RESUMEN
In malaria parasites, the erythrocyte binding-like proteins (EBL) are a family of invasion proteins that are attractive vaccine targets. In the case of Plasmodium vivax, the widespread malaria parasite, blood-stage vaccines have been largely focused on a single EBL candidate, the Duffy binding-like domain (DBL) of the Duffy binding protein (DBPII), due to its well-characterized role in the reticulocyte invasion. A novel P. vivax EBL family member, the Erythrocyte binding protein (EBP2, also named EBP or DBP2), binds preferentially to reticulocytes and may mediate an alternative P. vivax invasion pathway. To gain insight into the natural genetic diversity of the DBL domain of EBP2 (region II; EBP2-II), we analyzed ebp2-II gene sequences of 71 P. vivax isolates collected in different endemic settings of the Brazilian Amazon rainforest, where P. vivax is the predominant malaria-associated species. Although most of the substitutions in the ebp2-II gene were non-synonymous and suggested positive selection, the results showed that the DBL domain of the EBP2 was much less polymorphic than that of DBPII. The predominant EBP2 haplotype in the Amazon region corresponded to the C127 reference sequence first described in Cambodia (25% C127-like haplotype). An overview of ebp2-II gene sequences available at GenBank (n = 352) from seven countries (Cambodia, Madagascar, Myanmar, PNG, South Korea, Thailand, Vietnam) confirmed the C127-like haplotype as highly prevalent worldwide. Two out of 43 haplotypes (5 to 20 inferred per country) showed a global frequency of 60%. The results presented here open new avenues of research pursuit while suggesting that a vaccine based on the DBL domain of EBP2 should target a few haplotypes for broad coverage.
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Variación Genética , Malaria Vivax , Plasmodium vivax , Proteínas Protozoarias , Plasmodium vivax/genética , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Proteínas Protozoarias/química , Malaria Vivax/parasitología , Humanos , Bosque Lluvioso , Filogenia , Haplotipos , Antígenos de Protozoos/genética , Dominios Proteicos , Receptores de Superficie CelularRESUMEN
BACKGROUND: The simultaneous infection of Plasmodium falciparum and Epstein-Barr virus (EBV) could promote the development of the aggressive endemic Burkitt's Lymphoma (eBL) in children living in P. falciparum holoendemic areas. While it is well-established that eBL is not related to other human malaria parasites, the impact of EBV infection on the generation of human malaria immunity remains largely unexplored. Considering that this highly prevalent herpesvirus establishes a lifelong persistent infection on B-cells with possible influence on malaria immunity, we hypothesized that EBV co-infection could have impact on the naturally acquired antibody responses to P. vivax, the most widespread human malaria parasite. METHODOLOGY/PRINCIPAL FINDINGS: The study design involved three cross-sectional surveys at six-month intervals (baseline, 6 and 12 months) among long-term P. vivax exposed individuals living in the Amazon rainforest. The approach focused on a group of malaria-exposed individuals whose EBV-DNA (amplification of balf-5 gene) was persistently detected in the peripheral blood (PersVDNA, n = 27), and an age-matched malaria-exposed group whose EBV-DNA could never be detected during the follow-up (NegVDNA, n = 29). During the follow-up period, the serological detection of EBV antibodies to lytic/ latent viral antigens showed that IgG antibodies to viral capsid antigen (VCA-p18) were significantly different between groups (PersVDNA > NegVDNA). A panel of blood-stage P. vivax antigens covering a wide range of immunogenicity confirmed that in general PersVDNA group showed low levels of antibodies as compared with NegVDNA. Interestingly, more significant differences were observed to a novel DBPII immunogen, named DEKnull-2, which has been associated with long-term neutralizing antibody response. Differences between groups were less pronounced with blood-stage antigens (such as MSP1-19) whose levels can fluctuate according to malaria transmission. CONCLUSIONS/SIGNIFICANCE: In a proof-of-concept study we provide evidence that a persistent detection of EBV-DNA in peripheral blood of adults in a P. vivax semi-immune population may impact the long-term immune response to major malaria vaccine candidates.
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Linfoma de Burkitt , Coinfección , Infecciones por Virus de Epstein-Barr , Malaria Falciparum , Malaria Vivax , Malaria , Adulto , Anticuerpos Antiprotozoarios , Formación de Anticuerpos , Antígenos Virales , Linfoma de Burkitt/complicaciones , Linfoma de Burkitt/parasitología , Niño , Coinfección/complicaciones , Estudios Transversales , Infecciones por Virus de Epstein-Barr/complicaciones , Herpesvirus Humano 4/genética , Humanos , Malaria/complicaciones , Malaria Falciparum/parasitología , Plasmodium vivaxRESUMEN
Severe thrombocytopenia can be a determinant factor in the morbidity of Plasmodium vivax, the most widespread human malaria parasite. Although immune mechanisms may drive P. vivax-induced severe thrombocytopenia (PvST), the current data on the cytokine landscape in PvST is scarce and often conflicting. Here, we hypothesized that the analysis of the bidirectional circuit of inflammatory mediators and their regulatory miRNAs would lead to a better understanding of the mechanisms underlying PvST. For that, we combined Luminex proteomics, NanoString miRNA quantification, and machine learning to evaluate an extensive array of plasma mediators in uncomplicated P. vivax patients with different degrees of thrombocytopenia. Unsupervised clustering analysis identified a set of PvST-linked inflammatory (CXCL10, CCL4, and IL-18) and regulatory (IL-10, IL-1Ra, HGF) mediators. Among the mediators associated with PvST, IL-6 and IL-8 were critical to discriminate P. vivax subgroups, while CCL2 and IFN-γ from healthy controls. Supervised machine learning spotlighted IL-10 in P. vivax-mediated thrombocytopenia and provided evidence for a potential signaling route involving IL-8 and HGF. Finally, we identified a set of miRNAs capable of modulating these signaling pathways. In conclusion, the results place IL-10 and IL-8/HGF in the center of PvST and propose investigating these signaling pathways across the spectrum of malaria infections.
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Malaria Vivax , MicroARNs , Trombocitopenia , Humanos , Mediadores de Inflamación , Plasmodium vivaxRESUMEN
BACKGROUND: A low proportion of P. vivax-exposed individuals acquire protective strain-transcending neutralizing IgG antibodies that are able to block the interaction between the Duffy binding protein II (DBPII) and its erythrocyte-specific invasion receptor. In a recent study, a novel surface-engineered DBPII-based vaccine termed DEKnull-2, whose antibody response target conserved DBPII epitopes, was able to induce broadly binding-inhibitory IgG antibodies (BIAbs) that inhibit P. vivax reticulocyte invasion. Toward the development of DEKnull-2 as an effective P. vivax blood-stage vaccine, we investigate the relationship between naturally acquired DBPII-specific IgM response and the profile of IgG antibodies/BIAbs activity over time. METHODOLOGY/PRINCIPAL FINDINGS: A nine-year follow-up study was carried-out among long-term P. vivax-exposed Amazonian individuals and included six cross-sectional surveys at periods of high and low malaria transmission. DBPII immune responses associated with either strain-specific (Sal1, natural DBPII variant circulating in the study area) or conserved epitopes (DEKnull-2) were monitored by conventional serology (ELISA-detected IgM and IgG antibodies), with IgG BIAbs activity evaluated by functional assays (in vitro inhibition of DBPII-erythrocyte binding). The results showed a tendency of IgM antibodies toward Sal1-specific response; the profile of Sal1 over DEKnull-2 was not associated with acute malaria and sustained throughout the observation period. The low malaria incidence in two consecutive years allowed us to demonstrate that variant-specific IgG (but not IgM) antibodies waned over time, which resulted in IgG skewed to the DEKnull-2 response. A persistent DBPII-specific IgM response was not associated with the presence (or absence) of broadly neutralizing IgG antibody response. CONCLUSIONS/SIGNIFICANCE: The current study demonstrates that long-term exposure to low and unstable levels of P. vivax transmission led to a sustained DBPII-specific IgM response against variant-specific epitopes, while sustained IgG responses are skewed to conserved epitopes. Further studies should investigate on the role of a stable and persistent IgM antibody response in the immune response mediated by DBPII.
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Antígenos de Protozoos/inmunología , Inmunoglobulina G/inmunología , Inmunoglobulina M/inmunología , Vacunas contra la Malaria/uso terapéutico , Malaria Vivax/prevención & control , Plasmodium vivax/inmunología , Proteínas Protozoarias/inmunología , Receptores de Superficie Celular/inmunología , Adulto , Anticuerpos Neutralizantes/inmunología , Formación de Anticuerpos , Femenino , Humanos , Vacunas contra la Malaria/inmunología , Malaria Vivax/inmunología , Masculino , Persona de Mediana EdadRESUMEN
Abstract Objective: To determine decision limits for total cholesterol, LDL-cholesterol, non-HDL cholesterol, HDL-cholesterol, and triglycerides in healthy children and adolescents from Cuiabá, Brazil. Methods: This was a cross-sectional study of 1866 healthy children and adolescents randomly selected from daycare centers and public schools in Cuiabá. The desirable levels of serum lipids were defined using the classic criteria, i.e., total cholesterol, LDL-cholesterol, non-HDL cholesterol, and triglycerides levels below the P75 percentile, and HDL-c above the P10 percentile. Results: For CT, P75 was: 160 mg/dL for the age range of 1 to <3 years, 170 mg/dL for ≥3 to <9 years, and 176 mg/dL for ≥9 to <13 years. For non-HDL cholesterol, it was 122 mg/dL for the age range of 1 to <13 years. For LDL-c, it was 104 mg/dL at the age range of 1 to <9 years and 106 mg/dL from ≥9 to <13 years. For TG, it was 127 mg/dL from 1 to <2 years; 98 mg/dL from ≥2 to <6 years; and 92 mg/dL from ≥6 to <13 years. As for HDL-cholesterol, P10 was 24 mg/dL, 28 mg/dL, 32 mg/dL, and 36 mg/dL, for the age ranges of 1 to <2 years, ≥2 to <3 years, ≥3 to <4 years, and ≥4 to <13 years, respectively. Conclusion: The decision limits for the serum lipid levels defined in this study differed from those observed in the current Brazilian and North-American guidelines, especially because it differentiates between the age ranges. Using these decision limits in clinical practice will certainly contribute to improve the diagnostic accuracy for dyslipidemia in this population group.
Resumo Objetivo: Determinar limites de decisão (LD) para o colesterol total (CT), LDL-colesterol (LDL-c), colesterol não-HDL (c-NHDL), HDL-colesterol (HDL-c) e triglicérides (TG) em crianças e adolescentes saudáveis de Cuiabá. Método: Estudo transversal envolvendo 1.866 crianças e adolescentes saudáveis de creches e escolas municipais públicas de Cuiabá, aleatoriamente selecionadas. Os LD desejáveis dos lipídeos séricos foram definidos pelos critérios clássicos, isto é, níveis de CT, LDL-c, c-NHDL, TG abaixo do percentil 75, e de HDL-c acima do percentil 10. Resultados: Os P75 para CT foram: 160 mg/dL para a faixa etária de 1 a < 3 anos, 170 mg/dL para ≥ 3 a < 9 anos e 176 mg/dL para ≥ 9 a < 13 anos. Para o c-NHDL, de 122 mg/dL na faixa etária de 1 a < 13 anos. LDL-c: 104 mg/dL na faixa etária de 1 a < 9 anos e 106 mg/dL de ≥ 9 a < 13 anos. TG: 127 mg/dL entre 1 a < 2 anos; 98 mg/dL de ≥ 2 a < 6 anos; e 92 mg/dL de ≥ 6 a < 13 anos. Quanto ao HDL-c, o P10, foi de 24 mg/dL, 28 mg/dL, 32 mg/dL e 36 mg/dL, para as faixas etárias de 1 a < 2 anos, ≥ 2 a < 3 anos, ≥ 3 a < 4 anos e ≥ 4 a < 13 anos, respectivamente. Conclusão: Os LD dos níveis séricos de lipídeos definidos neste estudo diferem daqueles apresentados nas diretrizes brasileiras e americanas atuais, especialmente por fazer a diferenciação entre as idades. Utilizar tais LD em nossa prática clínica certamente contribuirá para melhorar a acurácia do diagnóstico de dislipidemia nesse grupo populacional.
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Humanos , Masculino , Femenino , Lactante , Preescolar , Niño , Estado Nutricional , Lípidos/sangre , Valores de Referencia , Triglicéridos/sangre , Brasil , Colesterol/sangre , Estudios Transversales , HDL-Colesterol/sangre , LDL-Colesterol/sangreRESUMEN
OBJECTIVE: To determine decision limits for total cholesterol, LDL-cholesterol, non-HDL cholesterol, HDL-cholesterol, and triglycerides in healthy children and adolescents from Cuiabá, Brazil. METHODS: This was a cross-sectional study of 1866 healthy children and adolescents randomly selected from daycare centers and public schools in Cuiabá. The desirable levels of serum lipids were defined using the classic criteria, i.e., total cholesterol, LDL-cholesterol, non-HDL cholesterol, and triglycerides levels below the P75 percentile, and HDL-c above the P10 percentile. RESULTS: For CT, P75 was: 160mg/dL for the age range of 1 to <3 years, 170mg/dL for ≥3 to <9 years, and 176mg/dL for ≥9 to <13 years. For non-HDL cholesterol, it was 122mg/dL for the age range of 1 to <13 years. For LDL-c, it was 104mg/dL at the age range of 1 to <9 years and 106mg/dL from ≥9 to <13 years. For TG, it was 127mg/dL from 1 to <2 years; 98mg/dL from ≥2 to <6 years; and 92mg/dL from ≥6 to <13 years. As for HDL-cholesterol, P10 was 24mg/dL, 28mg/dL, 32mg/dL, and 36mg/dL, for the age ranges of 1 to <2 years, ≥2 to <3 years, ≥3 to <4 years, and ≥4 to <13 years, respectively. CONCLUSION: The decision limits for the serum lipid levels defined in this study differed from those observed in the current Brazilian and North-American guidelines, especially because it differentiates between the age ranges. Using these decision limits in clinical practice will certainly contribute to improve the diagnostic accuracy for dyslipidemia in this population group.
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Lípidos/sangre , Estado Nutricional , Brasil , Niño , Preescolar , Colesterol/sangre , HDL-Colesterol/sangre , LDL-Colesterol/sangre , Estudios Transversales , Femenino , Humanos , Lactante , Masculino , Valores de Referencia , Triglicéridos/sangreRESUMEN
Plasmodium vivax remains a global health problem and its ability to cause relapses and subpatent infections challenge control and elimination strategies. Even in low malaria transmission settings, such as the Amazon basin, where progress in malaria control has caused a remarkable reduction in case incidence, a recent increase in P. vivax transmission demonstrates the continued vulnerability of P.vivax-exposed populations. As part of a search for complementary approaches to P.vivax surveillance in areas in which adults are the majority of the exposed-population, here we evaluated the potential of serological markers covering a wide range of immunogenicity to estimate malaria transmission trends. For this, antibodies against leading P. vivax blood-stage vaccine candidates were assessed during a 9 year follow-up study among adults exposed to unstable malaria transmission in the Amazon rainforest. Circulating antibody levels against immunogenic P. vivax proteins, such as the Apical Membrane Antigen-1, were a sensitive measure of recent P. vivax exposure, while antibodies against less immunogenic proteins were indicative of naturally-acquired immunity, including the novel engineered Duffy binding protein II immunogen (DEKnull-2). Our results suggest that the robustness of serology to estimate trends in P.vivax malaria transmission will depend on the immunological background of the study population, and that for adult populations exposed to unstable P.vivax malaria transmission, the local heterogeneity of antibody responses should be considered when considering use of serological surveillance.
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Anticuerpos Antiprotozoarios/sangre , Malaria Vivax/inmunología , Malaria Vivax/transmisión , Plasmodium vivax/inmunología , Adulto , Biomarcadores/sangre , Brasil , Estudios de Cohortes , Estudios Transversales , Femenino , Estudios de Seguimiento , Humanos , Malaria Vivax/sangre , Masculino , Persona de Mediana Edad , Bosque Lluvioso , Factores de TiempoRESUMEN
BACKGROUND: The human malaria parasite Plasmodium vivax infects red blood cells through a key pathway that requires interaction between Duffy binding protein II (DBPII) and its receptor on reticulocytes, the Duffy antigen/receptor for chemokines (DARC). A high proportion of P. vivax-exposed individuals fail to develop antibodies that inhibit DBPII-DARC interaction, and genetic factors that modulate this humoral immune response are poorly characterized. Here, we investigate if DBPII responsiveness could be HLA class II-linked. METHODOLOGY/PRINCIPAL FINDINGS: A community-based open cohort study was carried out in an agricultural settlement of the Brazilian Amazon, in which 336 unrelated volunteers were genotyped for HLA class II (DRB1, DQA1 and DQB1 loci), and their DBPII immune responses were monitored over time (baseline, 6 and 12 months) by conventional serology (DBPII IgG ELISA-detected) and functional assays (inhibition of DBPII-erythrocyte binding). The results demonstrated an increased susceptibility of the DRB1*13:01 carriers to develop and sustain an anti-DBPII IgG response, while individuals with the haplotype DRB1*14:02-DQA1*05:03-DQB1*03:01 were persistent non-responders. HLA class II gene polymorphisms also influenced the functional properties of DBPII antibodies (BIAbs, binding inhibitory antibodies), with three alleles (DRB1*07:01, DQA1*02:01 and DQB1*02:02) comprising a single haplotype linked with the presence and persistence of the BIAbs response. Modelling the structural effects of the HLA-DRB1 variants revealed a number of differences in the peptide-binding groove, which is likely to lead to altered antigen binding and presentation profiles, and hence may explain the differences in subject responses. CONCLUSIONS/SIGNIFICANCE: The current study confirms the heritability of the DBPII antibody response, with genetic variation in HLA class II genes influencing both the development and persistence of IgG antibody responses. Cellular studies to increase knowledge of the binding affinities of DBPII peptides for class II molecules linked with good or poor antibody responses might lead to the development of strategies for controlling the type of helper T cells activated in response to DBPII.
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Anticuerpos Antiprotozoarios/inmunología , Antígenos de Protozoos/inmunología , Cadenas HLA-DRB1/inmunología , Malaria Vivax/genética , Malaria Vivax/inmunología , Plasmodium vivax/inmunología , Proteínas Protozoarias/inmunología , Receptores de Superficie Celular/inmunología , Adulto , Alelos , Anticuerpos Antiprotozoarios/sangre , Anticuerpos Antiprotozoarios/metabolismo , Brasil/epidemiología , Proteínas Portadoras/genética , Estudios de Cohortes , Sistema del Grupo Sanguíneo Duffy/inmunología , Ensayo de Inmunoadsorción Enzimática , Eritrocitos/parasitología , Femenino , Variación Genética , Genotipo , Cadenas HLA-DRB1/genética , Haplotipos , Humanos , Inmunoglobulina G/inmunología , Malaria Vivax/epidemiología , Malaria Vivax/parasitología , Masculino , Persona de Mediana Edad , Plasmodium vivax/química , Plasmodium vivax/genética , Polimorfismo GenéticoRESUMEN
Background. Leprosy reactions are acute inflammatory episodes that occur mainly in the multibacillary forms of the disease. The reactions are classified as type 1 (reverse reaction) or type 2 (erythema nodosum leprosum). Leprosy-associated oxidative stress has been widely demonstrated. Several recent studies have shown uric acid (UA) to have antioxidative effects under pathologic conditions. The objective of this study was to assess serum levels of UA in patients with leprosy reactions, with the aim of monitoring their levels before and after treatment, compared with levels in leprosy patients without reactions. Methods. The study included patients aged 18-69 years assisted at a leprosy treatment reference center in the Central Region of Brazil. Patients who were pregnant; were using immunosuppressant drugs or immunobiologicals; or had an autoimmune disease, human immunodeficiency virus infection, acquired immune deficiency syndrome, or tuberculosis were excluded. Upon recruitment, all individuals were clinically assessed for skin lesions and neural or systemic impairment. Some patients had already completed treatment for leprosy, while others were still undergoing treatment or had initiated treatment after being admitted. The treatment of the reactional episode was started only after the initial evaluation. Laboratory assessments were performed upon admission (baseline) and at approximately 30 and 60 days (time points 1 and 2, respectively). Results. A total of 123 leprosy patients were recruited between June 2012 and June 2015; among them, 56, 42, and 25 presented with type 1, type 2, and no reactions, respectively. Serum UA levels were significantly reduced in patients with type 2 leprosy reactions compared with patients in the control group and remained lower in the two subsequent assessments, after initiation of anti-reaction treatments, with similar values to those recorded before the treatment. Discussion. The decreased serum UA levels in patients with type 2 leprosy reactions might be due to the consumption of UA to neutralize the enhanced production of oxygen- and nitrogen-reactive species that occurs during type 2 reactions. The maintenance of the reduced levels in the follow-up assessments may indicate persistence of oxidative stress in the initial post-treatment stages, despite improved clinical conditions. The results of this study suggest that serum UA may play an antioxidative role during type 2 leprosy reactions.
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Recent reports showed that, in mice, symptomatic Plasmodium infection triggers NLRP3/NLRP12-dependent inflammasome formation and caspase-1 activation in monocytes. In humans, few works demonstrated that inflammasome is activated in malaria. As Plasmodiumvivax is a potent inducer of inflammatory response we hypothesised that inflammasome genetics might affect P. vivax malaria clinical presentation. For this purpose, selected SNPs in inflammasome genes were analysed among patients with symptomatic P. vivax malaria. 157 Brazilian Amazon patients with P. vivax malaria were genotyped for 10 single nucleotide polymorphisms (SNPs) in inflammasome genes NLRP1, NLRP3, AIM2, CARD8, IL1B, IL18 and MEFV. Effect of SNPs on hematologic and clinical parameters was analysed by multivariate analysis. Our data suggested an important role of NLRP1 inflammasome receptor in shaping the clinical presentation of P. vivax malaria, in term of presence of fever, anaemia and thrombocytopenia. Moreover IL1B rs1143634 resulted significantly associated to patients' parasitaemia, while IL18 rs5744256 plays a protective role against the development of anaemia. Polymorphisms in inflammasome genes could affect one or other aspects of malaria pathogenesis. Moreover, these data reveal novel aspects of P.vivax/host interaction that involved NLRP1-inflammasome.
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Predisposición Genética a la Enfermedad , Inflamasomas/genética , Malaria Vivax/genética , Malaria Vivax/parasitología , Plasmodium vivax , Proteínas Adaptadoras Transductoras de Señales/genética , Adulto , Anciano , Anciano de 80 o más Años , Alelos , Proteínas Reguladoras de la Apoptosis/genética , Femenino , Frecuencia de los Genes , Genotipo , Humanos , Inflamasomas/metabolismo , Interleucina-18/genética , Interleucina-1beta/genética , Desequilibrio de Ligamiento , Malaria Vivax/diagnóstico , Malaria Vivax/metabolismo , Masculino , Persona de Mediana Edad , Proteínas NLR , Fenotipo , Polimorfismo de Nucleótido Simple , Selección GenéticaRESUMEN
BACKGROUND: Plasmodium vivax infections commonly contain multiple genetically distinct parasite clones. The detection of multiple-clone infections depends on several factors, such as the accuracy of the genotyping method, and the type and number of the molecular markers analysed. Characterizing the multiplicity of infection has broad implications that range from population genetic studies of the parasite to malaria treatment and control. This study compared and evaluated the efficiency of neutral and non-neutral markers that are widely used in studies of molecular epidemiology to detect the multiplicity of P. vivax infection. METHODS: The performance of six markers was evaluated using 11 mixtures of DNA with well-defined proportions of two different parasite genotypes for each marker. These mixtures were generated by mixing cloned PCR products or patient-derived genomic DNA. In addition, 51 samples of natural infections from the Brazil were genotyped for all markers. The PCR-capillary electrophoresis-based method was used to permit direct comparisons among the markers. The criteria for differentiating minor peaks from artifacts were also evaluated. RESULTS: The analysis of DNA mixtures showed that the tandem repeat MN21 and the polymorphic blocks 2 (msp1B2) and 10 (msp1B10) of merozoite surface protein-1 allowed for the estimation of the expected ratio of both alleles in the majority of preparations. Nevertheless, msp1B2 was not able to detect the majority of multiple-clone infections in field samples; it identified only 6 % of these infections. The merozoite surface protein-3 alpha and microsatellites (PvMS6 and PvMS7) did not accurately estimate the relative clonal proportions in artificial mixtures, but the microsatellites performed well in detecting natural multiple-clone infections. Notably, the use of a less stringent criterion to score rare alleles significantly increased the sensitivity of the detection of multi-clonal infections. CONCLUSIONS: Depending on the type of marker used, a considerable amplification bias was observed, which may have serious implications for the characterization of the complexity of a P. vivax infection. Based on the performance of markers in artificial mixtures of DNA and natural infections, a minimum panel of four genetic markers (PvMS6, PvMS7, MN21, and msp1B10) was defined, and these markers are highly informative regarding the genetic variability of P. vivax populations.
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Marcadores Genéticos/genética , Malaria Vivax/parasitología , Epidemiología Molecular/normas , Plasmodium vivax/genética , Brasil/epidemiología , ADN Protozoario/genética , Electroforesis Capilar , Técnicas de Genotipaje , Humanos , Malaria Vivax/epidemiología , Epidemiología Molecular/métodos , Reacción en Cadena de la PolimerasaRESUMEN
BACKGROUND: Demographic, geographic, environmental and genetic factors influence lipids. In many countries, the normal lipid ranges for laboratory tests are based on references from American children and adolescents. In this work, we determined the reference intervals (RIs) for total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c), non-high-density lipoprotein cholesterol (nHDL-c), low-density lipoprotein cholesterol (LDL-c) and triglycerides (TG) in Brazilian healthy children and adolescents. METHODS: A cross-sectional study was conducted of 1,866 randomly sampled healthy children and adolescents from kindergartens and schools. Blood samples were collected after a variable period of fasting based on the age of the participant. The upper cut-off points were the 75(th) and 95(th) percentiles for TC, nHDL-c, LDL-c and TG. The 10(th) percentile (low) was used as the bottom level for HDL-c. Non-parametric tests were used for statistical analyses. RESULTS: The following RI and 75(th) and 95(th) percentiles were observed for each age interval. The 95(th) percentile values obtained for TC were: 1 to 2 years, 189 mg/dL, 3 to 8 years, 199 mg/dL; 9 to 12 years, 205 mg/dL. For the nHDL c, the only age group 1 to 12 years, this percentile value was 150 mg/dL. For the LDL-cholesterol, the values corresponding to the percentiles above, aged 1 to 8 years and 9 to 12 years, were 132 mg/dL 139 mg/dL, respectively. For the triglycerides, the values corresponding to 95(th) percentile were: 1 year, 189 mg/dL; 2 to 5 years, 139 mg/dL; 6 to 12 years, 139 mg/dL . The 10(th) percentiles for HDL-c were 24 mg/dL, 28 mg/dL, 32 mg/dL and 36 mg/dL for children 1, 2, 3 and 4-12 years old, respectively. CONCLUSIONS: The lipid reference intervals defined in the studied Brazilian children and adolescents differ from those recommended by the international literature and should be used for clinical decisions contributing to improve the diagnosis in this particular group in our country.
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HDL-Colesterol/sangre , LDL-Colesterol/sangre , Colesterol/sangre , Triglicéridos/sangre , Brasil , Niño , Preescolar , Estudios Transversales , Demografía , Ambiente , Etnicidad , Ayuno , Femenino , Humanos , Lactante , Lípidos/sangre , Masculino , Valores de Referencia , Historia Reproductiva , Instituciones Académicas , TrabajoRESUMEN
In this paper, we introduce a new model for recurrent event data characterized by a baseline rate function fully parametric, which is based on the exponential-Poisson distribution. The model arises from a latent competing risk scenario, in the sense that there is no information about which cause was responsible for the event occurrence. Then, the time of each recurrence is given by the minimum lifetime value among all latent causes. The new model has a particular case, which is the classical homogeneous Poisson process. The properties of the proposed model are discussed, including its hazard rate function, survival function, and ordinary moments. The inferential procedure is based on the maximum likelihood approach. We consider an important issue of model selection between the proposed model and its particular case by the likelihood ratio test and score test. Goodness of fit of the recurrent event models is assessed using Cox-Snell residuals. A simulation study evaluates the performance of the estimation procedure in the presence of a small and moderate sample sizes. Applications on two real data sets are provided to illustrate the proposed methodology. One of them, first analyzed by our team of researchers, considers the data concerning the recurrence of malaria, which is an infectious disease caused by a protozoan parasite that infects red blood cells.
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Biometría/métodos , Malaria/epidemiología , Modelos Estadísticos , Brasil/epidemiología , Humanos , Funciones de Verosimilitud , Distribución de Poisson , Probabilidad , RecurrenciaRESUMEN
The Plasmodium vivax Duffy binding protein (PvDBP) and its erythrocytic receptor, the Duffy antigen receptor for chemokines (DARC), are involved in the major P. vivax erythrocyte invasion pathway. An open cohort study to analyze DARC genotypes and their relationship to PvDBP immune responses was carried out in 620 volunteers in an agricultural settlement of the Brazilian Amazon. Three cross-sectional surveys were conducted at 6-month intervals, comprising 395, 410, and 407 subjects, respectively. The incidence rates of P. vivax infection was 2.32 malaria episodes per 100 person-months under survey (95% confidence interval [CI] of 1.92-2.80/100 person-month) and, of P. falciparum, 0.04 per 100 person-months (95% CI of 0.007-0.14/100 person-month). The distribution of DARC genotypes was consistent with the heterogeneous ethnic origins of the Amazon population, with a predominance of non-silent DARC alleles: FY*A > FY*B. The 12-month follow-up study demonstrated no association between DARC genotypes and total IgG antibodies as measured by ELISA targeting PvDBP (region II, DBPII or regions II-IV, DBPII-IV). The naturally acquired DBPII specific binding inhibitory antibodies (BIAbs) tended to be more frequent in heterozygous individuals carrying a DARC-silent allele (FY*BES). These results provide evidence that DARC polymorphisms may influence the naturally acquired inhibitory anti-Duffy binding protein II immunity.
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Antígenos de Protozoos/inmunología , Sistema del Grupo Sanguíneo Duffy/genética , Malaria Vivax/inmunología , Polimorfismo Genético , Proteínas Protozoarias/inmunología , Receptores de Superficie Celular/genética , Receptores de Superficie Celular/inmunología , Adolescente , Adulto , Alelos , Estudios Transversales , Estudios de Seguimiento , Frecuencia de los Genes , Genotipo , Humanos , Malaria Vivax/genética , Masculino , Persona de Mediana Edad , Adulto JovenRESUMEN
BACKGROUND: This study described altered platelet indices in patients with acute malaria caused by Plasmodium vivax and determined whether these alterations are associated with warning signs of severe and complicated malaria. METHODS: A total of 186 patients attending the Malaria Clinic at the University Hospital from the Federal University of Mato Grosso, Brazil, between 2008 and 2013 were included in this study. After parasitological confirmation of exclusive infection by P. vivax, blood cell counts and platelet indices were determined. Disease gravity was evaluated on the basis of classic signs of Plasmodium falciparum severe malaria, including severe anemia, or by changes in serum levels of glucose, bilirubin, aminotransferases and creatinine at the time of the patient's admission. Patients with a longer duration of symptoms or those identified as primo infected were considered potential candidates for evolution into the severe form of malaria. RESULTS: The mean platelet volume (MPV), platelet distribution width (PDW), and plateletcrit (PCT) values exhibited significant variability. A significant inverse relationship was observed between parasitaemia and PCT. Patients with warning signs for evolution into severe disease, with primo infection, or presenting with symptoms for over three days had the highest MPV and PDW. The adjusted analyses showed the presence of warning signs for the development of severe and complicated malaria remained independently linked to elevated MPV and PDW. CONCLUSION: Altered platelet indices should be analysed as potential markers for the severity of malaria caused by P. vivax. Future studies with appropriate methodology for prognostic evaluation could confirm the potential use of these indices in clinical practice.
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Biomarcadores/análisis , Plaquetas/citología , Malaria Vivax/diagnóstico , Malaria Vivax/patología , Índice de Severidad de la Enfermedad , Adulto , Brasil , Estudios Transversales , Femenino , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , Adulto JovenRESUMEN
BACKGROUND: Malaria is the most prevalent parasitic disease in the world. In Brazil, the largest number of malaria cases (98%) is within the Legal Amazon region, where Plasmodium vivax is responsible for over 80% of diagnosed cases. The aim of this study was to investigate the annexin-A1 expression in CD4+, CD8+ T cells, regulatory T cells (Treg) and cytokine IL-10 quantification in plasma from patients with malaria caused by P. vivax. METHODS: The quantification of the cytokine IL-10 of patients infected with P. vivax and healthy controls were evaluated by enzyme-linked immunosorbent assay (ELISA). The determination of the expression of annexin-A1 in lymphocytes from patients and healthy controls was determined by immunofluorescence staining. All results were correlated with the parasitaemia and the number of previous episodes of malaria. RESULTS: The cytokine IL-10 plasma levels showed a significant increase in both patients with low (650.4 ± 59.3 pg/mL) and high (2870 ± 185.3 pg/mL) parasitaemia compared to the control (326.1 ± 40.1 pg/mL). In addition, there was an increase of this cytokine in an episode dependent manner (individuals with no previous episodes of malaria--primoinfected: 363.9 ± 31.1 pg/mL; individuals with prior exposure: 659.9 ± 49.4 pg/mL). The quantification of annexin-A1 expression indicated a decrease in CD4+ and CD8+ T cells and an increase in Treg in comparison with the control group. When annexin-A1 expression was compared according to the number of previous episodes of malaria, patients who have been exposed more than once to the parasite was found to have higher levels of CD4+ T cells (96.0 ± 2.5 A.U) compared to primoinfected (50.3 ± 1.7). However, this endogenous protein had higher levels in CD8+ (108.5 ± 3.1) and Treg (87.5 ± 2.5) from patients primoinfected. CONCLUSION: This study demonstrates that in the patients infected with P. vivax the release of immunoregulatory molecules can be influenced by the parasitaemia level and the number of previous episodes of malaria. annexin-A1 is expressed differently in lymphocyte sub-populations and may have a role in cell proliferation. Furthermore, annexin-A1 may be contributing to IL-10 release in plasma of patients with vivax malaria.
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Anexina A1/biosíntesis , Interleucina-10/sangre , Malaria Vivax/inmunología , Plasmodium vivax/inmunología , Subgrupos de Linfocitos T/inmunología , Adulto , Brasil , Ensayo de Inmunoadsorción Enzimática , Femenino , Técnica del Anticuerpo Fluorescente , Voluntarios Sanos , Humanos , MasculinoRESUMEN
INTRODUCTION: In remote areas of the Amazon Region, diagnosis of malaria by microscopy is practically impossible. This study aimed to evaluate the performance of two rapid diagnostic tests (RDTs) targeting different malaria antigens stored at room temperature in the Brazilian Amazon Region. METHODOLOGY: Performance of the OptiMal Pf/Pan test and ICT-Now Pf/Pan test was analyzed retrospectively in 1,627 and 1,602 blood samples, respectively. Tests were performed over a 15-month period. Kits were stored at room temperature in five community health centres located in the Brazilian Amazon Region. RDT results were compared with thick blood smear (TBS) results to determine sensitivity, specificity, and accuracy of the RDT. RESULTS: The sensitivities of the OptiMal Pf/Pan test were 79.7% for Plasmodium falciparum malaria diagnosis and 85.7% for non-P. falciparum infections. The results showed a crude agreement of 88.5% for P. falciparum, and 88.3% for non-P. falciparum infections (Kappa index = 0.74 and 0.75, respectively). For the ICT-Now Pf/Pan test (CI 95%), the sensitivities were 87.9% for P. falciparum malaria diagnosis and 72.5% for non-P. falciparum infection. Crude agreement between the ICT-Now Pf/Pan test and TBS was 91.4% for P. falciparum and 79.7% for non-P. falciparum infection. The Kappa index was 0.81 and 0.59 for the final diagnosis of P. falciparum and non-P. falciparum, respectively. Higher levels of parasitaemia were associated with higher crude agreement between RDT and TBS. CONCLUSIONS: The sensitivities of RDTs stored at room temperature over a 15-month period and performed in field conditions were lower than those previously reported.
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Antígenos de Protozoos/sangre , Pruebas Diagnósticas de Rutina/métodos , Malaria Falciparum/diagnóstico , Plasmodium falciparum/aislamiento & purificación , Manejo de Especímenes/métodos , Adolescente , Adulto , Anciano , Brasil , Niño , Preescolar , Femenino , Humanos , Inmunoensayo/métodos , Lactante , Masculino , Persona de Mediana Edad , Plasmodium falciparum/inmunología , Sensibilidad y Especificidad , Temperatura , Factores de Tiempo , Adulto JovenRESUMEN
Understanding the pathogenesis of Plasmodium vivax malaria is challenging. We hypothesized that susceptibility to P. vivax-induced thrombocytopenia could be associated with polymorphisms on relevant platelet membrane integrins: integrin α2 (C807T), and integrin ß3 (T1565C). Although ß3 polymorphism was not related with P. vivax malaria, α2 807T carriers, which show high levels of integrin α2ß1, had a higher probability for severe thrombocytopenia than wild-type carriers. This evidence of the association of integrin polymorphism and P. vivax morbidity was further demonstrated by a moderate but significant correlation between clinical disease and surface levels of the integrin α2ß1.
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Integrina alfa2beta1/genética , Malaria Vivax/genética , Plasmodium vivax/patogenicidad , Polimorfismo Genético , Trombocitopenia/parasitología , Adolescente , Adulto , Anciano , Niño , Preescolar , Femenino , Genotipo , Humanos , Integrina alfa2/genética , Integrina alfa2/metabolismo , Integrina alfa2beta1/metabolismo , Integrina beta3/genética , Integrina beta3/metabolismo , Malaria Vivax/parasitología , Masculino , Persona de Mediana Edad , Adulto JovenRESUMEN
BACKGROUND: Signal peptide is one of the most important motifs involved in protein trafficking and it ultimately influences protein function. Considering the expected functional conservation among orthologs it was hypothesized that divergence in signal peptides within orthologous groups is mainly due to N-terminal protein sequence misannotation. Thus, discrepancies in signal peptide prediction of orthologous proteins were used to identify misannotated proteins in five Plasmodium species. METHODS: Signal peptide (SignalP) and orthology (OrthoMCL) were combined in an innovative strategy to identify orthologous groups showing discrepancies in signal peptide prediction among their protein members (Mixed groups). In a comparative analysis, multiple alignments for each of these groups and gene models were visually inspected in search of misannotated proteins and, whenever possible, alternative gene models were proposed. Thresholds for signal peptide prediction parameters were also modified to reduce their impact as a possible source of discrepancy among orthologs. Validation of new gene models was based on RT-PCR (few examples) or on experimental evidence already published (ApiLoc). RESULTS: The rate of misannotated proteins was significantly higher in Mixed groups than in Positive or Negative groups, corroborating the proposed hypothesis. A total of 478 proteins were reannotated and change of signal peptide prediction from negative to positive was the most common. Reannotations triggered the conversion of almost 50% of all Mixed groups, which were further reduced by optimization of signal peptide prediction parameters. CONCLUSIONS: The methodological novelty proposed here combining orthology and signal peptide prediction proved to be an effective strategy for the identification of proteins showing wrongly N-terminal annotated sequences, and it might have an important impact in the available data for genome-wide searching of potential vaccine and drug targets and proteins involved in host/parasite interactions, as demonstrated for five Plasmodium species.
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Biología Computacional/métodos , Anotación de Secuencia Molecular/métodos , Plasmodium/genética , Señales de Clasificación de Proteína , Proteínas Protozoarias/genéticaRESUMEN
OBJECTIVE: To investigate risk factors associated with the acquisition of antibodies against Plasmodium vivax Duffy binding protein (PvDBP) - a leading malaria vaccine candidate - in a well-consolidated agricultural settlement of the Brazilian Amazon Region and to determine the sequence diversity of the PvDBP ligand domain (DBP(II)) within the local malaria parasite population. METHODS: Demographic, epidemiological and clinical data were collected from 541 volunteers using a structured questionnaire. Malaria parasites were detected by conventional microscopy and PCR, and blood collection was used for antibody assays and molecular characterisation of DBP(II). RESULTS: The frequency of malaria infection was 7% (6% for P. vivax and 1% for P. falciparum), with malaria cases clustered near mosquito breeding sites. Nearly 50% of settlers had anti-PvDBP IgG antibodies, as detected by enzyme-linked immunosorbent assay (ELISA) with subject's age being the only strong predictor of seropositivity to PvDBP. Unexpectedly, low levels of DBP(II) diversity were found within the local malaria parasites, suggesting the existence of low gene flow between P. vivax populations, probably due to the relative isolation of the studied settlement. CONCLUSION: The recognition of PvDBP by a significant proportion of the community, associated with low levels of DBP(II) diversity among local P. vivax, reinforces the variety of malaria transmission patterns in communities from frontier settlements. Such studies should provide baseline information for antimalarial vaccines now in development.