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Malaria is the leading parasitic disease worldwide, with P. vivax being a major challenge for its control. Several studies have indicated metabolomics as a promising tool for combating the disease. The study evaluated plasma metabolomic profiles of patients with recurrent and non-recurrent P. vivax malaria in the Brazilian Amazon. Metabolites extracted from the plasma of P. vivax-infected patients were subjected to LC-MS analysis. Untargeted metabolomics was applied to investigate the metabolic profile of the plasma in the two groups. Overall, 51 recurrent and 59 non-recurrent patients were included in the study. Longitudinal metabolomic analysis revealed 52 and 37 significant metabolite features from the recurrent and non-recurrent participants, respectively. Recurrence was associated with disturbances in eicosanoid metabolism. Comparison between groups suggest alterations in vitamin B6 (pyridoxine) metabolism, tyrosine metabolism, 3-oxo-10-octadecatrienoate ß-oxidation, and alkaloid biosynthesis II. Integrative network analysis revealed enrichment of other metabolic pathways for the recurrent phenotype, including the butanoate metabolism, aspartate and asparagine metabolism, and N-glycan biosynthesis. The metabolites and metabolic pathways predicted in our study suggest potential biomarkers of recurrence and provide insights into targets for antimalarial development against P. vivax.

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BACKGROUND: Malaria transmission modelling has demonstrated the potential impact of semiquantitative glucose-6-phosphate dehydrogenase (G6PD) testing and treatment with single-dose tafenoquine for Plasmodium vivax radical cure but has not investigated the associated costs. This study evaluated the cost-effectiveness of P. vivax treatment with tafenoquine after G6PD testing using a transmission model. METHODS AND FINDINGS: We explored the cost-effectiveness of using tafenoquine after G6PD screening as compared to usual practice (7-day low-dose primaquine (0.5 mg/kg/day) without G6PD screening) in Brazil using a 10-year time horizon with 5% discounting considering 4 scenarios: (1) tafenoquine for adults only assuming 66.7% primaquine treatment adherence; (2) tafenoquine for adults and children aged >2 years assuming 66.7% primaquine adherence; (3) tafenoquine for adults only assuming 90% primaquine adherence; and (4) tafenoquine for adults only assuming 30% primaquine adherence. The incremental cost-effectiveness ratios (ICERs) were estimated by dividing the incremental costs by the disability-adjusted life years (DALYs) averted. These were compared to a willingness to pay (WTP) threshold of US$7,800 for Brazil, and one-way and probabilistic sensitivity analyses were performed. All 4 scenarios were cost-effective in the base case analysis using this WTP threshold with ICERs ranging from US$154 to US$1,836. One-way sensitivity analyses showed that the results were most sensitive to severity and mortality due to vivax malaria, the lifetime and number of semiquantitative G6PD analysers needed, cost per malaria episode and per G6PD test strips, and life expectancy. All scenarios had a 100% likelihood of being cost-effective at the WTP threshold. The main limitations of this study are due to parameter uncertainty around our cost estimates for low transmission settings, the costs of G6PD screening, and the severity of vivax malaria. CONCLUSIONS: In our modelling study that incorporated impact on transmission, tafenoquine prescribed after a semiquantitative G6PD testing was highly likely to be cost-effective in Brazil. These results demonstrate the potential health and economic importance of ensuring safe and effective radical cure.

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IMPORTANCE: The SARS-CoV-2 virus infection in humans induces significant inflammatory and systemic reactions and complications of which corticosteroids like methylprednisolone have been recommended as treatment. Our understanding of the metabolic and metabolomic pathway dysregulations while using intravenous corticosteroids in COVID-19 is limited. This study will help enlighten the metabolic and metabolomic pathway dysregulations underlying high daily doses of intravenous methylprednisolone in COVID-19 patients compared to those receiving placebo. The information on key metabolites and pathways identified in this study together with the crosstalk with the inflammation and biochemistry components may be used, in the future, to leverage the use of methylprednisolone in any future pandemics from the coronavirus family.

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Background: Plasmodium vivax malaria is challenging to control and eliminate. Treatment with radical cure drugs fails to target the hidden asymptomatic and hypnozoite reservoirs in populations. PvSeroTAT, a novel serological test-and-treat intervention using a serological diagnostic to screen hypnozoite carriers for radical cure eligibility and treatment, could accelerate P. vivax elimination. Methods: Using a previously developed mathematical model of P. vivax transmission adapted to the Brazilian context as a case study for implementation, we evaluate the public health impact of various deployment strategies of PvSeroTAT as a mass campaign. We compare relative reductions in prevalence, cases averted, glucose-6-phosphate dehydrogenase (G6PD) tests, and treatment doses of PvSeroTAT campaigns to strengthened case management alone or mass drug administration (MDA) campaigns across different settings. Findings: Deploying a single round of PvSeroTAT with 80% coverage to treat cases with a high efficacy radical cure regimen with primaquine is predicted to reduce point population prevalence by 22.5% [95% UI: 20.2%-24.8%] in a peri-urban setting with high transmission and by 25.2% [95% UI: 9.6%-42.2%] in an occupational setting with moderate transmission. In the latter example, while a single PvSeroTAT achieves 9.2% less impact on prevalence and averts 300 less cases per 100,000 than a single MDA (25.2% [95% UI: 9.6%-42.2%] point prevalence reduction versus 34.4% [95% UI: 24.9%-44%]), PvSeroTAT requires 4.6 times less radical cure treatments and G6PD tests. Layering strengthened case management and deploying four rounds of PvSeroTAT six months apart is predicted to reduce point prevalence by a mean of 74.1% [95% UI: 61.3%-86.3%] or more in low transmission settings with less than 10 cases per 1000 population. Interpretation: Modelling predicts that mass campaigns with PvSeroTAT are predicted to reduce P. vivax parasite prevalence across a range of transmission settings and require fewer resources than MDA. In combination with strengthened case management, mass campaigns of serological test-and-treat interventions can accelerate towards P. vivax elimination. Funding: This project was funded in part by the Bill and Melinda Gates Foundation and the National Health and Medical Research Council.

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BACKGROUND: The groundwork for malaria elimination does not currently consider the potential of Plasmodium zoonotic cycles that involve non-human primates (NHPs) in sylvatic environments. Since vivax malaria is less responsive to control measures, finding Plasmodium vivax infected NHPs adds even more concern. METHODS: Both Free-living monkeys in forest fragments inside the urban area and captive monkeys from a local zoo had blood samples tested for Plasmodium species. RESULTS: In this study, among the Neotropical monkeys tested, three (4.4%), one captive and two free-living, were found to be naturally infected by P. vivax. CONCLUSION: This important finding indicates that it is necessary to estimate the extent to which P. vivax NHP infection contributes to the maintenance of malaria transmission to humans. Therefore, the discussion on wildlife conservation and management must be incorporated into the malaria elimination agenda.

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The exact path leading to cognitive impairment that goes beyond malaria is unclear, but it appears to be the result of interactive factors. Time of exposure to disease and recurrences are potentially major determinant variables. Cognitive impairment is described mainly in children, rarely in adults. The disease in high endemic areas usually does not affect elderlies, because of acquired immunity over time. However, this population is relatively more frequently sick in lower endemic areas, such as in the Amazon. This study assessed the effect of Plasmodium vivax malaria on the executive and cognitive functions of elderlies, in the Brazilian Amazon. A cohort study was conducted to evaluate executive and cognitive functions one week (T0), two months (T2) and eight months (T8) after the malaria episode. Mini-Mental State Examination (MMSE), Beck Depression Inventory II (BDI-II), Clock Drawing Test (CDT), Wechsler adult intelligence scale (WAIS-III), and Wisconsin Card Sorting Test (WCST) were used to assess executive and cognitive functions. One hundred-forty elderlies were enrolled (70 with P. vivax malaria and 70 without malaria). P. vivax malaria was associated with impairment of the executive and cognitive functions in elderlies for up to 8 months after acute P. vivax malaria. Prior history of malaria, recurrences and higher parasitemia were independently associated with various surrogates of executive and cognitive impairment. With the increase in life expectancy, elderlies living in malaria endemic areas will deserve more attention from health authorities, to guarantee improvement of their quality of life in the tropics.

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BACKGROUND: As quantitative glucose 6-phosphate dehydrogenase deficiency (G6PDd) screening tools are evaluated in operational studies, questions remain as to whether they are cost-effective. Here, a cost-effectiveness analysis (CEA) was performed to estimate the Incremental Cost-effectiveness Ratio (ICER) of the introduction of quantitative screening test to detect G6PDd among P. vivax carriers in two municipalities in the Brazilian Amazon. METHODOLOGY/PRINCIPAL FINDINGS: This cost-effectiveness analysis evaluated the use of the Standard G6PD quantitative screening test in vivax malaria treatment units in two municipalities of the Brazilian Amazon. Using the perspective of the Brazilian public health system, the analysis was performed for the outcome 'PQ-associated hospitalization avoided', based on a decision tree model. The results indicated that the G6PDd screening strategy compared with the routine strategy was highly cost-effective, with an ICER of US$495 per additional hospitalization avoided, which represented less than 8% of one Brazilian gross domestic product per capita (US$6,822). The uncertainties evaluated in the sensitivity analysis did not significantly affect the ICER identified in the base-case. CONCLUSIONS/SIGNIFICANCE: This cost-effectiveness analysis showed the quantitative G6PD testing was effective in avoiding PQ-associated hospitalizations. The incorporation of G6PD screening is of paramount importance towards P. vivax malaria elimination in the Amazon to promote the safe use of primaquine and tafenoquine.

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BACKGROUND: The presence of Plasmodium vivax malaria parasites in the human bone marrow (BM) is still controversial. However, recent data from a clinical case and experimental infections in splenectomized nonhuman primates unequivocally demonstrated the presence of parasites in this tissue. METHODS: In the current study, we analyzed BM aspirates of 7 patients during the acute attack and 42 days after drug treatment. RNA extracted from CD71+ cell suspensions was used for sequencing and transcriptomic analysis. RESULTS: We demonstrated the presence of parasites in all patients during acute infections. To provide further insights, we purified CD71+ BM cells and demonstrated dyserythropoiesis and inefficient erythropoiesis in all patients. In addition, RNA sequencing from 3 patients showed that genes related to erythroid maturation were down-regulated during acute infections, whereas immune response genes were up-regulated. CONCLUSIONS: This study thus shows that during P. vivax infections, parasites are always present in the BM and that such infections induced dyserythropoiesis and ineffective erythropoiesis. Moreover, infections induce transcriptional changes associated with such altered erythropoietic response, thus highlighting the importance of this hidden niche during natural infections.

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OBJECTIVES: To evaluate the incidence of COVID-19 and its main outcomes in rheumatic disease (RD) patients on hydroxychloroquine (HCQ) compared to household cohabitants (HC). METHODS: This is a 24-week nationwide prospective multi-centre cohort with a control group without RD and not using HCQ. All participants were monitored through scheduled phone interviews performed by health professionals. Details regarding COVID-19 symptoms, and epidemiological, clinical, and demographic data were recorded on a specific web-based platform. COVID-19 was defined according to the Brazilian Ministry of Health criteria and classified as mild, moderate or severe. RESULTS: A total of 9,585 participants, 5,164 (53.9%) RD patients on HCQ and 4,421 (46.1%) HC were enrolled from March 29th, 2020 to September 30th, 2020, according to the eligibility criteria. COVID-19 confirmed cases were higher in RD patients than in cohabitants [728 (14.1%) vs. 427 (9.7%), p<0.001] in a 24-week follow-up. However, there was no significant difference regarding outcomes related to moderate/ severe COVID-19 (7.1% and 7.3%, respectively, p=0.896). After multiple adjustments, risk factors associated with hospitalisation were age over 65 (HR=4.5; 95%CI 1.35-15.04, p=0.014) and cardiopathy (HR=2.57; 95%CI 1.12-5.91, p=0.026). The final survival analysis demonstrated the probability of dying in 180 days after a COVID-19 diagnosis was significantly higher in patients over 65 years (HR=20.8; 95%CI 4.5-96.1) and with 2 or more comorbidities (HR=10.8; 95%CI 1.1-107.9 and HR=24.8; 95%CI 2.5-249.3, p=0.006, respectively). CONCLUSIONS: Although RD patients have had a higher COVID-19 incidence than individuals from the same epidemiological background, the COVID-19 severity was related to traditional risk factors, particularly multiple comorbidities and age, and not to underlying RD and HCQ.

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Homeostatic perturbation caused by infection fosters two major defense strategies, resistance and tolerance, which promote the host's survival. Resistance relates to the ability of the host to restrict the pathogen load. Tolerance minimizes collateral tissue damage without directly affecting pathogen fitness. These concepts have been explored mechanistically in murine models of malaria but only superficially in human disease. Indeed, individuals infected with Plasmodium vivax may present with asymptomatic malaria, only mild symptoms, or be severely ill. We and others have reported a diverse repertoire of immunopathological events that potentially underly susceptibility to disease severity in vivax malaria. Nevertheless, the combined epidemiologic, clinical, parasitological, and immunologic features associated with defining the disease outcomes are still not fully understood. In the present study, we perform an extensive outlining of cytokines and inflammatory proteins in plasma samples from a cohort of individuals from the Brazilian Amazon infected with P. vivax and presenting with asymptomatic (n = 108) or symptomatic (n = 134) disease (106 with mild presentation and 28 with severe malaria), as well as from uninfected endemic controls (n = 128) to elucidate these gaps further. We employ highly multidimensional Systems Immunology analyses using the molecular degree of perturbation to reveal nuances of a unique profile of systemic inflammation and imbalanced immune activation directly linked to disease severity as well as with other clinical and epidemiologic characteristics. Additionally, our findings reveal that the main factor associated with severe cases of P. vivax infection was the number of symptoms, despite of a lower global inflammatory perturbation and parasitemia. In these participants, the number of symptoms directly correlated with perturbation of markers of inflammation and tissue damage. On the other hand, the main factor associated with non-severe infections was the parasitemia values, that correlated only with perturbation of inflammatory markers, such as IL-4 and IL-1ß, with a relatively lower number of symptoms. These observations suggest that some persons present severe vivax regardless of pathogen burden and global inflammatory perturbation. Such patients are thus little tolerant to P. vivax infection and show higher susceptibility to disrupt homeostasis and consequently exhibit more clinical manifestations. Other persons are capable to tolerate higher parasitemia with lower inflammatory perturbation and fewer symptoms, developing non-severe malaria. The analytical approach presented here has capability to define in more details the determinants of disease tolerance in vivax malaria.

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Anopheles aquasalis is an important malaria vector in coastal regions of South America and islands of the Caribbean. In its original description, the species was divided into two varieties, based on the scaling patterns of their hind-tarsomere 2. Specimens from our 25-year established colony, used for Plasmodium experimental infections, still exhibit both scaling tarsomere patterns. This study examined the DNA sequence of the nuclear Internal Transcribed Spacer 2 (ITS2) and susceptibility to Plasmodium, looking for differences among the phenotypes 30BS and 50BS. One hundred mosquitoes, 25 males and 25 females of each sex, and phenotype were analyzed. Twenty-seven novel haplotypes were identified. Three were found in both phenotypes (30BS and 50BS) regardless of gender. Among the other 27 genotypes, we observed a male-oriented bias in both phenotypic categories. Evaluation of Plasmodium yoelii N67 infections, based on oocyst counts, showed a higher susceptibility of 30BS compared with 50BS. Future studies need to be conducted to evaluate if these genotype assortments among the phenotypic groups reflect differences in fitness, mating, and their susceptibility to infection by Plasmodium parasites.

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BACKGROUND: The first potential focus for artemisinin resistance in South America was recently confirmed with the presence of the C580Y mutation in the Plasmodium falciparum kelch 13 gene (pfk13) in Guyana. OBJECTIVES: This study aimed to strengthen pfk13 monitoring in the Amazon basin countries, to compile the available data and to evaluate the risk of spreading of mutations. METHODS: Sanger sequencing was done on 862 samples collected between 1998 and 2019, and a global map of pfk13 genotypes available for this region was constructed. Then, the risk of spreading of mutations based on P. falciparum case importation between 2015 and 2018 within countries of the Amazon basin was evaluated. RESULTS: No additional pfk13 C580Y foci were identified. Few mutations (0.5%, 95% CI = 0.3%-0.8%) in the propeller domain were observed in the general parasite population of this region despite a high proportion of K189T mutations (49.1%, 95% CI = 46.2%-52.0%) in the non-propeller domain. Case information revealed two patterns of intense human migration: Venezuela, Guyana and the Roraima State in Brazil; and French Guiana, Suriname and the Amapá State in Brazil. CONCLUSIONS: There are few pfk13 mutant foci, but a high risk of dispersion in the Amazon basin, mainly from the Guiana Shield, proportionate to mining activities. Therefore, access to prompt diagnosis and treatment, and continuous molecular monitoring is essential in these geographical areas.

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BACKGROUND: Point-of-care glucose-6-phosphate dehydrogenase (G6PD) testing has the potential to make the use of radical treatment for vivax malaria safer and more effective. Widespread use of G6PD tests as part of malaria case management has been limited, in part due to due concerns regarding product usability, user training, and supervision. This study seeks to assess how well end users can understand the Standard™ G6PD Test (SD Biosensor, Suwon, South Korea) workflow, result output, and label after training. This will ultimately help inform test registration and introduction. METHODS: Potential G6PD test users who provide malaria case management at three sites in Brazil, Ethiopia, and India were trained on the use of the SD Biosensor Standard G6PD Test and assessed based on their ability to understand the test workflow and interpret results. The assessment was done through a questionnaire, designed to assess product usability against key technical product specifications and fulfill regulatory evidence requirements. Any participant who obtained 85% or above correct responses to the questionnaire was considered to adequately comprehend how to use and interpret the test. RESULTS: Forty-five participants, including malaria microscopists, laboratory staff, nurses, and community health workers took part in the study. Seventy-eight percent of all participants in the study (35/45) obtained passing scores on the assessment with minimal training. Responses to the multiple-choice questions indicate that most participants understood well the test intended use, safety claims, and warnings. The greatest source of error regarding the test was around the correct operating temperature. Most test results were also read and interpreted correctly, with the haemoglobin measurement being a more problematic output to interpret than the G6PD measurement. CONCLUSIONS: These data results show how a standardized tool can be used to assess a user's ability to run a point-of-care diagnostic and interpret results. When applied to the SD Biosensor Standard G6PD Test, this tool demonstrates that a range of users across multiple contexts can use the test and suggests improvements to the test instructions and training that can improve product usability, increase user comprehension, and ultimately contribute to more widespread effective use of point-of-care G6PD tests. TRIAL REGISTRATION: NCT04033640.

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In Brazil, malaria caused by Plasmodium vivax presents control challenges due to several reasons, among them the increasing possibility of failure of P. vivax treatment due to chloroquine-resistance (CQR). Despite limited reports of CQR, more extensive studies on the actual magnitude of resistance are still needed. Short-time recurrences of malaria cases were analyzed in different transmission scenarios over three years (2005, 2010, and 2015), selected according to malaria incidence. Multilevel models (binomial) were used to evaluate association of short-time recurrences with variables such as age. The zero-inflated Poisson scan model (scanZIP) was used to detect spatial clusters of recurrences up to 28 days. Recurrences compose less than 5% of overall infection, being more frequent in the age group under four years. Recurrences slightly increased incidence. No fixed clusters were detected throughout the period, although there are clustering sites, spatially varying over the years. This is the most extensive analysis of short-time recurrences worldwide which addresses the occurrence of P. vivax CQR. As an important step forward in malaria elimination, policymakers should focus their efforts on young children, with an eventual shift in the first line of malaria treatment to P. vivax.

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BACKGROUND: Mining in the Amazon exposes gold miners to various diseases, including malaria, whose control is still a major challenge. The environment of the mines contributes to the proliferation of vector mosquitoes and the precarious housing conditions facilitate transmission of the disease. Understanding gold miners' perceptions is essential for the formulation of strategies to fight malaria. A qualitative study was carried out in the municipality of Calçoene, state of Amapá, Brazilian Amazon adjointining the municipality of Oiapoque, that is in the border area with French Guiana and Suriname. METHODS: A semi-structured interview was applied to an intentional sample of 29 miners, a number determined by the theoretical saturation criterion. Thematic analysis was adopted to obtain the results and the Cohen's Kappa index was calculated to verify the agreement between observers during coding. RESULTS: The agreement between observers was verified by a Cohen's Kappa index of 0.82. Analysis of the interviews showed that gold miners were subjected to prejudice from the community due to forest diseases that they can transmit, and their activities are often associated with crime. When the miners return to their hometown after a period of mining, the urban population blames them for the onset of diseases such as malaria. Most participants in the survey did not know how malaria transmission occurs, and associated its occurrence with contaminated water and food. Participants reported not being afraid of the disease, trusting the diagnosis and available treatment, though this depends on where they are treated. The use of therapeutic resources, such as medicinal plants and medicines acquired in the illegal market, is very common in this population. Despite the challenges identified by the research subjects, they believe that the disease can be controlled, or the cases reduced, but there was low acceptability for a possible mass drug administration (MDA) intervention. CONCLUSION: Despite a recent reduction in malaria prevalence in Brazil, there are still vulnerable populations, such as gold miners, who help to perpetuate the existence of the disease in the Amazon. The lack of knowledge regarding how the transmission of malaria occurs, associated with myths regarding this and the use of traditional health practices and illegal drugs for the treatment of the disease without a specific diagnosis, jeopardizes the country's efforts to eliminate malaria. It is necessary to implement control programmes in these populations, especially those who frequently travel around the border region and to remote locations, which are difficult regions for health teams to access, thus hindering diagnostic and treatment actions. For this reason, understanding the perceptions of these individuals as well as their customs, beliefs and lifestyle, can assist in the production of targeted educational material and adoption of strategies in the elimination of malaria in the country.

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BACKGROUND: Glucose-6-phosphate dehydrogenase (G6PD) deficiency greatly hinders Plasmodium vivax malaria radical cure and further elimination due to 8-aminoquinolines-associated hemolysis. Although the deleterious health effects of primaquine in G6PD deficient individuals have been known for over 50 years, G6PD testing is not routinely performed before primaquine treatment in most P. vivax endemic areas. METHOD/PRINCIPAL FINDINGS: The qualitative CareStart G6PD screening test was implemented in 12 malaria treatment units (MTUs) in the municipality of Rio Preto da Eva, Western Brazilian Amazon, a malaria endemic area, between February 2019 and early January 2020. Training materials were developed and validated; evaluations were conducted on the effectiveness of training health care professionals (HCPs) to perform the test, the interpretation and reliability of routine testing performed by HCPs, and perceptions of HCPs and patients. Most HCPs were unaware of G6PD deficiency and primaquine-related adverse effects. Most of 110 HCPs trained (86/110, 78%) were able to correctly perform the G6PD test after a single 4-hour training session. The test performed by HCPs during implementation showed 100.0% (4/4) sensitivity and 68.1% (62/91) specificity in identifying G6PD deficient patients as compared to a point-of-care quantitative test (Standard G6PD). CONCLUSIONS/SIGNIFICANCE: G6PD screening using the qualitative CareStart G6PD test performed by HCPs in MTUs of an endemic area showed high sensitivity and concerning low specificity. The amount of false G6PD deficiency detected led to substantial loss of opportunities for radical cure.

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Plasmodium vivax is a world-threatening human malaria parasite, whose biology remains elusive. The unavailability of in vitro culture, and the difficulties in getting a high number of pure parasites makes RNA isolation in quantity and quality a challenge. Here, a methodological outline for RNA-seq from P. vivax isolates with low parasitemia is presented, combining parasite maturation and enrichment with efficient RNA extraction, yielding ~ 100 pg.µL-1 of RNA, suitable for SMART-Seq Ultra-Low Input RNA library and Illumina sequencing. Unbiased coding transcriptome of ~ 4 M reads was achieved for four patient isolates with ~ 51% of transcripts mapped to the P. vivax P01 reference genome, presenting heterogeneous profiles of expression among individual isolates. Amongst the most transcribed genes in all isolates, a parasite-staged mixed repertoire of conserved parasite metabolic, membrane and exported proteins was observed. Still, a quarter of transcribed genes remain functionally uncharacterized. In parallel, a P. falciparum Brazilian isolate was also analyzed and 57% of its transcripts mapped against IT genome. Comparison of transcriptomes of the two species revealed a common trophozoite-staged expression profile, with several homologous genes being expressed. Collectively, these results will positively impact vivax research improving knowledge of P. vivax biology.

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Plasmodium vivax is the most prevalent cause of malaria outside of Africa. P. vivax biology and pathogenesis are still poorly understood. The role of one highly occurring phenotype in particular where infected reticulocytes cytoadhere to noninfected normocytes, forming rosettes, remains unknown. Here, using a range of ex vivo approaches, we showed that P. vivax rosetting rates were enhanced by plasma of infected patients and that total immunoglobulin M levels correlated with rosetting frequency. Moreover, rosetting rates were also correlated with parasitemia, IL-6 and IL-10 levels in infected patients. Transcriptomic analysis of peripheral leukocytes from P. vivax-infected patients with low or moderated rosetting rates identified differentially expressed genes related to human host phagocytosis pathway. In addition, phagocytosis assay showed that rosetting parasites were less phagocyted. Collectively, these results showed that rosette formation plays a role in host immune response by hampering leukocyte phagocytosis. Thus, these findings suggest that rosetting could be an effective P. vivax immune evasion strategy.

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