RESUMO
Serum responses to oral cholera vaccines were assessed in three paediatric vaccine trials, two in León, Nicaragua and one in Stockholm, Sweden. A calibrated anti-cholera toxin B subunit (CTB) IgA ELISA was used together with an assay for vibriocidal antibodies. Swedish children had lower pre-vaccination levels of antibody, but serum responses were more pronounced in Swedish children than in Nicaraguan children. Post-vaccination levels of anti-toxin antibody were generally above those found after natural infections with enterotoxigenic Escherichia coli, that cross-reacts serologically with Vibrio cholerae. Adverse events seen after vaccination were generally mild and of little clinical significance.
Assuntos
Anticorpos Antibacterianos/biossíntese , Vacinas contra Cólera/imunologia , Vacinação , Vacinas de Produtos Inativados/imunologia , Vibrio cholerae/imunologia , Administração Oral , Calibragem , Criança , Pré-Escolar , Vacinas contra Cólera/administração & dosagem , Ensaios Clínicos como Assunto , Método Duplo-Cego , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Lactente , Masculino , Nicarágua , Segurança , Testes Sorológicos , Suécia , Vacinas de Produtos Inativados/administração & dosagemRESUMO
BACKGROUND: Rotavirus is an important cause of dehydrating diarrhea in young children throughout the world. Knowledge about frequency of reinfections, development of immunity to the virus and the possible protective effect of breast milk is important, in particular in relation to possible strategies for immunization. METHODS: A prospective study of rotavirus infections in a cohort of 235 infants followed from birth until 2 years of age was performed in León, Nicaragua. Fecal and serum specimens were collected at specified times, and stools were also obtained during episodes of diarrhea. Fecal specimens were screened by rotavirus antigen detection and serum and colostral specimens were analyzed by isotype-specific rotavirus antibody enzyme-linked immunosorbent assay. RESULTS: As judged by anti-rotavirus IgA antibody seroconversion and/or demonstration of rotavirus antigen in fecal specimens, > 50% of the babies had evidence of past rotavirus infection by the age of 2 months. The total incidence of rotavirus infections, including many reinfections, was 0.7 infection/child-year, of which only 17% were associated with diarrhea. The time from birth to the first demonstration of rotavirus in stool samples correlated significantly with the concentration of anti-rotavirus IgA antibodies in colostrum. There was also a tendency toward a relationship between long duration of breast-feeding and asymptomatic infection. CONCLUSIONS: Rotavirus infections are acquired very early in infants in León, Nicaragua, and reinfections are common. Most infections are asymptomatic. Breast milk appears to confer partial protection against rotavirus infection, probably mediated by specific IgA antibodies. To be effective rotavirus vaccination would probably have to be given at a very early age to infants in developing countries.
Assuntos
Infecções por Rotavirus/imunologia , Anticorpos Antivirais/sangue , Pré-Escolar , Fezes/virologia , Feminino , Humanos , Imunoglobulina A/sangue , Imunoglobulina G/sangue , Lactente , Recém-Nascido , Masculino , Estudos Prospectivos , Recidiva , Rotavirus/classificação , Infecções por Rotavirus/prevenção & controle , VacinaçãoRESUMO
Diarrheal episodes with enterotoxigenic Escherichia coli (ETEC) were prospectively monitored during the first 2 years of life in a cohort of 235 infants from Leon, Nicaragua. ETEC was an etiological finding in 38% (310 of 808) of diarrheal episodes and in 19% (277 of 1,472) of samples taken as asymptomatic controls at defined age intervals (P = <0.0001). The majority of diarrheal episodes (80%) occurred before 12 months of age. The major ETEC type was characterized by colonization factor CFA I and elaboration of both heat-labile enterotoxin and heat-stable enterotoxin (ST). The proportion of E. coli strains with CFA I was significantly higher in cases with diarrhea (P = 0.002). The second most prevalent type showed putative colonization factor PCFO166 and production of ST. The prevalence of PCFO166 was approximately 20%, higher than reported before. Children with a first CFA I episode contracted a second ETEC CFA I infection 24% of the time, compared with 46% for ETEC strains of any subtype. Most of the ETEC episodes were of moderate severity, and only 5% (15 of 310) were characterized as severe. In conclusion, our results give valuable information for the planning of intervention studies using ETEC vaccines.
Assuntos
Diarreia Infantil/epidemiologia , Enterotoxinas/análise , Infecções por Escherichia coli/epidemiologia , Escherichia coli/isolamento & purificação , Proteínas de Fímbrias , Fatores Etários , Proteínas de Bactérias/análise , Diarreia Infantil/microbiologia , Enterotoxinas/genética , Escherichia coli/química , Escherichia coli/patogenicidade , Infecções por Escherichia coli/microbiologia , Feminino , Seguimentos , Humanos , Incidência , Recém-Nascido , Masculino , Nicarágua/epidemiologia , Estudos Prospectivos , RecidivaRESUMO
We analyzed the prevalence of rotavirus in 296 children age between 3 and 36 months who were hospitalized in 1994 with severe gastro-enteritis at two health centres for diarrhoea treatment in León, Nicaragua. Enteric viruses were detected in 96 (32.4%) of the children and rotaviruses were the most common pathogens detected in 84 (28%). The majority of rotavirus infections occurred in children less than 1 year old and all strains isolated belonged to subgroup II and had 'long' RNA patterns. Molecular epidemiology of 55 rotavirus strains revealed that all had the same RNA migration pattern and serotyping of 37 strains by PCR technology revealed that all isolates belonged to serotype 3. A significant observation was that only one electropherotype of rotavirus circulated. No non-group A rotaviruses were found by RNA gel electrophoresis. Adenoviruses were found by ELISA in 14 of 265 (5%) children and were most frequently detected during the 1st year of life. Of 103 faecal samples analyzed by electron microscopy, four contained small round structured viruses.