No abstract

The class-specific antibody responses to serotype 1 rotavirus structural proteins were examined by immunoblotting with sera obtained from young children hospitalized with acute rotavirus diarrhea caused by serotype 1. All were believed to be primary infections. Three consecutive serum samples were obtained from 16 patients during the acute and convalescent phases of the disease and then approximately 4 months later. Immunoglobulin G (IgG)-class antibody responses to two inner capsid proteins (VP2 and VP6) and to the major homologous outer capsid protein (VP7) were detected in all patients. Antibody responses to VP6 were rapid, increased in intensity during 20 to 40 days after the onset of symptoms, and persisted for more than 4 months. Responses to VP2 and VP7 were more delayed, were maximal in convalescent-phase sera, and decreased markedly in intensity 4 months after the onset of symptoms in the majority of children. Two patients with evidence of mixed infection showed persisting high levels of antibody to VP7. Responses to the outer capsid protein VP4 were detected in 67% of patients, peaked at 20 to 40 days after the onset of symptoms, and were no longer detected at 4 months in the majority of patients. It is likely that the immunoblotting technique underestimated responses to VP4. Acuteand convalescent-phase sera (known to contain antirotavirus IgM or IgA measured by enzyme immunoassay) were also examined by immunoblotting. IgM-and IgA-class antibody responses to viral proteins VP2, VP4, and VP7 appeared to be qualitatively identical to those observed for IgG in the same serum samples.2 to 4 weeks after the onset of gastroenteritis in all cases,

Infection with reovirus serotype 3 (reo 3) has been postulated to be associated with extrahepatic biliary atresia (EHBA) in infants, and with neonatal hepatitis (NNH). We have investigated this association by assaying antireo 3 antibodies in sera from infants (aged < 4 months) with EHBA (n = 40), NNH (59), cholestatic liver disease due to other causes (61) and control infants with no liver disease (138). Antireo 3 immunoglobulins (Ig) of the G, A and M classes were measured by enzyme-linked immunosorbent assay. No differences in the prevalence of antireo 3 IgG or IgA were found between any of the four groups. A significantly higher prevalence of positive antireo 3 IgM was found in infants with EHBA (12/40), NNH (12/59) or cholestatic liver disease associated with parenteral nutrition (7/17), alpha-1 antitrypsin deficiency (4/15) or a variety of other causes (15/29) compared with control infants (13/138). These data support an association between reovirus 3 infection and cholestatic liver disease in infants. The nature of this association may differ for EHBA, NNH and cholestatic liver disease due to other causes, and remains to be determined.

Rotaviruses are the single most important causes of severe acute diarrhoea in children worldwide. Despite success in developing vaccines, there is still a lack of knowledge about many components of the immune response, particularly those to non-structural proteins. This study established radioimmunoprecipitation (RIP) assays using labeled G1P[8], G2P[4], and G4P[6] human rotaviruses to examine the spectrum and duration of rotavirus antibodies in sera collected sequentially for 18-36 months from 27 children after hospitalization for primary rotavirus gastroenteritis. Five children experienced rotavirus re-infections. Primary responses detected to non-structural protein NSP2 declined to baseline after 100-150 days. Responses were heterotypic between NSP2 of G1P[8] and G4P[8] rotaviruses. Re-infections after 465-786 days boosted antibody levels to NSP2of both serotypes, together with the appearance of anti-NSP2 to G2P[4], even though there was no evidence of infection with this serotype. We developed an enzyme-immunoassay to measure sequential levels of anti-NSP2 IgG and IgA, using recombinant (heterotypic) NSP2 derived from SA11 (G3P[2]). Anti-NSP2 IgG and IgA were detected in sera from 23/23 (100%) and 18/24 (75%) of children after primary infection, declined to baseline after 100-150 days, were boosted after rotavirus re-infections, and again declined to baseline 150 days later. Anti-NSP2 IgA was also detected after primary infection, in duodenal juice from 14/16 (87%), and faecal extract from 11/19 (57%) of children. Sequential estimation of anti-NSP2 EIA levels in sera could be a sensitive index of rotavirus infection and re-infection. The potential of anti-NSP2 to limit viral replication after re-infection deserves further study.