Detection of anti-rotavirus IgG, IgM, and IgA antibodies in healthy subjects, rotavirus infections, and immunodeficiencies by immunoblotting

Molecular characterisation of rotavirus strains detected during a clinical trial of the human neonatal rotavirus vaccine (RV3-BB) in Indonesia

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Equine-like G3P[8] the major cause of gastroenteritis during RV3-BB efficacy trial.

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The Indonesian equine-like G3P[8] strain was genetically similar to Hungarian and Spanish strains.

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Equine-like G3P[8] strain is an emerging cause of gastroenteritis in Indonesia.

Background

The RV3-BB human neonatal rotavirus vaccine aims to provide protection from severe rotavirus disease from birth. The aim of the current study was to characterise the rotavirus strains causing gastroenteritis during the Indonesian Phase IIb efficacy trial.

Methods

A randomized, double-blind placebo-controlled trial involving 1649 participants was conducted from January 2013 to July 2016 in Central Java and Yogyakarta, Indonesia. Participants received three doses of oral RV3-BB vaccine with the first dose given at 0–5 days after birth (neonatal schedule), or the first dose given at ∼8 weeks after birth (infant schedule), or placebo (placebo schedule). Stool samples from episodes of gastroenteritis were tested for rotavirus using EIA testing, positive samples were genotyped by RT-PCR. Full genome sequencing was performed on two representative rotavirus strains.

Results

There were 1110 episodes of acute gastroenteritis of any severity, 105 episodes were confirmed as rotavirus gastroenteritis by EIA testing. The most common genotype identified was G3P[8] (90/105), the majority (52/56) of severe (Vesikari score ≥11) rotavirus gastroenteritis episodes were due to the G3P[8] strain. Full genome analysis of two representative G3P[8] samples demonstrated the strain was an inter-genogroup reassortant, containing an equine-like G3 VP7, P[8] VP4 and a genogroup 2 backbone I2-R2-C2-M2-A2-N2-T2-E2-H2. The complete genome of the Indonesian equine-like G3P[8] strain demonstrated highest genetic identity to G3P[8] strains circulating in Hungary and Spain.

Conclusions

The dominant circulating strain during the Indonesian Phase IIb efficacy trial of the RV3-BB vaccine was an equine-like G3P[8] strain. The equine-like G3P[8] strain is an emerging cause of severe gastroenteritis in Indonesia and in other regions.

Serological responses to rotavirus NSP2 following administration of RV3-BB human neonatal rotavirus vaccine

Serum rotavirus IgA responses are an imperfect non-mechanistic correlate of protection, and the lack of an accurate serological marker is a challenge to the development of new rotavirus vaccines. Serological responses to rotavirus NSP2 occur following wild-type infection; however, it is unknown if serological responses to NSP2 occur following administration of rotavirus vaccines. The phase IIa immunogenicity trial of RV3-BB provided an opportunity to investigate the serological responses to NSP2 following vaccination. Healthy, full-term babies (n = 96) were previously recruited as part of a phase IIa safety and immunogenicity trial in Dunedin, New Zealand between January 2012 and April 2014. Participants received three doses of oral RV3-BB vaccine with the first dose given at 0–5 days after birth (neonatal schedule), or the first dose given at about 8 weeks after birth (infant schedule), or to receive placebo (placebo schedule). Serum IgA and IgG antibody responses to total RV3-BB and NSP2 protein (RV3-BB) were assessed using ELISA. Despite significant serum IgA response against total RV3-BB, we were unable to demonstrate a significant serological response to NSP2 in participants receiving RV3-BB when compared to placebo. Heterotypic antibodies against multiple NSP2 genotypes were detected following RV3-BB vaccination. Our data demonstrates that while serological responses to NSP2 were detectable in a subset of participants, it is a less useful marker when compared to total rotavirus serum IgA response.

Development of antirotavirus agents in Asia

Human rotaviruses are the major etiologic agents of diarrhea in infants and young children under 2 years of age worldwide. Rotavirus diarrhea is a life-threatening disease for children; many efforts are made to reduce the morbidity and mortality in Asia. To date many natural compounds and some Western medicines have exhibited their antirotavirus effects in clinical studies, in animal experiments and in vitro. Compared with antirotavirus agents in the USA and Europe, natural compounds have been identified as ideal candidates for antirotaviral drugs in Asia because they are cheaper and effective, have no side-effect and no toxicity. We have attempted to reveal the antirotavirus mechanism of some natural compounds. We found that cacao pigment, tea extract and pine seed shell extract inhibit rotavirus adsorption to cells while cacao pigment may also inhibit rotavirus reproduction in vitro. The usage of antirotavirus agents in Asia demonstrated that additional effective approaches to control rotavirus infection, such as antirotavirus agents, are necessary, in particular for the children with rotavirus diarrhea who have severe complications.

Viral proteins VP2, VP6, and NSP2 are strongly precipitated by serum and fecal antibodies from children with rotavirus symptomatic infection

Rotavirus-specific IgA has been correlated with immune protection against rotavirus reinfection and symptomatic disease. Systemic and mucosal antibody responses were determined by an enzyme-linked immunosorbent assay in 11 infants with severe rotavirus gastroenteritis. Geometric mean titers of antirotavirus serum IgG and IgA antibodies were significantly higher during the convalescence of the disease (P < 0.001 vs. acute-phase titers). Rotavirus-specific fecal sIgA antibodies increased 4 times during the convalescence in 9 (81.8%) children (P < 0.001). The serum IgG and IgA antibody and fecal sIgA antibody responses to individual rotavirus polypeptides were characterized by radioimmunoprecipitation assay (RIPA) using Staphylococcus aureus protein A and the lectin jacalin to precipitate IgG- and IgA-immune complexes, respectively. The main IgG response was directed toward the structural viral proteins VP2, VP4, and VP6 and toward the nonstructural protein NSP2. Serum IgA reactivity was detected by RIPA in all serum samples, with major responses to VP2, VP6, and NSP2. Interestingly, fecal sIgA in convalescent samples reacted strongly toward NSP2 and VP6. These data reinforce the antigenic importance of rotaviral proteins other than VP4 and VP7, such as VP2, VP6, and NSP2, as main targets in the immune response to rotavirus.

Humoral immunity patterns based on antibody reactivity to rotavirus antigens in Brazilian children under 5 years of age

The age distribution of antibody to simian rotavirus (SA-11) was studied in serum specimens obtained from 399 children aged to 5 years and living in the city of Recife (PE), located in the north eastern region of Brazil. Sera were examined for group-specific rotavirus antibody using a blocking enzyme immunoassay (bELISA) and a hemagglutination inhibition antibody (HIA) test, and for anti-VP2, anti-VP4, anti-VP6, and anti-VP7 antibodies using an immunoblotting assay (IBA). Antibody prevalence was similar in all bELISA and HIA assays, showing a steep rise in the 6-to 17-month-old age groups. The results indicate early acquisition of antibody to rotavirus. The majority of children aged 2 to 4 years had bELISA (50% to 60%) and HIA (70% to 81%) antibodies. There was an association in prevalence data obtained by HIA and bELISA with immunoblotting (IBA), revealing four serologic profiles. Children with profiles I and II (60%) respectively had HAI and ELISA antibody or HAI antibody alone and all had immunoprotective antibodies to VP4 and/or VP7. These children were regarded as "immune," resembling convalescent patients with a rotavirus infection. Children with profile III (4%) had no HIA antibody and only non-protective anti-VP6 and/or VP7 antibody, and were considered to be "partially immune." Children with profile IV (36%) had no detectable antibody and were classified as "nonimmune." These children should be considered to be susceptible to rotavirus infection, with the risk of developing clinically severe diarrhea.

The status of rotavirus vaccines in 1990

The status of rotavirus (RV) vaccines in 1990 is reviewed with particular reference to the range of RV strains which infect human beings as well as the antibody response and immunity to naturally acquired RV infections. The requirements for an ideal vaccine are stated and the various approaches towards developing RV vaccines are described. Results of various field trials are given and finally important questions are posed which remain to be addressed if success in producing an ideal vaccine is to be achieved.

Homotypic serum antibody responses to rotavirus proteins following primary infection of young children with serotype 1 rotavirus

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 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. Acute- and 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.

Detection of immunoglobulin G, M, and A antibodies to enterovirus structural proteins by immunoblot technique in echovirus type 4-infected patients

Paired serum specimens from 24 patients with echovirus (EV) type 4 infection by virus isolation were tested by the immunoblot technique for the presence of IgG, IgM, and IgA antibodies to EV4 structural proteins. Single sera from 20 patients without neutralizing enterovirus IgM were used as controls. All the sera from EV4-infected patients had IgG antibodies to VP1 of EV4 but also 13 out of the 20 controls. 23 out of 24 EV4-infected patients elicited IgM and IgA specific antibodies to VP1, a pattern highly significant as compared with controls (3/20 for IgM and 8/20 for IgA). In 16 out of the 24 EV4-infected patients, the IgM antibodies were also directed against VP2 (versus 2 out of 20 in the control group). Anti-VP2 IgA were detected in 4 out of the 24 EV4 patients (versus 0 in controls). The 24 paired sera from EV4-infected subjects were also tested by immunoblot technique against three other enteroviruses: EV21, coxsackievirus A9 and poliovirus 1. Cross-reactivities were observed to a large extent against VP1 and VP2 proteins with the three classes of antibodies. These results confirm the data of previous studies on the reactivity of IgM antibodies to various structural proteins that IgG antibodies react exclusively to VP1. Furthermore, this study demonstrates the occurrence of circulating IgA antibodies directed to VP1 and sometimes VP2 in the course of enterovirus infection. The potential interest of this latter finding for diagnosis requires further investigation.

Detection of anti rotavirus coproantibodies by immunoblotting technique

IgA and IgG coproantibodies to individual simian rotavirus (SA 11) structural polypeptides were detected in healthy infants in nursery homes. The number of immunoblottable peptides differed from individual to individual. Coproantibodies were also detected at the convalescent stage of rotavirus infection in two patients but not during the acute stage. This method is useful for confirming the diagnosis of rotavirus infection serologically without the need for paired sera.