The role of serum antibodies in the protection against rotavirus disease: an overview

Combatting infectious diarrhea: innovations in treatment and vaccination strategies

INTRODUCTION

The escalating prevalence of infectious diseases is an important cause of concern in society. Particularly in several developing countries, infectious diarrhea poses a major problem, with a high fatality rate, especially among young children. The condition is divided into four classes, namely, acute diarrhea, invasive diarrhea, acute bloody diarrhea, and chronic diarrhea. Various pathogenic agents, such as bacteria, viruses, protozoans, and helminths, contribute to the onset of this condition.

AREAS COVERED

The review discusses the scenario of infectious diarrhea, the prevalent types, as well as approaches to management including preventive, therapeutic, and vaccination strategies. The vaccination techniques are extensively discussed including the available vaccines, their advantages as well as limitations.

EXPERT OPINION

There are several approaches available to develop new-improved vaccines. In addition, route of immunization is important and aerosols/nasal sprays, oral route, skin patches, powders, and liquid jets to minimize needles can be used. Plant-based vaccines, such as rice, might save packing and refrigeration costs by being long-lasting, non-refrigerable, and immunogenic. Future research should utilize predetermined PCR testing intervals and symptom monitoring to identify persistent pathogens after therapy and symptom remission.

Acute rotavirus infection is associated with the induction of circulating memory CD4+ T cell subsets

Strong CD4⁺ T cell-mediated immune protection following rotavirus infection has been observed in animal models, but its relevance in humans remains unclear. Here, we characterized acute and convalescent CD4⁺ T cell responses in children who were hospitalized with rotavirus-positive and rotavirus-negative diarrhoea in Blantyre, Malawi. Children presenting with laboratory-confirmed rotavirus infection had higher proportions of effector and central memory T helper 2 cells during acute infection i.e., at disease presentation compared to convalescence, 28 days post-infection defined by a follow-up 28 days after acute infection. However, circulating cytokine-producing (IFN-γ and/or TNF-α) rotavirus-specific VP6-specific CD4⁺ T cells were rarely detectable in children with rotavirus infection at both acute and convalescent stages. Moreover, following whole blood mitogenic stimulation, the responding CD4⁺ T cells were predominantly non-cytokine producers of IFN-γ and/or TNF-α. Our findings demonstrate limited induction of anti-viral IFN-γ and/or TNF-α-producing CD4⁺ T cells in rotavirus-vaccinated Malawian children following the development of laboratory-confirmed rotavirus infection.

A Pooled Analysis of Sex Differences in Rotaviral Enteritis Incidence Rates in Three Countries Over Different Time Periods

Background: Sex differences in incidence rates (IRs) of infectious diseases could provide clues to the mechanisms of infection. The results of studies on sex differences in the incidence of rotaviral enteritis have been inconsistent.

Methods: We carried out a pooled analysis of sex differences in IRs for rotaviral enteritis in three countries for a period of 7–22 years. Male-to-female incidence rate ratios (IRRs) were computed by age group, country, and years of reporting. A meta-analytic methodology was used to combine IRRs. Metaregression was performed to evaluate the contribution of age group, country, and years of reporting to the IRR.

Results: Significantly higher IRs in males were found in the age groups 0–4, 5–9, and 10–14 years, with pooled IRRs (with 95% confidence intervals [CIs]) of 1.12 (1.09–1.14), 1.07 (1.05–1.09), and 1.13 (1.05–1.21), respectively. In adults, the sex differences were reversed with higher rates in females. The pooled male-to-female IRRs (with 95% CIs) were 0.66 (0.64–0.68), 0.78 (0.72–0.85), and 0.78 (0.72–0.84) for the age groups 15–44, 45–64, and 65+ years, respectively. Metaregression results demonstrated that age is responsible for much of the variation in IRRs.

Conclusions: The higher rotaviral enteritis IRs in males at a very early age suggest that sex-related factors unrelated to exposure may play a role. The higher IRs in adult females could result, at least partly, from behavioral and occupational factors.

The Epidemiological and clinical profiles of acute diarrhea due rotavirus in children aged 0-71 months hospitalized at Kalembe-lembe pediatric hospital in Kinshasa, Democratic Republic of Congo

This research is based on a retrospective analysis of medical records filed in the archives of the emergency departments of Kalembe-lembe Hospital in the provincial city of Kinshasa in the Democratic Republic of Congo. The study involved 324 records of patients aged 0-71 months admitted to the emergency departments and hospitalized for acute diarrhea from January 1 to December 31, 2015. The aim was to inventory the cases of rotavirus diarrhea and/or other germs (individually or in combination) to study their epidemiological and clinical aspects. Thus, the epidemiological and clinical parameters (age, sex, season, symptoms, frequency and physical aspects of stools, dehydration status and duration of hospitalization) of diarrheic children diagnosed as positive for rotavirus were compared with those infected with other germs (individually or in combination with rotavirus or other viruses). The search for the etiological agents of the diarrhea was performed in 56.48% of the cases. The results of this work allowed us to show: (i) a predominance of infections by viruses (69.94%) including rotavirus (48.08%), (ii) high rates of infections by etiological agents of diarrhea including rotavirus in children under 12 months, (iii) a high proportion of vomiting, (iii) a high proportion of vomiting, fever, physical asthenia and restlessness or frequent and liquid stools or moderate dehydration in children infected with rotavirus, (iv) specific clinical pictures according to the etiological agents of diarrhea or their combinations.

Plasma rotavirus-specific IgA and risk of rotavirus vaccine failure in infants in Malawi

BACKGROUND

Rotavirus vaccine efficacy is reduced in low-income populations, but efforts to improve vaccine performance are limited by lack of clear correlates of protection. While plasma rotavirus (RV)-specific IgA appears strongly associated with protection against rotavirus gastroenteritis in high-income countries, weaker association has been observed in low-income countries. We tested the hypothesis that lower RV-specific IgA is associated with rotavirus vaccine failure in Malawian infants.

METHODS

In a case-control study we recruited infants presenting with severe rotavirus gastroenteritis following monovalent oral rotavirus vaccination (RV1 vaccine failures). Conditional logistic regression was used to determine the odds of rotavirus seronegativity (RV-specific IgA<20 U/mL) in these cases compared 1:1 with age-matched, vaccinated, asymptomatic community controls. Plasma RV-specific IgA was determined by ELISA for all participants at recruitment, and for cases at 10 days post symptom onset. Rotavirus infection and genotype were determined by antigen testing and RT-PCR respectively.

RESULTS

In 116 age-matched pairs, infants with RV1 vaccine failure were more likely to be RV-specific IgA seronegative than controls: OR 3.1 (95%CI 1.6-5.9), p=0.001. In 60 infants with convalescent serology, 42/45 (93%, 95%CI 81-98%) infants seronegative at baseline became seropositive. Median rise in RV-specific IgA concentration following acute infection was 112.8 (IQR 19.1-380.6) fold.

CONCLUSIONS

In this vaccinated population with high residual burden of rotavirus disease, RV1 vaccine failure was associated with lower RV-specific IgA, providing further evidence of RV-specific IgA as a marker of protection. Robust convalescent RV-specific IgA response in vaccine failures suggests differences in wild-type and vaccine-induced immunity, which informs future vaccine development.

Virus neutralisation by intracellular antibodies

For decades antibodies were largely thought to provide protection in extracellular spaces alone, mediating their effector functions by mechanisms such as entry-blocking, complement activation and phagocyte recruitment. However, a wealth of research has shown that antibodies are also capable of neutralising numerous viruses inside cells. Efficacy has now been demonstrated at virtually all intracellular stages of the viral life cycle. Antibodies can neutralise viruses in endosomes by blocking uncoating, fusion mechanisms, or new particle egress. Neutralisation can also occur in the cytosol via recruitment of the intracellular antibody receptor TRIM21. In addition to these direct neutralisation effects, recent research has shown that antibodies can mediate virus control indirectly by promoting MHC class I presentation and thereby increasing the CD8 T cell response. This provides valuable new insight into how non-neutralising antibodies can mediate potent protection in vivo. Overall, the importance of understanding the mechanisms of intracellular neutralisation by antibodies is highlighted by the ongoing need to develop new methods to control viruses. Using or inducing antibodies to block virus replication inside cells is now an innovative approach used by several vaccination and therapeutic strategies.

Safety and immunogenicity of a novel oral hexavalent rotavirus vaccine：a phase I clinical trial

Background Rotavirus infections, prevalent in human populations, are caused mostly by group A viruses. Immunization against rotaviruses in infancy is currently the most effective and economical strategy to prevent rotavirus infection. This study evaluated the safety of a novel hexavalent rotavirus vaccine and analyzed its dose and immunogenicity.Methods This randomized, double-blinded, placebo-controlled phase I clinical trial enrolled healthy adults, toddlers, and infants in Zhengding County, Hebei Province, northern China. 40 adults and 40 children were assigned in a 2:1:1 ratio to receive one vaccine dose, placebo 1, and placebo 2, respectively. 120 6-12 week old infants were assigned equivalently into 3 groups. The infants in each group were assigned in a 2:1:1 ratio to receive three doses of vaccine, placebo 1, and placebo 2, at a 28-day interval. Adverse events (AEs) until 28 days after each dose and serious adverse events (SAEs) until 6 months after the third dose were reported. Virus shedding until 14 days after each dose in infants was tested. Geometric mean concentrations (GMCs) and seroconversion rates were measured for anti-rotavirus IgA by using an enzyme-linked immunosorbent assay (ELISA).Results The solicited and unsolicited AE frequencies and laboratory indexes were similar among the treatment groups. No vaccine-related SAEs were reported. The average percentage of rotavirus vaccine shedding in the infant vaccine groups was 5.00%. The post-3rd dose anti-rotavirus IgA antibody geometric mean concentrations (GMC) and seroconversion rate were higher in the vaccine groups than in the placebo groups.Conclusions The novel oral hexavalent rotavirus vaccine was generally well-tolerated in all adults, toddlers and infants, and the vaccine was immunogenic in infants.

In-vitro inhibitory effect of maternal breastmilk components on rotavirus vaccine replication and association with infant seroconversion to live oral rotavirus vaccine

BACKGROUND

Despite contributing to a significant reduction in rotavirus associated diarrhoea in highly burdened low- and middle-income countries, live attenuated, oral rotavirus vaccines have lower immunogenicity and efficacy in these settings in comparison to more developed countries. Breastmilk has been implicated among factors contributing to this lowered oral vaccine efficacy. We conducted in-vitro experiments to investigate the inhibitory effects of maternal antibody and other non-antibody components in breastmilk on rotavirus vaccine strain (Rotarix) multiplication in MA104 cell culture system and assessed associations with in-vivo vaccine seroconversion in vaccinated infants.

METHODS

Breastmilk samples were collected from mothers before routine rotavirus vaccination of their infant at 6 weeks of age. For each sample, whole breastmilk, purified IgA, purified IgG and IgG and IgA depleted breastmilk samples were prepared as exposure preparations. A 96 well microtitre plate was set up for each sample including a control in which only MA104 cells were grown as well as a virus control with MA104 cells and virus only. The outcome of interest was 50% inhibition dilution of each of the exposure preparations calculated as the titer at which 50% of virus dilution was achieved. Samples from 30 women were tested and correlated to vaccine seroconversion status of the infant. HIV status was also correlated to antiviral breastmilk proteins.

RESULTS

The mean 50% inhibitory dilution titer when whole breastmilk was added to virus infected MA104 cells was 14.3 (95% CI: 7.1, 22.7). Incubation with purified IgG resulted in a mean 50% inhibitory dilution of 5 (95%CI -1.6, 11.6). Incubating with purified IgA resulted in a mean 50% inhibitory dilution of 6.5 (95% CI -0.7, 13.7) and IgG and IgA depleted breastmilk did not yield any inhibition with a titer of 1.06 (95%CI 0.9, 1.2). Higher milk IgA levels contributed to a failure of infants to seroconvert. HIV was also not associated with any antiviral breastmilk proteins.

DISCUSSION AND CONCLUSION

Whole breastmilk and breastmilk purified IgG and IgA fractions showed inhibitory activity against the rotavirus vaccine Rotarix™ whilst IgA and IgG depleted breastmilk with non-antibody breastmilk fraction failed to show any inhibition activity in-vitro. These findings suggest that IgA and IgG may have functional inhibitory properties and indicates a possible mechanism of how mothers in rotavirus endemic areas with high titres of IgA and IgG may inhibit viral multiplication in the infant gut and would potentially contribute to the failure of their infants to serocovert. There was not association of HIV with either lactoferrin, lactadherin or tenascin-C concentrations.

An Optimized Reverse Genetics System Suitable for Efficient Recovery of Simian, Human, and Murine-Like Rotaviruses

An entirely plasmid-based reverse genetics (RG) system was recently developed for rotavirus (RV), opening new avenues for in-depth molecular dissection of RV biology, immunology, and pathogenesis. Several improvements to further optimize the RG efficiency have now been described. However, only a small number of individual RV strains have been recovered to date. None of the current methods have supported the recovery of murine RV, impeding the study of RV replication and pathogenesis in an in vivo suckling mouse model. Here, we describe useful modifications to the RG system that significantly improve rescue efficiency of multiple RV strains. In addition to the 11 group A RV segment-specific (+)RNAs [(+)ssRNAs], a chimeric plasmid was transfected, from which the capping enzyme NP868R of African swine fever virus (ASFV) and the T7 RNA polymerase were expressed. Second, a genetically modified MA104 cell line was used in which several components of the innate immunity were degraded. Using this RG system, we successfully recovered the simian RV RRV strain, the human RV CDC-9 strain, a reassortant between murine RV D6/2 and simian RV SA11 strains, and several reassortants and reporter RVs. All these recombinant RVs were rescued at a high efficiency (≥80% success rate) and could not be reliably rescued using several recently published RG strategies (<20%). This improved system represents an important tool and great potential for the rescue of other hard-to-recover RV strains such as low-replicating attenuated vaccine candidates or low-cell culture passage clinical isolates from humans or animals.IMPORTANCE Group A rotavirus (RV) remains as the single most important cause of severe acute gastroenteritis among infants and young children worldwide. An entirely plasmid-based reverse genetics (RG) system was recently developed, opening new ways for in-depth molecular study of RV. Despite several improvements to further optimize the RG efficiency, it has been reported that current strategies do not enable the rescue of all cultivatable RV strains. Here, we described a helpful modification to the current strategies and established a tractable RG system for the rescue of the simian RRV strain, the human CDC-9 strain, and a murine-like RV strain, which is suitable for both in vitro and in vivo studies. This improved RV reverse genetics system will facilitate study of RV biology in both in vitro and in vivo systems that will facilitate the improved design of RV vaccines, better antiviral therapies, and expression vectors.

Intracellular neutralisation of rotavirus by VP6-specific IgG

Rotavirus is a major cause of gastroenteritis in children, with infection typically inducing high levels of protective antibodies. Antibodies targeting the middle capsid protein VP6 are particularly abundant, and as VP6 is only exposed inside cells, neutralisation must be post-entry. However, while a system of poly immune globulin receptor (pIgR) transcytosis has been proposed for anti-VP6 IgAs, the mechanism by which VP6-specific IgG mediates protection remains less clear. We have developed an intracellular neutralisation assay to examine how antibodies neutralise rotavirus inside cells, enabling comparison between IgG and IgA isotypes. Unexpectedly we found that neutralisation by VP6-specific IgG was much more efficient than by VP6-specific IgA. This observation was highly dependent on the activity of the cytosolic antibody receptor TRIM21 and was confirmed using an in vivo model of murine rotavirus infection. Furthermore, mice deficient in only IgG and not other antibody isotypes had a serious deficit in intracellular antibody-mediated protection. The finding that VP6-specific IgG protect mice against rotavirus infection has important implications for rotavirus vaccination. Current assays determine protection in humans predominantly by measuring rotavirus-specific IgA titres. Measurements of VP6-specific IgG may add to existing mechanistic correlates of protection.

Prevalence and diversity of human rotavirus among Thai adults

Rotavirus infections have become one of the most common causes of infectious gastroenteritis in children. Although rotavirus infections have been intensively studied in infants and young children, the study in adults has been limited. As such, this study assessed the prevalence of rotaviruses and performed the molecular characterization of rotaviruses circulating in Thai adults experiencing acute gastroenteritis between January 2018 and December 2018. Group A human rotaviruses were detected in 100 feces samples by rapid immunochromatography. The peak incidence of infection occurred in February and began to decline in the summer months. From January 2018 to December 2018, there were 1344 acute gastroenteritis adult cases in the Hospital for Tropical Diseases, Bangkok, Thailand. Among these, 310 cases were rotavirus-suspected cases. Only 100 samples tested positive for rotavirus via an immunochromatography test. Twentynine out of the 100 rotavirus-positive samples were further characterized by real-time polymerase chain reaction. The G3[P8] strain was identified as the most prevalent (31.0%) followed by G1P[8], G8P[8] and G9P[8], and G2P[8], which accounted for 20.8%, 17.2%, and 13.8%, respectively. Because of the detection of rare rotavirus genotypes, such as G8, the surveillance of rotavirus epidemiology is crucial in monitoring new emergences of rotavirus strains, leading to a better understanding of the effects of strain variation for further vaccine development.

Comparative Sequence Analysis of Historic and Current Porcine Rotavirus C Strains and Their Pathogenesis in 3-Day-Old and 3-Week-Old Piglets

The increased prevalence of porcine group C rotavirus (PRVC) in suckling piglets and the emergence of new genetically distinct PRVC strains are concerning due to the associated significant economic losses they cause to the swine industry. We sequenced and analyzed two new PRVC strains, RV0104 (G3), and RV0143 (G6) and compared their pathogenesis with that of the historic strain Cowden (G1) in gnotobiotic (Gn) pigs. Near complete genome sequence analysis confirmed that these two strains were distinct from one another and the Cowden strain. VP1, VP2, VP6, NSP1-NSP3, and NSP5 genes were more similar between Cowden and RV0143, whereas VP3, VP7, and NSP4 shared higher nucleotide identity between Cowden and RV0104. Three-day-old and 3-week-old Gn piglets were inoculated with 10⁵ FFU/piglet of Cowden, RV0104 or RV0143, or mock. All 3-day-old piglets developed severe diarrhea, anorexia, and lethargy, with mean PRVC fecal shedding titers peaking and numerically higher in RV0104 and RV0143 piglets on post infection day (PID) 2. Histopathological examination of the small intestine revealed that the 3-day-old Cowden and RV0104 inoculated piglets were mildly affected, while significant destruction of small intestinal villi was observed in the RV0143 inoculated piglets. Consistent with the highest degree of pathological changes in the small intestines, the RV0143 inoculated piglets had numerically higher levels of serum IL-17 and IFN-α cytokines and numerically lower PRVC IgA geometric mean antibody titers. Milder pathological changes and overall higher titers of PRVC IgA antibodies were observed in 3-week-old vs. 3-day-old piglets. Additionally, diarrhea was only observed in RV0104 and RV0143 (but not Cowden) inoculated 3-week-old piglets, while levels of serum IL-10 and PRVC IgA antibodies were higher in Cowden inoculated pigs, consistent with the lack of diarrhea. Thus, we confirmed that these current, genetically heterogeneous PRVC strains possess distinct pathobiological characteristics that may contribute to the increased prevalence of PRVC diarrhea in neonatal suckling piglets.

Serum IgA Fc effector functions in infectious disease and cancer

Immunoglobulin (Ig) A is the most abundant antibody isotype present at mucosal surfaces and the second most abundant in human serum. In addition to preventing pathogen entry at mucosal surfaces, IgA can control and eradicate bacterial and viral infections through a variety of antibody‐mediated innate effector cell mechanisms. The role of mucosal IgA in infection (e.g. neutralization) and in inflammatory homeostasis (e.g. allergy and autoimmunity) has been extensively investigated; by contrast, serum IgA is comparatively understudied. IgA binding to fragment crystallizable alpha receptor plays a dual role in the activation and inhibition of innate effector cell functions. Mounting evidence suggests that serum IgA induces potent effector functions against various bacterial and some viral infections including Neisseria meningitidis and rotavirus. Furthermore, in the era of immunotherapy, serum IgA provides an interesting alternative to classical IgG monoclonal antibodies to treat cancer and infectious pathogens. Here we discuss the role of serum IgA in infectious diseases with reference to bacterial and viral infections and the potential for IgA as a monoclonal antibody therapy.

Parenterally Administered P24-VP8* Nanoparticle Vaccine Conferred Strong Protection against Rotavirus Diarrhea and Virus Shedding in Gnotobiotic Pigs

Current live rotavirus vaccines are costly with increased risk of intussusception due to vaccine replication in the gut of vaccinated children. New vaccines with improved safety and cost-effectiveness are needed. In this study, we assessed the immunogenicity and protective efficacy of a novel P24-VP8* nanoparticle vaccine using the gnotobiotic (Gn) pig model of human rotavirus infection and disease. Three doses of P24-VP8* (200 μg/dose) intramuscular vaccine with Al(OH)₃ adjuvant (600 μg) conferred significant protection against infection and diarrhea after challenge with virulent Wa strain rotavirus. This was indicated by the significant reduction in the mean duration of diarrhea, virus shedding in feces, and significantly lower fecal cumulative consistency scores in post-challenge day (PCD) 1-7 among vaccinated pigs compared to the mock immunized controls. The P24-VP8* vaccine was highly immunogenic in Gn pigs. It induced strong VP8*-specific serum IgG and Wa-specific virus-neutralizing antibody responses from post-inoculation day 21 to PCD 7, but did not induce serum or intestinal IgA antibody responses or a strong effector T cell response, which are consistent with the immunization route, the adjuvant used, and the nature of the non-replicating vaccine. The findings are highly translatable and thus will facilitate clinical trials of the P24-VP8* nanoparticle vaccine.

Surface Display of Antigen Protein VP8* of Porcine Rotavirus on Bacillus Subtilis Spores Using CotB as a Fusion Partner

Porcine rotavirus is a major cause of acute viral gastroenteritis in suckling piglets, and vaccination is considered to be an effective measure to control these infections. The development of a live mucosal vaccine using Bacillus subtilis spores as an antigen delivery vehicle is a convenient and attractive vaccination strategy against porcine rotavirus. In this study, a shuttle vector was constructed for the spore surface display of the spike protein VP8* from porcine rotavirus (the genotype was G5P[7]). A successful display of the CotB-VP8* fusion protein on the spore surface was confirmed by Western blot and immunofluorescence microscopy analysis. The capacity for immune response generated after immunization with the recombinant strain was evaluated in a mouse model. The intestinal fecal IgA and serum IgG were detected by enzyme-linked-immunosorbent serologic assay (ELISA). Importantly, recombinant strain spores could elicit strong specific mucosal and humoral immune responses. These encouraging results suggest that recombinant B. subtilis BV could provide a strategy for a potential novel application approach to the development of a new and safe mucosal subunit vaccine against porcine rotavirus.

Rotavirus Double Infection Model to Study Preventive Dietary Interventions

Rotaviruses are the main cause of acute diarrhea among young children worldwide with an increased frequency of reinfection. Several life style factors, such as dietary components, may influence such processes by affecting the outcome of the first rotavirus infection and therefore having a beneficial impact on the anti-rotavirus immune responses during any subsequent reinfections. The aim of this research was to develop a double-infection model in rat that mimics real-life clinical scenarios and would be useful in testing whether nutritional compounds can modulate the rotavirus-associated disease and immune response. Three experimental designs and a preventive dietary-like intervention were conducted in order to achieve a differential response in the double-infected animals compared to the single-infected ones and to study the potential action of a modulatory agent in early life. Diarrhea was only observed after the first infection, with a reduction of fecal pH and fever. After the second infection an increase in body temperature was also found. The immune response against the second infection was regulated by the preventive effect of the dietary-like intervention during the first infection in terms of specific antibodies and DTH. A rotavirus-double-infection rat model has been developed and is suitable for use in future preventive dietary intervention studies.

Cynomolgus Monkeys (Macaca fascicularis) as an Experimental Infection Model for Human Group A Rotavirus

Group A rotaviruses (RVA) are one of the most common causes of severe acute gastroenteritis in infants worldwide. Rotaviruses spread from person to person, mainly by faecal–oral transmission. Almost all unvaccinated children may become infected with RVA in the first two years of life. The establishment of an experimental monkey model with RVA is important to evaluate new therapeutic approaches. In this study, we demonstrated viral shedding and viraemia in juvenile–adult Macaca fascicularis orally inoculated with Wa RVA prototype. Nine monkeys were inoculated orally: seven animals with human RVA and two control animals with saline solution. During the study, the monkeys were clinically monitored, and faeces and blood samples were tested for RVA infection. In general, the inoculated animals developed an oligosymptomatic infection pattern. The main clinical symptoms observed were diarrhoea in two monkeys for three days, associated with a reduction in plasmatic potassium content. Viral RNA was detected in seven faecal and five sera samples from inoculated animals, suggesting virus replication. Cynomolgus monkeys are susceptible hosts for human Wa RVA infection. When inoculated orally, they presented self-limited diarrhoea associated with presence of RVA infectious particles in faeces. Thus, cynomolgus monkeys may be useful as animal models to evaluate the efficacy of new antiviral approaches.

Preventive Effect of a Synbiotic Combination of Galacto- and Fructooligosaccharides Mixture With Bifidobacterium breve M-16V in a Model of Multiple Rotavirus Infections

Rotavirus (RV) causes morbidity and mortality among infants worldwide, and there is evidence that probiotics and prebiotics can have a positive influence against infective processes such as that due to RV. The aim of this study was to evidence a preventive role of one prebiotic mixture (of short-chain galactooligosaccharide/long-chain fructooligosaccharide), the probiotic Bifidobacterium breve M-16V and the combination of the prebiotic and the probiotic, as a synbiotic, in a suckling rat double-RV infection model. Hyperimmune bovine colostrum was used as protection control. The first infection was induced with RV SA11 and the second one with EDIM. Clinical variables and immune response were evaluated after both infections. Dietary interventions ameliorated clinical symptoms after the first infection. The prebiotic and the synbiotic significantly reduced viral shedding after the first infection, but all the interventions showed higher viral load than in the RV group after the second infection. All interventions modulated ex vivo antibody and cytokine production, gut wash cytokine levels and small intestine gene expression after both infections. In conclusion, a daily supplement of the products tested in this preclinical model is highly effective in preventing RV-induced diarrhea but allowing the boost of the early immune response for a future immune response against reinfection, suggesting that these components may be potential agents for modulating RV infection in infants.

Rotavirus Vaccines: Effectiveness, Safety, and Future Directions

Rotavirus is the leading cause of diarrheal death among children < 5 years old worldwide, estimated to have caused ~ 215,000 deaths in 2013. Prior to rotavirus vaccine implementation, > 65% of children had at least one rotavirus diarrhea illness by 5 years of age and rotavirus accounted for > 40% of all-cause diarrhea hospitalizations globally. Two live, oral rotavirus vaccines have been implemented nationally in > 100 countries since 2006 and their use has substantially reduced the burden of severe diarrheal illness in all settings. Vaccine efficacy and effectiveness estimates suggest there is a gradient in vaccine performance between low child-mortality countries (> 90%) and medium and high child-mortality countries (57-75%). Additionally, an increased risk of intussusception (~ 1-6 per 100,000 vaccinated infants) following vaccination has been documented in some countries, but this is outweighed by the large benefits of vaccination. Two additional live, oral rotavirus vaccines were recently licensed and these have improved on some programmatic limitations of earlier vaccines, such as heat stability, cost, and cold-chain footprint. Non-replicating rotavirus vaccines that are parenterally administered are in clinical testing, and these have the potential to reduce the performance differential and safety concerns associated with live oral rotavirus vaccines.

Epidemiological Survey of Rotaviruses Responsible for Infantile Diarrhea by the Immunomolecular Technique in Cotonou (Benin, West Africa)

Rotavirus remains the main causative agent of gastroenteritis in young children, in countries that have not yet introduced the vaccine. Benin, in order to implement the WHO recommendations, projects to introduce the rotavirus vaccine in 2018 as part of its Expanded Program on Immunization. But before the introduction of this vaccine, epidemiological data on rotavirus infections and rotavirus genotypes circulating in Benin should be available. The aim of this study is to generate epidemiological data on infantile rotavirus diarrhea in Benin. In order to determine the epidemiological characteristics and electrophoretypes of rotavirus responsible for gastroenteritis in diarrheic children aged 0 to 5 years, 186 stool samples were collected according to the WHO Rotavirus Laboratory Manual from March 2014 to February 2015 at Suru-Lere University Hospital Center. Detection of rotavirus antigen was performed by the ELISA test, followed by molecular characterization using polyacrylamide gel electrophoresis. 186 stool samples were analyzed for rotavirus, and seventy-three (39.2%) were found to be positive for rotavirus antigen by ELISA. Children aged 3 to 24 months were the most affected by rotavirus diarrhea in this study. Of the seventy-three children affected with rotavirus diarrhea, 27 (37%) had vomiting accompanied by dehydration and fever. Results based on electrophoresis showed that, among the 73 samples tested, 38 yielded typical rotavirus electrophoretic migration profiles.

Estimating the incidence of rotavirus infection in children from India and Malawi from serial anti-rotavirus IgA titres

Accurate estimates of rotavirus incidence in infants are crucial given disparities in rotavirus vaccine effectiveness from low-income settings. Sero-surveys are a pragmatic means of estimating incidence however serological data is prone to misclassification. This study used mixture models to estimate incidence of rotavirus infection from anti-rotavirus immunoglobulin A (IgA) titres in infants from Vellore, India, and Karonga, Malawi. IgA titres were measured using serum samples collected at 6 month intervals for 36 months from 373 infants from Vellore and 12 months from 66 infants from Karonga. Mixture models (two component Gaussian mixture distributions) were fit to the difference in titres between time points to estimate risk of sero-positivity and derive incidence estimates. A peak incidence of 1.05(95% confidence interval [CI]: 0.64, 1.64) infections per child-year was observed in the first 6 months of life in Vellore. This declined incrementally with each subsequent time interval. Contrastingly in Karonga incidence was greatest in the second 6 months of life (1.41 infections per child year [95% CI: 0.79, 2.29]). This study demonstrates that infants from Vellore experience peak rotavirus incidence earlier than those from Karonga. Identifying such differences in transmission patterns is important in informing vaccine strategy, particularly where vaccine effectiveness is modest.

Live attenuated tetravalent (G1-G4) bovine-human reassortant rotavirus vaccine (BRV-TV): Randomized, controlled phase III study in Indian infants

BACKGROUND

Rotavirus remains the leading cause of diarrhoea among children <5years. We assessed immunogenic non-inferiority of a tetravalent bovine-human reassortant rotavirus vaccine (BRV-TV) over the licensed human-bovine pentavalent rotavirus vaccine RV5.

METHODS

Phase III single-blind study (parents blinded) in healthy infants randomized (1:1) to receive three doses of BRV-TV or RV5 at 6-8, 10-12, and 14-16weeks of age. All concomitantly received a licensed diphtheria, tetanus, pertussis, hepatitis B, Haemophilus influenzae type b conjugate vaccine (DTwP-HepB-Hib) and oral polio vaccine (OPV). Immunogenic non-inferiority was evaluated in terms of the inter-group difference in anti-rotavirus serum IgA seroresponse (primary endpoint), and seroprotection/seroresponse rates to DTwP-HepB-Hib and OPV vaccines. Seroresponse was defined as a ≥4-fold increase in titers from baseline to D28 post-dose 3. Non-inferiority was declared if the difference between groups (based on the lower limit of the 95% confidence interval [CI]) was above -10%. Each subject was evaluated for solicited adverse events 7days and unsolicited & serious adverse events 28days following each dose of vaccination.

RESULTS

Of 1195 infants screened, 1182 were randomized (590 to BRV-TV; 592 to RV5). Non-inferiority for rotavirus serum IgA seroresponse was not established: BRV-TV, 47.1% (95%CI: 42.8; 51.5) versus RV5, 61.2% (95%CI: 56.8; 65.5); difference between groups, -14.08% (95%CI: -20.4; -7.98). Serum IgA geometric mean concentrations at D28 post-dose 3 were 28.4 and 50.1U/ml in BRV-TV and RV5 groups, respectively. For all DTwP-HepB-Hib and OPV antigens, seroprotection/seroresponse was elicited in both groups and the -10% non-inferiority criterion between groups was met. There were 16 serious adverse events, 10 in BRV-TV group and 6 in RV5 group; none were classified as vaccine related. Both groups had similar vaccine safety profiles.

CONCLUSION

BRV-TV was immunogenic but did not meet immunogenic non-inferiority criteria to RV5 when administered concomitantly with routine pediatric antigens in infants.

Rotavirus specific Salivary and Fecal IgA in Indian Children and Adults

OBJECTIVE

To compare serum, salivary and fecal IgA responses in infants and adults following rotavirus vaccination.

STUDY DESIGN

Laboratory testing of samples from clinical trials.

SETTING

Medical College Hospital.

PARTICIPANTS

13 healthy adult volunteers not given vaccine, 20 healthy adult volunteers given one dose of bovine rotavirus tetravalent vaccine (Shantha Biotechnics), and 88 infants given 3 or 5 doses of Rotarix.

OUTCOME MEASURES

Serum, salivary and fecal IgA at one or more time points.

METHODS

IgA antibodies were estimated in serum, saliva and fecal samples by enzyme-linked immunosorbent assay, and normalized to total IgA in saliva.

RESULTS

In naturally infected adult volunteers, comparing serum and salivary IgA showed significant positive correlation (r=0.759; P=0.003). Of 20 vaccinated adults, complete samples showing change were available for 10; among them there was a significant positive correlation (P<0.05) between pre-vaccination serum and pre-vaccination salivary IgA but not between post-vaccination serum and post-vaccination salivary IgA. Of 88 infants given 3 or 5 doses of vaccine, 13 had more than 4-fold IgA response in serum, saliva and fecal samples, 6 had a 2-4 fold increases in all specimens. There was weak correlation between seroconversion rates measured by serum and salivary antibody responses. Salivary and stool assays were able to detect seroconversion in a few children in whom there was no detectable response in serum.

CONCLUSIONS

Evaluation of multiple samples is useful for intensive experimental study designs and may help improve our understanding of the induction and dynamics of immune responses to rotavirus vaccination.

Association of Maternal Immunity with Rotavirus Vaccine Immunogenicity in Zambian Infants

Introduction

Live attenuated oral vaccines against rotavirus (RV) have been shown to be less efficacious in children from developing countries. Reasons for this disparity are not fully understood. We assessed the role of maternal factors including breast milk RV-specific IgA, transplacentally acquired infant serum RV-specific IgG and maternal HIV status in seroconversion among Zambian infants routinely immunized with Rotarix™ (RV1).

Methods

420 mother-child pairs were recruited at infant age 6–12 weeks in Lusaka. Clinical information and samples were collected at baseline and at one month following the second dose of RV1. Determination of breast milk RV-specific IgA and serum RV-specific IgA and IgG was done using standardized ELISA. Seroconversion was defined as a ≥ 4 fold rise in serum IgA titre from baseline to one-month post RV1 dose 2, while seropositivity of IgA was defined as serum titre ≥ 40 and antibody variables were modelled on log-base 2. Logistic regression was used to identify predictors of the odds of seroconversion.

Results

Baseline infant seropositivity was 25.5% (91/357). The seroconversion frequency was 60.2% (130/216). Infants who were IgA seropositive at baseline were less likely to seroconvert compared to their seronegative counterparts (P = 0.04). There was no evidence of an association between maternal HIV status and seroconversion (P = 0.25). Higher titres of breast milk rotavirus-specific IgA were associated with a lower frequency of seroconverson (Nonparametric test for trend Z = -2.84; P<0.01): a two-fold increase in breast milk RV-specific IgA titres was associated with a 22% lower odds of seroconversion (OR = 0.80; 95% CI = 0.68–0.94; P = 0.01). There was seasonal variation in baseline breast milk rotavirus-specific IgA titres, with significantly higher GMTs during the cold dry months (P = 0.01).

Conclusion

Low immunogenicity of RV1 vaccine could be explained in part by exposure to high antibody titres in breast milk and early exposure to wild-type rotavirus infections. Potential interference of anti-RV specific IgA in breast milk and pre-vaccination serum RV specific-IgA and IgG titres with RV1 seroconversion and effectiveness requires further research.

Evaluating the Impact of Breastfeeding on Rotavirus Antigenemia and Disease Severity in Indian Children

Objectives

To evaluate the contribution of breastfeeding to Rotavirus (RV)-induced antigenemia and/or RNAemia and disease severity in Indian children (<2 yrs age).

Methods

Paired stool and serum samples were collected from (a) hospitalized infants with diarrhea (n = 145) and (b) healthy control infants without diarrhea (n = 28). Stool RV-antigen was screened in both groups by commercial rapid-test and enzyme immunoassay. The disease severity was scored and real-time-PCR was used for viral-load estimation. Serum was evaluated for RV-antigenemia by EIA and RV-RNAemia by RT-PCR. Data was stratified by age-group and breastfeeding status and compared.

Results

Presence of RV-antigenemia and RV-RNAemia was positively related with presence of RV in stool. Disease severity and stool viral-load was significantly associated with RV-antigenemia[(r = 0.74; CI:0.66 to 0.84; P<0.0001,R² = 0.59) and (r = -0.55; CI:-0.68 to -0.39; P<0.0001,R² = 0.31) respectively], but not with RV-RNAemia. There was significant reduction in RV-antigenemiarate in the breast-fed group compared to non-breastfed infants, especially in 0–6 month age group (P<0.001). Non-breastfed infants were at risk for RV-antigenemia with severe disease manifestations in form of high Vesikari scores correlating with high fever, more vomiting episodes and dehydration.

Conclusion

RV-antigenemia was common in nonbreastfed children with severe RV-diarrhea and correlated with stool RV-load and disease severity.

Current status of rotavirus vaccines

BACKGROUND

Rotaviruses remain the major cause of childhood diarrheal disease worldwide and of diarrheal deaths of infants and children in developing countries. The huge burden of childhood rotavirus-related diarrhea in the world continues to drive the remarkable pace of vaccine development.

DATA SOURCES

Research articles were searched using terms "rotavirus" and "rotavirus vaccine" in MEDLINE and PubMed. Articles not published in the English language, articles without abstracts, and opinion articles were excluded from the review. After preliminary screening, all articles were reviewed and synthesized to provide an overview of current vaccines and vaccination programs.

RESULTS

In this review of the global rotavirus vaccines and vaccination programs, the principles of rotavirus vaccine development and the efficacy of the currently licensed vaccines from both developed and developing countries were summarized.

CONCLUSIONS

Rotavirus is a common cause of diarrhea in children in both developed and developing countries. Rotavirus vaccination is a cost-effective measure to prevent rotavirus diarrhea.

Correlates of protection for rotavirus vaccines: Possible alternative trial endpoints, opportunities, and challenges

Rotavirus (RV) is a major vaccine-preventable killer of young children worldwide. Two RV vaccines are globally commercially available and other vaccines are in different stages of development. Due to the absence of a suitable correlate of protection (CoP), all RV vaccine efficacy trials have had clinical endpoints. These trials represent an important challenge since RV vaccines have to be introduced in many different settings, placebo-controlled studies are unethical due to the availability of licensed vaccines, and comparator assessments for new vaccines with clinical endpoints are very large, complex, and expensive to conduct. A CoP as a surrogate endpoint would allow predictions of vaccine efficacy for new RV vaccines and enable a regulatory pathway, contributing to the more rapid development of new RV vaccines. The goal of this review is to summarize experiences from RV natural infection and vaccine studies to evaluate potential CoP for use as surrogate endpoints for assessment of new RV vaccines, and to explore challenges and opportunities in the field.

Immunogenicity and efficacy in mice of an adenovirus-based bicistronic rotavirus vaccine expressing NSP4 and VP7

NSP4 and VP7 are important functional proteins of rotavirus. Proper combination of viral gene expression is favorable to improving the protection effect of subunit vaccine. In the present study, We evaluated the immunogenicity and efficacy of the bicistronic recombinant adenovirus (rAd-NSP4-VP7) and two single-gene expressing adenoviruses (rAd-NSP4, rAd-VP7). The three adenovirus vaccines were used to immunize mice by intramuscular or intranasal administration. The data showed significant increases in serum antibodies, T lymphocyte subpopulations proliferation, and cytokine secretions of splenocyte in all immunized groups. However, the serum IgA and neutralizing antibody levels of the rAd-NSP4-VP7 or rAd-VP7 groups were significantly higher than those of the rAd-NSP4, while the splenocyte numbers of IFN-γ secretion in the rAd-NSP4-VP7 or rAd-NSP4 groups was greater than that of the rAd-VP7. Furthermore, the efficacy evaluation in a suckling mice model indicated that only rAd-NSP4-VP7 conferred significant protection against rotavirus shedding challenge. These results suggest that the co-expression of NSP4 and VP7 in an adenovirus vector induce both humoral and cell-mediated immune responses efficiently, and provide potential efficacy for protection against rotavirus disease. It is possible to represent an efficacious subunits vaccine strategy for control of rotavirus infection and transmission.

[Epidemiological and clinical study of rotavirus acute diarrhea in infants at the hospital Jason Sendwe Lubumbashi, Democratic Republic of Congo]

Introduction

Le rotavirus est un problème de santé publique, non seulement dans les pays en développement où tous les enfants sont infectés avant l’âge de deux à trois ans mais aussi dans les pays développés où les conditions d'hygiène sont bonnes. La présente étude est la première à fournir des informations sur la prévalence de l'infection à rotavirus dans les diarrhées aiguës des nourrissons dans la ville de Lubumbashi. Elle s'est fixée comme objectifs de déterminer la fréquence hospitalière ainsi que la saisonnalité, les caractéristiques sociodémographiques, cliniques et évolutives de l'infection à Rotavirus chez les nourrissons admis à l'hôpital Jason Sendwe de Lubumbashi pour une diarrhée aiguë.

Méthodes

Il s'agit d'une étude descriptive et transversale menée pendant la période allant du 1^er janvier au 31 décembre 2012. Les paramètres épidémio-cliniques et évolutifs (âge, sexe, saison, signes cliniques, nombre journalier de selles et évolution) des enfants diagnostiqués positifs au rotavirus ont été comparés à ceux des enfants dont le test au rotavirus était négatif. Le degré de signification était de 5%.

Résultats

Nous avons récolté 193 cas de diarrhées aiguës dont 104 nourrissons étaient infectés par le rotavirus soit 53,8%. Des taux élevés des diarrhées à rotavirus sont enregistrés au cours de la saison sèche comparativement à la saison des pluies (p0,05). Par ailleurs, les enfants infectés par le rotavirus étaient 6 fois plus susceptibles de présenter une déshydratation modérée/sévère (p0,05).

Conclusion

Le rotavirus est confirmé dans la ville de Lubumbashi et touche souvent les enfants d’âge ≤12 mois, pendant la saison sèche sans distinction de sexe et conduit rapidement à une déshydratation modérée/sévère. Une prise en charge adaptée et précoce permet d’éviter les décès et l'assainissement du milieu, le lavage des mains, la prise d'eau potable et la vaccination contre le rotavirus sont les mesures préventives les plus efficaces contre les rotavirus et à conseiller dans notre communauté.

Safety and immunogenicity of a parenterally administered rotavirus VP8 subunit vaccine in healthy adults

BACKGROUND

The P2-VP8 subunit vaccine for the prevention of rotavirus gastroenteritis is comprised of a truncated VP8 subunit protein from the rotavirus Wa strain (G1[P8]) fused to the tetanus toxin P2 epitope, and adsorbed on aluminum hydroxide for intramuscular administration.

METHODS

Three groups of 16 adults were randomized to receive three injections of P2-VP8 (12) or placebo (4) at doses of 10, 30 or 60 μg of vaccine. IgG and IgA antibodies to P2-VP8 were assessed by ELISA in serum and lymphocyte supernatant (ALS). Serum samples were tested for neutralizing antibodies to homologous and heterologous strains of rotavirus.

RESULTS

The vaccine was well-tolerated. All vaccine recipients demonstrated significant IgA responses and all but one demonstrated IgG responses; in the 60 μg cohort, geometric mean titers (GMTs) rose 70- and 80-fold for IgA and IgG, respectively. Homologous neutralizing antibody responses were observed in about half of participants in all three dose cohorts; in the 60 μg cohort, GMTs against Wa rose from 128 to 992. Neutralizing antibody responses were robust to P[8] strains, moderate to P[4] strains and negligible to P[6] strains. ALS IgA responses were dose dependent.

CONCLUSIONS

The P2-VP8 subunit vaccine was well tolerated and evoked promising immune responses.

CLINICAL TRIALS REGISTRATION

NCT01764256.

A Prospective Hospital-based Surveillance to Estimate Rotavirus Disease Burden in Bhutanese Children under 5 Years of Age

As part of efforts to develop an informed policy for rotavirus vaccination, this prospective study was conducted to estimate the burden of rotavirus diarrhea among children less than 5 years old attended to the Department of Pediatrics, Jigme Dorji Wangchuk National Referral Hospital (JDWNRH), Thimphu, Bhutan. The duration of the study was three years, extending from February 2010 through December 2012. We estimated the frequency of hospitalization in the pediatric ward and dehydration treatment unit (DTU) for diarrhea and the number of events attributable to rotavirus infection among children under 5 years of age. During the study period, a total of 284 children (1 in 45) were hospitalized in the pediatric ward, and 2,220 (1 in 6) in the DTU with diarrhea among children residing in the Thimphu district. Group A rotavirus was detected in 32.5% and 18.8% of the stool samples from children hospitalized in the pediatric ward, respectively. Overall, 22.3% of the stool samples were rotavirus-positive, and the majority (90.8%) of them was detected in children under 2 years of age. From this study, we estimated that the annual incidence of hospitalization in the pediatric ward and DTU due to rotavirus diarrhea was 2.4/1000 (95% CI 1.7–3.4) and 10.8/1000 (95% CI 9.1–12.7) children, respectively. This study revealed that rotavirus is a major cause of diarrhea in Bhutanese children in Thimphu district and since no study has been performed previously, represents an important finding for policy discussions regarding the adoption of a rotavirus vaccine in Bhutan.

Association of serum antibodies with protection against rotavirus infection and disease in South Indian children

Serum antibodies play an important role in natural protection from rotavirus infection and disease, but conflicting estimates of association have emerged from epidemiological studies in different geographical settings. In this study, we aim to assess the relationship between pre-existing serum immunoglobulin (Ig)G and IgA titers with protection against rotavirus infection and disease in a birth cohort of Indian children. Children were recruited at birth and followed up for 36 months. Stool samples were collected every 2 weeks and during episodes of diarrhea and serum samples were obtained at least every 6 months. The incidence rate of rotavirus infection and diarrhea was 0.9 (95% CI: 0.88, 0.99) and 0.2 (95% CI: 0.19, 0.25) episodes per child year, respectively. The risk of rotavirus infection and diarrhea decreased with age, while antibody titers (IgG and IgA) increased with age. After adjusting for age and number of previous infections, higher levels of IgG and IgA were independently associated with reduced risk of rotavirus infection. However, we did not find a clear association of IgG or IgA with rotavirus diarrhea risk or a threshold level of protection. The study supports a correlation of serum antibodies in reducing the risk of rotavirus infections, however the potential of serum antibody titer as a correlate of protection is not clear for children in lower income settings.

Human and bovine rotavirus strain antigens for evaluation of immunogenicity in a randomized, double-blind, placebo-controlled trial of a single dose live attenuated tetravalent, bovine-human-reassortant, oral rotavirus vaccine in Indian adults

A single dose of live attenuated tetravalent (G1-G4) bovine human reassortant rotavirus vaccine (BRV-TV) was administered to healthy Indian adult volunteers, who were assessed for safety and immunogenicity of the vaccine with 3:1 randomization to vaccine or placebo. All 20 adult male volunteers in the study had rotavirus specific serum IgA at baseline. There were no side effects or adverse events reported. Administration of BRV-TV was not associated with fever, diarrhea, or altered liver transaminases. Rotavirus IgA seroconversion post single dose administration was 27%. This study shows that BRV-TV is non-reactogenic, safe and immunogenic in adults. The IgA units estimated for the same sample using human G1P[8] rotavirus strain as the antigen were consistently higher than with the bovine G6P[5] WC3 strain and the human G2P[4] DS-1 strain antigen. The use of different human and bovine rotavirus strains as antigens in a quantitative rotavirus specific serum IgA assay resulted in different estimations of IgA antibody in the same sample.

Improved characteristics and protective efficacy in an animal model of E. coli-derived recombinant double-layered rotavirus virus-like particles

Live rotavirus vaccines that are effective in middle- and high-income countries have been found to be less immunogenic and effective in infants in resource-limited settings. The virus-like particle (VLP) approach is promising for rotavirus vaccine development, but challenges remain for VLP production at large scale. In this study, rotavirus capsid VP2 and VP6 proteins were expressed in Escherichia coli and were assembled with high efficiency into homogeneous single-layered VP6-VLPs or double-layered VP2/6-VLPs (dl2/6-VLPs) through a post-purification assembly process. The dl2/6-VLPs were observed to have better thermal stability and antigenicity. Although the immunogenicity of VP6 trimers, VP6-VLPs and dl2/6-VLPs was comparable, the efficacy of the dl2/6-VLPs to protect against rotavirus-induced diarrhea in pups was significantly higher than that of the trimeric VP6 or the VP6-VLPs when assessed using a mouse maternal antibody model. Taken together, the recombinant dl2/6-VLP antigen, which is highly analogous to rotavirus virion-derived double-layered particles, is a viable candidate for vaccine development and has the potential to be a parenterally administered safe and efficacious rotavirus vaccine.

Association of serum anti-rotavirus immunoglobulin A antibody seropositivity and protection against severe rotavirus gastroenteritis: analysis of clinical trials of human rotavirus vaccine

Clinical trials of the human rotavirus vaccine Rotarix™ (RV1) have demonstrated significant reductions in severe rotavirus gastroenteritis (RVGE) in children worldwide. However, no correlate of vaccine efficacy (VE) has yet been established. This paper presents 2 analyses which aimed to investigate whether serum anti-RV IgA measured by ELISA 1 or 2 mo post-vaccination can serve as a correlate of efficacy against RVGE: (1) In a large Phase III efficacy trial (Rota-037), the Prentice criteria for surrogate endpoints was applied to anti-RV IgA seropositivity 1 mo post-vaccination. These criteria determine whether a significant vaccine group effect can be predicted from the surrogate, namely seropositivity (anti-RV IgA concentration >20 U/mL); (2) Among other GSK-sponsored RV1 VE studies, 8 studies which assessed immunogenicity at 1 or 2 mo post-vaccination in all or a sub-cohort of enrolled subjects and had at least 10 RVGE episodes were included in a meta-analysis to measure the regression between clinical VE and VE predicted from immunogenicity (VE1). In Rota-037, anti-RV IgA seropositivity post-vaccination was associated with a lower incidence of any or severe RVGE, however, the proportion of vaccine group effect explained by seropositivity was only 43.6% and 32.7% respectively. This low proportion was due to the vaccine group effect observed in seronegative subjects. In the meta-analysis, the slope of the regression between clinical VE and VE1 was statistically significant. These two independent analyses support the hypothesis that post-vaccination anti-RV IgA seropositivity (antibody concentration ≥20 U/mL) may serve as a useful correlate of efficacy in clinical trials of RV1 vaccines.

Rotavirus infection and its genetic characterization in non-hospitalized adults with acute gastroenteritis in Shanghai, China

Rotavirus is a major cause of acute gastroenteritis in infants and young children, while its role as a pathogen in adults has long been underappreciated. In order to describe the epidemiological patterns and genetic characteristics of rotavirus causing sporadic acute gastroenteritis in adults, hospital-based surveillance of rotavirus infections was conducted in Shanghai, China, between June 2010 and May 2011. Stool specimens were collected from outpatients with acute gastroenteritis admitted to three local hospitals. Rotavirus was detected using a colloidal gold test device. G and P genotyping were performed by multiplex PCR assays, and the VP7 gene of G9 strains were sequenced for further genetic characterization. Of 1,479 adult diarrheal stool samples examined during the 1-year surveillance period, 138 (9.3 %) were found to be rotavirus positive. G1 appeared to be the predominant genotype (35.5 %), suggesting a shift from genotype G3 to G1 in the study population in Shanghai. Meanwhile, a high frequency of genotype G9 (27.5 %) was also observed, and G9 was also predominant (38.1 %) in the small number of children (n=123) involved in the present study. Other specificities detected in adults were G2 (12.3 %) and G3 (13.8 %). For P genotyping, only two types, P[8] and P[4], were detected. P[8] was dominant in both children and adults. Sequence and phylogenetic analysis revealed that these strains could be divided into two different groups, with clustering within G9 lineage 3 and the subcluster of Japanese and Chinese G9 strains, respectively. In comparison to the previous data, G9 strains established themselves in a short time span as an important genotype in Shanghai, China.

[Epidemiology of rotavirus gastroenteritis among children under 5 years of age in Tunisia - results of sentinel hospital surveillance 2009 to 2011]

BACKGROUND

Rotavirus is the major cause of severe acute gastroenteritis among young children. The objectives of this study were to assess the epidemiology, clinical and virological features of community-acquired rotavirus acute gastroenteritis, in children under 5 years of age, hospitalized in Tunisia.

METHODS

A multicenter prospective observational study was conducted from April 2009 to March 2011, in 11 sentinel pediatric departments. Clinical data and stool samples were collected for all children under 5 years, admitted for acute gastroenteritis. Rotavirus was detected by Elisa immunoassay test and genotyped for G and P by semi-nested multiplex RT-PCR.

RESULT

A total of 621 children were enrolled in this study. Rotavirus was detected in 30.3% of cases (95% CI [26.7-33.9]). The estimated incidence rate of rotavirus acute gastroenteritis was 11 cases/100,000 child-years (95% CI [9.43-12.57]). This infection affected predominantly children aged under 24 months, and occurred mainly in winter (55.3%). Vomiting, fever and dehydration were observed in 79.6%, 69.5% and 57% respectively. Genotype analysis identified four G types (G1, G2, G3 and G4) and 4 P types (P[4], P[6], P[8] and P[9]). The most common G/P combination was G3P[8] (24.4%), followed by G4P[8] (13.3%) and G1P[8] (6.5%).

CONCLUSION

These results highlight the frequency and potential severity of rotavirus acute gastroenteritis in pediatric hospital settings. The present study could provide a sufficient database to make a decision related to the introduction of rotavirus vaccine in Tunisian national immunization program.

Efficacy of a pentavalent human-bovine reassortant rotavirus vaccine against rotavirus gastroenteritis among American Indian children

BACKGROUND

Before the widespread use of rotavirus vaccines, rotavirus was a leading cause of gastroenteritis among children. Navajo and White Mountain Apache children suffer a disproportionate burden of severe rotavirus disease compared with the general U.S. population.

METHODS

We enrolled Navajo and White Mountain Apache infants in a multicenter, double-blind, placebo-controlled trial of pentavalent human-bovine reassortant rotavirus vaccine (PRV). Subjects received 3 doses of vaccine or placebo at 4 to 10 week intervals, with the first dose given between 6 and 12 weeks of age. Gastroenteritis episodes were identified by active surveillance. Disease severity was determined by a standardized scoring system.

RESULTS

There were 509 and 494 randomized children who received vaccine and placebo, respectively. Among placebo recipients, the incidence of rotavirus gastroenteritis was 34.2 episodes/100 child-years (95% confidence interval [95% CI]: 25.8-38.9) versus 8.1 episodes/100 child-years (95% CI: 5.4-12.5) in the vaccine group. The percentage of rotavirus episodes caused by serotypes G1, G2, and G3 was 72.3%, 23.4%, and 2.1%, respectively. There were no severe rotavirus episodes among vaccinees and 4 among placebo recipients. PRV was 77.1% (95% CI: 59.7-87.6), 89.5% (95% CI: 65.9-97.9), and 82.9% (95% CI: 61.1-93.6) effective against G1-G4 rotavirus disease, severe and moderate rotavirus disease combined, and outpatient visits for rotavirus disease, respectively. The risk of adverse events was similar for the vaccine and placebo groups.

CONCLUSIONS

PRV was highly effective in preventing rotavirus disease and related health care utilization in these American Indian infants. Vaccine efficacy and immunogenicity were similar to the overall study population enrolled in the multicenter trial.

Human rotavirus genotypes circulating in Brazil before and after a nationwide rotavirus vaccination program established in 2006

Accounting for an estimated 600,000 deaths worldwide each year, rotaviruses are recognized as the most important etiologic agents causing severe acute gastroenteritis among children under the age of five years. In Brazil, until rotavirus vaccination was established in the public health system in 2006, acute gastroenteritis striking children under five years and caused by these viruses was clearly associated with 3.5 million episodes of diarrhea, 650,000 visits to outpatient health care facilities, 92,000 hospitalizations, and 850 deaths each year. After the introduction of the rotavirus vaccine in Brazil in March 2006, studies all over the country have been comparing rotavirus genotypes circulating in the recent pre- and postvaccination era. Most of these studies have reported a high prevalence of the G2P[4] genotype and also a decrease in rotavirus detection all over Brazil after the introduction of the vaccine. So far, these are preliminary studies, as a longer period of time is necessary to establish if this high prevalence of G2P[4] is due to selective pressure by the vaccine on the circulating viruses or to a normal genotype fluctuation, and if it will have any impact on vaccine efficacy in the future. This review describes results from the most recent studies addressing this issue and on rotavirus genotypic variability in Brazil.