Development of candidate rotavirus vaccines

Formulation development of a live attenuated human rotavirus (RV3-BB) vaccine candidate for use in low- and middle-income countries

Formulation development was performed with the live, attenuated, human neonatal rotavirus vaccine candidate (RV3-BB) with three main objectives to facilitate use in low- and middle- income countries including (1) a liquid, 2-8°C stable vaccine, (2) no necessity for pre-neutralization of gastric acid prior to oral administration of a small-volume dose, and (3) a low-cost vaccine dosage form. Implementation of a high-throughput RT-qPCR viral infectivity assay for RV3-BB, which correlated well with traditional FFA assays in terms of monitoring RV3-BB stability profiles, enabled more rapid and comprehensive formulation development studies. A wide variety of different classes and types of pharmaceutical excipients were screened for their ability to stabilize RV3-BB during exposure to elevated temperatures, freeze-thaw and agitation stresses. Sucrose (50-60% w/v), PEG-3350, and a solution pH of 7.8 were selected as promising stabilizers. Using a combination of an in vitro gastric digestion model (to mimic oral delivery conditions) and accelerated storage stability studies, several buffering agents (e.g., succinate, adipate and acetate at ~200 to 400 mM) were shown to protect RV3-BB under acidic conditions, and at the same time, minimize virus destabilization during storage. Several optimized RV3-BB candidate formulations were identified based on negligible viral infectivity losses during storage at 2-8°C and -20°C for up to 12 months, as well as by relative stability comparisons at 15°C and 25°C (up to 12 and 3 months, respectively). These RV3-BB stability results are discussed in the context of stability profiles of other rotavirus serotypes as well as future RV3-BB formulation development activities.

Overview of the Development, Impacts, and Challenges of Live-Attenuated Oral Rotavirus Vaccines

Safety, efficacy, and cost-effectiveness are paramount to vaccine development. Following the isolation of rotavirus particles in 1969 and its evidence as an aetiology of severe dehydrating diarrhoea in infants and young children worldwide, the quest to find not only an acceptable and reliable but cost-effective vaccine has continued until now. Four live-attenuated oral rotavirus vaccines (LAORoVs) (Rotarix^®, RotaTeq^®, Rotavac^®, and RotaSIIL^®) have been developed and licensed to be used against all forms of rotavirus-associated infection. The efficacy of these vaccines is more obvious in the high-income countries (HIC) compared with the low- to middle-income countries (LMICs); however, the impact is far exceeding in the low-income countries (LICs). Despite the rotavirus vaccine efficacy and effectiveness, more than 90 countries (mostly Asia, America, and Europe) are yet to implement any of these vaccines. Implementation of these vaccines has continued to suffer a setback in these countries due to the vaccine cost, policy, discharging of strategic preventive measures, and infrastructures. This review reappraises the impacts and effectiveness of the current live-attenuated oral rotavirus vaccines from many representative countries of the globe. It examines the problems associated with the low efficacy of these vaccines and the way forward. Lastly, forefront efforts put forward to develop initial procedures for oral rotavirus vaccines were examined and re-connected to today vaccines.

Distribution of rotavirus genotypes after vaccine introduction in the Triângulo Mineiro region of Brazil: 4-Year follow-up study

BACKGROUND

Rotaviruses are the major cause of diarrhea in children for which a monovalent G1P[8] vaccine has been provided free for all Brazilian infants since March 2006.

OBJECTIVES

To investigate prevalence and genotypes of rotavirus strains causing diarrhea in children in Triângulo Mineiro, Minas Gerais, during 2007-2010, and to assess local vaccine impact.

STUDY DESIGN

Fecal specimens were analyzed for rotavirus detection and characterization by PAGE, RT-PCR and PCR-genotyping assays.

RESULTS

Overall, rotavirus was diagnosed in 12.1% (76/630) cases, accounting for 35.8% of the hospitalizations and 6.5% of outpatient attendance due to diarrhea. A trend in rotavirus disease reduction occurred in both cities (71.8% and 83.4% in Uberaba; 95.3% in Uberlândia) up to 2009, but it reversed in 2010 with increased rotavirus cases in Uberlândia. Short pattern G2P[4] strains were detected in all but three (96%) cases of mixed/P[NT] infections with long electropherotypes.

CONCLUSIONS

This 4-year follow-up study showed a reduction in rotavirus-related diarrhea and even skipped a rotavirus season, which is consistent with vaccine mediated protection. The 2007-2010 rotavirus epidemic curve reflected the natural cyclic fluctuation of the single G2P[4] genotype, with sharp reduction of cases in 2008 leading to lack of a rotavirus 2009 season (both cases and hospitalizations) followed by its come back in 2010. Diarrhea cases related to either vaccine serotype/genotype (G1 or P[8]) were not detected. Thus, a new scenario emerged with a single epidemic genotype replacing the cocirculation of great diversity of genotypes, thus far, a hallmark of the epidemiology of rotavirus in Brazil.

Vaccines for preventing rotavirus diarrhoea: vaccines in use

BACKGROUND

Rotavirus results in higher diarrhoea-related death in children less than five years of age than any other single agent, particularly in low- and middle-income countries. The World Health Organization has recommended the use of rotavirus vaccines in childhood immunization schedules.

OBJECTIVES

To evaluate rotavirus vaccines approved for use (Rotarix, RotaTeq, and Lanzhou Lamb Rotavirus (LLR)) for preventing rotavirus diarrhoea.

SEARCH STRATEGY

In February 2010, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (published in The Cochrane Library 2009, Issue 1), MEDLINE, EMBASE, LILACS, and BIOSIS. We also searched the ICTRP (January 2010) and checked reference lists of identified studies.

SELECTION CRITERIA

Randomized controlled trials comparing rotavirus vaccines approved for use with placebo, no intervention, or another vaccine in children.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility, extracted data, and assessed risk of bias. Dichotomous data were combined using the risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

Thirty-four trials that included 175,944 participants met the inclusion criteria. They evaluated Rotarix (26 trials; 99,841 participants) and RotaTeq (eight trials; 76,103 participants), and had variable risk of bias (where information provided). None of the identified trials used LLR or compared rotavirus vaccines. Compared to placebo, Rotarix and RotaTeq were both effective at reducing rotavirus diarrhoea (severe cases and cases of any severity). They also reduced all-cause diarrhoea (severe cases), and hospitalizations and need for medical attention caused by rotavirus diarrhoea. However, few data were available for Rotarix and all-cause diarrhoea. Versus the placebo groups, participants in each vaccine group had similar numbers of deaths, serious adverse events, reactogenicity profiles (fever, diarrhoea, and vomiting), and adverse events that required discontinuation of the vaccination schedule. Both vaccines were immunogenic (measured by virus shedding in stool and/or seroconversion). Subgroup analyses indicate that both vaccines are effective in countries with different incomes, but few data are available.

AUTHORS' CONCLUSIONS

Rotarix and RotaTeq are effective vaccines for the prevention of rotavirus diarrhoea. The balance between benefit and harm favours benefit. Ongoing safety monitoring should be continued. Trials comparing LLR with placebo should be conducted and the results made available.

Detection of group a human rotavirus G9 genotype circulating in Córdoba, Argentina, as early as 1980

The incidence of human rotavirus G types was determined over a 25-year period (1979-2003) by using reverse transcription-PCR (RT-PCR) to examine 519 stool specimens found to be positive for rotavirus by enzyme linked immunosorbent assay (ELISA) or polyacrylamide gel electrophoresis (PAGE). These stool samples were obtained from children under 3 years old who had been treated for acute diarrhea at public hospitals in Córdoba, Argentina. The present study describes the continued circulation of the common human G types G1 (53.8%), G2 (10.2%), G3 (4.4%), and G4 (27%), and also the detection of the unusual types G8 (0.5%) and G9 (4.2%). Genotype G9 was detected during the 1980-1988 and 1997-2003 periods at relatively low rates. Rotavirus G types distribution was independent of age (1-18 months), gender or out-patient or in-patient status. Unexpectedly, 44.6% of mixed infections were detected, involving common and unusual genotypes. Overall, 95.4% of the typed strains belonged to the most prevalent human serotypes (G1-G4) but the detection of G9 infection throughout this study period highlights the importance of this serotype as a human pathogen.

Experimental infection of non-human primates with a human rotavirus isolate

Several rotavirus candidate vaccines have been developed and are at various stages of evaluation. In order to assess the safety and efficacy of these candidate vaccines, an appropriate non-human primate model is desirable. In earlier studies, we reported the presence of naturally occurring anti-rotavirus antibodies in monkeys and demonstrated that parenteral vaccination of baboons led to production of specific rotavirus antibodies in their milk. In the present study, we assessed the possibility of developing the baboon and the vervet monkey as an animal model for rotavirus studies by inoculating them with a pathogenic human rotavirus isolate prepared from the fresh faeces obtained from a child suffering from rotavirus diarrhoea. Preliminary studies have showed excretion of rotavirus in the faeces of 5 of 5 vervets monkeys and 1 of 2 baboons, by antigen ELISA and SDS-PAGE. These results were confirmed by RT-PCR and electron microscopy. The animals also showed elevation of IgG and high titres of virus neutralising antibodies. These data indicate that baboon and vervet monkeys may be useful models for human rotavirus infection and for pre-clinical evaluation of rotavirus candidate vaccines.

Neonatal rotavirus infection in Belém, northern Brazil: nosocomial transmission of a P[6] G2 strain

A total of 614 fecal specimens were obtained during a survey for rotavirus infection conducted between May 1996 and May 1998 among 437 newborns admitted to special care nurseries at a public hospital in the urban area of Belém, Brazil. Routine stool samples were taken weekly from all babies up to the age of 28 days. Overall, 51 (11.7%) of the neonates excreted rotaviruses while in hospital, of whom 42 (82.3%) developed asymptomatic nosocomial infection; nosocomial infection was also proved in five of the nine patients with diarrhea. Three distinct RNA profiles were detected, of which one short electropherotyping pattern was far more frequent ( approximately 90% of the strains). Using monoclonal antibody-based enzyme immunoassays, 32 (62.7%) of the rotavirus-positive strains were classified as G2, and 1 (1.9%) as mixed G1 and G2. A G serotype could not be assigned to 18 (35.3%) of the isolates. A reverse transcription-polymerase chain reaction was used for determining the VP4 type-specificity of a subset of 28 rotavirus-positive samples. Characterization of the VP7-genotype specificity was also sought for 18 of these latter strains. Overall, P[6] and G2 genotypes were identified in 93% and 94% of tested samples respectively, with results being further confirmed by Southern hybridization. Although surveillance was conducted during a 25-month period, 50 (98%) of 51 rotavirus isolates clustered between January and December 1997. The earliest [P6]G2 rotavirus infections were detected by late January 1997, involving two (13- and 14-day-old) babies admitted with acute diarrhea. Thereafter, strains bearing these genotype specificities were identified among five infants with hospital-acquired gastroenteritis, followed by 16 others who were infected asymptomatically. This is the first report from Brazil describing nosocomial transmission of P[6]G2 rotavirus strains among neonates.

Emergence of G9 P[6] human rotaviruses in Argentina: phylogenetic relationships among G9 strains

Because rotavirus diarrhea can be reduced through vaccination and because current vaccine candidates provide protection against only the most common G antigenic types (G1 to G4), detection of uncommon G types is one of the main goals of rotavirus surveillance. After a 2-year nationwide rotavirus surveillance study in Argentina concluded, surveillance was continued and an increase of G9 prevalence in several Argentine cities was detected. During this period G9 strains predominated in the south, and a gradient of decreasing G9 prevalence was observed from south to north (41 to 0%). Sequence analysis of gene 9, encoding the G antigen, showed that Argentine strains cluster with most G9 isolates from other countries, showing less than 2% nucleotide divergence among them, but are distinctive from them in that they present some unique amino acid changes. Our results agree with reports of increased G9 prevalence in other parts of the world, suggesting the need to incorporate G9 into candidate rotavirus vaccines.

Immune responses and protection obtained with rotavirus VP6 DNA vaccines given by intramuscular injection

Intramuscular (i.m.) injection of murine VP6 DNA vaccines raised high titers of rotavirus-specific serum IgG and IgA antibodies in BALB/c mice. A Th1-like antibody response was generated based on the ratio of serum IgG2a to IgG1 antibodies. Rotavirus-specific serum IgA but not fecal IgA was detected in mice prior to rotavirus challenge. Partial protection against rotavirus challenge was achieved as measured by reduction of rotavirus antigen shedding in feces. A similar level of protection was found with a bovine rotavirus VP6 DNA vaccine against a murine rotavirus challenge, suggesting that heterologous protection can be obtained by immunizing with VP6 DNA vaccines. We did not directly test for cytotoxic T lymphocyte (CTL) activity, but in vivo depletion of CD8+ T cells in mice immunized with a murine VP6 DNA vaccine did not significantly change the duration of virus shedding or the pattern of protection obtained. This finding suggested that CD8+ CTL activity was not essential for the partial protection we obtained by i.m. immunization of mice with VP6 DNA vaccines.

Immune responses and protection obtained by oral immunization with rotavirus VP4 and VP7 DNA vaccines encapsulated in microparticles

Protective immune responses in mice were obtained after oral immunization with rotavirus DNA vaccines encapsulated in poly(lactide-co-glycolide) (PLG) microparticles. The DNA vaccines used encoded outer capsid proteins VP4 and VP7; proteins that are the basis for rotavirus serotyping and the generation of virus neutralizing antibodies. One dose of vaccine was given to BALB/c mice by oral gavage (75 microg DNA/mouse). Rotavirus-specific serum antibodies and intestinal IgA antibodies were detectable by 6 weeks postimmunization. After challenge with homologous murine rotavirus at 12 weeks postimmunization, fecal rotavirus antigen was reduced significantly in immunized mice compared with controls. Protective immunity also was generated by oral delivery of unencapsulated VP 7 DNA vaccine but to a lesser degree. These results demonstrate that the oral route is effective for generating protective immune responses with rotavirus DNA vaccines targeting neutralization antigens.

Bacterial expression of the major antigenic regions of porcine rotavirus VP7 induces a neutralizing immune response in mice

The outer capsid protein of rotavirus, VP7, is a major neutralization antigen. A chimeric protein comprising Escherichia coli (E. coli) outer membrane protein A (OmpA) and part of porcine rotavirus VP7 containing all three antigenic regions (217 amino acids) was expressed in Salmonella and E. coli as an outer-membrane associated protein. Mice immunized intraperitoneally or orally, respectively, with live E. coli or Salmonella cells expressing this chimeric protein produced antibodies against native VP7 as determined by enzyme-linked immunosorbent assays and neutralization tests. This indicates that the VP7 fragment from a porcine rotavirus which is antigenically similar to human rotavirus serotype 3, when expressed in bacteria as a chimeric protein, can form a structure resembling its native form at least in some of the major neutralization domains. These results indicate that the use of a live bacterial vector expressing rotavirus VP7 may represent a strategy for the development of vaccines against rotavirus-induced diarrhoea in infants.

Acute gastroenteritis

Acute gastroenteritis represents a frequent cause of morbidity and mortality among children in the developing world as well as morbidity in the developed world. Despite the large number of potential etiologic agents, management of gastroenteritis is uniform and aimed to prevent the two major complications, dehydration and malnutrition. Current guidelines emphasize the use of oral rehydration and the early reintroduction of age-appropriate foods. These guidelines are reviewed here, the underlying principles discussed, and practical points provided.

Protective immunity induced by oral immunization with a rotavirus DNA vaccine encapsulated in microparticles

DNA vaccines are usually given by intramuscular injection or by gene gun delivery of DNA-coated particles into the epidermis. Induction of mucosal immunity by targeting DNA vaccines to mucosal surfaces may offer advantages, and an oral vaccine could be effective for controlling infections of the gut mucosa. In a murine model, we obtained protective immune responses after oral immunization with a rotavirus VP6 DNA vaccine encapsulated in poly(lactide-coglycolide) (PLG) microparticles. One dose of vaccine given to BALB/c mice elicited both rotavirus-specific serum antibodies and intestinal immunoglobulin A (IgA). After challenge at 12 weeks postimmunization with homologous rotavirus, fecal rotavirus antigen was significantly reduced compared with controls. Earlier and higher fecal rotavirus-specific IgA responses were noted during the peak period of viral shedding, suggesting that protection was due to specific mucosal immune responses. The results that we obtained with PLG-encapsulated rotavirus VP6 DNA are the first to demonstrate protection against an infectious agent elicited after oral administration of a DNA vaccine.

Lack of maternal antibodies to P serotypes may predispose neonates to infections with unusual rotavirus strains

Rotavirus (RV) strains infecting newborns often have unique neutralization antigens (P serotypes) on their outer capsids that are distinct from those found on RV strains that cause diarrhea in older children. We examined the hypothesis that unusual RV strains preferentially infect newborns because the newborns lack maternal neutralizing antibodies to these strains. To test this hypothesis, sera and saliva samples collected from neonates infected with 116E-like (P[11]G9) strains in the maternity ward of the All India Institute of Medical Sciences (AIIMS) hospital in New Delhi were tested for neutralizing antibodies against common RV strains and those infecting newborns and these titers were compared with those of newborns who did not become infected (controls). The infected neonates had significantly lower levels of cord blood neutralizing antibodies to 116E than the controls, suggesting that immunity to neonatal RV infection is acquired transplacentally through maternal antibodies. Further, this study confirmed the immunogenicity of the AIIMS neonatal strain 116E, a vaccine candidate, in its ability to evoke a potent RV-specific immunoglobulin A and neutralizing antibody response in serum and saliva among the infected babies. Our findings have important implications for the development of an effective RV vaccine. In India, where G9 strains are common in the community, the use of 116E as a vaccine, together with the rhesus tetravalent vaccine, may provide a broader protection against all the circulating RV serotypes, including serotype G9, which is not represented in the current rhesus RV tetravalent vaccine (G1-G4).

Immune response to three doses of quadrivalent rotavirus vaccine: 1-year follow-up

Twenty-eight children who received three doses of the quadrivalent rotavirus vaccine with 4 x 10(5) plaque-forming units (p.f.u.) were followed during a year after vaccination. Serum samples were obtained and evaluated for rotavirus IgA and neutralizing antibodies against vaccine and human rotavirus strains. At the end of the study, up to 61% of the children showed an increase in circulating IgA antibody levels. Nearly all of the vaccinated children increased their neutralizing antibody titres against the vaccine strains, and 25-54% against human rotavirus serotypes. After comparing the vaccinees with a population of children naturally infected with serotype G1 in the same study area, we conclude that three doses of 4 x 10(5) p.f.u. of the quadrivalent vaccine should prepare the child against future severe rotavirus diarrhea.

Sequence analysis demonstrates that VP6, NSP1 and NSP4 genes of Indian neonatal rotavirus strain 116E are of human origin

We have sequenced the genes encoding the inner capsid protein VP6 and the nonstructural proteins NSP1 and NSP4 of the Indian neonatal serotype P8[11]G9 human/bovine reassortant candidate vaccine rotavirus strain 116E. These three genes share a high degree of sequence and deduced amino acid homology with human prototype strain Wa. Our results confirm and extend those of previous RNA-RNA hybridization studies which suggested that these genes are of human origin, and will facilitate examination of the host immune response to 116E induced by natural infection and vaccination.

Phase 1 trial of a candidate rotavirus vaccine (RV3) derived from a human neonate

OBJECTIVE

To conduct a phase 1 safety and tolerability trial of an oral rotavirus vaccine candidate RV3 in healthy volunteers.

METHODOLOGY

Double blind placebo controlled trial of a single 1 mL oral dose (6.5 x 10(5) fluorescing focus units [FFU]/mL) in 10 healthy young men, 10 3-4 year old children and 10 3 month old infants with a 4 week surveillance period. The study was undertaken at a children's hospital and nearby community in Melbourne, Australia.

RESULTS

All subjects successfully completed the trial. There were no significant side-effects attributable to the vaccine preparation in any age group. No shedding of vaccine virus was detected by enzyme immunoassay. There was evidence of an immune response in serum and/or gut secretions in two of five vaccinees in each age group.

CONCLUSION

RV3 rotavirus vaccine appears to be safe and well tolerated. Evidence of immunogenicity in some subjects after a single dose encourages further trials to determine immunogenicity after three doses, after reduction of viral dose, and without prior administration of buffer.

Periplasmic expression of part of the major rotavirus capsid protein VP7 containing all the three antigenic regions in Escherichia coli

Part of the porcine rotavirus outer capsid protein VP7 containing all the three antigenic regions was expressed as a chimeric protein with bacterial alkaline phosphatase (AP) in E. coli. The construct contains an ompF promoter, the DNA encoding the signal sequence and the first 12 amino acids of mature OmpF, part of vp7 and the DNA encoding mature AP. The chimeric protein is stable, retains the biological property of AP and ability to react with polyclonal antiserum against the virus, and can be exported through the bacterial inner membrane into the periplasm.

G3P2 rotaviruses causing diarrhoeal disease in neonates differ in VP4, VP7 and NSP4 sequence from G3P2 strains causing asymptomatic neonatal infection

During longitudinal epidemiological studies of rotavirus infections in children in Melbourne, Australia human G3P2 rotavirus strains causing asymptomatic or symptomatic infections have been identified. Eleven strains (AS strains) associated with asymptomatic infection of newborn babies from 1974-1984, and five strains (S strains) associated with symptomatic infection of newborn babies (4) or a 22 week old infant (1) during 1980-1986 were studied. The entire nucleotide sequences of genes coding for VP4, VP7, NSP4 and VP6 were derived for representative AS and S strains. The nucleotide sequences of neutralization epitope regions present on the outer capsid proteins VP4 and VP7 (regions C and F) showed extensive conservation of nucleotide and deduced amino acid sequence in all strains. Minor variations were observed over the 12 year period in VP7 epitope regions A and B in some strains. Specific conserved amino acids differences between the asymptomatic and symptomatic strains were observed in the genes encoding VP4 at aa133 and 303 (asparagine or threonine) and 380 (serine or isoleucine), VP7 at aa27 (threonine or isoleucine), aa29 (isoleucine or threonine), aa42 (valine or alanine) and aa238 (asparagine or aspartic acid/serine) and NSP4 at aa135 (isoleucine or valine). No amino acid changes were identified in gene 6. The observed amino acid differences occurred in proteins that have been implicated in virulence, and correlate with differences in clinical symptoms of infants infected with these strains. These results permit speculation about the genetic basis for virulence of human strains.

DNA vaccines against rotavirus infections

Plasmid DNA vaccines encoding for murine rotaviral proteins VP4, VP6, and VP7 were tested in adult BALB/c mice for their ability to induce immune responses and provide protection against rotavirus challenge. Serum antibodies were measured by virus neutralization and by ELISA. Cellular immunity was assessed by measuring cytotoxic T cell (CTL) responses. The vaccines were administered by inoculation into cells of the epidermis with an Accell gene gun (Auragen, Inc., Middleton, WI, USA). Each of the three vaccines elicited rotavirus-specific serum antibodies as measured by ELISA. Virus neutralizing antibodies were detected in mice receiving DNA vaccines encoding for VP4 and VP7, but not in those which received the plasmid encoding for VP6. Vaccines encoding for VP4, VP6, or VP7 generated virus-specific CTL responses in recipient mice. Efficacy of the vaccines was determined by challenge with homotypic rotaviruses. Each of the three vaccines was effective in protecting mice against infection after rotavirus (100 ID50) challenge. Significant reductions (p < 0.0002, analysis of variance) in viral excretion measured over a 9 day period were seen in mice receiving the DNA vaccines compared with mice that received control plasmids.

Titration of human-bovine rotavirus reassortants using a tetrazolium-based colorimetric end-point dilution assay

A colorimetric end-point dilution assay was developed for the titration of rotavirus-containing samples that uses commercially available tetrazolium dyes as an indicator of virus infection. This assay offers several advantages over both plaque assays and traditional end-point dilution methods. The latter assays require manual counting of plaques or the scoring of wells for the presence of virus based on observed cytopathic effects. The colorimetric end-point dilution assay enables the scoring of wells based upon absorbance readings alone, thereby eliminating time-consuming and subjective manual screenings. This method also has the potential for automating the analysis of large numbers of samples. Virus titers of human-bovine rotavirus reassortants obtained using this method are comparable to those determined by plaque assay. The scoring of wells based on absorbance readings was also found to agree with manual scoring of cytopathic effects and with the production of viral antigen.

Heterogeneity of VP4 neutralization epitopes among serotype P1A human rotavirus strains

We have used serotype-specific VP4 and VP7 neutralizing monoclonal antibodies (Nt-MAbs), as well as subgroup (SG)-specific MAbs, to characterize by enzyme immunoassay rotavirus strains isolated from diarrheic infants in the city of Monterrey, Mexico, from July 1993 to March 1994. Of a total of 465 children studied, 140 were rotavirus positive, including 3 patients infected with non-group A rotaviruses. The SG and VP7 (G) serotype specificities could be determined for 118 (84%) of the 140 rotavirus-positive stool specimens; 4 rotavirus strains were serotype G1 and SGII; 1 strain was serotype G2 and SGI+II; 112 strains were serotype G3 and SGII; 1 strain was serotype G3 and SGI; and none of the strains was serotype G4. Fifty-eight specimens, representing the 13 different group A rotavirus electropherotypes detected, were chosen for VP4 (P) serotyping. Of these, 48 (83%) strains reacted with the P1A serotype-specific Nt-MAb 1A10. None of the strains reacted with the serotype P2-specific Nt-MAbs tested. Not all viruses that reacted with Nt-MAb 1A10 were recognized by Nt-MAbs 2A3 and 2G1, which also recognize P1A strains, indicating heterogeneity of neutralization epitopes among serotype P1A human rotaviruses. This heterogeneity could be relevant for the specificity of the VP4-mediated neutralizing antibody immune response and indicates the need for antigenic characterization, in addition to genomic typing, of the VP4 proteins of circulating human rotavirus field strains.

Comparison of mucosal and systemic humoral immune responses and subsequent protection in mice orally inoculated with a homologous or a heterologous rotavirus

Rotaviruses are the single most important cause of severe diarrhea in young children worldwide, and vaccination is probably the most effective way to control the disease. Most current live virus vaccine candidates are based on the host range-restricted attenuation of heterologous animal rotaviruses in humans. The protective efficacy of these vaccine candidates has been variable. To better understand the nature of the heterologous rotavirus-induced active immune response, we compared the differences in the mucosal and systemic immune responses generated by heterologous (nonmurine) and homologous (murine) rotaviruses as well as the ability of these infections to produce subsequent protective immunity in a mouse model. Sucking mice were orally inoculated with a heterologous simian or bovine rotavirus (strain RRV or NCDV) or a homologous murine rotavirus (wild-type or tissue culture-adapted) strain EHP at various doses. Six weeks later, mice were challenged with a virulent murine rotavirus (wild-type strain ECW) and the shedding of viral antigen in feces was quantitated. Levels of rotavirus-specific serum immunoglobulin G (IgG) and fecal IgA prior to challenge were measured and correlated with subsequent viral shedding or protection. Heterologous rotavirus-induced active protection was highly dependent on the strain and dose of the virus tested. Mice inoculated with a high dose (10(7) PFU per mouse) of RRV were completely protected, while the protection was diminished in animals inoculated with NCDV or lower doses of RRV. The ability of a heterologous rotavirus to stimulate a detectable intestinal IgA response correlated with the ability of the virus to generate protective immunity. Serum IgG titer did not correlate with protection. Homologous rotavirus infection, on the other hand, was much more efficient at inducing both mucosal and systemic immune responses as well as protection regardless of the virulence of the virus strain or the size of the immunizing dose.

Survey of rotavirus G and P types associated with human gastroenteritis in São Paulo, Brazil, from 1986 to 1992

Rotavirus strains causing gastroenteritis in Brazilian children were characterized by PCR-based typing assays. In addition to strains bearing the major human G and P types, large numbers of strains bearing P3 (M37-like), P6 (HCR3-like), untypeable P and G types, and complex mixtures of P and G types not previously recognized were present in the community.

Rotavirus and other viral causes of gastroenteritis

Diarrheal diseases are a major cause of childhood morbidity and mortality worldwide. Viruses are the leading cause of diarrhea, and rotavirus is the major cause of severe dehydrating diarrhea in both developed and developing countries. Children with viral gastroenteritis generally present with watery non-bloody diarrhea, often with vomiting and low grade fever. Disease is self-limited and treatment is simple--fluid and electrolyte replacement, preferably via the oral route, with early refeeding. While various adjunctive therapies, such as bismuth subsalicylate and oral immunoglobulins, appear promising, they cannot be routinely recommended at this time. Prevention is the key: by good personal hygiene--particularly good handwashing, by maintaining safe water supplies, and in the future, by an effective rotavirus vaccine.

The rotavirus genus

Human rotaviruses, discovered nearly 20 years ago, have been proven to be major cause of paediatric diarrhoeal disease morbidity and mortality. The clinical significance of these viruses stimulated basic studies on their biology, molecular and antigenic properties and epidemiology. General features, clinical relevance, epidemiologic pattern and laboratory diagnosis of human rotavirus infections are here reviewed.

Diarrhoeal disease: current concepts and future challenges. Diarrhoeal disease and vaccine development

Vaccination against diarrhoeal disease offers many opportunities to reduce significantly disease burden and childhood mortality from preventable disease world-wide. Regrettably, vaccine development has become an issue more of the development of the ultimate vaccine rather than the provision of a useful public health tool. The delay in implementing the delivery of vaccines with only 50% protective efficacy while awaiting the development of single dose vaccines that will provide lifelong immunity in more than 90% of recipients has resulted in no vaccine becoming available to those people who need it. Any alleviation of the disease burden would be of considerable benefit in an endemic region, to both the people and the governments, while researchers continue pursuing the ideal vaccine. The issues are discussed in this paper.