The future of rotavirus vaccines

Issues in pediatric vaccine-preventable diseases in low- to middle-income countries

The highest burden of pediatric vaccine-preventable disease is found in developing nations where resource constraints pose the greatest challenge, impacting disease diagnosis and surveillance as well as the implementation of large scale vaccination programmes. In November 2012, a Working Group Meeting convened in Casablanca to describe and discuss the status with respect to 8 vaccine-preventable diseases (pertussis, pneumococcal disease, measles-mumps-rubella-varicella (MMRV), rotavirus and meningococcal meningitis) to identify and consider ways of overcoming obstacles to pediatric vaccine implementation. Experts from Europe, Russia, the Commonwealth of Independent States, the Middle East, Africa and South East Asia participated in the meeting. A range of region-specific needs and barriers to uptake were discussed. The aim of this article is to provide a summary of the ongoing status with respect to pediatric vaccine preventable disease in the countries represented, and the experts' opinions and recommendations with respect to pediatric vaccine implementation.

Rotavirus infection frequency and risk of celiac disease autoimmunity in early childhood: a longitudinal study

OBJECTIVE

Few studies have assessed the role of specific gastrointestinal infections in celiac disease. We investigated whether increased frequency of rotavirus infection, a common cause of gastrointestinal infection and inflammation, predicts increased risk of celiac disease autoimmunity.

METHODS

A cohort of 1,931 children from the Denver metropolitan area who carried celiac disease human leukocyte antigen (HLA) risk alleles were followed from infancy for development of celiac disease autoimmunity, defined as positivity at two or more subsequent clinic visits for tissue transglutaminase (tTG) autoantibodies measured using a radioimmunoassay with human recombinant tTG. Blood samples were obtained at ages 9, 15, and 24 months, and annually thereafter. Rotavirus antibodies were assayed using an indirect enzyme immunoassay in serial serum samples from each case and two matched controls. Frequency of infections were estimated by the number of increases (> 2 assay coefficient of variation) in rotavirus antibody between clinic visits.

RESULTS

Fifty-four cases developed celiac disease autoimmunity at a median age of 4.4 yr. Thirty-six had an intestinal biopsy, of which 27 (75%) were positive for celiac disease. Frequent rotavirus infections predicted a higher risk of celiac disease autoimmunity (compared with zero infections, rate ratio 1.94, 95% confidence interval [CI] 0.39-9.56, for one infection and rate ratio 3.76, 95% CI 0.76-18.7, for > or = 2 infections, rate ratio for trend per increase in number of infections = 1.94, 95% CI 1.04-3.61, p = 0.037). The result was similar after adjustment for gender, ethnic group, maternal education, breast-feeding, day-care attendance, number of siblings, season of birth, and number of HLA DR3-DQ2 haplotypes.

CONCLUSIONS

This prospective study provides the first indication that a high frequency of rotavirus infections may increase the risk of celiac disease autoimmunity in childhood in genetically predisposed individuals.

New viral vaccines

Vaccination is the most effective medical intervention against diseases caused by human viral pathogens. Viral vaccines prevent or modify the severity of illness in the individual and interrupt or reduce the transmission of the pathogens to other susceptible people. Through these mechanisms, vaccines against smallpox, polio, measles and hepatitis B have had an enormous impact on world health over the last 50 years. Advances in basic virology and understanding of human immunity promise more progress in the control of human viral diseases as the 21st century begins. Some important targets, including human immunodeficiency virus, respiratory syncytial virus and hepatitis C virus present challenges that require more basic research. The purpose of this review is to highlight four new viral vaccines that have recently, or will soon demonstrate the effective translation of basic investigations into clinical benefits for disease control in healthy and high-risk populations. These vaccines include the live attenuated vaccines against the RNA viruses, rotavirus and influenza A and B, and vaccines against human papilloma virus and varicella-zoster virus, which are DNA viruses that cause morbidity and mortality through their capacity to establish persistent infection. Although only the influenza vaccine has been licensed in the United States, these other new tools for disease prevention are likely to be introduced within the next few years, with profound effects on the diseases that they cause. Hence, as Virology celebrates its 50th anniversary, it is appropriate to examine these examples of recent advances in viral vaccines.

Rectal immunization with rotavirus virus-like particles induces systemic and mucosal humoral immune responses and protects mice against rotavirus infection

To evaluate whether the rectal route of immunization may be used to provide appropriate protection against enteric pathogens such as rotaviruses (RV), we studied the antibody response and the protection induced by rectal immunization of mice with RV virus-like particles (VLP). For this purpose, 6-week-old BALBc mice were rectally immunized twice with RV 8-2/6/7-VLP derived from the bovine RV RF81 strain either alone or combined with various adjuvants including four toxins [cholera toxin (CT) and three attenuated Escherichia coli-derived heat-labile toxins (LTs), LT(R192G), LT(R72), and LT(K63)] and two Toll-like receptor-targeting adjuvants (CpG and resiquimod). Six weeks after the second immunization, mice were challenged with murine RV strain ECw. RV VLP administered alone were not immunogenic and did not protect mice against RV challenge. By contrast, RV VLP combined with any of the toxin adjuvants were immunogenic (mice developed significant titers of anti-RV immunoglobulin A [IgA] in both serum and feces and of anti-RV IgG in serum) and either efficiently induced complete protection of the mice (no detectable fecal virus shedding) or, for LT(K63), reduced the amount of fecal virus shedding after RV challenge. When combined with RV VLP, CpG and resiquimod failed to achieve protection, although CpG efficiently induced an antibody response to RV. These results support the consideration of the rectal route for the development of new immunization strategies against RV infection. Rectal delivery of a VLP-based vaccine might allow the use of adjuvants less toxic than, but as efficient as, CT.

Porcine rotavirus strain Gottfried-based human rotavirus candidate vaccines: Construction and characterization

Rotavirus gastroenteritis remains the leading cause of severe diarrheal disease in infants and young children worldwide, and thus, a safe and effective rotavirus vaccine is urgently needed in both developing and developed countries. Various candidate rotavirus vaccines that were developed by us and others have been or are being evaluated in different populations in various parts of the world. We have recently confirmed that a porcine rotavirus Gottfried strain bears a P (VP4) serotype (P2B[6]) closely related to human rotavirus P serotype 2A[6] which is of epidemiologic importance in some regions of the world. Based on the modified Jennerian approach to immunization, we have constructed 11 Gottfried-based single VP7 or VP4 gene substitution reassortant vaccine candidates which could provide: (i) an attenuation phenotype of a porcine rotavirus in humans; and (ii) antigenic coverage for G serotypes 1-6 and 8-10 and P serotype 1A[8], 1B[4] and 2A[6]. In addition, following immunization of guinea pigs with Gottfried VP4, we found low but consistent levels of neutralizing antibodies to VP4 with P1A[8] or P1B[4] specificity, both of which are of global epidemiologic importance. Thus, porcine-based VP7 reassortant rotavirus vaccines may provide an advantage over rhesus- or bovine-based VP7 reassortant vaccines since the VP4s of the latter vaccines do not evoke antibodies capable of neutralizing the viruses bearing P1A[8], P1B[4] or P2A[6] VP4.

A porcine G9 rotavirus strain shares neutralization and VP7 phylogenetic sequence lineage 3 characteristics with contemporary human G9 rotavirus strains

Of five globally important VP7 (G) serotypes (G1-4 and 9) of group A rotaviruses (the single most important etiologic agents of infantile diarrhea worldwide), G9 continues to attract considerable attention because of its unique natural history. Serotype G9 rotavirus was isolated from a child with diarrhea first in the United States in 1983 and subsequently in Japan in 1985. Curiously, soon after their detection, G9 rotaviruses were not detected for about a decade in both countries and then reemerged in both countries in the mid-1990s. Unexpectedly, however, such reemerged G9 strains were distinct genetically and molecularly from those isolated in the 1980s. Thus, the origin of the reemerged G9 viruses remains an enigma. Sequence analysis has demonstrated that the G9 rotavirus VP7 gene belongs to one of at least three phylogenetic lineages: lineage 1 (strains isolated in the 1980s in the United States and Japan), lineage 2 (strains first isolated in 1986 and exclusively in India thus far), and lineage 3 (strains that emerged/reemerged in the mid-1990s). Currently, lineage 3 G9 viruses are the most frequently detected G9 strains globally. We characterized a porcine rotavirus (A2 strain) isolated in the United States that was known to belong to the P[7] genotype but had not been serotyped by neutralization. The A2 strain was found to bear serotype G9 and P9 specificities as well as NSP4 [B] and subgroup I characteristics. By VP7-specific neutralization, the porcine G9 strain was more closely related to lineage 3 viruses than to lineage 1 or 2 viruses. Furthermore, by sequence analysis, the A2 VP7 was shown to belong to lineage 3 G9. These findings raise intriguing questions regarding possible explanations for the emergence of variations among the G9 strains.

Humoral immune response to rotavirus NSP4 enterotoxin in Spanish children

The rotavirus non-structural protein 4 (NSP4) has been shown to play a crucial role in rotavirus-induced diarrhea, acting as a viral enterotoxin. It has also been demonstrated that antibody to NSP4 can reduce the severity of rotavirus-induced diarrhea in newborn mice. Two recombinant baculoviruses, expressing the NSP4 protein from the SA11 and Wa rotavirus strains, genotypes A and B, respectively, were used to produce and purify these glycoproteins, which were applied as antigen in an enzyme-linked immunosorbent assay (ELISA) to test the specific antibody response to NSP4 in human sera. Serum samples from 30 children convalescing from a rotavirus infection, from 54 healthy children under 5-years-old, and from 49 adults were tested to determine the presence of antibodies to the viral enterotoxin and to rotavirus structural proteins. Seventy percent of the sera from rotavirus-infected children showed an IgG antibody response to either one or both NSP4 proteins used in this study, although the response was weak. However, IgG antibodies towards either one or both NSP4 proteins were only detected in 26% of the non-convalescent healthy children and in only 18% of the adults. No serum IgA antibodies towards NSP4 were found in this study. IgG antibody recognition of the NSP4 protein from the SA11 and Wa rotavirus strains was not always heterotypic.

Rotavirus surveillance in the city of Rio de Janeiro-Brazil during 2000-2004: Detection of unusual strains with G8P[4] or G10P[9] specificities

Rotavirus diarrhea is a potentially life-threatening disease that affects millions of children annually around the world. Because protection against rotavirus disease is thought to be type specific, continuous rotavirus surveillance before and after implementation of a vaccine is still of essential importance. Rotavirus surveillance has been conducted in the city of Rio de Janeiro, Brazil since 1982. In the present study, we report rotavirus surveillance data in Rio de Janeiro city from 2000 to 2004. One hundred twenty nine of 1,568 (8.2%) stool samples, collected from children with acute diarrhea between January 2000 and July 2004 were rotavirus-positive. One hundred twenty eight of the 129 (99.2%) rotavirus-positive samples were genotyped for G and/or P specificity. G1 was the predominant strain (49.6%, 64/129) followed by G9 (30.2%, 39/129), and G4 (17.8%, 23/129); G2 and G3 viruses were not detected. One sample (0.8%) was non-typeable. P genotypes were determined for 124 of the 129 (96%) samples, and P[8] was the predominant genotype (90.6%, 117/129). Genotypes P[4] and P[9] were detected in two (1.6%) samples each; one (0.8%) sample presented P[6] genotype; and five (3.8%) samples were non-typeable. Two samples (1.6%) presented mixed P genotypes (P[6] + P[8]). Two unusual strains were isolated: a G8P[4] strain isolated from a non-hospitalized child with diarrhea and a G10P[9] strain isolated from a hospitalized child with diarrhea.

The VP6 protein of rotavirus interacts with a large fraction of human naive B cells via surface immunoglobulins

Immunity to human group A rotavirus (RV), a major cause of viral gastroenteritis in infants, involves B lymphocytes that provide RV-specific antibodies. Additionally, some arguments suggest that naive B cells could be implicated in the first steps of the immune response against RV. The aim of our study was to analyze the interaction of VP6 and VP7 RV capsid proteins with human B cells depending on the immune status of the individual, i.e., naive or RV experienced. For this purpose, a two-color virus-like particle flow cytometry assay was devised to evaluate the blood B-lymphocyte reactivity to VP6 and VP7 proteins from healthy RV-exposed adults, recently infected infants, and neonates at birth. Both VP6 and VP7 interactions with B cells were mediated by surface immunoglobulins and probably by their Fab portions. VP7-reactive B lymphocytes were mainly detected from RV-experienced patients and almost exclusively in the CD27-positive memory cell fraction. Conversely, VP6-reactive B lymphocytes were detected at similar and high frequencies in adult, infant, and neonate samples. In adult samples, VP6 reacted with about 2% of the CD27-negative (CD27(neg)) naive B cells. These results demonstrated that the VP6 RV protein interacted with a large fraction of naive B lymphocytes from both adults and neonates. We propose that naive B cell-VP6 interaction might influence the strength and quality of the acquired immune response and should be considered for elaborating RV vaccine strategies.

Cloning and sequence analysis of dsRNA segments 5, 6 and 7 of a novel non-group A, B, C adult rotavirus that caused an outbreak of gastroenteritis in China

A diarrhoeal outbreak among adults in China was caused by a new rotavirus, termed ADRV-N, that does not react with antisera directed against group A, B or C rotaviruses [Zhonghua Liu Xing Bing Xue Za Zhi (Chin. Epidemiol.) 19 (1998) 336]. ADRV-N can be propagated in cell cultures [Zhonghua Yi Xue Za Zhi (Natl. Med. J. China) 82 (2002) 14]. We present the complete sequences for ADRV-N genome segments 5 and 6, and a full ORF sequence of genome segment 7. The deduced amino acid sequences suggest that these segments encode NSP1, VP6 and NSP3, respectively. These three ADRV-N genome segments have a unique -ACCCC-3' terminal sequence. The 5'-GG- terminus of segments 5 and 6 is the same as that of other rotaviruses. The amino acid similarity between VP6 and NSP3 of ADRV-N and the cognate sequences of their closest counterpart, group B IDIR, was 37 and 35%, respectively. The ADRV-N NSP1 has a double-stranded RNA binding motif (DSRM) and a putative autoproteolytic cleavage motif upstream from the DSRM. The putative ADRV-N NSP3 has a truncated C-terminus compared to the cognate protein of group B rotaviruses. All the available data demonstrate that ADRV-N differs significantly from the known rotaviruses and strongly suggest that ADRV-N is the first recognized member of a new group of rotaviruses infecting humans.

Defining T-cell-mediated immune responses in rotavirus-infected juvenile rhesus macaques

The appearance of virus-specific CD4(+) and/or CD8(+) T lymphocytes in peripheral blood of captive juvenile rhesus macaques (Macaca mulatta) was observed following rotavirus infection. These cell-mediated immune responses were measured following experimental or natural infection after rotavirus was isolated from stool specimens of asymptomatic animals. The virus isolated was a new strain of simian rotavirus that we named TUCH (for Tulane University and Cincinnati Children's Hospital). Restimulation of peripheral T lymphocytes by inactivated double- or triple-layered TUCH rotavirus particles containing either VP6 or VP4 and VP7 on their respective surfaces resulted in increased quantities of interleukin-6 (IL-6) and IL-12 in cell culture supernatants. Recall responses to rotavirus by CD4(+) and CD8(+) T lymphocytes were associated with accumulation of intracellular IL-6 and gamma interferon. Antigen presentation of TUCH rotavirus to lymphocytes was mediated via differentiated cultures of monocyte-derived dendritic (HLA-DR(+)) cells. This is the first report demonstrating cell-mediated immune responses to rotavirus in nonhuman primates. Further exploration of rhesus macaques in vaccine trials with human rotavirus vaccine candidates is the major objective of future studies.

Infection and the gut

Gastrointestinal symptoms, including vomiting, are caused by a variety of infective organisms in children, many of which are self-limiting and resolve within a week, but others are potentially much more serious in their consequences. Diarrhea, vomiting and abdominal pain are common but nonspecific symptoms. Investigation is dictated by the likely causative organism, given the age and presentation of the child. The role of bacteria in the pathogenesis of necrotizing enterocolitis, recognition that Yersinia, Campylobacter and Salmonella may produce symptoms difficult to distinguish clinically from appendicitis, the viral causes of idiopathic intussusception, the occurrence of intussusception after administration of rotavirus vaccine, and the evidence incriminating mycobacterium avium subspecies paratuberculosis in the aetiology of Crohn disease are discussed.

Construction and characterization of rhesus monkey rotavirus (MMU18006)- or bovine rotavirus (UK)-based serotype G5, G8, G9 or G10 single VP7 gene substitution reassortant candidate vaccines

Group A rotaviruses are the single most important etiologic agents of severe diarrhea of infants and young children worldwide and have been estimated to be responsible for approximately 650,000-800,000 deaths annually in children <5-year-old in the developing countries. Thus, the development of a safe and effective rotavirus vaccine has been a global public health goal. Epidemiologic surveillance of rotavirus VP7 (G) serotypes-genotypes conducted in various populations throughout the world has repeatedly shown that approximately 90% of the typeable rotavirus isolates belong to G1-G4. For these reasons, we have developed a rhesus rotavirus (RRV)-based or bovine rotavirus (UK)-based quadrivalent vaccine which is designed to provide antigenic coverage for G1-G4. More recently, G serotypes-genotypes other than G1-G4, including G5, G8-G10, have been detected in various parts of the world. Although the occurrence of such uncommon G types, except for G9, has been focal, still, in order to "be ready and prepared", we have constructed and characterized eight additional reassortant rotavirus vaccines, each of which bears a single human or bovine VP7 gene encoding G serotype 5, 8, 9 or 10 specificity and the remaining 10 genes of RRV strain MMU18006 or bovine rotavirus strain UK. These candidate vaccines could be evaluated singly in special populations or in combination with a RRV- or an UK-based quadrivalent vaccine to broaden its G serotype specificity.