Relative frequency of human rotavirus VP4 (P) genotypes recovered over a ten-year period from South African children with diarrhea

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.

Climatic Factors in Relation to Diarrhoea Hospital Admissions in Rural Limpopo, South Africa

Diarrheal disease is one of the leading causes of morbidity and mortality globally, particularly in children under 5 years of age. Factors related to diarrheal disease incidence include infection, malnutrition, and exposure to contaminated water and food. Climate factors also contribute to diarrheal disease. We aimed to explore the relationship between temperature, precipitation and diarrhoea case counts of hospital admissions among vulnerable communities living in a rural setting in South Africa. We applied ‘contour analysis’ to visually examine simultaneous observations in frequencies of anomalously high and low diarrhoea case counts occurring in a season, and assigning colours to differences that were statistically significant based on chi-squared test results. Children under 5 years of age were especially vulnerable to diarrhoea during very dry, hot conditions as well as when conditions were wetter than usual. We saw an anomalously higher number of diarrhoea cases during ‘warmer than usual’ conditions in the dry winter season, with average winter temperatures in Limpopo being from about 5 to 10 °C. As for ‘wetter than usual’ conditions, we saw an anomalously higher number of diarrhoea cases during ‘drier than usual’ conditions for the winter and spring. The lagged association seen in cumulative rainfall could not be distinguished in the same way for temperature-related variables (indicating rainfall had a larger impact on higher cases of diarrhoea), nor for the older age group of 5 years and older. Dry conditions were associated with diarrhoea in children under 5 years of age; such conditions may lead to increased water storage, raising the risks of water contamination. Reduced use of water for personal hygiene and cleaning of outdoor pit latrines also affect sanitation quality. Rural communities require adequate and uninterrupted water provision, and healthcare providers should raise awareness about potential diarrhoeal risks, especially during the dry season as well as during wintertime when conditions are warmer than usual.

A Rotavirus Vaccine for Infants: The Asian Experience

Introduction: Severe rotavirus gastroenteritis in children causes significant morbidity world- wide and substantial deaths in developing countries. Hence, a live attenuated vaccine Rotarix™ was developed with human strain RIX4414 of G1P1A P[8] specificity. RIX4414 trials in infants have begun in developed and developing countries worldwide. An overview of RIX4414 in developed and developing countries and prospects with this vaccine in Asia are presented. Methods: Completed RIX4414 trials have been reviewed. Results: Two oral doses of RIX4414 were well tolerated with a reactogenicity profile similar to placebo. RIX4414 was also highly immunogenic, e.g., in a dose-ranging study conducted in Singapore, 98.8% to100% of infants had a vaccine take after 2 doses. RIX4414 did not affect the immune response of simultaneously administered routine infant vaccines. RIX4414 significantly reduced severe rotavirus gastroen- teritis in settings where multiple serotypes including the emerging G9 type co-circulated. Conclusion: These encouraging results warrant further evaluation of the vaccine worldwide and especially in developing countries with the highest need. Therefore, evaluation of the Rotarix™ vaccine is continuing in large phase III trials in Asia and worldwide. Key words: Asia, Attenuated, Developing countries, Gastroenteritis, RIX4414

Global distribution of rotavirus serotypes/genotypes and its implication for the development and implementation of an effective rotavirus vaccine

A safe and effective rotavirus vaccine is urgently needed, particularly in developing countries. Critical to vaccine development and implementation is a knowledge base concerning the epidemiology of rotavirus G and P serotypes/genotypes throughout the world. The temporal and geographical distribution of human rotavirus G and P types was reviewed by analysing a total of 45571 strains collected globally from 124 studies reported from 52 countries on five continents published between 1989 and 2004. Four common G types (G1, G2, G3 and G4) in conjunction with P[8] or P[4] represented over 88% of the strains analysed worldwide. In addition, serotype G9 viruses associated with P[8] or P[6] were shown to have emerged as the fourth globally important G type with the relative frequency of 4.1%. When the global G and/or P type distributions were divided into five continents/subcontinents, several characteristic features emerged. For example, the P[8]G1 represented over 70% of rotavirus infections in North America, Europe and Australia, but only about 30% of the infections in South America and Asia, and 23% in Africa. In addition, in Africa (i) the relative frequency of G8 was as high as that of the globally common G3 or G4, (ii) P[6] represented almost one-third of all P types identified and (iii) 27% of the infections were associated with rotavirus strains bearing unusual combinations such as P[6]G8 or P[4]G8. Furthermore, in South America, uncommon G5 virus appeared to increase its epidemiological importance among children with diarrhea. Such findings have (i) confirmed the importance of continued active rotavirus strain surveillance in a variety of geographical settings and (ii) provided important considerations for the development and implementation of an effective rotavirus vaccine (e.g. a geographical P-G type adjustment in the formulation of next generation multivalent vaccines).

Human infection with a P[14], G3 lapine rotavirus

Group A rotaviruses are the main cause of severe diarrhoea in humans and animals throughout the world. We report the first description of a clinically apparent infection with a P[14], G3 rotavirus (strain B4106) in a hospitalized 6-year-old child. The VP7 gene of the B4106 strain had the closest sequence similarity (94% and 97% on the nucleotide and amino acid level, respectively) with strain 30/96 (P[14], G3), a lapine rotavirus isolated in an Italian rabbit in 1996 while the VP4 gene had the closest similarity with strain 30/96 on the nucleotide level (96%), and with lapine strains C-11 (P[14], G3) and Alabama (P[14], G3), isolated in the United States in the 1980s on the amino acid level (99%). The host restriction determinant gene NSP4 of B4106 was also most similar to lapine strain Alabama (95% nt identity and 97% aa identity). Phylogenetic analysis showed that the VP4, VP7, and NSP4 genes of the B4106 strain share a common evolutionary lineage with those of lapine rotavirus strains. We therefore hypothesize that a lapine rotavirus was able to cross the host species barrier and caused disease in a new host. The increasing detection of strains in humans that were previously believed to be restricted to animals raises questions whether interspecies transmission of rotaviruses is a common event in nature.

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.

Detection and characterization of rotavirus G and P types from children participating in a rotavirus vaccine trial in Belém, Brazil

This study sought the characterization of rotaviruses in a trial with a tetravalent rhesus-human rotavirus vaccine in Belém, Brazil in children who received three doses of vaccine or placebo in the 1st, 3rd and 5th months of life. Rotavirus electropherotypes, subgroups, G serotypes, G, [P] and [P], G genotypes were determined in 93.3%, 95.9%, 93.3%, 73.3%, 95.5% and 92.2% of isolates, respectively. Serotypes G1, G2 and G4 were detected in 58.9%, 30% and 4.4% of the cases, respectively. Rotavirus genotype G5 was detected for the first time in Northern region in 4.4% of the infections. Rotavirus genotypes P[8], P[4], P[6] and P[8 + 6] were detected in 54.5%, 26.7%, 12.2%, and 2.2% of the cases, respectively. The predominant genotypes were P[8], G1 and P[4], G2 with 53% and 26.6% of the infections, respectively. Unusual strains accounted for 20.5% including P[4], G1, P[6], G1, P[6], G4, P[6], G5, P[8], G2, P[8], G5. Mixed infections involving P[8 + 6], G2 and P[8 + 6], G1 were also noted. The neonatal P[6] strains associated with diarrhea were detected among children aged 9-24 months. To our knowledge, this study represents the first in Brazil to analyse, on molecular basis, rotavirus genotypes from children participating in a rotavirus vaccine trial. These results are of potential importance regarding future rotavirus vaccination strategies in Brazil.

Genotype profiles of rotavirus strains from children in a suburban community in Guinea-Bissau, Western Africa

The P (VP4) and G (VP7) genotypes of 167 group A rotavirus strains obtained during the period 1996 to 1998 from 149 children living in a suburban community in Guinea-Bissau, western Africa, were determined by the reverse transcription-PCR technique. A total of nine combinations including five different P types and five different G types were identified. The globally common genotype pairs P[8], G1; P[4], G2; P[8], G3 and P[8], G4 were underrepresented in this study area. We found a substantial year-to-year variation in the occurrence of the genotype combinations. In 1996 and 1997, P[6], G2 was the most frequent, whereas P[8], G1 was more common in 1998. The unusual type P[9], G3 and a few mixed infections were detected. Sixteen percent of the rotavirus-positive samples were nontypeable.

Identification of human rotavirus strains with the P[14] genotype by PCR

A seminested PCR typing assay has been extended to identify rotavirus strains with the P[14] genotype. The specificity of the method was confirmed by Southern hybridization and by restriction analysis with the enzyme AluI. One out of four human rotavirus (HRV) strains with unusual subgroup-electropherotype linkage but none out of 50 HRV strains with usual linkage was typed as P[14].

Isolation of a human rotavirus strain with a super-short RNA pattern and a new P2 subtype

Super-short rotavirus strains that have a rearranged gene segment 11 are rarely found in humans, and only five isolates, all from Southeast Asia, have been described in the literature. We report the first isolation in Japan from an infant with severe diarrhea of a rotavirus possessing a super-short RNA pattern. This strain, designated AU19, had a G1 VP7 and is also the first isolate in Japan that possesses a P2[6] VP4. Furthermore, the P2[6] VP4 carried by AU19 was divergent in the hypervariable region of the amino acid sequence from the P2A[6] VP4s carried by asymptomatic neonatal strains or from the P2B[6] VP4 carried by porcine rotavirus strain Gottfried. Thus, AU19 is likely to represent a new VP4 subtype, which we propose to call P2C. Given the recent emergence of the P2[6] VP4s in India, Brazil, and the United States and the role of VP4 in protective immunity, further scrutiny is justified to see whether the emergence of the previously underrepresented P2[6] VP4 serotype is related to this new P2 subtype.

Comparison of enzyme immunoassay, PCR, and type-specific cDNA probe techniques for identification of group A rotavirus gene 4 types (P types)

This study was designed to evaluate three techniques most commonly used to identify the VP4 (P) types of human group A fecal rotaviruses. The techniques included PCR with nested primers and hybridization with PCR-generated probes (to determine the P genotypes). The results obtained by these genetic techniques were evaluated against those obtained by an enzyme immunoassay (EIA) incorporating neutralizing monoclonal antibodies (N-MAbs) reacting with three major human P serotypes (serotypes P1A, P1B, and P2A). The P types of the rotaviruses present in 102 fecal specimens were determined under code by each of the three assays. The specificity of each assay was evaluated against a "gold standard" putative P type (P serotype and genotype) deduced from knowledge of the VP7 (G) type and the origin of the fecal specimen. Overall comparison of the results showed respective sensitivities and specificities of 92 and 92% for reverse transcription-PCR, 80 and 99% for hybridization, and 73 and 91% for EIA with N-MAbs. The hybridization assay retained high sensitivity with specimens stored for > or = 10 years. Hybridization assays with nonradioactive probes are relatively inexpensive and are suited for use in developing countries. In summary, both genetic assays showed high sensitivities and specificities in assigning a P type to human fecal rotavirus strains. Further evaluation of the EIA with N-MAbs is required, together with incorporation of new N-MAbs for the detection of the additional P types detected in developing countries.

Use of non-radioactive probes for VP4 typing of human rotaviruses

The rotavirus outer capsid proteins VP4 and VP7 determine the P- and G-serotypes, respectively, of the virus. Three types of VP4 protein are commonly found in human rotaviruses (P4, P6 and P8) which are encoded by distinct VP4 gene alleles. We developed a non-radioactive Northern hybridization method for the P-genotyping of rotavirus field isolates. Double-stranded RNA was isolated from faecal specimens of rotavirus positive patients. Digoxigenin (DIG)-labelled cDNA probes derived from the VP4 gene of the standard strains RV5 (P4), ST3 (P6) and RV4 (P8) were used to discriminate between the different alleles. Although the P4 probe exhibited cross-reactivity with some P8 samples, the P6 and P8 probes were found to be type-specific. In addition, the probes did not react with standard strains representative of other defined human and animal rotavirus P-types. Use of these probes on viral RNA of faecal origin allowed approximately 70% of samples to be assigned a P-type. This method complements PCR- and EIA-based P-typing methods, is relatively inexpensive and is readily applicable to large numbers of samples, thus proving useful for epidemiological studies.