The detection and molecular characterization of human G12 genotypes in South Africa

Circulating Rotavirus Genotypes among Children Younger than 5 Years with Acute Gastroenteritis in Zaria, Northwestern Nigeria

Objective This study aimed to determine the circulating rotavirus genotypes among children 0 to 59 months with acute gastroenteritis in Zaria, Northwestern Nigeria.

Methods A cross-sectional hospital-based study was performed from November 2015 to April 2017 on 415 stool samples of children 0 to 59 months with acute gastroenteritis presenting at the pediatric clinics in five selected health care facilities in Zaria, Northwestern Nigeria. The stool samples were tested for group A rotavirus antigen by enzyme-linked immunosorbent assay (ELISA) using the ProSpecT™ Rotavirus Microplate Assay (Thermo Scientific Oxoid, United Kingdom). Rotavirus-positive strains were further characterized using seminested multiplex reverse transcriptase polymerase chain reaction.

Results Of the 415 diarrheal stool samples collected from children with acute gastroenteritis, 12.3% (n = 51) tested positive by ELISA. Five rotavirus G genotypes (G1, G2, G3, G9, and G12) and three P genotypes (P[4], P[6], and P[8]) were detected. Eight genotype combinations were detected with G1P[8], G12P[8], and G3P[6] being the most prevalent (9.8% each) followed by G1P[6], G2P[4], and G9P[8] (5.9% each). G/P mix types representing 25.5% (n = 13) of strains were detected during the study period.

Conclusion This study found a high diversity of rotavirus strains with emerging unusual rotavirus genotypes and a concurrent high proportion of mixed infections. This increased antigenic diversity of rotavirus strains may impact on vaccine effectiveness and rotavirus epidemiology and highlights the importance of continuous surveillance.

Genetic characterization of G12P[6] and G12P[8] rotavirus strains collected in six African countries between 2010 and 2014

BACKGROUND

G12 rotaviruses were first observed in sub-Saharan Africa in 2004 and since then have continued to emerge and spread across the continent and are reported as a significant human rotavirus genotype in several African countries, both prior to and after rotavirus vaccine introduction. This study investigated the genetic variability of 15 G12 rotavirus strains associated with either P[6] or P[8] identified between 2010 and 2014 from Ethiopia, Kenya, Rwanda, Tanzania, Togo and Zambia.

METHODS

The investigation was carried out by comparing partial VP7 and partial VP4 sequences of the African G12P[6] and G12P[8] strains with the available GenBank sequences and exploring the recognized neutralization epitopes of these strains. Additionally, Bayesian evolutionary analysis was carried out using Markov Chain Monte Carlo (MCMC) implemented in BEAST to estimate the time to the most recent ancestor and evolutionary rate for these G12 rotavirus strains.

RESULTS

The findings suggested that the VP7 and VP4 nucleotide and amino acid sequences of the G12 strains circulating in African countries are closely related, irrespective of country of origin and year of detection, with the exception of the Ethiopian strains that clustered distinctly. Neutralization epitope analysis revealed that rotavirus VP4 P[8] genes associated with G12 had amino acid sequences similar to those reported globally including the vaccine strains in RotaTeq and Rotarix. The estimated evolutionary rate of the G12 strains was 1.016 × 10^- 3 substitutions/site/year and was comparable to what has been previously reported. Three sub-clusters formed within the current circulating lineage III shows the diversification of G12 from three independent ancestries within a similar time frame in the late 1990s.

CONCLUSIONS

At present it appears to be unlikely that widespread vaccine use has driven the molecular evolution and sustainability of G12 strains in Africa. Continuous monitoring of rotavirus genotypes is recommended to assess the long-term impact of rotavirus vaccination on the dynamic nature of rotavirus evolution on the continent.

Whole Genome Analysis of African G12P[6] and G12P[8] Rotaviruses Provides Evidence of Porcine-Human Reassortment at NSP2, NSP3, and NSP4

Group A rotaviruses (RVA) represent the most common cause of pediatric gastroenteritis in children <5 years, worldwide. There has been an increase in global detection and reported cases of acute gastroenteritis caused by RVA genotype G12 strains, particularly in Africa. This study sought to characterize the genomic relationship between African G12 strains and determine the possible origin of these strains. Whole genome sequencing of 34 RVA G12P[6] and G12P[8] strains detected from the continent including southern (South Africa, Zambia, Zimbabwe), eastern (Ethiopia, Uganda), central (Cameroon), and western (Togo) African regions, were sequenced using the Ion Torrent PGM method. The majority of the strains possessed a Wa-like backbone with consensus genotype constellation of G12-P[6]/P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1, while a single strain from Ethiopia displayed a DS-1-like genetic constellation of G12-P[6]-I2-R2-C2-M2-A2-N2-T2-E2-H2. In addition, three Ethiopian and one South African strains exhibited a genotype 2 reassortment of the NSP3 gene, with genetic constellation of G12-P[8]-I1-R1-C1-M1-A1-N1-T2-E1-H1. Overall, 10 gene segments (VP1–VP4, VP6, and NSP1–NSP5) of African G12 strains were determined to be genetically related to cognate gene sequences from globally circulating human Wa-like G12, G9, and G1 strains with nucleotide (amino acid) identities in the range of 94.1–99.9% (96.5–100%), 88.5–98.5% (93–99.1%), and 89.8–99.0% (88.7–100%), respectively. Phylogenetic analysis showed that the Ethiopian G12P[6] possessing a DS-1-like backbone consistently clustered with G2P[4] strains from Senegal and G3P[6] from Ethiopia with the VP1, VP2, VP6, and NSP1–NSP4 genes. Notably, the NSP2, NSP3, and NSP4 of most of the study strains exhibited the closest relationship with porcine strains suggesting the occurrence of reassortment between human and porcine strains. Our results add to the understanding of potential roles that interspecies transmission play in generating human rotavirus diversity through reassortment events and provide insights into the evolutionary dynamics of G12 strains spreading across selected sub-Saharan Africa regions.

Emergence of G12 and G9 rotavirus genotypes in the Central African Republic, January 2014 to February 2016

Objectives

Rotavirus gastroenteritis is a major cause of death among children under 5 years globally. A rotavirus gastroenteritis surveillance program started in October 2011 in the Central African Republic (CAR) with the Surveillance Epidémiologique en Afrique Centrale (SURVAC) project. We present here genotyping results showing the emergence of G9 and G12 genotypes in Central African Republic.

Results

Among 222 children hospitalized with acute gastroenteritis who had a stool sample collected at the sentinel site, Complexe Pédiatrique de Bangui (CPB), Bangui, Central African Republic, 100 (45%) were positive for rotavirus between January 2014 and February 2016. During this period the most common rotavirus strains were G1P[8] (37%), G12P[6] (27%) and G9P[8] (18%).

Group A rotaviruses circulating prior to a national immunization programme in Nigeria: Clinical manifestations, high G12P[8] frequency, intra-genotypic divergence of VP4 and VP7

Nigeria having approximately 50 000 Rotavirus A (RVA) deaths annually is yet to introduce RVA vaccine into routine national immunization; therefore surveillance of RVA strains circulating before vaccine introduction is essential in evaluating impact of the intervention. Stool samples and sociodemographic data of diarrhoeic children, <5 years were collected between August 2012 and December 2013. While a high prevalence of RVA infection (47.6%; 49/103) was observed by quantitative reverse transcription real time PCR, only 25% (26/103) had high RVA genome concentrations and were antigen positive. G and P types were obtained for 31 and 37 samples respectively. G12P[8] strains were predominant (30.6%; 16/31); Other genotypes found included G9, G3, G2 and P[4], P[6], P[8]. A G12 + G2/P[8] + P[6] mixed infection was detected. The P[8] genotype showed divergence with strains distributed in lineage III and IV. Compared to the vaccines, changes in antigenic sites of VP8* and VP7 were found. The finding of the G2P[6] genotype combination and emergence of G12 strains support observations in most of the recent RVA studies from Africa. P[6] is common in many African countries, in contrast to countries in Europe and the Americas. In conclusion, this study shows the circulation of other RVA genotypes compared to the common RVA genotypes in Nigeria. PCR results should be interpreted with caution to avoid significant bias from samples with low RVA genome concentrations. These findings provide important information on the detection and molecular epidemiology of RVA prior to vaccination and contribute as a baseline for future evaluations after possible vaccine introduction.

Prevalence and genetic diversity of rotavirus infection in children with acute gastroenteritis in a hospital setting, Nairobi Kenya in post vaccination era: a cross-sectional study

Introduction

Rotavirus is the leading cause of severe diarrhoea among infants and young children. Each year more than 611 000 children die from rotavirus gastroenteritis, and two million are hospitalized, worldwide. In Kenya, the impact of recent rotavirus vaccinations on morbidities has not been estimated. The study aimed at determining the prevalence and identity of rotavirus strains isolated from rotavirus-associated diarrhoea in vaccinated children presenting with acute gastroenteritis.

Methods

Two hundred and ninety eight specimen from children presented at Gertrude Childrens’ Hospital from January to June 2012 were tested by EIA (Enzyme-linked Immunosorbent Assay) for rotavirus antigens. Molecular characterization was conducted on rotavirus-positive specimens. Extracted viral RNA was separated by polyacrylamide gel electrophoresis (PAGE) and the specific rotavirus VP4 (P-types) and VP7 (G-types) determined.

Results

The prevalence rate of rotavirus was 31.5% (94/298). Of the rotavirus dsRNA, 57 (60.1%) gave visible RNA profiles, 38 (40.4%) assigned long electropherotypes while 19 (20.2%) were short electropherotypes. The strains among the vaccinated were G3P [4], G12P [6], G3P [6], G9P [4], G mixed G9/3P [4] and G1/3P [4]. Specifically, the G genotypes were G9/3 (5.3%), G9 (4.3%), G3 (4.3%), G12 (2.1%) and mixed G1/3 (1.1%). The P genotypes detected were P [4] (5.3%) and P [6] (5.3%).

Conclusion

The present study demonstrates diversity in circulating genotypes with emergence of genotypes G3, G9, G12 and mixed genotypes G9/3 and recommends that vaccines should be formulated with a broad range of strains to include G9 and G12.

Distribution of rotavirus VP7 and VP4 genotypes circulating in Tunisia from 2009 to 2014: Emergence of the genotype G12

Group A rotavirus (RVA) represents the most important aetiological agent of diarrhoea in children worldwide. From January 2009 to December 2014, a multi-centre study realized through 11 Tunisian cities was undertaken among children aged <5 years consulting or hospitalized for acute gastroenteritis. A total of 1127 faecal samples were collected. All samples were screened by ELISA for the presence of RVA antigen. RVA-positive samples were further analyzed by PAGE and used for G/P-genotyping by semi-nested multiplex RT-PCR. Globally, 270 specimens (24 %) were RVA-positive, with peaks observed annually between November and March. Nine different electropherotypes could be visualized by PAGE, six with a long profile (173 cases) and two with a short one (seven cases). Mixed profiles were detected in two cases. Among the 267 VP7 genotyped strains, the predominant G- genotype was G1 (39.6 %) followed by G3 (22.2 %), G4 (13 %), G9 (11.5 %), G2 (5.2 %) and G12 (5.2 %). Among the 260 VP4 genotyped strains, P[8] genotype was the predominant (74.5 %) followed by P[6] (10.4 %) and P[4] (5.5 %). A total of 257 strains (95.2 %) could be successfully G- and P-genotyped. G1P[8] was the most prevalent combination (34.4 %), followed by G3P[8] (16.3 %), G9P[8] (10.3 %), G4P[8] (8.9 %), G2P[4] (4 %), G12P[6] (2.6 %) and G12P[8] (1.9 %). Uncommon G/Pgenotype combinations, mixed infections and untypeable strains were also detected. This is the first report, in Tunisia, of multiple detection of an emerging human RVA strain, G12 genotype. This study highlighted the need for maintaining active surveillance of emerging strains in Northern Africa.

ROTAVIRUS GENOTYPES CIRCULATING IN BRAZIL, 2007-2012: IMPLICATIONS FOR THE VACCINE PROGRAM

Regarding public health in Brazil, a new scenario emerged with the establishment of universal rotavirus (RV) vaccination programs. Herein, the data from the five years of surveillance (2007-2012) of G- and P-type RV strains isolated from individuals with acute gastroenteritis in Brazil are reported. A total of 6,196 fecal specimens were investigated by ELISA and RT-PCR. RVs were detected in 19.1% (1,181/6,196). The peak of RV incidence moved from June-August to September. RV was detected less frequently (19.5%) among children ≤ 5 years than in older children and adolescents (6-18 years) (40.6%). Genotype distribution showed a different profile for each year: G2P[4] strains were most prevalent during 2007-2010, G9P[8] in 2011, and G12P[8] in 2012. Mixed infections (G1+G2P[4], G2+G3P[4]+P[8], G2+G12P[8]), unusual combinations (G1P[4], G2P[6]), and rare strains (G3P[3]) were also identified throughout the study period. Widespread vaccination may alter the RV seasonal pattern. The finding of RV disease affecting older children and adolescents after vaccine implementation has been reported worldwide. G2P[4] emergence most likely follows a global trend seemingly unrelated to vaccination, and G12, apparently, is emerging in the Brazilian population. The rapidly changing RV genotype patterns detected during this study illustrate a dynamic population of co-circulating wildtype RVs in Brazil.

Epidemiology of rotavirus A diarrhea in Chókwè, Southern Mozambique, from February to September, 2011

Acute diarrhea disease caused by Rotaviruses A (RVA) is still the leading cause of morbidity and mortality in children ≤5 years old in developing countries. An exploratory cross-sectional study was conducted between February and September, 2011 to determine the proportion of acute diarrhea caused by RVA. A total of 254 stool specimens were collected from children ≤5 years old with acute diarrhea, including outpatients (222 children) and inpatients (32 children), in three local health centers in Chókwè District, Gaza Province, South of Mozambique. RVA antigens were detected using enzyme immunoassay (EIA); the RVA G (VP7) and P (VP4) genotypes were determined by RT-PCR or analysis sequencing. Sixty (24%) out of 254 fecal specimens were positive for RVA by EIA; being 58 (97%) from children ≤2 years of age. RVA prevalence peaks in June and July (coldest and drier months) and the G[P] binary combination observed were G12P[8] (57%); G1P[8] (9%); G12P[6] (6%); and 2% for each of the following genotypes: G1P[6], G2P[6] G4P[6], and G9P[8]. Non-Typeable (NT) G and/or P genotypes were observed as follows: G12P [NT] (6%); G1P [NT], G3P[NT] and GNTP[NT] (4%). Considering the different GP combinations, G12 represented 67% of the genotypes. This is the first data showing the diversity of RVA genotypes in Mozambique highlighting the epidemiological importance of these viruses in acute diarrhea cases in children ≤2 years old. In addition, these findings will provide a baseline data before the introduction of the RVA monovalent (Rotarix(®) ) vaccine in the National Immunization Program in September 2015. J. Med. Virol. 88:1751-1758, 2016. © 2016 Wiley Periodicals, Inc.

Rotavirus surveillance in urban and rural areas of Niger, April 2010-March 2012

Knowledge of rotavirus epidemiology is necessary to make informed decisions about vaccine introduction and to evaluate vaccine impact. During April 2010–March 2012, rotavirus surveillance was conducted among 9,745 children <5 years of age in 14 hospitals/health centers in Niger, where rotavirus vaccine has not been introduced. Study participants had acute watery diarrhea and moderate to severe dehydration, and 20% of the children were enrolled in a nutrition program. Of the 9,745 children, 30.6% were rotavirus positive. Genotyping of a subset of positive samples showed a variety of genotypes during the first year, although G2P[4] predominated. G12 genotypes, including G12P[8], which has emerged as a predominant strain in western Africa, represented >80% of isolates during the second year. Hospitalization and death rates and severe dehydration among rotavirus case-patients did not differ during the 2 years. The emergence of G12P[8] warrants close attention to the characteristics of associated epidemics and possible prevention measures.

Molecular surveillance of rotavirus strains circulating in Yaoundé, Cameroon, September 2007-December 2012

Rotavirus is the most common cause of severe diarrheal disease in children under 5 years of age worldwide. The World Health Organization (WHO) estimated that 453,000 rotavirus-attributable deaths occur annually. Through the WHO, the Rotavirus Sentinel Surveillance Program was established in Cameroon in September 2007 with the Mother and Child Center (MCC) in Yaoundé playing the role of sentinel site and national laboratory for this program. The objectives of this surveillance were to assess the rotavirus disease burden and collect baseline information on rotavirus strains circulating in Cameroon. Diarrheal stool samples were collected in a pediatric hospital from children under 5, using the WHO case definition for rotavirus diarrhea. Antigen detection of rotavirus was performed by using an enzyme immunoassay (EIA). The genotypic characterization was performed using multiplexed semi-nested reverse transcription-polymerase chain reaction (RT-PCR) assays. Between September 2007 and December 2012, 2444 stool samples were received at the MCC laboratory for rotavirus antigen detection, of which 999 (41%) were EIA positive. Among EIA positive samples 898 were genotyped. Genotype prevalence varied each year. Genotype G9P[8] was the dominant type during 2007 (32%) and 2008 (24%), genotype G3P[6] predominated in 2010 (36%) and 2011 (25%), and G1P[8] was predominant in 2012 (44%). The findings showed that the rotavirus disease burden is high and there is a broad range of rotavirus strains circulating in Yaoundé. These data will help measure the impact of vaccination in the future.

Molecular surveillance of rotavirus infection in Bangui, Central African Republic, October 2011-September 2013

BACKGROUND

The World Health Organization (WHO) recommends the introduction of rotavirus vaccine in the immunization program of all countries. In the Central African Republic (CAR), sentinel surveillance for rotavirus gastroenteritis was established in 2011 by the Ministry of Health, with the support of the Surveillance en Afrique Centrale Project (SURVAC). The purpose of this study was to assess the burden of rotavirus gastroenteritis and to identify rotavirus strains circulating in CAR before the introduction of rotavirus vaccine planned for this year, 2014.

METHODS

One sentinel site and one laboratory at the national level were designated by the CAR Ministry of Health to participate in this surveillance system. Stool samples were collected from children who met the WHO rotavirus gastroenteritis case definition (WHO, 2006). The samples were first screened for group A rotavirus antigen by enzyme immunoassay (EIA), and genotyping assays performed using a multiplex reverse transcriptase PCR (RT-PCR) technique.

RESULTS

Between October 2011 and September 2013, 438 stool samples were collected and analyzed for detection of rotavirus antigen; 206 (47%) were positive. Among the 160 (78%) that could be genotyped, G2P[6] was the predominant strain (47%) followed by G1P[8] (25%) and G2P[4] (13%).

CONCLUSIONS

Almost half of stool samples obtained from children hospitalized with gastroenteritis were positive for rotavirus. These baseline rotavirus surveillance data will be useful to health authorities considering rotavirus vaccine introduction and for evaluating the efficacy of rotavirus vaccine once it is introduced into the routine immunization system.

Whole genomic analysis of human G12P[6] and G12P[8] rotavirus strains that have emerged in Kenya: identification of porcine-like NSP4 genes

G12 rotaviruses are globally emerging rotavirus strains causing severe childhood diarrhea. However, the whole genomes of only a few G12 strains have been fully sequenced and analyzed, of which only one G12P[4] and one G12P[6] are from Africa. In this study, we sequenced and characterized the complete genomes of three G12 strains (RVA/Human-tc/KEN/KDH633/2010/G12P[6], RVA/Human-tc/KEN/KDH651/2010/G12P[8], and RVA/Human-tc/KEN/KDH684/2010/G12P[6]) identified in three stool specimens from children with acute diarrhea in Kenya, Africa. On whole genomic analysis, all three Kenyan G12 strains were found to have a Wa-like genetic backbone: G12-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1 (strains KDH633 and KDH684) and G12-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 (strain KDH651). Phylogenetic analysis showed that most genes of the three strains examined in this study were genetically related to globally circulating human G1, G9, and G12 strains. Of note is that the NSP4 genes of strains KDH633 and KDH684 appeared to be of porcine origin, suggesting the occurrence of reassortment between human and porcine strains. Furthermore, strains KDH633 and KDH684 were very closely related to each other in all the 11 gene segments, indicating derivation of the two strains from a common origin. On the other hand, strain KDH651 consistently formed distinct clusters of 10 of the 11 gene segments (VP1-2, VP4, VP6-7, and NSP1-5), indicating a distinct origin of strain KDH651 from that of strains KDH633 and KDH684. To our knowledge, this is the first report on whole genome-based characterization of G12 strains that have emerged in Kenya. Our observations will provide important insights into the evolutionary dynamics of emerging G12 rotaviruses in Africa.

Genetic diversity of circulating rotavirus strains in Tanzania prior to the introduction of vaccination

Background

Tanzania currently rolls out vaccination against rotavirus-diarrhea, a major cause of child illness and death. As the vaccine covers a limited number of rotavirus variants, this study describes the molecular epidemiology of rotavirus among children under two years in Dar es Salaam, Tanzania, prior to implementation of vaccination.

Methods

Stool specimens, demographic and clinical information, were collected from 690 children admitted to hospital due to diarrhea (cases) and 545 children without diarrhea (controls) during one year. Controls were inpatient or children attending child health clinics. Rotavirus antigen was detected using ELISA and positive samples were typed by multiplex semi-nested PCR and sequencing.

Results

The prevalence of rotavirus was higher in cases (32.5%) than in controls (7.7%, P<0.001). The most common G genotypes were G1 followed by G8, G12, and G4 in cases and G1, G12 and G8 in controls. The Tanzanian G1 variants displayed 94% similarity with the Rotarix vaccine G1 variant. The commonest P genotypes were P[8], P[4] and P[6], and the commonest G/P combination G1 P[8] (n = 123), G8 P[4] and G12 P[6]. Overall, rotavirus prevalence was higher in cool (23.9%) than hot months (17.1%) of the year (P = 0.012). We also observed significant seasonal variation of G genotypes. Rotavirus was most frequently found in the age group of four to six months. The prevalence of rotavirus in cases was lower in stunted children (28.9%) than in non-stunted children (40.1%, P = 0.003) and lower in HIV-infected (15.4%, 4/26) than in HIV-uninfected children (55.3%, 42/76, P<0.001).

Conclusion

This pre-vaccination study shows predominance of genotype G1 in Tanzania, which is phylogenetically distantly related to the vaccine strains. We confirm the emergence of genotype G8 and G12. Rotavirus infection and circulating genotypes showed seasonal variation. This study also suggests that rotavirus may not be an opportunistic pathogen in children infected with HIV.

Rotavirus G and P types circulating in the eastern region of Kenya: predominance of G9 and emergence of G12 genotypes

BACKGROUND

The World Health Organization has recommended that rotavirus (RV) vaccines be included in all national immunization programs as part of a strategy to control RV-associated diarrheal diseases. Hospital-based surveillance of RV infection is therefore crucial in monitoring the impact pre- and post-vaccine introduction and also to document changes in genotype distribution. This study sought to determine the RV genotypes circulating in the eastern region of Kenya before introduction of the RV vaccine.

METHODS

During September 2009 to August 2011, 500 stool samples were collected from children <5 years of age admitted for acute diarrhea in hospitals in the eastern region of Kenya and analyzed for the presence of group A RV using an enzyme immunoassay. G and P genotypes were determined using hemi-nested reverse transcriptase polymerase chain reaction.

RESULTS

One hundred and eighty nine out of 500 (38%) samples analyzed were positive for rotavirus. The following G types were detected: G9 (50.9%), G1 (26.8%), G8 (12.1%), G12 (3.1%), G2 (0.6%), mixed G (1.3%) and 5.1% were G nontypeable. P types detected included: P[8] (63.7%), P[4] (12.1%), P[6] (4.5%), mixed P (7.6%) and 12.1% were P nontypeable. The most dominant strain was G9P[8] (35%), followed by G1P[8] (26.8%), G8P[4] (9.6%), G12P[6] (2.5%), G9P[6] (1.9%), G9P[4] (1.3%), G8P[8] (1.3%), and G2P[4] (0.6%).

CONCLUSIONS

The present study demonstrates the recurring changing genotypes of RV circulating in Kenya, with genotypes G9, G1 and G8 being the dominant strains circulating in the eastern region of Kenya between 2009 and 2011. Additionally, G12 genotype was detected for the first time in Kenya.

Update of rotavirus strains circulating in Africa from 2007 through 2011

BACKGROUND

The African Rotavirus Surveillance Network has been detecting and documenting rotavirus genotypes in the subcontinent since 1998, largely based on intercountry workshops conducted at Rotavirus Regional Reference Laboratories. This article reports on rotavirus genotypes generated at Regional Reference Laboratories, South Africa between 2007 and 2011 from 16 African countries.

METHODS

Stool samples were collected from <5-year-old children with diarrhea following World Health Organization criteria of hospital-based rotavirus surveillance. Enzyme immunoassay (EIA) was performed by National Laboratories. Regional Reference Laboratories retested 10% of randomly selected EIA positives and 10% of EIA negatives from each country as part of quality control. At least 50 rotavirus EIA positives from each country per year were subjected to reverse transcriptase polymerase chain reaction based on G-/P-types. Sequencing was conducted in 5-10% of each representative G or P genotype to confirm the genotype, as well as to type some of the samples that could not be genotyped with reverse transcriptase polymerase chain reaction-based methods.

RESULTS

A total of 2555 of rotavirus EIA positives were genotyped. G1 was the most predominant (28.8%), followed by G9 (17.3%), G2 (16.8%), G8 (8.2%), G12 (6.2%) and G3 (5.9%). Similarly, the P[8] strain was the most prevalent (40.6%), followed by P[6] (30.9%) and P[4] (13.9%). The top G/P combinations detected were G1P[8] (18.4%), G9P[8] (11.7%), G2P[4] (8.6%), G2P[6] (6.2%), G1P[6] (4.9%), G3P[6] (4.3%), G8P[6] (3.8%) and G12P[8] (3.1%).

CONCLUSIONS

There is high genetic diversity of rotavirus strains circulating in the subcontinent. Understanding the strain diversity pre- and postvaccine introduction are important in Africa to understand the broader impact of the rotavirus vaccines on regionally circulating strains.

Rotavirus vaccination within the South African Expanded Programme on Immunisation

Diarrhoeal diseases are ranked the third major cause of childhood mortality in South African children less than 5 years, where the majority of deaths are among black children. Acute severe dehydrating rotavirus diarrhoea remains an important contributor towards childhood mortality and morbidity and has been well documented in South Africa. As the preventive strategy to control rotavirus diarrhoea, South Africa became the first country in the WHO African Region to adopt the rotavirus vaccine in the national childhood immunisation programme in August 2009. The rotavirus vaccine in use, Rotarix, GSK Biologicals, is given at 6 and 14 weeks of age, along with other vaccines as part of Expanded Programme on Immunisation (EPI). Studies which facilitated the introduction of rotavirus vaccine in South Africa included the burden of rotavirus disease and strain surveillance, economic burden of rotavirus infection and clinical trials to assess the safety and efficacy of vaccine candidates. This paper reviews the epidemiology of rotavirus in South Africa, outlines some of the steps followed to introduce rotavirus vaccine in the EPI, and highlights the early positive impact of vaccination in reducing the rotavirus burden of disease based on the post-marketing surveillance studies at Dr George Mukhari hospital, a sentinel site at University of Limpopo teaching hospital in Pretoria, South Africa, which has conducted rotavirus surveillance for >20 years.

Molecular epidemiology of rotavirus and norovirus in Ile-Ife, Nigeria: high prevalence of G12P[8] rotavirus strains and detection of a rare norovirus genotype

Rotavirus (RV) and norovirus (NoV) are considered the most common causes of viral gastroenteritis in children. In this study, the prevalence of RV and NoV infection in 55 children with diarrhea from the rural community Akinlalu in Southwestern Nigeria was investigated using real-time PCR assays. The RV and NoV strains were genotyped by PCR and/or sequencing. RV and NoV infections occurred with a prevalence of 34.5% and 25.5% respectively, with predominance in children <1 year. Most infections occurred during the dry season with increasing prevalence of RV as the dry season progressed (October-January). Infections with RV VP6 subgroup (SG) II were more prevalent (27.3%) than SGI (7.3%). Similarly, NoV genogroup II infections were more common (23.6%) than genogroup I (1.8%). Five children out of 55 (9.1%) were co-infected with both RV and NoV. Notably, G12P[8] was the predominant RV strain (36.8%, n = 7), observed for the first time in Nigeria. The VP7 gene of the G12 strains clustered within lineage III, sharing high nucleotide identity with each other (>99%) indicating introduction in Nigeria from a single donor. Furthermore, a putative novel genotype within genogroup I NoV was detected, which till date has only been reported once in humans. To conclude, a high prevalence of the emerging G12P[8] RV strain was observed for the first time in Nigeria, as well as a putative novel NoV genotype in humans. These results provide new information which can be important for future vaccine evaluations and possible introduction in Nigeria.

Human rotavirus vaccine Rotarix™ provides protection against diverse circulating rotavirus strains in African infants: a randomized controlled trial

BACKGROUND

Rotaviruses are the most important cause of severe acute gastroenteritis worldwide in children <5 years of age. The human, G1P[8] rotavirus vaccine Rotarix™ significantly reduced severe rotavirus gastroenteritis episodes in a Phase III clinical trial conducted in infants in South Africa and Malawi. This paper examines rotavirus vaccine efficacy in preventing severe rotavirus gastroenteritis, during infancy, caused by the various G and P rotavirus types encountered during the first rotavirus-season.

METHODS

Healthy infants aged 5-10 weeks were enrolled and randomized into three groups to receive either two (10 and 14 weeks) or three doses of Rotarix™ (together forming the pooled Rotarix™ group) or three doses of placebo at a 6,10,14-week schedule. Weekly home visits were conducted to identify gastroenteritis episodes. Rotaviruses were detected by ELISA and genotyped by RT-PCR and nucleotide sequencing. The percentage of infants with severe rotavirus gastroenteritis caused by the circulating G and P types from 2 weeks post-last dose until one year of age and the corresponding vaccine efficacy was calculated with 95% CI.

RESULTS

Overall, 4939 infants were vaccinated and 4417 (pooled Rotarix™ = 2974; placebo = 1443) were included in the per protocol efficacy cohort. G1 wild-type was detected in 23 (1.6%) severe rotavirus gastroenteritis episodes from the placebo group. This was followed in order of detection by G12 (15 [1%] in placebo) and G8 types (15 [1%] in placebo). Vaccine efficacy against G1 wild-type, G12 and G8 types were 64.1% (95% CI: 29.9%; 82%), 51.5% (95% CI:-6.5%; 77.9%) and 64.4% (95% CI: 17.1%; 85.2%), respectively. Genotype P[8] was the predominant circulating P type and was detected in 38 (2.6%) severe rotavirus gastroenteritis cases in placebo group. The remaining circulating P types comprised of P[4] (20 [1.4%] in placebo) and P[6] (13 [0.9%] in placebo). Vaccine efficacy against P[8] was 59.1% (95% CI: 32.8%; 75.3%), P[4] was 70.9% (95% CI: 37.5%; 87.0%) and P[6] was 55.2% (95% CI: -6.5%; 81.3%)

CONCLUSIONS

Rotarix™ vaccine demonstrated efficacy against severe gastroenteritis caused by diverse circulating rotavirus types. These data add to a growing body of evidence supporting heterotypic protection provided by Rotarix™.

TRIAL REGISTRATION NUMBER

NCT00241644.

A first report on the characterization of rotavirus strains in Sierra Leone

In an effort to reduce the high mortalities associated with rotavirus infections, a number of African countries are considering introducing human rotavirus vaccines. The demonstrated safety and efficacy of the live-attenuate human rotavirus vaccines in several clinical trials worldwide has accelerated such initiatives. Although the percentage-mortality rates for Sierra Leone are top of the list for rotavirus-associated deaths in Africa, no study has reported the prevalent strains circulating within this country. In this study, stool specimens were collected from 128 Sierra Leonean children presenting with diarrhea in 2005. Almost 37.5% (48/128) were rotavirus positive by EIA, of which 89.6% (43/48) revealed a short electropherotype, and a further 6.98% (3/48) could not be assigned a PAGE pattern. Genotyping analysis revealed G2P[4] (30.23%), G2P[6] (13.95%), G8P[6] (11.63%), G2P[8] (4.65%), G8P[4] (4.65%), and G8P[8] (2%) strains. About 11% were only assigned VP7 genotypes (G2), while 20.9% had mixed G and P types. The frequent detection of G2 rotaviruses could be of concern considering data generated from some studies that suggests lower efficacy of Rotarix® vaccine against G2 rotaviruses. This underscores the need for extensive and continuous regional strain surveillance to support rotavirus vaccines introduction and guide future vaccine development efforts. Such information will be useful before considering administration of specific rotavirus vaccine candidates in countries like Sierra Leone where little is known about circulating rotavirus strains.

The detection of enteric viruses in selected urban and rural river water and sewage in Kenya, with special reference to rotaviruses

AIM

To determine the occurrence of eight human enteric viruses in surface water and sewage samples from different geographical areas in Kenya.

METHODS AND RESULTS

Enteric viruses were recovered from the water and sewage sources by glass-wool adsorption elution and/or polyethylene glycol/NaCl precipitation and detected by singleplex real-time and conventional PCR and reverse transcriptase-PCR assays. One or more enteric viruses were detected in nearly all sewage and river water samples except the urban Mbagathi River. The VP7 (G types) and the VP4 (P types) of the rotaviruses (RV) were characterized by multiplex nested PCR methods. The G and P types could be determined in 95·5% of the RV strains, respectively. Mixed G types were detected with G12 and G1 predominating, and unusual G types, G5 and G10, were present. P[4] predominated in the urban Karen sewage samples, while P[8] predominated in the urban and rural streams.

CONCLUSIONS

The high prevalence of RVs in surface water highlights the importance of assessing the water sources used for domestic purposes for viral contamination.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrates the benefit of environmental surveillance as an additional tool to determine the epidemiology of RVs and other enteric viruses circulating in a given community.

Molecular characterization of rare G12P[6] rotavirus isolates closely related to G12 strains from the United States, CAU 195 and CAU 214

Two human G12 rotaviruses, CAU 195 and CAU 214, were isolated from South Korea using cell culture and characterized on the basis of sequence divergence in the VP7, VP4, and NSP4 genes. Phylogenetic analysis of the VP7 gene sequences indicated that these strains clustered into lineage III and were most closely related to G12 rotaviruses isolated in the United States. The VP4 and NSP4 gene sequences showed that two strains belonged to the P[6]-Ia lineage and genotype [B]. This finding provides information that can be used to evaluate G12 strains and aid in the development of effective vaccines in the future.

Effect of human rotavirus vaccine on severe diarrhea in African infants

BACKGROUND

Rotavirus is the most common cause of severe gastroenteritis among young children worldwide. Data are needed to assess the efficacy of the rotavirus vaccine in African children.

METHODS

We conducted a randomized, placebo-controlled, multicenter trial in South Africa (3166 infants; 64.1% of the total) and Malawi (1773 infants; 35.9% of the total) to evaluate the efficacy of a live, oral rotavirus vaccine in preventing severe rotavirus gastroenteritis. Healthy infants were randomly assigned in a 1:1:1 ratio to receive two doses of vaccine (in addition to one dose of placebo) or three doses of vaccine--the pooled vaccine group--or three doses of placebo at 6, 10, and 14 weeks of age. Episodes of gastroenteritis caused by wild-type rotavirus during the first year of life were assessed through active follow-up surveillance and were graded with the use of the Vesikari scale.

RESULTS

A total of 4939 infants were enrolled and randomly assigned to one of the three groups; 1647 infants received two doses of the vaccine, 1651 infants received three doses of the vaccine, and 1641 received placebo. Of the 4417 infants included in the per-protocol efficacy analysis, severe rotavirus gastroenteritis occurred in 4.9% of the infants in the placebo group and in 1.9% of those in the pooled vaccine group (vaccine efficacy, 61.2%; 95% confidence interval, 44.0 to 73.2). Vaccine efficacy was lower in Malawi than in South Africa (49.4% vs. 76.9%); however, the number of episodes of severe rotavirus gastroenteritis that were prevented was greater in Malawi than in South Africa (6.7 vs. 4.2 cases prevented per 100 infants vaccinated per year). Efficacy against all-cause severe gastroenteritis was 30.2%. At least one serious adverse event was reported in 9.7% of the infants in the pooled vaccine group and in 11.5% of the infants in the placebo group.

CONCLUSIONS

Human rotavirus vaccine significantly reduced the incidence of severe rotavirus gastroenteritis among African infants during the first year of life. (ClinicalTrials.gov number, NCT00241644.)

Rotavirus vaccines for the developing world

PURPOSE OF REVIEW

The authors discuss the most relevant information in the field of rotavirus vaccines published from October 2007 to June 2009; new information on the virus, host response and disease burden that relate to our understanding of vaccine mechanisms and impact are discussed. The review will focus on the role of the vaccines for the developing world but this does not preclude the relevance of these vaccines for children living in the industrialized world.

RECENT FINDINGS

Immune mechanisms involved in rotavirus-associated immunity potentially relevant for vaccine-associated immunity continue to be identified including anti-NSP4 antibodies, cellular and mucosal mechanisms. Rotavirus-associated disease burden is high, causing approximately 40% of diarrhea-associated hospitalizations in children less than 5 years of age worldwide; G12, G8 and P[6] antigenic types emerging in developing countries are increasing in prevalence and may share worldwide circulation with the other five more common serotypes. The two currently available vaccines, based on different immune concepts, (VP7/VP4 homotypic specificity for RotaTeq vs. homotypic and heterotypic specificity for Rotarix) have demonstrated high and sustained efficacy in middle and high-income countries. Recent efficacy and effectiveness studies demonstrate acceptable protection levels in the poorest countries of the world against most antigenic types, leading to universal vaccine recommendation. Postlicensure surveillance has not detected any signal of increased risk for intussusception in children vaccinated with any of the two vaccines.

SUMMARY

Rotavirus vaccines are well tolerated and provide adequate protection against moderate to severe disease in high, middle and low-income regions. Partnerships between governments, industry, and funding agencies will now be urgently needed to promote vaccine use, especially in the less privileged countries of the world.