Rotavirus Strain Diversity in Blantyre, Malawi, from 1997 to 1999

Abstract

In a 2-year study of viral gastroenteritis in children in Blantyre, Malawi, the diversity of rotavirus strains was investigated by using electropherotyping, reverse transcription-PCR amplification of the VP7 and VP4 genes (G and P genotyping), and nucleotide sequencing. Of 414 rotavirus strains characterized, the following strain types were identified: P[8], G1 (n ‫؍‬ 111; 26.8%); P[6], G8 (n ‫؍‬ 110; 26.6%); P[8], G3 (n ‫؍‬ 93; 22.5%); P[4], G8 (n ‫؍‬ 31; 7.5%); P[8], G4 (n ‫؍‬ 21; 5.1%); P[6], G3 (n ‫؍‬ 12; 2.9%); P[6], G1 (n ‫؍‬ 7; 1.7%); P[6], G9 (n ‫؍‬ 3; 0.7%); P[6], G4 (n ‫؍‬ 3; 0.7%); P[4], G3 (n ‫؍‬ 1; 0.2%); and mixed (n ‫؍‬ 15; 3.6%). While all strains could be assigned a G type, seven strains (1.7%) remained P nontypeable. The majority of serotype G8 strains and all serotype G9 strains had short electropherotype profiles. All remaining typeable strains had long electropherotypes. Divergent serotype G1 rotaviruses, which contained multiple base substitutions in the 9T-1 primer binding site, were commonly identified in the second year of surveillance. Serotype G2 was not identified. Overall, G8 was the most frequently identified VP7 serotype (n ‫؍‬ 144; 34.8%) and P[8] was the most frequently detected VP4 genotype (n ‫؍‬ 227; 54.8%). Partial sequence analysis of the VP4 gene of genotype P[8] rotaviruses identified three distinct clusters, which predominantly (but not exclusively) comprised strains belonging to a distinct VP7 serotype (G1, G3, or G4). As a result of mutations in the 1T-1 primer binding site, strains belonging to each cluster required a separate primer for efficient typing. One cluster, represented by P[8], G4 strain OP354, was highly divergent from the established Wa and F45 VP4 P[8] lineages. As is the case for some other countries, the diversity of rotaviruses in Malawi implies that rotavirus vaccines in development will need to protect against a wider panel of serotypes than originally envisioned.In developing countries severe, dehydrating diarrhea caused by human rotavirus (HRV) results in an estimated 500,000 to 870,000 childhood deaths annually (13, 43). The routine implementation of safe and effective rotavirus vaccine programs in developing countries is expected to reduce dramatically the high level of mortality attributed to HRV, but the differing epidemiology of rotavirus in such settings may pose special challenges to successful vaccine use (6). In particular, the greater diversity of HRV strains encountered in some developing countries has implications for the formulation of rotavirus vaccines, since the original targets of these vaccines were the four most globally common HRV serotypes, G1 to G4, and some candidate vaccines were designed to provide serotypespecific (homotypic) protection (42). Thus, the first licensed vaccine, the tetravalent rhesus-human reassortant rotavirus (RRV-TV) vaccine, incorporated strains with these four mostcommon G-serotypes. The RRV-TV vaccine proved highly effective in preventing severe rotavirus diarrhea in infants and young children (3,35,49...

Molecular epidemiology of human P[8],G9 rotaviruses in Hungary between 1998 and 2001

“…Some of these may only have local significance (e.g. G5 in parts of Brazil and G8 in Malawi; Bok et al, 2001b;Cunliffe et al, 2001b), but at least one serotype, G9, was demonstrated to have dispersed worldwide (Ramachandran et al, 1996;Unicomb et al, 1999;Griffin et al, 2000;Iturriza-Gó mara et al, 2000;Palombo et al, 2000;Araú jo et al, 2001;Bok et al, 2001a;Cunliffe et al, 2001a;Bányai et al, 2004).…”

Molecular characterization of rotavirus strains detected during a clinical trial of a human rotavirus vaccine in Blantyre, Malawi

“…Such genetic diversity is recognised to be generally greater in developing countries including African countries than in industrialised countries [10,11,31]. Malawi, which has historically harboured a rich diversity of circulating rotaviruses [15,16] was selected as a site for a pivotal clinical trial of a human, monovalent G1P [8] rotavirus vaccine, Rotarix [8]. In the trial in Malawi, the diversity of circulating rotavirus strains was greater [8] than in any previously published rotavirus vaccine trial, in which the globally most common G1P [8] strain has predominated [32].…”

“…MAL23 (G1P [8]) and MAL82 (G9P [8]) belonged to lineage IV, whereas RIX4414 belonged to lineage II. The P [8] VP4 genes carried by Malawian strains reported previously belonged to lineages I, III and IV [15], and thus despite the same geographical origin, Malawi P [8] VP4 genes were noted to be highly divergent. In the P[6] VP4 phylogenetic tree there were 5 lineages (Fig.…”

“…This extensive diversity of G and P genotypes noted during the clinical trial was not exceptional since diverse rotavirus strains were known to have circulated during 10 years of surveillance in Malawi [13][14][15][16][17]. While it was reported that there was no statistically significant difference in vaccine efficacy against G1 and non-G1 genotypes in the clinical trial [8], we considered it important to examine whether the strain variation observed for the two surface protein genes extended to the other genome segments.…”

Rotavirus antigen, cytokine, and neutralising antibody profiles in sera of children with and without HIV infection in Blantyre, Malawi

“…19 We therefore, analysed 72 paired serum samples for neutralising activity against 3 human (Rotarix G1P [8], MW333 G8P [4] and WI61 G9P [8]), 1 bovine (WC3 G6P [5]) and 2 bovine-human reassortant (RotaTeq G1P [5] and G6P [8]) rotavirus strains, using MN assay ( Table 2). We found that children with natural infection developed high titres of cross-reactive neutralising activity responses against homotypic and heterotypic human strains.…”