Serological and molecular characterization of human rota viruses causing gastroenteritis in infants and young children in Kenya

Abstract

Rotavirus is known to be the most common cause of severe infantile diarrhea worldwide. Severe rotavirus disease may be preventable by vaccination. This study focused on serological and molecular characterization of rotavirus positive strains from infants and young children presenting with gastroenteritis at three hospitals in Kenya. Two hundred and eighty five virus strains were examined for RNA genome diversity by a classical method, polyacrylamide gel electrophoresis of the double stranded RNA and visualized by silver staining. The rotavirus strains were further characterized by monoclonal antibodies directed to the inner capsid, VP6 subgroup antigen. The VP7 serotype was characterized by the use of a nested PCR method using a cocktail of primers specific to the six human VP7 serotypes (GI,G2,G3,G4,G8,G9). Furthermore, the VP4 genotype was characterized by the use of a nested PCR method using a cocktail of primers specific for the five human VP4 genotypes (P4, P6, P8, P9 & P10). It was possible to determine the electropherotypes in 214 (75%) of the samples. 1551214 (72.4%) showed the long pattern and 56 (26.2%) the short pattern. Additionally three samples (1.4%) were showing a possibility of mixed infections, of both long and short patterns. Five long electropherotype patterns and five short patterns were observed. Subgroup 11 viruses occurred more commonly than subgroup I viruses (69% vs 29%). It was also found that 2% of the samples were expressing both subgroup I and 11 antigens. It was shown that the "long" electropherotype is associated with subgroup II and the "short" electropherotype with subgroup I. Interestingly a single strain of long electropherotype had subgroup I antigens. It was demonstrated that VP7 serotype GI predominated (22%), followed by G2 (9%), then G8 (8%), and then G3 and G4 (1%) in each case. No G9 serotypes were identified. Furthermore 2% of strains with dual serotype (Gl/G3 & GI/G2) were identified by the RT-PCR typing method. A large number of strains (57%) could not be typed to determine the serotype. The common VP4 genotypes P8 (22%) and P4 (14%) were identified, as well as the genotype P6 (9%), which has classically been associated with asymptomatic neonatal strains. Furthermore 2% of the strains were identified to have dual genotype (P8/P4 & P8/P6). A large number of strains (53%) could not be typed to determine the genotype. The combination of VP7 serotype and VP4 genotype demonstrated that GIP[8] strains predominated (52%), followed by G2P[4] (18%), then G8P[4] (12%) and G8P[6] (12%). The least identified were GIP[6] (3%) and G3P[8] (3%), in each case. This study has characterized the human rotavirus strains from Kenya by antigenic and genomic analysis. It has also contributed much needed epidemiological data of rotavirus infection in Africa. The results of this study show an emergence of serotype G8 as an important serotype in Kenya and suggesting that future human rotavirus vaccines will need to protect against disease caused by this serotype.