Emergence of rotavirus G4P8 strain among children suffering from watery diarrhea in Calcutta, India.

Rotavirus RNAs from the fecal samples were hybridized with cDNAs specific for G1 and G2 genotypes. 59 out of 138 samples (42.7%) did not hybridize with either probe. The cDNAs coding for VP7 and VP4 from one such sample, SC134, were synthesized by combined reverse transcriptase/polymerase chain reaction (PCR) using specific oligonucleotide primers and were used as probes to screen those local isolates which did not hybridize with either G1 or G2. 26/59 (44%) of fecal RNA hybridized with these cDNAs indicating a possible emergence of this strain in this part of India. The VP7 and VP4 genotype specificity of SC134 was found to be G4P8 by multiplex PCR. The VP7 gene of SC134 was cloned and characterized in detail by restriction enzyme digestion and DNA sequence analysis. Comparison of nucleotide and predicted amino acid sequence of the VP7 gene of SC134 with other serotypes revealed that the VP7 gene of SC134 was closely related to G4. However, amio acids within the VP7 sequence differed in seven positions with that of both the subtype 'A' and 'B' of the G4 serotype. To establish the relation of this emerging strain with the other reported G4 strains, a phylogenetic tree was constructed and SC134 was found to be more closely related to the ST3 strain isolated in England and included in the tetravalent vaccine formulation along with two Japanese strains, although all four were distinct and did not form any cluster as was evident by the horizontal distance separating them. The VP7 gene sequence of SC134 was submitted to EMBL and was assigned the accession number AJ278217.