Characterization of rotavirus strains with unusual electrophoretic profiles.

Abstract

Group A rotaviruses are currently recognizedas the most important cause of acute gastroenteri-tis among both infants and young children world-wide, accounting for about one million deaths peryear in developing countries (I DeZoysa et al. 1985Bull WHO 63: 569-583, NR Blacklow & HBGreenberg 1991 N Engl J Med 325: 252-264).Rotaviruses are members of the familyReoviridae and their genome consists of 11 dis-crete segments of double-stranded (ds) RNA sur-rounded by a triple-layered shell virion (MK Estes& J Cohen 1989 Microbiol Rev 53 : 410-449). Theusual RNA electrophoretic profile of group Arotaviruses displays four different size classes con-taining RNA segments 1 to 4, 5 and 6, 7 to 9 and10 and 11. Those rotavirus strains with genomicpatterns not matching this basic configuration maybe regarded as either non-group A rotaviruses orgroup A rotaviruses with rearranged genome (EMendez et al. 1992 Arch Virol 125: 331-338). Inthis context, avian-like rotavirus strains have beenrecognized which display five segments in the firstdsRNA class (H Brussow et al. 1992 J ClinMicrobiol 30: 67-73, RHP Gusmao et al. 1994 JDiarrhoeal Dis Res 12: 129-132).Each of the 11 RNA segments codes for a singlepolypeptide, with the exception of gene 11 whichcodes for two polypeptides. Three of the virusstructural proteins (VP4, gene 4; VP6, gene 6; andVP7, genes 7, 8 or 9) induce antibodies that areused for classification of rotaviruses on serologi-cal basis (Estes & Cohen loc. cit.). VP6 forms themiddle shell of the virus and induces cross-reac-tive group- and subgroup-specific, non-neutraliz-ing antibodies. On the other hand, the two surfaceproteins VP7 and VP4 independently induce type-specific neutralizing antibodies that form the basisfor the current classification of group A rotavirusesinto G (VP7) and P (VP4) serotypes (Estes C [P8], G3;[P8], G4; and P[4], G2 (JR Gentsch et al. 1992 JClin Microbiol 30 : 1365-1373, A Steele et al. 1993J Clin Microbiol 31: 1735-1740). Rotavirus strainscharacterized as being [P8], G1and [P4], G2 seemto be the most common worldwide (BK Das et al.1994 J Clin Microbiol 32 : 1820-1822, NBG Rasoolet al. 1993 Arch Virol 133: 275-282).Although limited, the available data in Brazilconcerning the occurrence of rotavirus G and Pgenotypes indicate that the predominant strains areessentially the same as those most commonly foundworldwide. Thus, [P8], G1 and [P4], G2 accountfor more than 50% of isolates (MCS Timenetskyet al. 1994 J Clin Microbiol 32: 2622-2624, VGouvea et al. 1994 J Clin Microbiol 32 : 1408-1409,JPG Leite et al. 1996 Arch Virol 141 : 2353-2364).In these studies, the detection of mixed infectionsis an indicator that in vivo reassortments may oc-cur, as previously reported in northern Brazil (JDPMascarenhas et al. 1988 Virus Res 14: 235-240).Of interest, these investigators have shown thatrotavirus genotype [P8], G5 accounts for a signifi-