Genetic Relatedness Among Human Rotaviruses as Determined by RNA Hybridization

Abstract

Viral RNAs from human rotaviruses were compared by gel electrophoresis and by hybridization to probes prepared by in vitro transcription of two well-characterized laboratory strains (Wa and DS-1). Also, the viral RNAs were compared by hybridization to probes prepared from three of the test viruses. Thirteen specimens (diarrheal stools) were obtained from infants and children 5 to 21 months old on a single day at the emergency ward of the Caracas Children's Hospital, and an additional specimen was obtained from the same hospital 6 months before. When the electrophoresed viral RNAs were stained with ethidium bromide and examined by UV light, five different migration patterns (electropherotypes) were distinguished on the basis of differences in mobility of the RNA segments. The hybridization technique that was employed permitted only qualitative comparisons of corresponding genes of different human rotaviruses. Ten of the specimens contained enough virus to yield sufficient RNA for hybridization studies. Eight of the viruses studied by hybridization contained 4 to 11 genes that reacted specifically with the Wa probe to yield double-stranded RNA segments with a mobility similar to that of Wa viral RNA or test virus RNA. The other two viruses contained 11 genes that reacted specifically with the DS-1 hybridization probe to yield double-stranded RNA segments with a mobility similar to DS-1 viral RNA or test virus RNA. A more complex picture emerged when hybridization probes were prepared from three of the test viruses and used to compare the different electropherotypes. Corresponding genes that exhibited similar migration did not necessarily exhibit homology when studied by hybridization. Also, some corresponding genes that exhibited homology did not have the same mobility by gel electrophoresis.

Further characterisation of human rotaviruses isolated from asymptomatically infected neonates in South Africa

“…These conditions would include the uniformity of the neonate as a host, isolation and persistence of a single virus strain, the levels and mechanisms of transmission, and the acquisition of high levels of maternal antibody and would favour back mutations to the favoured consensus sequence of the virus [Flores et al, 19881. Since the rotavirus genome is segmented, it has been shown that they are able to undergo genetic reassortment at a high rate. In vivo reassortment has been demonstrated in the laboratory Midthun et al, 19871 and has been demonstrated in field studies also [Flores et al, 1982b;Nakagomi et al, 19871. It is thus likely that different genotypes representing various combinations of VP4 and VP7 will be found to exist in nature.…”

Electrophoretic typing of nosocomial rotavirus infection in a general paediatric unit showing the continual introduction of community strains

“…All strains with a short electrophoretype which were analysed further exhibited VP7 serotype 2 specificity and bore the DS-1 like VP4 gene. These results are not unusual for the epidemiology of rotavirus and reflect the concept of the two primary "families" or genogroups of rotavirus as described previously [Flores et al, 1982a;Nakagomi et al, 19891. A single specimen was identified which reacted with both VP7 serotype 1 and 2 probes and with the VP4 Wa and DS-1 probes, indicating that the child had a dual infection with rotaviruses from each of the two genogroups.…”

“…A second antigen, VP4, which also elicits the production of neutralising antibodies [Hoshino et al, 19851, has been shown to be important in the virulence properties in the rotavirus isolate [Offit et al, 19861. At least three different alleles of the VP4 gene have been shown to exist in rotaviruses recovered from chil- dren shedding rotavirus. The Wa and DS-1 alleles have been identified in rotaviruses isolated from ill children with gastroenteritis and correspond to the Wa and DS-1 "families" or genogroups of rotavirus [Flores et al, 1982a;Nakagomi et al, 19891. The Wa VP4 gene is shared by members of the Wa genogroup which include virulent members with VP7 serotype 1 , 3 and 4 specificity, while the DS-1 VP4 gene allele is present in virulent strains with VP7 serotype 2 specificity [Flores et al, 1986a;Gorziglia et al, 19881.…”

Isolation and Molecular Characterization of a Serotype 9 Human Rotavirus Strain

“…We have recently shown that human rotaviruses can be placed together in terms of their gene homology and have proposed to term such genetic classifications of rotaviruses "genogroup" (15) instead of "family" (3,4), so that the classification can conform to the taxonomic hierarchy. Thus, it was recently shown by RNA-RNA hybridization that human rotaviruses fall into any one of three distinct genogroups (13) ; i.e., the first genogroup that includes strains related to the Wa strain (serotype 1, subgroup II, long RNA electropherotype) ; the second genogroup that includes strains related to the DS-1 strain (serotype 2, subgroup I, short RNA electropherotype) ; and the third genogroup that includes strains related to the AU-1 strain (serotype 3, subgroup I, long RNA electropherotype).…”