Rotavirus VP7-gene selection during coinfections in CaCo-2 cells

A previous rotavirus epidemiological survey in Córdoba, Argentina, revealed an unusually high frequency of mixed G-type infections (41.5%). The genotype distribution of those mixed infections showed that the most prevalent G-type combinations were G1+G4 (65.0%), G1+G2 (12.5%), G2+G4 (3.1%) and G1+G9 (2.5%). In the present study we analyzed the competitive growth in CaCo-2 cell cultures of strains from the most frequent rotavirus G-type coinfections in order to explain some aspect of the dynamic of G-type replacement along the time. Our results indicated that G1-type was preferentially selected compared with G2 and G9-genotypes, meanwhile, G1–G4 coinfections showed an efficient co-amplification of both types. Interestingly, this mirrored the high detection rates of both genotypes as single and mixed infections (G1+G4, 65.0%) in our region. On the other hand, G2-type revealed a better amplification rate with respect to G4-type. Fluctuant rates in the prevalence of different genotypes usually observed along the time could, in part, be explained by successive replacement of strains with different growth characteristics. We hypothesized that one aspect of these different fitnesses can be measured as differential growth in culture of the strains contained in the sample of a mixed infection. Our findings here provide the first data supporting the validity of the competitive replication in vitro to better understand rotavirus G-type circulation patterns.