Variability

Rotavirus populations can alter by point mutation (anti-genic drift), genome rearrangement, genome reassortment (antigenic shift), and zoonotic introduction. The rotaviral genome is replicated by an error-prone RNA-dependent RNA polymerase and there is no proofreading capacity. This results in a mutation rate of one mutation per genome replication which is of the same order of magnitude as that of influenza A virus. Sequence variation has been most studied in the genes encoding VP7 and VP4, and there is more and more evidence of divergence from the original G-types.[4] Thus G1 and P[8], which globally represent some of the most common genotypes, have drifted sufficiently to require design of new primers for RT-PCR detection.[4] For example, P[8] rotaviruses can currently be divided into three lineages (Wa-like, F45-like, and OP354-like) on the basis of deduced amino acid substitutions at 11 sites on the VP4 protein. Similar variability in NSP4 even in the toxic peptide region is common.[4] Variability in non-group A rotaviruses is less well studied, but the nucleotide sequence of segment 8 (putative NSP2) of a group B adult diarrhea rotavirus from Calcutta showed only 77% homology to that of a murine strain and 93% similarity to other human isolates.[9]

Rotavirus genome rearrangements were detected during studies of chronic infection.[4] On PAGE of serial samples of feces from immunodeficient children, RNA segments were lost or diminished in concentration and new heavier bands emerged. Sequencing the new bands indicated that there were genome rearrangements but that these did not usually result in abnormal viral proteins.

Table 5 Primers used for VP4 (P) typing

Primer

Strain

Serotype ([GT])

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

Get My Free Ebook


Post a comment