Recombination analysis based on the HAstV-2 and HAstV-4 complete genomes

Complete genome sequences of previously unstudied human astrovirus subgenotypes - HAstV-2a and HAstV-2c - and two isolates of a rare genotype HAstV-4 have been determined. These isolates were recovered from fecal samples of young children hospitalized with acute intestinal infections in Novosibirsk (Russia). Three of the four sequenced isolates (HAstV-2a, HAstV-2c, and HAstV-4) are recombinants. It has been shown that all known HAstV-2 genomes have emerged via recombination; the HAstV-1 and HAstV-4 genotypes contain both recombinant and non-recombinant isolates; and all HAstV-3, HAstV-5, and HAstV-6 whole-genome sequences display no reliable signs of recombination. The average mutation accumulation rate has been determined based on an extended ORF2 fragment and amounts to 1.0 × 10−3 substitutions per site per year. The evolutionary chronology of current HAstV genotypes has been reconstructed.