Short communicationGenetic heterogeneity and recombination in type-3 human astroviruses

- Surveillance for HAstV in Italy identified the circulation of HAstV-3.
- Sequence analysis of a 3.2 kb portion of the genome of HAstV-3 was performed.
- Genetic heterogeneity in HAstV-3: novel lineage and recombination.
- Additional epidemiological/molecular data on the HAstV-3 circulation.
- The study highlights the need to improve surveillance programs for HAstV.

Human astroviruses (HAstVs) are important enteric pathogens and can be classified genetically and antigenically into eight types. During molecular surveillance for HAstVs in Italy, sequence analysis of the diagnostic region C (about 400 nucleotide in length), located on the capsid (ORF2) gene, identified a novel type-3 strain. Upon sequencing of the full-length ORF2, the type-3 HAstV strain was characterized as a novel ORF2 genetic lineage, designated as 3c. By converse, in the ORF1b the virus was more similar to type-1 HAstVs, rather than to type-3 strains, suggesting a recombination nature, with the crossover site being mapped to the ORF1b/ORF2 junction region. Region C sequences of similar type-3 HAstV identified from European and extra-European countries were retrieved in the databases, suggesting the global distribution of this novel type-3 lineage.