F gene recombination between genotype II and VII Newcastle disease virus

Homologous recombination as an evolutionary force in the avian influenza A virus

Avian influenza A viruses (AIVs), including the H5N1, H9N2, and H7N7 subtypes, have been directly transmitted to humans, raising concerns over the possibility of a new influenza pandemic. To prevent a future avian influenza pandemic, it is very important to fully understand the molecular basis driving the change in AIV virulence and host tropism. Although virulent variants of other viruses have been generated by homologous recombination, the occurrence of homologous recombination within AIV segments is controversial and far from proven. This study reports three circulating H9N2 AIVs with similar mosaic PA genes descended from H9N2 and H5N1. Additionally, many homologous recombinants are also found deposited in GenBank. Recombination events can occur in PB2, PB1, PA, HA, and NP segments and between lineages of the same/different serotype. These results collectively demonstrate that intragenic recombination plays a role in driving the evolution of AIVs, potentially resulting in effects on AIV virulence and host tropism changes.

Cross-species recombination in the haemagglutinin gene of canine distemper virus

Canine distemper virus (CDV) has high prevalence in the world dog population and poses an important conservation threat to many carnivore species. In this study, extensive phylogenetic and recombination analyses were performed on all available complete haemagglutinin gene sequences and a strain (AF178038) isolated from giant panda was identified as putative recombinant. Interestingly, the mosaic was produced by recombination between genotypes European wildlife and Asia-1 and the recombination event involves viruses infecting different host species. This finding may have important implications for the evolution of CDV.