Circulating and unique recombinant forms of HIV type 1 containing subsubtype A2.

HIV-1 strains containing subsubtype A2 are relatively rare in the pandemic but have been repeatedly identified in Kenya, where candidate vaccines based in part on subtype A, but not A2 strains, may be evaluated. Among the most recent is CRF16_A2D, a circulating recombinant form (CRF) whose prototypes are complete or partial HIV-1 sequences from Kenya, Korea, and Argentina. Using samples from blood bank discards in Kenya and complete genome sequencing, this report further documents CRF16_A2D and related recombinants and identifies a second CRF, CRF21_A2D. The two A2-containing CRFs, and two recombinants related to CRF16_A2D, share common structural elements but appear to have been independently derived. Concerted selection may have influenced the emergence and spread of certain A2-containing strains in Kenya. The second complete subtype C sequence from Kenya is also reported here. Monitoring of A2-containing recombinants and subtype C strains, both relatively rare in Kenya, may be informative in the course of cohort development and evaluation of candidate vaccines.