Surveillance of HIV-1 genetic subtypes and diversity in the US blood supply

BACKGROUND: Recent reports of variant (non-subtype B) HIV infections in US populations have raised concerns about the sensitivity of subtype B virus-b ased donor screening and diagnostic assays. This study was designed to dete rmine the prevalence and genetic diversity of HIV subtypes in US blood dono rs over the last two decades. STUDY DESIGN AND METHODS: Three groups were studied: hemophiliacs infected by clotting factor concentrates in the early 1980s (n = 49), blood donors r etrospectively identified as being seropositive in 1985 (n = 97), and blood donors identified as seropositive between 1993 and 1996 (n = 405). Subtype assignment was based primarily on heteroduplex mobility analysis (HMA) of HIV-1 env, with DNA sequence confirmation of selected specimens. HIV peptid e-based EIA serotyping was used to rule out HIV-2 and group O infections an d to serotype HMA-refractory specimens. RESULTS: Of 551 specimens, 535 (97%) were assigned subtypes; 532 (99%) of t hese were subtype B. Three postscreening donations (1%) were assigned non-B subtypes (2 A, 1 C). Two of these three donors were born in Africa; the th ird was born in the United States and reported no risk factors other than h eterosexual activity. HMA distribution plots showed an increase in env dive rsity among HIV-1 group B strains over time. CONCLUSION: The results support the need for continued surveillance of HIV subtype diversity and ongoing validation of the sensitivity of HIV diagnost ic assays to non-B subtype infections.