The greatest risk of antiretroviral resistance from pre-exposure prophylaxis is conferred by use during undetected acute infection. Early, accurate identification of infection in HIV prevention trials is critical for protection of human subjects, data quality and study efficiency. We evaluated pre-seroconversion plasma from the VOICE Study (MTN-003) to determine if 4th generation antigen/antibody (Ag/Ab) rapid tests would have detected HIV infection earlier than the 3rd gen rapids used in the trial.
VOICE evaluated the safety and effectiveness of oral tenofovir disoproxil fumarate (TDF), oral TDF-emtricitabine (FTC) and vaginal tenofovir 1% gel for prevention of HIV infection in 5029 women from 15 clinical sites in South Africa, Uganda and Zimbabwe. Participants were monitored monthly for seroconversion with 1 or 2 3rd gen HIV rapids (Alere Determine™, OraQuick Advance® and/or Trinity Biotech™ Unigold®). Pre-seroconversion plasma collected closest to the date of the 1st positive rapid was tested for HIV-1 RNA (Roche TaqMan) and with Bio-Rad GS HIV Combo Ag/Ab EIA and re-tested with Unigold and OraQuick. The 4th gen FDA-approved Alere Determine™ HIV-1/2 Ag/Ab Combo (FDA-Combo) was compared with the Conformité Européene (CE)-Marked Alere™ (CE-Combo) which is marketed to be optimized for non-B subtypes. We also evaluated Multispot® (MS), Western Blot (WB), and Geenius™ (all Bio-Rad) as confirmatory tests. McNemar’s test was used to calculate statistical significance.
Of 231 plasma samples collected 12-91 days (median 55) before detection of seroconversion, 68 had RNA >200 cp/mL, and of those 57 tested negative by both Unigold and OraQuick. Of these 57, 30(53%) were reactive by 4th gen EIA. 16(28%) were reactive on the CE-Combo (1 Ab; 9 Ag; 6 Ag/Ab reactive). MS confirmed only 1 of 16 acute infections while WB (9 indeterminate [ind]) and Geenius (2 HIV-2 ind) confirmed none. 4(7%) samples were reactive by FDA-Combo (2 Ab; 2 Ag; 0 Ag/Ab reactive) of which none were confirmed by MS, WB (3 ind) or Geenius (1 HIV-2 ind). CE-Combo detected significantly more infections than FDA-Combo (p<0.002).
In VOICE, 28% of infections missed by current 3rd gen rapid tests would have been identified with the use of CE-marked Alere HIV Combo. Geenius, MS and WB were all insensitive (<10%) in confirming infections detected by 4th gen assays. An improved diagnostic algorithm that includes 4th gen rapids with HIV RNA testing will be essential for efficiently identifying seroconverters.