P44.09
Background: Vaccination with the RV144 regimen showed a waning efficacy of 60% at one year and 31.2% three years post-last vaccination. Risk correlated with plasma anti-Env binding antibody responses, but specimen volumes and collection sites limited analysis. HIV-vaccine naïve volunteers were vaccinated with the RV144 regimen plus a 12 month boost for immunologic assessment in multiple systemic and mucosal compartments.
Methods: Volunteers from 3 sites in Thailand were randomly enrolled into 4 placebo-controlled groups receiving the RV144 regimen plus no boost, ALVAC-HIV+AIDSVAX B/E, AIDSVAX B/E, or ALVAC at 12 months. Immune responses are being assessed both systemically and for additional site specimen collections in a subset of willing volunteers.
Results: Of 613 screened participants, 362 were enrolled (48% male and 52% female) with a mean age of 28 years. Consent to provide rectal secretions was provided by 69/172 (40%) of male volunteers, ranging from 12-90% among the three sites, while 135/172 (78%) consented to provide semen. Female participants consented for cervico-vaginal secretion collection (VTC: 69/95 (73%); RTA: 39/76 (51%); RIHES: 9/19 (47%), all sites: 117/190 (62%). Volunteers in two sites also consented for a single invasive procedure per participant as follows: Cervical biopsy (VTC: 44/95 (46%); RTA: 15/76 (20%); all sites 59/171 (35%), sigmoid biopsy in males [VTC: 29/57 (51%); RTA: 13/74 (18%); total 42/131 (32%)], leukapheresis: (VTC: 30/152 (20%); RTA 21/150 (14%); total 51/302 (17%) and bone marrow aspiration [VTC: 9/152 (6%); RTA: 5/150 (3%); total: 14/302 (5%)].
Conclusions: Mucosal collections and invasive procedure participation rates were high in this clinical trial conducted in Thailand, demonstrating both favorable disposition to research participation and effective counseling at the sites. Differences in participation in these procedures among sites provide insights that may lead to strategies to improve participation in future trials.
