Systemic Administration of Antiretrovirals Prior to Exposure Prevents Rectal and Intravenous HIV-1 Transmission in Humanized BLT Mice

Abstract

Successful antiretroviral pre-exposure prophylaxis (PrEP) for mucosal and intravenous HIV-1 transmission could reduce new infections among targeted high-risk populations including discordant couples, injection drug users, high-risk women and men who have sex with men. Targeted antiretroviral PrEP could be particularly effective at slowing the spread of HIV-1 if a single antiretroviral combination were found to be broadly protective across multiple routes of transmission. Therefore, we designed our in vivo preclinical study to systematically investigate whether rectal and intravenous HIV-1 transmission can be blocked by antiretrovirals administered systemically prior to HIV-1 exposure. We performed these studies using a highly relevant in vivo model of mucosal HIV-1 transmission, humanized Bone marrow/Liver/Thymus mice (BLT). BLT mice are susceptible to HIV-1 infection via three major physiological routes of viral transmission: vaginal, rectal and intravenous. Our results show that BLT mice given systemic antiretroviral PrEP are efficiently protected from HIV-1 infection regardless of the route of exposure. Specifically, systemic antiretroviral PrEP with emtricitabine and tenofovir disoproxil fumarate prevented both rectal (Chi square = 8.6, df = 1, p = 0.003) and intravenous (Chi square = 13, df = 1, p = 0.0003) HIV-1 transmission. Our results indicate that antiretroviral PrEP has the potential to be broadly effective at preventing new rectal or intravenous HIV transmissions in targeted high risk individuals. These in vivo preclinical findings provide strong experimental evidence supporting the potential clinical implementation of antiretroviral based pre-exposure prophylactic measures to prevent the spread of HIV/AIDS.

One Percent Tenofovir Applied Topically to Humanized BLT Mice and Used According to the CAPRISA 004 Experimental Design Demonstrates Partial Protection from Vaginal HIV Infection, Validating the BLT Model for Evaluation of New Microbicide Candidates

“…BLT mice were prepared essentially as previously described (6,11,12,24,25,31,41,45). Briefly, thymus/liver-implanted NOD/SCID or NOD/SCID-gamma chain null mice (NSG) (The Jackson Laboratories) were transplanted with autologous human fetal liver CD34 ϩ cells (Advanced Bioscience Resources) and monitored for human reconstitution in peripheral blood by flow cytometry, as we have previously described (11,12,31,45). Mice were maintained either at the Animal Resources Center of UT Southwestern Medical Center at Dallas or with the Division of Laboratory Animal Medicine at the University of North Carolina (UNC) at Chapel Hill in accordance with protocols approved by the each institution's Institutional Animal Care and Use Committee.…”

“…A trimeric D-peptide fusion inhibitor, PIE12-Trimer, was produced and purified as previously described and applied at a working concentration of 100 M (54). FTC-TDF was prepared as previously published and applied at a working concentration of 28 M and 16.5 M, respectively (12). Thioester compound 247 (TC247) was produced and purified as previously described and applied at a working concentration of 500 M (32).…”

“…Infection of BLT mice with HIV-1 was monitored in peripheral blood as follows: by determining plasma levels of viral antigenemia using a p24 enzyme-linked immunosorbent assay ([ELISA] assay sensitivity, 7.8 pg/ml; Coulter); by determining levels of viral RNA in plasma using either an Amplicor (Roche) assay or one-step reverse transcriptase real-time PCR (ABI custom TaqMan Assays-by-Design) according to the manufacturer's instructions (with primers 5Ј-CATGTTTTCAGCATTATCA GAAGGA-3Ј and 5Ј-TGCTTGATGTCCCCCCACT-3Ј and MGB-probe 5Ј-FAM-CCACCCCACAAGATTTAAACACCATGCTAA-Q-3Ј, where FAM is 6-carboxyfluorescein [37]; assay sensitivity of 400 RNA copies per ml in both assays); and by determining levels of viral DNA in peripheral blood cells (realtime PCR analysis; assay sensitivity of 10 copies) as previously described (11,12,45,53). The single-cell suspension preparation from the female reproductive tract (FRT) was adapted from a published protocol (22).…”

“…Cells were washed, counted using trypan blue exclusion, and utilized as indicated throughout the text, on figures, and in tables. Other tissues were harvested and then evaluated by molecular, microscopic, and flow cytometric analyses for evidence of HIV infection as we have previously described (11,12,31,45). The flow cytometry antibody panels for analysis of BLT mouse FRT were Analysis of systemic infection was performed on tissues harvested from infected mice or on cells isolated from the tissues indicated throughout the text, on figures, and in tables.…”

“…The evaluation of microbicide candidates would benefit significantly from validated animal models capable of accurately predicting human outcomes. Prior to the completion of the iPrEx trial, we reported the efficacy of systemic FTC-TDF to prevent vaginal and rectal HIV transmission in humanized bone marrow/liver/thymus (BLT) mice (11,12). Systemic FTC-TDF also was reported to prevent rectal simian-human immunodeficiency virus (SHIV) transmission in rhesus macaques (17).…”