Vaginal HIV Transmission Research Articles

Role of Semen on Vaginal HIV-1 Transmission and Maraviroc Protection

Role of Semen on Vaginal HIV-1 Transmission and Maraviroc Protection

The Role of Semen on Vaginal HIV-1 Transmission and on the Efficacy of Maraviroc as a Topically Applied Microbicide

AIDS Research and Human RetrovirusesVol. 30, No. S1 Evaluation of Novel InterventionsThe Role of Semen on Vaginal HIV-1 Transmission and on the Efficacy of Maraviroc as a Topically Applied MicrobicideOlivia Snyder, Angela Wahl, Michael Swanson, Rae Ann Spagnuolo, and J. Victor GarciaOlivia SnyderSearch for more papers by this author, Angela WahlSearch for more papers by this author, Michael SwansonSearch for more papers by this author, Rae Ann SpagnuoloSearch for more papers by this author, and J. Victor GarciaSearch for more papers by this authorPublished Online:30 Oct 2014https://doi.org/10.1089/aid.2014.5087.abstractAboutSectionsView articleView Full TextPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"The Role of Semen on Vaginal HIV-1 Transmission and on the Efficacy of Maraviroc as a Topically Applied Microbicide." AIDS Research and Human Retroviruses, 30(S1), p. A50FiguresReferencesRelatedDetails Volume 30Issue S1Oct 2014 InformationCopyright 2014, Mary Ann Liebert, Inc.To cite this article:Olivia Snyder, Angela Wahl, Michael Swanson, Rae Ann Spagnuolo, and J. Victor Garcia.The Role of Semen on Vaginal HIV-1 Transmission and on the Efficacy of Maraviroc as a Topically Applied Microbicide.AIDS Research and Human Retroviruses.Oct 2014.A50-A50.http://doi.org/10.1089/aid.2014.5087.abstractPublished in Volume: 30 Issue S1: October 30, 2014PDF download

FACTS 001: Characteristics of Participants Enrolled in a Phase III Randomised Controlled Trial of Tenofovir Gel for Prevention of HIV-1 and HSV-2

AIDS Research and Human RetrovirusesVol. 30, No. S1 Tenofovir Gel: Acceptability and AdherenceFACTS 001: Characteristics of Participants Enrolled in a Phase III Randomised Controlled Trial of Tenofovir Gel for Prevention of HIV-1 and HSV-2Sinead Delany-Moretlwe, Emilee Smith, Landon Myer, Khatija Ahmed, Busi Nkala, Rebone Maboa, Cynthia Gama, Sydney Sibiya, Modulakgotla Sebe, William Brumskine, Linda-Gail Bekker, Maposhane Nchabeleng, Carl Lombard, Glenda Gray, Helen Rees, and FACTS 001 Study GroupSinead Delany-MoretlweUniversity of the Witwatersrand, Wits Reproductive Health & HIV Institute, Johannesburg, South AfricaSearch for more papers by this author, Emilee SmithUniversity of Cape Town, Centre for Infectious Diseases Epidemiology & Research, Cape Town, South AfricaSearch for more papers by this author, Landon MyerUniversity of Cape Town, Centre for Infectious Diseases Epidemiology & Research, Cape Town, South AfricaSearch for more papers by this author, Khatija AhmedSetshaba Research Centre, Soshanguve, South AfricaSearch for more papers by this author, Busi NkalaUniversity of the Witwatersrand, Perinatal HIV Research Unit, Soweto, South AfricaSearch for more papers by this author, Rebone MaboaUniversity of the Witwatersrand, Wits Reproductive Health and HIV Institute, Johannesburg, South AfricaSearch for more papers by this author, Cynthia GamaUniversity of the Witwatersrand, MATCH, Durban, South AfricaSearch for more papers by this author, Sydney SibiyaQhakaza Mbokodo Research Centre, Ladysmith, South AfricaSearch for more papers by this author, Modulakgotla SebeAurum Institute, Tembisa, South AfricaSearch for more papers by this author, William BrumskineAurum Institute, Rustenburg, South AfricaSearch for more papers by this author, Linda-Gail BekkerUniversity of Cape Town, Desmond Tutu HIV Centre, Cape Town, South AfricaSearch for more papers by this author, Maposhane NchabelengMedunsa, Medunsa Clinical Research Unit (MeCRU), Ga-Rankuwa, South AfricaSearch for more papers by this author, Carl LombardMedical Research Council of South Africa, Cape Town, South AfricaSearch for more papers by this author, Glenda GrayUniversity of the Witwatersrand, Perinatal HIV Research Unit, Soweto, South AfricaMedical Research Council of South Africa, Cape Town, South AfricaSearch for more papers by this author, Helen ReesUniversity of the Witwatersrand, Wits Reproductive Health & HIV Institute, Johannesburg, South AfricaSearch for more papers by this author, and FACTS 001 Study GroupSearch for more papers by this authorPublished Online:30 Oct 2014https://doi.org/10.1089/aid.2014.5637.abstractAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"FACTS 001: Characteristics of Participants Enrolled in a Phase III Randomised Controlled Trial of Tenofovir Gel for Prevention of HIV-1 and HSV-2." AIDS Research and Human Retroviruses, 30(S1), pp. A281–A282FiguresReferencesRelatedDetailsCited byPrevention of vaginal and rectal HIV transmission by antiretroviral combinations in humanized mice7 September 2017 | PLOS ONE, Vol. 12, No. 9 Volume 30Issue S1Oct 2014 InformationCopyright 2014, Mary Ann Liebert, Inc.To cite this article:Sinead Delany-Moretlwe, Emilee Smith, Landon Myer, Khatija Ahmed, Busi Nkala, Rebone Maboa, Cynthia Gama, Sydney Sibiya, Modulakgotla Sebe, William Brumskine, Linda-Gail Bekker, Maposhane Nchabeleng, Carl Lombard, Glenda Gray, Helen Rees, and FACTS 001 Study Group.FACTS 001: Characteristics of Participants Enrolled in a Phase III Randomised Controlled Trial of Tenofovir Gel for Prevention of HIV-1 and HSV-2.AIDS Research and Human Retroviruses.Oct 2014.A281-A282.http://doi.org/10.1089/aid.2014.5637.abstractPublished in Volume: 30 Issue S1: October 30, 2014PDF download

Testing a Fast-dissolving Tablet Containing a Recombinant Live Biotherapeutic Product, MucoCept-CVN, in the Non-human Primate Model for Colonization

OA18.04 Background: Osel developed a recombinant live biotherapeutic product, MucoCept-CVN based on human vaginal Lactobacillus jensenii expressing the HIV-1 entry inhibitor Cyanovirin-N for prevention of vaginal transmission of HIV-1. We previously reported that macaques colonized with a live bacterial preparation in hydroxyethylcellulose showed a 63% reduction of SHIVSF162P3 acquisition followed repeated vaginal challenge. We formulated MucoCept-CVN as a fast dissolving vaginal tablet, which would allow for discreet, coital-independent, female controlled use. Tablets were potent (5.8 x 1011 colony forming units (CFUs)/gram) and stable for at least one year at 4°C and 25oC. Macaques were dosed with 1 tablet or 5 tablets delivered over 5 days. We examined colonization of the MucoCept-CVN bacteria in the rhesus macaque vagina at 14 and 21 days post dosing and found that 83% were highly colonized. Methods: Fast dissolving tablet were formulated (∼110 mg in a 1 x 1.5 cm mold). Tablet friability and dissolution were tested. Stability of the product was monitored for 1 year at 4°C and 25°C and for 2 months at 37°C. A single tablet or multiple tablets were administered to 18 rhesus macaques and vaginal colonization was monitored at 14 and 21 days post dosing by culture and PCR. Results: Tablets were potent and contained 5.8 x 1011 colony forming units (CFUs)/gram. The tablets were stable 1 yr at 4°C and 25oC and for 1 month at 37°C. The tablets maintained integrity when handled and dissolved quickly. High levels of colonization ∼108 CFU/vaginal swab of colonization were achieved in 15/18 macaques by day 21 post dosing. Two macaques had lower colonization levels ∼105 CFU/swab and in one macaque bacteria were detected by PCR only. Conclusions: MucoCept-CVN can be formulated and delivered as a conventional fast dissolving tablet dosage form. Colonization was achieved in 83% of macaques. The tablets were easy to handle and stable for>1 yr. This tablet formulation can be manufactured on large scale for ease of use.

Modeling neutralization kinetics of HIV by broadly neutralizing monoclonal antibodies in genital secretions coating the cervicovaginal mucosa.

Eliciting broadly neutralizing antibodies (bnAb) in cervicovaginal mucus (CVM) represents a promising “first line of defense” strategy to reduce vaginal HIV transmission. However, it remains unclear what levels of bnAb must be present in CVM to effectively reduce infection. We approached this complex question by modeling the dynamic tally of bnAb coverage on HIV. This analysis introduces a critical, timescale-dependent competition: to protect, bnAb must accumulate at sufficient stoichiometry to neutralize HIV faster than virions penetrate CVM and reach target cells. We developed a model that incorporates concentrations and diffusivities of HIV and bnAb in semen and CVM, kinetic rates for binding (kon) and unbinding (koff) of select bnAb, and physiologically relevant thicknesses of CVM and semen layers. Comprehensive model simulations lead to robust conclusions about neutralization kinetics in CVM. First, due to the limited time virions in semen need to penetrate CVM, substantially greater bnAb concentrations than in vitro estimates must be present in CVM to neutralize HIV. Second, the model predicts that bnAb with more rapid kon, almost independent of koff, should offer greater neutralization potency in vivo. These findings suggest the fastest arriving virions at target cells present the greatest likelihood of infection. It also implies the marked improvements in in vitro neutralization potency of many recently discovered bnAb may not translate to comparable reduction in the bnAb dose needed to confer protection against initial vaginal infections. Our modeling framework offers a valuable tool to gaining quantitative insights into the dynamics of mucosal immunity against HIV and other infectious diseases.

Vectored immunoprophylaxis protects humanized mice from mucosal HIV transmission.

The vast majority of new HIV infections result from relatively inefficient transmission1,2 of the virus across mucosal surfaces during sexual intercourse3. A consequence of this inefficiency is that small numbers of transmitted founder viruses initiate most heterosexual infections4. This natural bottleneck to transmission has stimulated efforts to develop interventions aimed at blocking this step of the infection process5. Despite the promise of this strategy, clinical trials of pre-exposure prophylaxis have had limited degrees of success in humans, due in part to lack of adherence to the recommended pre-exposure treatment regimens6,7. In contrast, a number of existing vaccines elicit systemic immunity that protects against mucosal infections, such as the vaccines for influenza8 and HPV9. We recently demonstrated the ability of vectored immunoprophylaxis (VIP) to prevent intravenous transmission of HIV using broadly neutralizing antibodies10. Here we demonstrate that VIP is capable of protecting humanized mice from intravenous as well as vaginal challenge with diverse viral strains, despite repeated exposures. Moreover, animals receiving VIP that expresses a modified VRC07 antibody were completely resistant to repetitive intravaginal challenge by a heterosexually transmitted founder HIV strain11, suggesting that VIP may be effective in preventing vaginal transmission of HIV between humans.

BLT Humanized Mice as Model to Study HIV Vaginal Transmission

The majority of human immunodeficiency virus type 1 (HIV-1) infections occur by sexual exposure, and vaginal transmission accounts for more than half of all newly acquired infections. Studies of vaginal transmission of simian immunodeficiency virus to nonhuman primates (NHPs) have suggested an important role for immune cell trafficking in the establishment of infection as well is in the process of viral dissemination. However, NHP models do not permit the study of HIV transmission and dissemination. The improvement of humanized mouse models with robust human immune cell reconstitution of the female genital tract renders these mice susceptible to intravaginal HIV infection. Thus humanized mouse models of HIV vaginal infection will allow the study of the mechanisms involved in HIV transmission and dissemination in vivo.

HIV gp120 induced gene expression signatures in vaginal epithelial cells

Gp120 is the envelope protein of HIV which binds to CD4 independent proteins on vaginal epithelial cells. HIV-gp120 has been reported to modulate gene expression in several cell types. How this interaction may alter the physiologic vaginal milieu during the earliest stages of vaginal transmission of HIV, is currently unknown. Vaginal epithelial cells were treated with HIV-gp120, and a global snapshot of changes in gene expression profiles, were unraveled by microarray analysis. The differentially expressed genes were involved in diverse cellular functions. Genes of immunomodulatory processes and induction of proteases were highly enriched. We propose that the induction of inflammation and proteases may act in concert to weaken the vaginal epithelium, making it more permeable to viral entry. Identification of the gene signatures involved in vaginal-HIV dialogue would aid in understanding the environ induced by HIV itself, as the virus invades and gains entry into its host.

Prevention of Vaginal SHIV Transmission in Macaques by a Coitally-Dependent Truvada Regimen

BackgroundDaily pre-exposure prophylaxis (PrEP) with Truvada (a combination of emtricitabine (FTC) and tenofovir (TFV) disoproxil fumarate (TDF)) is a novel HIV prevention strategy recently found to prevent HIV transmission in men who have sex with men and heterosexual couples. We previously showed that a coitally-dependent Truvada regimen protected macaques against rectal SHIV transmission. Here we examined FTC and tenofovir TFV exposure in vaginal tissues after oral dosing and assessed if peri-coital Truvada also protects macaques against vaginal SHIV infection.MethodsThe pharmacokinetic profile of emtricitabine (FTC) and tenofovir (TFV) was evaluated at first dose. FTC and TFV levels were measured in blood plasma, rectal, and vaginal secretions. Intracellular concentrations of FTC-triphosphate (FTC-TP) and TFV-diphosphate (TFV-DP) were measured in PBMCs, rectal tissues, and vaginal tissues. Efficacy of Truvada in preventing vaginal SHIV infection was assessed using a repeat-exposure vaginal SHIV transmission model consisting of weekly exposures to low doses of SHIV162p3. Six pigtail macaques with normal menstrual cycles received Truvada 24 h before and 2 h after each weekly virus exposure and six received placebo. Infection was monitored by serology and PCR amplification of SHIV RNA and DNA.ResultsAs in humans, the concentration of FTC was higher than the concentration of TFV in vaginal secretions. Also as in humans, TFV levels in vaginal secretions were lower than in rectal secretions. Intracellular TFV-DP concentrations were also lower in vaginal tissues than in rectal tissues. Despite the low vaginal TFV exposure, all six treated macaques were protected from infection after 18 exposures or 4 full menstrual cycles. In contrast, all 6 control animals were infected.ConclusionsWe modeled a peri-coital regimen with two doses of Truvada and showed that it fully protected macaques from repeated SHIV exposures. Our results open the possibility for simplified PrEP regimens to prevent vaginal HIV transmission in women.

Inefficient Vaginal Transmission of Tenofovir-Resistant HIV-1

Transmission of drug-resistant HIV has been postulated to be a threat to current first-line antiretroviral therapy (ART) regimens and the efficacy of several antiretroviral-based preexposure prophylaxis (PrEP) strategies being tested. Here we evaluated the effect of the common tenofovir (TFV) resistance mutation K65R on vaginal HIV transmission. Our results demonstrate that despite no overt loss of overall replication competence in vivo, this mutation results in significantly reduced mucosal transmission. When transmitted, the mutant virus eventually reverted to the wild type in 2 of 3 animals examined.

Topical gel formulation of broadly neutralizing anti-HIV-1 monoclonal antibody VRC01 confers protection against HIV-1 vaginal challenge in a humanized mouse model

The new generation broadly neutralizing antibody VRC01 against HIV-1 shows great potential as a topically administered microbicide to prevent sexual transmission. We evaluated its efficacy in a RAG-hu humanized mouse model of vaginal HIV-1 transmission. Mice were challenged vaginally with R5 tropic HIV-1 BaL an hour after intravaginal application of the VRC01 (1mg/ml concentration) gel. A combination of four first generation bNAbs, namely b12, 2F5, 4E10 and 2G12, was used as a positive efficacy control whereas a non-specific dengue MAb 4G2 was used as negative control. Our results showed that seven out of nine VRC01 antibody administered mice and all of the mice receiving the four bNAb antibody combination were protected against HIV-1 challenge. These findings demonstrate the efficacy of the new bNAb VRC01 as a topical microbicide to protect against HIV-1 vaginal transmission and highlight the use of the RAG-hu mouse model for testing HIV prevention strategies.

More than just a cut: a qualitative study of penile practices and their relationship to masculinity, sexuality and contagion and their implications for HIV prevention in Papua New Guinea

BackgroundMale circumcision (MC) has been shown to reduce vaginal transmission of HIV to men. While community acceptability is important in a countries preparedness to introduce MC, it is equally important to map contemporary MC and other penile cutting practices, and the socio-cultural dimensions underpinning these practices.MethodsA total of 482 men and women (n = 276 and n = 210, respectively) participated in 82 semi-structured and 45 focus group discussions from four different provinces of Papua New Guinea (PNG), each representing one of the four socially and geographically diverse regions of the country.ResultsOf the men interviewed 131 self-reported that they had undergone a penile alteration with some reporting multiple types. Practices were diverse and could be grouped into five broad categories: traditional (customary) penile cutting; contemporary penile cutting; medical circumcision; penile inserts; and penile bloodletting practices in which sharp objects are used to incise the glans and or inserted and withdrawn from the male urethra or in order to induce bleeding. Socio-cultural traditions, enhanced sexual pleasure and improved genital hygiene were key motivators for all forms of penile practices.ConclusionsThe findings from this study highlight the complex and diverse nature of penile practices in PNG and their association with notions of masculinity, sexuality and contagion. Contemporary penile practices are critical to a community’s acceptance of MC and of a country’s ability to successfully implement MC in the context of a rich and dynamic culture of penile practices. If a MC program were to be successfully rolled out in PNG to prevent HIV it would need to work within and build upon these diverse cultural meanings and motivators for penile practices already commonly performed in PNG by men.

Live-Attenuated Lentivirus Immunization Modulates Innate Immunity and Inflammation while Protecting Rhesus Macaques from Vaginal Simian Immunodeficiency Virus Challenge

Immunization with attenuated lentiviruses is the only reliable method of protecting rhesus macaques (RM) from vaginal challenge with pathogenic simian immunodeficiency virus (SIV). CD8(+) lymphocyte depletion prior to SIVmac239 vaginal challenge demonstrated that a modest, Gag-specific CD8(+) T cell response induced by immunization with simian-human immunodeficiency virus 89.6 (SHIV89.6) protects RM. Although CD8(+) T cells are required for protection, there is no anamnestic expansion of SIV-specific CD8(+) T cells in any tissues except the vagina after challenge. Further, SHIV immunization increased the number of viral target cells in the vagina and cervix, suggesting that the ratio of target cells to antiviral CD8(+) T cells was not a determinant of protection. We hypothesized that persistent replication of the attenuated vaccine virus modulates inflammatory responses and limits T cell activation and expansion by inducing immunoregulatory T cell populations. We found that attenuated SHIV infection decreased the number of circulating plasmacytoid dendritic cells, suppressed T cell activation, decreased mRNA levels of proinflammatory mediators, and increased mRNA levels of immunoregulatory molecules. Three days after SIV vaginal challenge, SHIV-immunized RM had significantly more T regulatory cells in the vagina than the unimmunized RM. By day 14 postchallenge, immune activation and inflammation were characteristic of unimmunized RM but were minimal in SHIV-immunized RM. Thus, a modest vaccine-induced CD8(+) T cell response in the context of immunoregulatory suppression of T cell activation may protect against vaginal HIV transmission.

Limited or no protection by weakly or nonneutralizing antibodies against vaginal SHIV challenge of macaques compared with a strongly neutralizing antibody

To guide vaccine design, we assessed whether human monoclonal antibodies (MAbs) b12 and b6 against the CD4 binding site (CD4bs) on HIV-1 gp120 and F240 against an immundominant epitope on gp41 could prevent vaginal transmission of simian HIV (SHIV)-162P4 to macaques. The two anti-gp120 MAbs have similar monomeric gp120-binding properties, measured in vitro, but b12 is strongly neutralizing and b6 is not. F240 is nonneutralizing. Applied vaginally at a high dose, the strongly neutralizing MAb b12 provided sterilizing immunity in seven of seven animals, b6 in zero of five animals, and F240 in two of five animals. Compared with control animals, the protection by b12 achieved statistical significance, whereas that caused by F240 did not. For two of three unprotected F240-treated animals there was a trend toward lowered viremia. The potential protective effect of F240 may relate to the relatively strong ability of this antibody to capture infectious virions. Additional passive transfer experiments also indicated that the ability of the administered anti-gp120 MAbs to neutralize the challenge virus was a critical influence on protection. Furthermore, when data from all of the experiments were combined, there was a significant increase in the number of founder viruses establishing infection in animals receiving MAb b6, compared with other nonprotected macaques. Thus, a gp120-binding, weakly neutralizing MAb to the CD4bs was, at best, completely ineffective at protection. A nonneutralizing antibody to gp41 may have a limited capacity to protect, but the results suggest that the central focus of HIV-1 vaccine research should be on the induction of potently neutralizing antibodies.

Superior human leukocyte reconstitution and susceptibility to vaginal HIV transmission in humanized NOD- scid IL-2Rγ −/− (NSG) BLT mice

Humanized Bone marrow/Liver/Thymus (BLT) mice recapitulate the mucosal transmission of HIV, permitting study of early events in HIV pathogenesis and evaluation of preexposure prophylaxis methods to inhibit HIV transmission. Human hematopoiesis is reconstituted in NOD- scid mice by implantation of human fetal liver and thymus tissue to generate human T cells plus intravenous injection of autologous liver-derived CD34 + hematopoietic stem cells to engraft the mouse bone marrow. In side-by-side comparisons, we show that NOD- scid mice homozygous for a deletion of the IL-2Rγ-chain (NOD- scid IL-2Rγ −/−) are far superior to NOD- scid mice in both their peripheral blood reconstitution with multiple classes of human leukocytes (e.g., a mean of 182 versus 14 CD4 + T cells per μl 12 weeks after CD34 + injection) and their susceptibility to intravaginal HIV exposure (84% versus 11% viremic mice at 4 weeks). These results should speed efforts to obtain preclinical animal efficacy data for new HIV drugs and microbicides.

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

Recent iPrEx clinical trial results provided evidence that systemic preexposure prophylaxis (PrEP) with emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF) can partially prevent rectal HIV transmission in humans. Similarly, we have previously demonstrated that systemic administration of the same FTC-TDF combination efficiently prevented rectal transmission in humanized bone marrow/liver/thymus (BLT) mice. The CAPRISA 004 trial recently demonstrated that topical application of the tenofovir could partially prevent vaginal HIV-1 transmission in humans. To further validate the usefulness of the BLT mouse model for testing HIV prevention strategies, we evaluated the topical administration of tenofovir as used in CAPRISA 004 to prevent vaginal HIV transmission in BLT mice. Our results demonstrate that vaginally administered 1% tenofovir significantly reduced HIV transmission in BLT mice (P = 0.002). Together with the results obtained after systemic antiretroviral PrEP, these topical inhibitor data serve to validate the use of humanized BLT mice to evaluate both systemic and topical inhibitors of HIV transmission. Based on these observations, we tested six additional microbicide candidates for their ability to prevent vaginal HIV transmission: a C-peptide fusion inhibitor (C52L), a membrane-disrupting amphipathic peptide inhibitor (C5A), a trimeric d-peptide fusion inhibitor (PIE12-Trimer), a combination of reverse transcriptase inhibitors (FTC-TDF), a thioester zinc finger inhibitor (TC247), and a small-molecule Rac inhibitor (NSC23766). No protection was seen with the Rac inhibitor NSC23766. The thioester compound TC247 offered partial protection. Significant protection was afforded by FTC-TDF, and complete protection was offered by three different peptide inhibitors tested. Our results demonstrate that these effective topical inhibitors have excellent potential to prevent vaginal HIV transmission in humans.

Inhibition of HIV transmission in human cervicovaginal explants and humanized mice using CD4 aptamer-siRNA chimeras

The continued spread of the HIV epidemic underscores the need to interrupt transmission. One attractive strategy is a topical vaginal microbicide. Sexual transmission of herpes simplex virus type 2 (HSV-2) in mice can be inhibited by intravaginal siRNA application. To overcome the challenges of knocking down gene expression in immune cells susceptible to HIV infection, we used chimeric RNAs composed of an aptamer fused to an siRNA for targeted gene knockdown in cells bearing an aptamer-binding receptor. Here, we showed that CD4 aptamer-siRNA chimeras (CD4-AsiCs) specifically suppress gene expression in CD4⁺ T cells and macrophages in vitro, in polarized cervicovaginal tissue explants, and in the female genital tract of humanized mice. CD4-AsiCs do not activate lymphocytes or stimulate innate immunity. CD4-AsiCs that knock down HIV genes and/or CCR5 inhibited HIV infection in vitro and in tissue explants. When applied intravaginally to humanized mice, CD4-AsiCs protected against HIV vaginal transmission. Thus, CD4-AsiCs could be used as the active ingredient of a microbicide to prevent HIV sexual transmission.

Mucoadhesive nanosystems for vaginal microbicide development: friend or foe?

Topical microbicides are a promising strategy in the prevention of vaginal and rectal HIV transmission as well as other sexually transmitted pathogens. The perspective of developing nanotechnology-based systems for topical microbicides seems to be useful because important features such as enhanced drug release, targeting, and epithelial penetration can be achieved. However, the interaction of nanoparticles with the mucus fluids that cover the cervicovaginal mucosal epithelium, which can work either as a docking point or as a barrier for diffusion, has been frequently neglected. In this review, we discuss the principles of nanosystems' adhesion to the mucosal tissue and how this relates to the development of optimized microbicide formulations.

Immune reconstitution of the female reproductive tract of humanized BLT mice and their susceptibility to human immunodeficiency virus infection

An HIV vaccine capable of providing sterilizing immunity from vaginal infection would reduce the spread of HIV to women. Unfortunately, only one of the four HIV-1 vaccine clinical trials has demonstrated any level of protection (31%) against HIV-1 transmission. Additionally, only one topical microbicide clinical trial has reported an overall reduction in HIV transmission (39%). Developing even more effective vaccines and microbicides will require a better understanding of the key events involved in HIV infection and dissemination at the site of exposure. Novel immunodeficient mice capable of being systemically reconstituted with human hematopoietic stem cells have provided new systems where HIV transmission studies can be performed. Specifically, a humanized mouse model of vaginal HIV transmission has been developed that utilizes the humanized bone marrow-liver-thymus (BLT) mouse. The female reproductive tract (FRT) of humanized BLT mice is reconstituted with functional human immune cells rendering them susceptible to vaginal HIV-1 infection. In this review we focus on four aspects of BLT mice for the study of vaginal HIV-1 transmission: (1) we discuss methods for creating humanized BLT mice and their reconstitution with human hematopoietic cells, (2) we describe reconstitution of the BLT mouse FRT with human immune cells, (3) we highlight the work done regarding vaginal HIV-1 transmission and (4) we summarize the efficacy of systemic pre-exposure prophylaxis (PrEP) to prevent vaginal HIV-1 transmission in BLT mice. BLT mice are a highly relevant small animal model for studying vaginal HIV-1 transmission, prevention and therapy.

Cervico‐Vaginal Tissue Ex Vivo as a Model to Study Early Events in HIV‐1 Infection

Vaginal intercourse remains the most prevalent route of infection of women. In spite of many efforts, the detailed mechanisms of HIV-1 transmission in the female lower genital tract remain largely unknown. With all the obvious restrictions on studying these mechanisms in humans, their understanding depends on the development of adequate experimental models. Isolated cell cultures do not faithfully reproduce important aspects of cell-cell interactions in living tissues and tissue responses to pathogens. Explants and other types of ex vivo tissue models serve as a bridge between cell culture and tissues in vivo. Herein, we discuss various cervico-vaginal tissue models and their use in studying HIV vaginal transmission and consider future directions of such studies.