Pharmacokinetic/pharmacodynamic investigation of raltegravir with or without lamivudine in the context of HIV-1 pre-exposure prophylaxis (PrEP)

Ex vivo challenge models for infectious diseases

Traditionally, molecular mechanisms of pathogenesis for infectious agents were studied in cell culture or animal models but have limitations on the extent to which the resulting data reflect natural infection in humans. The COVID-19 pandemic has highlighted the urgent need to rapidly develop laboratory models that enable the study of host-pathogen interactions, particularly the relative efficacy of preventive measures. Recently, human and animal ex vivo tissue challenge models have emerged as a promising avenue to study immune responses, screen potential therapies and triage vaccine candidates. This approach offers the opportunity to closely approximate human disease from the perspective of pathology and immune response. It has advantages compared to animal models which are expensive, lengthy and often require containment facilities. Herein, we summarize some recent advances in the development of ex vivo tissue challenge models for COVID-19, HIV-1 and other pathogens. We focus on the contribution of these models to enhancing knowledge of host-pathogen interactions, immune modulation, and their value in testing therapeutic agents. We further highlight the advantages and limitations of using ex vivo challenge models and briefly summarize how the use of organoids provides a useful advancement over current approaches. Collectively, these developments have enormous potential for the study of infectious diseases.

Dose finding study for on-demand HIV pre-exposure prophylaxis for insertive sex in sub-Saharan Africa: results from the CHAPS open label randomised controlled trial

BACKGROUND

The efficacy of on-demand HIV pre-exposure prophylaxis (PrEP) for men in sub-Saharan Africa has not been evaluated, and the on-demand PrEP dosing requirement for insertive sex remains unknown.

METHODS

HIV-negative males 13-24 years, requesting voluntary medical male circumcision (VMMC), were enrolled into an open-label randomised controlled trial (NCT03986970), and randomised 1:1:1:1:1:1:1:1:1 to control arm or one of eight arms receiving emtricitabine-tenofovir disoproxil fumarate (F/TDF) or emtricitabine-tenofovir alafenamide (F/TAF) over one or two days, and circumcised 5 or 21 h thereafter. The primary outcome was foreskin p24 concentrations following ex vivo HIV-1BaL challenge. Secondary outcomes included peripheral blood mononuclear cell (PBMC) p24 concentration, and drug concentrations in foreskin tissue, PBMCs, plasma and foreskin CD4+/CD4-cells. In the control arm, post-exposure prophylaxis (PEP) activity of non-formulated tenofovir-emtricitabine (TFV-FTC) or TAF-FTC was assessed with ex vivo dosing 1, 24, 48 or 72 h post-HIV-1 challenge.

FINDINGS

144 participants were analysed. PrEP with F/TDF or F/TAF prevented ex vivo infection of foreskins and PBMCs both 5 and 21 h after PrEP dosing. There was no difference between F/TDF and F/TAF (p24day15 geometric mean ratio 1.06, 95% confidence interval: 0.65-1.74). Additional ex vivo dosing did not further increase inhibition. In the control arm, PEP ex vivo dosing was effective up to 48 post-exposure diminishing thereafter, with TAF-FTC showing prolonged protection compared to TFV-FTC. Participants receiving F/TAF had higher TFV-DP concentrations in foreskin tissue and PBMCs compared with F/TDF, irrespective of dose and sampling interval; but F/TAF did not confer preferential TFV-DP distribution into foreskin HIV target cells. FTC-TP concentrations with both drug regimens were equivalent and ∼1 log higher than TFV-DP in foreskin.

INTERPRETATION

A double dose of either F/TDF or F/TAF given once either 5 or 21 h before ex vivo HIV-challenge provided protection across foreskin tissue. Further clinical evaluation of pre-coital PrEP for insertive sex is warranted.

FUNDING

EDCTP2, Gilead Sciences, Vetenskapsrådet.

Pharmacokinetics, the Immunological Impact, and the Effect on HIV Ex-Vivo Infectivity of Maraviroc, Raltegravir, and Lopinavir in Men Who Have Sex with Men Using Postexposure Prophylaxis

Most of the studies using the colorectal tissue explants challenge model have been conducted after one single dose and before reaching a steady state. We consider that longer exposure as in 28-day postexposure prophylaxis (PEP) course and in an at-risk setting, such as after a sexual risk exposure to HIV could give us valuable information about these drugs. In a substudy we assessed pharmacokinetics, changes on immune system and ex-vivo rectal mucosal susceptibility to HIV-1 infection after taking maraviroc (MVC), raltegravir (RAL), and ritonavir-boosted lopinavir (LPV/r) PEP-based regimens in 30 men who have sex with men. Participants received 28 days of twice-daily MVC (n = 11), RAL (n = 10) or LPV/r (n = 9) all with tenofovir/emtricitabine (TDF/FTC) backbone. Blood, rectal fluid, and rectal tissue samples were collected at days 7, 28, and 90 after starting PEP. The samples obtained at day 90 were considered baseline. All studied antiretrovirals were quantifiable at 7 and 28 days in all tissues. Activation markers were increased in CD4 mucosal mononuclear cells (MMCs) after 28 days of MVC: CD38 + 68.5 versus 85.1, p = .008 and CD38+DR +16.1 versus 26.7, p = .008. Exposure to MVC at both endpoints (7 and 28 days) was associated with significant suppression of HIV-1BAL (p = .005 and p = .028), but we did not observe this effect with RAL or LPV/r. Merging together changes in MMC in all arms, we found a positive correlation in the CD8 T cell lineage between the infectivity at day 7 and activation (CD38+ r = 0.43, p = .025, DR + r = 0.547, p = .003 and 38+DR+ r = 0.526, p = .05), senescence (CD57+CD28- r = 0.479, p = .012), naive cells (RA+CCR7+ r = 0.484, p = .01), and CCR5 expression (r = 0.593, p = .001). We conclude that MVC in combination with TDF/FTC was associated with viral suppression in rectal explants and that overall ex-vivo HIV infectivity correlated with activation and senescence in CD8 MMCs.

Women for science and science for women: Gaps, challenges and opportunities towards optimizing pre-exposure prophylaxis for HIV-1 prevention

Preventing new HIV infections remains a global challenge. Young women continue to bear a disproportionate burden of infection. Oral pre-exposure prophylaxis (PrEP), offers a novel women-initiated prevention technology and PrEP trials completed to date underscore the importance of their inclusion early in trials evaluating new HIV PrEP technologies. Data from completed topical and systemic PrEP trials highlight the role of gender specific physiological and social factors that impact PrEP uptake, adherence and efficacy. Here we review the past and current developments of HIV-1 prevention options for women with special focus on PrEP considering the diverse factors that can impact PrEP efficacy. Furthermore, we highlight the importance of inclusion of female scientists, clinicians, and community advocates in scientific efforts to further improve HIV prevention strategies.

Translational Models to Predict Target Concentrations for Pre-Exposure Prophylaxis in Women

The HIV epidemic remains a significant public health burden. Women represent half of the global HIV epidemic, yet there is an urgent need for a variety of prevention options to meet the needs of more women. Pre-exposure prophylaxis (PrEP) is a valuable prevention tool that uses antiretrovirals before a potential HIV exposure to prevent virus transmission. Development of effective preventive drug regimens for women is dependent on convenient dosing schedules and routes of administration, and on identifying defined target concentrations in mucosal tissues that provide complete protection against HIV transmission. There is a critical need for a translational model that can accurately predict in vivo target concentrations that are completely protective against HIV infection. There is no gold-standard preclinical model to predict PrEP efficacy. In this study, we review the strengths and limitations of three different preclinical models and their utility in predicting target concentrations in the female genital tract: humanized mice, non-human primates, and the ex vivo tissue model.

Pre-clinical evaluation of antiproteases as potential candidates for HIV-1 pre-exposure prophylaxis

Previous studies on highly HIV-1-exposed, yet persistently seronegative women from the Punwami Sex Worker cohort in Kenya, have shed light on putative protective mechanisms, suggesting that mucosal immunological factors, such as antiproteases, could be mediating resistance to HIV-1 transmission in the female reproductive tract. Nine protease inhibitors were selected for this study: serpin B4, serpin A1, serpin A3, serpin C1, cystatin A, cystatin B, serpin B13, serpin B1 and α-2-macroglobulin-like-protein 1. We assessed in a pilot study, the activity of these antiproteases with cellular assays and an ex vivo HIV-1 challenge model of human ecto-cervical tissue explants. Preliminary findings with both models, cellular and tissue explants, established an order of inhibitory potency for the mucosal proteins as candidates for pre-exposure prophylaxis when mimicking pre-coital use. Combination of all antiproteases considered in this study was more active than any of the individual mucosal proteins. Furthermore, the migration of cells out of ecto-cervical explants was blocked indicating potential prevention of viral dissemination following amplification of the founder population. These findings constitute the base for further development of these mucosal protease inhibitors for prevention strategies.

A post-mortem analysis of tenofovir, lamivudine, efavirenz and fluconazole penetration in female genital tissues

BACKGROUND

Optimal penetration of anti-infectives in the female genital tract (FGT) is paramount in the treatment and prevention of infectious diseases. While exposure of anti-infectives in lower FGT tissues (e.g. cervix, vagina) has been described, little data exist on upper genital tissues (e.g. ovary, uterus).

METHODS

Autopsies were performed and post-mortem tissues were collected within 24 h of death for female participants with advanced HIV in Uganda (n = 27). Tenofovir, lamivudine, efavirenz and fluconazole concentrations were measured using LC-MS/MS in plasma, ovarian, uterine, cervical and vaginal tissues. Tissue penetration was calculated as tissue-to-plasma concentration ratios (TPRs).

RESULTS

TPRs of tenofovir, lamivudine and fluconazole were highest in vaginal tissue (medians 1.86, 1.83 and 0.94, respectively), while the TPR of efavirenz was highest in ovarian tissue (median 0.65). With cervix as a reference compartment, vaginal TPRs were significantly higher than cervical for all four drugs; TPRs of efavirenz in uterine and ovarian compartments were also significantly higher than cervical. Most of the post-mortem FGT samples had a TPR of greater than 1 for tenofovir and lamivudine, while less than 50% had a TPR of greater than 1 for both efavirenz and fluconazole.

CONCLUSIONS

Penetration of anti-infectives was not homogeneous among the FGT compartments. Approximately 70% of FGT tissues had a TPR of greater than 1 for tenofovir and lamivudine, favouring the prevention of local HIV replication and transmission in the FGT.

Mucosal Responses to Zika Virus Infection in Cynomolgus Macaques

Zika virus (ZIKV) cases continue to be reported, and no vaccine or specific antiviral agent has been approved for the prevention or treatment of infection. Though ZIKV is primarily transmitted by mosquitos, cases of sexual transmission and prolonged viral RNA presence in semen have been reported. In this observational study, we report the mucosal responses to sub-cutaneous and mucosal ZIKV exposure in cynomolgus macaques during acute and late chronic infection. Subcutaneous challenge induced a decrease in the growth factor VEGF in colorectal and cervicovaginal tissues 100 days post-challenge, in contrast to the observed increase in these tissues following vaginal infection. This different pattern was not observed in the uterus, where VEGF was upregulated independently of the challenge route. Vaginal challenge induced a pro-inflammatory profile in all mucosal tissues during late chronic infection. Similar responses were already observed during acute infection in a vaginal tissue explant model of ex vivo challenge. Non-productive and productive infection 100 days post-in vivo vaginal challenge induced distinct proteomic profiles which were characterized by further VEGF increase and IL-10 decrease in non-infected animals. Ex vivo challenge of mucosal explants revealed tissue-specific modulation of cytokine levels during the acute phase of infection. Mucosal cytokine profiles could represent biosignatures of persistent ZIKV infection.

Pre-Clinical Evaluation of Tenofovir and Tenofovir Alafenamide for HIV-1 Pre-Exposure Prophylaxis in Foreskin Tissue

Background: HIV-1 pre-exposure prophylaxis (PrEP) has focused predominantly on protective efficacy in receptive sex, with limited research on the dosing requirements for insertive sex. We pre-clinically assessed the ex vivo pharmacokinetic–pharmacodynamic (PK–PD) profile of tenofovir (TFV) and tenofovir alafenamide (TAF) in foreskin tissue. Methods: Inner and outer foreskin explants were exposed to serial dilutions of TFV or TAF prior to addition of HIV-1_BaL at a high (HVT) or a low viral titer (LVT). Infection was assessed by measurement of p24 in foreskin culture supernatants. TFV, TAF and TFV–diphosphate (TFV–DP) concentrations were measured in tissues, culture supernatants and dosing and washing solutions. Results: Dose–response curves were obtained for both drugs, with greater potency observed against LVT. Inhibitory equivalency mimicking oral dosing was defined between 1 mg/mL of TFV and 15 µg/mL of TAF against HVT challenge. Concentrations of TFV–DP in foreskin explants were approximately six-fold higher after ex vivo dosing with TAF than with TFV. Statistically significant negative linear correlations were observed between explant levels of TFV or TFV–DP and p24 concentrations following HVT. Conclusions: Pre-clinical evaluation of TAF in foreskin explants revealed greater potency than TFV against penile HIV transmission. Clinical evaluation is underway to support this finding.

Ex Vivo Evaluation of Mucosal Responses to Vaccination with ALVAC and AIDSVAX of Non-Human Primates

Non-human primates (NHPs) remain the most relevant challenge model for the evaluation of HIV vaccine candidates; however, discrepancies with clinical trial results have emphasized the need to further refine the NHP model. Furthermore, classical evaluation of vaccine candidates is based on endpoints measured systemically. We assessed the mucosal responses elicited upon vaccination with ALVAC and AIDSVAX using ex vivo Rhesus macaque mucosal tissue explant models. Following booster immunization with ALVAC/AIDSVAX, anti-gp120 HIV-1CM244-specific IgG and IgA were detected in culture supernatant cervicovaginal and colorectal tissue explants, as well as systemically. Despite protection from ex vivo viral challenge, no neutralization was observed with tissue explant culture supernatants. Priming with ALVAC induced distinct cytokine profiles in cervical and rectal tissue. However, ALVAC/AIDSVAX boosts resulted in similar modulations in both mucosal tissues with a statistically significant decrease in cytokines linked to inflammatory responses and lymphocyte differentiation. With ALVAC/AIDSVAX boosts, significant correlations were observed between cytokine levels and specific IgA in cervical explants and specific IgG and IgA in rectal tissue. The cytokine secretome revealed differences between vaccination with ALVAC and ALVAC/AIDSVAX not previously observed in mucosal tissues and distinct from the systemic response, which could represent a biosignature of the vaccine combination.