Durable protection against repeated penile exposures to simian-human immunodeficiency virus by broadly neutralizing antibodies

Preservation of memory B cell homeostasis in an individual producing broadly neutralising antibodies against HIV-1

Immunological determinants favouring emergence of broadly neutralising antibodies are crucial to the development of HIV-1 vaccination strategies. Here, we combined RNAseq and B cell cloning approaches to isolate a broadly neutralising antibody (bnAb) ELC07 from an individual living with untreated HIV-1. Using single particle cryogenic electron microscopy (cryo-EM), we show that the antibody recognises a conformational epitope at the gp120-gp41 interface. ELC07 binds the closed state of the viral glycoprotein causing considerable perturbations to the gp41 trimer core structure. Phenotypic analysis of memory B cell subsets from the ELC07 bnAb donor revealed a lack of expected HIV-1-associated dysfunction, specifically no increase in CD21-/CD27- cells was observed whilst the resting memory (CD21+/CD27+) population appeared preserved despite uncontrolled HIV-1 viraemia. Moreover, single cell transcriptomes of memory B cells from this bnAb donor showed a resting memory phenotype irrespective of the epitope they targeted or their ability to neutralise diverse strains of HIV-1. Strikingly, single memory B cells from the ELC07 bnAb donor were transcriptionally similar to memory B cells from HIV-negative individuals. Our results demonstrate that potent bnAbs can arise without the HIV-1-induced dysregulation of the memory B cell compartment and suggest that sufficient levels of antigenic stimulation with a strategically designed immunogen could be effective in HIV-negative vaccine recipients.

Broadly neutralizing antibody-mediated protection against simian-HIV infection among macaques with vaginal sexually transmitted infections

OBJECTIVE

Sexually transmitted infections (STIs) increase mucosal HIV infection risk and have the potential to reduce preexposure prophylaxis efficacy. Clinical trials of a broadly neutralizing antibody (bNAb) provided proof-of-concept that passive immunization against HIV can be efficacious in people. We sought to evaluate preclinically the protective efficacy of passive bNAb immunization against simian-human immunodeficiency virus (SHIV) infection in the context of concurrent vaginal STIs.

DESIGN

Using a macaque model of combined ulcerative and nonulcerative vaginal STIs caused by Treponema pallidum , Chlamydia trachomatis , and Trichomonas vaginalis , we determined the protection that passively administered bNAb 10-1074 conferred against repeated vaginal SHIV challenges and compared correlates of protection to contemporaneous and historical controls without STIs.

METHODS

Plasma viremia was monitored via RT-qPCR assay. Concentrations of 10-1074 were determined longitudinally in plasma samples via TZM-bl pseudovirus neutralization assay.

RESULTS

Among macaques with vaginal STIs, a single subcutaneous injection of 10-1074 durably protected against vaginal SHIV acquisition, as compared with untreated controls. Interestingly, the median plasma concentration of 10-1074 at the time of SHIV breakthrough among macaques with STIs was significantly higher (10-fold) than that previously observed among 10-1074-treated macaques in the absence of STIs.

CONCLUSION

Passive immunization with 10-1074 conferred significant protection against repeated vaginal SHIV challenges among macaques harboring vaginal STIs. However, our findings suggest that higher bNAb concentrations may be required for prophylaxis when STIs are present. Our findings potentially impact dose selection for the clinical development of bNAbs and highlight the importance of additional preclinical efficacy testing in STI models.

Pharmacology of boosted and unboosted integrase strand transfer inhibitors for two-dose event-driven HIV prevention regimens among men

BACKGROUND

Event-driven HIV prevention strategies are a priority for users who do not require daily pre-exposure prophylaxis (PrEP). Regimens containing integrase strand transfer inhibitors (INSTIs) are under evaluation as alternatives to daily PrEP. To better understand INSTI distribution and inform dosing selection we compared the pharmacology of two-dose boosted elvitegravir and unboosted bictegravir regimens in MSM.

MATERIALS AND METHODS

Blood, rectal and penile secretions and rectal biopsies were collected from 63 HIV-negative MSM aged 18-49 years. Specimens were collected up to 96 h after two oral doses of tenofovir alafenamide and emtricitabine with elvitegravir boosted by cobicistat or unboosted bictegravir given 24 h apart. Antiretroviral drugs were measured by LC-MS.

RESULTS

Mean bictegravir plasma concentrations remained above the 95% protein-adjusted effective concentration 96 h after dosing [273 (95% CI: 164-456) ng/mL] whereas elvitegravir plasma concentrations became undetectable 48 h after the second dose. Bictegravir and elvitegravir reached rectal tissues within 2 h after the first dose, and elvitegravir tissue concentrations [1.07 (0.38-13.51) ng/mg] were greater than bictegravir concentrations [0.27 (0.15-0.70) ng/mg]. Both INSTIs became undetectable in tissues within 96 h. Elvitegravir and bictegravir were not consistently detected in penile secretions.

CONCLUSIONS

Whereas bictegravir plasma concentrations persist at least 4 days after a two-oral-dose HIV prophylaxis regimen, elvitegravir accumulates in mucosal tissues. Differing elvitegravir and bictegravir distribution may result in variable mucosal and systemic antiviral activity and can inform dosing strategies for event-driven HIV prevention.

In vivo engineered B cells secrete high titers of broadly neutralizing anti-HIV antibodies in mice

Transplantation of B cells engineered ex vivo to secrete broadly neutralizing antibodies (bNAbs) has shown efficacy in disease models. However, clinical translation of this approach would require specialized medical centers, technically demanding protocols and major histocompatibility complex compatibility of donor cells and recipients. Here we report in vivo B cell engineering using two adeno-associated viral vectors, with one coding for Staphylococcus aureus Cas9 (saCas9) and the other for 3BNC117, an anti-HIV bNAb. After intravenously injecting the vectors into mice, we observe successful editing of B cells leading to memory retention and bNAb secretion at neutralizing titers of up to 6.8 µg ml^-1. We observed minimal clustered regularly interspaced palindromic repeats (CRISPR)-Cas9 off-target cleavage as detected by unbiased CHANGE-sequencing analysis, whereas on-target cleavage in undesired tissues is reduced by expressing saCas9 from a B cell-specific promoter. In vivo B cell engineering to express therapeutic antibodies is a safe, potent and scalable method, which may be applicable not only to infectious diseases but also in the treatment of noncommunicable conditions, such as cancer and autoimmune disease.

To bnAb or Not to bnAb: Defining Broadly Neutralising Antibodies Against HIV-1

Since their discovery, antibodies capable of broad neutralisation have been at the forefront of HIV-1 research and are of particular interest due to in vivo passive transfer studies demonstrating their potential to provide protection. Currently an exact definition of what is required for a monoclonal antibody to be classed as a broadly neutralising antibody (bnAb) has not yet been established. This has led to hundreds of antibodies with varying neutralisation breadth being studied and has given insight into antibody maturation pathways and epitopes targeted. However, even with this knowledge, immunisation studies and vaccination trials to date have had limited success in eliciting antibodies with neutralisation breadth. For this reason there is a growing need to identify factors specifically associated with bnAb development, yet to do this a set of criteria is necessary to distinguish bnAbs from non-bnAbs. This review aims to define what it means to be a HIV-1 bnAb by comparing neutralisation breadth, genetic features and epitopes of bnAbs, and in the process highlights the challenges of comparing the array of antibodies that have been isolated over the years.

Incorporating the Cluster A and V1V2 Targets into a Minimal Structural Unit of the HIV-1 Envelope to Elicit a Cross-Clade Response with Potent Fc-Effector Functions

The generation of a potent vaccine for the prevention and/or control of HIV-1 has been unsuccessful to date, despite decades of research. Existing evidence from both infected individuals and clinical trials support a role for non-neutralizing or weakly neutralizing antibodies with potent Fc-effector functions in the prevention and control of HIV-1 infection. Vaccination strategies that induce such antibodies have proven partially successful in preventing HIV-1 infection. This is largely thought to be due to the polyclonal response that is induced in a vaccine setting, as opposed to the infusion of a single therapeutic antibody, which is capable of diverse Fc-effector functions and targets multiple but highly conserved epitopes. Here, we build on the success of our inner domain antigen, ID2, which incorporates conformational CD4-inducible (CD4i) epitopes of constant region 1 and 2 (C1C2 or Cluster A), in the absence of neutralizing antibody epitopes, into a minimal structural unit of gp120. ID2 has been shown to induce Cluster A-specific antibodies in a BALB/c mouse model with Fc-effector functions against CD4i targets. In order to generate an immunogen that incorporates both epitope targets implicated in the protective Fc-effector functions of antibodies from the only partially successful human vaccine trial, RV144, we incorporated the V1V2 domain into our ID2 antigen generating ID2-V1V2, which we used to immunize in combination with ID2. Immunized BALB/c mice generated both Cluster A- and V1V2-specific antibodies, which synergized to significantly improve the Fc-mediated effector functions compared to mice immunized with ID2 alone. The sera were able to mediate both antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). We therefore conclude that ID2-V1V2 + ID2 represents a promising vaccine immunogen candidate for the induction of antibodies with optimal Fc-mediated effector functions against HIV-1.

Broadly neutralizing antibody-mediated protection of macaques against repeated intravenous exposures to simian-human immunodeficiency virus

OBJECTIVE

The opioid epidemic has increased parentally acquired HIV infection. To inform the development of a long-acting prevention strategy, we evaluated the protective efficacy of broadly neutralizing antibodies (bNAbs) against intravenous simian-human immunodeficiency virus (SHIV) infection in macaques.

DESIGN

Five cynomolgus macaques were injected once subcutaneously with 10-1074 and 3BNC117 (10 mg each kg-1) and were repeatedly challenged intravenously once weekly with SHIVAD8-EO (130 TCID50), until infection was confirmed via plasma viral load assay. Two control macaques, which received no antibody, were challenged identically.

METHODS

Plasma viremia was monitored via RT-qPCR assay. bNAb concentrations were determined longitudinally in plasma samples via TZM-bl neutralization assays using virions pseudotyped with 10-1074-sensitive (X2088_c9) or 3BNC117-sensitive (Q769.d22) HIV envelope proteins.

RESULTS

Passively immunized macaques were protected against a median of five weekly intravenous SHIV challenges, as compared to untreated controls, which were infected following a single challenge. Of the two bNAbs, 10-1074 exhibited relatively longer persistence in vivo. The median plasma level of 10-1074 at SHIV breakthrough was 1.1 μg ml-1 (range: 0.6-1.6 μg ml-1), whereas 3BNC117 was undetectable. Probit modeling estimated that 6.6 μg ml-1 of 10-1074 in plasma corresponded to a 99% reduction in per-challenge infection probability, as compared to controls.

CONCLUSIONS

Significant protection against repeated intravenous SHIV challenges was observed following administration of 10-1074 and 3BNC117 and was due primarily to 10-1074. Our findings extend preclinical studies of bNAb-mediated protection against mucosal SHIV acquisition and support the possibility that intermittent subcutaneous injections of 10-1074 could serve as long-acting preexposure prophylaxis for persons who inject drugs.

Broadly neutralizing HIV-1 antibody reactivity in HIV tests: implications for diagnostics

OBJECTIVE

Passive immunization with broadly neutralizing antibodies (bNAbs) is under evaluation for HIV prevention. BNAbs target gp120 or gp41, two HIV envelope antigens commonly present in diagnostic tests. Depending on bNAb type and dose administered to humans, serum levels can reach nearly 1 mg/ml and wane over several weeks to months. We investigated the reactivity of bNAbs in HIV serological tests to inform diagnostic testing practices for persons treated with these products.

DESIGN AND METHODS

The antigp120 bNAbs VRCO1, PGT121, PGT145, 3BNC117, 10-1074 and N6 and antigp41 bNAbs 10E8 and 10E8v4 were tested with the laboratory-based Bio-Rad Ag/Ab Combo assay, the point-of-care single-use Determine Combo, OraQuick, Reveal G4, SureCheck, Uni-Gold, INSTI and DPP HIV-1/2 assays, and the supplemental Geenius and HIV-1 Western Blot assays.

RESULTS

At 1 mg/ml, all bNAbs were nonreactive in four screening tests. OraQuick, SureCheck, Reveal G4 and INSTI detected at least two bNAbs each; SureCheck exhibited reactivity to six bNAbs. Geenius was HIV-1 indeterminate (gp160+) with all bNAbs except PGT121, which was HIV antibody-negative. HIV-1 Western Blot was indeterminate (gp41+/gp160+) with 10E8 and 10E8v4 and negative with the remaining bNAbs. There was no correlation between the test antigen construct(s) and bNAb reactivity.

CONCLUSION

We identified a laboratory-based Ag/Ab EIA and three single-use rapid HIV tests that are nonreactive against a panel of bNAbs supporting some diagnostic tests can distinguish HIV-1 infection events among persons receiving bNAb immunoprophylaxis. Evaluation of HIV diagnostic tests prior to clinical use may identify suitable serologic assays for persons administered bNAbs.

Broadly Neutralizing Antibodies for HIV-1 Prevention

Given the absence of an effective vaccine for protection against HIV-1 infection, passive immunization strategies that utilize potent broadly neutralizing antibodies (bnAbs) to block acquisition of HIV-1 are being rigorously pursued in the clinical setting. bnAbs have demonstrated robust protection in preclinical animal models, and several leading bnAb candidates have shown favorable safety and pharmacokinetic profiles when tested individually or in combinations in early phase human clinical trials. Furthermore, passive administration of bnAbs in HIV-1 infected individuals has resulted in prolonged suppression of viral rebound following interruption of combination antiretroviral therapy, and robust antiviral activity when administered to viremic individuals. Recent results from the first efficacy trials testing repeated intravenous administrations of the anti-CD4 binding site bnAb VRC01 have demonstrated positive proof of concept that bnAb passive immunization can confer protection against HIV-1 infection in humans, but have also highlighted the considerable barriers that remain for such strategies to effectively contribute to control of the epidemic. In this review, we discuss the current status of clinical studies evaluating bnAbs for HIV-1 prevention, highlight lessons learned from the recent Antibody Mediated Prevention (AMP) efficacy trials, and provide an overview of strategies being employed to improve the breadth, potency, and durability of antiviral protection.

Lactobacilli Expressing Broadly Neutralizing Nanobodies against HIV-1 as Potential Vectors for HIV-1 Prophylaxis?

In the absence of an active prophylactic vaccine against HIV-1, passively administered, broadly neutralizing antibodies (bnAbs) identified in some chronically infected persons were shown to prevent HIV-1 infection in animal models. However, passive administration of bnAbs may not be suited to prevent sexual HIV-1 transmission in high-risk cohorts, as a continuous high level of active bnAbs may be difficult to achieve at the primary site of sexual transmission, the human vagina with its acidic pH. Therefore, we used Lactobacillus, a natural commensal in the healthy vaginal microbiome, to express bn nanobodies (VHH) against HIV-1 that we reported previously. After demonstrating that recombinant VHHA6 expressed in E. coli was able to protect humanized mice from mucosal infection by HIV-1Bal, we expressed VHHA6 in a soluble or in a cell-wall-anchored form in Lactobacillus rhamnosus DSM14870. This strain is already clinically applied for treatment of bacterial vaginosis. Both forms of VHHA6 neutralized a set of primary epidemiologically relevant HIV-1 strains in vitro. Furthermore, VHHA6 was still active at an acidic pH. Thus, lactobacilli expressing bn VHH potentially represent an attractive vector for the passive immunization of women in cohorts at high risk of HIV-1 transmission.

Persons who inject drugs (PWID) retain functional NK cells, dendritic cell stimulation, and adaptive immune recall responses despite prolonged opioid use

Previous literature suggests that acute opioid use results in the functional impairment of the immune response, thereby decreasing resistance to viral infection. Here, we assessed if innate and adaptive immune responses are compromised ex vivo in persons who inject drugs (PWID) and whether long-term injection drug use may impact host susceptibility to in vitro HIV infection. We measured the frequency, activation state, and functional profile of NK cells, dendritic cells, and CD4+ and CD8+ T cells in low-risk PWID who do not share needles, high-risk needle-sharing PWID, and control donors who did not inject drugs. We also assessed plasma levels of inflammatory markers and CD4+ T cell susceptibility to HIV infection. We observed a significant increase in the amount of sCD14 (P = 0.0023, n = 16) and sCD163 (P = 0.0001, n = 16) in the plasma of PWID compared to controls. Evidence of constitutive activation was noted in PWID as compared to controls with increased CD69 expression in CD56dim NK cells (P = 0.0103, n = 26) and increased CD38 and HLA-DR expression in CD4+ T cells (P = 0.0355, n = 23). However, no innate or adaptive functional differences were detected between PWID and controls, including: NK cell direct or antibody-dependent cellular cytotoxicity poly-functional response, TLR-stimulated dendritic cell/NK crosstalk, CD8+ T cell response to Staphylococcal enterotoxin B or CMV/EBV/FLU peptides, or constitutive or anti-CD3/CD28-stimulated CD4+ T cell infectivity with CCR5-tropic or CXCR4-tropic HIV-1 isolates. Our data indicate that PWID who utilize opioids over as prolonged time frame can retain a functional ex vivo immune response without a measurable increase in CD4+ T cell infectivity suggesting that leukocytes from PWID are not intrinsically more susceptibility to infection with HIV than non-PWID controls.

Glycoengineering of AAV-delivered monoclonal antibodies yields increased ADCC activity

The absence of fucose on asparagine-297 of the human immunoglobulin G (IgG) heavy chain has been shown to enhance antibody-dependent cellular cytotoxicity (ADCC) activity by 10- to 100-fold compared to fucosylated antibody. Our lab is studying the use of adeno-associated virus (AAV) as a vector for the delivery of HIV-specific antibodies for therapeutic purposes. Since the antibody is produced by vector-transduced cells in vivo, current techniques of glycoengineering cannot be utilized. In order to achieve similar enhancement of ADCC with AAV-delivered antibodies, short hairpin RNAs (shRNAs) that target fucosyltransferase-8 (FUT8), were designed, tested, and cloned into AAV vectors used to deliver HIV-specific broadly neutralizing antibodies (bNAbs). Antibodies produced by our glycoengineered-AAV (GE-AAV) vectors were analyzed for fucose content and ADCC. GE-AAV constructs were able to achieve over 80% knockdown of FUT8. Results were confirmed by lectin western blot for α1-6 fucose, which revealed almost a complete absence of fucose on GE-AAV-produced antibodies. GE-AAV-produced antibodies revealed >10-fold enhancement of ADCC, while showing identical neutralization and gp140 trimer binding compared to their fucosylated counterparts. ADCC was enhanced 40- to 60-fold when combined with key Fc mutations known to enhance binding to FcγRIIIA. Our findings define a powerful approach for supercharging AAV-delivered anti-HIV antibodies.