Strategies to target the central nervous system HIV reservoir

PURPOSE OF THE REVIEW

The central nervous system (CNS) is an hotspot for HIV persistence and may be a major obstacle to overcome for curative strategies. The peculiar anatomical, tissular and cellular characteristics of the HIV reservoir in the CNS may need to be specifically addressed to achieve a long-term HIV control without ART. In this review, we will discuss the critical challenges that currently explored curative strategies may face in crossing the blood-brain barrier (BBB), targeting latent HIV in brain-resident myeloid reservoirs, and eliminating the virus without eliciting dangerous neurological adverse events.

RECENT FINDINGS

Latency reversing agents (LRA), broadly neutralizing monoclonal antibodies (bNabs), chimeric antigen receptor (CAR) T-cells, and adeno-associated virus 9-vectored gene-therapies cross the BBB with varying efficiency. Although brain penetration is poor for bNAbs, viral vectors for in vivo gene-editing, certain LRAs, and CAR T-cells may reach the cerebral compartment more efficiently. All these approaches, however, may encounter difficulties in eliminating HIV-infected perivascular macrophages and microglia. Safety, including local neurological adverse effects, may also be a concern, especially if high doses are required to achieve optimal brain penetration and efficient brain cell targeting.

SUMMARY

Targeting the CNS remains a potential problem for the currently investigated HIV curing strategies. In vivo evidence on CNS effectiveness is limited for most of the investigated strategies, and additional studies should be focused on evaluating the interplay between the cerebral HIV reservoir and treatment aiming to achieve an ART-free cure.

Semen enhances transmitted/founder HIV-1 infection and only marginally reduces antiviral activity of broadly neutralizing antibodies

Topically applied microbicides may play a critical role in preventing sexual transmission of human immunodeficiency virus type 1 (HIV-1); however, their efficacy can be compromised by amyloid fibrils present in semen, which significantly increase HIV-1 infectivity. This phenomenon may have contributed to the failure of most microbicide candidates in clinical settings. Understanding the impact of semen on microbicide effectiveness is thus crucial. In our study, we evaluated the influence of semen on the neutralizing activity of broadly neutralizing antibodies (bNAbs), including PG16, PGT121, 10-1074, 3BNC117, and VRC01, which are potential microbicide candidates. We found that semen enhances infection of HIV-1 transmitted/founder viruses but only marginally affects the neutralizing activity of tested antibodies, suggesting their potential for microbicide application. Our findings underscore the need to consider semen-mediated enhancement when evaluating and developing microbicides and highlight the potential of incorporating HIV-1 bNAbs in formulations to enhance efficacy and mitigate HIV-1 transmission during sexual encounters.IMPORTANCEThis study examined the impact of semen on the development of microbicides, substances used to prevent the transmission of HIV-1 during sexual activity. Semen contains certain components that can render the virus more infectious, posing a challenge to microbicide effectiveness. Researchers specifically investigated the effect of semen on a group of powerful antibodies called broadly neutralizing antibodies, which can neutralize a large spectrum of different HIV-1 variants. The results revealed that semen only had a minimal effect on the antibodies' ability to neutralize the virus. This is promising because it suggests that these antibodies could still be effective in microbicides, even in the presence of semen. Understanding this interaction is crucial for developing better strategies to prevent HIV-1 transmission. By incorporating the knowledge gained from this study, scientists can now focus on creating microbicides that consider the impact of semen, bringing us closer to more effective prevention methods.

Phase 1 trial evaluating safety and pharmacokinetics of HIV-1 broadly neutralizing mAbs 10E8VLS and VRC07-523LS

BACKGROUNDBroadly neutralizing monoclonal antibodies (bNAbs) represent a promising strategy for HIV-1 immunoprophylaxis and treatment. 10E8VLS and VRC07-523LS are bNAbs that target the highly conserved membrane-proximal external region (MPER) and the CD4-binding site of the HIV-1 viral envelope glycoprotein, respectively.METHODSIn this phase 1, open-label trial, we evaluated the safety and pharmacokinetics of 5 mg/kg 10E8VLS administered alone, or concurrently with 5 mg/kg VRC07-523LS, via s.c. injection to healthy non-HIV-infected individuals.RESULTSEight participants received either 10E8VLS alone (n = 6) or 10E8VLS and VRC07-523LS in combination (n = 2). Five (n = 5 of 8, 62.5%) participants who received 10E8VLS experienced moderate local reactogenicity, and 1 participant (n = 1/8, 12.5%) experienced severe local reactogenicity. Further trial enrollment was stopped, and no participant received repeat dosing. All local reactogenicity resolved without sequelae. 10E8VLS retained its neutralizing capacity, and no functional anti-drug antibodies were detected; however, a serum t1/2 of 8.1 days was shorter than expected. Therefore, the trial was voluntarily stopped per sponsor decision (Vaccine Research Center, National Institute of Allergy and Infectious Diseases [NIAID], NIH). Mechanistic studies performed to investigate the underlying reason for the reactogenicity suggest that multiple mechanisms may have contributed, including antibody aggregation and upregulation of local inflammatory markers.CONCLUSION10E8VLS resulted in unexpected reactogenicity and a shorter t1/2 in comparison with previously tested bNAbs. These studies may facilitate identification of nonreactogenic second-generation MPER-targeting bNAbs, which could be an effective strategy for HIV-1 immunoprophylaxis and treatment.TRIAL REGISTRATIONClinicaltrials.gov, accession no. NCT03565315.FUNDINGDivision of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH.

Development of AAV-delivered broadly neutralizing anti-human ACE2 antibodies against SARS-CoV-2 variants

The ongoing evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), resulting in the emergence of new variants that are resistant to existing vaccines and therapeutic antibodies, has raised the need for novel strategies to combat the persistent global COVID-19 epidemic. In this study, a monoclonal anti-human angiotensin-converting enzyme 2 (hACE2) antibody, ch2H2, was isolated and humanized to block the viral receptor-binding domain (RBD) binding to hACE2, the major entry receptor of SARS-CoV-2. This antibody targets the RBD-binding site on the N terminus of hACE2 and has a high binding affinity to outcompete the RBD. In vitro, ch2H2 antibody showed potent inhibitory activity against multiple SARS-CoV-2 variants, including the most antigenically drifted and immune-evading variant Omicron. In vivo, adeno-associated virus (AAV)-mediated delivery enabled a sustained expression of monoclonal antibody (mAb) ch2H2, generating a high concentration of antibodies in mice. A single administration of AAV-delivered mAb ch2H2 significantly reduced viral RNA load and infectious virions and mitigated pulmonary pathological changes in mice challenged with SARS-CoV-2 Omicron BA.5 subvariant. Collectively, the results suggest that AAV-delivered hACE2-blocking antibody provides a promising approach for developing broad-spectrum antivirals against SARS-CoV-2 and potentially other hACE2-dependent pathogens that may emerge in the future.

Replacement of Antiretroviral Therapy with HIV Broadly Neutralizing Antibodies to Maximize the Effectiveness of Chemotherapy in HIV Patients with Lung Cancer

Non-small cell lung cancer (NSCLC) is the most fatal non-AIDS defining cancer in people living with HIV (PWH) on antiretroviral therapy (ART). Treatment of malignancies in PWH requires concomitant cancer therapy and ART, which can lead to potential drug-drug interactions (DDIs) and overlapping toxicities. In this study, we hypothesize that replacement of ART with HIV broadly neutralizing antibodies (bNAbs) during cancer chemotherapy (chemo) may maintain HIV suppression and tumor inhibition while minimizing DDIs and overlapping toxicities. We compared HIV suppression, tumor inhibition, and toxicity between conventional treatment (ART plus chemo) and a new modality (bNAbs plus chemo) in humanized mice. Humanized mice infected with HIVYU2 and xenografted with human NSCLC A549 cells were treated with NSCLC chemo (cisplatin and gemcitabine) and first-line ART (dolutegravir, tenofovir disoproxil difumarate, and emtricitabine) or bNAbs (N49P9.6-FR and PGT 121) at human equivalent drug doses. We monitored plasma HIV RNA, tumor volume, and toxicities over five cycles of chemo. We found that chemo plus ART or bNAbs were equally effective at maintaining suppression of HIV viremia and tumor growth. Comparative analysis showed that mice on ART and chemo had significant reductions in body weight and significant increases in plasma creatinine concentrations compared with mice on bNAbs and chemo, which suggests that a combination of bNAbs and chemo produces less renal toxicity than an ART and chemo combination. These data suggest that bNAb therapy during concomitant chemo may be an improved treatment option over ART for PWH and NSCLC, and possibly other cancers, because bNAbs maintain HIV suppression while minimizing DDIs and toxicities.

Nanodepots Encapsulating a Latency Reversing Agent and Broadly Neutralizing Antibody Enhance Natural Killer Cell Cytotoxicity Against an in vitro Model of Latent HIV

Purpose

Current antiretroviral therapies (ART) for human immunodeficiency virus (HIV) are not curative, as the virus persists in latent reservoirs, requiring lifelong adherence to ART and increasing the risk of co-morbidities. "Shock and kill" approaches to reactivate HIV from latent reservoirs followed by administration of anti-HIV drugs represent a promising strategy for eradicating latent HIV. To achieve effective shock and kill, we describe a strategy to eradicate the HIV reservoir that combines latency reversing agents (LRAs), broadly neutralizing antibodies (bnAbs), and natural killer (NK) cells. This strategy utilizes a polymer nanodepot (ND) that co-encapsulates the LRA and bnAb to reactivate latent infection and elicit enhanced cytotoxicity from co-administered NK cells.

Methods

Poly(lactic-co-glycolic acid) (PLGA) NDs were synthesized using the nanoprecipitation method to co-encapsulate an LRA (TNF-α) and a bnAb (3BNC117) (TNF-α-3BNC117-NDs). ACH-2 cells were used as a cellular model of latent HIV infection. An NK92 subline, genetically modified to constitutively express the Fc receptor CD16, was administered to ACH-2 cells in combination with TNF-α-3BNC117-NDs. ACH-2 cell death and extracellular p24 were measured via flow cytometry and ELISA, respectively.

Results

Stable PLGA NDs co-encapsulated TNF-α and 3BNC117 with high efficiencies and released these agents in physiological conditions. NK92 phenotype remained similar in the presence of TNF-α-3BNC117-NDs. TNF-α released from NDs efficiently reactivated HIV in ACH-2 cells, as measured by a 3.0-fold increase in the frequency of intracellular p24 positive cells. Released 3BNC117 neutralized and bound reactivated virus, targeting 57.5% of total ACH-2 cells. Critically, TNF-α-3BNC117-NDs significantly enhanced NK92 cell-mediated killing of ACH-2 cells (1.9-fold) and reduced extracellular levels of p24 to baseline.

Conclusion

These findings suggest the therapeutic potential of our novel ND-based tripartite strategy to reactivate HIV from latently infected cells, generate an HIV-specific site for bnAb binding, and enhance the killing of reactivated HIV-infected target cells by NK92 cells.

Broadly neutralizing antibodies and long-acting antiretroviral drugs as treatments for HIV

PURPOSE OF REVIEW

To discuss progress and challenges in the development of antiretroviral regimens that combine broadly neutralizing antibodies (bNAbs) and long-acting (LA) small-molecule antiretroviral drugs (ARVs).

RECENT FINDINGS

Data are extremely limited, with results from only a single phase 1a clinical trial reported to date. That study, a combination of lenacapavir plus the bNAbs teropavimab and zinlirvimab, maintained viral suppression over 26 weeks in 18 of 20 participants. A second pilot study, ACTG A5357, which tests the safety and virologic efficacy of the combination of LA injectable cabotegravir with the bNAb VRC07-523LS is fully enrolled; results are expected in the second half of 2023.

SUMMARY

The development of regimens that combine bNAbs and LA ARVs has been challenging. Both agents need similar half-lives in order to harmonize dosing schedules. In addition, the need to perform bNAb susceptibility testing to assure activity of the bNAb in order to protect against the risk of developing resistance to the LA ARV has slowed enrollment into trials and poses substantial logistical challenges to widespread adoption of these combinations should they prove safe and effective. Improvements in manufacture that reduce the cost of goods and advances in delivery systems are needed to ensure equitable access to these regimens.

Divide and conquer: broadly neutralizing antibody combinations for improved HIV-1 viral coverage

PURPOSE OF REVIEW

Successful HIV-1 prevention and therapy will require broad and potent coverage of within-host and global viral diversity. Broadly neutralizing antibody (bNAb) combination and multispecific therapeutics provide an opportunity to meet this challenge due to the complementary activity of individual antibody components. Here, we review the principles and applications of this concept.

RECENT FINDINGS

The Antibody Mediated Prevention (AMP) trials have demonstrated the high bar for neutralization potency and breadth that bNAb-mediated prevention modalities will need to achieve to have a meaningful impact on the HIV-1 epidemic. Additional clinical studies have recently shown that an even higher bar may be required for therapeutic inhibition of the diverse within-host quasispecies present in viremic and aviremic people with HIV-1 (PWH). We discuss how the complementarity of bNAbs in terms of neutralization profiles, resistance mutations and coverage of within-host quasispecies may overcome these stringent requirements and lead to effective bNAb combination or multispecific antibody based prophylactic and therapeutic strategies.

SUMMARY

The design of next-generation bNAb-based combination or multispecific therapeutics for the prevention and/or treatment of HIV-1 infection will need to leverage the complementarity of component bNAbs to maximize the potency and breadth that will be required for clinical success.

Broad cross-reactivity across sarbecoviruses exhibited by a subset of COVID-19 donor-derived neutralizing antibodies

Many anti-severe acute respiratory syndrome coronavirus 2 (anti-SARS-CoV-2) neutralizing antibodies target the angiotensin-converting enzyme 2 (ACE2) binding site on viral spike receptor-binding domains (RBDs). Potent antibodies recognize exposed variable epitopes, often rendering them ineffective against other sarbecoviruses and SARS-CoV-2 variants. Class 4 anti-RBD antibodies against a less-exposed, but more-conserved, cryptic epitope could recognize newly emergent zoonotic sarbecoviruses and variants, but they usually show only weak neutralization potencies. Here, we characterize two class 4 anti-RBD antibodies derived from coronavirus disease 2019 (COVID-19) donors that exhibit breadth and potent neutralization of zoonotic coronaviruses and SARS-CoV-2 variants. C118-RBD and C022-RBD structures reveal orientations that extend from the cryptic epitope to occlude ACE2 binding and CDRH3-RBD main-chain H-bond interactions that extend an RBD β sheet, thus reducing sensitivity to RBD side-chain changes. A C118-spike trimer structure reveals rotated RBDs that allow access to the cryptic epitope and the potential for intra-spike crosslinking to increase avidity. These studies facilitate vaccine design and illustrate potential advantages of class 4 RBD-binding antibody therapeutics.

Broadly neutralizing antibodies potently inhibit cell-to-cell transmission of semen leukocyte-derived SHIV162P3

BACKGROUND

HIV-1 sexual transmission occurs mostly through infected semen, which contains both free virions and infected leukocytes. Transmission initiated by infected cells has been shown by several in vitro and in vivo studies and a reduced capacity of broadly neutralizing antibodies (bNAbs) to inhibit cell-to-cell transmission has also been reported. However, due to limitations of available experimental models, there is yet no clarity to which extend bNAbs can prevent transmission mediated by semen leukocytes.

METHODS

We developed a novel in vitro assay to measure cell-cell transmission that makes use of splenocytes or CD45+ semen leukocytes collected from acutely SHIV162P3-infected cynomolgus macaques. A panel of 11 bNAbs was used either alone or in combination to assess their inhibitory potential against both cell-free and cell-cell infection.

FINDINGS

Splenocytes and semen leucocytes displayed a similar proportion of CD4+T-cell subsets. Either cell type transferred infection in vitro to target TZM-bl cells and PBMCs. Moreover, infection of macaques was achieved following intravaginal challenge with splenocytes. The anti-N-glycans/V3 loop bNAb 10-1074 was highly efficient against cell-associated transmission mediated by infected spleen cells and its potency was maintained when transmission was mediated by CD45+ semen leukocytes.

INTERPRETATION

These results support the use of bNAbs in preventative or therapeutic studies aiming to block transmission events mediated not only by free viral particles but also by infected cells. Our experimental system could be used to predict in vivo efficacy of bNAbs.

FUNDING

This work was funded by the ANRS and the European Commission.

Fully Human Monoclonal Antibodies Effectively Neutralizing Botulinum Neurotoxin Serotype B

Botulinum neurotoxin (BoNT) is the most potent natural toxin known. Of the seven BoNT serotypes (A to G), types A, B, E, and F cause human botulism. Treatment of human botulism requires the development of effective toxin-neutralizing antibodies without side effects such as serum sickness and anaphylaxis. In this study, we generated fully human monoclonal antibodies (HuMAbs) against serotype B BoNT (BoNT/B1) using a murine–human chimera fusion partner cell line named SPYMEG. Of these HuMAbs, M2, which specifically binds to the light chain of BoNT/B1, showed neutralization activity in a mouse bioassay (approximately 10 i.p. LD₅₀/100 µg of antibody), and M4, which binds to the C-terminal of heavy chain, showed partial protection. The combination of two HuMAbs, M2 (1.25 µg) and M4 (1.25 µg), was able to completely neutralize BoNT/B1 (80 i.p. LD₅₀) with a potency greater than 80 i.p. LD₅₀/2.5 µg of antibodies, and was effective both prophylactically and therapeutically in the mouse model of botulism. Moreover, this combination showed broad neutralization activity against three type B subtypes, namely BoNT/B1, BoNT/B2, and BoNT/B6. These data demonstrate that the combination of M2 and M4 is promising in terms of a foundation for new human therapeutics for BoNT/B intoxication.

IgG Fc-binding motif-conjugated HIV-1 fusion inhibitor exhibits improved potency and in vivo half-life: Potential application in combination with broad neutralizing antibodies

The clinical application of conventional peptide drugs, such as the HIV-1 fusion inhibitor enfuvirtide, is limited by their short half-life in vivo. To overcome this limitation, we developed a new strategy to extend the in vivo half-life of a short HIV-1 fusion inhibitory peptide, CP24, by fusing it with the human IgG Fc-binding peptide (IBP). The newly engineered peptide IBP-CP24 exhibited potent and broad anti-HIV-1 activity with IC50 values ranging from 0.2 to 173.7 nM for inhibiting a broad spectrum of HIV-1 strains with different subtypes and tropisms, including those resistant to enfuvirtide. Most importantly, its half-life in the plasma of rhesus monkeys was 46.1 h, about 26- and 14-fold longer than that of CP24 (t1/2 = 1.7 h) and enfuvirtide (t1/2 = 3 h), respectively. IBP-CP24 intravenously administered in rhesus monkeys could not induce significant IBP-CP24-specific antibody response and it showed no obvious in vitro or in vivo toxicity. In the prophylactic study, humanized mice pretreated with IBP-CP24 were protected from HIV-1 infection. As a therapeutic treatment, coadministration of IBP-CP24 and normal human IgG to humanized mice with chronic HIV-1 infection resulted in a significant decrease of plasma viremia. Combining IBP-CP24 with a broad neutralizing antibody (bNAb) targeting CD4-binding site (CD4bs) in gp120 or a membrane proximal external region (MPER) in gp41 exhibited synergistic effect, resulting in significant dose-reduction of the bNAb and IBP-CP24. These results suggest that IBP-CP24 has the potential to be further developed as a new HIV-1 fusion inhibitor-based, long-acting anti-HIV drug that can be used alone or in combination with a bNAb for treatment and prevention of HIV-1 infection.

Safety, pharmacokinetics, and immunogenicity of the combination of the broadly neutralizing anti-HIV-1 antibodies 3BNC117 and 10-1074 in healthy adults: A randomized, phase 1 study

BACKGROUND

Additional forms of pre-exposure prophylaxis are needed to prevent HIV-1 infection. 3BNC117 and 10-1074 are broadly neutralizing anti-HIV-1 antibodies that target non-overlapping epitopes on the HIV-1 envelope. We investigated the safety, tolerability, pharmacokinetics, and immunogenicity of the intravenous administration of the combination of 3BNC117 and 10-1074 in healthy adults.

METHODS

This randomized, double-blind, placebo-controlled, single center, phase 1 study enrolled healthy adults aged 18-65 years to receive one infusion of 3BNC117 immediately followed by 10-1074 at 10 mg/kg, three infusions of 3BNC117 followed by 10-1074 at 3 mg/kg or 10 mg/kg every 8 weeks, or placebo infusions. The primary outcomes were safety and pharmacokinetics. This trial is registered with ClinicalTrials.gov, number NCT02824536.

FINDINGS

Twenty-four participants were enrolled in a 3:1 ratio to receive the study products or placebo. The combination of 3BNC117 and 10-1074 was safe and generally well tolerated. There were no serious adverse events considered related to the infusions. The mean elimination half-lives of 3BNC117 and 10-1074 were 16.4 ± 4.6 days and 23.0 ± 5.4 days, respectively, similar to what was observed in previous studies in which each antibody was administered alone. Anti-drug antibody responses were rare and without evidence of related adverse events or impact on elimination kinetics.

INTERPRETATION

Single and repeated doses of the combination of 3BNC117 and 10-1074 were well tolerated in healthy adults. These data support the further development of the combination of 3BNC117 and 10-1074 as a long-acting injectable form of pre-exposure prophylaxis for the prevention of HIV-1 infection.

Staphylococcus aureus drives expansion of low-density neutrophils in diabetic mice

Diabetic individuals are at considerable risk for invasive infection by Staphylococcus aureus, however, the mechanisms underlying this enhanced susceptibility to infection are unclear. We observed increased mortality following i.v. S. aureus infection in diabetic mice compared with nondiabetic controls, correlating with increased numbers of low-density neutrophils (LDNs) and neutrophil extracellular traps (NETs). LDNs have been implicated in the inflammatory pathology of diseases such as lupus, given their release of large amounts of NETs. Our goal was to describe what drives LDN increases during S. aureus infection in the diabetic host and mechanisms that promote increased NET production by LDNs. LDN development is dependent on TGF-β, which we found to be more activated in the diabetic host. Neutralization of TGF-β, or the TGF-β-activating integrin αvβ8, reduced LDN numbers and improved survival during S. aureus infection. Targeting S. aureus directly with MEDI4893*, an α toxin-neutralizing monoclonal antibody, blocked TGF-β activation, reduced LDNs and NETs, and significantly improved survival. A comparison of gene and protein expression in high-density neutrophils and LDNs identified increased GPCRs and elevated phosphatase and tensin homolog (PTEN) in the LDN subset. Inhibition of PTEN improved the survival of infected diabetic mice. Our data identify a population of neutrophils in infected diabetic mice that correlated with decreased survival and increased NET production and describe 3 therapeutic targets, a bacterial target and 2 host proteins, that prevented NET production and improved survival.