Potent anti-viral activity of a trispecific HIV neutralizing antibody in SHIV-infected monkeys

Broadly neutralizing antibodies (bNAbs) represent an alternative to drug therapy for the treatment of HIV-1 infection. Immunotherapy with single bNAbs often leads to emergence of escape variants, suggesting a potential benefit of combination bNAb therapy. Here, a trispecific bNAb reduces viremia 100- to 1000-fold in viremic SHIV-infected macaques. After treatment discontinuation, viremia rebounds transiently and returns to low levels, through CD8-mediated immune control. These viruses remain sensitive to the trispecific antibody, despite loss of sensitivity to one of the parental bNAbs. Similarly, the trispecific bNAb suppresses the emergence of resistance in viruses derived from HIV-1-infected subjects, in contrast to parental bNAbs. Trispecific HIV-1 neutralizing antibodies, therefore, mediate potent antiviral activity in vivo and may minimize the potential for immune escape.

Anti-HIV-1 Antibodies: An Update

Even after more than 30 years since its discovery, there is no cure for HIV-1 infection. Combination antiretroviral therapy (cART) is currently the only HIV-1 infection management option in clinics. Despite its success in suppressing viral replication and converting HIV-1 from a lethal infection to a chronic and manageable disease, cART treatment is life long and long-term use can result in major drawbacks such as high cost, multiple side effects, and an increase in the development of multidrug-resistant escape mutants. Recently, antibody-based anti-HIV-1 treatment has emerged as a potential alternative therapeutic modality for HIV-1 treatment and cure strategies. These antibody-based anti-HIV-1 treatments comprising either receptor-targeting antibodies or broad neutralizing antibodies (bNAbs) are currently being developed and evaluated in clinical trials. These antibodies have demonstrated potent antiviral effects against multiple strains of HIV-1, and shown promise for prevention, maintenance, and prolonged remission of HIV-1 infection. This review gives an update on the current status of these antibody-based treatments for HIV-1, discusses their mechanism of action and the challenges in developing them, providing insight for their development as novel clinical therapies against HIV-1 infection.

Trispecific antibody targeting HIV-1 and T cells activates and eliminates latently-infected cells in HIV/SHIV infections

Agents that can simultaneously activate latent HIV, increase immune activation and enhance the killing of latently-infected cells represent promising approaches for HIV cure. Here, we develop and evaluate a trispecific antibody (Ab), N6/αCD3-αCD28, that targets three independent proteins: (1) the HIV envelope via the broadly reactive CD4-binding site Ab, N6; (2) the T cell antigen CD3; and (3) the co-stimulatory molecule CD28. We find that the trispecific significantly increases antigen-specific T-cell activation and cytokine release in both CD4+ and CD8+ T cells. Co-culturing CD4+ with autologous CD8+ T cells from ART-suppressed HIV+ donors with N6/αCD3-αCD28, results in activation of latently-infected cells and their elimination by activated CD8+ T cells. This trispecific antibody mediates CD4+ and CD8+ T-cell activation in non-human primates and is well tolerated in vivo. This HIV-directed antibody therefore merits further development as a potential intervention for the eradication of latent HIV infection.

Concordance of immunological events between intrarectal and intravenous SHIVAD8-EO infection when assessed by Fiebig-equivalent staging

Primary HIV-1 infection can be classified into six Fiebig stages based on virological and serological laboratory testing, whereas simian-HIV (SHIV) infection in nonhuman primates (NHPs) is defined in time post-infection, making it difficult to extrapolate NHP experiments to the clinics. We identified and extensively characterized the Fiebig-equivalent stages in NHPs challenged intrarectally or intravenously with SHIVAD8-EO. During the first month post-challenge, intrarectally challenged monkeys were up to 1 week delayed in progression through stages. However, regardless of the challenge route, stages I-II predominated before, and stages V-VI predominated after, peak viremia. Decrease in lymph node (LN) CD4+ T cell frequency and rise in CD8+ T cells occurred at stage V. LN virus-specific CD8+ T cell responses, dominated by degranulation and TNF, were first detected at stage V and increased at stage VI. A similar late elevation in follicular CXCR5+ CD8+ T cells occurred, consistent with higher plasma CXCL13 levels at these stages. LN SHIVAD8-EO RNA+ cells were present at stage II, but appeared to decline at stage VI when virions accumulated in follicles. Fiebig-equivalent staging of SHIVAD8-EO infection revealed concordance of immunological events between intrarectal and intravenous infection despite different infection progressions, and can inform comparisons of NHP studies with clinical data.

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.