Objective: The objective of this study is to determine the breadth of HIV-1 Env-specific antibody-dependent cellular cytotoxicity (ADCC) in HIV controllers and HIV progressors with a view to design globally relevant HIV vaccines. Design: The breadth of ADCC towards four major HIV-1 Env subtypes was measured in vitro for 11 HIV controllers and 11 HIV progressors. Methods: Plasma from 11 HIV controllers (including long-term slow progressors, viremic controllers, elite controller and posttreatment controller) and 11 HIV progressors, mostly infected with HIV-1 subtype B, was analysed for ADCC responses. ADCC assays were performed against 10 HIV-1 gp120 and 8 gp140 proteins from four major HIV-1 subtypes (A, B, C and E) and 3 glycosylation-mutant gp140 proteins. Results: ADCC-mediated natural killer cell activation was significantly broader (P = 0.02) and of higher magnitude (P < 0.001) in HIV controllers than in HIV progressors. HIV controllers also showed significantly higher magnitude of ADCC-mediated killing of Env-coated target cells than HIV progressors to both HIV-1 subtype B and the heterologous subtype E gp140 (P = 0.001). We found good ADCC reactivity to subtype B and E Envs, less cross-reactivity to subtype A and minimal cross-reactivity to subtype C Envs. Glycosylation-dependent ADCC epitopes comprise a significant proportion of the total Env-specific ADCC response, as evident from the reduction in ADCC to nonglycosylated form of HIV-1 gp140 (P = 0.004). Conclusion: HIV controllers have robust ADCC responses that recognize a broad range of HIV-1 Env. Glycosylation of Env was found to be important for recognition of ADCC epitopes. Identifying conserved ADCC epitopes will assist in designing globally relevant ADCC-based HIV vaccines.

A prophylactic vaccine eliciting both broad neutralizing antibodies (bNAbs) to the HIV-1 envelope glycoprotein (Env) and strong T cell responses would be optimal for preventing HIV-1 transmissions. Replication incompetent HIV-1 virus-like particles (VLPs) offer the opportunity to present authentic-structured, virion-associated Env to elicit bNAbs, and also stimulate T cell responses. Here, we optimize our DNA vaccine plasmids as VLP expression vectors for efficient Env incorporation and budding. The original vector that was used in human trials inefficiently produced VLPs, but maximized safety by inactivating RNA genome packaging, enzyme functions that are required for integration into the host genome, and deleting accessory proteins Vif, Vpr, and Nef. These original DNA vaccine vectors generated VLPs with incomplete protease-mediated cleavage of Gag and were irregularly sized. Mutations to restore function within the defective genes revealed that several of the reverse transcriptase (RT) deletions mediated this immature phenotype. Here, we made efficient budding, protease-processed, and mature-form VLPs that resembled infectious virions by introducing alternative mutations that completely removed the RT domain, but preserved most other safety mutations. These VLPs, either expressed from DNA vectors in vivo or purified after expression in vitro, are potentially useful immunogens that can be used to elicit antibody responses that target Env on fully infectious HIV-1 virions.

Soluble "SOSIP"-stabilized envelope (Env) trimers are promising HIV-vaccine immunogens. However, they induce high-titer responses against the glycan-free trimer base, which is occluded on native virions. To delineate the effect on base responses of priming with immunogens targeting the fusion peptide (FP) site of vulnerability, here, we quantify the prevalence of trimer-base antibody responses in 49 non-human primates immunized with various SOSIP-stabilized Env trimers and FP-carrier conjugates. Trimer-base responses account for ∼90% of the overall trimer response in animals immunized with trimer only, ∼70% in animals immunized with a cocktail of SOSIP trimer and FP conjugate, and ∼30% in animals primed with FP conjugates before trimer immunization. Notably, neutralization breadth in FP-conjugate-primed animals correlates inversely with trimer-base responses. Our data provide methods to quantify the prevalence of trimer-base responses and reveal that FP-conjugate priming, either alone or as part of a cocktail, can reduce the trimer-base response and improve the neutralization outcome.

An optimal prophylactic vaccine to prevent human immunodeficiency virus (HIV-1) transmission should elicit protective antibody responses against the HIV-1 envelope glycoprotein (Env). Replication-incompetent HIV-1 virus-like particles (VLPs) offer the opportunity to present virion-associated Env with a native-like structure during vaccination that closely resembles that encountered on infectious virus. Here, we optimized the incorporation of Env into previously designed mature-form VLPs (mVLPs) and assessed their immunogenicity in mice. The incorporation of Env into mVLPs was increased by replacing the Env transmembrane and cytoplasmic tail domains with those of influenza haemagglutinin (HA-TMCT). Furthermore, Env was stabilized on the VLP surface by introducing an interchain disulfide and proline substitution (SOSIP) mutations typically employed to stabilize soluble Env trimers. The resulting mVLPs efficiently presented neutralizing antibody epitopes while minimizing exposure of non-neutralizing antibody sites. Vaccination of mice with mVLPs elicited a broader range of Env-specific antibody isotypes than Env presented on immature VLPs or extracellular vesicles. The mVLPs bearing HA-TMCT-modified Env consistently induced anti-Env antibody responses that mediated modest neutralization activity. These mVLPs are potentially useful immunogens for eliciting neutralizing antibody responses that target native Env epitopes on infectious HIV-1 virions.

Broadly neutralizing antibodies (bNAbs) show potential to prevent human immunodeficiency virus (HIV-1) infection in humans¹. However, there are limited data on the antibody concentrations required to prevent infection. Clinical trials of bNAb prophylaxis have demonstrated partial efficacy², but the sampling frequency typically does not allow precise timing of infection events and concurrent antibody levels. Here, using simian immunodeficiency virus (SIV) infection of rhesus macaques, we show that although potent bNAbs can delay the onset of acute viremia, subclinical infections occur while bNAb levels remain high. Serial SIV challenge of monkeys given partially and fully neutralizing bNAbs revealed that ‘viral blips’—low and transient plasma viremia—often occur while serum bNAb concentrations are well above currently accepted protective levels. To understand the precise timing of the infections resulting in such blips, we performed plasma viral sequencing on monkeys that were serially challenged with genetically barcoded SIV after bNAb administration. These analyses showed that subclinical infections occurred in most animals that were given potent bNAb prophylaxis. These subclinical infections occurred while antibody concentrations were 2- to 400-fold higher than the levels required to prevent fully viremic breakthrough infection. This study demonstrates that immunoprophylaxis can mask subclinical infections, which may affect the interpretation of prophylactic HIV-1 bNAb clinical trials.

BST-2 (tetherin, CD317, HM1.24) restricts virus growth by tethering enveloped viruses to the cell surface. The role of BST-2 during influenza A virus infection (IAV) is controversial. Here, we assessed the capacity of endogenous BST-2 to restrict IAV in primary murine cells. IAV infection increased BST-2 surface expression by primary macrophages, but not alveolar epithelial cells (AEC). BST-2-deficient AEC and macrophages displayed no difference in susceptibility to IAV infection relative to wild type cells. Furthermore, BST-2 played little role in infectious IAV release from either AEC or macrophages. To examine BST-2 during IAV infection in vivo, we infected BST-2-deficient mice. No difference in weight loss or in viral loads in the lungs and/or nasal tissues were detected between BST-2-deficient and wild type animals. This study rules out a major role for endogenous BST-2 in modulating IAV in the mouse model of infection.