HIV-1-Based Virus-like Particles that Morphologically Resemble Mature, Infectious HIV-1 Virions

Abstract

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.

An integrin/MFG-E8 shuttle loads HIV-1 viral-like particles onto follicular dendritic cells in mouse lymph node

“…Multiple reports have demonstrated that HIV-1 VLPs can induce strong antibody responses in small animal models and macaques (Tong et al, 2014), (Buonaguro et al, 2012). Furthermore, expertise in the generation and usage of VLPs is evolving towards the goal of producing a safe mimic of real HIV-1 virions (Gonelli et al, 2019). However, care in the evaluation of HIV-1 VLPs vaccine studies is needed.…”

Genetic Co-Administration of Soluble PD-1 Ectodomains Modifies Immune Responses against Influenza A Virus Induced by DNA Vaccination

“…One reason for the observed variations in modulatory activities between soluble PD-1 and PD-L1 adjuvants could stem from the form of the encoded antigens. The application of DNA vaccines against HIV-1 may lead to production and secretion of HIV VLPs in the muscle tissues in situ [ 20 , 49 , 50 ]. In vitro, co-transfection of 293T cells with HIV-1 Env and Gag plasmids used for the HIV-1 DNA vaccine led to VLP production [ 20 ].…”

Immunogenicity of HIV-1-Based Virus-Like Particles with Increased Incorporation and Stability of Membrane-Bound Env

“…VLP-expression vectors producing immature VLPs (iVLPs) (pCMV-AEp55B) or mVLPs (pCMV-AEB.NCΔRT) bearing WT AD8 Env, and Env-deficient mVLPs (mVLP Δenv) (pCMV-AEΔB.NCΔRT) were previously described [ 57 ]. A non-particle-producing control VLP vector (ΔVLP) was generated by introducing nonsense mutations at the Gag start codon and all potential initiation codons within p17 and at the beginning of p24 (M1X, M31X, M142X) and excising part of the p24 domain (illustrated summary in Figure S3A ).…”

“…We previously described a vector expressing mature (proteolytically cleaved Gag core) HIV-1 VLPs [ 57 ] predicted to better trigger B-cell-receptor cross-linking, since core maturation facilitates surface Env clustering on virions [ 58 , 59 ]. The noninfectious mature VLP (mVLP) expression cassette lacked HIV-1 promoters, enzyme functions needed for host genome integration, and accessory proteins Vif, Vpr, and Nef [ 57 ]. We determined the minimal Gag and protease domain sequences required for efficient particle expression and maturation, and generated VLPs with similar morphology, size, and function (in terms of target-cell fusion) when compared to fully infectious, mature virions.…”

“…The immunogenicity of these VLPs was examined in mice, with the aim of inducing humoral responses capable of blocking virus infection. The Env expression cassette within a single HIV-1 VLP-producing vector developed previously [ 57 ] was modified within the TM and CT domains to increase Env incorporation into VLPs. Additionally, the introduction of a gp120-gp41 disulfide linkage in combination with a gp41 I559P mutation (SOSIP) stabilized the Env conformation and improved its antigenicity, as demonstrated by increased binding to bNAbs, particularly those targeting quaternary epitopes, and reduced interaction with non-neutralizing antibodies.…”