Peptide-MHC multimer-based monitoring of CD8 T-cells in HIV-1 infection and AIDS vaccine development

Conserved multiepitope vaccine constructs: A potent HIV-1 therapeutic vaccine in clinical trials

Despite the success of Antiretroviral Therapy (ART) in preventing HIV-1-associated clinical progression to AIDS, it is unable to eliminate the viral reservoirs and eradicate the HIV-1 infection. Therapeutic vaccination is an alternative approach to alter the HIV-1 infection course. It can induce effective HIV-1-specific immunity to control viremia and eliminate the need for lifelong ART. Immunological data from spontaneous HIV-1 controllers have shown that cross-reactive T-cell responses are the key immune mechanism in HIV-1 control. Directing these responses toward preferred HIV-1 epitopes is a promising strategy in therapeutic vaccine settings. Designing novel immunogens based on the HIV-1 conserved regions containing a wide range of critical T- and B-cell epitopes of the main viral antigens (conserved multiepitope approaches) supplies broad coverage of global diversity in HIV-1 strains and Human Leukocyte Antigen (HLA) alleles. It can also prevent immune induction to undesirable decoy epitopes theoretically. The efficacy of different novel HIV-1 immunogens based on the conserved and/or functional protective site of HIV-1 proteome has been evaluated in multiple clinical trials. Most of these immunogens were generally safe and able to induce potent HIV-1-specific immunity. However, despite these findings, several candidates have demonstrated limited efficacy in viral replication control. In this study, we used the PubMed and ClinicalTrial.gov databases to review the rationale of designing curative HIV-1 vaccine immunogens based on the conserved favorable site of the virus. Most of these studies evaluate the efficacy of vaccine candidates in combination with other therapeutics and/or with new formulations and immunization protocols. This review briefly describes the design of conserved multiepitope constructs and outlines the results of these vaccine candidates in the recent clinical pipeline.

Increased frequency of HLA-A*02 in patients with atherosclerosis is associated with VZV seropositivity

BACKGROUND

HLA molecules are inherited key molecules in the immune inflammation and specific responses to environmental pathogens. We investigated the association of HLA-A alleles with Varicella zoster virus (VZV) seropositivity in patients with atherosclerosis (AS).

MATERIALS AND METHODS

Plasma Anti-VZV IgG and molecular HLA type were detected in 203 (100 AS⁺ and 103 AS^-) individuals.

RESULTS

Of 100 AS⁺ individuals, 66 were anti-VZV⁺ and 34 were anti-VZV^-. Of 103 age/sex-matched AS^- individuals, 59 were anti-VZV⁺ and 44 were anti-VZV^-. Anti-VZV-IgG in AS⁺ cases was higher than AS^- controls (p = .034). The mean anti-VZV IgG in HLA-A*02⁺AS⁺ individuals was higher than HLA-A*02⁺AS^- controls (p < .001). HLA-A*02 was associated with VZV-seropositivity (p = .01) in AS⁺ patients. A higher frequency of HLA-A*02-allele in AS⁺ patients compared to AS^- controls (p = .015) and an accumulation of HLA-A*02-allele in AS⁺ anti-VZV⁺ group (33.3%, p = .004) was observed.

CONCLUSIONS

HLA-A alleles and immune responses to VZV are associated with clinical atherosclerosis.

Artificial Anti-HIV-1 Immunogen Comprising Epitopes of Broadly Neutralizing Antibodies 2F5, 10E8, and a Peptide Mimic of VRC01 Discontinuous Epitope

The construction of artificial proteins using conservative B-cell and T-cell epitopes is believed to be a promising approach for a vaccine design against diverse viral infections. This article describes the development of an artificial HIV-1 immunogen using a polyepitope immunogen design strategy. We developed a recombinant protein, referred to as nTBI, that contains epitopes recognized by broadly neutralizing HIV-1 antibodies (bNAbs) combined with Th-epitopes. This is a modified version of a previously designed artificial protein, TBI (T- and B-cell epitopes containing Immunogen), carrying four T- and five B-cell epitopes from HIV-1 Env and Gag proteins. To engineer the nTBI molecule, three B-cell epitopes of the TBI protein were replaced with the epitopes recognized by broadly neutralizing HIV-1 antibodies 10E8, 2F5, and a linear peptide mimic of VRC01 epitope. We showed that immunization of rabbits with the nTBI protein elicited antibodies that recognize HIV-1 proteins and were able to neutralize Env-pseudotyped SF162.LS HIV-1 strain (tier 1). Competition assay revealed that immunization of rabbits with nTBI induced mainly 10E8-like antibodies. Our findings support the use of nTBI protein as an immunogen with predefined favorable antigenic properties.

Mass spectrometry-based identification of MHC-bound peptides for immunopeptidomics

Peptide antigens bound to molecules encoded by the major histocompatibility complex (MHC) and presented on the cell surface form the targets of T lymphocytes. This critical arm of the adaptive immune system facilitates the eradication of pathogen-infected and cancerous cells, as well as the production of antibodies. Methods to identify these peptide antigens are critical to the development of new vaccines, for which the goal is the generation of effective adaptive immune responses and long-lasting immune memory. Here, we describe a robust protocol for the identification of MHC-bound peptides from cell lines and tissues, using nano-ultra-performance liquid chromatography coupled to high-resolution mass spectrometry (nUPLC-MS/MS) and recent improvements in methods for isolation and characterization of these peptides. The protocol starts with the immunoaffinity capture of naturally processed MHC-peptide complexes. The peptides dissociate from the class I human leukocyte antigens (HLAs) upon acid denaturation. This peptide cargo is then extracted and separated into fractions by HPLC, and the peptides in these fractions are identified using nUPLC-MS/MS. With this protocol, several thousand peptides can be identified from a wide variety of cell types, including cancerous and infected cells and those from tissues, with a turnaround time of 2-3 d.

Formulation of chitosan with the polyepitope HIV-1 protein candidate vaccine efficiently boosts cellular immune responses in mice

Human immunodeficiency virus-1 (HIV-1) continues to be a major global public health issue and priority. Despite the variety of antiretroviral therapies, it seems that an effective vaccine against HIV-1 is still very necessary. An ideal HIV-1 vaccine should be able to elicit both humoral and cellular immunities. In this respect, polyepitope vaccines, incorporated from several conserved regions of HIV-1 proteins, have received much attention recently. Herein, the immunogenicity of the HIV-1 polyepitope protein-based candidate vaccines was evaluated in BALB/c mice. Following the plasmid (pET23a-HIV-1-tat/pol/gag/env) preparation and transformation, the recombinant protein expression was optimized in Escherichia coli BL21 (DE3) host cells. After the HIV-1-top4 protein purification, chitosan and alum adjuvants were added to the vaccines formulations to reinforce the immunogenicity of the candidate vaccines. Mice were subcutaneously immunized three times at 2-week intervals with the candidate vaccines and the elicitation of both humoral and cellular immune responses were investigated. Taken together, the results showed that chitosan adjuvanted candidate vaccine conferred a stronger immunogenicity and elicited higher cellular responses than other candidate vaccines (P < 0.05). Thereby, it seems that co-utilizing of potent adjuvants with the HIV-1 polyepitope protein vaccines can help to open new avenues for strategies for HIV/AIDS vaccine design.

Quantum dot/pMHC multimers vs. phycoerythrin/pMHC tetramers for identification of HLA-A*0201-restricted pHBV core antigen18-27-specific T cells

Detection of human leukocyte antigens-A2-restricted p-hepatitis B virus (HBV) core antigen‑specific cytotoxic T lymphocytes (CTLs) is important in the study of HBV immunopathogenesis and vaccine design. Currently, major histocompatibility complex (MHC) class I/peptide‑(p) MHCI tetramers are considered the optimal tools to detect antigen‑specific CTLs. However, the MHC‑tetramer technique also has certain drawbacks and is under continuous development. The quantum dot (QD) bioconjugates nanotechnology with its unique inorganic‑biological properties has been developing fast. However, QD/pMHC multimers have seldom been used for the identification of the C18‑27 epitope, which is important in HBV infection. QD/pMHC multimers were synthesized by metal‑affinity coordination and an avidin‑biotin system. In the present study they were characterized by transmission electron microscopy, dynamic light scattering and fluorescence spectrophotometry. C18‑27‑specific CTLs were obtained by ex vivo expansion of CD8+ T cells. Cultured CTLs were tested for the secretion level of interferon (IFN)‑γ by ELISA and for cytotoxicity by lactate dehydrogenase release assay. Then, the performance of phycoerythrin (PE)/pMHC tetramers and QD/pMHC multimers were compared by flow cytometry. The synthesized QD/pMHC multimers dispersed well and their emission spectrum exhibited only slight differences compared with original QDs. C18‑27‑specific CTLs not only secreted IFN‑γ but also effectively targeted T2 cells pulsed with peptide C18‑27. The frequencies of C18‑27‑specific CTLs determined by QD/pMHC multimers were higher compared with PE/pMHC tetramers. The present results suggested that QD/pMHC multimers may be able to characterize greater numbers of C18‑27‑specific CTLs with increased sensitivity compared to conventional strategies.

Immunotherapeutic Approaches for the Control and Eradication of HIV

Since the onset of the AIDS epidemic over 35 years ago, attempts at immunologic manipulation to develop preventative and therapeutic approaches to HIV infection have been the subject of intense focus by the scientific community. New tactics such as latency reveal agents and immune interventions with engineered and directed monoclonal antibodies, as well as vaccines for prevention and treatment are among the strategies addressed in this review.