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. 2018 Aug 29;92(18):e00370-18.
doi: 10.1128/JVI.00370-18. Print 2018 Sep 15.

Vaccination with the Conserved Caveolin-1 Binding Motif in Human Immunodeficiency Virus Type 1 Glycoprotein gp41 Delays the Onset of Viral Infection and Provides Partial Protection in Simian/Human Immunodeficiency Virus-Challenged Cynomolgus Macaques

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Vaccination with the Conserved Caveolin-1 Binding Motif in Human Immunodeficiency Virus Type 1 Glycoprotein gp41 Delays the Onset of Viral Infection and Provides Partial Protection in Simian/Human Immunodeficiency Virus-Challenged Cynomolgus Macaques

Ara G Hovanessian et al. J Virol. .

Abstract

We have previously reported that the CBD1 peptide (SLEQIWNNMTWMQWDK), corresponding to the consensus caveolin-1 binding domain in human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein gp41, elicits peptide-specific antibodies. Here, we have investigated the cellular immune response and the protective efficacy against a simian/human immunodeficiency virus (SHIV162P3) challenge. In addition to the CBD1 peptide, peptides overlapping the caveolin-binding-motif (CBM) (622IWNNMTWMQW631 or 622IWNNMTW628) were fused to a Gag-p24 T helper epitope for vaccination. All immunized cynomolgus macaques responded to a cocktail peptide immunization by inducing specific T cells and the production of high-titer CBD1/CBM peptide-specific antibodies. Six months after the fourth vaccine boost, six control and five vaccinated animals were challenged weekly by repeated exposure to SHIV162P3 via the mucosal rectal route. All control animals were infected after 1 to 3 challenges with SHIV, while among the five vaccinated monkeys, three became infected after a delay compared to control; one was infected after the eighth viral challenge, and one remained uninfected even after the ninth SHIV challenge. Immunized animals maintained a CD4 T cell count, and their central memory CD4 T cells were less depleted than in the control group. Furthermore, SHIV challenge stimulates antigen-specific memory T cell response in vaccinated macaques. Our results indicate that peptides derived from the CBM region can be immunogenic and provide protection against SHIV infection in cynomolgus monkeys.IMPORTANCE In HIV-1-producing cells, gp41 exists in a complexed form with caveolin-1, an interaction most probably mediated by the caveolin-1 binding motif. This sequence is highly conserved in every single HIV-1 isolate, thus suggesting that there is constant selective pressure to preserve this sequence for a specific function in the HIV infectious cycle. Consequently, the CBM sequence may represent the "Achilles' heel" of HIV-1 in the development of an efficient vaccine. Our results demonstrate that macaques immunized with the CBM-based peptides displayed a delay in the onset of viral infection and CD4 depletion, as well as a significant induction of antigen-specific memory T cell response, which is essential for the control of HIV/SIV infections. Finally, as HIV-infected individuals lack anti-CBM immune responses, CBM-based vaccines could have applications as a therapeutic vaccine in AIDS patients.

Keywords: AIDS; B cell; CD4; HIV; IgG; SIV; TH1; Th1; gp41; human immunodeficiency virus; immunization; macaque; memory T cells; simian immunodeficiency virus; vaccine.

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Figures

FIG 1
FIG 1
IgG responses in vaccinated cynomolgus macaques. ELISA was used to quantify specific IgG against the CBD1/CBM-based peptide-cocktail vaccine formulation. Sera were also tested against the HIV-Gag p24 peptide used as a carrier for CBM peptides. The titers correspond to the dilution of serum giving an OD value of ≥0.1. Arrowheads indicate the times of four immunizations at days 0, 42, 70, and 110.
FIG 2
FIG 2
T cell responses in individual vaccinated monkeys. PBMCs were stimulated with CBD1, K24W, K27W, and HIV-Gag p24 peptides. IL-2 (A), IFN-γ (B), and IL-4 (C) ELISpot assays were performed at different time points. Data are expressed as spot-forming cells (SFC) per million PBMCs minus the background (medium alone), which did not exceed 80 SFC per million cells. Arrowheads indicate immunizations.
FIG 3
FIG 3
Protective effect of CBD1/CBM vaccination. Six months after the fourth vaccine boost, animals were challenged with a repetitive low dose of SHIV162P3 (0.33 AID50; NIH) via the mucosal rectal route. (A) Acquisition rates in both control and CBD1/CBM-vaccinated monkeys. All animals from the control group were infected after 1 to 3 challenges with SHIV162P3. The difference between vaccinated and control groups was evaluated using Fisher's exact test (P = 0.03). (B) Survival curves of CBD1/CBM-vaccinated macaques versus controls. Statistical significance was evaluated using the Mantel-Cox test (P = 0.05). (C) Plasma viral loads of SHIV162P3-infected monkeys were evaluated by quantitative RT-PCR. (D) Peak viral load in control (closed symbols) and CBD1/CBM-vaccinated (open symbols) macaques. We arbitrarily considered the peak of viral load for the uninfected monkey at week 10. Statistical significance was evaluated using the Mann-Whitney test.
FIG 4
FIG 4
CBD1/CBM vaccination prevents memory CD4 T cell depletion. (A) CD4 T cell counts from control and CBD1/CBM-vaccinated monkeys at different weeks postchallenge. (B) CD4 T cell depletion at week 2 in control (closed circles) and CBD1/CBM-vaccinated (open circles) animals. (C) Peak of CD4 T depletion (in weeks postchallenge) in control (closed circles) and CBD1/CBM-vaccinated (open circles) animals. (D) Correlation between the peak of CD4 T cell depletion and the peak of viral load (VL). We arbitrarily considered the peak of viral load for the uninfected monkey at week 10. (E) Proportion of effector (EM) and central memory CD4 T cells depleted at week 2 from control (closed circles) and CBD1/CBM-vaccinated (open circles) monkeys. Statistical significance was evaluated using the Mann-Whitney test.
FIG 5
FIG 5
T cell responses in control and CBD1/CBM-vaccinated monkeys after SHIV challenge. PBMCs from controls (n = 6) and CBD1/CBM-vaccinated macaques (n = 5) were stimulated with CBD1, K24W, K27W, and HIV Gag peptides. IL-2 (A) and IFN-γ (B) ELISpots were used to quantify specific T cell responses at different weeks postchallenge. Data are expressed as spot-forming cells (SFC) per million PBMCs minus the background (medium alone).
FIG 6
FIG 6
Individual responses of CBD1/CBM-vaccinated monkeys. Numbers of IL-2 (A) and IFN-γ (B) spot-forming cells (SFC) per million PBMCs from CBD1/CBM-vaccinated monkeys after in vitro K27W or K24W peptide stimulations at different weeks postchallenge. Data are expressed as spot-forming cells (SFC) per million PBMCs minus the background (medium alone).
FIG 7
FIG 7
Magnitude of SIV Gag response in control and CBD1/CBM-vaccinated monkeys after SHIV challenge. PBMCs from CBD1/CBM-vaccinated macaques (30164, 30237, 30317, 30788, and 30809) and control macaques (27085R, 30154, 30713, 31003, 31004, 30991) were stimulated with SIV Gag antigen, and the numbers of IL-2 (A) and IFN-γ (B) ELISpots were assessed at different weeks postchallenge. Data are shown as spot-forming cells (SFC) per million PBMCs minus the background (medium alone).

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