A prospective study on correlation between the decrease in anti-P17 antibody level and progression to AIDS in asymptomatic carriers of HIV

The HIV matrix protein p17 subverts nuclear receptors expression and induces a STAT1-dependent proinflammatory phenotype in monocytes

Background

Long-term remission of HIV-1 disease can be readily achieved by combinations of highly effective antiretroviral therapy (HAART). However, a residual persistent immune activation caused by circulating non infectious particles or viral proteins is observed under HAART and might contribute to an higher risk of non-AIDS pathologies and death in HIV infected persons. A sustained immune activation supports lipid dysmetabolism and increased risk for development of accelerated atehrosclerosis and ischemic complication in virologically suppressed HIV-infected persons receiving HAART.

Aim

While several HIV proteins have been identified and characterized for their ability to maintain immune activation, the role of HIV-p17, a matrix protein involved in the viral replication, is still undefined.

Results

Here, we report that exposure of macrophages to recombinant human p17 induces the expression of proinflammatory and proatherogenic genes (MCP-1, ICAM-1, CD40, CD86 and CD36) while downregulating the expression of nuclear receptors (FXR and PPARγ) that counter-regulate the proinflammatory response and modulate lipid metabolism in these cells. Exposure of macrophage cell lines to p17 activates a signaling pathway mediated by Rack-1/Jak-1/STAT-1 and causes a promoter-dependent regulation of STAT-1 target genes. These effects are abrogated by sera obtained from HIV-infected persons vaccinated with a p17 peptide. Ligands for FXR and PPARγ counteract the effects of p17.

Conclusions

The results of this study show that HIV p17 highjacks a Rack-1/Jak-1/STAT-1 pathway in macrophages, and that the activation of this pathway leads to a simultaneous dysregulation of immune and metabolic functions. The binding of STAT-1 to specific responsive elements in the promoter of PPARγ and FXR and MCP-1 shifts macrophages toward a pro-atherogenetic phenotype characterized by high levels of expression of the scavenger receptor CD36. The present work identifies p17 as a novel target in HIV therapy and grounds the development of anti-p17 small molecules or vaccines.

HIV-1 Matrix Protein p17 Modulatesin VivoPreactivated Murine T-Cell Response and Enhances the Induction of Systemic and Mucosal Immunity Against Intranasally Co-administered Antigens

HIV-1 p17 is a viral cytokine that acts on preactivated, but not on resting, human T cells promoting proliferation, proinflammatory cytokines release and HIV-1 replication, after binding to a cellular receptor (p17R). Here, we demonstrate that p17Rs are expressed on activated murine T cells, which respond to p17 stimulation similarly to their human counterpart. We developed a mouse model of abortive HSV-1 infection to induce T cell activation in vivo. Preactivated cells expressed p17Rs and were highly susceptible to p17 stimulation, which triggered proinflammatory cytokines release and promoted CD4+ T cell survival and expansion. Coculture of in vivo activated splenocytes with macrophages in the presence of p17 further increased their ability to produce IFN-gamma. The presence of macrophages and activated T cells at mucosal sites prompted us to investigate the immunomodulatory activities of p17 in vivo. Intranasal coadministration of p17 with beta-galactosidase (beta-gal) resulted in improved beta-gal specific cellular and humoral immune responses at systemic and mucosal levels. It is well established that HIV-1 replication is driven in an autocrine/paracrine manner by endogenously produced proinflammatory cytokines. Our results highlight the role of p17 in sustaining cellular activation and inflammation, thereby promoting a permissive microenvironment for HIV-1 replication. In addition, p17 is a promising candidate antigen, exhibiting immunomodulatory/adjuvant properties, that need to be exploited in the development of HIV/AIDS vaccines.

Cross-reactivity of anti-HIV-1-p17-derivative peptide (P30-52) antibody to Env V3 peptide

Strong antibody responses are often seen in human immunodeficiency virus type 1 (HIV-1) carriers, but it is not known whether these antibodies are effective in the inhibition of disease progression. In this study, we examined antigenic epitopes for anti-HIV-1 p17 antibody (p17 Ab) in an HIV-1 carrier's serum, and found that the residues of amino acid numbers 1 to 12 (P1-12), 12 to 29 (P12-29) and 30 to 52 (P30-52) of p17 were highly recognized in the serum. Our examination of purified antibodies from the patient using the p17-derivative-peptide-immunoaffinity columns showed that the reactivity of anti-p30-52 Ab (p30-52Ab) was high for p30-52 and the naive protein, p17. In addition, this P30-52Ab cross-reacted with the third variable region of the envelope glycoprotein (Env V3). To confirm this cross-reactivity, we immunized mice with P30-52, and established a monoclonal antibody (MAb), 8H10. We found that 8H10 was also reactive to Env V3. It is unclear whether this cross-reactivity of P30-52 Ab can function as the inhibitor of HIV-1, but these results will be of help in clarifying the interaction of Env protein with HIV-1 gag polyprotein and the relationship of the decline of the p17 antibody titer with the disease progression in HIV-1 carriers.

Anti-P30-52 monoclonal antibody cross-reacted to Env V3 and inhibited the viral multiplication of HIV-1-infected MT-4 cells

It is well known that the anti-p17 antibody titer decreases with the disease progression among human immunodeficiency virus type 1 (HIV-1) carriers. We previously established several murine anti-p17 monoclonal antibodies (MAbs) to investigate the immunological role of p17, and to further characterize these MAbs, we examined the anti-p17 antibody titer in serum of a patient who was a long-term nonprogressor with hemophilia, and found that the antibody for the p17-derivative peptide from amino acid residues 30 to 52 (P30-52) cross-reacted to the third variable region of the envelope glycoprotein of HIV-1, Env V3. In the present study, we primed mice with P30-52 to establish anti-P30-52 MAbs (P30-52 MAbs), and examined their affinity and whether they suppressed the viral multiplication of HIV-1-infected MT-4 (HTLV-1-transformed CD4+ T-cell line) cells, in a TCID50 assay. At the same time, an anti-Env V3 MAb (Env V3 MAb) was also established and examined as above. The IgM-type P30-52 MAb and Env V3 MAb showed heteroclitic binding, and the IgM-type P30-52 MAb inhibited the viral multiplication. We also found that an increase of fragmented DNA of HIV-1-infected MT-4 cells co-cultured with P30-52 MAbs. Because DNA fragmentation is one of the features of programmed cell death, the viral multiplication may be suppressed by the apoptosis of HIV-1-infected MT-4 cells co-cultured with P30-52 MAbs. Though the relationship between cross-reactivity and the inhibition mechanism of multiplication of HIV-1 is unclear, P30-52 of p17 may well be a useful region of viral proteins for the development of therapeutic and vaccination strategies.

Random expression of human immunodeficiency virus-1 (HIV-1) p17 (epitopes) on the surface of the HIV-1-infected cell

Twenty monoclonal antibodies (MAbs) were obtained by immunizing Balb/c mice with recombinant p17 (rp17) of HIV-1. Epitope specificity of each MAb was determined using six peptides that cover the entire region of p17. We found that each MAb reacts with only one of the peptides, residues 12-29, 30-52, 53-87, and 87-115 (P12-29, P30-52, P53-87, P87-115) of p17 with the exception of one MAb. Three kinds of MAbs that recognize P30-52, P87-115, and a conformational epitope, suppressed the infectivity of HIV-1 (JMH-1) when they added in the culture of MT-4 cells infected by HIV-1 within 24 h of the infection.

Antibodies to the HIV-1 p17 protein cross-react with human superoxide dismutase-2

Antibodies reacting with the gag protein p17 of the human immunodeficiency virus type 1 (HIV-1) can occasionally be found in the serum of non-HIV-1-infected individuals. Conversely, anti-p17 antibodies can also react with human tissues from non-infected individuals. Here we report on the isolation from human liver of a molecule that is immunoreactive with anti-p17 antibodies. This molecule was purified to homogeneity and identified as superoxide dismutase-2 (manganese type SOD). Both human SOD-2 and HIV-1 p17 contain the LQPALK hexapeptide which may serve as a common antigenic determinant. This study indicates that human SOD-2 is a target for anti-p17 antibodies and suggests that HIV-1-negative individuals may possess SOD-2 auto-antibodies that cross-react with HIV-1 p17.