Inhibition of Human Immunodeficiency Virus Type 1 Infection of Human CD4 ⁺ T Cells by Microbial HSP70 and the Peptide Epitope 407-426

Abstract

Targeting the cognate human immunodeficiency virus type 1 (HIV-1) antigen is the classical way of preventing HIV-1 infection, but this approach has encountered serious problems in eliciting effective cytotoxic T lymphocytes (CTL) and neutralizing antibodies. Both CTL and neutralizing antibodies are subject to viral escape, and HIV-1 mutation may occur in the acute (30), as well as the chronic, phase of infection (4,12,15). Indeed, HIV-1 sequences found in a population may represent largely CTL escape variants restricted by the most prevalent HLA alleles in that population (29). Alternative preventive strategies such as the use of host antigens may have to be considered. Among a large, nonrandom selection of host proteins, HSP70 was found in the virion membrane of HIV-1; the amount was similar to that of Pol protein, and HSP70 functions as a chaperone during intracellular transport (17). HSP70 mRNA is upregulated in CD4 ϩ T cells infected with HIV-1 (35), and the expression of HSP70 is significantly increased in lymphocytes from HIV-1-infected subjects (1). HSP70 elicits innate immune responses by generating chemokines and cytokines (23, 27, 38), which exert robust adjuvanticity in nonhuman primates (5). Furthermore, alloimmune responses can be enhanced by stimulating the CD40-CD40L costimulatory pathway (13) and the alternative CD40-HSP70 pathway may function in a similar way by upregulating CD40, CD80/86, HLA-II, and tumor necrosis factor alpha (TNF-␣) (38, 39). Recently, we and others have demonstrated that HSP70 binds directly to CCR5 expressed on the surfaces of human CD4 ϩ T cells and dendritic cells (11,41).The aims of the present investigations were to explore and characterize any inhibitory effect of microbial HSP70 on HIV-1. An examination of the effect of HSP70 on HIV infectivity revealed a dose-dependent inhibition of HIV-1 infection of activated CD4 ϩ T cells. The inhibitory function of HSP70 was progressively localized, first to the C-terminal fragment (the peptide comprising amino acids [aa] 359 to 609 [p359-609]), then to the peptide binding domain (p359-494), and finally to the 20-mer peptide epitope (aa 407 to 426). The kinetics of the HIV-1-inhibitory effects of the HSP70 peptides over 24 h were comparable for HSP70, p359-609, and p359-494, though the duration of inhibition varied among the HSP70 fragments. We then explored any complementary inhibitory effect on HIV-1 by adding anti-CCR5 monoclonal or polyclonal antibodies to HSP70. Whereas HSP70 alone inhibited the R5 strains of HIV-1 in a dose-dependent way by up to a mean (Ϯ the standard error of the mean [SEM]) of 72.8% (Ϯ14.8%) and monoclonal antibody (mAb) to CCR5 inhibited HIV-1 up to 93.5% (Ϯ3.9%), combining HSP70 with mAb to CCR5 enhanced the level of inhibition to 99.7% (Ϯ0.9%). MATERIALS AND METHODSPreparation of HSP70, its C-terminal (aa 359 to 609) and N-terminal (aa 1 to 358) fragments, and the peptide binding domain (aa 359 to 494). The recombinant Mycobacterium tuberculosis HSP70, p359-609, p1-358, and p359-494 were prepared fr...

Caught with their PAMPs down? The extracellular signalling actions of molecular chaperones are not due to microbial contaminants

“…2c; Wang et al 2005a, b). Furthermore, the dose-dependent inhibition of HIV-1 infection of human CD4 + T cell lines by Hsp70 has been reproduced by p407-426 (Babaahmady et al 2007). The mechanism involves the stimulation of CCL-3, CCL-4 and CCL-5 chemokines, which bind and down-modulate CCR5, thereby preventing HIV-1 binding to the CCR5 co-receptors.…”

“…A comparative experiment in which GFP-labelled pseudovirions are treated with Hsp70, and LPS showed that the LPS-treated cells were 5-to 6-fold higher than Hsp70-treated counterparts. Hsp70 also increased A3G expression in CD8 + and CD4 + T cells and DCs to a greater extent than LPS, and LPS had no detectable effect on A3G expression at concentrations of 2.5 to 20 ng/ml (Babaahmady et al 2007). The Janus-like properties of HSPC4 (gp96) (A.G.P.…”

“…The dual Hsp70 receptor functions of CD40 and CCR5 have been utilised in the generation of the anti-viral factor APOBEC3G (A3G) by stimulating human CD4 + T cells with Hsp70, which up-regulates A3G and inhibits HIV-1 infectivity (Babaahmady et al 2007). A comparative experiment in which GFP-labelled pseudovirions are treated with Hsp70, and LPS showed that the LPS-treated cells were 5-to 6-fold higher than Hsp70-treated counterparts.…”

Effect of Vaginal Immunization with HIVgp140 and HSP70 on HIV-1 Replication and Innate and T Cell Adaptive Immunity in Women

“…HSP70 also functions as a coadjuvant by virtue of binding among other receptors, CD40 and the CCR5 molecules, and Toll-like receptor 4 (TLR4) in dendritic cells (DCs) and macrophages (14,(17)(18)(19). Furthermore, microbial HSP70 inhibits in vitro HIV-1 infection of human CD4 ϩ T cells (20). Thus, HSP70 may function as a coadjuvant, enhancing innate immunity, and when linked to antigen it may induce adaptive immune responses.…”

Unfolding the relationship between secreted molecular chaperones and macrophage activation states

“…It is therefore important to note that M. tuberculosis Hsp70 can dosedependently inhibit the infection of CD4 T cells by HIV-1, the active site in this protein being the C-terminal epitope 407-426. The Hsp70 apparently works by blocking the CCR5 co-receptor and by inhibition of CC-chemokines (Babaahmady et al 2007). This suggests a therapeutic potential for this protein and a re-examination of the M. tuberculosis/HIV-1 relationship.…”