HIV-1 p17 Gag (77-85) – SLYNTVATL – Epitope of Human Immunodeficiency Virus 1
HIV-1 p17 Gag (77-85), also called SL9, is a short part of the Human Immunodeficiency Virus 1 especially a short peptide of matrix composed of the viral protein p17 ensuring the integrity of the virion particle. HIV-1 p17 Gag (77-85) HLA-A*02:01-restricted was one of the first cytotoxic T lymphocytes epitope identified for HIV-1. It produces a specific cytotoxic T cells response in 75% of chronically infected adults but a rare activity in acute infection. Therefore, HIV-1 p17 Gag (77-85) may serve as target for anticancer immunotherapeutic strategies especially for vaccine development.
Applications of HIV-1 p17 Gag (77-85)
HIV-1 p17 Gag (77-85) is used to stimulate CTL responses in peripheral blood mononuclear cells (PBMCs). Then, ELISPOT assay is used to quantify peptide epitope specificity and IFN-γ releasing effector cells.
Potential cross-reactivities with FluM1 (58-66) and HCV NS5B (2594-2602)
Moreover, HIV-1 p17 Gag (77-85) share similarities with FluM1 (58-66) which can potentially show a cross-reactivity between these epitopes. It has been demonstrated a cross-reactivity and results suggest that immunity following infection by Influenza virus causes specific immune response to HIV-1 p17 Gag (77-85).
Similarities between two others HLA-A2-restricted epitopes of two viruses have been demonstrated too: the amino acid sequence of HIV-1 p17 Gag (77-85) (SLYNTVATL) and of HCV NS5B (2594-2602) (ALYDVVTKL). Therefore, researches are conducted to know if during HCV/HIV co-infection it could be exist a T cell cross reactivity.
HIV’s considerable capacity to vary its HLA-I-restricted peptide antigens allows it to escape from host cytotoxic T lymphocytes (CTLs). Nevertheless, therapeutics able to target HLA-I-associated antigens, with specificity for the spectrum of preferred CTL escape mutants, could prove effective. Here we use phage display to isolate and enhance a T-cell antigen receptor (TCR) originating from a CTL line derived from an infected person and specific for the immunodominant HLA-A(*)02-restricted, HIVgag-specific peptide SLYNTVATL (SL9). High-affinity (K(D) < 400 pM) TCRs were produced that bound with a half-life in excess of 2.5 h, retained specificity, targeted HIV-infected cells and recognized all common escape variants of this epitope. CD8 T cells transduced with this supraphysiologic TCR produced a greater range of soluble factors and more interleukin-2 than those transduced with natural SL9-specific TCR, and they effectively controlled wild-type and mutant strains of HIV at effector-to-target ratios that could be achieved by T-cell therapy.
2- Champagne P. et al. Nature. 410(6824):106-111 (2001)
Understanding the lineage differentiation of memory T cells is a central question in immunology. We investigated this issue by analysing the expression of the chemokine receptor CCR7, which defines distinct subsets of naive and memory T lymphocytes with different homing and effector capacities and antiviral immune responses to HIV and cytomegalovirus. Ex vivo analysis of the expression of CD45RA and CCR7 antigens, together with in vitro analysis of the cell-division capacity of different memory CD8+ T-cell populations, identified four subsets of HIV- and CMV-specific CD8+ T lymphocytes, and indicated the following lineage differentiation pattern: CD45RA+ CCR7+ –> CD45RA- CCR7+ –> CD45RA- CCR7- –> CD45RA+ CCR7-. Here we demonstrate through analysis of cell division (predominantly restricted to the CCR7+ CD8+ T-cell subsets) that the differentiation of antigen-specific CD8+ T cells is a two-step process characterized initially by a phase of proliferation largely restricted to the CCR7+ CD8+ cell subsets, followed by a phase of functional maturation encompassing the CCR7- CD8+ cell subsets. The distribution of these populations in HIV- and CMV-specific CD8+ T cells showed that the HIV-specific cell pool was predominantly (70%) composed of pre-terminally differentiated CD45RA- CCR7- cells, whereas the CMV-specific cell pool consisted mainly (50%) of the terminally differentiated CD45RA+ CCR7- cells. These results demonstrate a skewed maturation of HIV-specific memory CD8+ T cells during HIV infection.
3- Collins K. L., Chen B. K., Kalams S. A., Walker B. D. and Baltimore D. Nature. 391(6665):397-401 (1998)
Cytotoxic T lymphocytes (CTLs) lyse virally infected cells that display viral peptide epitopes in association with major histocompatibility complex (MHC) class I molecules on the cell surface. However, despite a strong CTL response directed against viral epitopes, untreated people infected with the human immunodeficiency virus (HIV-1) develop AIDS. To resolve this enigma, we have examined the ability of CTLs to recognize and kill infected primary T lymphocytes. We found that CTLs inefficiently lysed primary cells infected with HIV-1 if the viral nef gene product was expressed. Resistance of infected cells to CTL killing correlated with nef-mediated downregulation of MHC class I and could be overcome by adding an excess of the relevant HIV-1 epitope as soluble peptide. Thus, Nef protected infected cells by reducing the epitope density on their surface. This effect of nef may allow evasion of CTL lysis by HIV-1-infected cells.
4- Kan-Mitchell J., Bisikirska B., Wong-Staal F., Schaubert K. L., Bajcz M. and Bereta M. J. Immunol. 172(9):5249-5261 (2004)
The CTL response to the HLA-A*0201-restricted, HIV-1 p17 Gag77–85 epitope (SLYNTVATL; SL9) has been extensively studied in patients. Although this reactivity is exceptionally prominent in chronically infected patients and inversely correlated to viral load, SL9-specific CTLs (SL9-CTLs) are rarely detected in acute infection. To explore the cellular basis for this unusual manifestation, SL9-CTLs primed ex vivo from naive circulating CD8+ T cells of healthy, seronegative donors were generated and characterized. SL9 appeared to differ from other well-studied A*0201-restricted epitopes in several significant respects. In contrast to published reports for influenza and melanoma peptides and the HIV gag IV9 epitope studied here in parallel, SL9-CTLs were primed by immature but not mature autologous dendritic cells. Highly activated SL9-CTLs produce sufficient autocrine mediators to sustain clonal expansion and CTL differentiation for months without CD4 T cells or exogenous IL-2. Moreover, SL9-CTLs were sensitive to paracrine IL-2-induced apoptosis. IL-2 independence and sensitivity to paracrine IL-2 were also characteristic of SL9-CTLs immunized by dendritic cells transduced by a nonreplicating lentiviral vector encoding full-length Gag. In vitro-primed SL9-CTLs resembled those derived from patients in degeneracy of recognition and functional avidities for both SL9 and its natural mutations. Together, these data show that SL9 is a highly immunogenic, help-independent HIV epitope. The scarcity of SL9-CTLs in acute infection may result from cytokine-induced apoptosis with the intense activation of the innate immunity. In contrast, SL9-CTLs that constitutively produce autocrine help would predominate during CD4-diminished chronic infection.
5- Acierno P. M., Newton D. A., Brown E. A., Maes L. A., Baatz J. E. and Gattoni-Celli S. J. Transl. Med. 1(3) (2003)
BACKGROUND: The matrix protein of the influenza A virus and the matrix and capsid proteins of the human immunodeficiency virus (HIV) share striking structural similarities which may have evolutionary and biological significance. These similarities led us to hypothesize the existence of cross-reactivity between HLA-A2-restricted FLU-M1:58–66 and HIV-1 p17 GAG:77–85 epitopes.
METHODS: The hypothesis that these two epitopes are cross-reactive was tested by determining the presence and extent of FLU/GAG immune cross-reactivity in lymphocytes from HIV-seropositive and seronegative HLA-A2+ donors by cytotoxicity assays and tetramer analyses. Moreover, the molecular basis for FLU/GAG cross-reactivity in HIV-seropositive and seronegative donors was studied by comparing lymphocyte-derived cDNA sequences corresponding to the TCR-β variable regions, in order to determine whether stimulation of lymphocytes with either peptide results in the expansion of identical T-cell clonotypes.
RESULTS: Here, we report evidence of cross-reactivity between FLU-M1:58–66 and HIV-1 p17 GAG:77–85 epitopes following in vitro stimulation of PBMC derived from either HIV-seropositive or seronegative HLA-A2+ donors as determined by cytotoxicity assays, tetramer analyses, and molecular clonotyping.
CONCLUSION: These results suggest that immunity to the matrix protein of the influenza virus may drive a specific immune response to an HLA-A2-restricted HIV gag epitope in HIV-infected and uninfected donors vaccinated against influenza.
The immunologic mechanisms underlying the faster progression of hepatitis C virus (HCV) disease in the presence of human immunodeficiency virus (HIV) coinfection are not clearly understood. T-cell cross-reactivity between HCV and influenza virus-specific epitopes has been associated with rapid progression of HCV disease (S. Urbani, B. Amadei, P. Fisicaro, M. Pilli, G. Missale, A. Bertoletti, and C. Ferrari, J. Exp. Med. 201:675-680, 2005). We asked whether T-cell cross-reactivity between HCV and HIV could exist during HCV/HIV coinfection and affect pathogenesis. Our search for amino acid sequence homology between the HCV and HIV proteomes revealed two similar HLA-A2-restricted epitopes, HIV-Gag (SLYNTVATL [HIV-SL9]) and HCV-NS5b (ALYDVVSKL [HCV-AL9]). We found that 4 out of 20 HLA-A2-positive (HLA-A2+) HIV-infected individuals had CD8+ T cells that recognized both the HIV-SL9 and HCV-AL9 epitopes. However, the AL9 epitope was generally shown to be a weak agonist. Although HCV-monoinfected individuals in our study did not show AL9-specific responses, we found that about half of HCV/HIV-coinfected individuals had dual responses to both epitopes. High dual T-cell recognition among coinfected subjects was usually due to separate T-cell populations targeting each epitope, as determined by pentamer staining. The one individual demonstrating cross-reactive T cells to both epitopes showed the most advanced degree of liver disease. In coinfected individuals, we observed a positive correlation between the magnitudes of T-cell responses to both the SL9 and the AL9 epitopes, which was also positively associated with the clinical parameter of liver damage. Thus, we find that HIV infection induces T cells that can cross-react to heterologous viruses or prime for T cells that are closely related in sequence. However, the induction of cross-reactive T cells may not be associated with control of disease caused by the heterologous virus. This demonstrates that degeneracy of HIV-specific T cells may play a role in the immunopathology of HCV/HIV coinfection.
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