T cell receptor usage in patients with non-progressing HIV infection

Predicting the impact of CD8+ T cell polyfunctionality on HIV disease progression

During the chronic phase of HIV-1 infection, polyfunctional CD8+ T cell responses, which are characterized by a high frequency of cells able to secrete multiple cytokines simultaneously, are associated with lower virus loads and slower disease progression. This relationship may arise for different reasons. Polyfunctional responses may simply be stronger. Alternatively, it could be that the increased functional diversity in polyfunctional responses leads to lower virus loads and slower disease progression. Lastly, polyfunctional responses could contain more CD8+ T cells that mediate a specific key function that is primarily responsible for viral control. Disentangling the influences of overall strength, functional diversity, and specific function on viral control and disease progression is very relevant for the rational design of vaccines and immunotherapy using cellular immune responses. We developed a mathematical model to study how polyfunctional CD8+ T cell responses mediating lytic and nonlytic effector functions affect the CD4+ T cell count and plasma viral load. We based our model on in vitro data on the efficacy of gamma interferon (IFN-γ) and macrophage inflammatory protein 1β (MIP-1β)/RANTES against HIV. We find that the strength of the response is a good predictor of disease progression, while functional diversity has only a minor influence. In addition, our model predicts for realistic levels of cytotoxicity that immune responses dominated by nonlytic effector functions most positively influence disease outcome.

IMPORTANCE

It is an open question in HIV research why polyfunctional CD8+ T cell responses are associated with better viral control, while individual functional correlates of protection have not been identified so far. Identifying the role of CD8+ T cells in HIV-1 infection has important implications for the potential development of effective T cell-based vaccines. Our analysis provides new ways to think about a causative role of CD8+ T cells by studying different hypotheses regarding why polyfunctional CD8+ T cells might be more advantageous. We identify measurements that have to be obtained in order to evaluate the role of CD8+ T cells in HIV-1 infection. In addition, our method shows how individual cell functionality data can be used in population-based virus dynamics models.

A nonsense mutation (428G-->A) in the fucosyltransferase FUT2 gene affects the progression of HIV-1 infection

BACKGROUND

The human FUT2 gene encodes the alpha(1,2)fucosyltransferase that determines secretor status. Homozygous for the nonsense mutation are called non-secretors and are unable to express histo-blood group antigens in secretions and on mucosal surfaces. In this study we have investigated the importance of the FUT2 fucosyltransferase activity on the progress of HIV-1 infection.

METHODS

Swedish blood donors (n = 276), 15 long-term non-progressors (LTNP) and 19 progressors were genotyped with respect to the nonsense mutation 428G-->A in the FUT2 gene. In addition 265/276 blood donors and 19 progressors with rapid or expected progression rate were Delta32 CCR5 genotyped.

RESULTS

Of 276 blood donors 218 (79%) were found to be secretor positive (se+), either homozygous (se+/+) wild type (30%) or heterozygous (se+/-) (49%) and 58 (21%) were homozygous non-secretors (se-/-). Five LTNP (33%) were found to be secretor-positive (se+/+, se+/-) and 10 (67%) se-/-. Of the 19 individuals with normal HIV-1 progression 15 (79 %) were found to be secretor positive and four (21%) were non-secretors. No frequency differences were found in the Delta32 CCR5 allele among the groups studied.

CONCLUSION

Strong association (P < 0.001) was observed between the nonsense mutation 428G-->A in the FUT2 gene and a slow disease progression of HIV-1 infection.

Flow cytometry evaluation of the T-cell receptor Vbeta repertoire among human T-cell lymphotropic virus type-1 (HTLV-1) infected individuals: effect of interferon alpha therapy in HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)

Human T-cell lymphotropic virus type-1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is chronic inflammatory disease of the spinal cord characterized by perivascular lymphocytic cuffing and parenchymal lymphocytic infiltration. In this study using flow cytometry, we have investigated the T-cell receptor (TCR) Vbeta repertoire of peripheral blood T lymphocytes in 8 HAM/TSP patients, 10 HTLV-1 infected healthy carriers, and 11 uninfected healthy controls to determine if there is a biased usage of TCR Vbeta. We found that TCR Vbeta7.2 was under-utilized and Vbeta12 was over-utilized in CD4+ T cells of HTLV-1 infected individuals compared with healthy uninfected controls, whereas there were no such differences in CD8+ T cells. Comparison of Vbeta repertoire changes before and after interferon-alpha (IFN-alpha) treatment for HAM/TSP revealed that one out of five patients showed dramatic decrease of specific Vbeta in CD8+ T cells. Our results suggest that dominant Vbeta subpopulations in CD4+ T cells evolved associated with chronic HTLV-1 infection, and IFN-alpha treatment for HAM/TSP does not induce a specific pattern of TCR Vbeta changes.

Flow Cytometry Evaluation of the T-Cell ReceptorVβ Repertoire Among HIV-1 Infected Individuals Before and After Antiretroviral Therapy

HIV-1 infection leads to serious impairment of the immune system and perturbations in the T cell receptor Vbeta repertoire are also described. Immune reconstitution can be potentially achieved in response to HAART. In the present study 10 patients were investigated for the Vbeta pattern expression before and after six months of HAART. TCR were analyzed for T CD4+ and CD8+ subsets, separately, by flow cytometry, using a monoclonal antibody set of 24 different Vbeta chains. Compared to eight Brazilian healthy controls, no differences in Vbeta pattern of expression was observed for patients before or on antiretroviral therapy. Some chains such as Vbeta 3, 14, 16, 20 and 21.3 were over utilized by both T subsets, independently of HIV infection and/or antiretroviral treatment, differing from the ones described for individuals of other nationalities. However, when each patient was taken individually, particular alterations were detected for the Vbeta gene usage, compared to controls, for all individuals. After treatment, significant Vbeta usage changes were observed for seven patients. One or more chains on both T subsets were engaged in this process, defining a preferential oligoclonal profile for TCR repertoire distribution, after HAART. Although no pattern of specific Vbeta changes was detected in the circulating T cells, we cannot exclude that differential immune responses to HIV or other important antigens are being focused by these cells.

The T-cell receptor in primates: identifying and sequencing new owl monkey TRBV gene sub-groups

The New World primate Aotus nancymaae (owl monkey) has been shown to be an excellent experimental model when studying malarial parasites. Characterising the T-cell receptor (TR) alphabeta repertoire by means of the different variable beta (TRBV) genes displayed contributes to a better understanding of these lymphocytes' role in the response against several malarial antigens. This study describes identifying and characterising eleven new TRBV gene sub-groups in cDNA from Aotus nancymaae's peripheral blood lymphocytes; these 11 gene sequences displayed homology to the previously reported human TRBV3, TRBV10, TRBV11, TRBV14, TRBV18, TRBV19, TRBV20, TRBV25, TRBV27, TRBV29 and TRBV30 sub-groups, resulting in 83% overall homology at the amino acid level. An additional Aotus sequence was found having similarity with the human TRBJ-2-7*01 gene. Evolutionary relationships amongst these sequences and the homologous genes from both New and Old World primates have shown that the TRBV repertoire has been maintained in the species being studied, displaying varying association patterns and substitution rates, depending on the sub-group being studied. The degree of identity observed when comparing human and Aotus genes suggests that these species might have a similar TRBV repertoire.

Resistance to viral infection by intraepithelial lymphocytes in HIV-1 P18-I10-specific T-cell receptor transgenic mice

For the analysis of mucosal immunity to HIV-1, we have recently established a line of transgenic (Tg) mice expressing the TCRalpha and TCRbeta genes of the murine CTL clone RT1 specific for P18-I10 (RGPGRAFVTI), an immunodominant gp160 envelope-derived epitope of IIIB isolate, restricted by the H-2D(d) MHC-I molecule. Here we examine those cells bearing specific TCR among the intraepithelial lymphocytes (IELs), with flow cytometric analysis using H-2D(d)/P18-I10 tetramers. We observed three distinct CD3(+), tetramer positive populations among the IELs: extra-thymic CD8alphabeta(+), alphabetaTCR T-cells; CD8 alphaalpha+, gammadeltaTCR T-cells; and thymus-derived CD8alphabeta+, alphabetaTCR T-cells. Challenge of these Tg mice with P18-I10 encoded by a vaccinia virus vector, either intrarectally (i.r.) or intraperitoneally (i.p.), revealed that the intraepithelial compartment seems to be a major site for prevention of the spread of viral infection. Such immunity appears due to the thymus-derived, CD8alphabeta+ antigen-specific CTLs together with CD8alphaalpha+ gammadelta cells, which regulate virus spread. This model system for studying CTL based immunity at mucosal sites should prove helpful in developing rational approaches for HIV control.

The heat-shock protein receptor CD91 is up-regulated in monocytes of HIV-1-infected "true" long-term nonprogressors

A small proportion of patients with human immunodeficiency virus type 1 (HIV-1) remains asymptomatic for a long period after infection. It is thought that a vigorous immune response may contribute to long-term nonprogression, though studies are confounded by heterogeneity among patients. We studied the levels of HIV-1 receptors, costimulatory T-cell molecules, and dendritic cell (DC) numbers in 18 patients with long-term infection, CD4 counts greater than 400 cells/mm(3), and HIV-1 viral loads lower than 50 copies/mL. These patients were further differentiated through the presence or absence of 2-LTR DNA circles, a possible marker for residual ongoing HIV-1 replication. A statistically significant increase in levels of CD91, the heat-shock protein (HSP) receptor, was observed in therapy-naive patients who had no evidence of ongoing viral replication (P =.01). This difference was most notable on their monocytes. High levels of CD91 may be a host factor that contributes to the maintenance of long-term nonprogression. The ability of CD91 to internalize alpha-defensins and to cross-present exogenous antigen to cytotoxic T lymphocytes through major histocompatibility complex (MHC) class 1 may maintain CD8(+) responses in these patients.