Modulation of the CD161+ Double-Negative T cell Population During Progression of HIV-1 Infection to AIDS is Correlated with an Increased Pro-Inflammatory T cell Gene Expression

This study characterized CD3+ T cell populations able to secrete IL-17; CD4+, CD8+ and double negative (CD3+CD4-CD8− - DNTs). All CD3 + T cells capable of producing IL-17 are positive for the expression of the surface marker CD161. Using this information, we used flow cytometric methods to characterize these various CD3+ T cell populations in HIV-1 infected patients (n= 36), AIDS patients (n=11) and healthy controls (n=11). The CD4+CD161+ T cells remain relatively stable until reaching the AIDS stage of infection, where there is a dramatic depletion as a percentage of the total CD161+ T cell population (Healthy Controls: 59.67%±6.05 vs. AIDS Group: 40.33%±5.04; p=0.003). The CD8+CD161+ T cell population does not change significantly as a percentage of the total CD161+ population, but the most striking result of our research is that CD161 + DNTs are more than doubled as a percentage of the CD161+ population (Healthy Controls: 12.87%±2.41 vs. AIDS Group: 29.90%±5.17 (p=0.001)). This is significant in that CD161+ DNTs are a highly pro-inflammatory cell population. Secondly, our findings demonstrated that two populations of CD161+DNTs exist; those that are CD3bright and CD3moderate. We concluded that CD3moderateCD161+DNTs were most likely of the α:β-CD3 phenotype, while those CD36brightCD161 +DNTs were likely to be of γδ-CD3 phenotype. Lastly with respect to our flow cytometric data; we noticed a phenomenon we call 'CD8 Drift.' In both our healthy controls and HIV-1 infected populations, the CD4 +CD161+ population is tightly grouped and, with respect to CD4 expression, demonstrates equal brightness to that of the CD4 +CD161− T cells. However, in both our healthy control and patient population, the CD8+CD161+ and CD8+CD161− T cells do not stain equally as bright in regard to CD8 expression. The CD8+CD161 + T cells are scattered broadly across the quadrant, appearing to 'drift' from CD8+ expression to CD8− expression.;In the latter stages of HIV-1 infection, with the CD4+ T cells depleted from the virus, and the CD8+ T cells exhausted due to chronic immune activation, we formed the hypothesis that the increase in these CD161+DNTs represented the human immune systems final effort at producing a pro-inflammatory immune response. To test this we isolated CD3+ T cells from five healthy controls and eight HIV-1 infected patients, and isolated their RNA for use in microarray analysis with qRT-PCR. We predicted that the HIV-1 infected patients with low CD4 counts would have a distinctly pro-inflammatory T cell transcriptional profile as compared to healthy controls. The four HIV-1 infected patients with CD4 counts below 100 showed no positive or negative fold change greater than two, with any of the genes profiled. Of the four HIV patients profiled with CD4 counts between 320 and 101, two showed statistically significant, 2+ fold change (p= <0.001) with respect to the IL-8 gene, while a third patient was very close to significant expression with a p=0.073. The IL-8 cytokine is the major chemoattractant for recruiting polymorphonuclear cells (PMNs) to sites of acute inflammation, and IL-17 is known to act on multiple tissues to induce the secretion of IL-8. Also significantly up-regulated in on the four patients were the GATA-3, CCL20, MMP3, CCL1 and CCL2, though only CCL1 and CCL2 showed a greater than 2+ fold change. Also, in three of the four patients with CD4 counts above 100, there were four genes that had +2 fold changes, and though they never reached the level of significance, they should still be mentioned due to their recurrence in each of the patient's transcriptional profiles. IL-1β, IL-6, CXCL1 and CXCL2 are those genes. All genes that have been listed function to mediate pro-inflammatory immune responses, which support our initial hypothesis that there is a correlation between the increase in CD161+DNTs and the generation of a pro-inflammatory transcriptional profile within the latter stage of an HIV-1 infection. These CD161+DNTs may very well be the body's final attempt at inducing a pro-inflammatory response. (Abstract shortened by UMI.).