Untersuchung der Suppressionskapazität der polymorphonuclear myeloid derived suppressor cells (PMN-MDSCs) in der chronischen HIV-1-Infektion

Die HIV-1-Infektion ist durch die Ausbildung einer progredienten Immunschwäche gekennzeichnet. Zahlreiche Zellen des Immunsystems, darunter CD4+ T-Zellen, zytotoxische CD8+ T-Zellen und B-Zellen verlieren im Verlauf der Erkrankung essentielle Effektorfunktionen. Insbesondere der persistenten Immunaktivierung wird eine wesentliche Rolle in diesem Prozess zugeschrieben, welcher als Immunerschöpfung bezeichnet wird. Myeloid-derived suppressor cells (MDSCs) beschreiben eine heterogene Population unreifer myeloischer Zellen, die sich hauptsächlich in zwei Subgruppen untergliedert: monozytäre MDSCs (M-MDSCs) und polymorphonukleäre MDSCs (PMN-MDSCs). MDSCs expandieren in einer Vielzahl von Erkrankungen und zeichnen sich durch ihre Fähigkeit, T-Zellantworten zu hemmen, aus. Das Ziel der vorliegenden Arbeit bestand darin, die immunsuppressive Funktion der PMN-MDSCs in der chronischen HIV-1-Infektion zu untersuchen und zu eruieren, ob sie dem Phänomen der Immunerschöpfung unterliegt. Zu diesem Zweck wurden PMN-MDSCs des peripheren Bluts mit CD8+ T-Zellen in Proliferationsassays koinkubiert. Die Blutproben wurden Patienten in der chronischen HIV-1-Infektion, HIV-Controllern, Bronchialkarzinompatienten und gesunden Probanden entnommen. Nach der Koinkubation wurde die Suppressionskapazität, welche ein Maß für die Hemmung der T-Zellproliferation durch die PMN-MDSCs darstellt, zwischen den Studiengruppen verglichen. Zusätzlich wurde die PMN-MDSC-Frequenz und das Ausmaß der Immunaktivierung der CD8+ T-Zellen bestimmt. Die suppressive Aktivität der PMN-MDSCs bestätigte sich in allen untersuchten Studiengruppen. Dabei konnte erstmals nachgewiesen werden, dass PMN-MDSCs in der unbehandelten, chronischen HIV-1-Infektion ihre Suppressionskapazität verlieren. Es zeigte sich, dass die Hemmung der T-Zellproliferation bei PMN-MDSC-Frequenzen > 2,5 % niedriger ausfiel als bei Frequenzen < 2,5 %. Darüber hinaus wurden Korrelationen zwischen der PMN-MDSC-Frequenz, Viruslast und CD4-Zellzahl festgestellt. Zwischen quantitativen und qualitativen Eigenschaften der PMN-MDSCs und den Immunaktivierungsmarkern CD38 und HLA-DR bestand hingegen kein signifikanter Zusammenhang. Unsere Ergebnisse deuten darauf hin, dass PMN-MDSCs in der fortgeschrittenen HIV-1-Infektion ihre immunsuppressive Funktion verlieren und somit von der Immunerschöpfung betroffen sind

High frequencies of PMN-MDSCs are associated with low suppressive capacity in advanced stages of HIV-1 infection

Background Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) are an immature cell type that inhibits the effector functions of T lymphocytes in chronic HIV infection. A well-known immunological feature of the disease course is the development of immune exhaustion, which is correlated with excessive immune activation in late-stage disease. Here, we hypothesized that immune exhaustion would also affect PMN-MDSCs in late-stage HIV-1 infection. Methods We evaluated untreated chronically HIV-infected patients (progressors, n = 10) and control groups (controllers, patients with non-small cell lung carcinoma and healthy controls, n = 16) with regard to levels of PMN-MDSCs and their inhibitory potential. Additionally, we studied CD8 T cell effector functions (interferon-gamma, TNF alpha, IL-2 and CD107) and parameters of CD8 T cell activation (CD38 and HLA-DR) and exhaustion (PD-1 and LAG-3) by flow cytometry. Plasma inflammation markers analyzed here were IL-6, IL-8, soluble CD14, highly sensitive CRP, and cystatin C. Results Coincubation experiments with isolated PMN-MDSCs led to a significant inhibition of CD8 T cell proliferation (p < 0.0001), with a significant correlation between PMN-MDSC frequency and suppressive capacity: the higher the frequency of PMN-MDSCs was, the lower the suppressive capacity (rho = 0.51, p = 0.0082). Stratifying all study subjects into subgroups with PMN-MDSC frequencies above or below 2.5% resulted in a significantly increased suppressive capacity in patients with frequencies below 2.5% (p = 0.021). While there was no correlation with the cellular activation markers CD38 and HLA-DR, high IL-8 levels were significantly associated with high PMN-MDSC frequencies (rho = 0.52, p = 0.0074) and low suppressive capacity (rho = 0.47, p = 0.019). Conclusions In this study, we demonstrate for the first time that PMN-MDSCs show limited effector functions in advanced disease stages of HIV infection. The hyperactive immune state is associated with this loss of function. However, we show an association with the proinflammatory cytokine IL-8, which is an important factor for the migration and adhesion of polymorphonuclear cells

Treatment intensification in HIV-infected Patients is associated With reduced Frequencies of regulatory T cells

In untreated HIV infection, the efficacy of T cell responses decreases over the disease course, resulting in disease progression. The reasons for this development are not completely understood. However, immunosuppressive cells are supposedly crucially involved. Treatment strategies to avoid the induction of these cells preserve immune functions and are therefore the object of intense research efforts. In this study, we assessed the effect of treatment intensification [= 5-drug antiretroviral therapy (ART)] on the development of suppressive cell subsets. The New Era (NE) study recruited patients with primary HIV infection (PHI) or chronically HIV-infected patients with conventional ART (CHI) and applied an intensified 5-drug regimen containing maraviroc and raltegravir for several years. We compared the frequencies of the immune suppressive cells, namely, the myeloid-derived suppressor cells (MDSCs), regulatory B cells (Bregs), and regulatory T cells (Tregs), of the treatment intensification patients to the control groups, especially to the patients with conventional 3-drug ART, and analyzed the Gag/Nef-specific CD8 T cell responses. There were no differences between PHI and CHI in the NE population (p > 0.11) for any of the studied cell types. Polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC), monocytic myeloid-derived suppressor cell (M-MDSC), and the Breg frequencies were comparable to those of patients with a 3-drug ART. However, the Treg levels were significantly lower in the NE patients than those in 3ART-treated individuals and other control groups (p = 0.0033). The Gag/Nef-specific CD8 T cell response was broader (p = 0.0134) with a higher magnitude (p = 0.026) in the NE population than that in the patients with conventional ART. However, we did not find a correlation between the frequency of the immune suppressive cells and the interferon-gamma+ CD8 T cell response. In the treatment intensification subjects, the frequencies of the immune suppressive cells were comparable or lower than those of the conventional ART-treated subjects, with surprisingly broad HIV-specific CD8 T cell responses, suggesting a preservation of immune function with the applied treatment regimen. Interestingly, these effects were seen in both treatment intensification subpopulations and were not attributed to the start of treatment in primary infection

Treatment Intensification in HIV-Infected Patients Is Associated With Reduced Frequencies of Regulatory T Cells

In untreated HIV infection, the efficacy of T cell responses decreases over the disease course, resulting in disease progression. The reasons for this development are not completely understood. However, immunosuppressive cells are supposedly crucially involved. Treatment strategies to avoid the induction of these cells preserve immune functions and are therefore the object of intense research efforts. In this study, we assessed the effect of treatment intensification [=5-drug antiretroviral therapy (ART)] on the development of suppressive cell subsets. The New Era (NE) study recruited patients with primary HIV infection (PHI) or chronically HIV-infected patients with conventional ART (CHI) and applied an intensified 5-drug regimen containing maraviroc and raltegravir for several years. We compared the frequencies of the immune suppressive cells, namely, the myeloid-derived suppressor cells (MDSCs), regulatory B cells (Bregs), and regulatory T cells (Tregs), of the treatment intensification patients to the control groups, especially to the patients with conventional 3-drug ART, and analyzed the Gag/Nef-specific CD8 T cell responses. There were no differences between PHI and CHI in the NE population (p &gt; 0.11) for any of the studied cell types. Polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC), monocytic myeloid-derived suppressor cell (M-MDSC), and the Breg frequencies were comparable to those of patients with a 3-drug ART. However, the Treg levels were significantly lower in the NE patients than those in 3ART-treated individuals and other control groups (p ≤ 0.0033). The Gag/Nef-specific CD8 T cell response was broader (p = 0.0134) with a higher magnitude (p = 0.026) in the NE population than that in the patients with conventional ART. However, we did not find a correlation between the frequency of the immune suppressive cells and the interferon-gamma+ CD8 T cell response. In the treatment intensification subjects, the frequencies of the immune suppressive cells were comparable or lower than those of the conventional ART-treated subjects, with surprisingly broad HIV-specific CD8 T cell responses, suggesting a preservation of immune function with the applied treatment regimen. Interestingly, these effects were seen in both treatment intensification subpopulations and were not attributed to the start of treatment in primary infection