No abstract

Taken together, our data indicate that virus-specific CD27- T cells may be important effector T cells in controlling chronic viral infections in humans and that lack of differentiation into CD27- effector T cells may lead to progression of viral disease.

We previously observed a loss of EpsteinBarr virus (EBV)-specific CD8 ؉ T cells in subjects progressing to EBV-related nonHodgkin lymphoma (NHL), correlating with loss of CD4 ؉ T cells. The aim of the present study was to determine the role of EBV-specific CD4 ؉ T cells in the development of NHL during chronic HIV infection. To this end, CD4 ؉ and CD8 ؉ memory T cells, capable of both proliferation and subsequent interferon ␥ (IFN␥) production, directed against a latent (EpsteinBarr virus nuclear antigen 1 [EBNA1]) and a lytic (BamH fragment Z left frame 1 [BZLF1]) EBV antigen were studied longitudinally in 9 progressors to NHL, 4 progressors to non-EBV-related AIDS, and 4 slow progressors to AIDS. In all 3 groups we observed a decline of EBV-specific memory CD4 ؉ and CD8 ؉ T-cell responses during HIV infection. However, whereas latent antigen EBNA1-specific CD4 ؉ T cells were lost well before diagnosis in all subjects who developed an AIDS-related NHL (and EBNA1-specific CD8 ؉ T cells were significantly lower compared with the other groups), these cells were better preserved in progressors to non-EBVrelated disease and slow progressors. Loss of EBNA1-specific T-cell immunity IntroductionThe Epstein-Barr virus (EBV) is a widespread human ␥-herpesvirus that persists for life in resting memory B cells after primary infection in the oropharynx. 1,2 Both primary infection as well as subsequent reactivations of the virus and proliferation of EBV-infected B cells are controlled mainly by CD8 ϩ T cells. 3,4 In immunosuppressed individuals a combination of factors may lead to lymphoproliferative disorders. 5,6 In HIV-infected subjects the risk of non-Hodgkin lymphoma (NHL) is 60-to 100-fold increased compared with the general population. [7][8][9] Most of these lymphomas are large B-cell lymphomas of which 50% to 70% are EBV positive. 10,11 While in HIV-infected individuals EBV-specific CD8 ϩ T cells are generally well preserved, 12,13 their ability to secrete interferon ␥ (IFN␥) in short-term antigen-specific stimulation assays is decreased, and in individuals progressing toward AIDS-related non-Hodgkin lymphoma the CD8 ϩ T-cell function ultimately collapses completely. 14 An association of this loss of CD8 ϩ T-cell function with a decrease in total CD4 ϩ T-cell numbers 14 suggests that a lack of EBV-specific CD4 ϩ T-cell help could play a role in disease progression. This would be in accordance with many human [15][16][17][18][19] and animal studies [20][21][22][23][24][25][26] that demonstrate the importance of CD4 ϩ T cells in the development and maintenance of effective CD8 ϩ T-cell responses.While the importance of EBV-specific CD8 ϩ T cells has been clearly demonstrated, and both the height and patterns of immunodominance of these CD8 ϩ T-cell responses are clearly defined, to date few data on EBV-specific CD4 ϩ T-cell responses are available. Due to the extremely low frequencies of these cells, only few investigators have been able to determine the ex vivo magnitude of the EBV-specific CD4 ϩ T-cell response. 27...

ObjectivesTo investigate whether T-cell activation and exhaustion is linked to HCV- and HIV disease parameters in HIV/HCV infected individuals, we studied T-cell characteristics in HIV/HCV coinfected patients and controls.Methods14 HIV/HCV coinfected, 19 HCV monoinfected, 10 HIV monoinfected patients and 15 healthy controls were included in this cross-sectional study. Differences in expression of activation and exhaustion markers (HLA-DR, CD38, PD-1, Tim-3 and Fas) and phenotypic markers on CD4+ and CD8+ T-cells were analysed by flow cytometry and were related to HCV disease parameters (HCV-viremia, ALT and liver fibrosis).ResultsFrequencies of activated CD4+ and CD8+ T-cells were higher in HIV/HCV-coinfected compared to healthy controls and HCV or HIV mono-infected individuals. Coinfected patients also showed high expression of the exhaustion marker PD-1 and death receptor Fas. In contrast, the exhaustion marker Tim-3 was only elevated in HIV-monoinfected patients. T-cell activation and exhaustion were correlated with HCV-RNA, suggesting that viral antigen influences T-cell activation and exhaustion. Interestingly, increased percentages of effector CD8+ T-cells were found in patients with severe (F3–F4) liver fibrosis compared to those with no to minimal fibrosis (F0–F2).ConclusionsHIV/HCV coinfected patients display a high level of T-cell activation and exhaustion in the peripheral blood. Our data suggest that T-cell activation and exhaustion are influenced by the level of HCV viremia. Furthermore, high percentages of cytotoxic/effector CD8+ T-cells are associated with liver fibrosis in both HCV monoinfected and HIV/HCV coinfected patients.

The leukocyte-associated Ig-like receptor-1 (LAIR-1) is capable of inhibiting immune cell function through interaction with collagens. LAIR is expressed on the majority of peripheral blood mononuclear cells. The abundant expression of both receptor and ligand calls for regulatory mechanisms to relieve the continuous interaction between collagens and LAIR-1. This regulation may occur at the expression level of the receptor. Here, we report that LAIR-1 is indeed differentially expressed during human T cell differentiation. Naive CD4 + and CD8 + T cells as well as CD8 + T cells of the effector phenotype express higher levels of LAIR-1 compared to memory T cells. In vitro stimulation revealed a decrease in LAIR-1 expression upon activation, and the lower LAIR-1 expression on CD127 -T cells suggests that activation-induced down-modulation of LAIR-1 may also occur in vivo. Furthermore, crosslinking of LAIR-1 on primary T cells results in an inhibition of T cell function. Our data suggest that regulated expression of LAIR-1 and the subsequent change in the threshold for activation may be a mechanism to modulate inhibition of the immune system.

In contrast to the situation in the post-transplant setting, in HIV-infected individuals an elevated EBV load is not predictive of EBV-related malignancies. To study whether a high EBV load is already a normal situation early in HIV infection and is not related to a decrease in immune function over time, we investigated EBV load and EBV-specific CD8+ T cells ∼1 year before and 1 year after HIV seroconversion. EBV load significantly increased after HIV seroconversion from 205 to 1002 copies/106 PBMC (p < 0.001), whereas no further increase in EBV load was observed between 1 and 5 years after HIV seroconversion (median, 1827–2478 copies/106 PBMC; p = 0.530). Interestingly, the absolute number of EBV lytic epitope, RAKFKQLL-specific CD8+ T cells increased over HIV seroconversion (4.78 to 9.54/μl; p = 0.011). Furthermore, the fraction of CD27-negative effector, RAK-specific CD8+ T cells tended to increase (from 12.2 to 17.31% CD27−; p = 0.051), in accordance with Ag-driven differentiation. In conclusion, both virological and immunological data support the idea that a new EBV viral setpoint is reached early in HIV infection, probably by EBV reactivation, as suggested by the preferential increase in EBV lytic epitope-specific CD8+ T cells. These data may thus help to explain the lack of predictive value of EBV load for the occurrence of AIDS-related lymphoma.

A lower function of EBV-specific CD8 + T cells in HIV-infected subjects could be related to a lack of specific CD4 + T cell help. Therefore, we studied EBV-specific CD4 + T cells in both healthy donors and untreated or highly active antiretroviral therapy (HAART)-treated HIV-seropositive homosexual men. To this end, PBMC were stimulated with overlapping peptide pools from a latent and a lytic EBV protein, EBV nuclear antigen (EBNA)1 and EBV lytic-switch protein ZEBRA (BZLF1), respectively. EBV-specific CD4 + T cell frequencies measured directly ex vivo were low. To measure EBV-specific memory CD4 + T cells, capable of both expansion and IFN-c production upon antigenic challenge, we developed a specific and reproducible assay, combining ex vivo expansion of specific T cells with flow cytometric analysis of IFN-c production. Untreated HIVinfected individuals had a lower CD4 + T cell response to both EBNA1 and BZLF1 as compared to healthy EBV carriers and HAART-treated HIV-positive subjects. This suggests loss of EBV-specific CD4 + T cells due to HIV infection, while HAART might restore this response. In addition, we found an increase in the EBNA1-specific CD8 + T cell response in HAART-treated subjects. Interestingly, numbers of EBV-specific CD4 + and CD8 + T cells were inversely correlated with EBV viral load, suggesting an important role also for EBV-specific CD4 + T cells in the control of EBV infection.

The immune system potentially plays an important mechanistic role in the relation between shift work and adverse health effects. To better understand the immunological effects of shift work, we compared numbers and functionality of immune cells between night-shift and non-shift workers. Blood samples were collected from 254 night-shift and 57 non-shift workers employed in hospitals. Absolute numbers of monocytes, granulocytes, lymphocytes, and T cell subsets were assessed. As read out of immune function, monocyte cytokine production and proliferative capacity of CD4 and CD8 T cells in response to various stimuli were analysed. The mean number of monocytes was 1.15 (95%-CI = 1.05–1.26) times higher in night-shift than in non-shift workers. Furthermore, night-shift workers who worked night shifts in the past three days had a higher mean number of lymphocytes (B = 1.12 (95%-CI = 1.01–1.26)), T cells (B = 1.16 (95%-CI = 1.03–1.31)), and CD8 T cells (B = 1.23 (95%-CI = 1.05–1.45)) compared to non-shift workers. No differences in functional parameters of monocytes and lymphocytes were observed. The differences in numbers of monocytes and T cells suggest that chronic exposure to night-shift work as well as recent night-shift work may influence the immune status of healthcare workers. This knowledge could be relevant for preventive initiatives in night-shift workers, such as timing of vaccination.