Enhanced PD-1 expression by T cells in cerebrospinal fluid does not reflect functional exhaustion during chronic human immunodeficiency virus type 1 infection

S Sadagopal, SL Lorey, L Barnett, D Sutherland… - Journal of …, 2010 - Am Soc Microbiol
S Sadagopal, SL Lorey, L Barnett, D Sutherland, R Basham, H Erdem, SA Kalams, DW Haas
Journal of virology, 2010Am Soc Microbiol
During chronic viral infections, T cells are exhausted due to constant antigen exposure and
are associated with enhanced programmed death 1 (PD-1) expression. Deficiencies in the
PD-1/programmed death-ligand 1 (PD-L1) pathway are associated with autoimmune
diseases, including those of the central nervous system (CNS). To understand the role of PD-
1 expression in regulating T-cell immunity in the CNS during chronic infection, we
characterized PD-1 expression in cerebrospinal fluid (CSF) and blood of individuals with …
Abstract
During chronic viral infections, T cells are exhausted due to constant antigen exposure and are associated with enhanced programmed death 1 (PD-1) expression. Deficiencies in the PD-1/programmed death-ligand 1 (PD-L1) pathway are associated with autoimmune diseases, including those of the central nervous system (CNS). To understand the role of PD-1 expression in regulating T-cell immunity in the CNS during chronic infection, we characterized PD-1 expression in cerebrospinal fluid (CSF) and blood of individuals with chronic human immunodeficiency virus type 1 (HIV-1) infection. PD-1 expression was higher on HIV-specific CD8+ T cells than on total CD8+ T cells in both CSF and blood. PD-1 expression on CSF T cells correlated positively with CSF HIV-1 RNA and inversely with blood CD4+ T-cell counts, suggesting that HIV-1 infection drives higher PD-1 expression on CSF T cells. However, in every HIV-positive individual, PD-1 expression was higher on T cells in CSF than on those in blood, despite HIV-1 RNA levels being lower. Among healthy HIV-negative controls, PD-1 expression was higher in CSF than in blood. Furthermore, frequencies of the senescence marker CD57 were lower on CSF T cells than on blood T cells, consistent with our prior observation of enhanced ex vivo functional capacity of CSF T cells. The higher PD-1 expression level on CSF T cells therefore does not reflect cellular exhaustion but may be a mechanism to downregulate immune-mediated tissue damage in the CNS. As inhibition of the PD-1/PD-L1 pathway is pursued as a therapeutic option for viral infections, potential effects of such a blockade on development of autoimmune responses in the CNS should be considered.
American Society for Microbiology