Plasma TIGIT Level Is a Possible Marker in HIV-Related Liver Damage

T cell immunoglobulin and ITIM domain (TIGIT), has a key role in immunopathogenesis of HIV. Previous studies on immune checkpoint receptors had mainly focused on the membrane form. To evaluate clinical significance of soluble form of TIGIT (sTIGIT) in people living with HIV. Blood samples of 61 untreated HIV-infected patients and 24 healthy individuals were collected and TIGIT concentrations in plasma were measured by ELISA method. A decreased level of plasma TIGIT in HIV-infected patients was found to be negatively associated with AST/ALT ratio (r = -0.5358, p = 0.0483) that was indicative of liver damage. Moreover, the proportion of TIGIT on CD3⁺CD4⁺ cells in HIV-infected individuals increased (47.12 ± 5.051%) compared with in healthy controls (22.13 ± 4.426%, p < 0.01), which indicated change in plasma TIGIT level was at least partially attributed to CD3⁺CD4⁺ T cells. Furthermore, there was a strong positive correlation between TIGIT plasma levels and lymphocyte activation gene-3 (LAG-3) plasma levels in HIV-infected patients with a linear correlation coefficient r = 0.904. Therefore, plasma TIGIT level is a possible marker in HIV-related liver damage and LAG-3 closely related to TIGIT possibly plays a co-ordinated role in HIV-related liver damage.