Pathological proliferation: a potential mechanism for poor CD4 + T cell recovery in people living with HIV

People living with HIV (PLWH) fail to achieve normalization of CD4 T cell counts and function, especially in immunological non-responders (INRs). The frequencies of Ki67 CD4 T cells were inversely associated with CD4 T cell counts in HIV infected patients. Early ART did not normalize CD4 T cell proliferation. However, the features of the abnormal proliferation CD4 T cell in INRs are far from known. PLWH were divided into INRs (n= 16) and immunological responders (IRs, n= 53) groups. Mass cytometry was applied to peripheral blood T cells to profile the immune cells and liquid chip technique was used to measure plasma levels of cytokines and chemokines. Correlation analyses were conducted to evaluate associations between the degree of CD4 T cell proliferation and immune function. The percentage of Ki67 CD4 T cells were significant higher in INRs, and we defined these cells with significant higher level of Ki67, as over-proliferating cells. No significant difference of markers' expression (HLA-DR, CD38, CD57, PD-1, PD-L1, CD107a, perforin) was found between INRs and IRs. Compared with naïve CD4 T cells in INRs, Ki67 CD4 T cells exhibited lower levels of CD57 and CD38. Whereas Ki67 T cells exhibited higher levels of CD38 and CD57 and activation compared with differentiated mature central memory CD4 T cells and effector memory CD4 T cells. Ki67 cells did not show higher levels of senescence and activation compared to certain Ki67 CD4 central memory T cells in IRs. Furthermore, Ki67 CD4 Tcm cells exhibited positive correlations with pro-inflammatory cytokines. We proposed and validated the hypothesis of "pathological proliferation" in INRs: excessive proliferation of CD4 T cells in INRs may be accompanied by aberrant activation, senescence and loss of immune function. Eventually, such over-proliferating but poor-quality cells in INRs result in incomplete recovery of both CD4 T cell counts and function. An intervention that enhancing the proliferative capacity or functional ability or both of CD4 T cell in INRs might therefore be beneficial.