Distinct Immune Profiles of Exhausted Effector and Memory CD8(+) T Cells in Individuals With Filarial Lymphedema

CD8(+) T cells are crucial for the clearance of viral infections, and current research begins to highlight their importance in parasitic diseases too. In-depth research about characteristics of CD8(+) T-cell subsets and exhaustion remains uncertain, especially during filariasis, a chronic helminth infection. Lymphatic filariasis, elicited by Wuchereria bancrofti, remains a serious health problem in endemic areas in Ghana, especially in those suffering from morbidity due to lymphedema (LE). In this observational study, the characteristics and profiles of CD8(+) T cells were compared between asymptomatic Wuchereria bancrofti-infected individuals, uninfected endemic normals, and those with LE (grades 2–6). Focusing on exhausted memory (CD8(+)ex(mem): CD8(+) T-bet(dim)Eomes(hi)) and effector (CD8(+)ex(eff): CD8(+)T-bet(hi)Eomes(dim)) CD8(+) T-cell subsets, advanced flow cytometry revealed that LE individuals presented reduced frequencies of IFN-γ(+)CD8(+)ex(mem) T cells expressing Tim-3 or LAG-3 which negatively correlated to the presence of LE. Moreover, the LE cohort further showed significantly higher frequencies of IL-10(+)CD8(+)ex(eff) T cells expressing either Tim-3, LAG-3, CD39, KLRG-1, or PD-1, all associated markers of exhaustion, and that these frequencies positively correlated with the presence of LE. In summary, this study shows that distinct exhausted CD8(+) T-cell subsets are prominent in individuals suffering from LE, suggesting that enhanced inflammation and constant immune activation might drive exhaustion of CD8(+) T cells. Since T-cell exhaustion is known to be associated with insufficient control of persisting antigen, the data presented here reveals that these CD8(+) T-cell exhaustion patterns in filarial LE should be taken into consideration for prevention and control management of LE.