Characterization of memory T cells in individuals resistant to Schistosoma mansoni infection

Abstract

Schistosomiasis is the second most important parasitic infection in terms of socioeconomic and public health impact in tropical and subtropical areas. It affects about 240 million people worldwide, especially in rural and peri-urban areas, and it is estimated that about 700 million people live in areas at risk of infection worldwide. 1 In Brazil, it is estimated that about 1.5 million people live in areas at risk of contracting the disease. 2 Some studies have shown that natural resistance to S mansoni infection involves both Th1 and Th2 responses with low levels of IgG4 against parasite-specific antigens. 3,4 Indeed, resistance to reinfection after antiparasitic treatment has been associated with an increase in the IgE/IgG4 ratio, involvement of specific IgE to the detriment of production IgG4, 5,6 and production of the Th2 cytokines IL-4 and IL-5 against parasite antigens. 7 As reviewed by Bourke et al, 8 CD4 + T cells play key functions in host defence against helminth reinfection, including schistosomiasis. Despite the strategies of vaccine development being based on induction of effector responses by CD4 + T cells, the mechanisms involved in this process require further elucidation. 9-11 The differentiation of CD4 + memory T cells and CD8 + T cells during continuous Abstract Schistosomiasis affects about 240 million people worldwide and is estimated that about 700 million people live in areas at risk of infection. In the context of immune response associated with infection by Schistosoma mansoni, the role of memory T cells is not well understood. Aim: To evaluate the frequency of memory CD4 + and CD8 + T cells from individuals resistant and susceptible to Schistosoma mansoni infection. Methods and Results:We selected individuals with low (resistant) and high (susceptible) parasite burden using databases generated during previous studies carried out in the same endemic area. The cell surface markers were performed using flow cytometry. In this study, the resistant individuals showed an increase in the CD4 + memory T-cell pool associated with an increase in the central memory cell (TCM) and a decrease in the effector memory cell (T EM ). Individuals susceptible to infection had higher frequencies of effector memory cells compared to resistant individuals. Conclusions:These data suggest that resistance to S mansoni infection may be associated with an increase in the number of CD4 + memory T cells and susceptibility to infection is associated with a decrease in the central memory cell as well as high proportions of effector memory cells. K E Y W O R D S memory T cells, Schistosoma mansoni, schistosomiasis

The burden of HIV, syphilis and schistosome infection and associated factors among adults in the fishing communities in northwestern Tanzania

“…Further, it is difficult to assess schistosome infection as a risk factor in a setting where over 80% of people have schistosome infections. In areas of such high endemicity, those who are not schistosome‐infected may have some unique immunologic or epidemiologic factor that causes them to remain uninfected [28–30]. It is also possible that reporting bias led to underestimation of the effects of STI symptoms or risky sexual behaviour on HIV infection in this community.…”