MITOCHONDRIAL AND METABOLIC ALTERATIONS IN CD4 T CELL DURING THE ACUTE PHASE OF TRYPANOSOMA CRUZI INFECTION.

ANA, YAMILE; JORGE ROJAS M; LAURA FOZZATTI; CERBAN F; CINTHIA STEMPIN

Congreso; Reunion de la ALAI; 2018

Trypanosoma cruzi, the parasite that causes Chagas disease, was identified 100 years ago. However, this infection is still a serious social and public health problem being endemic in Central and South America. Traditionally, it has been limited to poor rural areas where vector transmission is the main route of infection. Migration from rural to urban areas, congenital transmission and transplants have allowed the disease to spread beyond its natural geographical boundaries, becoming a global health issue. The disease involves an acute stage that evolves to a chronic stage that is usually asymptomatic, however one third of patients develop dilated cardiomyopathy that can progress to heart failure due to the effects of parasite persistence, immune dysregulation and microvascular damage. Several alterations of the immune response have been described during acute phase of the infection, including a dysfunction in the T cell compartment due to the generation of unresponsive anergic T cells and induction of CD4 T cell apoptosis causing deletion of effector cells favoring the persistence of the parasite. However, despite several decades of research, the mechanisms underlying the immunoregulation induced by the parasite are only partially understood and by operating simultaneously they make the response inefficient.We recently demonstrated that CD4 T cells from acute phase of T. cruzi experimental infection showed an increase in the E3-Ubiquitin-Ligase Gene Related to Anergy in Lymphocytes (GRAIL) expression coinciding with a decreased proliferation in these cells. In addition, CD4 T cell displayed as well increased PD-1 expression, reduced IL-2 production and lower mTOR activation. It has been shown that upon activation T cells undergo metabolic reprogramming to glycolysis and mitochondrial biogenesis required to support their functions. Since mTOR is a central regulator of metabolism, we investigate the status of metabolic pathways in CD4 T cells during T. cruzi infection. BALB/c mice were infected by intraperitoneal injection with 500 trypomastigotes of Tulahuen strain. CD4 T cells were purified from spleen of uninfected (control) or infected mice at different days post infection (d.p.i.). We evaluated expression of nutrient transporters CD98 (aminoacids) and Glut1 (glucose) as well as uptake of a fluorescent glucose analog 2NBDG by Flow cytometry. We did not observed differences in CD98 and Glut1 expression in ex vivo CD4 T cells from infected animals compared with controls. However, after anti-CD3/anti-CD28 stimulation, CD4 T cells from control and 42 d.p.i animals were able to upregulate these transporters besides increased the uptake of 2NBDG compared to unstimulated cells. However, CD4 T cells from 21 d.p.i. animals showed no differences compared to unstimulated cells. Additionally, to study mitochondrial function we combined a potential-dependent (MitoOrange) and a potencial-independent mitochondrial dye (MitoGreen) to identify CD4 T cells with depolarized mitochondria as well as measured mitochondrial ROS production (MitoSox) by Flow cytometry. At day 15 d.p.i. a higher fraction of CD4 T cells had depolarized mitochondria and produced increased levels of mROS compared with control or 42 d.p.i. animals, being mROS production greater in CD4 T cells with high PD-1 expression. These results may indicate T. cruzi induces mitochondrial alteration with high production of mitochondrial ROS leading to metabolic dysregulation of CD4 T cells. Then this mechanism could contribute to the immunosuppression observed during the acute phase of T. cruzi infection.