Cyclophosphamide immunosuppressed Xid mice model clarify the protective role of B cells in experimental encephalitozoonosis
Authors: Moysés Carla Renata Serantoni , Vidôto da Costa Lidiana Flora , Perez Elizabeth Cristina , Xavier José Guilherme , Spadacci-Morena Diva Denelle , Rocha Paulo Ricardo Dell’Armelina , Alvares-Saraiva Anuska Marcelino , Lallo Maria Anete 
Published: September 2018

Encephalitozoon cuniculiis an intracellular pathogen that stablishes a balanced relationship with immunocompetent individuals, which is dependent of T lymphocytes activity. We previously showed X-linked immunodeficiency (XID – B cell deficient) mice are more susceptible to encephalitozoonosis and B-1 cells presence influences in the immune response. Because XID mice are deficient both in B-1 and B-2 cells, here we investigate the role of these cells againstE. cuniculiinfection using cyclophosphamide (Cy) immunosuppressed murine model to exacerbate the infection. XID mice presented lethargy and severe symptoms, associated with encephalitozoonosis and there was an increase in the peritoneal populations of CD8+and CD4+T lymphocytes and macrophages and also in the proinflammatory cytokines IFN-γ, TNF-α and IL-6. In BALB/c mice, no clinical signs were observed and there was an increase of T lymphocytes and macrophages in the spleen, showing an effective immune response. B-2 cells transfer to XID mice resulted in reduction of symptoms and lesion area with increase of B-2 and CD4+T populations in the spleen. B-1 cells transfer increased the peritoneal populations of B-2 cells and macrophages and also reduced the symptoms. Therefore, the immunodeficiency of B cells associated to Cy immunosuppression condition leads to disseminated and severe encephalitozoonosis in XID mice with absence of splenic immune response and ineffective local immune response, evidencing the B-1 and B-2 cells role against microsporidiosis.

Author summary

The adaptive immune response plays a key role againstEncephalitozoon cuniculi, an opportunistic fungus for T cells immunodeficient patients. The role of B cells and antibody play in natural resistance toEncephalitozoon cuniculiremains unresolved. Previously, we demonstrated that B-1 deficient mice (XID), an important component of innate immunity, were more susceptible to encephalitozoonosis, despite the increase in the number of CD4+and CD8+T lymphocytes. In order to better understand the role of B-1 and B-2 cells and the relationship with the other cells of the immune response in encephalitozoonosis, we infected withE. cuniculiin cyclophosphamide immunosuppressed mice. Here we demonstrate that infected XID mice showed reduction of T cells and macrophages and increase of proinflammatory cytokines associated with disseminated and severe encephalitozoonosis with presence of abdominal effusion and lesions in multiple organs. This pattern of infection observed in mice with genetic deficiency in T cells, so we suggest that the absence of B-1 cells affects the cytotoxic capacity of these lymphocytes. When we transfer B-2 cells to XID mice, the lesion areas caused by the fungus, the populations of T lymphocytes in the peritoneum and the proinflammatory cytokines decrease, indicating a better resolution of the infection. We speculate that B-1 and B-2 cells participate in the immune response againstE. cuniculi, interacting with the other components effective in immunity. The results shown here indicate that B-1 cells as a constituent of the innate response to microsporidia.