Study of the role of the P2X7 receptor in conventional and follicular regulatory T lymphocytes in experimental malaria

• Grant number: 18/00686-3
• Support Opportunities: Scholarships in Brazil - Master
• Start date: May 01, 2018
• End date: March 31, 2020
• Field of knowledge: Biological Sciences - Immunology - Cellular Immunology
• Agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
• Principal Investigator: Maria Regina D'Império Lima
• Grantee: Paulo Henrique Lisboa Raeder
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Malaria is one of the most prevalent infectious diseases in the human species, accounting for more than 500,000 deaths a year worldwide. The immune response against plasmodium aids in the control of infection but can also contribute to its severity. Necrotic death causes the release of ATP, a signal of damage to cells of the immune system that activates inflammatory and tissue repair responses. ATP can also be released by activated and apoptotic cells through a channel called panexin-1, which results in autocrine and paracrine cell signaling. The P2X7 receptor is present in cells of the immune system and activates with high concentrations of extracellular ATP. Our recently published study showed the involvement of ATP and the P2X7 receptor in the protection against malaria caused by Plasmodium chabaudi AS (PcAS). This receptor contributes to the differentiation of TH1 lymphocytes in detriment of follicular CD4 + T lymphocytes (TFH), which cooperate with B lymphocytes for the production of antibodies. In addition, the absence of the P2X7 receptor leads to a reduction in the population of activated TREG lymphocytes (CD122 +). Based on the above considerations, the objective of this project is to establish the role of the P2X7 receptor in the generation and activity of conventional and follicular TREG lymphocytes in experimental malaria. To facilitate the analysis of the TREG lymphocytes we will use FoxP3-GFP P2X7 - / - mice, whose spleen cells will be compared with those of the FoxP3-GFP mice. The following parameters will be evaluated in the acute and chronic phases of infection by the parasites PcAS and Plasmodium yoelii 17XNL: (A) Expression of functional markers (CD25, CD39, CD44, CD62, CD69, CD73, CD122, PD-1, CXCR5, A2A , ICOS, GITR and CTLA-4) and transcription factors (T-bet and Bcl6), as well as the production of regulatory cytokines (IL-10 and TGF-b); (B) The suppressive activity towards the proliferation of CD4 + T lymphocytes stimulated with parasitized erythrocytes, as well as the production of IFN-³; (C) Expression of mRNAs related to differentiation of CD4 + T lymphocytes; (D) eATP response, assessing proliferation, cytokine production, and regulatory activity, as well as Ca2 + uptake and nuclear factor of activated T-cells (NFAT) translocation; (E) The same parameters described in the AD items obtained in infected CD4 - / - mice, which were previously transferred with CD4 + FoxP3-P2X7 + T lymphocytes, together with CD4 + FoxP3 + P2X7 + T lymphocytes or CD4 + T lymphocytes FoxP3 + P2X7- . This latter approach allows to verify the importance of P2X7 receptor expression in TREG cells for the regulation of the immune response, including TH1, TFH and B lymphocytes. This study will contribute to understand how the signs of damage affect the immune response against plasmodium. (AU)