Toxoplasma gondii serine protease inhibitor-1: a posible role in host cell invasion process

SANCHEZ V., BOGADO S., PICCHIO M., FENOY I., ARCÓN N., SOTO A., GOLDMAN A., MARTIN V

Congreso; XXVII Reunión Annual de la Sociedad Argentina de Protozoología. Buenos Aires; 2015

Toxoplasma gondii is able to invade any nucleated cell from a variety of warm-blooded animals in a highly controlled process that involves multiple steps: motility, adhesion and active entry into the host cell. During these events, the protein contents of the secretory organelles are released sequentially and in a highly regulated way. Among them, several proteases have been described, although the molecular mechanism of their regulation has not been described yet. TgPI-1 is a serine protease inhibitor secreted from dense granules and is expressed during all parasite stages. Although its role in the pathogenesis remains unknown, we have previously demonstrated that passive transfer of anti-rTgPI-1 serum to naive receptor mice was able to provide significant protection against parasite challenge. In this work we studied the possible implication of TgPI-1 in the host cell T. gondii invasion process. For this, RH tachyzoites were used to invade cultured Vero cells under different treatment conditions with anti-rTgPI-1 serum (PI) or with serum from naïve mice (Ctrl). Differential indirect immunofluorescence (IIF) was performed to distinguish attached tachyzoites to the host cell membrane from intracellular parasites. When tachyzoites were pre-incubated with sera and subsequently washed before infection of cells, the parasites treated with PI serum decreased their adhesion ability (20%) compare to control. When parasites and sera were added simultaneously to the cells, we observed a reduction in parasite entrance in the presence of PI serum (10%). Furthermore, when tachyzoites were pre-incubated with PI serum and put to invade cells without the subsequent washing, a significant reduction in the adhesion (37%) and the entry to the host cell (4.3%) was observed compare to Ctrl serum. These results show for the first time a possible role of T. gondii serine protease inhibitor-1 during the invasion process, at least in the steps of adhesion and entry into the host cell.