PREVIOUS HEAT-SHOCK TREATMENT INHIBITS MAYARO VIRUS-REPLICATION IN HUMAN LUNG ADENOCARCINOMA (A549) CELLS

Human lung adenocarcinoma cells (A549) were submitted to mild or sever e heat shock (42 degrees C or 44 degrees C) for 1 h, while another gro up of cells was double-heat-shocked (submitted to 42 degrees C for 1 h , returned to 37 degrees C for 3 h, then exposed to 44 degrees C for 1 h). After each heat treatment, the cells were infected with Mayaro vi rus for 24 h and incubated at 37 degrees C. The results showed that th e double-heat-shocked thermotolerant cells exhibited a 10(4)-fold viru s titre inhibition, despite the recovery of protein synthesis and orig inal morphology 24 h post-infection. In contrast, cells submitted to m ild or severe heat shock exhibited weaker inhibition of Mayaro virus t itre (10(2)-fold). The mildly heat-shocked cells also presented a full recovery in protein synthesis, which was not observed in severely hea t-shocked cells. These results indicate that exposure of A549 cells to a mild or to a double heat shock treatment before Mayaro virus infect ion induces an antiviral state.