Trypanosoma cruzi: interaction with vertebrate cells in vitro. IV. Environmental temperature effects

The effects of 4 environmental temperatures (29, 32, 35, and 38 C) on the interaction between Trypanosoma cruzi and bovine embryo skeletal muscle cells were quantified. Three aspects of the interaction (penetration of host cells by trypomastigotes, the lag period prior to the reproductive phase, and the reproductive phase) were markedly affected by temperature. There was a linear increase in the number of trypomastigotes penetrating cells in the 29–35 C range. Temperatures above 35 C can be considered supraoptimal as no further increase in the rate of penetration occurred. The lag period decreased linearly as temperature increased in the 29–35 C range; at 38 C, the lag period was markedly shortened. The doubling time of amastigotes increased linearly as temperature increased in the 32–38 C range; at 29 C, the doubling time was markedly lengthened. At all temperatures, parasites reproduced for 9 generations before cell rupture. The changes in lag period and doubling time complemented each other in the 32–38 C range. Thus, there was essentially no change in the overall length of the intracellular cycle which lasted 6.1 to 6.5 days. At 29 C, however, the cycle was lengthened to 8.9 days. Thermodynamic analysis revealed marked differences, characterized by a negative activation energy and negative enthalpy, between the reproductive phase of parasites within vertebrate cells and the vertebrate cells themselves. However, the thermodynamic parameters of parasites reproducing extracellularly in liquid medium and intracellularly were the same.