Severity of viral infection is promoted by hyperthermic pretreatment

The aim of this study was to determine if prior heat shock and consequential heat shock protein (HSP) accumulation would inhibit viral infection. Confluent cultures of Madin-Darby bovine kidney cells were subjected to 30 mins of hyperthermia at 42 degrees C then allowed to recover at 37 micro C for six hrs. During the six hrs, HSP concentrations increased by 232% in heat-shocked cultures. Following the recovery period, six replicates of heat-shocked (HS) and six replicates of non-heat-shocked (CON) cultures were infected with Bovine Herpes virus 1. After 72 hours, severity of infection was assessed by counting formed viral plaques in cell cultures. CON cultures averaged 172.0+/-34.3 plaques per culture and HS cultures averaged 339.3+/-96.1 plaques per culture, representing a significant increase in infected cells (p=0.0044). These data provide evidence that physiological stressors related to extreme or exhaustive exercise, specifically hyperthermia, may increase risk of viral infection.