Effects of single and multiple bouts of eccentric exercise on immune responses to HSV-gD1 DNA vaccination in mice

DNA vaccines comprise one modality of novel vaccination techniques. DNA vaccines employ intramuscular injection of DNA that codes for specific antigens from a pathogen. Prolonged eccentric endurance exercise can stimulate immune responses, possibly by increasing inflammatory mediators. This study aimed to determine the effects of one or three sessions of downhill running on the effectiveness of Herpes simplex virus type I glycoprotein D (HSV-gD1) DNA vaccination. Mice without or with one and three sessions of downhill running were vaccinated intramuscularly with the DNA vaccine or the empty vector. Cellular immune responses were assessed using an in vitro assay of lymphocyte proliferation in response to recall antigens. Also, a virus neutralisation test was used to determine the levels of neutralising antibodies in serum samples. In addition, Th1 and Th2 immune responses, and the ratio of the Th1/Th2 is considered an indicator of immune responses to infection in the current study. Multiple bouts of downhill running increased humoral immune responses after immunisation, also although Th2 immune responses decreased, lymphocyte proliferation and Th1/Th2 ratio immune responses increased following the viral challenge compared to the other groups. In addition, the timing of the 3-session exercise regimen plus DNA vaccination immediately following the last exercise session, as opposed to DNA vaccination 48 h before a single session of exercise, may account for the greater efficacy of DNA vaccination in the multiple bouts of the intensive exercise group. These findings indicate that short-term repeated bouts of eccentric endurance exercise have increased immune responses to intramuscular DNA-based vaccines.