Prophylactic Effect of Microwave Radiation on Toxoplasma gondii Tachyzoites of RH Strain: A Method for Partial Immunization in BALB/c Mice.

Toxoplasma gondii is a ubiquitous protozoan parasite causing toxoplasmosis in humans. The goal of this study was to examine the effect of microwave on the viability and infectivity of T. gondii tachyzoites of the RH strain, both in vitro and in vivo. T. gondii tachyzoites of the RH strain were treated with microwave radiation for 5, 10, 15, and 20 s. The viability of treated tachyzoites was assessed using flow cytometry. The in vitro infectivity of these treated tachyzoites was investigated using the HeLa cell culture. For in vivo studies, BALB/c mice received two injections of treated tachyzoites mixed with Freund's adjuvant, over a fortnight interval, and their daily survival rates were monitored. Subsequently, untreated tachyzoites were inoculated into surviving mice in order to evaluate induced immunity. The produced IgG antibody titers in surviving mice were measured using the modified agglutination test. The flow cytometry method showed mortality rates of 46.89%, 74.11%, 88.38%, and 99.34% for the treated tachyzoites at 5, 10, 15, and 20 s, respectively. An in vitro analysis showed no proliferation of treated tachyzoites at 10- to 20-s time points after 24, 48, and 72 h. An in vivo study showed that all mice injected with tachyzoites treated for 5 s died, while those treated for 10-20 s survived. Mice that survived were exposed to untreated tachyzoites and showed a significant viability rate up to 18 days. The modified agglutination test showed an antibody titer of 1:80 in partially immunized mice. These results suggest that microwave-treated tachyzoites combined with Freund's adjuvant greatly enhance survival rates, reduce infectivity, and induce a humoral immune response in mice, offering partial protection against acute toxoplasmosis.