Effect of 3-bromopyruvate and atovaquone on infection during in vitro interaction of Toxoplasma gondii and LLC-MK2 cells.

Toxoplasma gondii infection can be severe during pregnancy and in immunocompromised patients. Current therapies for toxoplasmosis are restricted to tachyzoites and have little or no effect on bradyzoites, which are maintained in tissue cysts. Consequently, new therapeutic alternatives have been proposed as the use of atovaquone has demonstrated partial efficacy against tachyzoites and bradyzoites. This work studies the effect of 3-bromopyruvate (3-BrPA), a compound that is being tested against cancer cells, on the infection of LLC-MK2 cells with T. gondii tachyzoites, RH strain. No effect of 3-BrPA on host cell proliferation or viability was observed, but it inhibited the proliferation of T. gondii. The incubation of cultures with lectin Dolichos biflorus agglutinin (DBA) showed the development of cystogenesis, and an ultrastructural analysis of parasite intracellular development confirmed morphological characteristics commonly found in tissue cysts. Moreover, the presence of degraded parasites and the influence of 3-BrPA on endodyogeny were observed. Infected cultures were alternatively treated with a combination of this compound plus atovaquone. This resulted in a 73% reduction in intracellular parasites after 24 h of treatment and a 71% reduction after 48 h; cyst wall formation did not occur in these cultures. Therefore, we conclude that the use of 3-BrPA may serve as an important tool for the study of (i) in vitro cystogenesis; (ii) parasite metabolism, requiring a deeper understanding of the target of action of this compound on T. gondii; (iii) the alternative parasite metabolic pathways; and (iv) the molecular/cellular mechanisms that trigger parasite death.

Uric acid and HMGB1 are involved in the induction of autoantibodies elicited in mice infected with mouse hepatitis virus A59.

We have shown that mice infected with mouse hepatitis virus A59 develop autoantibodies (autoAb) to liver and kidney fumarylacetoacetate hydrolase (FAH). Because it has been proposed that the immune system is stimulated by alarm signals called damage-associated molecular patterns or alarmins, we investigated the participation of uric acid and high-mobility group box protein 1 (HMGB1) in the autoimmune response elicited by mouse hepatitis virus (MHV). Mice subjected to MHV infection had increased plasmatic uric acid concentration that significantly decreased after 20 days of daily treatment with allopurinol and, simultaneously, autoAb to FAH were undetected. Furthermore, this autoAb disappeared after 30 days of treatment with ethyl pyruvate, along with a substantial reduction in serum HMGB1 concentration. Both results indicated a remarkable relationship between the autoimmune process induced by the virus and uric acid and HMGB1 liberation. Unexpectedly, it was found that allopurinol and ethyl pyruvate inhibited the release of both uric acid and HMGB1. Because HMGB1 is activated through binding to interleukin 1ß, and that this cytokine is produced by the NLRP3 inflammasome that could be stimulated by uric acid, we propose that both alarmins could be acting in concert with the induction of the autoAb to FAH in MHV-infected mice.