High-throughput synergy screening identifies microbial metabolites as combination agents for the treatment of fungal infections

The high mortality rate of immunocompromised patients with fungal infections and the limited availability of highly efficacious and safe agents demand the development of new antifungal therapeutics. To rapidly discover such agents, we developed a high-throughput synergy screening (HTSS) strategy for novel microbial natural products. Specifically, a microbial natural product library was screened for hits that synergize the effect of a low dosage of ketoconazole (KTC) that alone shows little detectable fungicidal activity. Through screening of approximate to 20,000 microbial extracts, 12 hits were identified with broadspectrum antifungal activity. Seven of them showed little cytotoxicity against human hepatoma cells. Fractionation of the active extracts revealed beauvericin (BEA) as the most potent component, because it dramatically synergized KTC activity against diverse fungal pathogens by a checkerboard assay. Significantly, in our immunocompromised mouse model, combinations of BEA (0.5 mg/kg) and KTC (0.5 mg/kg) prolonged survival of the host infected with Candida parapsilosis and reduced fungal colony counts in animal organs including kidneys, lungs, and brains. Such an effect was not achieved even with the high dose of 50 mg/kg KTC. These data support synergism between BEA and KTC and thereby a prospective strategy for antifungal therapy.

SEROLOGICAL SURVEY OF A CAPTIVE MACAQUE COLONY IN CHINA FOR ANTIBODIES TO SIMIAN TYPE-D RETROVIRUSES

Sera from 510 macaques consisting of Macaca mulatta, Macaca assamensis, Macaca fascicularis, Macaca nemestrina, and Macaca arctoides were investigated for antibodies to simian AIDS type D retrovirus (SRV) by ELISA and Western blot with viral antigens purified from supernatants of SRV-1 infected cell cultures. Of these monkeys, 104 were seropositive by ELISA; only 23 were confirmed by Western blot. The true positive reaction to SRV was found in 15 of 463 (3.2%) M. mulatta and eight of eleven (72.7%) M. assamensis.