The antibiotic thiazole compound siomycin, which we have found from the culture broth of Actinomycetes (strain No.806097) in search of antibody production inhibitor, showed the in vitro immunosuppressive property against B-cells stimulated with T-cell independent antigen DNP-LPS (dinitrophenyl-lipopolysaccharide) while it also showed inhibitory effect against Tcell proliferation. Its inhibitory mechanism was considered to be different from that of FK506, the representative of T-cell immunosuppressant. Moreover, siomycin showed inhibitory effect in both T-cell dependent and independent murine antibody production models and decreased the severity in murine collagen arthritis model. Therefore, siomycin is a unique immunosuppressant which has potential for the treatment of some antibody-mediated diseases.
Novel antifungal lipopeptides, FR227673 and FR190293, were isolated from the fermentation broths of fungal strains Chalara sp. No. 22210 and Tolypocladium parasiticum No. 16616, respectively. These compounds have the same cyclic peptide nuclear structure as FR901379, with different side chains, and showed antifungal activity against Aspergillus fumigatus and Candida albicans attributed to inhibition of 1,3-b-glucan synthesis.
Novel immunosuppressive agents, FR252921, FR252922 and FR256523 were isolated from the cultured broth of a bacterial strain No. 408813. The strain was identified Pseudomonas fluorescens from morphological and physiological characteristics. FR252921, FR252922 and FR256523, novel compounds containing macrolactone ring, showed immunosuppressive activity against murine splenocyte proliferation stimulated with lipopolysaccharide (LPS) or anti-CD3 mAb in vitro.
The current COVID-19 pandemic requires urgent development of effective therapeutics. 5-amino levulinic acid (5-ALA) is a naturally synthesized amino acid and has been used for multiple purposes including as an anticancer therapy and as a dietary supplement due to its high bioavailability. In this study, we demonstrated that 5-ALA treatment potently inhibited infection of SARS-CoV-2, a causative agent of COVID-19. The antiviral effects could be detected in both human and non-human cells, without significant cytotoxicity. Therefore, 5-ALA is a candidate as an oral antiviral drug for COVID-19.
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