Summary Bacterial CRISPR systems provide acquired immunity against invading nucleic acids by activating RNA-programmable RNases and DNases. Cas13a and Cas12a enzymes bound to CRISPR RNA (crRNA) recognize specific nucleic acid targets, initiating cleavage of the targets as well as non-target ( trans ) nucleic acids. Here, we examine the kinetics of single-turnover target and multi-turnover trans -nuclease activities of both enzymes. High-turnover, non-specific Cas13a trans -RNase activity is coupled to rapid binding of target RNA. By contrast, low-turnover Cas12a trans -nuclease activity is coupled to relatively slow cleavage of target DNA, selective for DNA over RNA, indifferent to base identity, and preferential for single-stranded substrates. Combining multiple crRNA increases detection sensitivity of targets, an approach we use to quantify pathogen DNA in samples from patients suspected of Buruli ulcer disease. Results reveal that these enzymes are kinetically adapted to play distinct roles in bacterial adaptive immunity and show how kinetic analysis can be applied to CRISPR-based diagnostics.

Graphical Abstract Highlights d Loss of human OASL and mouse Oasl2 inhibits DNA virus infection d OASL and Oasl2 inhibit cGAS-mediated IFN induction d OASL specifically binds to cGAS to inhibit cGAS enzyme activity d OASL binds to cGAS independently of double-stranded DNA SUMMARY Interferon-inducible human oligoadenylate synthetase-like (OASL) and its mouse ortholog, Oasl2, enhance RNA-sensor RIG-I-mediated type I interferon (IFN) induction and inhibit RNA virus replication. Here, we show that OASL and Oasl2 have the opposite effect in the context of DNA virus infection. In Oasl2 À/À mice and OASL-deficient human cells, DNA viruses such as vaccinia, herpes simplex, and adenovirus induced increased IFN production, which resulted in reduced virus replication and pathology. Correspondingly, ectopic expression of OASL in human cells inhibited IFN induction through the cGAS-STING DNA-sensing pathway. cGAS was necessary for the reduced DNA virus replication observed in OASL-deficient cells. OASL directly and specifically bound to cGAS independently of double-stranded DNA, resulting in a non-competitive inhibition of the second messenger cyclic GMP-AMP production. Our findings define distinct mechanisms by which OASL differentially regulates host IFN responses during RNA and DNA virus infection and identify OASL as a negative-feedback regulator of cGAS.

Argyreia speciosa (Linn. f.) Sweet is a popular Indian medicinal plant, which has long been used in traditional Ayurvedic Indian medicine for various diseases. This plant is pharmacologically studied for nootropic, aphrodisiac, immunomodulatory, hepatoprotective, antioxidant, antiinflammatory, antihyperglycemic, antidiarrheal, antimicrobial, antiviral, nematicidal, antiulcer, anticonvulsant, analgesic and central nervous depressant activities. A wide range of phytochemical constituents have been isolated from this plant. A comprehensive account of the morphology, phytochemical constituents and pharmacological activities reported are included in view of the many recent findings of importance on this plant.

In vitro trials investigating the effects of albendazole and triclabendazole anthelmintics on the growth profiles of the egg-parasitic fungi Paecilomyces lilacinus and Verticillium chlamydosporium were undertaken. In addition, in vivo trials were conducted in goats fed on millet grain cultures of each fungus and administered albendazole and triclabendazole anthelmintics. In vitro growth revealed V. chlamydosporium to be more sensitive to albendazole compared to P. lilacinus. In contrast, triclabendazole had the least inhibitory effect on in vitro growth of both P. lilacinus and V. chlamydosporium. Similar to albendazole, growth of P. lilacinus was more vigorous at 0.5 ppm concentration of triclabendazole. Efforts to re-isolate these egg-parasitic fungi from faeces of goats fed on fungal millet grain cultures before and following single intraruminal administration of albendazole and triclabendazole showed that P. lilacinus was not able to be re-isolated from the faeces at any sampling period. In contrast, V. chlamydosporium was able to be re-isolated from the faeces at all of the sampling periods except for the samples taken at 8-18 h and 18-24 h after administration of albendazole and triclabendazole, respectively. Lack of fungal activity at these times coincided with peak plasma availability of anthelmintics and suggests faecal levels of drugs were also high at these times and impacted negatively on fungal viability.