A Comparison of the Antibacterial Efficacy of Carbohydrate Lipid-like (Thio)Ether, Sulfone, and Ester Derivatives against Paenibacillus larvae

Paenibacillus larvae is the causative agent of American foulbrood (AFB), the most serious bacterial disease affecting developing honeybee larvae and pupas. In this study, a library of 24 (thio)glycosides, glycosyl sulfones, 6-O-esters, and ethers derived from d-mannose, d-glucose, and d-galactose having C10 or C12 alkyl chain were evaluated for their antibacterial efficacy against two P. larvae strains. The efficacy of the tested compounds determined as minimal inhibitory concentrations (MICs) varied greatly. Generally, dodecyl derivatives were found to be more potent than their decylated analogs. Thioglycosides were more efficient than glycosides and sulfones. The activity of the 6-O-ether derivatives was higher than that of their ester counterparts. Seven derivatives with dodecyl chain linked (thio)glycosidically or etherically at C-6 showed high efficacy against both P. larvae strains (MICs ranged from 12.5 μM to 50 μM). Their efficacies were similar or much higher than those of selected reference compounds known to be active against P. larvae—lauric acid, monolaurin, and honeybee larval food components, 10-hydroxy-2-decenoic acid, and sebacic acid (MICs ranged from 25 μM to 6400 μM). The high efficacies of these seven derivatives suggest that they could increase the anti-P. larvae activity of larval food and improve the resistance of larvae to AFB disease through their application to honeybee colonies.

Recombinant luciferase-expressing murine gammaherpesvirus 68 as a tool for rapid antiviral screening

Murine gammaherpesvirus 68 (MHV-68) provides a valuable tool to screen novel therapeutic strategies against oncogenic gammaherpesviruses. The development and characterization of antiviral agents usually depend on appropriate screening assays. The aim of this study was to develop rapid and sensitive method for testing antiviral compounds against gammaherpesviruses. For this purpose, a recombinant MHV-68 expressing firefly luciferase (MHV-68/LUC) was constructed. The conditions for MHV-68/LUC infection in Vero cells suitable for novel antiviral screening assay in 96-well plate format were then optimized. The sensitivity of MHV-68/LUC to acyclovir (ACV) and ganciclovir (GCV) was measured by the optimized luciferase activity reduction assay. The 50% inhibition concentration (IC50) values for ACV and GCV were comparable to those determined by conventional plaque reduction assay. Therefore, the luciferase activity reduction assay can efficiently replace the plaque reduction assay. The great advantages of novel assay are represented by the significant reduction in assay time and rapid and objective measurement of the assay. In order to evaluate whether the luciferase activity reduction assay could be used as a screening system for novel antivirals, newly synthesized quinolone/quinoline derivatives were tested for their effects on the replication of MHV-68/LUC in vitro. The compound 2-(1-(b-D-Xylopyranosyl)-1,2,3-triazol-4-yl)-3,4-dibenzyloxy-quinoline showed significant antiviral activity and its IC50 against MHV-68/LUC was estimated to be 1,76 µg/ml. However, this compound was not suitable for in vivo testing due to its narrow selectivity index (SI = 11). Keywords: MHV-68; antiviral screening; luciferase; quinolone/quinoline derivatives.