Evaluation of varicella-zoster antiviral drugs by a nucleic acid hybridization assay

Expression of variable viruses as herpes simplex glycoprotein D and varicella zoster gE glycoprotein using a novel plasmid based expression system in insect cell

Several prokaryotic and eukaryotic expression systems have been used for in vitro production of viruses’ proteins. However eukaryotic expression system was always the first choice for production of proteins that undergo post-translational modification such as glycosylation. Recombinant baculoviruses have been widely used as safe vectors to express heterologous genes in the culture of insect cells, but the manipulation involved in creating, titrating, and amplifying viral stocks make it time consuming and laborious. Therefore, to facilitate rapid expression in insect cell, a plasmid based expression system was used to express herpes simplex type 1 glycoprotein D (HSV-1 gD) and varicella zoster glycoprotein E (VZV gE). Recombinant plasmids were generated, transfected into insect cells (SF9), and both glycoproteins were expressed 48 h post-infection. A protein with approximately molecular weight of 64-kDa and 98-kDa for HSV-1 gD and VZV gE respectively was expressed and confirmed by SDS. Proteins were detected in insect cells cytoplasm and outer membrane by immunofluorescence. The antigenicity and immunoreactivity of each protein were confirmed by immunoblot and ELISA. Results suggest that this system can be an alternative to the traditional baculovirus expression for small scale expression system in insect cells.

In situ ELISA for the evaluation of antiviral compounds effective against human cytomegalovirus

An in situ ELISA was developed as an improved procedure over the plaque reduction assay for antiviral susceptibility testing of HCMV. Unlike the plaque reduction assay, the ELISA can be completed at 4-5 days post-infection. The effective dose (ED50) of ganciclovir (GCV), acyclovir (ACV), phosphonoacetic acid (PAA), or phosphonoformic acid (PFA), was determined using HCMV strain AD169. The resistance profiles of two laboratory-derived GCV-resistant mutants of HCMV strain AD169 and seven clinical isolates were determined using the ELISA. The ELISA results were confirmed by the plaque reduction assay. The ED50 for GCV with the AD169 control ranged from 3.1 to 6.2 microM with a mean inhibitory concentration of 5.4 +/- 1.4 microM. Six of the clinical isolates were susceptible to GCV (ED50 = 3.1-6.2 microM). The seventh isolate had an ED50 of 50 microM and was resistant to GCV. This ELISA assay is reproducible and relatively simple to perform. The ELISA endpoints are clearly determined and the assay works well with a variety of antiviral compounds.

Drug testing for activity against varicella-zoster virus in hairless guinea pigs

Inoculation of congenitally hairless guinea pigs with varicella-zoster virus (VZV) (Oka strain) results in a self-limited exanthematous infection analogous to varicella in children. Administration of acyclovir or 6-methoxypurine arabinoside modified the course of infection. This model should facilitate pre-clinical testing of putative anti-VZV agents.