A Wide Extent of Inter-Strain Diversity in Virulent and Vaccine Strains of Alphaherpesviruses

Alphaherpesviruses are widespread in the human population, and include herpes simplex virus 1 (HSV-1) and 2, and varicella zoster virus (VZV). These viral pathogens cause epithelial lesions, and then infect the nervous system to cause lifelong latency, reactivation, and spread. A related veterinary herpesvirus, pseudorabies (PRV), causes similar disease in livestock that result in significant economic losses. Vaccines developed for VZV and PRV serve as useful models for the development of an HSV-1 vaccine. We present full genome sequence comparisons of the PRV vaccine strain Bartha, and two virulent PRV isolates, Kaplan and Becker. These genome sequences were determined by high-throughput sequencing and assembly, and present new insights into the attenuation of a mammalian alphaherpesvirus vaccine strain. We find many previously unknown coding differences between PRV Bartha and the virulent strains, including changes to the fusion proteins gH and gB, and over forty other viral proteins. Inter-strain variation in PRV protein sequences is much closer to levels previously observed for HSV-1 than for the highly stable VZV proteome. Almost 20% of the PRV genome contains tandem short sequence repeats (SSRs), a class of nucleic acids motifs whose length-variation has been associated with changes in DNA binding site efficiency, transcriptional regulation, and protein interactions. We find SSRs throughout the herpesvirus family, and provide the first global characterization of SSRs in viruses, both within and between strains. We find SSR length variation between different isolates of PRV and HSV-1, which may provide a new mechanism for phenotypic variation between strains. Finally, we detected a small number of polymorphic bases within each plaque-purified PRV strain, and we characterize the effect of passage and plaque-purification on these polymorphisms. These data add to growing evidence that even plaque-purified stocks of stable DNA viruses exhibit limited sequence heterogeneity, which likely seeds future strain evolution

Choice of comparator in active control trials of new drugs.

Item does not contain fulltextBACKGROUND: When choosing the active control group in a randomized trial, it is important to maintain standard treatment for the therapeutic indication for which a medicine is studied. This choice is relevant not only for demonstrating the efficacy and safety of a new drug, but also for assessing its place in therapy in comparison with existing medicines. Comparative information is important for decisions on prescribing and reimbursement. However, choosing the most suitable comparator is difficult when recommendations on drugs of first choice vary depending on clinical settings and times. OBJECTIVE: To evaluate the choice of comparator in premarketing randomized active control trials (RaCTs) in comparison with recommendations for standard treatment. METHODS: We evaluated drugs that were authorized for use in the European Union market between 1999 and 2005. Information on active comparators in RaCTs was extracted from the European Public Assessment Reports and information on recommendations regarding standard treatment was retrieved from the annual editions of the Dutch reference book on pharmacotherapy. Data on prescribing and indications at the time of authorization and 3 years before authorization were included. The comparator was considered to be in line with standard treatment if there was a similarity in both active substance or therapeutic class and the dosage. RESULTS: For 58 new medications identified, treatment in the active control group was in line with the recommended standard treatment in 108 of 153 (71%) RaCTs at the time of the drug's authorization; 47 (81%) of the new drugs had been compared with the recommended standard treatment in at least one trial. When dissimilarities occurred, none of the comparators had been recommended as standard treatment 3 years earlier (the supposed time of defining the trials' protocol). CONCLUSIONS: Most comparators in the premarketing RaCTs of new medicines were in line with the recommended standard treatment at the moment of marketing authorization. In view of this similarity, most of these trials are also fit for postmarketing decision-making on prescribing and on inclusion in clinical guidelines and reimbursement systems