Further characterization of the biological and pathogenic properties of erythromelalgia-related poxviruses

Six isolates of erythromelalgia-related poxvirus (ERPV) were characterized with respect to host range, c.p.e. and inclusions, pock formation on chorioallantoic membrane (CAM), morphogenesis, serological reactivity, pathogenesis in animals and DNA restriction fragment profile. The results suggest that ERPV is either a new member of the Orthopoxvirus genus or a subspecies of ectromelia virus. Evidence is provided that (i) ERPV has a wide host range in vitro in which characteristic viral c.p.e. and inclusion bodies are induced; (ii) ERPV, unlike ectromelia virus, causes the formation of tiny greyish-white pocks on CAM both at 34 degrees C and 39 degrees C; (iii) eosinophilic A-type inclusions of ERPV do not contain viral particles; (iv) ERPV isolates are neutralized by both rabbit anti-vaccinia virus and mouse anti-ectromelia virus sera, but not vice versa; (v) young rabbits are not susceptible to ERPV by skin and/or corneal scratch infection even though ERPV is lethal for mice by intraperitoneal inoculation; (vi) the HindIII and SalI fragment profiles of ERPV P-4 DNA are similar to, but obviously different from, those of Chinese ectromelia virus. These biological and pathogenic characteristics of ERPV are distinguishable from those of other members of the genus Orthopoxvirus currently described in the literature.