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

Abstract

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 °C and 39 *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 HindlII and Sail fragment profiles ofERPV 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.

Genome Sequence of Erythromelalgia-Related Poxvirus Identifies it as an Ectromelia Virus Strain

“…The presence of a deletion in the ITR and small deletions within ORFs of ECTV-Nav relative to ERPV and ECTV-Mos, could suggest that the ECTV-Nav isolate used for sequencing was not the immediate progenitor of ERPV. Although some biological differences between ERPV and ECTV were previously reported [11], the ECTV was a Chinese isolate and its similarity to the ECTV-Nav was not determined.…”

“…The identification of ERPV as a strain of ECTV is perplexing, given its reported isolation from the pharynx of students in rural China [11] and the absence of other reports of ECTV infection of humans. Because 5 of the 6 original virus isolations occurred in culture using two different cell lines with newborn bovine serum in the medium, the virus was considered unlikely to be a laboratory contaminant [11].…”

“…Virus isolates from throat swabs of six individuals in three locations suffering from erythromelalgia were characterized [4], [10]. In five cases the virus was isolated directly in cell culture and in another was first passaged in mice [11]. In addition, the sera from patients with epidemic erythromelalgia were reported to have a higher incidence of ERPV antibody (39.2%) compared to non-symptomatic local students (11.8%) and sera of controls from the United States (11.9%) [12].…”

“…Electron microscopic examinations indicated that the isolated virus belongs to the poxvirus family [13]. Further analysis of the biological, serological and pathogenic properties suggested that erythromelalgia-related poxvirus (ERPV) is a member of the orthopoxvirus genus [11]. A restriction enzyme profile of the ERPV DNA resembled but was distinguishable from a Chinese strain of ectromelia virus (ECTV), the causative agent of mousepox [14].…”

“…The susceptibility of mice to ERPV and the formation of A-type inclusion bodies in the cytoplasm were also consistent with ECTV. However, there were apparent differences between the Chinese strain of ECTV and ERPV with regard to pock morphology on the chicken chorioallantoic membrane, pathogenicity for rabbits, and the ability of ERPV to be neutralized by anti-vaccinia virus and anti-ECTV sera from rabbits but not vice-versa [11]. Moreover, ECTV is not known to cause disease in humans.…”