A-type inclusion markers of wild white and other variola-related poxviruses.

possibility of the natural reservoir of variola virus among wild animals grew more important. Monkeypox virus was isolated from 20 clinical smallpox cases in West Africa among populations with close contacts with wild monkeys, but its epidemiological and virological differentiation from variola viruses was not difficult. During the virological studies of human monkeypox virus infections, a group of variola-like viruses called •gwild white viruses•h have been isolated from animal tissues. These viruses have been so far indistinguishable from variola viruses by laboratory markers including pock formation on chick chorioallantoic membranes (CAM) and CPE on cultured cells (Baxby, 1975). Two of them were isolated from apparently normal cynomolgus monkeys imported into Holland, two from specimens taken in Zaire from a chimpanzee and a monkey of unidentified species (Gispen and Brand-Saathof, 1972), and the other two from tissues of African wild rodents, Mastomys natalensis and Helioscorus rubobrachium (Marennikova, Shelukhina and Shenkman, 1975). As these viruses have been isolated from healthy animals, it should be suggested that they are capable of maintaining latent infection. It is thus urgently needed to find out any characteristic marker to differentiate wild white viruses from variola ones. As a candidate marker for differentiation, we checked the A-type inclusion (ATI) markers which are associated mainly with cowpox and mousepox (ectromelia) viruses. The ATI marker has been established to be controlled by viral gene, being expressed equally on a wide range of host cells, and to be composed of two characteristics of forming ATI bodies in the cytoplasm (A+) and of progeny virions to be incorporated into or adsorbed onto the ATI bodies formed (V+)