Broad Worldwide b Cowpox Rodent, a cow, human, cat, etc. United States Uasin Gishu Horse Medium Eastern Africa a Primary host. As noted, the viral particles contain approximately 200 proteins, about half structural and half nonstructural. Their internal structure is complex. The core is composed of tightly compressed nucleoprotein.
Poxviruses contain both specific and common proteins.
The common proteins induce cross-reactive immunity and account for the ability to vaccinate against disease from another poxvirus of the same genus. There are at least 10 enzymes present in the particle that mediate gene expression. The infection process produces many progeny that are replicas of the parent virus. The first step in the cycle of infection is attachment of the invading virion to the surface of the host cell. Usually the viral DNA genetic material cannot be replicated until it is released from the virion into the host cell.