Pseudorabies virus nucleocapsid antigen for skin testing in swine

A procedure is described for the production of an effective pseudorabies virus skin test antigen consisting of nucleocapsids. The nucleocapsids were prepared by disruption of pseudorabies virus-infected pig kidney cells and nonionic detergent removal of the viral envelope. This preparation was noninfectious for pig kidney cell cultures and mice. Swine that had recovered from a pseudorabies virus infection and were injected intradermally with the nucleocapsid antigen developed a delayed type hypersensitivity response similar to that induced by inactivated virion antigen. The major advantage of the nucleocapsid antigen is that the occasional problem of seroconversion that is encountered with the virion antigen is avoided.