The immune response to vaccinia virus is significantly reduced after scarification with TK- recombinants as compared to wild-type virus

Although it is unlikely that large-scale vaccination against smallpox will ever be required again, it is conceivable that the need may arise to vaccin ate against a human orthopoxvirus infection. A possible example could be th e emergence of monkey poxvirus (MPV) as a significant human disease in Afri ca. Vaccinia virus (VV) recombinants, genetically modified to carry the imm unogenic proteins of other pathogenic organisms, have potential use as vacc ines against other diseases present in this region. The immune response to parental wild-type (wt) or recombinant VV was examined by binding and funct ional assays, relevant to protection: total IgG, Ige subclass profile, B5R gene product (gp42)-specific IgG, neutralizing antibodies and class I-media ted cytotoxic lymphocyte activity. There was a substantial reduction in the immune response to VV after scarification with about 10(8) PFU of recombin ant as compared to wt virus. These data suggest that to achieve the levels of immunity associated with protection against human orthopoxvirus infectio n, and to control a possible future outbreak of orthopoxvirus disease, the use of wt VV would be necessary.