Immunization with plasmid DNA expressing the caprine arthritis-encephalitis virus envelope gene: quantitative and qualitative aspects of antibody response to viral surface glycoprotein

Saanen goats were vaccinated intradermally with plasmid DNA expressing capr ine arthritis-encephalitis virus (CAEV) rev-env (pENV) or tat-rev-env (pTAT -ENV) or vaccinia virus expressing CAEV env (rWR-63). Sera from all vaccina ted goats immunoprecipitated CAEV surface (SU) and transmembrane (TM) glyco proteins with a dominant response to SU. Antibody response to CAEV SU induc ed by plasmid DNA was relatively biased toward IgG2, whereas vaccinia rWR-6 3 induced predominantly IgG1 antibodies to SU. Differential IgG isotype bia s established by immunization with plasmid or vaccinia vectors was maintain ed following subcutaneous boost with purified CAEV SU in Freund's incomplet e adjuvant (FIA). Goats injected with pUC18 control plasmid followed by imm unization with SU-FIA also had IgG2 biased responses, whereas SU-FIA immuni zation of a goat primed with vaccinia rWR-SC11 without the CAEV env gene in duced a predominant IgG1 response. We conclude that pUC based plasmids expr essing the CAEV env gene promote stable type 1 biased immune responses to p lasmid encoded SU. IgG2 biased response may be due to innate type 1 priming capacity of immunostimulatory CpG motifs in the pUC ampicillin resistance gene. In 2001 Elsevier Science Ltd. All rights reserved.