PRODUCTION OF MOUSE ANTI-CD4 ANTIBODIES BY DNA-BASED IMMUNIZATION

The intramuscular injection of plasmid DNA encoding an antigenic prote in has been developed recently as a tool for immunization. DNA-based i mmunization was shown to generate immune responses against the encoded antigen in diverse animal species. In this report, we present the use of DNA-based immunization for the production of antibodies to CD4, a human leukocyte surface molecule. Mice were injected intramuscularly w ith eukaryotic expression vector containing cDNA encoding CD4 protein, termed CD4-DNA, and were subsequently assayed for anti-CD4 antibody p roduction by indirect immunofluorescence. Sera collected from 2 of 3 i noculated mice reacted with CD4 expressing transfected COS cells and S up-T1 cells. Anti-CD4 antibody activity was abolished by adsorption wi th CD4 molecule exppressing cells. CD4(+) cell depleted lymphocytes we re also used to confirm the specificity of the anti CD4 antibodies pre sent in immune serum. CD4-DNA immune serum reacted with approximately 1/3 of freshly isolated lymphocytes but to very few cells in the CD4() cells-depleted preparation. CD4-DNA immunized sera was used to enume rate CD4(+) cells in the peripheral blood of a healthy donors and 2 AI DS patients. The number of CD4(+) cells estimated by DNA immunized ser a was very similar to estimates using standard anti-CD4 monoclonal ant ibody Leu3a. DNA-based immunization is therefore capable of raising an tibodies to human leukocyte surface antigens. This technology may be u seful for producing antibodies to other cell surface antigens in mice or other animals.