Vaccination of rhesus Macaques with a recombinant measles virus expressing interleukin-12 alters humoral and cellular immune responses

Lack of a vaccine for infants and immunosuppression after infection are problems associated with measles virus ( MV). Because interleukin ( IL) - 12 has been used successfully as a vaccine adjuvant and because inhibition of IL- 12 expression has been associated with immunosuppression during measles, the addition of IL- 12 may enhance the immune response to MV. To determine the effect of IL- 12 supplementation, rhesus macaques were vaccinated with a recombinant MV expressing IL- 12; these macaques had increased interferon- gamma production by CD4(+) T cells, decreased production of IL- 4, and lower levels of MV- specific immunoglobulin G4 and neutralizing antibody. Lymphoproliferative responses to mitogen were not improved. IL- 12 supplementation altered the T helper type 2 bias of the immune response after MV vaccination, had a detrimental effect on the protective neutralizing antibody response, and did not improve other manifestations of immunosuppression. Reduced IL- 12 levels are not the sole factor in MV- induced immunosuppression.