A DNA adjuvant encoding a fusion protein between anti-CD3 single-chain Fv and AIMP1 enhances T helper type 1 cell-mediated immune responses in antigen-sensitized mice

T helper type 1 (Th1) cell-mediated immune responses contribute to host defences against intracellular pathogen infections and cancer. Previously, we found that aminoacyl tRNA synthetase-interacting multifunctional protein 1 (AIMP1) activated macrophages and dendritic cells to enhance Th1 responses. Herein, we manipulated this property to improve Th1 immune responses in vivo by constructing a mammalian expression plasmid (pAnti-CD3sFv/AIMP1) encoding AIMP1 fused to the anti-CD3 single-chain Fv (sFv), the smallest unit of the antibody that interacts with the CD3ε region of the T-cell receptor. Intramuscular injection of ovalbumin (OVA)-sensitized BALB/c mice with pAnti-CD3sFv/AIMP1 DNA adjuvant increased the OVA-specific, interferon-γ production by their CD4⁺ T cells and the levels of anti-OVA immunoglobulin G2a (IgG2a) isotype in their sera. Furthermore, the pAnti-CD3sFv/AIMP1 DNA adjuvant decreased interleukin-4 production and anti-OVA IgE levels in the OVA-injected mice. Importantly, the pAnti-CD3sFv/AIMP1 was more efficient than a mixture of pAnti-CD3sFv and pAIMP1 in inducing OVA-specific Th1 immune responses and also in inhibiting OVA-specific Th2 responses during antigen priming. These studies indicated that the pAnti-CD3sFv/AIMP1 fusion DNA adjuvant enhanced Th1 immune responses in antigen-sensitized mice.