Mycobacterial HSP70 as an adjuvant in the design of an idiotype vaccine against a murine lymphoma

Mycobacterial HSP70 protein coupled with ovalbumin is known to elicit antigen-specific CD8+ T-cell response. We investigated whether anti-idiotype immunity can likewise be enhanced using a conjugate of recombinant mycHSP70 and the Ig Id in a murine lymphoma model, A20. Plasmids were constructed of A20 tumor to generate A20Id-HSP70 (scFv-H), unconjugated A20Id (scFv), and mycHSP70 (H) recombinant proteins. We evaluated their relative efficacy in activating anti-tumor immunity that can reduce the mortality of tumor-challenged BALB/c mice; significantly, a longer term protection (>50% of the population) was observed in mice vaccinated with scFv-H compared to those receiving the scFv or H proteins. Concomitantly a much higher-level activation in anti-A20 cytotoxic T-cell activity, IFN-γ secretion and predominantly anti-A20 IgG2a response was also observed with the scFv-H group. Thus, conjugating HSP70 with the A20Id renders the latter significantly immunogenic and affords longer protection against A20 tumor progression.