in vivo characterization of fusion protein comprising of a1 subunit of shiga toxin and human gm-csf: assessment of its immunogenicity and toxicity

background: most cancer cells become resistant to anti-cancer agents. in the last few years, a new approach for targeted therapy of human cancer has been developed using immunotoxins which comprise both the cell targeting and the cell killing moieties. methods: in the present study, the recombinant shiga toxin a1 subunit fused to human granulocyte-macrophage colony stimulating factor (a1-gm-csf), previously produced in e. coli, was further characterized. results: the recombinant protein could cause 50% cytotoxicity and induced apoptosis in cells bearing gm-csf receptors. the non-specific toxicity of the fusion protein was assessed in c57bl/6 and balb/c mice. no mortality was observed in either group of mice, with different concentration of fusion protein. conclusion: the lymphocyte proliferation assay, induction of specific igg response and a mixed (th1/th2) response were observed only in balb/c mice. the mixed response in balb/c mice (th1/th2) could be explained on the basis of the two components of the fusion protein i.e. a1 and gm-csf.