This paper reports the use of a coating process based on supercritical fluid technology to prepare a solvent-free microparticles, loaded with a polymannopeptide (polyactin,PAA) for enhanceing optimal host response in cancer immunotherapy.Microparticles were characterized as regards their morphology, drug content and in vitro release . A prolonged release of the PAA had been achieved over a 24 h period from microparticles coated with the lipidic compound, which produced a more homogeneous, film-forming coating. Furthermore, it was shown that PAA did not undergo any degradation under the supercritical conditions used in the coating process. In vitro immunoactivity and anti-tumor effect analysis results showed that the PAA microsphere could efficiently trigger the induction of cytotoxic T lymphocytes (CTL) in a sustained manner.