Microparticles with adsorbed polypeptide-containing molecules formed without the use of surfactant, methods of making such microparticle compositions, and uses thereof, are disclosed. The microparticles comprise a polymer, such as a poly(α-hydroxy acid), a polyhydroxy butyric acid, a polycaprolactone, a polyorthoester, a polyanhydride, and the like. Preferred polymers are poly(D,L-lactide-co-glycolides), more preferably those having a lactide/glycolide molar ratio ranging from 40:60 to 60:40 and having a molecular weight ranging from 20,000 Daltons to 70,000 Daltons. Preferred polypeptide-containing molecules are bacterial and viral antigens (including HIV antigens, meningitis B antigens, streptococcus B antigens, and Influenza A hemagglutinin antigens).
