Comparison of humoral and cell-mediated immune responses to cationic PLGA microspheres containing recombinant hepatitis B antigen.

Presently available marketed alum adsorbed hepatitis B vaccine used for prophylactic immunization, can effectively elicit humoral immunity but is poor inducer of cell-mediated immunity (CMI). Besides, conventional alum-adjuvant vaccines require multiple injections to achieve long-lasting protective immune responses. Therefore, as a result of insufficient immunization, infections are still the leading killer among diseases. The present investigation was therefore, aimed at developing "single-shot" HBsAg adsorbed microspheres of poly (DL)-lactide-co-glycolide (PLGA) (L/G 50:50 and 75:25) and their capability to stimulate the cell mediated immune response against hepatitis B surface antigen. These microspheres were characterized in vitro for their size, shape polydispersity index, percentage HBsAg adsorption efficiency and in vitro release profile. The immune-stimulating activities were also studied following subcutaneous injection of HBsAg adsorbed PLGA microspheres (single-dose on day 0) and compared with alum adsorbed vaccines (two-doses on 0 and 28 days) in Balb/c mice. Specific cell-mediated immune responses such as lymphocyte transformation assay (stimulation-index) including release of interferon-gamma (IFN-γ), interleukin-2 (IL-2) and nitric-oxide were determined. Cellular responses in case of alum adsorb HBsAg vaccine was very low. These studies demonstrate the potential of cationic polymeric microspheres based vaccine in stimulating cell mediated immune response along with humoral response against hepatitis B.