engleski

Effect of liposomal formulations and PGM on the immune reaction to ovalbumin in mice - influence on antigen specific IgG1/IgG2a balance

The effects of different liposomal formulations of ovalbumin (OVA) and immunostimulating peptidoglycan monomer (PGM), respectively, on humoral immune response in CBA mice were studied. PGM is an adjuvant active compound that exhibits its adjuvant properties after very short persistance in an organism1. We hypothesised that its action could be improved if we would find a way to keep it longer in the immunised animal2. That's why we started to formulate PGM with liposomes, already shown to be depot acting adjuvants. Here we report on the adjuvant effect of two different combinations of liposomes and PGM tested in mice model, with ovalbumin as an antigen. The first preparation was a simple mixture of OVA, PGM and liposomes, the second one was the formulation where both OVA and PGM were incorporated into liposomes. Separate groups of CBA mice were immunised three times in 21 days intervals with these two preparations. Control groups for the first one were mice immunised with a mixture of OVA and PGM as well as those immunised with OVA mixed with liposomes. For the second preparation control group received only OVA (without PGM) incorporated into liposomes. Positive control for all groups were mice immunised with OVA in CFA/IFA adjuvant. Reference group were mice immunised with OVA in saline. Sera of immunised mice were screened after boosters for the total OVA specific IgG (anti-OVA IgG), OVA specific IgG1 and IgG2a, using respective ELISAs established in the laboratory. The quantity of anti-OVA IgG, as well as the IgG1/IgG2a ratio (as indication of Th2/Th1 immune response direction) were compared between experimental groups. The two tested formulations of PGM and liposomes induced significantly higher levels of anti-OVA IgG in comparison to control groups after both boosters, although the quantity of anti-OVA obtained by CFA/IFA was not reached. Liposomes (without PGM) increased anti-OVA IgG only after the first booster, being ineffective after the second in comparison to negative control (OVA in saline). But, liposomes were the most stimulative adjuvant in inducing IgG2a class of OVA-specific antibodies, shifting strongly the immune response towards Th1 pathway. PGM had immunostimulating effect on both anti-OVA IgG1 and IgG2a indicating a mixed Th2/Th1 response. The anti-OVA IgG1/IgG2a ratios obtained by the two formulations of PGM and liposomes were higher then the one obtained by liposomes solely. It could be concluded that appropriate formulations of antigen, PGM and liposomes might differently affect the humoral immune response and direct the switch in the type of immune response (Th1/Th2). 1J. Tomašić, I. Hanzl-Dujmović, B. Špoljar, B. Vranešić, M. Šantak, A. Jovičić. Vaccine 18 (2000) 1236-1243 2B. Halassy, M. Krstanović, R. Frkanec, J. Tomašić. Vaccine 21 (2002) 761-766

liposomes; PGM; ovalbumin; imunoglobulin

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