Antigen complex of opportunistic bacteria: Assessment of protective properties and toxicity in mice

INTRODUCTION. Medicinal products based on various bacterial antigens effectively prevent diseases caused by opportunisitic bacteria. However, their large-scale use will require improved composition and production process. A promising approach is to develop an antigen complex from Klebsiella pneumoniae, Escherichia coli, Proteus vulgaris, and Staphylococcus aureus.

AIM. This study aimed to examine protective properties and toxicity of antigens from K. pneumoniae, E. coli, P. vulgaris, S. aureus, and the antigen complex in experiments on mice.

MATERIALS AND METHODS. Antigens of K. pneumoniae 204, E. coli F147, P. vulgaris 177, the complex of two S. aureus antigens (1986 and 1991), and the complex of the above antigens were used in the study. Toxicity was evaluated in white male and female SHK mice weighing 18–20 g. A single dose of antigens (50, 100 or 200 μg per mouse) or antigen complex (0.1, 0.2, 0.4, 0.6 mL per mouse) was injected intraperitoneally. Protective properties were studied in female SHK mice weighing 14–16 g. Animals were immunised twice and then infected with live homologous strains of K. pneumonia 204, E. coli F147, P. vulgaris 177, S. aureus 1986, and P. aeruginosa PA103 heterologous strain. For seven days, their survival was monitored; LD50 value and efficiency index was determined.

RESULTS. E. coli, S. aureus and P. vulgaris antigens at all tested doses, and K. pneumoniae antigens at doses of 50 and 100 µg, did not cause toxic effects in mice. 200 µg of K. pneumoniae antigens caused weight loss and animal mortality. Injection of 0.1–0.4 mL of the antigen complex did not cause toxic effects; however, injection of 0.6 mL resulted in manifestations of toxicity. Double immunisation with 0.1 mL antigen complex protected mice against infection with homologous and heterologous strains. Efficiency index was 7.99 for K. pneumonia 204, 11.56 for E. coli F147, 25.90 for P. vulgaris 177, 7.45 for S. aureus 1986, and 4.00 for P. aeruginosa PA103 (р<0,05).

CONCLUSIONS. Test antigens of K. pneumoniae, E. coli, P. vulgaris, S. aureus, and the antigen complex had an acceptable toxicological profile. The antigen complex has shown significant protective properties both against homologous strains (K. pneumoniae, E. coli, P. vulgaris, and S. aureus) and heterologous strain of P. aeruginosa. Thus, the studied antigens and their complex can be used to develop a medicinal product preventing a wide range of opportunistic bacterial infections.

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