Abstract:

Objective To construct Acinetobacter baumannii SmpA/Omp22/NlpA（1 ⁃ 128） trivalent fusionprotein and investigate its immunogenicity. Methods The smpA/omp22/nlpA（1⁃384） fusion gene was obtained byartificial synthesis and PCR amplification，the fusion gene fragment was cloned into plasmid pColdI and trans⁃formed into E.coli BL21 for prokaryotic expression. BALB/c mice were inoculated subcutaneously with the purifiedrecombinant fusion protein formulated with Freund′s adjuvant three times. At the same time，the adjuvant controlgroup and the PBS control group were set up. Blood was collected from the mice orbital canthus on day 7 and 21after the last immunization，and the serum antibody titers were detected by ELISA. Spleen lymphocytes were isolatedand stimulated by the recombinant fusion protein in vitro，the proliferation of lymphocytes and the release level ofIFN⁃γ and IL⁃ were detected. Results A 5.9 kb recombinant plasmid was constructed and identified. The recom⁃binant plasmid can express a recombinant fusion protein with molecular weight about 56 kDa. Antigen specific anti⁃body IgG was detected in the serum of the recombinant fusion protein immunized mice. The proliferative activity ofspleen lymphocyte from the recombinant fusion protein immunized mice was significantly higher than that from theadjuvant and PBS control group（P < 0.001）. The IL⁃4 release level of the spleen lymphocytes from the recombinantfusion protein immunized mice was significantly higher than that from the control group（P < 0.01），while the IFN⁃γrelease level showed no significantly difference. Conclusion The SmpA/Omp22/NlpA（1⁃128） fusion protein of Aci⁃netobacter baumannii was successfully prepared and showed strong immunogenicity after mice immunization.

Key words: Acinetobacter baumannii, SmpA, Omp22, NlpA, immunogenicity, fusion protein