[The soluble expression and application of human papillomavirus type 58 (HPV58) major capsid protein L1]

Objective The major capsid protein L1 of human papillomavirus type 58 (HPV58 L1) was obtained and identified by prokaryotic expression. Methods The recombinant expression strain pE-SUMO-58 L1 (BL21) was induced by IPTG. The recombinant protein SUMO-58 L1 was expressed in E.coli and identified by SDS-PAGE and Western blot analysis. Then the recombinant protein SUMO-58 L1 was purified by Ni-column and the SUMO-tag was removed by ubiquitin-like protease 1 (ULP1) digestion. Subsequently, the bioactivity of recombinant protein HPV58 L1 was verified by hemagglutination assay (HA). BALB/c mice were immunized with HPV58 L1, and the antibody titers in sera of the immunized mice were detected by ELISA. And then the reaction between the immune serum and the HPV58 L1 protein transiently expressed by HEK293T cells was detected by indirect immunofluorescence assay (IFA). Results The soluble expression of the recombinant protein SUMO-58 L1 was identified by SDS-PAGE and Western blot analysis, with yields of soluble protein SUMO-58 L1 being about 50% of total soluble bacterial proteins. The relative molecular mass (M_r) of SUMO-58 L1 was about 72 000. After Ni-NTA affinity was purified and the SUMO-tag was removed by ULP1 digestion, M_r of recombinant protein HPV58 L1 reached about 58 000. The recombinant protein HPV58 L1 showed hemagglutination activity similar to that of natural HPV, with hemagglutination value of 1:16. After immunizing BALB/c mice, the titer of immune serum observed was about 1:10 240 by ELISA; and the sera of the immunized mice reacted specifically with HPV58 L1 proteins which were transiently expressed in HEK293T cells by IFA. Conclusion The recombinant protein HPV58 L1 also has hemagglutination activity, which can be successfully obtained from E. coli. The sera of the HPV58 L1 protein immunized mice can be used for immunocytochemical detection of HPV58 L1 protein expressed in eukaryotic cells.