Fine-mapping of immunodominant linear B-cell epitopes of C.jejuni PEB1 antigen using short overlapping peptides

Abstract

Objective To map the immunodominant linear B-cell epitopes of Campylobacter jejuni (C.jejuni) PEB1 antigen and evaluate the protective immune responses elicited by these epitopes in a mouse model of oral infection with C.jejuni. Methods The B-cell immunodominant PEB1 epitopes were identified using synthetic overlapping peptide ELISA. BALB/c mice were immunized with the immunodominant PEB1 peptides conjugated with KLH plus CFA/IFA, and the IgG titers against these peptides were detected using ELISA. Seven days after the last immunization, the mice were orally infected with C.jejuni 11168, and the bacterial burden and expression of tumor necrosis factor-α (TNF-α) mRNA in the jejunum were analyzed using qRT-PCR in 28 d after the challenge. We assessed the effect of the antibodies against the immunodominant PEB1 epitopes in mediating the opsonophagocytic killing of C.jejuni by HL-60 cells. We also assessed the bacterial burden in the jejunum following C.jejuni challenge in a B cell-knockout mice immunized with the peptides. Results The immunodominant peptides PEB155-72aa, PEB197-114aa, and PEB1211-228aa all induced strong IgG responses to PEB1 antiserum, and the antisera of these immunodominant peptides also showed strong IgG responses to recombinant PEB1. Compared with the antiserum of CFA/IFA, the antisera of these immunodominant peptides induced significantly enhanced opsonophagocytic activity of HL-60 cells (P < 0.01). Both the bacterial burdens and TNF-α mRNA expression level in the jejunum were significantly lowered in the mice immunized with the 3 immunodominant peptides in comparison with the control mice immunized with CFA/IFA (P < 0.01). In B cell-knockout mice, immunization with the 3 peptides did not provide immune protection against C.jejuni, and the bacterial burden in the jejunum after C.jejuni challenge was significantly greater than that in immunized wild-type mice (P < 0.01). Conclusion We successfully identified 3 linear B-cell epitopes of C.jejuni PEB1 (PEB155-72aa, PEB197-114aa, and PEB1211-228aa), which exhibit good immunogenicity and immunoprotective activities and may facilitate the future development of vaccines against C.jejuni infection.

Keywords

• c.jejuni
• peb1
• epitopes peptides
• opsonophagocytosis