Introduction: Identifying ideal non typeable Haemophilus influenzae (NTHi) vaccine candidates has not been easy due to extensive sequence and antigenic variation among gene products interacting with the immune system. Protein D (PD) is a highly conserved 42 kDa surface lipoprotein available in all H. influenzae, including NTHi. Methodology: In this study, the gene encoding PD was cloned from H. influenzae and expressed in Escheriachia coli TOPO10 cell in pBAD vector. Arabinose was used to express recombinant protein. In order to purify the protein, Ni-NTA agarose was used to perform affinity chromatography. Purified PD and PD mixed with outer membrane vesicle (OMV) and alum adjuvant were used for subcutaneous immunization in BALB/c mice. After vaccination, IgG responses to PD-OMV, PD-alum, and PD alone were determined by enzyme-linked immunosorbent assay (ELISA). Results: The recombinant PD containing His6 residues showed a molecular weight of 42 kDa. Anti-PD IgG was detected after first immunization in all groups of mice compared to the negative control group, and it increased after first vaccination, but results showed that the addition of OMV to PD led to a remarkable increase in IgG responses. Conclusions: Our results suggest an important role for OMV as an adjuvant and show how it could potentially be used when conjugated to H. influenzae PD or other safe subunit vaccine candidates.
The commensal microflora collection known as microbiota has an essential role in maintaining the host's physiological homeostasis. The microbiota has a vital role in induction and regulation of local and systemic immune responses. On the other hand, the immune system involves maintaining microbiota compositions. Optimal microbiota-immune system cross-talk is essential for protective responses to pathogens and immune tolerance to self and harmless environmental antigens. Any change in this symbiotic relationship may cause susceptibility to diseases. The association of various cancers and auto-immune diseases with microbiota has been proven. Here we review the interaction of immune responses to gut microbiota, focusing on innate and adaptive immune system and disease susceptibility.
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