RESUMO
The aim of this study is to investigate the distribution and sequence conservation of P6 outer membrane protein (OMP6)-encoding gene of nontypeable Haemophilus influenzae isolates as well as screen and identify the predominant T-and B-cell (T-B)-combined antigenic epitopes in OMP6 sequences and their immunogenicity.The entire omp6 genes of NTHi isolates were amplified by PCR and the amplification products were sequenced after T-A cloning.By using bioinformatic softwares,the sequence conservation and membrane location of OMP6 were analyzed as well as the T-B-combined antigenic epitopes in OMP6 were predicted.The immunogenicity and immunoreactivity of T-B-combined antigenic epitope peptides displayed by recombinant phage PⅢ proteins (rPⅢ) were determined by Western Blot assay and ELISA.The PCR showed that all the 35 NTHi isolates tested were detectable for omp6 gene.The identities of nucleotide and amino acid sequences of omp6 genes from 28 strains in the NTHi isolates were 98.3％-100％ and 99.3 ％-100％,respectively.OMP6 of NTHi was predicted as an outer membrane superficial protein that contains OMP6-2-25,OMP6-61-86 and OMP6-98-126 predicted T-B-combined antigenic epitopes.The immunoblotting assay and ELISA confirmed that OMP6-2-25 presented stronger hybridization band with NTHi antisera while 96.9％ (59/62),69.4％ (43/62) and 74.2％ (46/62) of serum samples from NTHi-infected children were positive for OMP6-2-25,OMP6-61-86 and OMP6-98-126 T-B-combined antigenic epitope peptides,respectively.All the results lead to a conclusion thatomp6 is an extensive distribution and sequence conserved gene of NTHi,and OMP6-2-25 is the predominant T-B-combined antigenic epitopes which can be used as the candidates for developing multiple antigenic peptide vaccine against NTHi.