ABSTRACT
Objective To investigate the distribution and sequence conservation of Hap adhensin encoding gene (hap) in clinical isolates of nontypeable Haemophilus influenzae (NTHi), to screen out and identify the predominant T-and B-cell (T-B) combined antigenic epitopes on Hap protein and to analyze their immunogenicity.Methods Sequence conservation of hap genes in NTHi strains and T-B combined antigenic epitopes were predicted using bioinformatic softwares.PCR was used to amplify the 156 bp segment at 5′-end and the 855 bp segment at 3′-end of hap gene (hap-5′-156 and hap-3′-855) and the amplified products were sequenced.Phage display systems of seven T-B combined antigenic epitopes located on the 55 aa segment at N-terminal and the 285 aa segment at C-terminal of Hap protein (Hap-N52 and Hap-C285) were constructed.Western blot assay and ELISA were performed to detect the antigenicity and immunoreactivity of different T-B combined epitopes displayed by recombinant phage PⅢ protein (rPⅢ).Results Hap protein encoded by the hap gene in NTHi was located on membrane surface.Sequences of the 156 bp segment at 5′-end and the 855 bp segment at 3′-end of hap genes extracted from different NTHi strains were relatively conservative, but many mutations were found in sequences at the middle regions of these hap genes.All of the 56 NTHi strains carried hap-5′-156 and hap-3′-855 segments and shared 92.3％-100％ identities in nucleotide and amino acid sequences of these segements.Hap-N5-24 in the Hap-N52 segment as well as Hap-C4-27, Hap-C28-47, Hap-C114-129, Hap-C150-173, Hap-C200-227 and Hap-C241-267 in the Hap-C285 segment was predicted as the T-B combined antigenic epitope with a higher score and less mutations.Results of Western blot assay and ELISA confirmed that the rPⅢ-displayed Hap-C4-27 and Hap-C150-173 epitopes presented clear hybridization bands with NTHi antisera, and 96.9％ (63/65) and 92.3％ (60/65) of serum samples from children with NTHi infection were positive for antibodies against Hap-C4-27 and Hap-C150-173 epitopes, respectively.Conclusion The gene of hap is widely distributed in clinical isolates of NTHi.Moreover, sequences of the 156 pb segment at 5′-end and the 855 bp segment at 3′-end of hap gene are conservative.Hap-C4-27 and Hap-C150-173 are the predominant T-B combined antigenic epitopes on Hap protein, suggesting that they can be used as epitope candidates for developing multiple antigenic peptide vaccines against NTHi.
ABSTRACT
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.
ABSTRACT
ObjectiveTo generate a prokaryotic expression system of series predominant epitopes (UreB322 and UreB527) of Helicobacter pylori UreB protein,and to synthesize a multiple antigenic peptide (MAP) vaccine by linking both the two epitopes with a peptide carrier (Poly-Asp-Lys),and to determine the immunogenicity and immunoprotection of the MAP vaccine.MethodsLinking primer PCR was performed to generate an enterokinase(EK) site-containing series UreB322 and UreB527 epitope encoding gene for construction of its prokaryotic expression system.The expressed target recombinant fusion protein 8 ×[rEK-UreB322-EK-UreB527-EK] was hydrolyzed with EK and then rUreB322-EK and rUreB527-EK epitope peptides were extracted using a Sephadex G-25 column.rUreB322-EK,rUreB527-EK and Poly-Asp-Lys were linked using carbodiimide method to produce a MAP vaccine (MAP-rUreB322/B527).The antigenicity and immunoreactivity of each of the two epitope peptides and MAP-rUreB322/527 were determined by ELISA and Western blot assay.An animal H.pylori strain SS1-infected model in BALB/c mice was used to detect the immunoprotection of MAP-rUreB322/527.ResultsAn octuple-repeated series UreB322-UreB527 encoding gene and its prokaryotic expression system were obtained.The yield of target fusion protein 8×[rEKUreB322-EK-rUreB527-EK] was as high as 48％ of the total bacterial proteins.EK hydrolyzed the target fusion protein completely into rUreB322-EK and rUreB527-EK peptides.The linking ratio of rUreB322-EK,rUreB527-EK and Poly-Asp-Lys was as high as 92.5％.The antibody against whole cell of H.pylori and rUreB-IgG could recognize and combine with the rUreB322-EK,rUreB527-EK or MAP-rUreB322/527.The specific serum antibody level in MAP-rUreB322/527-immunized mice was significantly higher than that in rUreB-immunized mice (P＜0.05).The immunoprotective rates(83.3％ and 91.7％ ) by immunization with50 or 100 μg MAP-rUreB322/527 in the H.pyloristrain SSI-infected mice were significantly higher that those(d1.7％ and 50.0％ ) by immunization with equal rUreB(P＜0.05).ConclusionAn gene composed for encoding a repeated series predominant epitopes of H.pylori UreB protein and its prokaryotic expression system are successfully generated in this study.MAP-rUreB322/527,the multiple antigenic peptide vaccine based on the two predominant epitopes of UreB,can noticeably increase the immunoprotection in H.py/or/infected mice.