Combined intrarectal/intradermal inoculation of recombinant Mycobacterium bovis bacillus Calmette-Guérin (BCG) induces enhanced immune responses against the inserted HIV-1 V3 antigen

Non-Muscular Invasive Bladder Cancer: Re-envisioning Therapeutic Journey from Traditional to Regenerative Interventions

Non-muscular invasive bladder cancer (NMIBC) is one of the most common cancer and major cause of economical and health burden in developed countries. Progression of NMIBC has been characterized as low-grade (Ta) and high grade (carcinoma in situ and T1). The current surgical intervention for NMIBC includes transurethral resection of bladder tumor; however, its recurrence still remains a challenge. The BCG-based immunotherapy is much effective against low-grade NMIBC. BCG increases the influx of T cells at bladder cancer site and inhibits proliferation of bladder cancer cells. The chemotherapy is another traditional approach to address NMIBC by supplementing BCG. Notwithstanding, these current therapeutic measures possess limited efficacy in controlling NMIBC, and do not provide comprehensive long-term relief. Hence, biomaterials and scaffolds seem an effective medium to deliver therapeutic agents for restructuring bladder post-treatment. The regenerative therapies such as stem cells and PRP have also been explored for possible solution to NMIBC. Based on above-mentioned approaches, we have comprehensively analyzed therapeutic journey from traditional to regenerative interventions for the treatment of NMIBC.

Development of a Live Recombinant BCG Expressing Human Immunodeficiency Virus Type 1 (HIV-1) Gag Using a pMyong2 Vector System: Potential Use As a Novel HIV-1 Vaccine

Even though the rate of new human immunodeficiency virus type 1 (HIV-1) infections is gradually decreasing worldwide, an effective preventive vaccine for HIV-1 is still urgently needed. The recombinant Mycobacterium bovis BCG (rBCG) is promising for the development of an HIV-1 vaccine. Recently, we showed that a recombinant Mycobacterium smegmatis expressing HIV-1 gag in a pMyong2 vector system (rSmeg-pMyong2-p24) increased the efficacy of a vaccine against HIV-1 in mice. Here, we evaluated the potential of an rBCG expressing HIV-1 p24 antigen Gag in pMyong2 (rBCG-pMyong2-p24) in a vaccine application for HIV-1 infection. We found that rBCG-pMyong2-p24 elicited an enhanced HIV-1 p24 Gag expression in rBCG and infected antigen-presenting cells. We also found that compared to rBCG-pAL-p24 in a pAL5000 derived vector system, rBCG-pMyong2-p24 elicited enhanced p24-specific immune responses in vaccinated mice as evidenced by higher levels of HIV-1 Gag-specific CD4 and CD8 T lymphocyte proliferation, gamma interferon ELISPOT cell induction, antibody production, and cytotoxic T lymphocytes (CTL) responses. Furthermore, rBCG-pMyong2-p24 showed a higher level of p24-specific Ab production than rSmeg-pMyong2-p24 in the same pMyong2 vector system. In conclusion, our data indicated that a live recombinant BCG expressing HIV-1 Gag using a pMyong2 vector system, rBCG-pMyong2-p24 elicited an enhanced immune response against HIV-1 infections in a mouse model system. So, rBCG-pMyong2-p24 may have the potential as a prime vaccine in a heterologous prime-boost vaccine strategy for HIV-1 infection.

Newborn mice vaccination with BCG.HIVA²²² + MVA.HIVA enhances HIV-1-specific immune responses: influence of age and immunization routes

We have evaluated the influence of age and immunization routes for induction of HIV-1- and M. tuberculosis-specific immune responses after neonatal (7 days old) and adult (7 weeks old) BALB/c mice immunization with BCG.HIVA(222) prime and MVA.HIVA boost. The specific HIV-1 cellular immune responses were analyzed in spleen cells. The body weight of the newborn mice was weekly recorded. The frequencies of HIV-specific CD8(+) T cells producing IFN-γ were higher in adult mice vaccinated intradermally and lower in adult and newborn mice vaccinated subcutaneously. In all cases the IFN-γ production was significantly higher when mice were primed with BCG.HIVA(222) compared with BCGwt. When the HIV-specific CTL activity was assessed, the frequencies of specific killing were higher in newborn mice than in adults. The prime-boost vaccination regimen which includes BCG.HIVA(222) and MVA.HIVA was safe when inoculated to newborn mice. The administration of BCG.HIVA(222) to newborn mice is safe and immunogenic and increased the HIV-specific responses induced by MVA.HIVA vaccine. It might be a good model for infant HIV and Tuberculosis bivalent vaccine.

Mucosal HIV transmission and vaccination strategies through oral compared with vaginal and rectal routes

IMPORTANCE OF THE FIELD

There are currently over thirty million people infected with HIV and there are no vaccines available to prevent HIV infections or disease. The genitourinary, rectal and oral mucosa are the mucosal HIV transmission routes. An effective vaccine that can induce both systemic and local mucosal immunity is generally accepted as a major means of protection against mucosal HIV transmission and AIDS.

WHAT THE READER WILL GAIN

Structure and cells that comprise the oral, vaginal and rectal mucosa pertaining to HIV transmission and vaccination strategies through each mucosal route to prevent mucosal and systemic infection will be discussed.

AREAS COVERED IN THIS REVIEW

Covering publications from 1980s through 2010, mucosal transmission of HIV and current and previous approaches to vaccinations are discussed.

TAKE HOME MESSAGE

Although oral transmission of HIV is far less common than vaginal and rectal transmissions, infections through this route do occur through oral sex as well as vertically from mother to child. Mucosal vaccination strategies against oral and other mucosal HIV transmissions are under intensive research but the lack of consensus on immune correlates of protection and lack of safe and effective mucosal adjuvants and delivery systems hamper progress towards a licensed vaccine.

Molecular characterization of heterologous HIV-1gp120 gene expression disruption in mycobacterium bovis BCG host strain: a critical issue for engineering mycobacterial based-vaccine vectors

Mycobacterium bovis Bacillus Calmette-Guérin (BCG) as a live vector of recombinant bacterial vaccine is a promising system to be used. In this study, we evaluate the disrupted expression of heterologous HIV-1gp120 gene in BCG Pasteur host strain using replicative vectors pMV261 and pJH222. pJH222 carries a lysine complementing gene in BCG lysine auxotrophs. The HIV-1 gp120 gene expression was regulated by BCG hsp60 promoter (in plasmid pMV261) and Mycobacteria spp. α-antigen promoter (in plasmid pJH222). Among 14 rBCG:HIV-1gp120 (pMV261) colonies screened, 12 showed a partial deletion and two showed a complete deletion. However, deletion was not observed in all 10 rBCG:HIV-1gp120 (pJH222) colonies screened. In this study, we demonstrated that E. coli/Mycobacterial expression vectors bearing a weak promoter and lysine complementing gene in a recombinant lysine auxotroph of BCG could prevent genetic rearrangements and disruption of HIV 1gp120 gene expression, a key issue for engineering Mycobacterial based vaccine vectors.

A prime-boost immunisation regimen using recombinant BCG and Pr55(gag) virus-like particle vaccines based on HIV type 1 subtype C successfully elicits Gag-specific responses in baboons

Mycobacterium bovis BCG is considered an attractive live bacterial vaccine vector. In this study, we investigated the immune response of baboons to a primary vaccination with recombinant BCG (rBCG) constructs expressing the gag gene from a South African HIV-1 subtype C isolate, and a boost with HIV-1 subtype C Pr55(gag) virus-like particles (Gag VLPs). Using an interferon enzyme-linked immunospot assay, we show that although these rBCG induced only a weak or an undetectable HIV-1 Gag-specific response on their own, they efficiently primed for a Gag VLP boost, which strengthened and broadened the immune responses. These responses were predominantly CD8+ T cell-mediated and recognised similar epitopes as those targeted by humans with early HIV-1 subtype C infection. In addition, a Gag-specific humoral response was elicited. These data support the development of HIV-1 vaccines based on rBCG and Pr55(gag) VLPs.

Recombinant Mycobacterium bovis BCG vector system expressing SIV Gag protein stably and persistently induces antigen-specific humoral immune response concomitant with IFN gamma response, even at three years after immunization

A vaccine against HIV-1 infection absolutely needs the ability to effectively elicit virus-specific immunity over a long term; nevertheless, there have been few studies indicating that the immunoinductivity of such a candidate vaccine has been researched for several years running. In a previous report, we demonstrated that recombinant BCG (rBCG) expressing the full-length gag gene of simian immunodeficiency virus (SIV) (rBCG-SIVgag) induced Gag-specific delayed-type hypersensitivity, T cell proliferation, gamma interferon (IFN gamma), and serum IgG responses in guinea pigs immunized intradermally (i.d.) with 0.1 mg for the 1-year period of study. Especially, the production of long-lasting Gag-specific serum IgG in the vaccinated animals perhaps reflects the persistent antigenic stimulation by rBCG-SIVgag. How long, we questioned, will such immune responses to Gag engendered by the rBCG-SIVgag vaccination persist without booster immunizations? To learn this, we examined Gag-specific IgG production in sera and Gag-specific IFN gamma mRNA expression in peripheral blood mononuclear cells (PBMC) in guinea pigs vaccinated with rBCG-SIVgag i.d. (0.1 mg) or orally (80 mg x 2) during a 3-year period. As a result, Gag-specific serum IgG was highly generated for 3 years at similar levels between the i.d. and the orally immunized guinea pigs (IgG2>IgG1). The enhancement of IFN gamma mRNA expression by in vitro restimulation with Gag antigen was also detected in PBMC from the two immunization groups throughout the 3-year observation period. In guinea pigs immunized i.d. with rBCG-SIVgag, a high level of Gag-specific IFN gamma response was observed at 1 year after vaccination, whereas the response has waned gradually. The current study indicates that i.d. and oral inoculations of rBCG-SIVgag elicit stable, strong, Gag-specific serum IgG production while exhibiting the different kinetics of Gag-specific IFN gamma responses between i.d. and oral vaccination routes. This suggests that the rBCG vector system expressing an appropriate size of foreign antigen gene should be suited for the induction of the antigen-specific humoral immunity concomitant with an IFN gamma response.

Rabbits immunised with recombinant BCG expressing the cottontail rabbit papillomavirus (CRPV) L2E7E2 genes induces regression of established papillomas

We previously demonstrated in a cottontail rabbit papillomavirus (CRPV) challenge model that recombinant Bacille Calmette-Guerin (rBCG) could potentially be used as a prophylactic vaccine vehicle to deliver papillomavirus proteins. In this study we investigated whether regression of CRPV-induced papillomas could be achieved following immunisation of out-bred New Zealand White rabbits with rBCG expressing CRPVL2, CRPVE2, CRPVE7 or CRPVL2E7E2 proteins. Rabbits immunised with rBCG/CRPVL2E7E2 had papillomas that were largely suppressed and were significantly smaller compared to the rBCG negative control group (P</=0.01). In addition, four of the six rabbits immunised with rBCG/CRPVL2E7E2 had papillomas that completely regressed 1.5 weeks post third immunisation. Rabbits immunised with rBCG/CRPVL2, rBCG/CRPVE7, or rBCG/CRPVE2 had papillomas that were significantly smaller than the negative control rabbits (P</=0.05). The findings in this study suggest that BCG could probably be used as a vaccine delivery vehicle for human papillomavirus proteins as a possible therapeutic vaccine.

Progress towards an HIV vaccine based on recombinant bacillus Calmette-Guérin: failures and challenges

The need for an affordable, safe and effective HIV vaccine has never been greater. As the immunogenicity of all the vaccine vectors being evaluated currently in human populations is limited, novel vaccine strategies are needed to stimulate the innate immune system, to generate high levels of neutralizing antibodies and to induce strong cell-mediated and mucosal immunity. There is strong evidence for a role for cytotoxic T lymphocytes in the containment of HIV replication. Several vaccine approaches have been tested to elicit anti-HIV cytotoxic T-lymphocyte responses. One promising approach is Bacillus Calmette-Guérin (BCG) as a bacterial live recombinant vaccine vehicle. BCG has a long record of safety in humans and is able to induce long-lasting immunity. In this review, we describe the limitations and challenges of developing a recombinant BCG-based HIV vaccine. We also emphasize possible approaches for overcoming the plasmid instability in vivo and the low levels of gene expression and immunogenicity induction. Today, projects all over the world are focused on the development of an AIDS vaccine. Overcoming the remaining scientific, logistical and financial hurdles to the development of an effective HIV vaccine will require real imagination and firm commitment from all stakeholders.

Mycobacterial codon optimization of the gene encoding the Sm14 antigen of Schistosoma mansoni in recombinant Mycobacterium bovis Bacille Calmette-Guérin enhances protein expression but not protection against cercarial challenge in mice

A mycobacterial codon-optimized gene encoding the Sm14 antigen of Schistosoma mansoni was generated using oligonucleotide assembly. This synthetic gene enhanced approximately fourfold the protein expression level in recombinant Mycobacterium bovis Bacille Calmette-Guérin (rBCG) when compared to that obtained using the native gene in the same expression vector. Immunization of mice with rBCG expressing Sm14 via the synthetic gene induced specific cellular Th1-predominant immune responses, as determined by interferon-gamma production of Sm14-stimulated splenocytes, which were comparable to those recorded in animals immunized with an rBCG strain expressing the native gene. Administration of a single dose of the rBCG-Sm14 construct carrying the synthetic gene conferred protection against cercarial challenge in outbred Swiss mice, at a level equivalent to those provided by either a single dose of rBCG expressing the native gene or three doses of Escherichia coli-derived recombinant Sm14. Our data demonstrated that despite improving the level of antigen expression, the codon optimization strategy did not result in enhanced immunity or protection against cercarial S. mansoni challenge.

Intranasal delivery of vaccines against HIV

HIV poses a serious health threat in the world. Mucosal transmission of HIV through the genitourinary tract may be the most important route of transmission. Intranasal immunisations induce vaginal and systemic immune responses. Various protein-, DNA- and RNA-based immunopotentiating adjuvants/delivery systems and live bacterial and viral vectors are available for intranasal immunisations, and these systems may differ in their ability to induce a specific type of immune response (e.g., a cytotoxic T cell versus an antibody response). As the protection against HIV may require both cytotoxic T cell and antibodies, a combination of adjuvants/delivery systems for combinations of mucosal and parenteral immunisations may be required in order to develop a protective anti-HIV vaccine.

Intradermal and oral immunization with recombinant Mycobacterium bovis BCG expressing the simian immunodeficiency virus Gag protein induces long-lasting, antigen-specific immune responses in guinea pigs

To develop a new recombinant BCG (rBCG) vaccine, we constructed rBCG that expresses the full-length Gag protein of simian immunodeficiency virus (rBCG-SIVGag) at a level of 0.5 ng/mg after 3 weeks of bacterial cell culture. Intradermal (i.d.) inoculation of guinea pigs with 0.1 mg of rBCG-SIVGag resulted in the induction of delayed-type hypersensitivity (DTH) responses to both purified protein derivative (PPD) of tuberculin and SIV Gag p27 protein; responses that were maintained for the duration of the 50-week study. In contrast, guinea pigs orally vaccinated with 160 mg of the same antigen exhibited a long-lasting DTH response to the SIV Gag p27 protein, but mounted no response to PPD. Proliferative responses to SIV Gag p27 and PPD antigens were detected in both i.d. and orally immunized animals; however, the levels of PPD-specific responses were significantly higher in guinea pigs immunized by the i.d. than the oral route. A significant increase in the level of PPD- and SIV Gag p27-specific IFNgamma mRNA expression was also detected in both immunization groups receiving rBCG-SIVGag. In addition, both i.d. and oral immunization with rBCG-SIVGag induced PPD- and SIV Gag p27-specific serum IgG responses. Insertion of the SIV gag gene into BCG did not appear to change the ability of rBCG-immunized animals to elicit PPD-specific immune responses. These results indicate that rBCG-SIVGag has the ability to effectively induce long-lasting, cell-mediated and humoral immunity against both viral and bacterial antigens in guinea pigs, suggesting that rBCG-Gag has the potential to elicit immunities specific not only for tuberculosis but also for HIV at human doses.

Immunisation with recombinant BCG expressing the cottontail rabbit papillomavirus (CRPV) L1 gene provides protection from CRPV challenge

Recombinant Bacille Calmette-Guerin (rBCG) could potentially be the vaccine vehicle of choice to deliver foreign antigens from multiple pathogens. In this study we have used the cottontail rabbit papillomavirus (CRPV) rabbit model to provide a "proof of concept" that immunisation with rBCG expressing the CRPV major capsid protein, L1 (rBCG/CRPVL1), will protect outbred New Zealand White rabbits against CRPV challenge. Rabbits immunised with rBCG/CRPVL1 (10(7) cfu/ml) were protected 5 weeks post-CRPV challenge. Rabbits immunised with rBCG/CRPVL1 (10(5) cfu/ml) had papillomas, which were smaller and took longer to appear than the control rabbits. None of the negative control rabbits vaccinated with rBCG expressing an irrelevant gene or PBS were protected from CRPV challenge. Sera from rabbits immunised with rBCG/CRPVL1 (10(7) cfu/ml) were able to neutralise 54.5% of CRPV at serum dilutions of 1:200. These results provide evidence that BCG could potentially be used as a vaccine delivery vehicle for human papillomavirus proteins as a possible prophylactic vaccine.

Priming-boosting vaccination with recombinant Mycobacterium bovis bacillus Calmette-Guérin and a nonreplicating vaccinia virus recombinant leads to long-lasting and effective immunity

Virus-specific T-cell responses can limit immunodeficiency virus type 1 (HIV-1) transmission and prevent disease progression and so could serve as the basis for an affordable, safe, and effective vaccine in humans. To assess their potential for a vaccine, we used Mycobacterium bovis bacillus Calmette-Guérin (BCG)-Tokyo and a replication-deficient vaccinia virus strain (DIs) as vectors to express full-length gag from simian immunodeficiency viruses (SIVs) (rBCG-SIVgag and rDIsSIVgag). Cynomolgus macaques were vaccinated with either rBCG-SIVgag dermally as a single modality or in combination with rDIsSIVgag intravenously. When cynomologus macaques were primed with rBCG-SIVgag and then boosted with rDIsSIVgag, high levels of gamma interferon (IFN-gamma) spot-forming cells specific for SIV Gag were induced. This combination regimen elicited effective protective immunity against mucosal challenge with pathogenic simian-human immunodeficiency virus for the 1 year the macaques were under observation. Antigen-specific intracellular IFN-gamma activity was similarly induced in each of the macaques with the priming-boosting regimen. Other groups receiving the opposite combination or the single-modality vaccines were not effectively protected. These results suggest that a recombinant M. bovis BCG-based vector may have potential as an HIV/AIDS vaccine when administered in combination with a replication-deficient vaccinia virus DIs vector in a priming-boosting strategy.

Mycobacterial codon optimization enhances antigen expression and virus-specific immune responses in recombinant Mycobacterium bovis bacille Calmette-Guérin expressing human immunodeficiency virus type 1 Gag

Although its potential for vaccine development is already known, the introduction of recombinant human immunodeficiency virus (HIV) genes to Mycobacterium bovis bacille Calmette-Guérin (BCG) has thus far elicited only limited responses. In order to improve the expression levels, we optimized the codon usage of the HIV type 1 (HIV-1) p24 antigen gene of gag (p24 gag) and established a codon-optimized recombinant BCG (rBCG)-p24 Gag which expressed a 40-fold-higher level of p24 Gag than did that of nonoptimized rBCG-p24 Gag. Inoculation of mice with the codon-optimized rBCG-p24 Gag elicited effective immunity, as evidenced by virus-specific lymphocyte proliferation, gamma interferon ELISPOT cell induction, and antibody production. In contrast, inoculation of animals with the nonoptimized rBCG-p24 Gag induced only low levels of immune responses. Furthermore, a dose as small as 0.01 mg of the codon-optimized rBCG per animal proved capable of eliciting immune responses, suggesting that even low doses of a codon-optimized rBCG-based vaccine could effectively elicit HIV-1-specific immune responses.

Vaccination of rhesus macaques with recombinant Mycobacterium bovis bacillus Calmette-Guérin Env V3 elicits neutralizing antibody-mediated protection against simian-human immunodeficiency virus with a homologous but not a heterologous V3 motif

Although the correlates of vaccine-induced protection against human immunodeficiency virus type 1 (HIV-1) are not fully known, it is presumed that neutralizing antibodies (NAb) play a role in controlling virus infection. In this study, we examined immune responses elicited in rhesus macaques following vaccination with recombinant Mycobacterium bovis bacillus Calmette-Guérin expressing an HIV-1 Env V3 antigen (rBCG Env V3). We also determined the effect of vaccination on protection against challenge with either a simian-human immunodeficiency virus (SHIV-MN) or a highly pathogenic SHIV strain (SHIV-89.6PD). Immunization with rBCG Env V3 elicited significant levels of NAb for the 24 weeks tested that were predominantly HIV-1 type specific. Sera from the immunized macaques neutralized primary HIV-1 isolates in vitro, including HIV-1BZ167/X4, HIV-1SF2/X4, HIV-1CI2/X4, and, to a lesser extent, HIV-1MNp/X4, all of which contain a V3 sequence homologous to that of rBCG Env V3. In contrast, neutralization was not observed against HIV-1SF33/X4, which has a heterologous V3 sequence, nor was it found against primary HIV-1 R5 isolates from either clade A or B. Furthermore, the viral load in the vaccinated macaques was significantly reduced following low-dose challenge with SHIV-MN, and early plasma viremia was markedly decreased after high-dose SHIV-MN challenge. In contrast, replication of pathogenic SHIV-89.6PD was not affected by vaccination in any of the macaques. Thus, we have shown that immunization with an rBCG Env V3 vaccine elicits a strong, type-specific V3 NAb response in rhesus macaques. While this response was not sufficient to provide protection against a pathogenic SHIV challenge, it was able to significantly reduce the viral load in macaques following challenge with a nonpathogenic SHIV. These observations suggest that rBCG vectors have the potential to deliver an appropriate virus immunogen for desirable immune elicitations.

A call for replicating vector prime-protein boost strategies in HIV vaccine design

A key challenge to HIV vaccine development is the integration of HIV proviral DNA into the host genome upon infection. Therefore, an optimal vaccine should block infection within hours of viral exposure, providing 'sterilizing immunity' at mucosal sites and in blood via potent, broadly reactive antibody to the HIV envelope glycoprotein. This is difficult due to the envelope's conformational complexity and sequence diversity. Antibodies that do not completely prevent infection nevertheless could reduce the viral infectious burden, allowing strong cellular immunity to control viremia, delay disease progression and prevent viral transmission, while also providing help for T- and B-cell responses. Rapidly responsive, potent, persistent immunity might best be achieved using prime-boost strategies incorporating a replicating vector and an optimally designed envelope subunit.

Factors influencing the immune response to foreign antigen expressed in recombinant BCG vaccines

A wide range of recombinant BCG vaccine candidates containing foreign viral, bacterial, parasite or immunomodulatory genetic material have been developed and evaluated, primarily in animal models, for immune response to the foreign antigen. This review considers some of the factors that may influence the immunogenicity of these vaccines. The influence of levels and timing of expression of the foreign antigen and the use of targeting sequences are considered in the first section. Genetic and functional stability of rBCG is reviewed in the second section. In the last section, the influence of dose and route of immunization, strain of BCG and the animal model used are discussed.

Listeria monocytogenes-based antibiotic resistance gene-free antigen delivery system applicable to other bacterial vectors and DNA vaccines

Plasmids represent a powerful tool to rapidly introduce genes into bacteria and help them reach high expression levels. In vaccine development, with live vaccine vectors, this allows greater flexibility and the ability to induce larger antigen amounts through multiple gene copies. However, plasmid retention often requires antibiotic resistance markers, the presence of which has been discouraged in clinical applications by the Food and Drug Administration. Therefore, we developed a Listeria monocytogenes-Escherichia coli shuttle plasmid that is retained by complementation of D-alanine racemase-deficient mutant strains both in vitro and in vivo. Our technology potentially allows the production of antibiotic resistance marker-free DNA vaccines as well as bacterial vaccine vectors devoid of engineered antibiotic resistances. As a proof of concept, we applied the D-alanine racemase complementation system to our Listeria cancer vaccine platform. With a transplantable tumor model, we compared the efficacy of the new Listeria vector to that of an established vector containing a conventional plasmid carrying a tumor-specific antigen. Both vaccine vector systems resulted in long-term regression of established tumors, with no significant difference between them. Thus, the Listeria vaccine vector presented here potentially complies with Food and Drug Administration regulations and could be developed further for clinical use.

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Construction and characterization of bivalent vaccine candidate expressing HspA and Mr18000 OMP from Helicobacter pylori

AIM: To construct a recombinant vector which can express outer membrane protein (OMP) with M_r18000 and heat shock protein A (HspA) from Helicobacter pylori (H. pylori) in E. coli BL21, and to exploit the possibility for obtaining the vaccine conferring protection from H. pylori infection.

METHODS: The target gene of HspA was amplified from H. pylori chromosome by PCR, and then inserted into the prokaryotic expression vector pET32a (+) by restrictive endonuclease enzyme kpn I, BamH I simultaneously. The recombinant vector was used to sequence, and then together with pET32a (+)/Omp₁₈, digested by restrictive endonuclease enzyme Hind III and BamH I simultaneously. pET32a(+)/ HspA and Omp₁₈ were recovered from 1% agarose gel by gel kit, and ligated with T₄ ligase by BamH I digested viscidity end. The recombinant plasmid of pET32a(+)/HspA/Omp₁₈ was transformed and expressed in E. coli BL21 (DE3) under induction of IPTG. After purification, its antigenicity of the fusion protein was detected by Western blot.

RESULTS: Enzyme digestion analysis and sequencing showed that the target genes were inserted into the recombinant vector, composed of 891 base pairs, encoded objective polypeptides of 297 amino acid residues. Compared with GenBank reported by Tomb et al there were 1.3% and 1.4% differences in obtained H. pylori nucleotide sequence and amino acid residues, respectively. SDS-PAGE analysis showed that relative molecule mass (M_r) of the expressed product was M_r 51000, M_r of protein expressed by pET32a (+) was about M_r 20000, and soluble expression product accounted for 18.96% of total bacterial protein. After purification with Ni⁺²-NTA agarose resins, the purification of recombinant fusion protein was about 95%. Western blot showed that recombinant fusion protein could be recognized by the patients’ serum infected with H. pylori and anti-Omp₁₈ monoclone, suggesting that this protein had good antigenicity.

CONCLUSION: The gene coding for H. pylori M_r18000 OMP and HspA was cloned and expressed successfully. The results obtained lay the foundation for development of H. pylori protein vaccine and a quick diagnostic kit.