A truncated C-terminal fragment of Mycobacterium tuberculosis HSP70 gene enhanced potency of HBV DNA vaccine

DNA vaccine represents an attractive approach to therapy of chronic hepatitis B virus (HBV) infection because of its ability to generate antigen-specific immunity; nevertheless, there is still a need to increase the potency of DNA vaccine. Mycobacterium tuberculosis heat shock protein70 (HSP70) has both chaperon and cytokine functions, and has been shown to act as an adjuvant when co-administered with peptide antigens or given as fusion proteins. Here we evaluated the effects of two truncated HSP70 molecules, N-terminal domain (HSP70(1-360), amino acids 1-360) and C-terminal domain (HSP70(359-610), amino acids 359-610) of mycobacterial HSP70, on the potency of antigen-specific immunity generated by a HBV DNA vaccination. We found that only the HSP70(359-610)-fused HBV DNA vaccination resulted in a significant increase in hepatitis B surface antigen (HBsAg)-specific humoral response, while the HSP70(1-360)- or the complete HSP70 molecule-fused vaccine did not. Moreover, HSP70(359-610)-fused DNA vaccine did not induce anti-HSP70 antibody. Interestingly, HSP70(359-610) not only enhanced HBsAg-specific cytotoxic lymphocytes (CTL) responses but also overcame the epitope suppression caused by L(d)-restricted epitope. Meanwhile, HSP70(369-610) mediated T helper (Th) cell balance towards Th1 pathway. In a HBV transgenic mouse model, the HSP70(359-610) fusion vaccine facilitated clearance of circulating HBsAg and down-regulation of HBV replication. These results suggested that the truncated mycobacterial HSP70 molecule, HSP70(359-610), might be a superior candidate to deliver the adjuvant function in HBV DNA vaccination instead of the complete HSP70 molecule.     

酶联免疫斑点法检测乙型肝炎病毒感染者抗原表位特异性细胞毒性T淋巴细胞

目的 通过观察乙型肝炎病毒(HBV)特异性细胞毒性T细胞(CTL)抗原表位肽刺激外周血单个核细胞(PBMC)产生γ干扰素(IFN-γ)的能力,分析不同类型HBV感染人群特异性CTL免疫应答差异.方法 合成4条人类白细胞抗原(HLA)-A2限制性HBV特异性CTL抗原表位肽[分别为多聚酶P的575-583序列FLLSLGIHL(Tp),HBsAg28-39序列IPQSLDSWVCTSL(Tel),HBsAg183-191序列FLLTRILTI(Te2)和HBcAg18-27序列FLPSDFFPSV(Tc)].流式细胞术鉴定HLA基因表型.用合成的CTL表位肽分别刺激慢性乙型肝炎组(CHB)、慢性乙型重型肝炎组(CSH),既往HBV感染者(N1)组和健康献血员(N2)的PBMC,采用酶联免疫斑点法(ELISPOT)检测分泌IFN-γ的CTL细胞的频率.结果 (1)HLA-A2基因分布频率:44例CHB组为45.5%(20/44),18例CSH组为55.6%(10/18),10例N1组为60%(6/10),10例N2组全部选择以往研究已确定的HLA-A2阳性者.(2)ELISPOT检测结果:①4条HBV特异性抗原多肽反应阳性率在CHB组、CSH组、N1组和N2组分别为50%(10/20)、10%(1/10)、83.3%(5/6)和10%(1/10).N1组反应阳性率高于CSH组(X2=9.000,P=0.008)和N2组(X2=9.000,P=0.008).②各组对Tp、Te1、Te2和Tc四条肽的平均反应强度用斑点形成细胞(SFC)/106PBMC表示,采用非参数秩和检验,N1组对Tp、Te1、Te2和Tc肽的平均反应强度大于CSH组和N2组(分别为77 SFC/106PBMC vs 10 SFC/106PBMC vs 15 SFC/106PBMC,59 SFC/106PBMC vs 0 SFC/106PBMC vs 0 SFC/106PBMC,100 SFC/106PBMC vs 0 SFC/106PBMC vs 22 SFC/106 PBMC和57 SFC/106 PBMC vs 20 SFC/106 PBMC vs 30 SFC/106 PBMC,均P<0.01).结论 各种类型HBV感染者不论病毒清除与否,都可对HBV特异性多肽产生T细胞免疫反应,这种免疫反应以既往感染者最强,慢性乙型肝炎组较弱,慢性乙型重型肝炎组缺乏,提示HBV特异性CTL应答可能是自身免疫机制清除病毒的重要因素.     

The delivery of HBcAg via Tat-PTD enhances specific immune response and inhibits Hepatitis B virus replication in transgenic mice

Recent studies have indicated that the therapeutic vaccine based on enhancement of HBV-specific cytotoxic T-lymphocyte (CTL) activity may lead to viral clearance in chronically infected individuals. It is demonstrated that protein transduction domains (PTD) from HIV-1-Tat protein is able to enter cells when combined with exogenous antigens and induce specific CTL responses. We have previously testified that the expressed and purified fusion protein containing Tat-PTD47-57 and HBcAg could enter cytoplasm of dendritic cells, and enhance T cells response to generate HBcAg-specific CTLs efficiently in vitro. In the present study, we evaluated HBcAg-specific immune responses of PTD-HBcAg fusion protein in BALB/c mice and antiviral immunity in HBV transgenic mice. The studies showed that PTD-HBcAg not only induced significantly higher antibody responses, but also increased production of cytokine (IFN-γ, IL-2, IL-4 and IL-10) compared to HBcAg alone and PBS. Moreover, PTD-HBcAg fusion protein increased significantly the percentages of IFN-γ+CD8+ T cells and HBcAg-specific (CTL) responses. Also, enhancement of immune response induced by fusion protein reduced HBV DNA and HBsAg levels and decreased the expression of HBsAg in liver tissue of HBV transgenic mice. In conclusion, PTD-HBcAg fusion protein could enhance not only cell immune response but also humoral immune response, and induce robust specific CTL activity and therapeutic effects in HBV transgenic mice.     

Peptide based cytotoxic T-cell vaccines; delivery of multiple epitopes, help, memory and problems

Synthetic CD8+ cytotoxic T-lymphocyte (CTL) peptide epitope based vaccines are being developed against a number of human diseases. Here we describe extensive preclinical testing of peptide epitope vaccines formulated with a protein as a source of CD4 help and Montanide ISA 720, an adjuvant currently in human clinical trials. Such water-in-oil formulations could effectively co-deliver several peptide epitopes and simultaneously induce multiple independent CTL responses. The efficiency of CTL induction by some peptides was, however, dependent on the aqueous buffer conditions, with poor performance correlating with non-covalent peptide oligomerisation. Any of a number of proteins currently used in human vaccines could supply CD4 help and no difference in CTL induction was obtained if the CD4 response was amnestic or a primary. Peptide immunisation was found to induce long term CTL memory and the recall of protective responses did not depend on an amnestic CD4 response. Slow pyroglutamic acid formation and rapid oxidation of methionine residues was observed in water-in-oil formulations, however, the latter had no effect on CTL induction. These data highlight the need to monitor for potential deleterious chemical events and interpeptide interactions, but illustrate that peptide based vaccination can effectively deliver multiple epitopes, in conjunction with any protein, and induce protective memory.     

Unique immunogenicity of hepatitis B virus DNA vaccine presented by live-attenuated Salmonella typhimurium

A novel vaccine for hepatitis B virus (HBV) was designed by putting a naked DNA vaccine carrying hepatitis B surface antigen (HBsAg) into live-attenuated Salmonella typhimurium. Mucosal immunization by the oral route in mice showed significantly stronger cytotoxic T lymphocyte (CTL) response than recombinant HBsAg vaccination (P < 0.01 at an effector:target ratio of 100:1), while comparable to intramuscular naked DNA immunization at all effector:target ratios. Contrary to previous reports on naked DNA vaccines given intramuscularly, the IgG antibody response induced by the mucosal DNA vaccine is relatively weak when compared to recombinant HBsAg vaccine (P < 0.001 at day 21). These findings are supported by a high interferon-gamma but a low interleukin-4 level detected in the supernatant of splenic cell cultures obtained from mucosally immunized mice. As distinct to recombinant HBsAg vaccine which is effective for protection, oral mucosal DNA vaccine should be considered as a candidate for therapeutic immunization in chronic HBV infection, donor immunization before adoptive transfer of HBV-specific CTL to HBsAg positive bone marrow transplant recipients, and immunization of non-responders to recombinant HBsAg vaccine. This strongly cellular and relatively absent humoral response may make this vaccine a better candidate as a therapeutic vaccine for chronic HBV carriers than naked DNA vaccines, as the humoral response is relatively less important for the clearance of HBV from hepatocytes, but its presence may lead to side effects such as serum sickness and immune complex deposition in chronic HBV carriers.     

Dendritic cell KLH loading requirements for efficient CD4+ T-cell priming and help to peptide-specific cytotoxic T-cell response,in view of potential use in cancer vaccines

This study focuses on a Keyhole Limpet Hemocyanin (KLH) adjuvant strategy to augment efficacy of dendritic cell-based vaccines that use class I-restricted peptides. Requirements for loading dendritic cells (DC) with KLH were first determined in order to optimally prime CD4(+) T cells. These KLH-loaded cells were pulsed with antigenic peptide and cultured with T cells to induce a cytotoxic T lymphocyte (CTL) response against the peptide. Such a concomitant presentation of KLH and peptide by the same DC strongly augmented the peptide-specific CTL response, as compared to the response induced by DC pulsed with the peptide alone. This adjuvant effect was more pronounced for poorly immunogenic antigens. The use of optimised peptide and KLH-loaded DC may improve the efficacy of therapeutic anti-tumour peptide vaccination.     

乙型肝炎病毒特异性细胞毒T细胞实验研究技术进展

由于乙型肝炎病毒（HBV）感染中抗原特异性细胞毒T细胞（CTL）在病毒清除和肝细胞损害中的重要作用，使其成为研究热点之一。本文对HBV抗原特异性CTL的实验研究技术进展作一综述。涉及的实验方法包括^51Cr释放实验，乳酸脱氢酶释放法，有限稀释法，MHC—I类分子-肽四聚体，酶免疫斑点技术和流式细胞技术等。上述方法分别用于对HBV抗原特异性CTL表达频率，细胞毒功能，以及CTL表达与分泌细胞因子功能的测定。     

Mushroom lectin enhanced immunogenicity of HBV DNA vaccine in C57BL/6 and HBsAg-transgenic mice

DNA vaccination is a promising strategy for activating immune responses against hepatitis B virus (HBV) infection. However, the accumulated data have shown that DNA vaccination alone generates weak immune responses. To enhance the immunogenicity of HBV DNA vaccine, lectin purified from pleurotus ostreatus (POL) was used as adjuvant of HBV DNA vaccine for C57BL/6 and HBV surface antigen transgenic (HBVsAg-Tg) mice. Our data demonstrate that low dose of POL (1 μg/mouse) in conjunction with HBV DNA vaccine stimulated stronger HBV-specific delayed-type hypersensitivity (DTH) responses and higher HBV-specific IgG level than that in high dose of POL groups (5 μg/mouse and 10 μg/mouse). POL activated strong Th2 and Tc1 cell responses in immunized C57BL/6 and HBVsAg-Tg mice. POL as adjuvant of HBV DNA vaccine effectively enhanced HBV surface protein antibody (HBVsAb) and decreased HBVsAg level for HBV Tg mice treatment. Furthermore, POL infiltrated more lymphocytes excluding Th1, Th2 and Tc1 cell subtypes to liver of HBVsAg-Tg mice. Together, these results suggest that POL as adjuvant enhanced immunogenicity of HBV DNA vaccination and effectively stimulated immune reaponse for HBsAg-Tg mice treatment. Our findings implicate the potential of mushroom lectin as adjuvant of HBV DNA vaccine.     

Towards immunotherapy for chronic hepatitis B virus infections

Chronic liver disease and hepatocellular carcinoma associated with chronic hepatitis B virus (HBV) infection are among the most serious human health problems in highly endemic regions. Although, effective vaccines against HBV have been available for many years, over 350 million people still remain persistently infected with HBV. Current therapies fail to provide long-term control of viral replication in most patients. Viral persistence has been associated with a defect in the development of HBV-specific cell-mediated immunity. Vaccine-based strategies to boost or to broaden the weak virus-specific T cell response of patients with chronic hepatitis B are proposed as a means of terminating this persistent infection.     

Immune tolerance against HBV can be overcome in HBV transgenic mice by immunization with dendritic cells pulsed by HBVsvp

In chronic Hepatitis B Virus (HBV) infection the function of dendritic cells (DC), T- and B-cells is impaired. DC vaccination is an option to overcome this. DC pulsed in vitro with HBV sub viral particles (HBVsvp) and used to immunize mice can activate HBV directed humoral and cellular immune responses. In the present study we vaccinated HBV transgenic mice as a model for chronic HBV infection and observed humoral and cellular immune responses. In these mice, the lacking immune response against HBV is mainly due to peripheral tolerance. HBVsvp, together with LPS as a co-activating molecule, were used for pulsing and in vitro activation of DC. HBV transgenic mice were injected with pulsed DC two times. Four weeks after DC vaccination humoral and cellular immune responses, viral antigen levels and liver histology were analyzed. DC vaccinated HBV-transgenic mice developed a strong HBV specific antibody and T-cell response after DC vaccination. Neither circulating HBV antigen levels nor viremia, however, were controlled. No liver damage was observed. These results demonstrate that in vitro activation of DC and loading with HBVsvp can overcome tolerance against HBV and reactivate B- and T-cell responses in HBV transgenic mice, but were not sufficient to lead to virus control in these mice. Vaccination using DC, the key players of cellular and humoral immunity, after in vitro reactivation promises to break tolerance against HBV and may help patients with chronic hepatitis B to clear the infection.     

The role of cytotoxic T cells and cytokines in the control of hepatitis B virus infection

The aim of this study was to elucidate the molecular basis for viral clearance and liver disease in the pathogenesis of hepatitis B virus (HBV) infection. Using transgenic mice that replicate HBV at high levels in the liver as recipients of HBV-specific cytotoxic T cells (CTL), we have shown that the antiviral potential of the CTL is primarily mediated by noncytolytic mechanisms that involve the intra-hepatic production of IFN-gamma by these cells. We also showed that, following antigen recognition, HBV-specific CTL recruit antigen non-specific inflammatory cells that contribute to amplify the liver disease initiated by CTL. These results provided insight into immunological and virological processes that may lead to the development of new therapeutic strategies to terminate chronic HBV infection.     

A novel multivalent human CTL peptide construct elicits robust cellular immune responses in HLA-A*0201 transgenic mice: implications for HTLV-1 vaccine design

Cytotoxic T-lymphocytes are critical in the clearance of chronic viral infections such as HTLV-1. Peptide-based vaccines may have potential application in invoking antiviral CTL responses. In the development of vaccination strategies, it is becoming increasingly important to elicit a broad immune response against several epitopes simultaneously that may provide large population coverage. In the present study, we addressed this issue, namely the processing and presentation of multiple CTL epitopes simultaneously for the generation of multispecific CTL responses. We designed a novel multivalent peptide consisting of three HLA-A(*)0201 restricted CTL epitopes, with intervening double arginine residues in tandem. These epitopes were derived from the HTLV-1 regulatory protein Tax, which is an attractive target for vaccine development against HTLV-1. Arginine residues were included to provide cleavage sites for proteasomes, to generate the intended MHC Class I ligands. Proteasomal digestion studies and mass spectrometry analysis showed cleavage of the multivalent construct to generate the individual epitopes. Immunization of HLA-A(*)0201 transgenic mice with this construct efficiently elicited cellular responses to each intended epitope in vivo, further validating the applicability of this approach. These data may have potential in the development of immunotherapeutic strategies for the treatment of HTLV-1 disease and in the future design of multivalent subunit peptide vaccines.     

Immunogenicity of a hepatitis B DNA vaccine administered to chronic HBV carriers

Hepatitis B virus (HBV) is the major pathogen of chronic hepatitis and liver disease worldwide. Despite the availability of effective vaccines against hepatitis B for many years, over 370 million people remain persistently infected with HBV. Viral persistence is thought to be related to poor HBV-specific T-cell responses. Based on clinical data, the development of efficient methods capable of inducing strong T-cell responses is an important and primary step toward the development of immunotherapeutics against chronic HBV infection. We designed a phase I clinical trial in chronic HBV carriers to assess safety, tolerability and immunogenicity of a DNA vaccine expressing HBV small (S) and middle (preS2 +S) envelope proteins. After occurrence of lamivudine breakthrough, 10 HBeAg positive patients with chronic hepatitis B were followed longitudinally before, during and after DNA vaccine therapy. Immunizations were well tolerated and adverse physical events were mild and considered unrelated to the vaccine. Proliferative responses to hepatitis B surface antigen (HBsAg) were detected in two patients after DNA injections. Following three injections of vaccine, interferon (IFN)-gamma-producing T-cells specific for the preS2 or the S antigen were detectable in 50 and 100% of the patients, respectively. Each patient recognized at least one peptide within the envelope domain encoded by the vaccine. Anti-preS2 antibodies and seroconversion to anti-HBe were detected in two patients. This study shows evidences for the safety and immunological efficacy of HBV-DNA vaccination and demonstrates that DNA vaccination can restore or activate T-cell responses in chronic HBV carriers.     

A new approach for therapeutic vaccination against chronic HBV infections

There are currently about 257 million people suffering from chronic HBV infection worldwide. In many cases, an insufficient T cell response is causative for establishment of a chronic infection. To ensure a robust cellular immune response and induction of neutralizing antibodies a novel vaccine platform based on modified cell–permeable HBV capsids was utilized. Cell permeability was achieved by fusion of the membrane–permeable TLM-peptide to HBV core monomers, assembling the capsids. Insertion of a Strep-tagIII into the spike tip domain that protrudes from the capsid surface enables flexible loading with antigens that are fused to streptavidin. In this study, HBV surface antigen-derived PreS1PreS2 domain, fused to monomeric streptavidin, served as cargo antigen. Binding between antigen and capsids was characterized by surface plasmon resonance spectroscopy, electron microscopy and density gradient centrifugation. Confocal immunofluorescence microscopy and in vivo imaging of immunized mice demonstrated membrane permeability of cargo-loaded carriers and spread of antigen over the whole organism. Immunization experiments of mice revealed a robust induction of a specific cellular immune response, leading to destruction of HBV-positive cells and induction of HBV-specific neutralizing antibodies. Membrane permeability of these carriers allows needle-free application of antigen-loaded capsids as evidenced by induction of an HBV-specific CTL response and HBV-specific B cell response after oral or transdermal vaccination.These data indicate that cell–permeable antigen carriers, based on HBV capsids and loaded with HBV antigen, have the capacity to induce a cellular and a neutralizing humoral immune response. In addition, cell permeability of the vaccine platform enables antigen transfer across several cell layers, that could allow oral or transdermal immunization.     

Heat-shock protein 70 acts as an effective adjuvant in neonatal mice and confers protection against challenge with herpes simplex virus

Immunization of the neonate is a highly desirable goal for vaccine developers, since the neonate is profoundly susceptible to a number of viral and bacterial pathogens. The neonatal immune system tends to generate Th2 recall responses, known as neonatal tolerance, which may not protect against viral challenge later in life. In this study we demonstrate that a potent immune proinflammatory stimulator, heat-shock protein 70 (hsp70), can act as an effective and safe adjuvant in neonates. Priming of neonates with hsp70 coupled to a viral MHC Class I-restricted epitope (gB498-505) and injection with recombinant gB generated strong cytotoxic T lymphocyte (CTL) responses and a Th1 primary T helper cell response during the neonatal period. In addition, enhanced CTL and predominant Th1 recall responses to viral antigens were observed following secondary challenge as adults. These responses were sufficient to allow protection against a lethal challenge with Herpes Simplex Virus Type-1 (HSV-1). Therefore, hsp70 in conjunction with viral epitopes and recombinant viral protein can perhaps prime protective immune responses to herpes viruses early in life when infection, which can be life-threatening, and the establishment of latency frequently occur.     

Recombinant heat shock protein 65 carrying hepatitis B core antigen induces HBcAg-specific CTL response

Many studies have provided evidence that heat shock protein 65 (Hsp65) can elicit potent specific cellular adaptive immune responses (e.g. CD8(+) cytotoxic T-cell effectors or classic CTLs) based on their ability to chaperone antigenic peptides. Hsp65 is thus an effective carrier for heterologous peptide epitopes for therapeutic vaccines against cancer or chronic infectious diseases. The core antigen of hepatitis B virus (HBcAg) is extremely immunogenic, and functions as both a T-cell-dependent and a T-cell-independent antigen. Therefore, HBcAg may be a promising candidate target for therapeutic vaccine control of chronic HBV infection. Here, a chimeric protein, Hsp65Bc, was created by fusing the HBcAg sequence to the carboxyl terminus of the Hsp65 sequence in E. coli. Analysis of its antigenicity and immunogenicity revealed that HBc epitopes are surface accessible. Hsp65Bc induced moderate anti-HBc immune responses as well as a strong specific T-cell response in BALB/c mice. These results indicate that Hsp65Bc may have potential as a vaccine for treatment of HBV chronic infection.     

Synthetic nanoparticle vaccines produced by layer-by-layer assembly of artificial biofilms induce potent protective T-cell and antibody responses in vivo

Nanoparticle vaccines induce potent immune responses in the absence of conventional adjuvant due to the recognition by immune cells of the particle structures, which mimic natural pathogens such as viruses and bacteria. Nanoparticle vaccines were fabricated by constructing artificial biofilms using layer-by-layer (LbL) deposition of oppositely charged polypeptides and target designed peptides on CaCO₃ cores. LbL nanoparticles were efficiently internalized by dendritic cells in vitro by a mechanism that was at least partially phagocytic, and induced DC maturation without triggering secretion of inflammatory cytokines. LbL nanoparticle delivery of designed peptides to DC resulted in potent cross-presentation to CD8+ T-cells and more efficient presentation to CD4+ T-cells compared to presentation of soluble peptide. A single immunization of mice with LbL nanoparticles containing designed peptide induced vigorous T-cell responses characterized by a balanced effector (IFNγ) and Th2 (IL-4) ELISPOT profile and in vivo CTL activity. Mice immunized with LbL nanoparticles bearing ovalbumin-derived designed peptides were protected from challenge with Listeria monocytogenes ectopically expressing ovalbumin, confirming the relevance of the CTL/effector T-cell responses. LbL nanoparticles also elicited antibody responses to the target epitope but not to the matrix components of the nanoparticle, avoiding the vector or carrier affect that hampers utility of other vaccine platforms. The potency and efficacy of LbL nanoparticles administered in aqueous suspension without adjuvant or other formulation additive, and the absence of immune responses to the matrix components, suggest that this strategy may be useful in producing novel vaccines against multiple diseases.     

Recombinant heat shock protein 65 carrying PADRE and HBV epitopes activates dendritic cells and elicits HBV-specific CTL responses

BCG Hsp65 and PADRE have been shown to be potent to enhance antigen specific immunity. In order to explore the possibility to utilize them for the development of HBV therapeutic vaccine, a chimeric protein, Hsp65-HBV, was created by fusing PADRE and epitopes from HBV to the carboxyl-terminus of BCG Hsp65 and expressed in E. coli. We evaluated its effects on human dendritic cell maturation and specific CTL induction in vitro. Results showed that Hsp65-HBV could activate human dendritic cells by up-regulating the expressions of HLA-A2, HLA-DR and CD86, companioning with high level of IL-12 secretion. Furthermore, Hsp65-HBV matured DCs could significantly stimulate human autologous CD8⁺ T cell proliferation and induce HBV-specific CTLs. Hsp65-HBV was also shown to generate HBsAg-specific CTLs in vivo in mice. These results indicated that Hsp65-HBV might be a candidate for the treatment of chronic HBV infection.     

Levamisole is a potential facilitator for the activation of Th1 responses of the subunit HBV vaccination

Chemical compounds activating innate responses may present potential adjuvants for the vaccine development. Levamisole (LMS), demonstrated as a potent adjuvant for DNA and viral killed vaccines in our previous studies, may activate such responses. To confirm this notion, LMS combined with the recombinant HBsAg (rHBsAg) was investigated. Compared to the vaccination with rHBsAg alone, LMS could up-regulate the expressions of TLR7&8, MyD88, IRF7 and their downstream pro-inflammatory cytokines including IFN-α and TNF-α, which promote DCs activation. Strikingly, we find that the combination of LMS and alum adjuvant synergistically enhances immunogenicity of rHBsAg and leads to a robust cell-mediated response demonstrated by the higher level of IgG2a/IgG1, T cell proliferation, and importantly, a high level of antigen-specific CTL and IFN-γ production within these activated CD8⁺ T cells. The achieved robust responses are at a comparative level with CpG + alum used as a positive control adjuvant in mice. The combination of LMS + alum with rHBsAg may provide a cost-effective, safe, and effective therapy to treat those individuals chronically infected by HBV, since antigen-specific cellular immunity is implicated for the clearance of HBV chronic infection.     

Immunization with a LEAPS heteroconjugate containing a CTL epitope and a peptide from beta-2-microglobulin elicits a protective and DTH response to herpes simplex virus type 1

A ligand epitope antigen presentation system (LEAPS) heteroconjugate vaccine containing a CTL epitope (H1) from the HSV-1 immediate early protein ICP27 (322-332) and a peptide sequence (J) from beta-2-microglobulin (35-50) elicited protection from intraperitoneal viral challenge and promoted DTH responses. The H1 peptide and other H1 containing heteroconjugates did not elicit protection or DTH responses. Antibody to the H1 peptide could not be detected by ELISA following vaccination with peptide, heteroconjugate or natural infection. The LEAPS heteroconjugate appears to prime a Thl-like response which is subsequently boosted by infection. These studies show that attachment of the J peptide can make a CTL epitope into a vaccine which is immunogenic and promotes a protective Th1 type of response.