HBV DNA vaccine with adjuvant cytokines induced specific immune responses against HBV infection

Coinfection of Clonorchis sinensis and hepatitis B virus: clinical liver indices and interaction in hepatic cell models

BACKGROUND

In China, people infected with hepatitis B virus (HBV) are commonly found in areas with a high prevalence of Clonorchis sinensis, a trematode worm. Published studies have reported that the progression of hepatitis B is affected by coinfection C. sinensis.

METHODS

Clinical data from a total of 72 patients with C. sinensis and HBV (as sole infection or with coinfections) and 29 healthy individuals were analysed. We also incubated the hepatic stellate cell line LX-2 with total proteins from C. sinensis adult worms (CsTPs) and HBV-positive sera. In addition, the human hepatoblastoma cell line HepG2.2.15 was treated with the antiviral drug entecavir (ETV), CsTPs and the anti-C. sinensis drug praziquantel (PZQ).

RESULTS

Our clinical data indicated that the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TB) and hyaluronic acid (HA) were significantly higher in patients with coinfection than in those infected with HBV only. In cell models, compared with the model in which LX-2 cells were incubated with HBV-positive sera (HBV group), transcripts of alpha-smooth muscle actin and types I and III collagen were significantly elevated in the models of LX-2 cells treated with CsTPs and HBV-positive sera (CsTP+HBV group), while the messenger RNA levels of tumour necrosis factor-α, interleukin (IL)-1β and IL-6 in the CsTP+HBV group were clearly lower. The HBV surface antigen and hepatitis B e-antigen levels were higher in the HepG2.2.15 cells treated with ETV and CsTPs than in those in the ETV group and in the cells administered a mixture of ETV, CsTPs and PZQ.

CONCLUSIONS

These results confirmed that C. sinensis and HBV coinfection could aggravate the progression of liver fibrosis. CsTPs might promote chronic inflammation of the liver in individuals with HBV infection, resulting in the development of hepatic fibrosis.

Cytokines and Chemokines in HBV Infection

Chronic hepatitis B virus (HBV) infection remains a leading cause of hepatic inflammation and damage. The pathogenesis of chronic hepatitis B (CHB) infection is predominantly mediated by persistent intrahepatic immunopathology. With the characterization of unique anatomical and immunological structure, the liver is also deemed an immunological organ, which gives rise to massive cytokines and chemokines under pathogenesis conditions, having significant implications for the progression of HBV infection. The intrahepatic innate immune system is responsible for the formidable source of cytokines and chemokines, with the latter also derived from hepatic parenchymal cells. In addition, systemic cytokines and chemokines are disturbed along with the disease course. Since HBV is a stealth virus, persistent exposure to HBV-related antigens confers to immune exhaustion, whereby regulatory cells are recruited by intrahepatic chemokines and cytokines, including interleukin-10 and transforming growth factor β, are involved in such series of causal events. Although the considerable value of two types of available approved treatment, interferons and nucleos(t)ide analogues, effectively suppress HBV replication, neither of them is sufficient for optimal restoration of the immunological attrition state to win the battle of the functional or virological cure of CHB infection. Notably, cytokines and chemokines play a crucial role in regulating the immune response. They exert effects by directly acting on HBV or indirectly manipulating target immune cells. As such, specific cytokines and chemokines, with a potential possibility to serve as novel immunological interventions, combined with those that target the virus itself, seem to be promising prospects in curative CHB infection. Here, we systematically review the recent literature that elucidates cytokine and chemokine-mediated pathogenesis and immune exhaustion of HBV infection and their dynamics triggered by current mainstream anti-HBV therapy. The predictive value of disease progression or control and the immunotherapies target of specific major cytokines and chemokines in CHB infection will also be delineated.

IL-12 DNA Displays Efficient Adjuvant Effects Improving Immunogenicity of Ag85A in DNA Prime/MVA Boost Immunizations

Mycobacterium tuberculosis (Mtb) infection is one of the leading causes of death worldwide. The Modified Vaccinia Ankara (MVA) vaccine vector expressing the mycobacterial antigen 85A (MVA85A) was demonstrated to be safe, although it did not improve BCG efficacy, denoting the need to search for improved tuberculosis vaccines. In this work, we investigated the effect of IL-12 DNA -as an adjuvant- on an Ag85A DNA prime/MVA85A boost vaccination regimen. We evaluated the immune response profile elicited in mice and the protection conferred against intratracheal Mtb H37Rv challenge. We observed that the immunization scheme including DNA-A85A+DNA-IL-12/MVA85A induced a strong IFN-γ production to Ag85A in vitro, with a significant expansion of IFN-γ⁺CD4⁺ and IFN-γ⁺CD8⁺ anti-Ag85A lymphocytes. Furthermore, we also detected a significant increase in the proportion of specific CD8⁺CD107⁺ T cells against Ag85A. Additionally, inclusion of IL-12 DNA in the DNA-A85A/MVA85A vaccine scheme induced a marked augment in anti-Ag85A IgG levels. Interestingly, after 30 days of infection with Mtb H37Rv, DNA-A85A+DNA-IL-12/MVA85A vaccinated mice displayed a significant reduction in lung bacterial burden. Together, our findings suggest that IL-12 DNA might be useful as a molecular adjuvant in an Ag85A DNA/MVA prime-boost vaccine against Mtb infection.

Serum HBeAg and HBV DNA levels are not always proportional and only high levels of HBeAg most likely correlate with high levels of HBV DNA: A community-based study

This study aimed to investigate the correlation between quantitative hepatitis B e antigen (HBeAg) and hepatitis B virus (HBV) DNA levels, and to determine whether semiquantitative measurement of HBeAg can indicate the extent of HBV replication in HBeAg-positive subjects in the immune tolerant phase.A cross-sectional, community-based survey was carried out in 12 communities of 2 counties in Zhejiang Province, China. A panel of 788 HBeAg-positive subjects was divided into 4 groups according to HBV DNA level.Groups I (n = 111), II (n = 91), III (n = 124), and IV (n = 462) had HBV DNA levels below 10 copies/mL (PCR undetectable), between 10 and 10 copies/mL (PCR detectable), between 10 and 2 × 10 copies/mL (hybridization detectable), and >2 × 10 copies/mL, respectively. The HBeAg level correlated well with the HBV DNA level (R = 0.658; P < .01) on a log scale. The average HBeAg level in group IV was significantly higher than those in the other 3 groups, and the best HBeAg cut-off value for differentiating group IV from the other 3 groups was 768 S/CO, with a sensitivity of 94.4% and specificity of 91.1%.Semiquantification of HBeAg could indicate a relative HBV DNA level in HBeAg-positive subjects in the immune tolerant phase.

Association of the interleukin-12 polymorphic variants with the development of antibodies to surface antigen of hepatitis B virus in hemodialysis patients in response to vaccination or infection

Cytokines, involved in the T-helper 1 system, play a role in the regulation of hepatitis B virus (HBV) clearance and the immune response to HBV antigens during natural infection or planned vaccination. Our aim was to examine whether the polymorphic variants of IL-12 are equally associated with development of antibodies to HBV surface antigen (anti-HBs) in hemodialysis (HD) patients in the case of HBV vaccination or HBV infection. The IL-12A rs568408 and IL-12B rs3212227 polymorphisms were analyzed in relation to anti-HBs development in 602 HD patients with negative antibodies to HBV core antigen (anti-HBc) who were hepatitis B vaccinated (group I) as well as in 237 anti-HBc positive HD patients who were infected with HBV in the past (group II). In group I, 199 patients did not develop an anti-HBs titre >10 IU/L (subgroup Ia), whereas in group II, 55 patients did not develop an anti-HBs titre >10 IU/L (subgroup IIa). Patients of groups I and II that developed an anti-HBs >10 IU/L were included into subgroups Ib and IIb, respectively. In hepatitis B vaccinated HD patients, development of a protective anti-HBs titre was positively associated with vintage of renal replacement therapy (RRT), chronic glomerulonephritis as a cause of RRT, and GA rs 568408 IL-12A (OR 1.6, 95 % CI 1.0-2.5, P = 0.035), but a frequency distribution of this genotype between responders and non-responders was not significant when the Bonferroni correction was applied. In HBV infected HD patients, anti-HBs development was positively associated with AC rs3212227 IL-12B (OR 8.0, 95 % CI 2.6-24.9, P < 0.001), whereas HBsAg positivity, AA rs3212227 IL-12B (OR 0.3, 95 % CI 0.1-0.7, P = 0.007), and CC rs3212227 IL-12B (OR 0.1, 95 % CI 0.03-0.6, P = 0.011) were negative predictors of positive anti-HBs phenotype. When the Bonferroni correction was applied, if appropriate, these associations remained significant. In HD patients, the studied IL-12 polymorphic variants seem to be associated with the anti-HBs phenotype (a) with borderline significance for IL-12A in hepatitis B vaccinated patients, and (b) significantly for IL-12B in patients who underwent natural HBV infection.

Antibodies to hepatitis B virus surface antigen and interleukin 12 and interleukin 18 gene polymorphisms in hemodialysis patients

BACKGROUND

The interleukin (IL)18 rs360719 CC genotype is associated with the development of antibodies to hepatitis B virus surface antigen (anti-HBs) in hemodialysis (HD) patients. IL18 shares biological properties with IL12 in promoting the T-hepler 1 (Th1) system. We studied whether polymorphisms in the IL12A 3` untranslated region (UTR) and IL12B 3`UTR may contribute to anti-HBs development (titre ≥ 10 IU/L) in HD patients either individually or jointly with the IL18 polymorphism.

METHODS

In 518 HD patients and 240 controls the IL12A rs568408 3'UTR G > A polymorphism was genotyped by high-resolution melting curve analysis. Polymerase chain reaction restriction fragment length polymorphism was used to detect the IL12B rs3212227 3'UTR A > C and IL18 -1297 T > C rs360719 polymorphisms. The associations between the IL12A, IL12B and IL18 genotypes and the risk of impaired anti-HBs development were estimated by computing the odds ratios and their 95% confidence intervals using logistic regression analysis.

RESULTS

In the logistic regression analysis, the higher frequency of rs360719 CC individually (2.9% in 207 patients without anti-HBs development vs 8.0% in 311 patients with anti-HBs development, p = 0.009) and of rs360719 CC combined with rs568408 GG (p = 0.048), rs568408 GA (p = 0.035), rs568408 GG/AA (p = 0.034) or rs3212227 AA (p = 0.046) was associated with an increased chance for the development of anti-HBs in HD patients. Patients bearing both rs568408 AA and rs360719 TT had a 10.9-fold or 8.9-fold lower chance, respectively, to develop anti-HBs compared with those carrying any other genotype (p = 0.005) or those who had both wild-type rs568408 GG and rs360719 TT (p = 0.011). Carriers of both rs3212227 CC and rs360719 TC had a 4.6-fold lower chance for anti-HBs development than carriers of any other genotype (p = 0.042).

CONCLUSION

Development of anti-HBs in HD patients is associated with gene polymorphisms of interleukins involved in the Th1 system.

Genetic immunization with Hantavirus vaccine combining expression of G2 glycoprotein and fused interleukin-2

In this research, we developed a novel chimeric HTNV-IL-2-G2 DNA vaccine plasmid by genetically linking IL-2 gene to the G2 segment DNA and tested whether it could be a candidate vaccine. Chimeric gene was first expressed in eukaryotic expression system pcDNA3.1 (+). The HTNV-IL-2-G2 expressed a 72 kDa fusion protein in COS-7 cells. Meanwhile, the fusion protein kept the activity of its parental proteins. Furthermore, BALB/c mice were vaccinated by the chimeric gene. ELISA, cell microculture neutralization test in vitro were used to detect the humoral immune response in immunized BALB/c mice. Lymphocyte proliferation assay was used to detect the cellular immune response.- The results showed that the chimeric gene could simultaneously evoke specific antibody against G2 glycoprotein and IL-2. And the immunized mice of every group elicited neutralizing antibodies with different titers. Lymphocyte proliferation assay results showed that the stimulation indexes of splenocytes of chimeric gene to G2 and IL-2 were significantly higher than that of other groups. Our results suggest that IL-2-based HTNV G2 DNA can induce both humoral and cellular immune response specific for HTNV G2 and can be a candidate DNA vaccine for HTNV infection.

Therapeutic vaccination with simian immunodeficiency virus (SIV)-DNA + IL-12 or IL-15 induces distinct CD8 memory subsets in SIV-infected macaques

DNA vaccination is an invaluable approach for immune therapy in that it lacks vector interference and thus permits repeated vaccination boosts. However, by themselves, DNA-based vaccines are typically poor inducers of Ag-specific immunity in humans and non-human primates. Cytokines, such as IL-12 and IL-15, have been shown to be potent adjuvants for the induction and maintenance of cellular immune responses, in particular during HIV infection. In this study, we examined the ability of therapeutic vaccination with SIV-DNA+IL-12 or IL-15 as molecular adjuvants to improve DNA vaccine potency and to enhance memory immune responses in SIV-infected macaques. Our results demonstrate that incorporating IL-12 into the vaccine induces SIV-specific CD8 effector memory T cell (T(EM)) functional responses and enhances the capacity of IFN-gamma-producing CD8 T(EM) cells to produce TNF. Lower levels of PD-1 were expressed on T cells acquiring dual function upon vaccination as compared with mono-functional CD8 T(EM) cells. Finally, a boost with SIV-DNA+IL-15 triggered most T cell memory subsets in macaques primed with either DNA-SIV or placebo but only CD8 T(EM) in macaques primed with SIV-DNA+IL-12. These results indicate that plasmid IL-12 and IL-15 cytokines represent a significant addition to enhance the ability of therapeutic DNA vaccines to induce better immunity.

Engineering enhancement of the immune response to HBV DNA vaccine in mice by the use of LIGHT gene adjuvant

DNA vaccines could induce protective immune responses in several animal models. Many strategies have been employed to improve the effect of nucleic acid vaccines. LIGHT is a member of the TNF superfamily and functions as a co-stimulatory molecule for T cell proliferation. In the study, the immunogenicity in the induction of humoral and cellular immune responses by HBV DNA vaccine and the adjuvant effect of LIGHT were studied in a murine model. The eukaryotic expression plasmid pcDNA-L was constructed by inserting mouse LIGHT gene into the vector pcDNA3.1(+). In vitro expression of LIGHT was detected by RT-PCR and indirect immunofluorescence assay in transfected HeLa cells. MLR assay showed that LIGHT-transfected DCs induced markedly higher allogeneic lymphocyte proliferation than pcDNA-transfected DCs and untreated DCs at all dilutions. After BALB/c mice were immunized by three intramuscular injections of the HBV DNA vaccine plasmids alone or in combination with LIGHT expression plasmids, the different levels of anti-HBV immune responses were measured comparable to the control groups immunized with parent plasmid pcDNA or PBS. The HBsAg-specific splenocytes proliferation and specific cytotoxic activities of splenic CTLs in the coinoculation group were both significantly higher than those in the HBV DNA single inoculation group, and an enhancement of antibody response was also observed in the coinoculation group compared with the single inoculation group. Taken together, coimmunization of HBV DNA vaccine plasmids and LIGHT expression plasmids can elicit stronger humoral and cellular immune responses in mice than HBV DNA vaccine plasmids alone, and LIGHT may be an effective immunological adjuvant in HBV DNA vaccination.

Granulocyte-macrophage colony-stimulating factor DNA prime-protein boost strategy to enhance efficacy of a recombinant pertussis DNA vaccine

AIM

To investigate a new strategy to enhance the efficacy of a recombinant pertussis DNA vaccine. The strategy is co-injection with cytokine plasmids as prime, and boosted with purified homologous proteins.

METHOD

A recombinant pertussis DNA vaccine containing the pertussis toxin subunit 1 (PTS1), fragments of the filamentous hemagglutinin (FHA) gene and pertactin (PRN) gene encoding filamentous hemagglutinin and pertactin were constructed. Balb/c mice were immunized with several DNA vaccines and antigen-specific antibodies anti-PTS1,anti-PRN, anti-FHA,cytokines interleukin (IL)-10, IL-4, IFN-gamma,TNF-alpha,and splenocyte-proliferation assay were used to describe immune responses.

RESULTS

The recombinant DNA vaccine could elicit similar immune responses in mice as that of separate plasmids encoding the 3 fragments, respectively. Mice immunized with DNA and boosted with the corresponding protein elicited more antibodies than those that received DNA as boost. In particular, when the mice were co-immunized with murine granulocyte-macrophage colony-stimulating factor plasmids and boosted with proteins, all 4 cytokines and the 3 antigen-specific antibodies were significantly increased compared to the pVAX1 group. Anti-PTS1, anti- FHA, IL-4 and TNF-alpha elicited in the colony stimulating factor (CSF) prime-protein boost group showed significant increase compared to all the other groups.

CONCLUSION

This prime and boost strategy has proven to be very useful in improving the immunogenicity of DNA vaccines against pertussis.

Anti-HBV immune responses in rhesus macaques elicited by electroporation mediated DNA vaccination

Electroporation has been shown to be an effective method to improve the efficiency of gene expression and the immunogenicity of DNA vaccines. In order to optimize the procedure and test for its efficacy in more clinically relevant large animal models, we examined the detailed immune responses in rhesus macaques after vaccination intramuscularly with electroporation using the plasmid encoding for HBV preS(2)-S antigen and an adjuvant plasmid encoding for hIL-2 and hIFN-gamma. Several important factors were examined, including the dose response relationships, the effect of various prime and boost regimens, and different combinations of electro-pulse parameters. The immune responses were closely followed for more than a year. The results showed that in rhesus macaques, electroporation can significantly enhance the immunogenicity of the DNA vaccines, resulting in greatly improved antibody responses as well as peptide-stimulated IFN-gamma producing T cell responses. In addition, we also reported the different antibody response behaviors resulted from different electro-pulse parameters. The detailed data would be useful to suggest possible optimization strategies for better DNA vaccine efficacy.

Evaluation of Brucella abortus DNA vaccine by expression of Cu–Zn superoxide dismutase antigen fused to IL-2

The Cu-Zn superoxide dismutase (SOD) antigen of Brucella abortus was previously identified to be a T cell antigen which induces both proliferation of and gamma interferon (IFN-gamma) secretion by T cells from infected mice. In an earlier study, we demonstrated that intramuscular injection of mice with a plasmid DNA carrying the gene for SOD leads to the development of significant protection against B. abortus challenge. It has been reported that the antigen-specific immune responses generated by a DNA vaccine can be enhanced by co-delivery of certain cytokine genes. In this study, we evaluated the effect of delivering IL-2 on the efficacy of SOD DNA vaccine by generating a plasmid (pSecTag-SOD-IL2) that codes for a secretory fusion protein of SOD and IL-2. Another plasmid (pSecTag-SOD) that codes for only SOD as a secretory protein was used for comparison. BALB/c mice injected intramuscularly with pSecTag-SOD or pSecTag-SOD-IL2, but not the control plasmid pSecTag, developed SOD-specific antibody and T cell immune responses. Upon in vitro stimulation with recombinant SOD (rSOD) antigen, T cells from mice immunized with pSecTag-SOD-IL2, in comparison with those from mice immunized with pSecTag-SOD, exhibited a lower proliferation response but produced significantly higher concentrations of IFN-gamma. Both DNA vaccines, however, induced similar levels of SOD-specific antibodies and cytotoxic T cell response. Although mice immunized with pSecTag-SOD-IL2 showed increased resistance to challenge with B. abortus virulent strain 2308, this increase was not statistically significant from that of pSecTag-SOD vaccinated mice. These results suggest that a SOD DNA vaccine fused to IL2 did not improve protection efficacy.

SIV DNA vaccine co-administered with IL-12 expression plasmid enhances CD8 SIV cellular immune responses in cynomolgus macaques

Current evidence suggests that a strong induced CD8 human immunodeficiency virus type 1 (HIV-1)-specific cell mediated immune response may be an important aspect of an HIV vaccine. The response rates and the magnitude of the CTL responses induced by current DNA vaccines in humans need to be improved and cellular immune responses to DNA vaccines can be enhanced in mice by co-delivering DNA plasmids expressing immune modulators. Two reported to work well in the mouse systems are interleukin (IL)-12 and CD40L. We sought to compare these molecular adjuvants in a primate model system. The cDNA for macaque IL-12 and CD40L were cloned into DNA vectors. Groups of cynomolgus macaques were immunized with 2 mg of plasmid expressing SIVgag alone or in combination with either IL-12 or CD40L. CD40L did not appear to enhance the cellular immune response to SIVgag antigen. However, more robust results were observed in animals co-injected with the IL-12 molecular adjuvant. The IL-12 expanded antigen-specific IFN-gamma positive effector cells as well as granzyme B production. The vaccine immune responses contained both a CD8 component as well a CD4 component. The adjuvanted DNA vaccines illustrate that IL-12 enhances a CD8 vaccine immune response, however, different cellular profiles.

Adjuvant Action of MurineIL-2/IgPlasmid After Intramuscular Immunization With Indian HIV-1 Subtype C Recombinantenv.gp120 Construct

The human immunodeficiency virus (HIV) epidemic is probably the greatest scourge to affect mankind in the 20th century. Containment of the acquired immunodeficiency syndrome (AIDS) epidemic will require an effective vaccine. Of various vaccine approaches, immunization with DNA plasmids containing HIV-1 structural genes is the most popular approach. However, an important limitation of DNA immunization is that these responses are relatively weak and are often only transient in their nature. The use of immunologic adjuvants together with DNA vaccines is a promising way to enhance and to optimize DNA-derived immunity. Cytokines have been widely used to enhance the immune responses of DNA vaccines. In the present investigation, we studied the in vivo immunomodulation of HIV-1 Indian subtype C plasmid construct (pJWSK3, encoding envgp120 gene) by plasmid-based murine IL-2/Ig construct. Subcloning of mIL-2/Ig gene from pVRCmIL-2/Ig construct into pJW4304 vector was done followed by its in vitro expression study on the COS-7 cell line. Co-immunization of the recombinant HIV-1 env-gp120 construct with the IL-2/Ig construct in the female Balb/c mice by the intramuscular route resulted in induction of significantly higher levels of both HIV-1-specific antibody response and cell mediated immune response than by DNA plasmid construct alone (p < 0.001 and p < 0.05, respectively). The induced HIV-1-specific murine IFN-gamma response was robust, broad based, and seen even at the end of 6 months after immunization. Taken together these results indicate that the strategy of using IL-2/Ig plasmid can be highly effective when used along with recombinant DNA constructs and serve as the potential tool for the development of more rationally designed vaccines against HIV-1.

Current developments in viral DNA vaccines: shall they solve the unsolved?

This review describes the mechanisms of immune response following DNA vaccination. The efficacy of DNA vaccines in animal models is highlighted, especially in viral diseases against which no widely accepted vaccination is currently available. Emphasis is given to possible therapeutic vaccination in chronic infections due to persisting virus genomes, such as recurrent herpes (HSV-1 and HSV-2), pre-AIDS (HIV-1) and/or chronic hepatitis B (HBV). In these, the problem of introducing foreign viral DNA may not be of crucial importance, since the immunised subject is already a viral DNA (or provirus) carrier. The DNA-based immunisation strategies may overcome several problems of classical viral vaccines. Novel DNA vaccines could induce immunity against multiple viral epitopes including the conservative type common ones, which do not undergo antigenic drifts. Within the immunised host, they mimic the effect of live attenuated viral vaccines when continuously expressing the polypeptide in question. For this reason they directly stimulate the antigen-presenting cells, especially dendritic cells. The antigen encoded by plasmid elicits T helper cell activity (Th1 and Th2 type responses), primes the cytotoxic T cell memory and may induce a satisfactory humoral response. The efficacy of DNA vaccines can be improved by adding plasmids encoding immunomodulatory cytokines and/or their co-receptors.

A combined nucleocapsid vaccine induces vigorous SARS-CD8+ T-cell immune responses

Several studies have shown that cell-mediated immune responses play a crucial role in controlling viral replication. As such, a candidate SARS vaccine should elicit broad CD8+ T-cell immune responses. Several groups of mice were immunized alone or in combination with SARS-nucleocapsid immunogen. A high level of specific SARS-CD8+ T-cell response was demonstrated in mice that received DNA encoding the SARS-nucleocapsid, protein and XIAP as an adjuvant. We also observed that co-administration of a plasmid expressing nucleocapsid, recombinant protein and montanide/CpG induces high antibody titers in immunized mice. Moreover, this vaccine approach merits further investigation as a potential candidate vaccine against SARS.

Enhanced mucosal and systemic immunogenicity of human papillomavirus-like particles encapsidating interleukin-2 gene adjuvant

Here, we report the enhanced mucosal and systemic immunogenicity of human papillomavirus type (HPV) 16 L1 virus-like particles (VLP) encapsidating a cytokine genetic adjuvant. Plasmid DNA expressing interleukin-2 (pIL2) was encapsidated in VLP using the reassembly property of VLP from disassembled L1 capsomeres. pIL2 in reassembled VLP showed stability against DNase I, indicating encapsidation. After intramuscular immunization into mice, the highest vaginal and salivary HPV16 L1-specific IgA titers were observed in pIL2-encapsidated VLP, followed by VLP plus pIL2 in separate plasmid, and VLP alone. Similar to mucosal responses, serum IgG, IgG1, and IgG2a antibody titers were the highest in the group treated with pIL2-encapsidated VLP. Moreover, the adjuvanticity of pIL2 encapsidated in VLP was stronger in IgG2a antibody relative to IgG1 antibody. Our results indicate that the encapsidation of a genetic cytokine adjuvant pIL2 would be beneficial for more effective induction of mucosal and systemic immune responses to VLP vaccines.

Resiquimod is a modest adjuvant for HIV-1 gag-based genetic immunization in a mouse model

DNA vaccines have been effective at generating useful immune responses in many animal species. However, it is clearly desirable to increase their potency. The identification of adjuvants that increase their cell-mediated immune (CMI) response is therefore an important goal. Resiquimod is an imiquimod analog proven to activate dendritic cells through TLR-7. The adjuvant capacity of resiquimod has not, to our knowledge, been studied in the context of genetic immunization. Here, we studied resiquimod as an adjuvant for plasmid vaccine therapy by intra-muscular immunization of BALB/c mice with HIV-1 gag DNA vaccine without and with several concentrations of resiquimod (ranging from 5-100nM). We observed that resiquimod moderately enhanced IFN-gamma production as measured by a peptide-based ELISPOT assay compared to that obtained in mice immunized with DNA gag only. Antigen-specific T-cell proliferation studies showed a several-fold increase in the stimulation index in mice immunized with DNA gag +50 nM of resiquimod as compared to mice receiving DNA gag alone. Antibody titer also increased, while the antibody isotyping data showed a strong Th1 biased type response. Analysis of cytokine production in serum samples demonstrated a stronger Th1 cytokine bias in the presence of resiquimod. Furthermore, relevant increase in IL-4 production, as measured by ELISPOT assay, was not observed. Our results show that resiquimod can have modest adjuvant activity, in a DNA formulation, driving the immune system towards a cell-mediated immune response. Additional studies involving this adjuvant for DNA vaccines are underway.

HLA and cytokine gene polymorphisms are independently associated with responses to hepatitis B vaccination

Variable immune responses to hepatitis B virus (HBV) infection and recombinant HBV vaccines have been associated with polymorphisms in several genes within the human leukocyte antigen (HLA) complex. Analyses of polymerase chain reaction (PCR)-based genotyping data from 164 North American adolescents vaccinated with recombinant HBV products confirmed that HLA-DRB1*07 (relative odds [RO] = 5.18, P <.0001) and human immunodeficiency virus type 1 (HIV-1) infection (RO = 3.91, P <.001) were both associated with nonresponse to full-dose vaccination. Further associations were observed with single nucleotide polymorphisms (SNPs) at the IL2 and IL4 loci along with insertion/deletion variants at the IL12B locus (P =.003-.01). Host genetic associations were independent of one another as well as other HLA (A, B, C, and DQB1) and cytokine gene (IL4R, IL6, IL10, and TNF) variants. Statistical adjustments for nongenetic factors (gender, ethnicity, age, HIV-1 infection, and vaccination protocols) did not substantially alter the strengths of the genetic relationships. The overall distribution pattern of genetic variations was similar between the analyzed vaccinees and additional adolescents (n = 292) from the same cohort. In conclusion, DRB1*07 (or a closely linked allele) and immunoregulatory cytokine gene polymorphisms correlate with variable immune response to recombinant HBV vaccines.

Co-immunization with plasmid IL-12 generates a strong T-cell memory response in mice

Plasmid encoded exogenous IL-12 delivered as a DNA vaccine adjuvant has been shown to improve vaccine-induced immunity. In particular, pIL-12 greatly improves antigen (Ag)-specific cytotoxic tlymphocyte (CTL) activity in immunized mice. The longevity of this response has not previously been studied in detail. We have studied the effect of co-immunization with pIL-12 on HIV gp160 and Influenza A Hemeagglutinnin-specific memory immune responses. Mice co-immunized with pIL-12 and plasmid encoded antigens maintained a greater memory response than those immunized with the plasmid antigen alone which could be measured at least 6 months after vaccination. Further, this translated to an improved outcome after challenge of long term rested mice that were previously immunized. The strength of the immune response as well as the number of Ag-specific T-cells is proportional to the number of Ag-specific cells primed by the vaccination regimen.

Construction of hepatitis B virus X gene expression vector in eucaryotic cells and its transfection in HL-7702 cells

AIM: To establish a human hepatocyte cell line which can express hepatitis B virus (HBV) X gene.

METHODS: HBV X gene was obtained through PCR techn-ology. After A-tailing added, X gene was connected into vector PUCmT. Vector PUCmT-X and PcDNA3 were digested with EcoRI and HindIII. The fragments of X and PcDNA3 were connected to establish reconstituted plasmid PcDNA3-X. Then PcDNA3-X and PcDNA3 were transfected into HL-7702 cells by lipid-mediated transfection. After selected with G418, HL-7702/HBx cells were analysed by the reverse transcription-PCR to confirm the steady expression of X gene in HL-7702.

RESULTS: Reconstituted plasmid PcDNA3-X included the anticipated fragment of HBV X gene was proved by auto-sequencing assay. RT-PCR analysis showed that reconstituted plasmid PcDNA3-X could express the X protein efficiently in HL-7702 cells.

CONCLUSION: Hepatocyte can express HBV X gene, which is an ideal model to study the effect of HBV X gene on the development of hepatitis and hepatocelular carcinoma.

Construction of human CD81 eukaryotic expression vector and expression of the gene segment in COS-7 cell line

AIM: To construct a human CD81 eukaryotic expression vector and to analyze the expression of CD81 in COS-7 cells.

METHODS: CD81 gene from the pMD18-T-CD81 vector with double-enzyme digestion was cloned into the pVAX1 eukaryotic expression vector, named pVAX1-CD81. The recombinant vector pVAX1-CD81 and pVAX1 as controls were transfected into COS-7 cells by lipofectamine, and the transient expression product on the transfected cells was analyzed with anti-CD81 monoclonal antibody by indirect immunofluorescence assay (IFA).

RESULTS: The identification of the eukaryotic expression vector pVAX1-CD81 by PCR and restriction enzyme analysis showed that CD81 gene was rightly inserted into the vector; and the product of the CD81 gene was successfully expressed on surface of COS-7 cells.

CONCLUSION: The eukaryotic expression vector with CD81 gene is constructed and efficiently expressed in COS-7 cells. The results indicate that the transfected CD81 cells will need to further studies on the roles of CD81 in the process of HCV infection and entrance to cells.

Screening and identification of mimotope of gastric cancer associated antigen MGb1-Ag

AIM: Using a monoclonal antibody against gastric cancer antigen named MGb1 to screen a phage-displayed random peptide library fused with coat protein pIII in order to get some information on mimotopes.

METHODS: Through affinity enrichment and ELISA screening, positive clones of phages were amplified. 10 phage clones were selected after three rounds of biopanning and the ability of specific binding of the positive phage clones to MGb1-Ab were detected by ELISA assay (DNA sequencing was performed and the amino acid sequences were deduced) By blocking test, specificity of the mimic phage epitopes was identified.

RESULTS: There were approximately 200 times of enrichment about the titer of bound phages after three rounds of biopanning procedures. DNA of 10 phage clones after the third biopanning was assayed and the result showed that the positive clones had a specific binding activity to MGb1-Ab and a weak ability of binding to control mAb or to mouse IgG. DNA sequencing of 10 phage clones was performed and the amino acid sequences were deduced. According to the homology of the amino acid sequences of the displayed peptides, most of the phage clones had motifs of H(x)Q or L(x)S. And these 10 phage clones could also partly inhibit the binding of MGb1-Ab to gastric cancer cell KATO-III. The percentage of blocking was from (21.0 ± 1.6)% to (39.0 ± 2.7)%.

CONCLUSION: Motifs of H(x)Q and L(x)S selected and identified show a high homology in the mimic epitopes of gastric cancer associated antigen. There may be one or more clones which can act as candidates of tumor vaccines.