Tiantan Vaccinia Research Articles

TianTan vaccinia virus-based EBV vaccines targeting both latent and lytic antigens elicits potent immunity against lethal EBV challenge in humanized mice

ABSTRACT Epstein–Barr virus (EBV) infection has been related to multiple epithelial cancers and lymphomas. Current efforts in developing a prophylactic EBV vaccine have focused on inducing neutralizing antibodies. However, given the lifelong and persistent nature of EBV infection following primary infection, it is rationalized that an ideal vaccine should elicit both humoral and cellular immune responses targeting multiple stages of the EBV lifecycle. This study used a DNA vector and a TianTan vaccinia virus to express key EBV antigens, including BZLF1, EBNA1, EBNA3B, and gH/gL, to generate multi-antigen vaccines. The multi-antigen vaccine expressing all four antigens and the multi-antigen vaccine expressing BZLF1, EBNA1, and EBNA3B showed comparable protection effects and prevented 100% and 80% of humanized mice, respectively, from EBV-induced fatal B cell lymphoma by activating BZLF1, EBNA1, and EBNA3B specific T cell. The vaccine expressing lytic protein BZLF1 elicited stronger T cell responses and conferred superior protection compared to vaccines targeting single latent EBNA1 or EBNA3B. The vaccine solely expressing gH/gL exhibited no T cell protective effects in our humanized mice model. Our study implicates the potential of EBV vaccines that induce potent cellular responses targeting both latent and lytic phases of the EBV life cycle in the prevention of EBV-induced B cell lymphoma.

DNA vaccine prime and replicating vaccinia vaccine boost induce robust humoral and cellular immune responses against MERS-CoV in mice

As of December 2022, 2603 laboratory-identified Middle East respiratory syndrome coronavirus (MERS-CoV) infections and 935 associated deaths, with a mortality rate of 36%, had been reported to the World Health Organization (WHO). However, there are still no vaccines for MERS-CoV, which makes the prevention and control of MERS-CoV difficult. In this study, we generated two DNA vaccine candidates by integrating MERS-CoV Spike (S) gene into a replicating Vaccinia Tian Tan (VTT) vector. Compared to homologous immunization with either vaccine, mice immunized with DNA vaccine prime and VTT vaccine boost exhibited much stronger and durable humoral and cellular immune responses. The immunized mice produced robust binding antibodies and broad neutralizing antibodies against the EMC2012, England1 and KNIH strains of MERS-CoV. Prime-Boost immunization also induced strong MERS-S specific T cells responses, with high memory and poly-functional (CD107a-IFN-γ-TNF-α) effector CD8+ T cells. In conclusion, the research demonstrated that DNA-Prime/VTT-Boost strategy could elicit robust and balanced humoral and cellular immune responses against MERS-CoV-S. This study not only provides a promising set of MERS-CoV vaccine candidates, but also proposes a heterologous sequential immunization strategy worthy of further development.

Cross-reactive antibodies against monkeypox virus exist in the population immunized with vaccinia Tian Tan strain in China.

Monkeypox virus (MPXV) belongs to the Orthopoxvirus genus. The worldwide outbreak of MPXV in 2022 has caused widespread concerns. Cross-reactive antibodies induced by vaccinia-inoculation can provide protection against reinfection by MPXV. The vaccinia Tian Tan (VTT) strain, which was widely inoculated in the Chinese population before the 1980s, has genomic differences from other vaccinia strains, although they all belong to the orthopoxviruses family. The current seroprevalence of VTT-vaccinated populations remains unclear more than four decades after the termination of vaccination campaigns in China. Our results showed that cross-reactive IgG antibodies against MPXV were present in 31.8% (75/236) of vaccinees four decades after VTT-vaccination, suggesting that vaccination with VTT may provide long-term protection against MPXV infection in some individuals.

Exploration of a Sequential Gp140-Gp145 Immunization Regimen with Heterologous Envs to Induce a Protective Cross-Reactive HIV Neutralizing Antibody Response In Non-human Primates.

Raising a heterologous tier 2 neutralizing antibody (nAb) response remains a daunting task for HIV vaccine development. In this study, we explored the utility of diverse HIV-1 envelope (Env) immunogens in a sequential immunization scheme as a solution to this task. This exploration stemmed from the rationale that gp145, a membrane-bound truncation form of HIV Env, may facilitate the focusing of induced antibody response on neutralizing epitopes when sequentially combined with the soluble gp140 form as immunogens in a prime-boost mode. We first showed that gp140 DNA prime-gp145 Tiantan vaccinia (TV) boost likely represents a general format for inducing potent nAb response in mice. However, when examined in rhesus macaque, this modality showed little effectiveness. To improve the efficacy, we extended the original modality by adding a strong protein boost, namely native-like SOSIP.664 trimer displayed on ferritin-based nanoparticle (NP), which was generated by a newly developed click approach. The resulting three-immunization regimen succeeded in eliciting tier-2 nAb response with substantial breadth when implemented in rhesus macaque over a short 8-week schedule. Importantly, the elicited nAb response was able to effectively contain viremia upon a heterologous SHIV challenge. Collectively, our studies highlighted that diversification of Env immunogens, in both types and formulations, under the framework of a sequential immunization scheme might open new opportunity toward HIV vaccine development.Electronic supplementary materialThe online version of this article (10.1007/s12250-021-00361-3) contains supplementary material, which is available to authorized users.

Evaluation of Tumor Specificity and Immunity of Thymidine Kinase-Deleted Vaccinia Virus Guang9 Strain.

PurposeOncolytic viruses are emerging as promising options for clinical cancer treatment due to their inherent ability of tumor tropism and oncolytic property. Aside from tumor lysis, oncolytic viruses can induce host immune responses against tumor cells and may thus be viewed as a form of immunotherapy.MethodsThe attenuated vaccinia VG9-Luc, which originated from Chinese vaccinia Tian Tan strain, was constructed to express firefly luciferase for bioluminescence imaging and to disrupt the thymidine kinase gene for promoting tumor specificity. An in vivo bioluminescence imaging was performed to observe the virus distribution in live mice. The titers of neutralizing antiviral and antitumor antibodies in plasma were determined by time-resolved fluoroimmunoassay.ResultsExcept BALB/c mice treated with intravenous virus injection, all immunocompromised and immunocompetent mice showed obvious tumor targeting ability of vaccinia VG9-Luc. Besides, host immune response activated by vaccinia VG9-Luc showed the production of antiviral and antitumor antibodies, the process of which was similar between intravenous and intratumoral viral delivery systems. The results indicated that virus infection promoted tumor-specific immunity by increasing the production of antitumor antibodies. Moreover, virus reinjection was performed and a more rapid viral clearance was observed in immunocompetent mice compared with first virus infection.ConclusionThe thymidine kinase-deleted vaccinia Guang9 strain, which has the properties of tumor specificity and antitumor immunity, is a promising candidate vector for cancer therapy.

Antitumor efficacy of cytosine deaminase-armed vaccinia virus plus 5-fluorocytosine in colorectal cancers

BackgroundVaccinia viruses have emerged as attractive therapeutic candidates for cancer treatment due to their inherent ability of tumor tropism and oncolytic property. Cytosine deaminase (CD), which is derived from bacteria or yeast, can convert a relatively nontoxic prodrug 5-fluorocytosine (5-FC) into the active anticancer drug 5-Fluorouracil (5-FU). Vaccinia virus armed with the prodrug-activator CD gene would result in augmented antitumor effects that combined the effect of vaccinia virus and 5-FU together, and particularly limited the anticancer drug to tumor regions.MethodsThe attenuated vaccinia Tian Tan strain Guang 9 (VG9), with active yeast CD expression and thymidine kinase (TK) deficiency, was successfully constructed. Then, in vitro and in vivo antitumor efficacy of vaccinia VG9-CD plus 5-FC administration was evaluated in colorectal cancer cells.ResultsVaccinia viruses displayed different oncolytic potency in vitro cells, no relationship with whether they were cancer cells or normal cells. In colorectal tumor models, mice treated with vaccinia VG9-TK− showed better tumor remission ability and prolonged survival. Moreover, vaccinia VG9-CD in combination with gavage administration of 5-FC displayed the best antitumor efficacy, especially for the prolongation of survival.ConclusionsVaccinia VG9-CD in combination with 5-FC plays combined effect of vaccinia virus and chemotherapy, and becomes a promising virotherapy for cancer.

Virotherapy-recruited PMN-MDSC infiltration of mesothelioma blocks antitumor CTL by IL-10-mediated dendritic cell suppression

ABSTRACT Antitumor cytotoxic T lymphocytes (CTLs) are essential for immune surveillance, yet the blockade of eliciting such CTLs during oncolytic virotherapy remains incompletely understood. Here, we show that oncolysis of mesothelioma by modified vaccinia Tiantan (MVTT) induces damage-associated molecular patterns exposure. Although MVTT leads to regression of established mesothelioma dose-dependently, antitumor CTLs are rarely induced. Mechanistically, MVTT virotherapy generates C-X-C chemokines that recruit CXCR2-expressing polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) into tumor microenvironment, where they suppress dendritic cells (DCs) by producing IL-10 and halt CTL responses. During the virotherapy, however, depletion of PMN-MDSCs but not of monocytic (M)-MDSCs results in the induction of potent antitumor CTLs that not only eradicate established mesothelioma but also prevent the second tumor challenge. Our findings suggest that vaccinia virotherapy may combine strategies that prevent the chemotactic recruitment of PMN-MDSCs, block their suppression on DCs or deplete PMN-MDSCs in order to induce potent CTLs for tumor eradication.

Construction of an attenuated Tian Tan vaccinia virus strain by deletion of TA35R and TJ2R genes

rVTT-TA35-TJ, an attenuated vaccinia virus Tian Tan strain (VTT), was constructed by knocking out two non-essential gene fragments (TA35R and TJ2R) related to virulence, immunomodulation, and host range; and by combining double marker screening with exogenous and endogenous selectable marker knock-out techniques. Here, the shuttle plasmids pSK-TA35 and pSK-TJ were constructed, containing two pairs of recombinant arms: early and late strong promoter pE/L and EGFP as an exogenous selectable marker. The recombinant vaccinia virus rVTT-TA35-TJ without exogenous selection markers was then obtained through homologous recombination technology and the Cre/loxP system. Knocking out the two gene fragments does not affect the replication ability of the virus and displays a good genetic stability. Furthermore, a series of in vivo and in vitro experiments demonstrate that although virulence of rVTT-TA35-TJ is attenuated significantly, high immunogenicity was maintained. These results support the potential development of rVTT-TA35-TJ as a safe viral vector or vaccine.

DNA prime/MVTT boost regimen with HIV-1 mosaic Gag enhances the potency of antigen-specific immune responses

HIV-1 diversity and latent reservoir are the major challenges for the development of an effective AIDS vaccine. It is well indicated that Gag-specific CD8+ T cells serve as the dominant host immune surveillance for HIV-1 control, but it still remains a challenge for vaccine design to induce broader and stronger cytotoxic T cell immunity against the virus. Genetic variation of the HIV-1 gag gene across different clades is one of the reasons for the reduction of antigenic epitope coverage. Here, we report an immunization strategy with heterologous vaccines expressing a mosaic Gag antigen aimed to increase antigenic breadth against a wider spectrum of HIV-1 strains. Priming using a DNA vaccine via in vivo electroporation, followed by boosting with a live replication-competent modified vaccinia TianTan (MVTT) vectored vaccine, elicited greater and broader protective Gag-specific immune responses in mice. Compared to DNA or MVTT homologous immunization, the heterologous DNA/MVTT vaccination resulted in higher frequencies of broadly reactive, Gag-specific, polyfunctional, long-lived cytotoxic CD8+ T cells, as well as increased anti-Gag antibody titer. Importantly, the DNA/MVTT heterologous vaccination induced protection against EcoHIV and mesothelioma AB1-Gag challenges. In summary, the stronger protective Gag-specific immunity induced by the heterologous regimen using two safe vectors shows promise for further development to enhance anti-HIV-1 immunity. Our study has important implications for immunogen design and the development of an effective HIV-1 heterologous vaccination strategy.

Generation of an Attenuated Tiantan Vaccinia Virus Strain by Deletion of Multiple Genes.

An attenuated vaccinia virus-MVTTEAB-was constructed by deletion of non-essential gene segments related to the immunomodulatory and virulence functions of the vaccinia virus Tiantan strain (VVTT). The shuttle plasmids pTC-EGFP, pTE-EGFP, pTA35-EGFP, pTB-EGFP, and pTA66-EGFP were constructed and combined with the early and late strong promoter pE/L and EGFP as an exogenous selectable marker. Then, through the homologous recombination technology and Cre/loxP system, the following gene fragments were gradually knocked out one by one: TC7L-TK2L, TE3L, TA35R, TB13R, and TA66R. Ultimately, the five-segment-deleted attenuated strain MVTTEAB was obtained. Knockout of these segments and genetic stability of MVTTEAB were confirmed, and it was also shown that knockout of these segments did not affect the replication ability of the virus. Further, a series of in vivo and in vitro experiments demonstrated that the virulence of MVTTEAB was attenuated significantly, but at same time, high immunogenicity was maintained. These results indicate that MVTTEAB has potential for clinical use as a safe viral vector or vaccine with good attenuation and immunogenicity.

Bioluminescence imaging of a tumor-selective, thymidine kinase-defective vaccinia virus Guang9 strain after intratumoral or intraperitoneal administration in mice.

Vaccinia virus has been used as an oncolytic virus because of its capacity to preferentially infect tumors rather than normal tissues. The vaccinia Tian Tan strain, used as a vaccine against smallpox for millions of people in China, is a promising candidate for cancer therapy. In this study, we constructed an attenuated Tian Tan strain of Guang9 with a disrupted thymidine kinase gene to enhance tumor selectivity and an inserted firefly luciferase to monitor the viral distribution by in vivo bioluminescence imaging. Living animal imaging confirmed the high specificity of vaccinia Guang9 for tumor targeting after intratumoral and intraperitoneal administration. In addition, the vaccinia Guang9 strain produced higher in vivo luciferase activity and endured longer in immunocompromised nude mice than in immunocompetent C57BL/6 mice, all of which had been tumor-challenged. The luciferase activity and viral titers in excised tissues confirmed these conclusions. These data provide evidence for the safety and efficacy of the clinical application of vaccinia virus, which would be a promising approach for cancer therapy.

Construction of a recombinant HIV-1 gp140 protein vaccine and evaluation of its immunogenicity

Objective To construct a recombinant HIV-1 gp140 protein vaccine and to evaluate its immunogenicity. Methods Four expression vectors containing different signal peptides including DRVI, IL-2, venom and chitinase were constructed for the expression of gp140 protein clones. Western blot assay was performed to evaluate the expression efficiency of the constructed expression vectors. The cleavage of signal peptides was analyzed by sequencing analysis. The gp140 protein clones with different lengths of C-terminus were constructed and then comparatively analyzed for the screening of optimized recombinant HIV-1 gp140 antigen. Guinea pigs were immunized with different strategies and the potency of vaccination was evaluated by detecting the binding antibodies and neutralizing antibodies after immunization. Results DRVI, the designed signal peptide, had the advantages in determining the efficiency of protein secretion and signal peptide cleavage. Compared with the co-immunization with DNA and recombinant Tiantan vaccinia (rTV) HIV vaccines, immunization of guinea pigs with the recombined gp140 protein vaccine alone could induce higher levels of binding antibodies and neutralizing antibodies. The gp140 protein with long C-terminus was slightly better than the one with short C-terminus in eliciting immune response, but no significant differences were found between them. Conclusion The optimized HIV-1 gp140 protein vaccine with appropriate protein signal peptide and C-terminus was successfully constructed and turned out to be effective in eliciting stronger immune response. Key words: HIV-1 gp140 protein; Antigen design; Immune evaluation

Strong IgA-mediated mucosal immune responses elicited in BALB/c mice primed with Vaccinia Tiantan-based HIV vaccine intramuscularly and boosted with protein intranasally

Objective To analyze the mucosal immune responses induced in BALB/c mice after immunization with Vaccinia Tiantan-based HIV vaccine in combination with protein and to evaluate the efficacy of different immune strategies and adjuvants. Methods The BALB/c mice were intramuscularly or intranasally immunized with the recombinant Vaccinia virus Tiantan strain (rTV) carrying CN54 Gag-Pol-Env gene and boosted with the gp140 protein and MF59 adjuvant by intramuscular, intranasal or subcutaneous injection. Serum, saliva and vaginal lavage samples were collected from the BALB/c mice. The titers of antigen specific IgG and IgA were detected by ELISA. Results Significantly enhanced mucosal immune responses were induced by immunization with gp140 protein used in combination with MF59 adjuvant. The IgA antibodies elicited in mice mucosal tissues by gp140 protein and MF59 adjuvant were as high as those induced by gp140 protein and cholera toxin subunit B or recombinant flagellin adjuvant. High tiers of gp140-specific IgA antibodies were observed in serum, saliva and vaginal lavage samples from the mice intramuscularly primed with rTV and intranasally boosted with gp140 protein and MF59 adjuvant. The tiers of IgA antibodies in serum and mucosal tissue samples were 1∶15 000 and 1∶600, respectively. Conclusion High titers of mucosal IgA antibodies were elicited in BALB/c mice intramuscularly primed with Vaccinia Tiantan-based HIV vaccine and intranasally boosted with gp140 protein and MF59 adjuvant, especially in vaginal and oral tissues. This immunization strategy might be able to block the heterosexual transmission of HIV-1 through vaginal and oral mucosa. Key words: HIV Vaccine; Vaccinia Tiantan strain; HIV protein vaccine; Mucoantibody

Development of HIV-1 vaccines based on replication competent Tiantan vaccinia vector in China

BackgroundA vaccine is the best solution to stop the AIDS pandemic, but how to develop a vaccine is an unprecedented challenge to the global scientific community. The HIV vaccine programme of the China Center for Disease Control and Prevention (CDC) is being developed through careful selection of the representative circulating HIV-1 strain CRF07 in China, through a nationwide molecular epidemiology survey involving all provinces. The replication competent Tiantan vaccinia (VTT, smallpox vaccine in China) was used as an AIDS vaccine vector. A DNA/rTV HIV-1 vaccine containing gag, pol, and env genes has been developed. In preclinical tests in monkeys, this vaccine gives high protection (more than 80%) against homologous SHIV (SHIV97001) challenge and partial protection (50%) against heterologous SHIV (SHIV SF162 P3) challenge when boosted with HIV-1 envelop protein. The aim of this study was to test the safety and immunological effect of the HIV-1 vaccine in healthy human volunteers. MethodsA double-blind, placebo-controlled phase 1 trial was done at the Peking Union Medical College Hospital, Beijing, China. We enrolled HIV-1 uninfected healthy adults with or without history of smallpox vaccination. The subjects were randomly assigned to receive DNA alone (DNA 4 mg, DNA-H/rTV (DNA 4 mg), DNA-L/rTV (DNA 2 mg), or placebo. Randomisation was done by the Division of Health Statistics, China CDC, using SAS version 9.1.2. Participants, site staff, laboratory personnel responsible for endpoint assays, and investigators were blinded as to treatment assignments during the trial. Participants were primed with DNA vaccine (4 mg, intramuscular) three times at 1 month intervals and boosted once with rTV (5×104 plaque-forming units, skin scratches). The participants were monitored for safety and immunological outcomes. Vaccine-induced immunogenicity were measured by the enzyme-linked immunospot assay, intracellular cytokine staining, and antibody assays. All available data were used, according to randomization assignment. The analyses for the primary objectives of safety and tolerability were descriptive. For the secondary analyses of immunogenicity, we used assay-specific predefined positivity criteria to categorise each individual as a responder or a non-responder at each time point. Between-group comparisons were based on Fisher's Exact Test for binary data and Wilcoxon rank sum tests for the magnitude of the response. The protocol was approved by the ethics committees of PUMCH and National Center for AIDS/STD Control and Prevention, China CDC. All participants provided written informed consent. This trial was registered at chictr.org, number ChiCTR-PRC-10001287. Findings36 HIV-1 uninfected healthy adults with or without history of smallpox vaccination were enrolled; ten participants were women, and the mean age of the participants was 28·28 years (6·46). Among the participants, 23 were vaccinia-naive, and 13 were vaccinia-vaccinated. Six participants received DNA alone, 12 participants received DNA-H/rTV, 12 participants received DNA-L/rTV, and six participants received placebo. 34 (94%) participants completed all study visits. Results of the completed phase 1 trial showed that DNA/rTV vaccines were well tolerated in participants. We detected HIV-1-specific binding antibody against gp140 protein and V1V2 in all volunteers. T-cell responses induced by the vaccines were found in two-thirds of participants and were multi-functional (IL2/IFN-g/TNF-α). Typical skin reaction in all rTV vaccinated 22 participants, enlargement of the lymph nodes under the same arm receiving rTV (13 cases), and slight fever (37·6°C for 1 day, 1 case) were observed. No severe adverse events related to the vaccines were found. InterpretationThe DNA/rTV vaccines are safe and stimulate an immunogenic response. In order to protect primate against heterologous SHIV challenges, HIV envelop proteins needed as a boosting immunogen. Study is required to further test the safety and immunogenicity of DNA/rTV vaccine in high-risk groups to HIV infection. It is worthwhile to compare the non-replicating pox vector of the Pox Protein public Private Partnership (p5 project) with the replicating Tiantan vector. The China CDC and US National Institutes of Health (NIH) have planned a joint phase 2b vaccine trial of the DNA/rTV of China CDC and gp145 of US NIH. FundingNational Science and Technology Major Projects for Infectious Diseases Control and Prevention (2008ZX10104 and 2012ZX10001008).

Simian immunodeficiency virus infection evades vaccine-elicited antibody responses to V2 region.

An effective AIDS vaccine should elicit protective antibody responses against HIV/simian immunodeficiency virus (SIV) infection. We recently reported that mucosal priming with a replicating modified vaccinia Tiantan virus (MVTTgpe)-based vaccine regimen induces durable protection against pathogenic SIVmac239 infection in rhesus monkeys. Here, we aim to conduct a comprehensive analysis on antigenic determinants recognized by specific antibody responses generated by vaccination and SIVmac239 infection. A novel yeast surface displayed antigen library of entire SIVmac239 envelope (Env) glycoprotein was established and validated to map the major antigenic determinants (MAD) in monkey sera elicited by vaccination and infection. MAD-directed antibody responses were further analyzed for correlation of protection. The yeast surface displayed library allows the mapping of SIV-specific linear and conformational MAD. The MVTTgpe-based regimen induces antibodies targeting mainly to 6 antigenic domains covering the entire gp160. Critically, this regimen induced a uniquely predominant antibody response against a distinct MAD in variable region 2 (V2) as compared with the Ad5gpe-based vaccine and SIVmac239 infection. This MAD was associated with a higher titer of anti-V2 antibody responses, which was inversely correlated with peak and set-point viral loads. Unexpectedly, the pathogenic SIVmac239 challenge evaded the vaccine-elicited anti-V2 antibody response. Instead of recalling B-cell memory responses to the V2 MAD, viral infection directed anti-V1V2 antibodies primarily to V1 region. Moreover, the anti-V1V2 antibody responses diminished significantly in infected macaques after they enter the stage of simian AIDS. Our findings have critical implications to AIDS vaccine efforts with focus on V2 region.

HIV-1 vaccines based on replication-competent Tiantan vaccinia protected Chinese rhesus macaques from simian HIV infection.

To assess the efficacy of HIV vaccines constructed from replication-competent Tiantan vaccinia virus (rTV) alone or combined with DNA in protecting Chinese rhesus macaques from homologous Simian/Human Immunodeficiency Virus (SHIV)-CN97001 challenge. The nef, gag, pol, and gp140 genes from strain CRF07_BC HIV-1 CN54 were selected to construct an HIV vaccine using the rTV or rTV/DNA vaccine. After vaccination, the vaccine and control groups were intravenously challenged with SHIV-CN97001 (32 MID50). HIV-specific antibodies and neutralizing antibodies, gp70 V1V2 binding antibodies, and cytotoxic T-lymphocyte responses were measured prospectively after vaccination with an ELISA, a virus infectivity assay in TZM-bl cells, and ELISPOT assays, respectively. Viral RNA was quantified after challenge with real-time reverse transcriptase-PCR (RT-PCR), and protection efficacy was determined with an analysis of CD8 lymphocyte depletion in vivo. Both rTV and DNA/rTV vaccine groups developed strong cellular and humoral responses against HIV-1 CN54 antigens, including Gag and Env, and also developed significant and persistent anti-Env antibodies and neutralizing antibodies after immunization. Both the rTV and DNA/rTV groups were significantly protected against SHIV-CN97001 or displayed lower viremia than the controls. After CD8 lymphocyte depletion, no viremia was detectable in the vaccinated monkeys, but rebounded rapidly in the control animals. Protection against infection correlated with vaccine-elicited neutralizing antibodies specific for homologous HIV-1 viruses. An rTV-based HIV-1 vaccine, with or without a DNA primer, provided protection from SHIV challenge in a macaque model. Replication-competent Tiantan vaccinia is a promising vector and should enable advances in HIV-1 vaccine development.

Correction: A Replicating Modified Vaccinia Tiantan Strain Expressing an Avian-Derived Influenza H5N1 Hemagglutinin Induce Broadly Neutralizing Antibodies and Cross-Clade Protective Immunity in Mice

Correction: A Replicating Modified Vaccinia Tiantan Strain Expressing an Avian-Derived Influenza H5N1 Hemagglutinin Induce Broadly Neutralizing Antibodies and Cross-Clade Protective Immunity in Mice

Generation of an attenuated Tiantan vaccinia virus by deletion of the ribonucleotide reductase large subunit

Attenuation of the virulence of vaccinia Tiantan virus (VTT) underlies the strategy adopted for mass vaccination campaigns. This strategy provides advantages of safety and efficacy over traditional vaccines and is aimed at minimization of adverse health effects. In this study, a mutant form of the virus, MVTT was derived from VTT by deletion of the ribonucleotide reductase large subunit (R1) (TI4L). Compared to wild-type parental (VTT) and revertant (VTT-rev) viruses, virulence of the mutant MVTT was reduced by 100-fold based on body weight reduction and by 3,200-fold based on determination of the intracranial 50% lethal infectious dose. However, the immunogenicity of MVTT was equivalent to that of the parental VTT. We also demonstrated that the TI4L gene is not required for efficient replication. These data support the conclusion that MVTT can be used as a replicating virus vector or as a platform for the development of vaccines against infectious diseases and for cancer therapy.

Fusion-expressed CTB improves both systemic and mucosal T-cell responses elicited by an intranasal DNA priming/intramuscular recombinant vaccinia boosting regimen.

Previous study showed that CTB (Cholera toxin subunit B) can be used as a genetic adjuvant to enhance the systemic immune responses. To further investigate whether it can also be used as a genetic adjuvant to improve mucosal immune responses, we constructed DNA and recombinant Tiantan vaccinia (rTTV) vaccines expressing OVA-CTB fusion antigen. Female C57BL/6 mice were immunized with an intranasal DNA priming/intramuscular rTTV boosting regimen. OVA specific T-cell responses were measured by IFN-γ ELISPOT and specific antibody responses were determined by ELISA. Compared to the nonadjuvant group (pSV-OVA intranasal priming/rTTV-OVA intramuscular boosting), pSV-OVA-CTB intranasal priming/rTTV-OVA-CTB intramuscular boosting group significantly improved the magnitudes of T-cell responses at spleen (1562 ± 567 SFCs/106 splenocytes versus 330 ± 182 SFCs/106 splenocytes, P < 0.01), mesenteric LN (96 ± 83 SFCs/106 lymphocytes versus 1 ± 2 SFCs/106 lymphocytes, P < 0.05), draining LNs of respiratory tract (109 ± 60 SFCs/106 lymphocytes versus 2 ± 2 SFCs/106 lymphocytes, P < 0.01) and female genital tract (89 ± 48 SFCs/106 lymphocytes versus 23 ± 21 SFCs/106 lymphocytes, P < 0.01). These results collectively demonstrated that fusion-expressed CTB could act as a potent adjuvant to improve both systemic and mucosal T-cell responses.

A Replicating Modified Vaccinia Tiantan Strain Expressing an Avian-Derived Influenza H5N1 Hemagglutinin Induce Broadly Neutralizing Antibodies and Cross-Clade Protective Immunity in Mice

To combat the possibility of a zoonotic H5N1 pandemic in a timely fashion, it is necessary to develop a vaccine that would confer protection against homologous and heterologous human H5N1 influenza viruses. Using a replicating modified vaccinia virus Tian Tan strain (MVTT) as a vaccine vector, we constructed MVTTHA-QH and MVTTHA-AH, which expresses the H5 gene of a goose-derived Qinghai strain A/Bar-headed Goose/Qinghai/1/2005 or human-derived Anhui Strain A/Anhui/1/2005. The immunogenicity profiles of both vaccine candidates were evaluated. Vaccination with MVTTHA-QH induced a significant level of neutralizing antibodies (Nabs) against a homologous strain and a wide range of H5N1 pseudoviruses (clades 1, 2.1, 2.2, 2.3.2, and 2.3.4). Neutralization tests (NT) and Haemagglutination inhibition (HI) antibodies inhibit the live autologous virus as well as a homologous A/Xingjiang/1/2006 and a heterologous A/Vietnam/1194/2004, representing two human isolates from clade 2.2 and clade 1, respectively. Importantly, mice vaccinated with intranasal MVTTHA-QH were completely protected from challenge with lethal dosages of A/Bar-headed Goose/Qinghai/1/2005 and the A/Viet Nam/1194/2004, respectively, but not control mice that received a mock MVTTS vaccine. However, MVTTHA-AH induced much lower levels of NT against its autologous strain. Our results suggest that it is feasible to use the H5 gene from A/Bar-headed Goose/Qinghai/1/2005 to construct an effective vaccine, when using MVTT as a vector, to prevent infections against homologous and genetically divergent human H5N1 influenza viruses.