Tiantan Vaccinia Research Articles

Enhancement of DNA vaccine-induced immune responses by a 72-bp element from SV40 enhancer

Although DNA vaccine is considered as the next generation of vaccine, most DNA vaccine candidates are still suffering from the relatively weak immunogenicity despite the increased dosage of plasmid DNA administered. In order to enhance the immune responses elicited by a codon-optimized HIV gag DNA vaccine, a modified plasmid vector pDRVI1.0 and a booster immunization with replicating Tiantan vaccinia (RTV) strain expressing the same gene were employed. Vector pDRVI1.0 was constructed through inserting the 72-bp element from the SV40 enhancer, which was reported promoting nuclear transport of plasmid DNA, to the upstream of cytomegalovirus enhancer/promoter region of the plasmid vector pVR1012. Gene expression levels from expression plasmids based on pDRVI1.0 and pVR1012 were tested. Humoral and cellular immune responses induced by DNA vaccine alone or DNA prime-RTV boost regimen were determined in mice. It was shown that the 72-bp element significantly enhanced the gene expression level in non-dividing cells. gag-specific humoral and cellular immune responses induced by DNA vaccination were both significantly improved, while the Th1/Th2 balance was not obviously affected by the 72-bp element. RTV boosting further significantly enhanced DNA vaccine-primed antibody and T cell responses in a Th1-biased manner. The 72-bp SV40 enhancer element should be included in the DNA vaccine vector and RTV strain is a very efficient live vector for boosting immunization.

Comparison of immunogenicity between codon optimized HIV-1 Thailand subtype B gp140 and gp145 vaccines

HIV-1 pandemic posed an unprecedented challenge to the global health and it is believed that an effective vaccine will be the final solution against HIV-1. HIV-1 envelope is the primary immunogen in developing neutralization antibody based HIV vaccine. To define the suitable Env derived immunogen, we systemically compared the immunogenicity of gp140 and gp145 in a DNA vaccination alone and a prime-boost modalities. Two DNA vaccines and two recombinant Tiantan vaccinia vaccines (rTTV) were constructed for vaccination of female Balb/c mice. Elispot assay was used to read out the T cell immunity and ELISA assay was used to quantify antibody immunity. PLL (poly-L-leucine)-ELISA assay was used in linear antibody epitope mapping. Mice primed with gp145 tended to elicit more Env-specific T cells responses than those primed with gp140, significant difference was observed in DNA immunization alone. The ultimate T cell responses in prime-boost regimen tend to be determined mainly by the priming efficacy. Linear antibody epitope mapping displayed that sera raised by gp145 priming were vigorously reactive to more peptides than that by gp140. Our data demonstrated HIV-1 Thailand B-derived gp145 may raise higher T-cell responses and broader linear peptide-specific antibody responses than gp140 does. However, it remains to be determined that how these observations are relevant to the neutralization of antibody activities.

Mucosal priming with PEI/DNA complex and systemic boosting with recombinant TianTan vaccinia stimulate vigorous mucosal and systemic immune responses

An effective vaccine strategy for HIV-1 will probably requires the induction and maintenance of both humoral and cellular immunity. We tested a new prime–boost approach of intranasal priming with 10 μg DNA plasmid in the PEI/DNA complexes and boosting with 10 7 PFU of replicative recombinant TianTan vaccinia virus (rTTV) expressing HIV-1 Gag in BALB/c mice. Intranasal priming with PEI/DNA complexes elicited strikingly stronger HIV-specific T-cell ( p = 0.0358) and IgA immune responses at mucosal sites of lung ( p = 0.0445) and vaginal tract ( p = 0.0469) than intranasal priming with naked DNA, though both are followed by the same rTTV boosting. Furthermore, an intramuscular boosting with rTTV could profoundly enhance both T-cell and antibody immune responses raised by intranasal priming. These results demonstrate that the combination of intranasal priming with PEI/DNA complexes and systemic boosting with rTTV is a preferable regimen for induction of both T-cell and humoral immune responses.

Sequential priming and boosting with heterologous HIV immunogens predominantly stimulated T cell immunity against conserved epitopes

The effort to develop an effective preventive vaccine against HIV-1 infection is challenged by the wide genetic diversity of HIV-1 among different isolates. To explore a new vaccination strategy by using heterologous HIV immunogens derived from different clades for sequential priming and boosting. HIV Env and Gag immunogens derived from Thailand B (B'), C/B' recombinant and A/E recombinant were selected as these three clades account for 29%, 45% and 15% of HIV-1 prevalence in China, respectively. Three humanized fusion genes of env and gag derived from those three clades were synthesized and inserted into DNA and recombinant Tiantan vaccinia vectors as model vaccines. C57BL/6 and Balb/c mice were used as animal model. Peptides spanning the entire Env and Gag were used as stimuli and Elispot assay was used to assess the T cell immunity. Sequential priming and boosting was observed with heterologous HIV immunogens predominantly stimulated T cell immunity against conserved epitopes, whereas a single vaccine derived from one clade or the mixture of multiple vaccines from different clades primarily raised T cells against less conservative or non-conservative epitopes. This is the first demonstration of a practical strategy to raise immune responses against conserved epitopes. This strategy has important implications for vaccine development against HIV and other pathogens that have high genetic diversity, such as influenza.

Intranasal priming with HIV DNA vaccine and systemic boosting with recombinant vaccinia induce vigorous immune responses: experiment with mice

To explore the strategy to raise both mucosal and systemic anti-HIV-1 immunity. Eighteen BALB/c rats were randomly divided into 2 groups, experimental group and control group. The experimental group were further subdivided into 4 subgroups of 3 mice: 3-dose HIV DNA vaccine group, 3-dose DNA vaccine + cholera toxin (CT) adjuvant subgroup, 1-dose recombinant Tiantan strain vaccinia-based vaccine subgroup, and 3-dose DNA vaccine + CT adjuvant + Tiantan strain vaccinia-based vaccine subgroup. The control group was subdivided into 2 subgroups of 3 mice: 3-dose DNA blank vector subgroup, and 3-dose DNA blank vector + Tiantan strain vaccinia-based vaccine subgroup. Intranasal administration of DNA vaccine-based vaccine (10 microg) was done on the days 0, 14, and 28 as the mucosal priming, and recombinant Tiantan vaccinia (1 x 10(7) PFU) was injected intramuscularly as systemic boosting on the day 42. On the day 56 the mice were killed and specimens of serum, nasopharynx wash, lung wash, and spleen were collected and splenocytes were isolated. Splenocytes were added into the phosphate-buffered saline with anti-mouse interferon-gamma (IFN-gamma) envelop antibody to count the number of spot-forming cells (SFCs). Indirect ELISA was used to detect the HIV-1 specific antibody in the nasopharynx wash and lung wash. Immunohistochemistry was used to detect the intracellular staining of IFN-gamma in the splenocytes. The number of spot forming cells in the HIV-1 DNA vaccine + CT adjuvant group was (14 +/- 11) SFCs/10(6) splenocytes, significantly more than that of the HIV-1 DNA vaccine group [(2 +/- 1) SFCs/10(6) spleen cells (P < 0.01). The number of SFCs of the 1-dose DNA-vaccine subgroup was [(30 +/- 18) SFCs/10(6) spleen cells], significantly higher than that of the only DNS vaccine group (P < 0.01). The number of SFCs of DNA vaccine + CT adjuvant + recombinant Tiantan vaccinia-based vaccine was (61 +/- 35) SFCs/10(6) splenocytes, significantly higher than those of the other groups (all P < 0.01). Flow cytometry showed that the rate of HIV-1 Gag specific CD8(+) T cell was 1.8% +/- 1.4%. The value of specific IgG of the DNA vaccine + adjuvant + Tiantan vaccinia-based vaccine was 1.50 +/- 0.30, significantly higher than those of the blank vector, single-dose Tiantan vaccinia-based vaccine, and single-dose DNA vaccine + CT adjuvant subgroups (0.42 +/- 0.02, 0.74 +/- 0.13, and 0.75 +/- 0.02 respectively, all P < 0.05). In different subgroups the levels of specific IgA in the lung wash were all higher than those in the nasopharynx wash. The levels of specific IgA in the lung and nasopharynx wash of the DNA vaccine + CT adjuvant subgroup were higher than those of the other subgroups whether or not with boosting of Tiantan. The specific IgA levels of the groups enhanced by Tiantan vaccinia-based vaccine were all significantly higher than those of the corresponding subgroups without enhancement (all P < 0.01). The IgA level of lung wash of the DNA vaccine + CT adjuvant subgroup was 1.82 +/- 0.76, significantly higher than that of the one-dose Tiantan vaccinia-based vaccine group (0.52 +/- 0.19, P < 0.05). The vaccination modality of mucosal priming and systemic boosting induces both mucosal and systemic immune responses.

Host range, growth property, and virulence of the smallpox vaccine: Vaccinia virus Tian Tan strain

Vaccinia Tian Tan (VTT) was used as a vaccine against smallpox in China for millions of people before 1980, yet the biological characteristics of the virus remain unclear. We have characterized VTT with respect to its host cell range, growth properties in vitro, and virulence in vivo. We found that 11 of the 12 mammalian cell lines studied are permissive to VTT infection whereas one, CHO-K1, is non-permissive. Using electron microscopy and sequence analysis, we found that the restriction of VTT replication in CHO-K1 is at a step before viral maturation probably due to the loss of the V025 gene. Moreover, VTT is significantly less virulent than vaccinia WR but remains neurovirulent in mice and causes significant body weight loss after intranasal inoculation. Our data demonstrate the need for further attenuation of VTT to serve either as a safer smallpox vaccine or as a live vaccine vector for other pathogens.

Immunogenicity and relative attenuation of different vaccinia-rabies virus recombinants.

Immunogenicity and relative attenuation were examined for the following Tian Tan strain vaccinia-rabies recombinant viruses: 1) NGc-1, which coexpresses the glycoprotein (G) and nucleocapsid protein (N) of the rabies virus Challenge Virus Standard (CVS) strain; 2) Nc-1, which expresses the CVS N; 3) Gc-2, Gc-3, Gc-4, and Gc-5, which express CVS G via promoters from different vaccinia strains or from different vaccinia genome loci; 4) Ga-1, which expresses the G of rabies virus strain aG; and 5) Gas-1; which expresses the carboxyltruncated G ectodomain (Gs) of strain aG. All but Nc-1 and Gas-1 induced rabies virus neutralizing antibodies (VNAs) and protected groups of mice at very high frequencies from intramuscular (IM) or intracranial (IC) challenge with CVS or SW1 Shanghai dog street rabies virus (SRV); Nc-1 and Gas-1 were partly protective, more frequently against IM challenge. NGc-1 and Gc-5 appeared to induce high levels of VNAs sooner after immunization than the other constructs in mice. Relative attenuation assessed by IM infection of neonatal mice, IC infection of adult mice, and intradermal infection of rabbits with varying doses was best for NGc-1. All the recombinants were at least 100-fold more attenuated than the parent, Tian Tan vaccinia virus. Gc-2, Gc-3, Gc-4, Gc-5, and NGc-1 induced VNAs after immunization of dogs, and a subset of VNA-positive animals vaccinated with NGc-1 or Gc-3 were protected against an otherwise lethal IM injection of SRV at 21 days after vaccination.

Vaccinia virus serpins B13R (SPI-2) and B22R (SPI-1) encode Mr 38.5 and 40K, intracellular polypeptides that do not affect virus virulence in a murine intranasal model

A characterization of genes B13R (SPI-2) and B22R (SPI-1) from vaccinia virus strain Western Reserve (WR) is presented. These genes are transcribed early during infection and the predicted encoded proteins show similarity to the superfamily of serine protease inhibitors (serpins). The 5′ transcriptional initiation site of each gene was mapped by primer extension experiments to 71–72 and 31 nucleotides upstream of the B13R and B22R open reading frames (ORFs), respectively. Each ORF was expressed in Escherichia coli and specific antisera were raised against the protein produced. These antisera were used to identify the B13R- and B22R-encoded proteins in vaccinia virus-infected cells as stable, intracellular, nonglycosylated proteins of M r 38.5K and M r 40K, respectively. The B22R gene product was detected in all orthopoxviruses tested including cowpox, rabbitpox, and vaccinia strains WR, Copenhagen, Tashkent, Tian Tan, Lister, Wyeth, IHD-J, and IHD-W. In contrast, the B13R gene product had a more limited distribution and was not detected in Copenhagen, Tashkent, Lister, and Tian Tan. Viable virus deletion mutants that lacked only B13R or B22R coding sequences (ΔB13R and ΔB22R) and revertant viruses in which the deleted gene was restored were constructed by transient dominant selection. The growth of the deletion mutants in cell culture was indistinguishable from that of wild-type virus. Additionally the virulence of each deletion mutant was indistinguishable from wild-type and revertant viruses in a murine intranasal model.