Unpolarized release of vaccinia virus and HIV antigen by colchicine treatment enhances intranasal HIV antigen expression and mucosal humoral responses

Advances in vaccinia virus-based vaccine vectors, with applications in flavivirus vaccine development

Historically, virulent variola virus infection caused hundreds of millions of deaths. The smallpox pandemic in human beings has spread for centuries until the advent of the attenuated vaccinia virus (VV) vaccine, which played a crucial role in eradicating the deadly contagious disease. Decades of exploration and utilization have validated the attenuated VV as a promising vaccine vehicle against various lethal viruses. In this review, we focus on the advances in VV-based vaccine vector studies, including construction approaches of recombinant VV, the impact of VV-specific pre-existing immunity on subsequent VV-based vaccines, and antigen-specific immune responses. More specifically, the recombinant VV-based flaviviruses are intensively discussed. Based on the publication data, this review aims to provide valuable insights and guidance for future VV-based vaccine development.

Administration with Vaccinia Virus Encoding Canine Parvovirus 2 vp2 Elicits Systemic Immune Responses in Mice and Dogs

Canine parvovirus type 2 (CPV2) is a highly contagious cause of serious and often fatal disease in young dogs. Despite the widespread availability of attenuated vaccines, safer, more stable, and more effective CPV2 vaccine candidates are still under exploration. Vaccinia virus (VV) has already been proved to be a safe, stable, and effective vaccine vector. In this study, we generated a VV-based CPV2 vaccine candidate (VV_-CPV-VP2) and then evaluated its immunogenicity in mice and dogs. The exogenous vp2 gene of CPV2, which replaced the major virulence gene hemagglutinin (ha) of VV, expressed efficiently and stably in vitro. Subsequently, intramuscular immunization of mice induced robust and lasting systemic immune responses, including neutralizing antibody against both CPV2a and CPV2b, and CPV2-VP2-specific interferon gamma (IFN-γ) secreting T cell. In addition, administration with a high-dose of VV_-CPV-VP2 did not cause significant side effects for mice, thus indicating marked safety of this vaccine candidate. Most importantly, a single-dose vaccination of VV_-CPV2-VP2 elicited substantial antibody responses and provided comparable protection for dogs with attenuated CPV2 vaccine. Collectively, this study demonstrated that VV_-CPV2-VP2 could be used as a promising vaccine candidate preventing CPV2 from infection for dogs.

Intranasal immunization with recombinant Vaccinia virus Tiantan harboring Zaire Ebola virus gp elicited systemic and mucosal neutralizing antibody in mice

Accumulating literature revealed that human mucosa was likely one of the important routes for EBOV attachment and further infection. Therefore inducing effective mucosal immune responses play key role in preventing the virus infection. Vaccinia virus Tiantan strain (VV) was a remarkably attenuated poxvirus, which has been broadly exploited as a multifunctional vector during the development of genetically recombinant vaccine and cancer therapeutic agent. In this study, we generated a recombinant VV harboring EBOV gp (VV-_Egp) that was used to immunize mice, followed by assessing immune responses, particularly the mucosal immune responses to EBOV GP. A stable and further attenuated VV-_Egp, in which the VV ha gene was replaced with the EBOV gp, was generated. In BALB/c mouse model, intranasal immunization with VV-_Egp elicited robust humoral and cellular immune responses, including high level of neutralizing serum IgG and IgA against EBOV, and a large amount of GP-specific IFN-γ secreting lymphocytes. More importantly, EBOV GP-specific neutralizing secreted IgA (sIgA) in nasal wash and both sIgA and IgG in vaginal wash were induced. In summary, immunization with a safe and stable recombinant VV carrying a single EBOV gp conferred robust systemic immune response and mucosal neutralizing antibodies, indicating that the recombinant virus could be utilized as a viral vector for plug-and-play universal platform in mucosal vaccine development.

Labeling and Single-Particle-Tracking-Based Entry Mechanism Study of Vaccinia Virus from the Tiantan Strain

Entry is the first and critical step of viral infection, while the entry mechanisms of many viruses are still unclear due to the lack of efficient technology. In this report, by taking advantage of the single-virion fluorescence tracking technique and simultaneous dual-labeling methods for viruses we developed, the entry pathway of vaccinia virus from tiantan strain (VACV-TT) was studied in real-time. By combining with the technologies of virology and cell biology, we found that VACV-TT moved toward the Vero cell body along the filopodia induced by the virions interaction, and then, they were internalized through macropinocytosis, which was an actin-, ATP-dependent but clathrin-, caveolin-independent endocytosis. These results are of significant importance for VACV-TT-based vaccine vectors and oncolytic virus study.

Second-generation Flagellin-rPAc Fusion Protein, KFD2-rPAc, Shows High Protective Efficacy against Dental Caries with Low Potential Side Effects

Dental caries is one of the most common global chronic diseases affecting all ages of the population; thus a vaccine against caries is urgently needed. Our previous studies demonstrated that a fusion protein, KF-rPAc, in which rPAc of S. mutans is directly fused to the C-terminal of E. coli-derived flagellin (KF), could confer high prophylactic and therapeutic efficiency against caries. However, possible side effects, including the high antigenicity of flagellin and possible inflammatory injury induced by flagellin, may restrict its clinical usage. Here, we produced a second-generation flagellin-rPAc fusion protein, KFD2-rPAc, by replacing the main antigenicity region domains D2 and D3 of KF with rPAc. Compared with KF-rPAc, KFD2-rPAc has lower TLR5 agonist efficacy and induces fewer systemic inflammatory responses in mice. After intranasal immunization, KFD2-rPAc induces significantly lower flagellin-specific antibody responses but a comparable level of rPAc-specific antibody responses in mice. More importantly, in rat challenge models, KFD2-rPAc induces a robust rPAc-specific IgA response, and confers efficient prophylactic and therapeutic efficiency against caries as does KF-rPAc, while the flagellin-specific antibody responses are highly reduced. In conclusion, low side effects and high protective efficiency against caries makes the second-generation flagellin-rPAc fusion protein, KFD2-rPAc, a promising vaccine candidate against caries.

Spectral analysis and slow spreading dynamics on complex networks

The susceptible-infected-susceptible (SIS) model is one of the simplest memoryless systems for describing information or epidemic spreading phenomena with competing creation and spontaneous annihilation reactions. The effect of quenched disorder on the dynamical behavior has recently been compared to quenched mean-field (QMF) approximations in scale-free networks. QMF can take into account topological heterogeneity and clustering effects of the activity in the steady state by spectral decomposition analysis of the adjacency matrix. Therefore, it can provide predictions on possible rare-region effects, thus on the occurrence of slow dynamics. I compare QMF results of SIS with simulations on various large dimensional graphs. In particular, I show that for Erdős-Rényi graphs this method predicts correctly the occurrence of rare-region effects. It also provides a good estimate for the epidemic threshold in case of percolating graphs. Griffiths Phases emerge if the graph is fragmented or if we apply a strong, exponentially suppressing weighting scheme on the edges. The latter model describes the connection time distributions in the face-to-face experiments. In case of a generalized Barabási-Albert type of network with aging connections, strong rare-region effects and numerical evidence for Griffiths Phase dynamics are shown. The dynamical simulation results agree well with the predictions of the spectral analysis applied for the weighted adjacency matrices.

Deletion of C7L and K1L genes leads to significantly decreased virulence of recombinant vaccinia virus TianTan

The vaccinia virus TianTan (VTT) has been modified as an HIV vaccine vector in China and has shown excellent performance in immunogenicity and safety. However, its adverse effects in immunosuppressed individuals warrant the search for a safer vector in the following clinic trails. In this study, we deleted the C7L and K1L genes of VTT and constructed six recombinant vaccinia strains VTT△C7L, VTT△K1L, VTT△C7LK1L, VTKgpe△C7L, VTKgpe△K1L and VTT△C7LK1L-gag. The pathogenicity and immunogenicity of these recombinants were evaluated in mouse and rabbit models. Comparing to parental VTT, VTT△C7L and VTT△K1L showed significantly decreased replication capability in CEF, Vero, BHK-21 and HeLa cell lines. In particular, replication of VTT△C7LK1L decreased more than 10-fold in all four cell lines. The virulence of all these mutants were decreased in BALB/c mouse and rabbit models; VTT△C7LK1L once again showed the greatest attenuation, having resulted in no evident damage in mice and erythema of only 0.4 cm diameter in rabbits, compared to 1.48 cm for VTT. VTKgpe△C7L, VTKgpe△K1L and VTT△C7LK1L-gag elicited as strong cellular and humoral responses against HIV genes as did VTKgpe, while humoral immune response against the vaccinia itself was reduced by 4-8-fold. These data show that deletion of C7L and K1L genes leads to significantly decreased virulence without compromising animal host immunogenicity, and may thus be key to creating a more safe and effective HIV vaccine vector.

Enveloped virus labeling via both intrinsic biosynthesis and metabolic incorporation of phospholipids in host cells

An alternative method for labeling fully replicative enveloped viruses was developed, in which both the biosynthesis and metabolic incorporation of phospholipids in host cells were simultaneously utilized to introduce an azide group to the envelope of the vaccinia virus by taking advantage of the host-derived lipid membrane formation mechanism. Such an azide group could be subsequently used to fluorescently label the envelope of the virus via a bioorthogonal reaction. Furthermore, simultaneous dual-labeling of the virus through the virus replication was realized skillfully by coupling this envelope labeling strategy with "replication-intercalation labeling" of viral nucleic acid. For the first time, it is by natural propagation of the virus in its host cells in the presence of fluorophores that simultaneous dual-labeling of living viruses can be mildly realized with high efficiency in facile and mild conditions.

Antigen replacement of domains D2 and D3 in flagellin promotes mucosal IgA production and attenuates flagellin-induced inflammatory response after intranasal immunization

Targeting early infection in mucosal sites is one of the primary goals for mucosal vaccines so as to prevent pathogen mucosal transmission and infection. The TLR5 agonist flagellin was deemed to be a mucosal adjuvant candidate for clinical usage. However, the high antigenicity of flagellin and the possible inflammatory injury induced by flagellin might restrict its clinical usage. Here HIV-1 p24 protein was selected as an antigen model and we replaced the main antigenicity region domains D2 and D3 of non-pathogenic E.coli-derived flagellin (KF). The derived soluble protein KFD-p24 3D was then compared with KF-p24, which fused p24 directly to the C-terminal of KF. In vitro and ex vivo experiments showed that KFD-p24 3D has lower TLR5 agonist efficacy and less immunocyte-activating efficacy. Interestingly, the production of KF- specific antibody was highly reduced, and KFD-p24 3D induced IgA-biased antibody responses in mucosal sites. Moreover, KFD-p24 3D induced far fewer systemic inflammatory responses and abrogated detectable inflammatory side effects on mice, even at the high dose. The properties of enhanced IgA generation and attenuated inflammatory responses broaden the safe-dose range of KFD-p24 3D flagellin, creating a potentially promising mucosal adjuvant.

A mild and reliable method to label enveloped virus with quantum dots by copper-free click chemistry

Real-time tracking of the dynamic process of virus invasion is crucial to understanding the infection mechanism. For successful tracking, efficient labeling methods are indispensable. In this paper, we report a mild and reliable method for labeling viruses, especially with regard to easily disabled enveloped viruses. The copper-free click chemistry has been used to label enveloped viruses with quantum dots (QDs) by linking virions modified with azide to the QDs derived with dibenzocyclooctynes (DBCO). Both vaccinia virus (VACV) and avian influenza A virus (H9N2) can be specifically and rapidly labeled under mild conditions, with a labeling efficiency of more than 80%. The labeled virions were of intact infectivity, and their fluorescence was strong enough to realize single-virion tracking. Compared to previously reported methods, our method is less destructive, reliable, and universal, without specific requirements for the type and structure of viruses to be labeled, which has laid the foundation for long-term dynamic visualization of virus infection process.

Anti-HIV-1 activity of a new scorpion venom peptide derivative Kn2-7

For over 30 years, HIV/AIDS has wreaked havoc in the world. In the absence of an effective vaccine for HIV, development of new anti-HIV agents is urgently needed. We previously identified the antiviral activities of the scorpion-venom-peptide-derived mucroporin-M1 for three RNA viruses (measles viruses, SARS-CoV, and H5N1). In this investigation, a panel of scorpion venom peptides and their derivatives were designed and chosen for assessment of their anti-HIV activities. A new scorpion venom peptide derivative Kn2-7 was identified as the most potent anti-HIV-1 peptide by screening assays with an EC₅₀ value of 2.76 µg/ml (1.65 µM) and showed low cytotoxicity to host cells with a selective index (SI) of 13.93. Kn2-7 could inhibit all members of a standard reference panel of HIV-1 subtype B pseudotyped virus (PV) with CCR5-tropic and CXCR4-tropic NL4-3 PV strain. Furthermore, it also inhibited a CXCR4-tropic replication-competent strain of HIV-1 subtype B virus. Binding assay of Kn2-7 to HIV-1 PV by Octet Red system suggested the anti-HIV-1 activity was correlated with a direct interaction between Kn2-7 and HIV-1 envelope. These results demonstrated that peptide Kn2-7 could inhibit HIV-1 by direct interaction with viral particle and may become a promising candidate compound for further development of microbicide against HIV-1.

Attenuation of vaccinia Tian Tan strain by removal of viral TC7L-TK2L and TA35R genes

Vaccinia Tian Tan (VTT) was attenuated by deletion of the TC7L-TK2L and TA35R genes to generate MVTT3. The mutant was generated by replacing the open reading frames by a gene encoding enhanced green fluorescent protein (EGFP) flanked by loxP sites. Viruses expressing EGFP were then screened for and purified by serial plaque formation. In a second step the marker EGFP gene was removed by transfecting cells with a plasmid encoding cre recombinase and selecting for viruses that had lost the EGFP phenotype. The MVTT3 mutant was shown to be avirulent and immunogenic. These results support the conclusion that TC7L-TK2L and TA35R deletion mutants can be used as safe viral vectors or as platform for vaccines.