Joint production of prime/boost pairs of Fowlpox Virus and Modified Vaccinia Ankara recombinants carrying the same transgene

Time- and cost-effective production of untagged recombinant MVA by flow virometry and direct virus sorting

BACKGROUND

Recombinant MVAs (rMVAs) are widely used both in basic and clinical research. Our previously developed Red-to-Green Gene Swapping Method (RGGSM), a cytometry-based Cell-Sorting protocol, revolves around the transient expression of a green fluorescent cytoplasmic marker, to subsequently obtain purified untagged rMVA upon loss of that marker by site-specific recombination. The standard RGSSM is quite costly in terms of bench work, reagents, and Sorting Facility fees. Although faster than other methods to obtain recombinant MVAs, the standard RGSSM still is time-consuming, taking at least 25 days to yield the final product.

METHODS

The direct sorting of fluorescent virions is made amenable by the marker HAG, a flu hemagglutinin/EGFP fusion protein, integrated into the external envelope of extracellular enveloped virions (EEVs). Fluorescent EEVs-containing supernatants of infected cultures are used instead of purified virus. Direct Virus-Sorting was performed on BD FACSAria Fusion cell sorter equipped with 4 lasers and a 100-mm nozzle, with 20 psi pressure and a minimal flow rate, validated using Megamix beads.

RESULTS

Upon infection of cells with recombinant EEVs, at the first sorting step virions that contain HAG are harvested and cloned, while the second sorting step yields EEVs that have lost HAG, allowing to clone untagged rMVA. Because only virion-containing supernatants are used, no virus purification steps and fewer sortings are necessary. Therefore, the final untagged rMVA product can be obtained in a mere 8 days.

CONCLUSIONS

Altogether, we report that the original RGSSM has been markedly improved in terms of time- and cost efficiency by substituting Cell-Sorting with direct Virus-Sorting from the supernatants of infected cells. The improved virometry-based RGGSM may find wide applicability, considering that rMVAs hold great promise to serve as personalized vaccines for therapeutic intervention against cancer and various types of infectious diseases.

Strategies to obtain multiple recombinant modified vaccinia Ankara vectors. Applications to influenza vaccines

As a vaccination vector, MVA has been widely investigated both in animal models and humans. The construction of recombinant MVA (rMVA) relies on homologous recombination between an acceptor virus and a donor plasmid in infected/transfected permissive cells. Our construction strategy "Red-to-Green gene swapping" - based on the exchange of two fluorescent markers within the flanking regions of MVA deletion ΔIII, coupled to fluorescence activated cell sorting - is here extended to a second insertion site, within the flanking regions of MVA deletion ΔVI. Exploiting this strategy, both double and triple rMVA were constructed, expressing as transgenes the influenza A proteins HA, NP, M1, and PB1. Upon validation of the harbored transgenes co-expression, double and triple recombinants rMVA(ΔIII)-NP-P2A-M1 and rMVA(ΔIII)-NP-P2A-M1-(ΔVI)-PB1 were assayed for in vivo immunogenicity and protection against lethal challenge. In vivo responses were identical to those obtained with the reported combinations of single recombinants, supporting the feasibility and reliability of the present improvement and the extension of Red-to-Green gene swapping to insertion sites other than ΔIII.

Efficacy and immunogenicity of recombinant swinepox virus expressing the truncated S protein of a novel isolate of porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) causes significant loss to the swine industry. The emergence of novel PEDV strains in recent years has decreased the effectiveness of PEDV vaccines. We have developed a live recombinant vaccine, a swinepox virus vector that expresses a truncated S protein (rSPV-St) from a recent PEDV strain, SQ2014, and evaluated its immunogenicity and effectiveness in a swine model. Vaccination of swine with rSPV-St elicited a robust antibody response specific for the homologous PEDV SQ2014. Serum IgA titers in rSPV-St-vaccinated animals were significantly higher than in those immunized with inactivated vaccines. The effectiveness of antibodies induced by the rSPV-St vaccine in protection against PEDV was tested in a passive-transfer model in which piglets were challenged with the homologous virus SQ2014 and the heterologous strain CV777. When challenged with the homologous virus, sera from rSPV-St vaccination provided complete protection. However, sera from rSPV-St vaccination did not provide any protection against the heterologous virus challenge. Amino acid sequence differences in the S proteins of the two viruses were identified within neutralizing epitopes, which might have contributed to the divergent clinical results. Our data suggest that rSPV-St is potentially an effective vaccine against infection with emerging PEDV strains.

Protection of mice against the highly pathogenic VVIHD-J by DNA and fowlpox recombinant vaccines, administered by electroporation and intranasal routes, correlates with serum neutralizing activity

The control of smallpox was achieved using live vaccinia virus (VV) vaccine, which successfully eradicated the disease worldwide. As the variola virus no longer exists as a natural infection agent, mass vaccination was discontinued after 1980. However, emergence of smallpox outbreaks caused by accidental or deliberate release of variola virus has stimulated new research for second-generation vaccine development based on attenuated VV strains. Considering the closely related animal poxviruses that also arise as zoonoses, and the increasing number of unvaccinated or immunocompromised people, a safer and more effective vaccine is still required. With this aim, new vectors based on avian poxviruses that cannot replicate in mammals should improve the safety of conventional vaccines, and protect from zoonotic orthopoxvirus diseases, such as cowpox and monkeypox. In this study, DNA and fowlpox (FP) recombinants that expressed the VV L1R, A27L, A33R, and B5R genes were generated (4DNAmix, 4FPmix, respectively) and tested in mice using novel administration routes. Mice were primed with 4DNAmix by electroporation, and boosted with 4FPmix applied intranasally. The lethal VVIHD-J strain was then administered by intranasal challenge. All of the mice receiving 4DNAmix followed by 4FPmix, and 20% of the mice immunized only with 4FPmix, were protected. The induction of specific humoral and cellular immune responses directly correlated with this protection. In particular, higher anti-A27 antibodies and IFNγ-producing T lymphocytes were measured in the blood and spleen of the protected mice, as compared to controls. VVIHD-J neutralizing antibodies in sera from the protected mice suggest that the prime/boost vaccination regimen with 4DNAmix plus 4FPmix may be an effective and safe mode to induce protection against smallpox and poxvirus zoonotic infections. The electroporation/intranasal administration routes contributed to effective immune responses and mouse survival.

Preclinical development of HIvax: Human survivin highly immunogenic vaccines

Our previous work involved the development of a recombinant fowlpox virus encoding survivin (FP-surv) vaccine that was evaluated for efficacy in mesothelioma mouse models. Results showed that FP-surv vaccination generated significant immune responses, which led to delayed tumor growth and improved animal survival. We have extended those previous findings in the current study, which involves the pre-clinical development of an optimized version of FP-surv designed for human immunization (HIvax). Survivin-derived peptides for the most common haplotypes in the human population were identified and their immunogenicity confirmed in co-culture experiments using dendritic cells and T cells isolated from healthy donors. Peptides confirmed to induce CD8(+) and CD4(+) T cells activation in humans were then included in 2 transgenes optimized for presentation of processed peptides on MHC-I (HIvax1) and MHC-II (HIvax2). Fowlpox vectors expressing the HIvax transgenes were then generated and their efficacy was evaluated with subsequent co-culture experiments to measure interferon-γ and granzyme B secretion. In these experiments, both antigen specific CD4(+) and CD8(+) T cells were activated by HIvax vaccines with resultant cytotoxic activity against survivin-overexpressing mesothelioma cancer cells. These results provide a rationale for clinical testing of HIvax1 and HIvax2 vaccines in patients with survivin-expressing cancers.

Efficacy and immunogenicity of recombinant swinepox virus expressing the A epitope of the TGEV S protein

To explore the possibility of developing a vaccine against transmissible gastroenteritis virus (TGEV) infection, a recombinant swinepox virus (rSPV-SA) expressing a TGEV protective antigen has been constructed. Immune responses and protection efficacy of the vaccination vector were assessed in both mice and pig models. An indirect ELISA assay suggested that when mice were vaccinated with rSPV-SA, the level of IgG against TGEV was enhanced dramatically. The cytokine assays were employed and the results indicated that both the Th1-type and Th2-type cytokine levels raised after vaccination with rSPV-SA in mice models. Results from the passive immunity protection test of new born piglets demonstrated that the recombinant live-vector vaccine, rSPV-SA, could 100% protect piglets from the SPV infection, and there was no significant clinical symptom in the rSPV-SA treatment group during this experiment. The data suggest that the novel recombinant swinepox virus is a potential vaccine against TGEV infection.

Against the clock towards new Ebola virus therapies

Since the end of 2013, West Africa has been suffering the largest Ebola virus (EBOV) outbreak in recorded history. The lack of health care infrastructure in the affected countries, as well as a concentration of infected cases in the most populated areas allowed the virus to spread with no control during the first months of the outbreak. With no specific treatment available to combat EBOV infection and its associated disease, an extraordinary worldwide effort was made to confront the severity of the situation and to establish new therapeutic strategies that would lead to better and faster control and eradicate the outbreak. In the last two years, several candidate therapies and potential vaccines against EBOV have arisen and human clinical trials are ongoing, in hopes of starting their deployment in the affected countries. This article reviews the current candidate therapies against EBOV, their stage of development and future prospects in battling EBOV outbreaks.

Systemically administered DNA and fowlpox recombinants expressing four vaccinia virus genes although immunogenic do not protect mice against the highly pathogenic IHD-J vaccinia strain

The first-generation smallpox vaccine was based on live vaccinia virus (VV) and it successfully eradicated the disease worldwide. Therefore, it was not administered any more after 1980, as smallpox no longer existed as a natural infection. However, emerging threats by terrorist organisations has prompted new programmes for second-generation vaccine development based on attenuated VV strains, which have been shown to cause rare but serious adverse events in immunocompromised patients. Considering the closely related animal poxviruses that might also be used as bioweapons, and the increasing number of unvaccinated young people and AIDS-affected immunocompromised subjects, a safer and more effective smallpox vaccine is still required. New avipoxvirus-based vectors should improve the safety of conventional vaccines, and protect from newly emerging zoonotic orthopoxvirus diseases and from the threat of deliberate release of variola or monkeypox virus in a bioterrorist attack. In this study, DNA and fowlpox recombinants expressing the L1R, A27L, A33R and B5R genes were constructed and evaluated in a pre-clinical trial in mouse, following six prime/boost immunisation regimens, to compare their immunogenicity and protective efficacy against a challenge with the lethal VV IHD-J strain. Although higher numbers of VV-specific IFNγ-producing T lymphocytes were observed in the protected mice, the cytotoxic T-lymphocyte response and the presence of neutralising antibodies did not always correlate with protection. In spite of previous successful results in mice, rabbits and monkeys, where SIV/HIV transgenes were expressed by the fowlpox vector, the immune response elicited by these recombinants was low, and most of the mice were not protected.

Fowlpox-based survivin vaccination for malignant mesothelioma therapy

Survivin protein is an attractive candidate for cancer immunotherapy since it is abundantly expressed in most common human cancers and mostly absent in normal adult tissues. Malignant mesothelioma (MM) is a deadly cancer associated with asbestos or erionite exposure for which no successful therapies are currently available. In this study, we evaluated the therapeutic efficacy of a novel survivin-based vaccine by subcutaneous or intraperitoneum injection of BALB/c mice with murine fiber-induced MM tumor cells followed by vaccination with recombinant Fowlpox virus replicons encoding survivin. Vaccination generated significant immune responses in both models, leading to delayed tumor growth and improved animal survival. Flow cytometry and immunofluorescence analyses of tumors from vaccinated mice showed CD8(+) T-cell infiltration, and real-time PCR demonstrated increased mRNA and protein levels of immunostimulatory cytokines. Analyses of survivin peptide-pulsed spleen and lymph node cells from vaccinated mice using ELISPOT and intracellular cytokine staining confirmed antigen-specific, interferon-γ-producing CD8(+) T-cell responses. In addition pentamer-based flow cytometry showed that vaccination generated survivin-specific CD8(+) T cells. Importantly, vaccination did not affect fertility or induce autoimmune abnormalities in mice. Our results demonstrate that vaccination with recombinant Fowlpox expressing survivin improves T-cell responses against aggressive MM tumors and may form the basis for promising clinical applications.

Immune responses and protective efficacy of a recombinant swinepox virus expressing HA1 against swine H1N1 influenza virus in mice and pigs

Swine influenza virus (SIV) is not only an important respiratory pathogen in pigs but also a potent threat to human health. Although immunization with recombinant poxviruses expressing protective antigens as vaccines has been widely used for against many infectious diseases, development of recombinant swinepox virus (rSPV) vector for the purpose has been less successful. Here, we report the construction of a recombinant swinepox virus (rSPV-HA1) expressing hemagglutinin (HA1) of H1N1 SIV. Immune responses and protection efficacy of the vaccination vector were evaluated in both the mouse model and the natural host: pig. Prime and boost inoculations of rSPV-HA1 yielded high levels of neutralization antibody against SIV and elicited potent H1N1 SIV-specific IFN-γ response from T-lymphocytes. Complete protection of pigs against H1N1 SIV challenge was observed. No pigs showed evident systemic and local reactions to the vaccine and no SIV shedding was detected from pigs vaccinated with rSPV-HA1 after challenge. Our data demonstrated that the recombinant swinepox virus encoding HA1 of SIV H1N1 may serve as a promising SIV vaccine for protection against SIV infection.