Modified Vaccinia Virus Ankara Research Articles

OX40L-expressing recombinant modified vaccinia virus Ankara induces potent antitumor immunity via reprogramming Tregs.

Effective depletion of immune suppressive regulatory T cells (Tregs) in the tumor microenvironment without triggering systemic autoimmunity is an important strategy for cancer immunotherapy. Modified vaccinia virus Ankara (MVA) is a highly attenuated, non-replicative vaccinia virus with a long history of human use. Here, we report rational engineering of an immune-activating recombinant MVA (rMVA, MVA∆E5R-Flt3L-OX40L) with deletion of the vaccinia E5R gene (encoding an inhibitor of the DNA sensor cyclic GMP-AMP synthase, cGAS) and expression of two membrane-anchored transgenes, Flt3L and OX40L. Intratumoral (IT) delivery of rMVA (MVA∆E5R-Flt3L-OX40L) generates potent antitumor immunity, dependent on CD8+ T cells, the cGAS/STING-mediated cytosolic DNA-sensing pathway, and type I IFN signaling. Remarkably, IT rMVA (MVA∆E5R-Flt3L-OX40L) depletes OX40hi regulatory T cells via OX40L/OX40 interaction and IFNAR signaling. Single-cell RNA-seq analyses of tumors treated with rMVA showed the depletion of OX40hiCCR8hi Tregs and expansion of IFN-responsive Tregs. Taken together, our study provides a proof-of-concept for depleting and reprogramming intratumoral Tregs via an immune-activating rMVA.

A recombinant Modified Vaccinia virus Ankara expressing prME of tick-borne encephalitis virus affords mice full protection against TBEV infection.

Tick-borne encephalitis virus (TBEV) is an important human pathogen that can cause a serious disease involving the central nervous system (tick-borne encephalitis, TBE). Although approved inactivated vaccines are available, the number of TBE cases is rising, and breakthrough infections in fully vaccinated subjects have been reported in recent years. In the present study, we generated and characterized a recombinant Modified Vaccinia virus Ankara (MVA) for the delivery of the pre-membrane (prM) and envelope (E) proteins of TBEV (MVA-prME). MVA-prME was tested in mice in comparison with a licensed vaccine FSME-IMMUN® and proved to be highly immunogenic and afforded full protection against challenge infection with TBEV. Our data indicate that MVA-prME holds promise as an improved next-generation vaccine for the prevention of TBE.

1238 Local differentiation of Tcf7+ stem-like CD8+ T cells into activating effector CD8+ T cells is critical for antitumor effects induced by intratumoral injection of immunogenic recombinant modified vaccinia virus ankara

1238 Local differentiation of Tcf7+ stem-like CD8+ T cells into activating effector CD8+ T cells is critical for antitumor effects induced by intratumoral injection of immunogenic recombinant modified vaccinia virus ankara

Abstract LB223: Intratumoral administration of modified vaccinia Ankara expressing a tumor associated antigen and the costimulatory molecules IL-12 and 4-1BBL induces potent systemic long-term immune responses against murine tumors

Abstract In the last decade, immunotherapy has revolutionized cancer treatment. However, the lack of potent therapy-induced immune responses against solid tumors due to the immune-suppressive tumor microenvironment (TME) is still a major drawback. One approach to reprogram TME is virotherapy, which can target tumors via destruction of infected tumor cells as well as activating immune cell populations in the TME. A versatile and safe tool for virotherapy is modified vaccinia virus Ankara (MVA), which has already been approved by the FDA as a non-replicating vaccine against smallpox and monkeypox and is also in clinical trials against other infectious diseases and cancer. In the current study, we deciphered the anti-tumorigenic effect of a novel MVA vector encoding a tumor associated antigen (TAA) and the costimulatory molecules IL-12 and 4-1BBL, called MVA-TAA-4-1BBL-IL12. We could show that repetitive intratumoral (IT) injection of MVA-TAA-4-1BBL-IL12 resulted in strong tumor growth control, shrinkage and/or complete elimination of tumors and induction of tumor-specific CD8 T cell response. Furthermore, MVA-TAA-4-1BBL-IL12 treatment promoted a systemic anti-tumor immune response not only against the treated tumor but also untreated, distant tumors. Importantly, local virotherapy also resulted in the generation of tumor-specific memory response, which protected mice against local recurrence after rechallenge. As a conclusion, our findings show that MVA-TAA-4-1BBL-IL12 IT treatment induces an effective anti-tumorigenic immune response in different solid tumor models, which gives rise to long-term protection against cancer recurrence. Citation Format: Cigdem Atay Langbein, Raphael Giessel, Mahmad Ismail Housni, Kerstin Lämmermann, Barbara Bathke, André Riedl, Jürgen Hausmann, Markus Kalla, Paul Chaplin, Hubertus Hochrein, José Medina-Echeverz, Maria Hinterberger. Intratumoral administration of modified vaccinia Ankara expressing a tumor associated antigen and the costimulatory molecules IL-12 and 4-1BBL induces potent systemic long-term immune responses against murine tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB223.

Abstract LB205: Feasibility and immunogenicity of adjuvant TG4050, a patient tailored cancer vaccine in head and neck and ovarian cancer

Abstract Background: Head and Neck (HNSCC) and Ovarian cancer (OC) are two indications for which immunotherapy had limited impact so far. Current treatments achieve high rates of initial success through surgery and adjuvant chemo/radiotherapy, but patients (pts) remain at high risk of relapse in both indications. Immune stimulation using a vaccine is a promising strategy to a clinically meaningful improvement. Herein we report phase I data of TG4050, a vaccine engineered to carry a pt tailored antigen payload, in pts with HNSCC (NCT04183166) or OC (NCT03839524). Methods: Tumor specific variants are identified using next generation sequencing of tumor and normal samples whereby immune relevant mutations are predicted using a machine learning algorithm factoring in parameters known to affect immunogenicity including MHC binding, level of expression, prevalence across clones, and antigen processing. DNA sequences of the mutations of interest, typically 30 per pt, are cloned in a viral vector (Modified Vaccinia Virus Ankara). Following curative intent treatment, HNSCC pts in complete remission were randomized to an immediate vaccination arm to receive weekly doses of TG4050 for 6 weeks followed by a maintenance period of one dose every 3 weeks for up to 20 doses or to a delayed vaccination arm where the same vaccination regimen is initiated at relapse. OC pts received the vaccine upon onset of signs of relapse. PBMC were collected at Baseline and after 6 doses of vaccine. Primary endpoint was vaccine safety and secondary endpoints included feasibility, immunogenicity. Results: 18 pts received TG4050 (5 OC and 13 HNSCC) treatment with no related grade ≥ 3 adverse events. Tumor mutational burden (TMB) was on average 3.00±0.98 and 2.43±0.69 mutations per megabase for HNSCC and OC respectively. Despite this low TMB, all pts had sufficient cancer specific neoantigens to design a vaccine. Ex-vivo ELISPOT was completed for 7 pts at the time of submission. A mean of 44% of selected mutations were associated with a reactive T cell responses either spontaneously or after TG4050 stimulation ranging from 6 to 22 mutations per pt. Vaccination induced a stimulation of T cell response in all tested pts on an average of 10 targeted mutations, induction of de novo responses was seen in all 7 tested pts and amplification of pre-existing response in 6/7 pts. None of the evaluable HNSCC pts receiving TG4050 immediately after first line treatment had relapse after a median follow-up of 7 months while 2 pts had relapse in the delayed vaccination arm. Furthermore, in OC pts treated at early relapse, TG4050 has normalized disease markers (ctDNA and/or CA-125) for 2/4 pts with stable disease for 9 and 11 months. Conclusion: TG4050 treatment is feasible and immunogenic in pts with low to moderate TMB. It is effective in inducing T cell responses and first signs of antitumor activity are encouraging for the continuation of development. Citation Format: Ana Lalanne, Camille Jamet, Christian H. Ottensmeier, Jean-Pierre Delord, Christophe Le Tourneau, Matthew S. Block, Gerardo Colon-Otero, Keith L. Knutson, Annette Tavernaro, Gisele Lacoste, Benoit Grellier, Xavier Noiriel, Thierry Huss, Bernard Burtin, Yoshiko Yamashita, Kousuke Onoue, Kazuhide Onoguchi, Brandon Malone, Olivier Lantz, Oliver Baker, Naoko Yamagata, Yuki Tanaka, Eric Quemeneur, Maud Brandely, Kaidre Bendjama. Feasibility and immunogenicity of adjuvant TG4050, a patient tailored cancer vaccine in head and neck and ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB205.

Abstract CT045: A randomized phase II trial of TG4001 plus avelumab versus avelumab alone in recurrent/metastatic (R/M) human papilloma virus (HPV)-16 positive anogenital cancers

Abstract Background: Immune checkpoint inhibitors targeting the PD1/PD-L1 axis have made a breakthrough in advanced solid tumors, leading to improved overall survival (OS) in several cancer types. However, only a minority of patients experience durable responses, requiring further development of anti-tumoral immunotherapies to overcome tumor immune escape. We hypothesized that priming the immune system with TG4001, a vaccine using the highly attenuated Modified Vaccinia virus Ankara as vector expressing the HPV16 E6 and E7 proteins (rendered non-oncogenic) and interleukin-2, would increase the clinical benefit associated with PD-L1 blockade in HPV16+ cancer patients. In the single-arm part of the trial evaluating the combination of TG4001 and avelumab in terms of response rate, the overall response rate (ORR) was 22%. Presence of liver metastases had a profound impact on outcome in terms of ORR and Progression Free Survival (PFS). In patients (pts) without liver metastases an ORR of 32% was observed versus 0% in pts with liver metastases, warranting further development of this combination in this patient population (SITC 2020, Abstract ID 793). Methods: We have designed a randomized open-label two-arms trial evaluating the efficacy of the combination of TG4001 and avelumab versus avelumab alone (NCT03260023). Eligible pts have R/M HPV-16 positive anogenital cancer including cervical, vulvar, vaginal, penile, and anal cancers with no more than one prior line of chemotherapy for R/M disease and no previous exposure to cancer immunotherapy. HPV-16 positivity is determined in a central laboratory. Patients are randomly assigned 1:1 to receive either TG4001 plus avelumab or avelumab alone. Randomization is stratified by primary tumor type (cervical, anal, genital). TG4001 is administered subcutaneously (SC) at 5 × 107 plaque forming units (pfu) Q1w for 5 weeks, Q2w until month 6 and Q12w until progressive disease and avelumab intravenously (IV) at 800 mg Q2w until progressive disease. A total of up to 140 pts are currently being recruited into two cohorts (A and B) in France, Spain, and USA. For Cohort A, consisting of pts without liver metastases at Baseline (BL), a 2-stage sample size adjustment design is used with PFS by RECIST 1.1 as primary endpoint. Plans are to accrue 120 patients following Interim Analysis and Independent Data Monitoring Committee (IDMC) review. Cohort B recruits pts with liver metastases at BL. To be eligible, hepatic disease is restricted in terms of extent and number of lesions. A total of 20 pts will be recruited and analyzed for the percentage of early progressors. Secondary endpoints include overall survival, objective response rate according to RECIST1.1, duration of response, disease control rate. Exploratory endpoints comprise analyses of blood-based parameters and tumor-based proteins and RNA expression and their impact on clinical outcomes. Citation Format: Christophe Le Tourneau, Frédéric Rolland, Amaury Daste, Philippe Cassier, Sébastien Salas, Luis Manso Sánchez, Gerardo Colon-Otero, Lauriane Eberst, Olivier Lantz, Ana Lalanne, Annette Tavernaro, Hakim Makhloufi, Kaïdre Bendjama, Maud Brandely, Jean-Pierre Delord. A randomized phase II trial of TG4001 plus avelumab versus avelumab alone in recurrent/metastatic (R/M) human papilloma virus (HPV)-16 positive anogenital cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT045.

Сравнение онколитической активности рекомбинантных штаммов вируса осповакцины LIVP-RFP и MVA-RFP в отношении солидных опухолей

Among oncolytic viruses, modified vaccinia virus Ankara (MVA), a highly attenuated vaccinia virus (VV) is a well-studied variant with promising results in preclinical and clinical trials. The Lister VV strain from the Moscow Institute of Viral Preparations (LIVP) has been studied to a lesser extent than MVA and has a different oncolytic property from MVA. The aim of this work was to compare the oncolytic efficacy of LIVP and MVA strains against solid tumors. We developed recombinant variants LIVP-RFP and MVA-RFP; to enhance onco-selectivity thymidine kinase (TK) gene was inactivated by insertion of red fluorescent protein (RFP) gene to the TK locus. The replication kinetics and oncolytic activity of the obtained recombinant strains were evaluated in vitro and in vivo on tumor cell lines and mouse syngeneic tumor models of metastatic mouse 4T1 mammary adenocarcinoma, CT26 colon adenocarcinoma, and B16 melanoma. Both MVA-RFP and LIVP-RFP showed high replication efficiency in tumor cells and pronounced oncolytic activity against B16 melanoma and 4T1 breast adenocarcinoma allografts. In relation to 4T1, which is a model of triple negative human breast cancer, LIVP-RFP showed more than 50% increased cytotoxicity in in vitro tests compared to MVA-RFP, as well as a significant slowdown in the progression of 4T1 allografts and an increase in animal survival in experiments in vivo. Thus, the LIVP strain may be more promising than MVA as a platform for the development of recombinant oncolytic viruses for the breast cancer treatment.

Recombinant Modified Vaccinia Virus Ankara Expressing a Glycosylation Mutant of Dengue Virus NS1 Induces Specific Antibody and T-Cell Responses in Mice.

The four serotypes of dengue virus (DENV1-4) continue to pose a major public health threat. The first licenced dengue vaccine, which expresses the surface proteins of DENV1-4, has performed poorly in immunologically naïve individuals, sensitising them to antibody-enhanced dengue disease. DENV non-structural protein 1 (NS1) can directly induce vascular leakage, the hallmark of severe dengue disease, which is blocked by NS1-specific antibodies, making it an attractive target for vaccine development. However, the intrinsic ability of NS1 to trigger vascular leakage is a potential drawback of its use as a vaccine antigen. Here, we modified DENV2 NS1 by mutating an N-linked glycosylation site associated with NS1-induced endothelial hyperpermeability and used modified vaccinia virus Ankara (MVA) as a vector for its delivery. The resulting construct, rMVA-D2-NS1-N207Q, displayed high genetic stability and drove efficient secretion of NS1-N207Q from infected cells. Secreted NS1-N207Q was composed of dimers and lacked N-linked glycosylation at position 207. Prime-boost immunisation of C57BL/6J mice induced high levels of NS1-specific antibodies binding various conformations of NS1 and elicited NS1-specific CD4+ T-cell responses. Our findings support rMVA-D2-NS1-N207Q as a promising and potentially safer alternative to existing NS1-based vaccine candidates, warranting further pre-clinical testing in a relevant mouse model of DENV infection.

Monkeypox Virus Cross-Neutralizing Antibodies in Clinical Trial Participants Vaccinated With Modified Vaccinia Virus Ankara Encoding Middle East Respiratory Syndrome-Coronavirus Spike Protein.

Modified vaccinia virus Ankara (MVA) is used as a vaccine against monkeypox virus and as a viral vaccine vector. MVA-MERS-S is a vaccine candidate against Middle East respiratory syndrome (MERS)-associated coronavirus. Here, we report that cross-reactive monkeypox virus neutralizing antibodies were detectable in only a single study participant after the first dose of MVA-MERS-S vaccine, in 3 of 10 after the second dose, and in 10 of 10 after the third dose.

ADCC: An underappreciated correlate of cross-protection against influenza?

In this short review, we summarized the results obtained with an assay to detect influenza virus-specific antibodies that mediate ADCC, which was developed and evaluated within the framework of the IMI-funded project "FLUCOP". HA-specific ADCC mediating antibodies were detected in serum samples from children and adults pre- and post-vaccination with monovalent, trivalent, or quadrivalent seasonal influenza vaccines, or following infection with H1N1pdm09 virus. Additionally, using chimeric influenza HA proteins, the presence of HA-stalk-specific ADCC mediating antibodies after vaccination and natural infection with H1N1pdm09 virus was demonstrated. With serum samples obtained from children that experienced a primary infection with an influenza B virus, we showed that primary infection induces HA-specific ADCC-mediating antibodies that cross-reacted with HA from influenza B viruses from the heterologous lineage. These cross-reactive antibodies were found to be directed to the HA stalk region. Antibodies directed to the influenza B virus HA head mediated low levels of ADCC. Finally, vaccination with a recombinant modified vaccinia virus Ankara expressing the HA gene of a clade 1 A(H5N1) highly pathogenic avian influenza virus led to the induction of ADCC-mediating antibodies, which cross-reacted with H5 viruses of antigenically distinct clades. Taken together, it is clear that virus-specific antibodies induced by infection or vaccination have immunological functionalities in addition to neutralization. These functionalities could contribute to protective immunity. The functional profiling of vaccine-induced antibodies may provide further insight into the effector functions of virus-specific antibodies and their contribution to virus-specific immunity.

Improved memory CD8 T cell response to delayed vaccine boost is associated with a distinct molecular signature.

Effective secondary response to antigen is a hallmark of immunological memory. However, the extent of memory CD8 T cell response to secondary boost varies at different times after a primary response. Considering the central role of memory CD8 T cells in long-lived protection against viral infections and tumors, a better understanding of the molecular mechanisms underlying the changing responsiveness of these cells to antigenic challenge would be beneficial. We examined here primed CD8 T cell response to boost in a BALB/c mouse model of intramuscular vaccination by priming with HIV-1 gag-encoding Chimpanzee adenovector, and boosting with HIV-1 gag-encoding Modified Vaccinia virus Ankara. We found that boost was more effective at day(d)100 than at d30 post-prime, as evaluated at d45 post-boost by multi-lymphoid organ assessment of gag-specific CD8 T cell frequency, CD62L-expression (as a guide to memory status) and in vivo killing. RNA-sequencing of splenic gag-primed CD8 T cells at d100 revealed a quiescent, but highly responsive signature, that trended toward a central memory (CD62L+) phenotype. Interestingly, gag-specific CD8 T cell frequency selectively diminished in the blood at d100, relative to the spleen, lymph nodes and bone marrow. These results open the possibility to modify prime/boost intervals to achieve an improved memory CD8 T cell secondary response.

Evaluation of the Effect of CD70 Co-Expression on CD8 T Cell Response in Protein-Prime MVA-Boost Vaccination in Mice.

Here, we investigate the potential of CD70 co-expression during viral vector boost vaccination to improve an antigen-specific T cell response. To determine the chance of activating antigen-specific T cells by CD70, we used the HBV core antigen as a model antigen in a heterologous protein-prime, Modified Vaccinia virus Ankara (MVA) boost vaccination scheme. Both the HBV core and a CD70 expression cassette were co-expressed upon delivery by an MVA vector under the same promoter linked by a P2A site. To compare immunogenicity with and without CD70 co-expression, HBV-naïve, C57BL/6 (wt) mice and HBV-transgenic mice were prime-vaccinated using recombinant HBV core antigen followed by the MVA vector boost. Co-expression of CD70 increased the number of vaccine-induced HBV core-specific CD8 T cells by >2-fold and improved their effector functions in HBV-naïve mice. In vaccinated HBV1.3tg mice, the number and functionality of HBV core-specific CD8 T cells was slightly increased upon CD70 co-expression in low-viremic, but not in high-viremic animals. CD70 co-expression did not impact liver damage as indicated by ALT levels in the serum, but increased the number of vaccine-induced, proliferative T cell clusters in the liver. Overall, this study indicates that orchestrated co-expression of CD70 and a vaccine antigen may be an interesting and safe means of enhancing antigen-specific CD8 T cell responses using vector-based vaccines, although in our study it was not sufficient to break immune tolerance.

Full protection from SARS-CoV-2 brain infection and damage in susceptible transgenic mice conferred by MVA-CoV2-S vaccine candidate.

Vaccines against SARS-CoV-2 have been shown to be safe and effective but their protective efficacy against infection in the brain is yet unclear. Here, in the susceptible transgenic K18-hACE2 mouse model of severe coronavirus disease 2019 (COVID-19), we report a spatiotemporal description of SARS-CoV-2 infection and replication through the brain. SARS-CoV-2 brain replication occurs primarily in neurons, leading to neuronal loss, signs of glial activation and vascular damage in mice infected with SARS-CoV-2. One or two doses of a modified vaccinia virus Ankara (MVA) vector expressing the SARS-CoV-2 spike (S) protein (MVA-CoV2-S) conferred full protection against SARS-CoV-2 cerebral infection, preventing virus replication in all areas of the brain and its associated damage. This protection was maintained even after SARS-CoV-2 reinfection. These findings further support the use of MVA-CoV2-S as a promising vaccine candidate against SARS-CoV-2/COVID-19.

Activation of CD4 T cells during prime immunization determines the success of a therapeutic hepatitis B vaccine in HBV-carrier mouse models

We recently developed a heterologous therapeutic vaccination scheme (TherVacB) comprising a particulate protein prime followed by a modified vaccinia-virus Ankara (MVA)-vector boost for the treatment of HBV. However, the key determinants required to overcome HBV-specific immune tolerance remain unclear. Herein, we aimed to study new combination adjuvants and unravel factors that are essential for the antiviral efficacy of TherVacB. Recombinant hepatitis B surface and core antigen (HBsAg and HBcAg) particles were formulated with different liposome- or oil-in-water emulsion-based combination adjuvants containing saponin QS21 and monophosphoryl lipid A; these formulations were compared to STING-agonist c-di-AMP and conventional aluminium hydroxide formulations. Immunogenicity and the antiviral effects of protein antigen formulations and the MVA-vector boost within TherVacB were evaluated in adeno-associated virus-HBV-infected and HBV-transgenic mice. Combination adjuvant formulations preserved HBsAg and HBcAg integrity for ≥12 weeks, promoted human and mouse dendritic cell activation and, within TherVacB, elicited robust HBV-specific antibody and T-cell responses in wild-type and HBV-carrier mice. Combination adjuvants that prime a balanced HBV-specific type 1 and 2T helper response induced high-titer anti-HBs antibodies, cytotoxic T-cell responses and long-term control of HBV. In the absence of an MVA-vector boost or following selective CD8 T-cell depletion, HBsAg still declined (mediated mainly by anti-HBs antibodies) but HBV replication was not controlled. Selective CD4 T-cell depletion during the priming phase of TherVacB resulted in a complete loss of vaccine-induced immune responses and its therapeutic antiviral effect in mice. Our results identify CD4 T-cell activation during the priming phase of TherVacB as a key determinant of HBV-specific antibody and CD8 T-cell responses. Therapeutic vaccination is a potentially curative treatment option for chronic hepatitis B. However, it remains unclear which factors are essential for breaking immune tolerance in HBV carriers and determining successful outcomes. Our study provides the first direct evidence that efficient priming of HBV-specific CD4 T cells determines the success of therapeutic hepatitis B vaccination in two preclinical HBV-carrier mouse models. Applying an optimal formulation of HBV antigens that activates CD4 and CD8 T cells during prime immunization provided the foundation for an antiviral effect of therapeutic vaccination, while depletion of CD4 T cells led to a complete loss of vaccine-induced antiviral efficacy. Boosting CD8 T cells was important to finally control HBV in these mouse models. Our findings provide important insights into the rational design of therapeutic vaccines for the cure of chronic hepatitis B.

Characteristics of and prevention/control measures against the worldwide outbreak of human monkeypox 2022

Human monkeypox (hMPX) is a smallpox-like disease caused by the monkeypox virus (MPXV) that belongs to the genus of Orthopoxvirus, in the family of Poxviridae. The natural hosts of MPXV are species of rodents, which are found in habitats in Central and Western Africa. Sporadic cases of patients with hMPX have been identified in central Africa since the discovery of the first cases in the early 1970s in the Democratic Republic of the Congo (DRC) and Western African countries. Since May 2022 (and up to the end of October 2022), more than 75,000 patients with hMPX have been reported, mainly in European and American countries. In the current outbreak, MPXV is transmitted from human to human, through close sexual contact, especially among men who have sex with men (MSM). Safe and effective third-generation smallpox vaccines, namely, LC16m8 and modified vaccinia virus Ankara (MVA), are effective in protecting vaccinees from hMPX. It is highly possible that immediate vaccination of close contacts with MVA or LC16m8, before disease onset, may be effective in reducing the severity of hMPX if infected. A proper vaccination program would reduce the scale of the current hMPX outbreak. Furthermore, hMPX in endemic areas should be prevented through mass vaccination programs with third-generation vaccines for those living in these regions. Notably, the current hMPX outbreak is mainly associated with community-specific MSM circumstances. Special consideration should be given to patients with hMPX, who must be protected from societal discrimination.

Creation of poxvirus expressing foot-and-mouth and peste des petits ruminant disease virus proteins

Foot-and-mouth disease (FMD) and Peste des petits ruminant disease (PPR) are acute and severe infectious diseases of sheep and are listed as animal diseases for compulsory immunization. However, there is no dual vaccine to prevent these two diseases. The Modified Vaccinia virus Ankara strain (MVA) has been widely used in the construction of recombinant live vector vaccine because of its large capacity of foreign gene, wide hostrange, high safety, and immunogenicity. In this study, MVA-GFP recombinant virus skeleton was used to construct dual live vector vaccines against FMD and PPR. The recombinant plasmid pUC57-FMDV P1-2A3CPPRV FH was synthesized and transfected into MVA-GFP infected CEF cells for homologous recombination. The results showed that a recombinant virus without fluorescent labeling was obtained after multiple rounds of plaque screening. The recombinant virus successfully expressed the target proteins, and the empty capsid of FMDV could be observed by transmission electron microscope (TME), and the expression levels of foreign proteins (VP1 and VP3) detected by ELISA were like those detected in FMDV-infected cells. This study laidthe foundation for the successful construction of a live vector vaccine against FMD and PPR. • A recombinant MVA expressing FMDVP12A3C and PRRV HF proteins • Both the FMDV and PRRV proteins inserted into the virus were expressed • The proteins expressed by the recombinant poxvirus were assembled into VLPs.

Stabilized recombinant SARS-CoV-2 spike antigen enhances vaccine immunogenicity and protective capacity.

The SARS-CoV-2 spike (S) glycoprotein is synthesized as a large precursor protein and must be activated by proteolytic cleavage into S1 and S2. A recombinant modified vaccinia virus Ankara (MVA) expressing native, full-length S protein (MVA-SARS-2-S) is currently under investigation as a candidate vaccine in phase I clinical studies. Initial results from immunogenicity monitoring revealed induction of S-specific antibodies binding to S2, but low-level antibody responses to the S1 domain. Follow-up investigations of native S antigen synthesis in MVA-SARS-2-S-infected cells revealed limited levels of S1 protein on the cell surface. In contrast, we found superior S1 cell surface presentation upon infection with a recombinant MVA expressing a stabilized version of SARS-CoV-2 S protein with an inactivated S1/S2 cleavage site and K986P and V987P mutations (MVA-SARS-2-ST). When comparing immunogenicity of MVA vector vaccines, mice vaccinated with MVA-SARS-2-ST mounted substantial levels of broadly reactive anti-S antibodies that effectively neutralized different SARS-CoV-2 variants. Importantly, intramuscular MVA-SARS-2-ST immunization of hamsters and mice resulted in potent immune responses upon challenge infection and protected from disease and severe lung pathology. Our results suggest that MVA-SARS-2-ST represents an improved clinical candidate vaccine and that the presence of plasma membrane-bound S1 is highly beneficial to induce protective antibody levels.

Efficient production of protein complexes in mammalian cells using a poxvirus vector.

The production of full length, biologically active proteins in mammalian cells is critical for a wide variety of purposes ranging from structural studies to preparation of subunit vaccines. Prior research has shown that Modified vaccinia virus Ankara encoding the bacteriophage T7 RNA polymerase (MVA-T7) is particularly suitable for high level expression of proteins upon infection of mammalian cells. The expression system is safe for users and 10-50 mg of full length, biologically active proteins may be obtained in their native state, from a few litres of infected cell cultures. Here we report further improvements which allow an increase in the ease and speed of recombinant virus isolation, the scale-up of protein production and the simultaneous synthesis of several polypeptides belonging to a protein complex using a single virus vector. Isolation of MVA-T7 viruses encoding foreign proteins was simplified by combining positive selection for virus recombinants and negative selection against parental virus, a process which eliminated the need for tedious plaque purification. Scale-up of protein production was achieved by infecting a BHK 21 suspension cell line and inducing protein expression with previously infected cells instead of virus, thus saving time and effort in handling virus stocks. Protein complexes were produced from infected cells by concatenating the Tobacco Etch Virus (TEV) N1A protease sequence with each of the genes of the complex into a single ORF, each gene being separated from the other by twin TEV protease cleavage sites. We report the application of these methods to the production of a complex formed on the one hand between the HIV-1 integrase and its cell partner LEDGF and on the other between the HIV-1 VIF protein and its cell partners APOBEC3G, CBFβ, Elo B and Elo C. The strategies developed in this study should be valuable for the overexpression and subsequent purification of numerous protein complexes.

Genetic stability of SIV Gag/Tat gene inserted into Del-II in modified vaccinia virus ankara after serial passage of recombinant vector in pCEFs cells

Modified vaccinia virus Ankara (MVA) is an attenuated vaccinia virus with restricted replication in human cells. The virus serves as an ideal vaccine vector suitable for safe use even in immune-compromised individuals. With its inherently large packaging capacity, expression cassettes encoding bulky genes can be inserted into deletion regions within the MVA genome. These deletion sites develop during the process of the attenuation of the virus by passage in Chicken Embryo Fibroblasts (pCEFs). Transgene stability in MVA is important to assure immunogenicity and efficacy. In the present study, we assessed the effect of substantial passage of recombinant MVA vectors on the stability of expression cassette encoding SIV Gag/Tat genes inserted at the Del-II site, as part of generating a vaccine to protect from HIV. Our data indicated that after 15 passages there was a significant loss or mutation of the inserted genes.

Intravenous injection of a novel viral immunotherapy encoding human interleukin-7 in nonhuman primates is safe and increases absolute lymphocyte count

ABSTRACT Persistence of an immunosuppression, affecting both the innate and adaptive arms of the immune system, plays a role in sepsis patients’ morbidity and late mortality pointing to the need for broad and effective immune interventions. MVA-hIL-7-Fc is a non-replicative recombinant Modified Vaccinia virus Ankara encoding the human interleukin-7 fused to human IgG2 Fc fragment. We have shown in murine sepsis models the capacity of this new virotherapy to stimulate both arms of the immune system and increase survival. Herein, an exploratory study in nonhuman primates was performed following a single intravenous injection of the MVA-hIL-7-Fc used at the clinical dose to assess its safety and biological activities. Four cynomolgus macaques were followed for 3 weeks post-injection (p.i), without observed acute adverse reactions. Circulating hIL-7-Fc was detected during the first 3–5 days p.i with a detection peaking at 12 h p.i. IL-7 receptor engagement and downstream signal transduction were detected in T cells demonstrating functionality of the expressed IL-7. Expansion of blood lymphocytes, mainly CD4 and CD8 naïve and central memory T cells, was observed on day 7 p.i. together with a transient increase of Ki67 expression on T lymphocytes. In addition, we observed an increase in circulating B and NK cells as well as monocytes were albeit with different kinetics and levels. This study indicates that a vectorized IL-7-Fc, injected by intravenous route at a relevant clinical dose in a large animal model, is active without adverse reactions supporting the clinical development of this novel virotherapy for treatment of sepsis patients.