Modified vaccinia virus Ankara multiplies in rat IEC-6 cells and limited production of mature virions occurs in other mammalian cell lines

The Feasibility of Elimination of Monkeypox Virus in Nigeria: A Systematic Review

Monkeypox is a zoonotic virus with an increasing incidence in Nigeria, posing significant public health challenges. The virus, related to smallpox, primarily spreads through direct contact with infected animals or humans and has been noted for its potential for wider transmission due to changing ecological and social dynamics. This research aims to evaluate the feasibility of eliminating monkeypox in Nigeria through integrated approaches involving vaccination, public health strategies, and ecological management. Additionally, it seeks to propose a unified public health strategy, incorporating One Health principles, to achieve the elimination of monkeypox in Nigeria. A review of the feasibility of eliminating the monkeypox virus in Nigeria was conducted using databases like Science Direct, Cochrane, PubMed, and Medline. The search was guided by the methodologies and reporting guidelines of the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA). The initial search yielded 89 publications, but the number of articles that required examination was reduced after applying selected keywords and evaluating abstracts. We deemed 32 articles relevant to the subject after applying inclusion and exclusion criteria. The findings are analyzed, highlighting their limitations and strengths and discussing practical implications, knowledge gaps, and recommendations for future research. This study provides evidence supporting the feasibility of the elimination of the monkeypox virus in Nigeria. Strategic recommendations for a sustainable public health approach to eliminating monkeypox emphasize preventive measures, community engagement, and ecological preservation. This study will provide critical insights into the feasibility of eliminating monkeypox in Nigeria, offering a model that can be adapted for other regions facing similar challenges. The integration of health, ecological, and community-focused strategies is expected to contribute significantly to global efforts to control and potentially eradicate monkeypox. This research could serve as a foundational study for public health authorities in Nigeria and internationally, informing policy and operational decisions to control and eliminate monkeypox as a public health threat. The monkeypox virus reemerges in Nigeria, increasing mortality rates. Awareness programs should be conducted on its danger, transmission mode, and potential human transmission. Public education on the lack of treatment and vaccines is crucial. Meat inspection laws should be enforced to ensure safe animal consumption.

Whole genome sequencing of recombinant viruses obtained from co-infection and superinfection of Vero cells with modified vaccinia virus ankara vectored influenza vaccine and a naturally occurring cowpox virus

Modified vaccinia virus Ankara (MVA) has been widely tested in clinical trials as recombinant vector vaccine against infectious diseases and cancers in humans and animals. However, one biosafety concern about the use of MVA vectored vaccine is the potential for MVA to recombine with naturally occurring orthopoxviruses in cells and hosts in which it multiplies poorly and, therefore, producing viruses with mosaic genomes with altered genetic and phenotypic properties. We previously conducted co-infection and superinfection experiments with MVA vectored influenza vaccine (MVA-HANP) and a feline Cowpox virus (CPXV-No-F1) in Vero cells (that were semi-permissive to MVA infection) and showed that recombination occurred in both co-infected and superinfected cells. In this study, we selected the putative recombinant viruses and performed genomic characterization of these viruses. Some putative recombinant viruses displayed plaque morphology distinct of that of the parental viruses. Our analysis demonstrated that they had mosaic genomes of different lengths. The recombinant viruses, with a genome more similar to MVA-HANP (>50%), rescued deleted and/or fragmented genes in MVA and gained new host ranges genes. Our analysis also revealed that some MVA-HANP contained a partially deleted transgene expression cassette and one recombinant virus contained part of the transgene expression cassette similar to that incomplete MVA-HANP. The recombination in co-infected and superinfected Vero cells resulted in recombinant viruses with unpredictable biological and genetic properties as well as recovery of delete/fragmented genes in MVA and transfer of the transgene into replication competent CPXV. These results are relevant to hazard characterization and risk assessment of MVA vectored biologicals.

The monkeypox diagnosis, treatments and prevention: A review

The world is currently dealing with a second viral outbreak, monkeypox, which has the potential to become an epidemic after the COVID-19 pandemic. People who reside in or close to forest might be exposed indirectly or at a low level, resulting in subclinical disease. However, the disease has lately emerged in shipped African wild mice in the United States. Smallpox can cause similar signs and symptoms to monkeypox, such as malaise, fever, flu-like signs, headache, distinctive rash, and back pain. Because Smallpox has been eliminated, similar symptoms in a monkeypox endemic zone should be treated cautiously. Monkeypox is transmitted to humans primarily via interaction with diseased animals. Infection through inoculation via interaction with skin or scratches and mucosal lesions on the animals is conceivable significantly once the skin barrier is disrupted by scratches, bites, or other disturbances or trauma. Even though it is clinically unclear from other pox-like infections, laboratory diagnosis is essential. There is no approved treatment for human monkeypox virus infection, however, smallpox vaccination can defend counter to the disease. Human sensitivity to monkeypox virus infection has grown after mass vaccination was discontinued in the 1980s. Infection may be prevented by reducing interaction with sick patients or animals and reducing respiratory exposure among people who are infected.

Development of Modified Vaccinia Virus Ankara-Based Vaccines: Advantages and Applications

Modified vaccinia virus Ankara (MVA) is a promising viral vector for vaccine development. MVA is well studied and has been widely used for vaccination against smallpox in Germany. This review describes the history of the origin of the virus and its properties as a vaccine, including a high safety profile. In recent years, MVA has found its place as a vector for the creation of vaccines against various diseases. To date, a large number of vaccine candidates based on the MVA vector have already been developed, many of which have been tested in preclinical and clinical studies. We discuss data on the immunogenicity and efficacy of some of these vaccines.

Monkeypox Virus in Nigeria: Infection Biology, Epidemiology, and Evolution

Monkeypox is a zoonotic disease caused by monkeypox virus (MPXV), which is a member of orthopoxvirus genus. The reemergence of MPXV in 2017 (at Bayelsa state) after 39 years of no reported case in Nigeria, and the export of travelers' monkeypox (MPX) from Nigeria to other parts of the world, in 2018 and 2019, respectively, have raised concern that MPXV may have emerged to occupy the ecological and immunological niche vacated by smallpox virus. This review X-rays the current state of knowledge pertaining the infection biology, epidemiology, and evolution of MPXV in Nigeria and worldwide, especially with regard to the human, cellular, and viral factors that modulate the virus transmission dynamics, infection, and its maintenance in nature. This paper also elucidates the role of recombination, gene loss and gene gain in MPXV evolution, chronicles the role of signaling in MPXV infection, and reviews the current therapeutic options available for the treatment and prevention of MPX. Additionally, genome-wide phylogenetic analysis was undertaken, and we show that MPXV isolates from recent 2017 outbreak in Nigeria were monophyletic with the isolate exported to Israel from Nigeria but do not share the most recent common ancestor with isolates obtained from earlier outbreaks, in 1971 and 1978, respectively. Finally, the review highlighted gaps in knowledge particularly the non-identification of a definitive reservoir host animal for MPXV and proposed future research endeavors to address the unresolved questions.

Identification and characterization of PEDV infection in rat crypt epithelial cells

•

The rat crypt epithelial cells (IEC-6) were highly susceptible to different subtypes of PEDV.

•

The PEDV replication capacity in IEC-6 cells was similar to Vero cells and superior to that in IPEC-J2 cells.

•

PEDV infection activated a robust immune response in IEC-6 cells.

Porcine epidemic diarrhea (PED) is a devastating enteric disease to the world's swine production. Porcine epidemic diarrhea virus (PEDV), as the PED causative agent, has been commonly propagated and investigated in Vero cells, as well as in IPEC-J2, a porcine epithelial cell-jejunum 2. However, Vero cells, which are defective in interferon production, cannot represent the host response in enteric cells while PEDV replicates poorly in IPEC-J2 cells. In this study, we observed that rat crypt epithelial cells (IEC-6) were highly susceptible to different subtypes of PEDV. The replication kinetics of PEDV in IEC-6 cells is similar to that in Vero cells, but it is much higher than in IPEC-J2 cells. Besides that, PEDV infection in IEC-6 cells can induce the production of inflammatory cytokines and interferon, especially the type III IFNs. Collectively, our findings suggest that IEC-6 is an ideal cell line for PEDV replication and immune response studies.

Orf virus (ORFV) infection in a three-dimensional human skin model: Characteristic cellular alterations and interference with keratinocyte differentiation

ORF virus (ORFV) is the causative agent of contagious ecthyma, a pustular dermatitis of small ruminants and humans. Even though the development of lesions caused by ORFV was extensively studied in animals, only limited knowledge exists about the lesion development in human skin. The aim of the present study was to evaluate a three-dimensional (3D) organotypic culture (OTC) as a human skin model for ORFV infection considering lesion development, replication of the virus, viral gene transcription and modulation of differentiation of human keratinocytes by ORFV. ORFV infection of OTC was performed using the ORFV isolate B029 derived from a human patient. The OTC sections showed a similar structure of stratified epidermal keratinocytes as human foreskin and a similar expression profile of the differentiation markers keratin 1 (K1), K10, and loricrin. Upon ORFV infection, OTCs exhibited histological cytopathic changes including hyperkeratosis and ballooning degeneration of the keratinocytes. ORFV persisted for 10 days and was located in keratinocytes of the outer epidermal layers. ORFV-specific early, intermediate and late genes were transcribed, but limited viral spread and restricted cell infection were noticed. ORFV infection resulted in downregulation of K1, K10, and loricrin at the transcriptional level without affecting proliferation as shown by PCNA or Ki-67 expression. In conclusion, OTC provides a suitable model to study the interaction of virus with human keratinocytes in a similar structural setting as human skin and reveals that ORFV infection downregulates several differentiation markers in the epidermis of the human skin, a hitherto unknown feature of dermal ORFV infection in man.

Hazard Characterization of Modified Vaccinia Virus Ankara Vector: What Are the Knowledge Gaps?

Modified vaccinia virus Ankara (MVA) is the vector of choice for human and veterinary applications due to its strong safety profile and immunogenicity in vivo. The use of MVA and MVA-vectored vaccines against human and animal diseases must comply with regulatory requirements as they pertain to environmental risk assessment, particularly the characterization of potential adverse effects to humans, animals and the environment. MVA and recombinant MVA are widely believed to pose low or negligible risk to ecosystem health. However, key aspects of MVA biology require further research in order to provide data needed to evaluate the potential risks that may occur due to the use of MVA and MVA-vectored vaccines. The purpose of this paper is to identify knowledge gaps in the biology of MVA and recombinant MVA that are of relevance to its hazard characterization and discuss ongoing and future experiments aimed at providing data necessary to fill in the knowledge gaps. In addition, we presented arguments for the inclusion of uncertainty analysis and experimental investigation of verifiable worst-case scenarios in the environmental risk assessment of MVA and recombinant MVA. These will contribute to improved risk assessment of MVA and recombinant MVA vaccines.

Environmental risk assessment of clinical trials involving modified vaccinia virus Ankara (MVA)-based vectors

The modified vaccinia virus Ankara (MVA) strain, which has been developed as a vaccine against smallpox, is since the nineties widely tested in clinical trials as recombinant vector for vaccination or gene therapy applications. Although MVA is renowned for its safety, several biosafety aspects need to be considered when performing the risk assessment of a recombinant MVA (rMVA). This paper presents the biosafety issues and the main lessons learned from the evaluation of the clinical trials with rMVA performed in Belgium. Factors such as the specific characteristics of the rMVA, the inserted foreign sequences/transgene, its ability for reconversion, recombination and dissemination in the population and the environment are the main points of attention. Measures to prevent or manage identified risks are also discussed.

Truncation of gene F5L partially masks rescue of vaccinia virus strain MVA growth on mammalian cells by restricting plaque size

Modified vaccinia virus Ankara (MVA) is a candidate vaccine vector that is severely attenuated due to mutations acquired during several hundred rounds of serial passage in vitro. A previous study used marker rescue to produce a set of MVA recombinants with improved replication on mammalian cells. Here, we extended the characterization of these rescued MVA strains and identified vaccinia virus (VACV) gene F5L as a determinant of plaque morphology but not replication in vitro. F5 joins a growing group of VACV proteins that influence plaque formation more strongly than virus replication and which are disrupted in MVA. These defective genes in MVA confound the interpretation of marker rescue experiments designed to map mutations responsible for the attenuation of this important VACV strain.

Vaccinia virus immune evasion: mechanisms, virulence and immunogenicity

Virus infection of mammalian cells is sensed by pattern recognition receptors and leads to an innate immune response that restricts virus replication and induces adaptive immunity. In response, viruses have evolved many countermeasures that enable them to replicate and be transmitted to new hosts, despite the host innate immune response. Poxviruses, such as vaccinia virus (VACV), have large DNA genomes and encode many proteins that are dedicated to host immune evasion. Some of these proteins are secreted from the infected cell, where they bind and neutralize complement factors, interferons, cytokines and chemokines. Other VACV proteins function inside cells to inhibit apoptosis or signalling pathways that lead to the production of interferons and pro-inflammatory cytokines and chemokines. In this review, these VACV immunomodulatory proteins are described and the potential to create more immunogenic VACV strains by manipulation of the gene encoding these proteins is discussed.

Attenuation and immunogenicity of host-range extended modified vaccinia virus Ankara recombinants

Modified vaccinia virus Ankara (MVA) is being widely investigated as a safe smallpox vaccine and as an expression vector to produce vaccines against other infectious diseases and cancer. MVA was isolated following more than 500 passages in chick embryo fibroblasts and suffered several major deletions and numerous small mutations resulting in replication defects in human and most other mammalian cells as well as severe attenuation of pathogenicity. Due to the host range restriction, primary chick embryo fibroblasts are routinely used for production of MVA-based vaccines. While a replication defect undoubtedly contributes to safety of MVA, it is worth considering whether host range and attenuation are partially separable properties. Marker rescue transfection experiments resulted in the creation of recombinant MVAs with extended mammalian cell host range. Here, we characterize two host-range extended rMVAs and show that they (i) have acquired the ability to stably replicate in Vero cells, which are frequently used as a cell substrate for vaccine manufacture, (ii) are severely attenuated in immunocompetent and immunodeficient mouse strains following intranasal infection, (iii) are more pathogenic than MVA but less pathogenic than the ACAM2000 vaccine strain at high intracranial doses, (iv) do not form lesions upon tail scratch in mice in contrast to ACAM2000 and (v) induce protective humoral and cell-mediated immune responses similar to MVA. The extended host range of rMVAs may be useful for vaccine production.

Vaccination with recombinant modified vaccinia virus Ankara prevents the onset of intestinal allergy in mice

BACKGROUND

Modified vaccinia virus Ankara (MVA)-encoding antigens are considered as safe vaccine candidates for various infectious diseases in humans. Here, we investigated the immune-modulating properties of MVA-encoding ovalbumin (MVA-OVA) on the allergen-specific immune response.

METHODS

The immune-modulating properties of MVA-OVA were investigated using GM-CSF-differentiated BMDCs from C57BL/6 mice. OVA expression upon MVA-OVA infection of BMDCs was monitored. Activation and maturation markers on viable MVA-OVA-infected mDCs were analyzed by flow cytometry. Secretion of INF-γ, IL-2, and IL-10 was determined in a co-culture of BMDCs infected with wtMVA or MVA-OVA and OVA-specific OT-I CD8(+) and OT-II CD4(+ ) T cells. BALB/c mice were vaccinated with wtMVA, MVA-OVA, or PBS, sensitized to OVA/alum and challenged with a diet containing chicken egg white. OVA-specific IgE, IgG1, and IgG2a and cytokine secretion from mesenteric lymph node (MLN) cells were analyzed. Body weight, body temperature, food uptake, intestinal inflammation, and health condition of mice were monitored.

RESULTS

Infection with wtMVA and MVA-OVA induced comparable activation of mDCs. MVA-OVA-infected BMDCs expressed OVA and induced enhanced IFN-γ and IL-2 secretion from OVA-specific CD8(+ ) T cells in comparison with OVA, wtMVA, or OVA plus wtMVA. Prophylactic vaccination with MVA-OVA significantly repressed OVA-specific IgE, whereas OVA-specific IgG2a was induced. MVA-OVA vaccination suppressed TH 2 cytokine production in MLN cells and prevented the onset of allergic symptoms and inflammation in a mouse model of OVA-induced intestinal allergy.

CONCLUSION

Modified vaccinia virus Ankara-ovalbumin (MVA-OVA) vaccination induces a strong OVA-specific TH 1- immune response, likely mediated by the induction of IFN-γ and IgG2a. Finally, MVA-based vaccines need to be evaluated for their therapeutic potential in established allergy models.

Protein B5 is required on extracellular enveloped vaccinia virus for repulsion of superinfecting virions

Vaccinia virus (VACV) spreads across cell monolayers fourfold faster than predicted from its replication kinetics. Early after infection, infected cells repulse some superinfecting extracellular enveloped virus (EEV) particles by the formation of actin tails from the cell surface, thereby causing accelerated spread to uninfected cells. This strategy requires the expression of two viral proteins, A33 and A36, on the surface of infected cells and upon contact with EEV this complex induces actin polymerization. Here we have studied this phenomenon further and investigated whether A33 and A36 expression in cell lines causes an increase in VACV plaque size, whether these proteins are able to block superinfection by EEV, and which protein(s) on the EEV surface are required to initiate the formation of actin tails from infected cells. Data presented show that VACV plaque size was not increased by expression of A33 and A36, and these proteins did not block entry of the majority of EEV binding to these cells. In contrast, expression of proteins A56 and K2 inhibited entry of both EEV and intracellular mature virus. Lastly, VACV protein B5 was required on EEV to induce the formation of actin tails at the surface of cells expressing A33 and A36, and B5 short consensus repeat 4 is critical for this induction.

Comparative sequence analysis of A-type inclusion (ATI) and P4c proteins of orthopoxviruses that produce typical and atypical ATI phenotypes

Some orthopoxviruses produce large proteinaceous intracellular bodies, known as A-type inclusions (ATIs) during infection of host cells. Virions associate with ATIs resulting in distinct phenotypes referred to as V+, V+/ and V⁻. The phenotype V+ has the virions embedded in the ATI matrix; V⁻ has no virions embedded within or on the surface of the ATI matrix, whereas an aberrant phenotype, the V+/ has virions only on the surface of ATIs. Viruses that do not produce ATI are designated as V⁰. Recombinant viruses generated from a V+ cowpox virus (CPXV) and a V⁰ transgenic vaccinia virus (VACV) produced aberrant V+/ ATIs. ATI phenotype is dependent on the A-type inclusion protein (Atip) and the P4c protein. We sequenced the atip and p4c genes of parental and progeny recombinant viruses as well as their flanking sequences. The atip and p4c open reading frames were identical in parental V+ CPXV and hybrid V+/ progenies. Our results suggest that additional viral gene(s) are required for the formation of wild type V+ ATI.

Introduction of the six major genomic deletions of modified vaccinia virus Ankara (MVA) into the parental vaccinia virus is not sufficient to reproduce an MVA-like phenotype in cell culture and in mice

Modified vaccinia virus Ankara (MVA) has a highly restricted host range in cell culture and is apathogenic in vivo. MVA was derived from the parental chorioallantois vaccinia virus Ankara (CVA) by more than 570 passages in chicken embryo fibroblast (CEF) cells. During CEF cell passaging, six major deletions comprising 24,668 nucleotides occurred in the CVA genome. We have cloned both the MVA and the parental CVA genome as bacterial artificial chromosomes (BACs) and have sequentially introduced the six major MVA deletions into the cloned CVA genome. Reconstituted mutant CVA viruses containing up to six major MVA deletions showed no detectable replication restriction in 12 of 14 mammalian cell lines tested; the exceptions were rabbit cell lines RK13 and SIRC. In mice, CVA mutants with up to three deletions showed slightly enhanced virulence, suggesting that gene deletion in replicating vaccinia virus (VACV) can result in gain of fitness in vivo. CVA mutants containing five or all six deletions were still pathogenic, with a moderate degree of attenuation. Deletion V was mainly responsible for the attenuated phenotype of these mutants. In conclusion, loss or truncation of all 31 open reading frames in the six major deletions is not sufficient to reproduce the specific MVA phenotype of strong attenuation and highly restricted host range. Mutations in viral genes outside or in association with the six major deletions appear to contribute significantly to this phenotype. Host range restriction and avirulence of MVA are most likely a cooperative effect of gene deletions and mutations involving the major deletions.

In vitro host range, multiplication and virion forms of recombinant viruses obtained from co-infection in vitro with a vaccinia-vectored influenza vaccine and a naturally occurring cowpox virus isolate

Background

Poxvirus-vectored vaccines against infectious diseases and cancer are currently under development. We hypothesized that the extensive use of poxvirus-vectored vaccine in future might result in co-infection and recombination between the vaccine virus and naturally occurring poxviruses, resulting in hybrid viruses with unpredictable characteristics. Previously, we confirmed that co-infecting in vitro a Modified vaccinia virus Ankara (MVA) strain engineered to express influenza virus haemagglutinin (HA) and nucleoprotein (NP) genes with a naturally occurring cowpox virus (CPXV-NOH1) resulted in recombinant progeny viruses (H Hansen, MI Okeke, Ø Nilssen, T Traavik, Vaccine 23: 499–506, 2004). In this study we analyzed the biological properties of parental and progeny hybrid viruses.

Results

Five CPXV/MVA progeny viruses were isolated based on plaque phenotype and the expression of influenza virus HA protein. Progeny hybrid viruses displayed in vitro cell line tropism of CPXV-NOH1, but not that of MVA. The HA transgene or its expression was lost on serial passage of transgenic viruses and the speed at which HA expression was lost varied with cell lines. The HA transgene in the progeny viruses or its expression was stable in African Green Monkey derived Vero cells but became unstable in rat derived IEC-6 cells. Hybrid viruses lacking the HA transgene have higher levels of virus multiplication in mammalian cell lines and produced more enveloped virions than the transgene positive progenitor virus strain. Analysis of the subcellular localization of the transgenic HA protein showed that neither virus strain nor cell line have effect on the subcellular targets of the HA protein. The influenza virus HA protein was targeted to enveloped virions, plasma membrane, Golgi apparatus and cytoplasmic vesicles.

Conclusion

Our results suggest that homologous recombination between poxvirus-vectored vaccine and naturally circulating poxviruses, genetic instability of the transgene, accumulation of non-transgene expressing vectors or hybrid virus progenies, as well as cell line/type specific selection against the transgene are potential complications that may result if poxvirus vectored vaccines are extensively used in animals and man.

Candidate influenza vaccines based on recombinant modified vaccinia virus Ankara

Recombinant modified vaccinia virus Ankara (MVA) is attractive and promising as a novel viral vector for the expression of foreign genes of interest because it possesses unique properties. In particular, its excellent safety profile and the availability of versatile vector technologies have frequently made MVA the vaccinia virus of choice for preclinical and clinical studies. Owing to its avirulence and deficiency to productively replicate after in vivo inoculation, MVA can be used under biosafety level 1 conditions. In addition to a better safety profile than replication competent vaccinia viruses, the use of MVA leads to similar levels of gene expression and has better immunostimulatory properties and improved efficacy as a recombinant vaccine. In animal models, recombinant MVA vaccines were immunogenic and induced protective immunity against various infectious agents, including viruses, bacteria and parasites. Here we review the progress that has been made in the development of recombinant MVA as a viral vector and candidate pandemic influenza H5N1 vaccine. Specifically, we will focus on the preclinical evaluation of recombinant MVA vector as pandemic influenza A/H5N1 vaccine candidates and discuss the possible future approaches for the use of these novel MVA-based vaccines.

Recombination-mediated genetic engineering of a bacterial artificial chromosome clone of modified vaccinia virus Ankara (MVA)

The production, manipulation and rescue of a bacterial artificial chromosome clone of Vaccinia virus (VAC-BAC) in order to expedite construction of expression vectors and mutagenesis of the genome has been described (Domi & Moss, 2002, PNAS99 12415–20). The genomic BAC clone was ‘rescued’ back to infectious virus using a Fowlpox virus helper to supply transcriptional machinery. We apply here a similar approach to the attenuated strain Modified Vaccinia virus Ankara (MVA), now widely used as a safe non-replicating recombinant vaccine vector in mammals, including humans. Four apparently full-length, rescuable clones were obtained, which had indistinguishable immunogenicity in mice. One clone was shotgun sequenced and found to be identical to the parent. We employed GalK recombination-mediated genetic engineering (recombineering) of MVA-BAC to delete five selected viral genes. Deletion of C12L, A44L, A46R or B7R did not significantly affect CD8⁺ T cell immunogenicity in BALB/c mice, but deletion of B15R enhanced specific CD8⁺ T cell responses to one of two endogenous viral epitopes (from the E2 and F2 proteins), in accordance with published work (Staib et al., 2005, J. Gen. Virol.86, 1997–2006). In addition, we found a higher frequency of triple-positive IFN-γ, TNF-α and IL-2 secreting E3-specific CD8+ T-cells 8 weeks after vaccination with MVA lacking B15R. Furthermore, a recombinant vaccine capable of inducing CD8⁺ T cells against an epitope from Plasmodium berghei was created using GalK counterselection to insert an antigen expression cassette lacking a tandem marker gene into the traditional thymidine kinase locus of MVA-BAC. MVA continues to feature prominently in clinical trials of recombinant vaccines against diseases such as HIV-AIDS, malaria and tuberculosis. Here we demonstrate in proof-of-concept experiments that MVA-BAC recombineering is a viable route to more rapid and efficient generation of new candidate mutant and recombinant vaccines based on a clinically deployable viral vector.

In vitro permissivity of bovine cells for wild-type and vaccinal myxoma virus strains

Myxoma virus (MYXV), a leporide-specific poxvirus, represents an attractive candidate for the generation of safe, non-replicative vaccine vector for non-host species. However, there is very little information concerning infection of non-laboratory animals species cells with MYXV. In this study, we investigated interactions between bovine cells and respectively a wild type strain (T1) and a vaccinal strain (SG33) of MYXV. We showed that bovine KOP-R, BT and MDBK cell lines do not support MYXV production. Electron microscopy observations of BT-infected cells revealed the low efficiency of viral entry and the production of defective virions. In addition, infection of bovine peripheral blood mononuclear cells (PBMC) occurred at a very low level, even following non-specific activation, and was always abortive. We did not observe significant differences between the wild type strain and the vaccinal strain of MYXV, indicating that SG33 could be used for new bovine vaccination strategies.

T-Cell epitope discovery for variola and vaccinia viruses

Variola major, the causative agent of smallpox, afflicted mankind throughout history until the worldwide World Health Organisation WHO vaccination campaign successfully eradicated the disease. Unfortunately, recent concerns about bioterrorism have renewed scientific interest in this virus. One essential component of our biodefense and preparedness efforts is an understanding of poxvirus immunity. To this end a number of laboratories have sought to discover T- and B-Cell epitopes from select agents such as variola virus. This review focuses on the efforts to identify CD8(+) T-Cell epitopes from poxviruses as a means to develop new vaccines and therapeutics. A wide variety of techniques have been employed by several research groups to provide complementary information regarding cellular immune responses to poxviruses. In the last several years well over 100 T-Cell epitopes have been identified and the work rapidly continues. The information gleaned from these studies will not only give us a greater understanding of immunity to variola virus and other viruses, but also provide a foundation for next generation vaccines and additional tools with which to study host-pathogen interactions.