Recombinant Vaccinia Virus Vectors Research Articles

Protection induced by recombinant vaccinia virus targeting the ROP4 of Toxoplasma gondii in mice.

Toxoplasmosis is a parasitic disease affecting a significant portion of the global population, whose etiology can be attributed to the protozoan organism Toxoplasma gondii. Despite its public health importance, an efficacious vaccine to prevent human toxoplasmosis remains unavailable. To this end, we designed an experimental toxoplasmosis vaccine using recombinant vaccinia virus vectors (rVacv) expressing the T. gondii rhoptry protein 4 (ROP4) antigen and evaluated its efficacy in a murine model. Intranasal vaccination with ROP4-rVacvs induced parasite-specific serum antibody responses as early as 3 weeks post-immunization, with subsequent immunizations elevating antibody responses to a greater extent. When challenged with T. gondii ME49 strain, significantly enhanced levels of mucosal IgA antibodies were detected in the intestines of immunized mice. Additionally, ROP4-rVacv immunization ensured that T cells and germinal center B cell populations were retained at high levels. These immune responses mitigated the severity of neuroinflammation, reduced tissue cyst formation, and ensured the survival of immunized mice. Our findings indicate that ROP4-rVacv could be a promising toxoplasmosis vaccine candidate.

Exploring SARS-CoV-2 infection and vaccine-induced immunity in chronic myeloid leukemia patients: insights from real-world data in Brazil and the United States

This study investigates COVID-19 outcomes and immune response in chronic myeloid leukemia (CML) patients post-SARS-CoV-2 vaccination, comparing effectiveness of various vaccine options. Data from 118 CML patients (85 in Brazil, 33 in the US) showed similar infection rates prior (14% Brazil, 9.1% US) and post-vaccination (24.7% vs. 27.3%, respectively). In Brazil, AstraZeneca and CoronaVac were the most commonly used vaccine brands, while in the US, Moderna and Pfizer-BioNTech vaccines dominated. Despite lower seroconversion in the Brazilian cohort, all five vaccine brands analyzed prevented severe COVID-19. Patients who received mRNA and recombinant viral vector vaccines (HR: 2.20; 95%CI 1.07–4.51; p < .031) and those that had achieved at least major molecular response (HR: 1.51; 95% CI 1.01–3.31; p < .0001) showed higher seroconversion rates. Our findings suggest that CML patients can generate antibody responses regardless of the vaccine brand, thereby mitigating severe COVID-19. This effect is more pronounced in patients with well-controlled disease.

Comparison of heterologous prime-boost immunization strategies with DNA and recombinant vaccinia virus co-expressing GP3 and GP5 of European type porcine reproductive and respiratory syndrome virus in pigs

Vaccination is principally used to control and treat porcine reproductive and respiratory syndrome virus (PRRSV) infection. This study investigated immunogenicity and protective efficacy of heterologous prime-boost regimens in pigs, including recombinant DNA and vaccinia virus vectors coexpressing PRRSV European genotype (EU) isolate GP3 and GP5: group A, pVAX1-EU-GP3-GP5 prime and rddVTT-EU-GP3-GP5 boost; group B, rddVTT-EU-GP3-GP5 prime and pVAX1-EU-GP3-GP5 boost; group C, empty vector pVAX1; group D, E3L gene-deleted vaccinia virus E3L− VTT. Vaccine efficacy was tested in an EU-type PRRSV (Lelystad virus strain) challenge pig model based on evaluating PRRSV-specific antibody responses, neutralizing antibodies, cytokines, T lymphocyte proliferation, CD4+ and CD8+ T lymphocytes, clinical symptoms, viremia and tissue virus loads. Plasmid DNA was delivered as chitosan-DNA nanoparticles, and Quil A (Quillaja) was used to increase vaccine efficiency. All piglets were boosted 21 days post the initial inoculation (dpi) and then challenged 14 days later. At 14, 21, 28 and 35 dpi, groups A and B developed significantly higher PRRSV-specific antibody responses compared with control groups C and D. Two weeks after the boost, significant differences in neutralizing antibody and IFN-γ levels were observed between groups A, C, D and B. At 49 dpi, groups A and B had markedly increased peripheral blood CD3+CD4+ T cell levels. Following virus challenge, group A showed viremia, but organ virus loads were lower than those in other groups. Thus, a heterologous prime-boost vaccine regimen (rddVTT-EU-GP3-GP5 prime, pVAX1-EU-GP3-GP5 boost) can improve humoral- and cell-mediated immune responses to provide resistance to EU-type PRRSV infection in vivo.

Approaches to quality control, preclinical and clinical studies of live recombinant viral vector vaccines

At present, there are not much data on the clinical use of live recombinant viral vector vaccines. Characteristics of new vaccines should be factored into requirements/recommendations for quality control, preclinical and clinical studies of vaccines in order to enable further risk/benefit assessment. The aim of this study was to analyse current approaches to quality control, preclinical and clinical studies of live recombinant viral vector vaccines. The paper provides an overview of the licensed live viral vector vaccines and those at various stages of clinical trials. The authors analysed Russian, European, American, and Japanese guidelines related to quality issues, preclinical and clinical studies of live viral vector vaccines. The analysis demonstrated that the regulatory requirements for live recombinant viral vector vaccines include assessment of a detailed rationale for vaccine development, including information on the choice of the vector, the origin of the heterologous antigen gene(s), elements related to the transgene(s) expression, as well as assessment of the genetic and phenotypic stability of the recombinant virus, the risk of reversion to virulence or recombination with wild type strains, the potential for virus genome integration into the host cell chromosome, the pre-existing immunity to the vector, the intensity of the immune response elicited by the vector, and the reusability of the vector. The choice and number of applicable toxicological and pharmacological models will depend on these aspects. The results of the analysis of approaches to quality control, preclinical and clinical studies of live recombinant viral vector vaccines may be used in the development of Russian regulatory guidelines harmonised with the international norms and regulations.

Review of Poultry Recombinant Vector Vaccines.

The control of poultry diseases has relied heavily on the use of many live and inactivated vaccines. However, over the last 30 yr, recombinant DNA technology has been used to generate many novel poultry vaccines. Fowlpox virus and turkey herpesvirus are the two main vectors currently used to construct recombinant vaccines for poultry. With the use of these two vectors, more than 15 recombinant viral vector vaccines against Newcastle disease, infectious laryngotracheitis, infectious bursal disease, avian influenza, and Mycoplasma gallisepticum have been developed and are commercially available. This review focuses on current knowledge about the safety and efficacy of recombinant viral vectored vaccines and the mechanisms by which they facilitate the control of multiple diseases. Additionally, the development of new recombinant vaccines with novel vectors will be briefly discussed.

Environmental Risk Assessment of Recombinant Viral Vector Vaccines against SARS-Cov-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the coronavirus disease 2019 (COVID-19) pandemic. Over the past months, considerable efforts have been put into developing effective and safe drugs and vaccines against SARS-CoV-2. Various platforms are being used for the development of COVID-19 vaccine candidates: recombinant viral vectors, protein-based vaccines, nucleic acid-based vaccines, and inactivated/attenuated virus. Recombinant viral vector vaccine candidates represent a significant part of those vaccine candidates in clinical development, with two already authorised for use in the European Union and one currently under rolling review by the European Medicines Agency (EMA). Since recombinant viral vector vaccine candidates are considered as genetically modified organisms (GMOs), their regulatory oversight includes besides an assessment of their quality, safety and efficacy, also an environmental risk assessment (ERA). The present article highlights the main characteristics of recombinant viral vector vaccine (candidates) against SARS-CoV-2 in the pipeline and discusses their features from an environmental risk point of view.

Novel Vaccine Technologies in Veterinary Medicine: A Herald to Human Medicine Vaccines.

The success of inactivated and live-attenuated vaccines has enhanced livestock productivity, promoted food security, and attenuated the morbidity and mortality of several human, animal, and zoonotic diseases. However, these traditional vaccine technologies are not without fault. The efficacy of inactivated vaccines can be suboptimal with particular pathogens and safety concerns arise with live-attenuated vaccines. Additionally, the rate of emerging infectious diseases continues to increase and with that the need to quickly deploy new vaccines. Unfortunately, first generation vaccines are not conducive to such urgencies. Within the last three decades, veterinary medicine has spearheaded the advancement in novel vaccine development to circumvent several of the flaws associated with classical vaccines. These third generation vaccines, including DNA, RNA and recombinant viral-vector vaccines, induce both humoral and cellular immune response, are economically manufactured, safe to use, and can be utilized to differentiate infected from vaccinated animals. The present article offers a review of commercially available novel vaccine technologies currently utilized in companion animal, food animal, and wildlife disease control.

COVID-19: Insights into Potential Vaccines.

People around the world ushered in the new year 2021 with a fear of COVID-19, as family members have lost their loved ones to the disease. Millions of people have been infected, and the livelihood of many has been jeopardized due to the pandemic. Pharmaceutical companies are racing against time to develop an effective vaccine to protect against COVID-19. Researchers have developed various types of candidate vaccines with the release of the genetic sequence of the SARS-CoV-2 virus in January. These include inactivated viral vaccines, protein subunit vaccines, mRNA vaccines, and recombinant viral vector vaccines. To date, several vaccines have been authorized for emergency use and they have been administered in countries across the globe. Meanwhile, there are also vaccine candidates in Phase III clinical trials awaiting results and approval from authorities. These candidates have shown positive results in the previous stages of the trials, whereby they could induce an immune response with minimal side effects in the participants. This review aims to discuss the different vaccine platforms and the clinical trials of the candidate vaccines.

Viral Vector Vaccines against Bluetongue Virus.

Bluetongue virus (BTV), the prototype member of the genus Orbivirus (family Reoviridae), is the causative agent of an important livestock disease, bluetongue (BT), which is transmitted via biting midges of the genus Culicoides. To date, up to 29 serotypes of BTV have been described, which are classified as classical (BTV 1–24) or atypical (serotypes 25–27), and its distribution has been expanding since 1998, with important outbreaks in the Mediterranean Basin and devastating incursions in Northern and Western Europe. Classical vaccine approaches, such as live-attenuated and inactivated vaccines, have been used as prophylactic measures to control BT through the years. However, these vaccine approaches fail to address important matters like vaccine safety profile, effectiveness, induction of a cross-protective immune response among serotypes, and implementation of a DIVA (differentiation of infected from vaccinated animals) strategy. In this context, a wide range of recombinant vaccine prototypes against BTV, ranging from subunit vaccines to recombinant viral vector vaccines, have been investigated. This article offers a comprehensive outline of the live viral vectors used against BTV.

Drug-cured experimental Trypanosoma cruziinfections confer long-lasting and cross-strain protection.

BackgroundThe long term and complex nature of Chagas disease in humans has restricted studies on vaccine feasibility. Animal models also have limitations due to technical difficulties in monitoring the extremely low parasite burden that is characteristic of chronic stage infections. Advances in imaging technology offer alternative approaches that circumvent these problems. Here, we describe the use of highly sensitive whole body in vivo imaging to assess the efficacy of recombinant viral vector vaccines and benznidazole-cured infections to protect mice from challenge with Trypanosoma cruzi.Methodology/Principal findingsMice were infected with T. cruzi strains modified to express a red-shifted luciferase reporter. Using bioluminescence imaging, we assessed the degree of immunity to re-infection conferred after benznidazole-cure. Those infected for 14 days or more, prior to the onset of benznidazole treatment, were highly protected from challenge with both homologous and heterologous strains. There was a >99% reduction in parasite burden, with parasites frequently undetectable after homologous challenge. This level of protection was considerably greater than that achieved with recombinant vaccines. It was also independent of the route of infection or size of the challenge inoculum, and was long-lasting, with no significant diminution in immunity after almost a year. When the primary infection was benznidazole-treated after 4 days (before completion of the first cycle of intracellular infection), the degree of protection was much reduced, an outcome associated with a minimal T. cruzi-specific IFN-γ+ T cell response.Conclusions/SignificanceOur findings suggest that a protective Chagas disease vaccine must have the ability to eliminate parasites before they reach organs/tissues, such as the GI tract, where once established, they become largely refractory to the induced immune response.

Sarah Gilbert: carving a path towards a COVID-19 vaccine

Sarah Gilbert: carving a path towards a COVID-19 vaccine

Phase III Vaccines for SARS-CoV-2: A Review of Development and Available Data

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has caused more than 35 million confirmed cases and more than 1 million deaths so far. This has led to global efforts to find effective treatment and vaccination to control disease transmission and decrease severity. The current efforts are focused on developing a vaccine that is safe and effective after one or two doses, provides protection for a minimum of six months, provides protection for high-risk population and reduces the risk of onward viral transmission. In this review, we summarize available information related to the development and safety profile of these phase III vaccines against SARS-CoV-2. Methods Literature search was performed on PubMed, Cochrane and ClinicalTrial.gov using keywords like “SARS-CoV-2”, “COVID-19”, and “Phase III vaccines”. Two individuals performed screening of the resultant library. We assessed different articles for information focusing on vaccines in phase III trials. Results As of September 3, 2020 update by the World Health Organization (WHO), there are currently more than 137 candidate vaccines undergoing preclinical development and of these 34 candidate vaccines are in the clinical evaluation phase, 18 are in phase I and 5 are in phase II. Currently, there are 9 vaccines in the phase III development process. Conclusion Multiple phase III trials of COVID-19 vaccines are in progress across the globe, highlighting the collaborative international efforts to develop a safe and effective vaccine. The available efficacy and safety data of phase I/II trials of these vaccines have shown promising results. Pharmaceutical companies are using different strategies including inactivated vaccines, RNA vaccines, recombinant viral vector vaccines and live attenuated BCG vaccine.

Vaccinia Virus Vectors Targeting Peptides for MHC Class II Presentation to CD4+ T Cells.

CD4+ helper T cells play important roles in providing help to B cells, macrophages, and cytotoxic CD8+ T cells, but also exhibit direct effector functions against a variety of different pathogens. In contrast to CD8+ T cells, CD4+ T cells typically exhibit broader specificities and undergo less clonal expansion during many types of viral infections, which often makes the identification of virus-specific CD4+ T cells technically challenging. In this study, we have generated recombinant vaccinia virus (VacV) vectors that target I-Ab-restricted peptides for MHC class II (MHC-II) presentation to activate CD4+ T cells in mice. Conjugating the lymphocytic choriomeningitis virus immunodominant epitope GP61-80 to either LAMP1 to facilitate lysosomal targeting or to the MHC-II invariant chain (Ii) significantly increased the activation of Ag-specific CD4+ T cells in vivo. Immunization with VacV-Ii-GP61-80 activated endogenous Ag-specific CD4+ T cells that formed memory and rapidly re-expanded following heterologous challenge. Notably, immunization of mice with VacV expressing an MHC-II-restricted peptide from Leishmania species (PEPCK335-351) conjugated to either LAMP1 or Ii also generated Ag-specific memory CD4+ T cells that underwent robust secondary expansion following a visceral leishmaniasis infection, suggesting this approach could be used to generate Ag-specific memory CD4+ T cells against a variety of different pathogens. Overall, our data show that VacV vectors targeting peptides for MHC-II presentation is an effective strategy to activate Ag-specific CD4+ T cells in vivo and could be used to study Ag-specific effector and memory CD4+ T cell responses against a variety of viral, bacterial, or parasitic infections.

Analysis of MHC Class I Processing Pathways That Generate a Response to Vaccinia Virus Late Proteins.

Use of recombinant viral vectors encoding nonnative Ags is an attractive mechanism for the generation of protective Ab, CD4+ T cell (TCD4+), and CD8+ T cell (TCD8+) responses in vivo following immunization. However, the life cycle and tropism of the viral vector, and its interactions with various components of the immune system, must be fully understood to maximize the efficacy of any vaccination strategies. Ab and TCD4+ responses typically target native Ags driven by late promoters in vaccinia virus (VACV)-based vectors. However, it has been demonstrated that model Ags driven by late promoters in recombinant VACV vectors do not stimulate TCD8+ responses, whereas identical Ags driven by early promoters stimulate strong responses. Conversely, TCD8+ can be generated against some natural late VACV Ags. We explored this dichotomy by investigating the Ag presentation pathways responsible for presentation of natural late VACV Ags in mice. We found that all of the late VACV Ags we examined could be cross-primed (i.e., presented by uninfected professional APC), as well as directly presented by infected dendritic cell populations. However, one Ag was only presented by professional APC populations and was not the target of a protective TCD8+ response. Therefore, there is no generalized blockade in Ag presentation of late VACV Ags, and expression of nonnative Ags driven by a late promoter allows production of large quantities of Ag that may allow simultaneous targeting of both TCD4+ and Ab responses, as well as TCD8+ responses, in the future.

RVSVΔG-ZEBOV-GP (also designated V920) recombinant vesicular stomatitis virus pseudotyped with Ebola Zaire Glycoprotein: Standardized template with key considerations for a risk/benefit assessment

The Brighton Collaboration Viral Vector Vaccines Safety Working Group (V3SWG) was formed to evaluate the safety and characteristics of live, recombinant viral vector vaccines. A recent publication by the V3SWG described live, attenuated, recombinant vesicular stomatitis virus (rVSV) as a chimeric virus vaccine for HIV-1 (Clarke et al., 2016). The rVSV vector system is being explored as a platform for development of multiple vaccines. This paper reviews the molecular and biological features of the rVSV vector system, followed by a template with details on the safety and characteristics of a rVSV vaccine against Zaire ebolavirus (ZEBOV). The rVSV-ZEBOV vaccine is a live, replication competent vector in which the VSV glycoprotein (G) gene is replaced with the glycoprotein (GP) gene of ZEBOV. Multiple copies of GP are expressed and assembled into the viral envelope responsible for inducing protective immunity. The vaccine (designated V920) was originally constructed by the National Microbiology Laboratory, Public Health Agency of Canada, further developed by NewLink Genetics Corp. and Merck & Co., and is now in final stages of registration by Merck. The vaccine is attenuated by deletion of the principal virulence factor of VSV (the G protein), which also removes the primary target for anti-vector immunity. The V920 vaccine caused no toxicities after intramuscular (IM) or intracranial injection of nonhuman primates and no reproductive or developmental toxicity in a rat model. In multiple studies, cynomolgus macaques immunized IM with a wide range of virus doses rapidly developed ZEBOV-specific antibodies measured in IgG ELISA and neutralization assays and were fully protected against lethal challenge with ZEBOV virus. Over 20,000 people have received the vaccine in clinical trials; the vaccine has proven to be safe and well tolerated. During the first few days after vaccination, many vaccinees experience a mild acute-phase reaction with fever, headache, myalgia, and arthralgia of short duration; this period is associated with a low-level viremia, activation of anti-viral genes, and increased levels of chemokines and cytokines. Oligoarthritis and rash appearing in the second week occur at a low incidence, and are typically mild-moderate in severity and self-limited. V920 vaccine was used in a Phase III efficacy trial during the West African Ebola epidemic in 2015, showing 100% protection against Ebola Virus Disease, and it has subsequently been deployed for emergency control of Ebola outbreaks in central Africa. The template provided here provides a comprehensive picture of the first rVSV vector to reach the final stage of development and to provide a solution to control of an alarming human disease.

Oncolytic cancer therapy with a vaccinia virus strain.

Oncolytic vaccinia virus is currently undergoing evaluation as a biological anticancer agent in clinical trials. This treatment exploits the lytic nature of a viral infection to eradicate the tumor mass in a cancer cell‑specific manner. So far, various vaccinia strains have been used as backbones in the design of oncolytic agents. However, the efficacy as oncolytic virotherapy of Chinese vaccinia strain Tian Tan(VTT) has not been reported. Vaccinia strain Guang9(VG9), derived from VTT by consecutive plaque‑cloning selection, was attenuated to a greater extent than its parental strain. In this study, the oncolytic efficacy of VG9 was evaluated. We examined in vitro replication and cytotoxicity, in vivo biodistribution, and antitumor effects in a B16 tumor model. The results revealed that VG9 replicated rapidly, but the cytotoxicity varied in different cell lines. Significant antitumor effects of VG9 were observed in a murine melanoma tumor model, and an antitumor cytotoxic T‑lymphocyte response induced by VG9 was also observed. The results indicated that the Chinese vaccinia strain VG9 holds promise in the construction of a recombinant vaccinia virus vector and as a potential therapeutic strategy in cancer treatment.

New generation vaccines against bluetongue virus

Over the last three decades, a variety of approaches have been investigated to develop new types of bluetongue virus (BTB) vaccines, ranging from baculovirus-expressed subunit vaccines to live vector vaccines. DNA vaccines against BTV consist of DNA plasmid expressing different BTV proteins after inoculation of the animals. The recombinant viral vector vaccines against BTV are based on recombinant viruses that express desired BTV antigens in the host upon inoculation. Viruses such as vaccinia, modified vaccinia Ancara (MVA), capripox, canarypox, herpes, myxoma and fowlpox viruses have been used as vectors of BTV genes. The reverse genetics (RG) systems for BTV are useful tools for BTV vaccine development. Disabled infectious single-cycle (DISC) vaccines make it possible to restore virus replication and can be used for differentiating infected from vaccinated animals (DIVA). These vaccines are based on the production of a modified virus with a deletion in one or more genes that are essential for virus replication. Another approach for BTV vaccine development using RG is the disabled infectious single-animal (DISA) vaccine, generated by deletion of NS3/NS3a expression. DISC and DISA vaccines can mimic the natural tropism of the virus and can express BTV proteins at the site of infection. Important advantages of these new generation vaccines over the conventional BTV vaccines are their high efficacy as well as the possibility of applying them for DIVA. At present, there are a number of novel laboratory-scale BTV vaccines that could meet vaccine profiles required for different field situations. However, further development and licensing of these vaccine candidates for many BTV serotypes is needed in order to prepare for future BT outbreaks. To date, all novel BTV vaccines described in this paper are still under laboratory testing. They are not available commercially, and the time of their application in the field is still indefinite. .

Current and future vaccines and vaccination strategies against infectious laryngotracheitis (ILT) respiratory disease of poultry

Infectious laryngotracheitis (ILT) is an economically important respiratory disease of poultry that affects the industry worldwide. Vaccination is the principal tool in the control of the disease. Two types of vaccines, live attenuated and recombinant viral vector, are commercially available. The first generation of GaHV-1 vaccines available since the early 1960′s are live viruses, attenuated by continuous passages in cell culture or embryos. These vaccines significantly reduce mortalities and, in particular, the chicken embryo origin (CEO) vaccines have shown to limit outbreaks of the disease. However, the CEO vaccines can regain virulence and become the source of outbreaks. Recombinant viral vector vaccines, the second generation of GaHV-1 vaccines, were first introduced in the early 2000′s. These are Fowl Pox virus (FPV) and Herpes virus of turkeys (HVT) vectors expressing one or multiple GaHV-1 immunogenic proteins. Recombinant viral vector vaccines are considered a much safer alternative because they do not regain virulence. In the face of challenge, they improve bird performance and ameliorate clinical signs of the disease but fail to reduce shedding of the challenge virus increasing the likelihood of outbreaks. At the moment, several new strategies are being evaluated to improve both live attenuated and viral vector vaccines. Potential new live vaccines attenuated by deletion of genes associated with virulence or by selection of CEO viral subpopulations that do not exhibit increased virulence upon passages in birds are being evaluated. Also new vector alternatives to express GaHV-1 glycoproteins in Newcastle diseases virus (NDV) or in modified very virulent (vv) serotype I Marek’s disease virus (MDV) were developed and evaluated.

Live virus vaccines based on a vesicular stomatitis virus (VSV) backbone: Standardized template with key considerations for a risk/benefit assessment

The Brighton Collaboration Viral Vector Vaccines Safety Working Group (V3SWG) was formed to evaluate the safety of live, recombinant viral vaccines incorporating genes from heterologous viral and other microbial pathogens in their genome (so-called “chimeric virus vaccines”). Many such viral vector vaccines are now at various stages of clinical evaluation. Here, we introduce an attenuated form of recombinant vesicular stomatitis virus (rVSV) as a potential chimeric virus vaccine for HIV-1, with implications for use as a vaccine vector for other pathogens. The rVSV/HIV-1 vaccine vector was attenuated by combining two major genome modifications. These modifications acted synergistically to greatly enhance vector attenuation and the resulting rVSV vector demonstrated safety in sensitive mouse and non-human primate neurovirulence models. This vector expressing HIV-1 gag protein has completed evaluation in two Phase I clinical trials. In one trial the rVSV/HIV-1 vector was administered in a homologous two-dose regimen, and in a second trial with pDNA in a heterologous prime boost regimen. No serious adverse events were reported nor was vector detected in blood, urine or saliva post vaccination in either trial. Gag specific immune responses were induced in both trials with highest frequency T cell responses detected in the prime boost regimen. The rVSV/HIV-1 vector also demonstrated safety in an ongoing Phase I trial in HIV-1 positive participants. Additionally, clinical trial material has been produced with the rVSV vector expressing HIV-1 env, and Phase I clinical evaluation will initiate in the beginning of 2016. In this paper, we use a standardized template describing key characteristics of the novel rVSV vaccine vectors, in comparison to wild type VSV. The template facilitates scientific discourse among key stakeholders by increasing transparency and comparability of information. The Brighton Collaboration V3SWG template may also be useful as a guide to the evaluation of other recombinant viral vector vaccines.

Adventitious agents and live viral vectored vaccines: Considerations for archiving samples of biological materials for retrospective analysis

Vaccines are one of the most effective public health medicinal products with an excellent safety record. As vaccines are produced using biological materials, there is a need to safeguard against potential contamination with adventitious agents. Adventitious agents could be inadvertently introduced into a vaccine through starting materials used for production. Therefore, extensive testing has been recommended at specific stages of vaccine manufacture to demonstrate the absence of adventitious agents. Additionally, the incorporation of viral clearance steps in the manufacturing process can aid in reducing the risk of adventitious agent contamination. However, for live viral vaccines, aside from possible purification of the virus or vector, extensive adventitious agent clearance may not be feasible.In the event that an adventitious agent is detected in a vaccine, it is important to determine its origin, evaluate its potential for human infection and pathology, and discern which batches of vaccine may have been affected in order to take risk mitigation action. To achieve this, it is necessary to have archived samples of the vaccine and ancillary components, ideally from developmental through to current batches, as well as samples of the biological materials used in the manufacture of the vaccine, since these are the most likely sources of an adventitious agent. The need for formal guidance on such vaccine sample archiving has been recognized but not fulfilled. We summarize in this paper several prior major cases of vaccine contamination with adventitious agents and provide points for consideration on sample archiving of live recombinant viral vector vaccines for use in humans.