Vector-based Vaccines Research Articles

Recent Advances in Designing Adeno-Associated Virus-Based Vaccines Against Viral Infections

Over 80% of the world’s deadliest pandemics are caused by viral infections, and vaccination remains the most effective way to prevent these infections from spreading. Since the discovery of the first vaccine over two centuries ago, several vaccine design technologies have been developed. Next-generation vaccines, based on mRNA and viral vector technologies, have recently emerged as alternatives to traditional vaccines. Adenoviral vector-based vaccines against coronavirus disease 2019 have demonstrated a more sustained antibody response as compared to mRNA vaccines. However, this has not been without complications, with a few cases of severe adverse events identified in vaccinated individuals, and the underlying mechanism is the subject of intense investigation. Adeno-associated viral vectors induce a weaker cellular immune response compared to adenoviral vectors, and it is mainly for this reason that there has been a diminished interest in exploring them as a vaccine platform until recently. This review will discuss recent developments and the potential of adeno-associated viral vectors as anti-viral vaccines.

Repeated COVID-19 mRNA-based vaccination contributes to SARS-CoV-2 neutralizing antibody responses in the mucosa.

To prevent infection by respiratory viruses and consequently limit virus circulation, vaccines need to promote mucosal immunity. The extent to which the currently used messenger RNA (mRNA)-based COVID-19 vaccines induce mucosal immunity remains poorly characterized. We evaluated mucosal neutralizing antibody responses in a cohort of 183 individuals. Participants were sampled at several time points after primary adenovirus vector-based or mRNA-based COVID-19 vaccination and after mRNA-based booster vaccinations. Our findings revealed that repeated vaccination with mRNA boosters promoted severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibodies in nasal secretions. Nasal and serum neutralizing antibody titers of both IgG and IgA isotypes correlated to one another. We investigated the source of these mucosal antibodies in a mouse model wherein mice received repeated mRNA vaccines for SARS-CoV-2. These experiments indicated that neutralizing antibody-producing cells reside in the spleen and bone marrow, whereas no proof of tissue homing to the respiratory mucosa was observed, despite the detection of mucosal antibodies. Serum transfer experiments confirmed that circulating antibodies were able to migrate to the respiratory mucosa. Collectively, these results demonstrate that, especially upon repeated vaccination, the currently used COVID-19 mRNA vaccines can elicit mucosal neutralizing antibodies and that vaccination might also stimulate mucosal immunity induced by previous SARS-CoV-2 infection. Moreover, migration of circulating antibodies to the respiratory mucosa might be a main mechanism. These findings advance our understanding of mRNA vaccine-induced immunity and have implications for the design of vaccine strategies to combat respiratory infections.

Impact of Knowledge, Attitudes, And Perceptions Regarding the Covid-19 Vaccine Among Students at A Tertiary Institution in Kenya

COVID-19 vaccination was authorized as a preventive measure due to its proven effectiveness in reducing infection, severity, and mortality rates. mRNA-based vaccines, such as the Pfizer-BioNTech and Moderna vaccines, work by utilizing a small piece of the virus's genetic material called messenger RNA (mRNA). Viral vector-based vaccines, such as the Oxford-AstraZeneca and Johnson & Johnson vaccines, use a harmless virus to deliver a modified version of the SARS-CoV-2 virus's genetic material into cells. As of June 2021, COVID-19 vaccines approved to be safe and effective by the WHO included: AstraZeneca (oxford vaccine), Johnson and Johnson, Pfizer (BioNTech), Moderna, Sinopharm, and Sinovac. Both mRNA-based and viral vector-based vaccines have shown high efficacy in preventing COVID-19 and reducing the severity of the disease. We assessed how knowledge, attitudes, and perceptions of COVID-19 vaccines influenced uptake by students at a tertiary institution in Kenya. This was a descriptive cross-sectional study conducted in Kabarak University-Main Campus. The sampling procedure employed was the convenience sampling method. The data was collected via a self-administered questionnaire on 385 students and analyzed using SPSS. Vaccination was not entirely successful (at threshold) in Kenya due to insufficient public education (benefits or side effects); inadequate health care professionals; myths & misconceptions (including the risk of infertility), opinions & beliefs (clinical trials short time to detect long term side effects like malignancies); resistance (fear for death or infection, fear of expired vaccines administration); mistrust on government (forced, threats by leaders, a charade to donations, benefits government, research on Kenyans) & mistrust on the sources of vaccines (China, Russia), reluctance, procrastination, negligence & ignorance (not embraced, negative attitude to westernization, the pandemic is over!); infection even after being vaccinated and the dosage forms available injection, fear for syringes, oral preferred. The study results revealed that 15.1% strongly agreed that a vaccine is important to end the COVID-19 pandemic; 33.5% agreed that a vaccine is important to end the COVID-19 pandemic; 33.2% were undecided that a vaccine is important to end the COVID-19 pandemic. The study findings showed that 53.0% had been vaccinated as compared to 47.0% who had not been vaccinated. That is medical students (pharmacy and medicine) had higher rates of vaccine uptake compared to Engineering students.

Induction of neutralizing antibody responses by AAV5-based vaccine for respiratory syncytial virus in mice.

Respiratory Syncytial Virus (RSV) is a significant cause of respiratory illnesses worldwide, particularly in infants and elderly individuals. Despite the burden RSV imposes, effective preventive measures are limited. The research application of adeno-associated virus (AAV) in vaccine platforms has been expanding, and its potential in prevention and treatment has garnered much attention. In this study, we explored the potential application of a recombinant adeno-associated virus 5 (rAAV5) vector-based RSV vaccine, focusing on the expression of the pre-fusion (Pre-F) protein structure. Through intramuscular immunization in mice. The immunogenicity of the vaccine was evaluated in Balb/c mice immunized intramuscularly and intranasal, respectively. The rAAV5-RSV-Fm vaccine demonstrated positive humoral and induced antibody titers against RSV strains A and B for up to 120 days post-immunization. Notably, intranasal administration also elicited protective antibodies. Characterization studies confirmed the ability of the vac-cine to express the Pre-F protein and its superior immunogenicity compared to that of full-length F protein. These findings underscore the potential application of rAAV5 vector platforms in RSV vaccine development and further investigation into their protective efficacy is warranted.

A novel orf virus vector-based COVID-19 booster vaccine shows cross-neutralizing activity in the absence of anti-vector neutralizing immunity

ABSTRACT Next-generation COVID-19 vaccines are being developed to expand the breadth of coverage against existing and future variants and to extend the duration of protection. Prime-2-CoV_Beta is an orf virus (ORFV) based multi-antigen COVID-19 vaccine that co-expresses Spike (S) and Nucleocapsid (N) antigens. The safety and immunogenicity of Prime-2-CoV_Beta is investigated in a phase 1 first-in-human (FIH) dose-finding trial (ORFEUS study, ClinicalTrials.gov: NCT05367843). Participants of two age groups (18–55 and 65–85 years) who previously completed at least two doses of mRNA vaccines were enrolled and sequentially assigned to different dose groups to receive one intramuscular dose of 3 × 105, 3 × 106, 1.5 × 107, or 3 × 107 plaque-forming units (PFU) of Prime-2-CoV_Beta on day 1 and a second dose on day 29. Here, we report safety and immunogenicity data collected up to 6 months after the first study vaccination. Prime-2-CoV_Beta is safe and well tolerated and elicits immune responses at higher dose levels in participants aged 18–55. A single dose of 3 × 107 PFU boosted binding and cross-neutralizing antibody responses that are maintained through 6 months after the first booster vaccination. Polyfunctional S-specific CD4+ and CD8+ T cell responses are observed after vaccination. No pre-existing or vaccine-induced neutralizing anti-vector antibodies are detected. Our findings highlight the potential of the ORFV vector as a safe platform for future vaccine design, which provides the ability to deliver multiple antigens and allows for repeat immunization.

A single dose of an ALVAC vector-based RABV virus-like particle candidate vaccine induces a potent immune response in mice, cats and dogs

Rabies, caused by the Rabies virus (RABV), is a highly fatal zoonotic disease. Existing rabies vaccines have demonstrated good immune efficacy, but the complexity of immunization procedures and high cost has impeded the elimination of RABV, particularly in the post-COVID-19 era. There is a pressing need for safer and more effective rabies vaccines that streamline vaccination protocols and reduce expense. To meet this need, we have developed a potential rabies vaccine candidate called ALVAC-RABV-VLP, utilizing CRISPR/Cas9 gene editing technology. This vaccine employs a canarypox virus vector (ALVAC) to generate RABV virus-like particles (VLPs). In mice, a single dose of ALVAC-RABV-VLP effectively activated dendritic cells (DCs), follicular helper T cells (Tfh), and the germinal center (GC)/plasma cell axis, resulting in durable and effective humoral immune responses. The survival rate of mice challenged with lethal RABV was 100%. Similarly, in dogs and cats, a single immunization with ALVAC-RABV-VLP elicited a stronger and longer-lasting antibody response. ALVAC-RABV-VLP induced superior cellular and humoral immunity in both mice and beagles compared to the commercial inactivated rabies vaccine. In conclusion, ALVAC-RABV-VLP induced robust protective immune responses in mice, dogs and cats, offering a novel, cost-effective, efficient, and promising approach for herd prevention of rabies.

Subsequent Vaccination against SARS-CoV-2 after Vaccine-Induced Immune Thrombotic Thrombocytopenia.

Background: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare but severe complication following vaccination with adenovirus vector-based COVID-19 vaccines. Antibodies directed against platelet factor 4 (PF4) are thought to be responsible for platelet activation and subsequent thromboembolic events in these patients. Since a single vaccination does not lead to sufficient immunization, subsequent vaccinations against COVID-19 have been recommended. However, concerns exist regarding the possible development of a new thromboembolic episode after subsequent vaccinations in VITT patients. Methods: We prospectively analyzed follow-up data from four VITT patients (three women and one man; median age, 44 years [range, 22 to 62 years]) who subsequently received additional COVID-19 vaccines. Platelet counts, anti-PF4/heparin antibody level measurements, and a functional platelet activation assay were performed at each follow-up visit. Additionally, we conducted a literature review and summarized similar reports on the outcome of subsequent vaccinations in patients with VITT. Results: The patients had developed thrombocytopenia and thrombosis 4 to 17 days after the first vaccination with ChAdOx1 nCoV-19. The optical densities (ODs) of anti-PF4/heparin antibodies decreased with time, and three out of four patients tested negative within 4 months. One patient remained positive even after 10 months post first vaccination. All four patients received an mRNA-based vaccine as a second vaccination against SARS-CoV-2. No significant drop in platelet count or new thromboembolic complications were observed during follow-up. We identified seven publications reporting subsequent COVID-19 vaccination in VITT patients. None of the patients developed thrombocytopenia or thrombosis after the subsequent vaccination. Conclusion: Subsequent vaccination with an mRNA vaccine appears to be safe in VITT patients.

Revolutionizing Veterinary Health with Viral Vector-Based Vaccines.

Vaccines signify one of the economical and reasonable means to prevent and eradicate the important infectious diseases. Conventional vaccines like live attenuated and inactivated vaccines comprise of whole pathogen either in attenuated or killed form. While, new generation vaccines have been designed to elicit immune response by genetically modifying only the nucleic acid portion of that pathogen. These new generation therapeutics include mRNA vaccines, DNA plasmid vaccines, chimeric vaccines and recombinant viral vector-based vaccines. Nucleic acid based vaccines use genetic material itself thus, they are highly stable and potent in nature to induce long-lasting immune response. Amongst these novel vaccine platforms, viral vector-based vaccines is one such emerging field which has proven to be extremely effective and potent. Nowadays, veterinary medicine has also accepted this innovative vectored vaccine platform to develop an effective control strategy against certain important viral diseases of animals. Viral vector-based vaccine uses various DNA and RNA viruses of human or animal origin to carry an immunogenic transgene of target pathogen. These vaccines enhance both humoral and cell mediated immune response without use of any accessory immune-stimulants. Till today, several viruses have been modified to be characterized as vaccine vectors. Currently, large number of research programs are going on to develop vectored vaccines and novel viral vector for veterinary use. In the present review, different kinds of viral vectored vaccines having veterinary importance have been discussed.

Developing Vaccines in Pancreatic Adenocarcinoma: Trials and Tribulations.

Pancreatic adenocarcinoma represents one of the most challenging malignancies to treat, with dismal survival rates despite advances in therapeutic modalities. Immunotherapy, particularly vaccines, has emerged as a promising strategy to harness the body's immune system in combating this aggressive cancer. This abstract reviews the trials and tribulations encountered in the development of vaccines targeting pancreatic adenocarcinoma. Key challenges include the immunosuppressive tumor microenvironment, the heterogeneity of tumor antigens, and a limited understanding of immune evasion mechanisms employed by pancreatic cancer cells. Various vaccine platforms, including peptide-based, dendritic cell-based, and viral vector-based vaccines, have been explored in preclinical and clinical settings. However, translating promising results from preclinical models to clinical efficacy has proven elusive. In recent years, mRNA vaccines have emerged as a promising immunotherapeutic strategy in the fight against various cancers, including pancreatic adenocarcinoma. We will discuss the potential applications, opportunities, and challenges associated with mRNA vaccines in pancreatic cancer treatment.

Viral Vector-Based Chlamydia trachomatis Vaccines Encoding CTH522 Induce Distinct Immune Responses in C57BL/6J and HLA Transgenic Mice.

Chlamydia trachomatis remains a major global health problem with increasing infection rates, requiring innovative vaccine solutions. Modified Vaccinia Virus Ankara (MVA) is a well-established, safe and highly immunogenic vaccine vector, making it a promising candidate for C. trachomatis vaccine development. In this study, we evaluated two novel MVA-based recombinant vaccines expressing spCTH522 and CTH522:B7 antigens. Our results show that while both vaccines induced CD4+ T-cell responses in C57BL/6J mice, they failed to generate antigen-specific systemic CD8+ T cells. Only the membrane-anchored CTH522 elicited strong IgG2b and IgG2c antibody responses. In an HLA transgenic mouse model, both recombinant MVAs induced Th1-directed CD4+ T cell and multifunctional CD8+ T cells, while only the CTH522:B7 vaccine generated antibody responses, underscoring the importance of antigen localization. Collectively, our data indicate that distinct antigen formulations can induce different immune responses depending on the mouse strain used. This research contributes to the development of effective vaccines by highlighting the importance of careful antigen design and the selection of appropriate animal models to study specific vaccine-induced immune responses. Future studies should investigate whether these immune responses provide protection in humans and should explore different routes of immunization, including mucosal and systemic immunization.

Intranasal Administration of Recombinant Newcastle Disease Virus Expressing SARS-CoV-2 Spike Protein Protects hACE2 TG Mice against Lethal SARS-CoV-2 Infection.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), emerged as a global outbreak in 2019, profoundly affecting both human health and the global economy. Various vaccine modalities were developed and commercialized to overcome this challenge, including inactivated vaccines, mRNA vaccines, adenovirus vector-based vaccines, and subunit vaccines. While intramuscular vaccines induce high IgG levels, they often fail to stimulate significant mucosal immunity in the respiratory system. We employed the Newcastle disease virus (NDV) vector expressing the spike protein of the SARS-CoV-2 Beta variant (rK148/beta-S), and evaluated the efficacy of intranasal vaccination with rK148/beta-S in K18-hACE2 transgenic mice. Intranasal vaccination with a low dose (106.0 EID50) resulted in an 86% survival rate after challenge with the SARS-CoV-2 Beta variant. Administration at a high dose (107.0 EID50) led to a reduction in lung viral load and 100% survival against the SARS-CoV-2 Beta and Delta variants. A high level of the SARS-CoV-2 spike-specific IgA was also induced in vaccinated mice lungs following the SARS-CoV-2 challenge. Our findings suggest that rK148/beta-S holds promise as an intranasal vaccine candidate that effectively induces mucosal immunity against SARS-CoV-2.

Trends in Viral Vector-Based Vaccines for Tuberculosis: A Patent Review (2010-2023).

Tuberculosis (TB) is an ancient global public health problem. Several strategies have been applied to develop new and more effective vaccines against TB, from attenuated or inactivated mycobacteria to recombinant subunit or genetic vaccines, including viral vectors. This review aimed to evaluate patents filed between 2010 and 2023 for TB vaccine candidates. It focuses on viral vector-based strategies. A search was carried out in Espacenet, using the descriptors "mycobacterium and tuberculosis" and the classification A61K39. Of the 411 patents preliminarily identified, the majority were related to subunit vaccines, with 10 patents based on viral vector platforms selected in this study. Most of the identified patents belong to the United States or China, with a concentration of patent filings between 2013 and 2023. Adenoviruses were the most explored viral vectors, and the most common immunodominant Mycobacterium tuberculosis (Mtb) antigens were present in all the selected patents. The majority of patents were tested in mouse models by intranasal or subcutaneous route of immunization. In the coming years, an increased use of this platform for prophylactic and/or therapeutic approaches for TB and other diseases is expected. Along with this, expanding knowledge about the safety of this technology is essential to advance its use.

Update on Hepatitis C Virus (HCV) Vaccine Candidates in Clinical Trials: A Systematic Literature Review

Introduction: Hepatitis C virus (HCV) infection remains a significant global health challenge, affecting over 71 million people worldwide and leading to severe liver diseases such as cirrhosis and hepatocellular carcinoma (HCC). Despite the availability of highly effective direct-acting antiviral (DAA) therapies achieving sustained virologic response (SVR) rates exceeding 90%, high costs and limited accessibility impede global eradication efforts. Additionally, DAAs do not confer immunity against reinfection, highlighting the need for a prophylactic vaccine. Methods: This systematic literature review follows the PRISMA guidelines. A comprehensive search was conducted in PubMed, Scopus, and Web of Science for articles published between January 2010 and March 2024, focusing on HCV vaccine candidates in clinical trials. Data on study characteristics, participant demographics, vaccine characteristics, vaccine platforms and key outcomes were extracted. Results: Nine studies met the eligibility criteria, covering various phases of clinical trials (Phase I, II, and II/III). Key findings included: Vaccine platforms: The studies primarily utilized three types of vaccine platforms: Viral Vector-Based Vaccines, Peptide-Based Vaccines and Recombinant Protein Vaccines Immunogenicity: Vaccines targeting non-structural proteins (NS3, NS4, NS5) induced robust T-cell responses. Chimpanzee adenovirus (ChAd) and Modified Vaccinia Ankara (MVA) vector-based vaccines showed high polyfunctional CD8+ and CD4+ T-cell levels. Safety: Most adverse events were mild to moderate, including flu-like symptoms and injection site reactions. Severe adverse events were noted with TG4040 when combined with PEG-IFNα and RBV. Efficacy: Significant reductions in viral load and improvements in liver function were reported. Personalized peptide vaccines demonstrated enhanced immune responses and improved overall survival in HCV-positive advanced HCC patients. Conclusion: HCV vaccine development has made significant strides, with several candidates demonstrating strong immunogenicity, acceptable safety, and promising efficacy in clinical trials. Continued research is essential to address challenges such as viral genetic variability, durability of immune responses, and global accessibility.

A Simple and Versatile Method for Ex Vivo Monitoring of Goat Vaginal Mucosa Transduction by Viral Vector Vaccines.

Goat may represent a valid large animal model for human pathogens and new vaccines testing. Appropriate vaccine administration is a critical component of a successful immunization program. The wrong route of administration may reduce the efficacy of the vaccine, whereas the proper administration strategy can enhance it. Viral vectors have been employed successfully for goat and sheep immunization; however, no data concerning the vaginal route are available. A viral vector's ability to transduce the site of inoculation is of primary interest. In this study, a fast and reliable ex vivo assay for testing the transduction capability of an Ad5-based vector when intravaginally administered was developed. An Ad5 vector delivering an expression cassette with a bicistronic reporter gene, Ad5-CMV-turboGFP-IRES-Luc2, was constructed. We demonstrated Ad5-CMV-turboGFP-IRES-Luc2's ability to transduce caprine vaginal mucosa by ex vivo bioluminescent imaging (BLI) employing a simple CCD camera apparatus for chemiluminescence western immunoblotting. These data, though simple, provide valuable insights into developing a vaginal immunization strategy using a viral vector-based vaccine to protect against pathogens causing genital diseases.

Development of multidose thermotolerant formulations of a vector-based Covid-19 vaccine candidate, NDV-HXP-S in different product formats: Stability and preservative efficacy study

Current lead coronavirus vaccines require continuous cold or ultra-cold storage from the manufacturing site to the field to maintain protective efficacy. Since cold chain capacity is limited and complex, logistics planning is crucial to limit vaccine wastage.[1] The restrictive storage concerns also make it difficult to share vaccines between public health departments and neighboring states, leading to increased vaccine wastage.[2] A Newcastle Disease Virus (NDV) vector-based severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) vaccine candidate, NDV-HXP-S, offers a cost-effective alternative which aims to improve global access to SARS CoV-2 vaccines.[3] The NDV-HXP-S vaccine candidate can be mass-produced in chicken eggs and has demonstrated efficacy in preclinical studies, as well as acceptable safety andpotent immunogenicity in clinical studies.[3,4–10] To further advance the NDV-HXP-S vaccine candidate, this manuscript describes work focused on the development of multidose thermotolerant vaccine formulations (i.e., those which would not require continuous extendedrefrigeration), making it convenient to use and store, and simplifying transport and distribution logistics, especially in outbreak settings. Liquid and lyophilized formulations for parenteral administration were rigorously screened for the vaccine formulation’s ability to maintain S-antigen stability after exposure to temperaturestress at 40 °C, 25 °C, and 2 °C to 8 °C storage for six months. Preservative efficacy was evaluated to enable a multidose liquid vaccine format as well as endotoxin testing in lyophilized formulations. Lead liquid vaccine formations were identified that were able to maintain S-antigen content at 2 °C to 8 °C and 25 °C storage for the entire six-month study. Lead lyophilized vaccine formulations were identified which were able to maintain S-antigen content for six months at 2 °C to 8 °C, 25 °C, and 40 °C. Both the liquid and lyophilized formulations identified are improved thermotolerant SARS-CoV-2 vaccine formulations.

The Central Conserved Peptides of Respiratory Syncytial Virus G Protein Enhance the Immune Response to the RSV F Protein in an Adenovirus Vector Vaccine Candidate.

Respiratory syncytial virus (RSV) is a serious human respiratory pathogen that commonly affects children, older adults, and immunocompromised individuals. At present, the design of licensed vaccines focuses on the incorporation of the pre-fusion protein (PreF protein) of RSV, as this protein has the ability to induce antibodies that offer a high level of protection. Moreover, the G protein contains the CX3C motif that binds the chemokine receptor CX3CR1 in respiratory epithelial cells, which plays an essential role in viral infection. Therefore, incorporating the G antigen into vaccine design may prove more advantageous for RSV prevention. In this study, we developed a human adenoviral vector-based RSV vaccine containing highly neutralizing immunogens, a modified full-length PreF protein fused with the central conserved peptides of the G protein (Gcc) from both RSV subgroups trimerized via a C-terminal foldon, and evaluated its immune response in mice through intranasal (i.n.) immunization. Our results showed that immunization with Ad5-PreF-Qa-Gcc elicited a balanced Th1/Th2 immune response and robust mucosal immunity with higher neutralizing antibody titers against RSV Long and RSV B1. Importantly, immunization with Ad5-PreF-Qa-Gcc enhanced CD4+ CD25+ FoxP3+ Treg cell response and protected the mice against RSV infection. Our data demonstrate that the combination of Gcc and the PreF antigen is a viable strategy for developing effective RSV vaccines.

Immunogenicity and Protective Efficacy of a Single Intranasal Dose Vectored Vaccine Based on Sendai Virus (Moscow Strain) against SARS-CoV-2 Variant of Concern.

The mouse paramyxovirus Sendai, which is capable of limited replication in human bronchial epithelial cells without causing disease, is well suited for the development of vector-based intranasal vaccines against respiratory infections, including SARS-CoV-2. Using the Moscow strain of the Sendai virus, we developed a vaccine construct, Sen-Sdelta(M), which expresses the full-length spike (S) protein of the SARS-CoV-2 delta variant. A single intranasal delivery of Sen-Sdelta(M) to Syrian hamsters and BALB/c mice induced high titers of virus-neutralizing antibodies specific to the SARS-CoV-2 delta variant. A significant T-cell response, as determined by IFN-γ ELISpot and ICS methods, was also demonstrated in the mouse model. Mice and hamsters vaccinated with Sen-Sdelta(M) were well protected against SARS-CoV-2 challenge. The viral load in the lungs and nasal turbinates, measured by RT-qPCR and TCID50 assay, decreased dramatically in vaccinated groups. The most prominent effect was revealed in a highly sensitive hamster model, where no tissue samples contained detectable levels of infectious SARS-CoV-2. These results indicate that Sen-Sdelta(M) is a promising candidate as a single-dose intranasal vaccine against SARS-CoV-2, including variants of concern.

Long-term humoral and cellular responses elicited by Gam-COVID-Vac vaccine in hemodialysis patients: A prospective cohort study

<b>Purpose: </b>The aim of this study is to assess long-term immunogenicity of the recombinant adenoviruses 26 and 5 vector-based COVID-19 vaccine Gam-COVID-Vac (Sputnik V, developed by N. F. Gamaleya National Research Centre, Russia) in patients receiving maintenance hemodialysis (HD) compared to healthy subjects.<br /> <b>Materials & methods: </b>A prospective cohort study included patients treated with maintenance HD (n=23) and healthy volunteers (n=28). The levels of anti-severe acute respiratory syndrome coronavirus-2 specific IgG as well as specific T-cell responses were quantified in all participants at two time points: one and six months after complete vaccination. All participates were adults, had been vaccinated twice with Gam-COVID-Vac and had no prior history of confirmed COVID-19.<br /> <b>Results: </b>In both groups, IgG levels decreased from month one to six, however, antibodies did not decline more rapidly in HD group (analysis of variance p=0.7214 for the “time×group” interaction, non-adjusted model). At the end of the study, 48.0% of non-HD and 67.0% of HD participants showed T-cell positivity. T-spot counts dropped over time in non-HD controls, but not in HD subjects (p=0.0080 and p=0.1800, respectively).<br /> <b>Conclusions: </b>Patients receiving HD maintain significant long-term humoral response after Gam-COVID-Vac vaccination, which is comparable to that in subjects with normal kidney function. Cellular response turned up to be more sustained over time in HD group.

Monitoring of adaptive immune responses in healthcare workers who received a Coronavirus disease 2019 vaccine booster dose.

Coronavirus disease 2019 (COVID-19) has become a global pandemic and led to increased mortality and morbidity. Vaccines against the etiologic agent; severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) were approved for emergency use on different platforms. In the early phase of the pandemic, Thai healthcare workers (HCWs) received CoronaVac, an inactivated vaccine, as the first vaccine against SARS-CoV-2, followed by ChAdOx1 nCoV-19, a viral vector-based vaccine, or BNT162b2, an mRNA vaccine, as a booster dose. This preliminary study evaluated the immunogenicity of ChAdOx1 nCoV-19 and BNT162b2 as a booster dose in HCWs who previously received two doses of CoronaVac. Ten HCW participants received ChAdOx1 nCoV-19 and another 10 HCWs received BNT162b2 as a booster dose after two doses of CoronaVac. Anti-RBD IgG, neutralizing antibodies (NAb), and cellular immunity, including interferon-gamma (IFN-γ)-releasing CD4, CD8, double negative T cells, and NK cells, were measured at 3 and 5 months after the booster dose. There was no significant difference in anti-RBD IgG levels at 3 and 5 months between the two different types of booster vaccine. The levels of anti-RBD IgG and NAb were significantly decreased at 5 months. HCWs receiving BNT162b2 had significantly higher NAb levels than those receiving ChAdOx1 nCoV-19 at 5 months after the booster dose. IFN-γ release from CD4 T cells was detected at 3 months with no significant difference between the two types of booster vaccines. However, IFN-γ-releasing CD4 T cells were present at 5 months in the ChAdOx1 nCoV-19 group only. ChAdOx1 nCoV-19 or BNT162b2 can be used as a booster dose after completion of the primary series primed by inactivated vaccine. Although the levels of immunity decline at 5 months, they may be adequate during the first 3 months after the booster dose.

Development of a Recombinant Live Attenuated Influenza Vaccine Virus Expressing Pneumococcal Surface Antigen A as a Strategy for Combined Protection Against Influenza and Bacterial Coinfection Caused by Streptococcus pneumoniae

Introduction Bacterial superinfection with Streptococcus pneumoniae following the influenza virus infection complicates the course of the disease and is a major cause of mortality during influenza virus epidemics. The effectiveness of licensed polysaccharide vaccines is limited by the serotypes included in the vaccine and possible immune tolerance during revaccination. Pneumococcal surface protein A (PspA), which includes conserved regions and has at least two functions in pathogen virulence, is considered a promising target for the development of new-generation vaccines, including gene-engineering constructions. Therefore, the development of an influenza virus vector-based vaccine expressing conserved bacterial proteins seems to be a promising strategy for designing combined vaccines against influenza and bacterial pathogens. Methods A recombinant live attenuated influenza virus (LAIV) expressing PspA fragment in a modified hemagglutinin was rescued on the A/Leningrad/134/17/57 (H2N2) backbone. This recombinant virus was assessed for its growth characteristics in vitro, as well as for its immunogenicity and protective capacity, using a mouse model of influenza-bacterial coinfection. Results The rescued recombinant LAIV/HA+PspA virus was genetically stable after sequential passaging in embryonated chicken eggs and possessed an attenuated phenotype similar to the classical LAIV strain. The LAIV/HA+PspA bivalent vaccine-induced IgG antibodies specific to both influenza virus and S. pneumoniae and provided complete protection of vaccinated mice against lethal influenza infection, as well as a 40% survival rate for lethal homologous and heterologous influenza infection complicated by concomitant bacterial infection with S. pneumoniae. Conclusion The presented design of a recombinant influenza virus carrying immunogenic fragments of a bacterial pathogen can be considered a promising strategy for the combined protection of vaccinated individuals against influenza and its bacterial complications, and further in-depth studies of such recombinant viruses in preclinical studies are warranted.