Prime-boost Combinations Research Articles

Effectiveness of VSV vectored SARS-CoV-2 spike when administered through intranasal, intramuscular or a combination of both

A critical feature of the VSV vector platform is the ability to pseudotype the virus with different glycoproteins from other viruses, thus altering cellular tropism of the recombinant virus. The route of administration is critical in triggering local and systemic immune response and protection. Most of the vaccine platforms used at the forefront are administered by intramuscular injection. However, it is not known at what level ACE2 is expressed on the surface of skeletal muscle cells, which will have a significant impact on the efficiency of a VSV-SARS-CoV-2 spike vaccine to mount a protective immune response when administered intramuscularly. In this study, we investigate the immunogenicity and efficacy of a prime-boost immunization regimen administered intranasally (IN), intramuscularly (IM), or combinations of the two. We determined that the prime-boost combinations of IM followed by IN immunization (IM + IN) or IN followed by IN immunization (IN + IN) exhibited strong spike-specific IgG, IgA and T cell response in vaccinated K18 knock-in mice. Hamsters vaccinated with two doses of VSV expressing SARS-CoV-2 spike, both delivered by IN or IM + IN, showed strong protection against SARS-CoV-2 variants of concern Alpha and Delta. This protection was also observed in aged hamsters. Our study underscores the highly crucial role immunization routes have with the VSV vector platform to elicit a strong and protective immune response.

An MVA-based vector expressing cell-free ISG15 increases IFN-I production and improves HIV-1-specific CD8 T cell immune responses.

The human immunodeficiency virus (HIV), responsible of the Acquired Immune Deficiency Syndrome (AIDS), continues to be a major global public health issue with any cure or vaccine available. The Interferon-stimulated gene 15 (ISG15) encodes a ubiquitin-like protein that is induced by interferons and plays a critical role in the immune response. ISG15 is a modifier protein that covalently binds to its targets via a reversible bond, a process known as ISGylation, which is the best-characterized activity of this protein to date. However, ISG15 can also interact with intracellular proteins via non-covalent binding or act as a cytokine in the extracellular space after secretion. In previous studies we proved the adjuvant effect of ISG15 when delivered by a DNA-vector in heterologous prime-boost combination with a Modified Vaccinia virus Ankara (MVA)-based recombinant virus expressing HIV-1 antigens Env/Gag-Pol-Nef (MVA-B). Here we extended these results evaluating the adjuvant effect of ISG15 when expressed by an MVA vector. For this, we generated and characterized two novel MVA recombinants expressing different forms of ISG15, the wild-type ISG15GG (able to perform ISGylation) or the mutated ISG15AA (unable to perform ISGylation). In mice immunized with the heterologous DNA prime/MVA boost regimen, the expression of the mutant ISG15AA from MVA-Δ3-ISG15AA vector in combination with MVA-B induced an increase in the magnitude and quality of HIV-1-specific CD8 T cells as well as in the levels of IFN-I released, providing a better immunostimulatory activity than the wild-type ISG15GG. Our results confirm the importance of ISG15 as an immune adjuvant in the vaccine field and highlights its role as a potential relevant component in HIV-1 immunization protocols.

Heterologous prime-boost vaccine using antigen-loaded microparticles and adenovirus (encoding antigen) enhances cellular immune responses and antitumor activity

Heterologous prime-boost vaccines have the potential to promote higher immune responses than homologous prime-boost vaccines and were used in this murine study to investigate the effect on the magnitude of the cellular (and humoral) antigen-specific immune responses and antitumor efficacy when a microparticle formulation (prime) is combined with an adenoviral vaccine (boost). Specifically, the prime comprised chick egg ovalbumin (OVA; 25 µg/dose), used here as a model tumor antigen (TA), encapsulated in microparticles (∼700 nm diameter) made from the biodegradable polymer, 50:50 poly(lactic-co-glycolic acid) (PLGA); while attenuated adenovirus (type 5) encoding OVA (Ad5OVA; 108 PFU/dose) was employed as the boost. The ability of OVA-loaded microparticles to enhance OVA-specific antibody responses, OVA-specific CD3 + CD8 + T cell responses and antitumor activity (i.e., protection against OVA-expressing tumor-challenge) to the heterologous prime-boost vaccine was investigated; and it was found that this prime-boost combination could significantly enhance OVA-specific cellular responses compared to all other vaccination groups and was the only group to confer a significant survival advantage over the unvaccinated group (naïve) in a prophylactic animal tumor model. This finding illustrates the potential for combining TA-loaded PLGA-based microparticles with other vaccine formats to improve tumor-specific cellular immune responses.

Immunogenicity and Safety of Homologous and Heterologous Prime-Boost of CoronaVac® and ChAdOx1 nCoV-19 among Hemodialysis Patients: An Observational Prospective Cohort Study.

Vaccines that prevent SARS-CoV-2 infection are considered the most promising approach to modulating the pandemic. There is scarce evidence on the efficacy and safety of different vaccine prime-boost combinations in MHD patients since most clinical trials have used homologous mRNA vaccine regimens. This prospective observational study assessed the immunogenicity and safety of homologous CoronaVac® (SV-SV), ChAdOx1 nCoV-19 (AZD1222) (AZ-AZ), and the heterologous prime-boost of SV-AZ, among MHD patients. A total of 130 MHD participants were recruited. On day 28, after the second dose, seroconversion results of the surrogate virus neutralization test were not different between vaccine regimens. The magnitude of the receptor-binding domain-specific IgG was highest among the SV-AZ. Different vaccine regimens had a distinct impact on seroconversion, for which the heterologous vaccine regimen demonstrated a higher probability of seroconversion (OR 10.12; p = 0.020, and OR 1.81; p = 0.437 for SV-AZ vs. SV-SV, and SV-AZ vs. AZ-AZ, respectively). There were no serious adverse events reported in any of the vaccine groups. Immunization with SV-SV, AZ-AZ, and SV-AZ could generate humoral immunity without any serious adverse events among MHD patients. Using the heterologous vaccine prime-boost seemed to be more efficacious in terms of inducing immunogenicity.

Response to HIV-1 gp160-carrying recombinant virus HSV-1 and HIV-1 VLP combined vaccine in BALB/c mice.

Human immunodeficiency virus (HIV) induced AIDS causes a large number of infections and deaths worldwide every year, still no vaccines are available to prevent infection. Recombinant herpes simplex virus type 1 (HSV-1) vector-based vaccines coding the target proteins of other pathogens have been widely used for disease control. Here, a recombinant virus with HIV-1 gp160 gene integration into the internal reverse (IR) region-deleted HSV-1 vector (HSV-BAC), was obtained by bacterial artificial chromosome (BAC) technology, and its immunogenicity investigated in BALB/c mice. The result showed similar replication ability of the HSV-BAC-based recombinant virus and wild type. Furthermore, humoral and cellular immune response showed superiority of intraperitoneal (IP) administration, compared to intranasally (IN), subcutaneous (SC) and intramuscularly (IM), that evidenced by production of significant antibody and T cell responses. More importantly, in a prime-boost combination study murine model, the recombinant viruses prime followed by HIV-1 VLP boost induced stronger and broader immune responses than single virus or protein vaccination in a similar vaccination regimen. Antibody production was sufficient with huge potential for viral clearance, along with efficient T-cell activation, which were evaluated by the enzyme-linked immunosorbent assay (ELISA) and flow cytometry (FC). Overall, these findings expose the value of combining different vaccine vectors and modalities to improve immunogenicity and breadth against different HIV-1 antigens.

An Overview of Current Accomplishments and Gaps of COVID-19 Vaccine Platforms and Considerations for Next Generation Vaccines

Vaccines against SARS-CoV-2 have transformed the course of the COVID-19 pandemic with more than 30 authorizations. More than 2 billion people have been vaccinated with these vaccines developed on very different manufacturing platforms. We have reviewed the unprecedented work done in various aspects of the authorized vaccines and listed three potential improvements: 1) long-term stability at room-temperature conditions; 2) suitability for diverse populations such as infants, elderly, immune-compromised, and those with pre-existing or ongoing diseases; and 3) ability to act against different strains. In this article, we have discussed the current status of COVID-19 vaccines with respect to 1) diversity (strength and breadth) of initial immune responses and long-term immune memory; 2) prime-boost combinations that induce protection against variants; and 3) breakthrough infections. Further, we have listed host, product (critical quality attributes), and viral pathogenic factors that contribute to safety, efficacy, and effectiveness of vaccines. In addition, we have elaborated on the potential to (develop models and) determine the immune correlates that can predict long-term immune memory. The graphical representation of the abstract is provided as Fig. 1.

A prime-boost combination of a three-protein cocktail and multiepitopic MVA as a vaccine against Babesia bigemina elicits neutralizing antibodies and a Th1 cellular immune response in mice

In the intraerythrocytic protozoan parasites of the genus Babesia both innate and adaptive immune responses are necessary to confer protection against clinical disease. In particular, the adaptive immune response involves the production of neutralizing antibodies as well as the presentation of parasite antigens to CD4+ T lymphocytes by professional antigen-presenting cells. Therefore, the development of alternative vaccines that replace the use of live attenuated strains should include relevant epitopes targeting both B and T cell responses. The aim of this study was to design new Babesia bigemina immunogens and evaluate the humoral and cellular responses in mice. To achieve this, three B. bigemina recombinant antigens called Apical Membrane Antigen 1 (AMA-1), Rhoptry Associated Protein 1 (RAP-1) and the Thrombospondin Related Anonymous Protein 1 (TRAP-1) were obtained. Besides, two recombinant modified vaccinia virus Ankara vectors coding for chimeric constructs containing bioinformatically predicted B and T cell epitopes from the same three antigens were generated. These immunogens were evaluated in prime-boost heterologous schemes. Among the combinations tested, priming with a cocktail of the three proteins followed by a booster immunization with a mix of both viruses induced the highest activation of IFN-γ+ CD4+ and CD8+ antigen-specific T cell responses. Remarkably, all vaccine schemes containing antigen cocktails also induced antibodies that were capable of neutralizing merozoite invasion of bovine erythrocytes in vitro at a level comparable to an anti B. bigemina hyperimmune bovine serum. Our results offer a new perspective for vaccines against B. bigemina combining bioinformatics predictions and prime-boost immunization regimes for future control measures against bovine babesiosis.

Rapid decline in vaccine-boosted neutralizing antibodies against SARS-CoV-2 Omicron variant

SummaryThe Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibits reduced susceptibility to vaccine-induced neutralizing antibodies, requiring a boost to generate protective immunity. We assess the magnitude and short-term durability of neutralizing antibodies after homologous and heterologous boosting with mRNA and Ad26.COV2.S vaccines. All prime-boost combinations substantially increase the neutralization titers to Omicron, although the boosted titers decline rapidly within 2 months from the peak response compared with boosted titers against the prototypic D614G variant. Boosted Omicron neutralization titers are substantially higher for homologous mRNA vaccine boosting, and for heterologous mRNA and Ad26.COV2.S vaccine boosting, compared with homologous Ad26.COV2.S boosting. Homologous mRNA vaccine boosting generates nearly equivalent neutralizing activity against Omicron sublineages BA.1, BA.2, and BA.3 but modestly reduced neutralizing activity against BA.2.12.1 and BA.4/BA.5 compared with BA.1. These results have implications for boosting requirements to protect against Omicron and future variants of SARS-CoV-2. This trial was conducted under ClincalTrials.gov: NCT04889209.

Immunogenicity and reactogenicity after heterologous prime-boost vaccination with CoronaVac and ChAdox1 nCov-19 (AZD1222) vaccines

ABSTRACT Mass vaccination with a safe and effective vaccine may be the best way to control the COVID-19 pandemic. Heterologous prime-boost vaccination with the CoronaVac and AZD1222 vaccines may increase the immunogenicity elicited by either vaccine alone. This study sought to compare the immunogenicity of a heterologous CoronaVac and AZD1222 prime-boost with a homologous CoronaVac prime-boost. From July 13 to September 2, 2021, 88 participants were enrolled in the study. Half (n = 44) of the participants were assigned to the AZD1222/CoronaVac cohort and half were assigned to the CoronaVac/AZD1222 cohort. Both cohorts had a prime-boost interval of 4 weeks. A control group of 136 health care personnel who received the homologous CoronaVac/CoronaVac prime-boost was matched by age and sex to the experimental cohorts. The primary endpoint was the geometric mean ratio (GMR) of the anti-receptor binding domain (RBD) antibody concentration 4 weeks after the booster dose was administered. The CoronaVac/CoronaVac cohort served as the reference group. Baseline age and sex were similar, and the median age was 42.5 years. The GMR was 2.58 (95% confidence interval [CI] 1.80–3.71) and 8.69 (95% CI 6.05–12.47) in the AZD1222/CoronaVac and CoronaVac/AZD1222 cohorts, respectively. Reactogenicity was similar following prime and booster doses with the same vaccine. Findings indicated that the heterologous CoronaVac and AZD1222 prime-boost combination elicited a more robust immune response than the homologous CoronaVac prime-boost. While both heterologous prime-boost combinations showed similar reactogenicity, the immunogenicity of the CoronaVac/AZD1222 cohort was higher, indicating that the order of prime-boost vaccine administration was important.

SARS-CoV-2 vaccine research and immunization strategies for improved control of the COVID-19 pandemic.

The record speed at which Chinese scientists identified severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2) and shared its genomic sequence with the world, has greatly facilitated the development of coronavirus disease (COVID-19) diagnostics, drugs, and vaccines. It is unprecedented in pandemic control history to develop a dozen successful vaccines in the first year and to immunize over half of the global population in the second year, due to the efforts of the scientific community, biopharmaceutical industry, and regulatory agencies worldwide. The challenges are both great and multidimensional due to the rapid emergence of virus variants and waning of vaccine immunity. Vaccination strategies need to adapt to these challenges to keep population immunity above the herd immunity threshold, by increasing vaccine coverage, especially for older adults and young people, and providing timely booster doses with homologous or heterologous vaccine boosts. Further research should be undertaken to develop more effective vaccines against SARS-CoV-2 variants and to understand the best prime-boost vaccine combinations and immunization strategies to provide sufficient and sustainable immune protection against COVID-19.

Heterologous Prime-Boost Vaccination with a Peptide-Based Vaccine and Viral Vector Reshapes Dendritic Cell, CD4+ and CD8+ T Cell Phenotypes to Improve the Antitumor Therapeutic Effect.

Simple SummaryDeveloping new therapeutic cancer vaccines is of paramount importance to counteract tumor escape observed after conventional therapies in certain types of cancer. We have previously shown that the combination of two different vaccine platforms, targeting tumor-specific antigens, resulted in potent immune responses in preclinical models. Here, we show that the heterologous prime-boost combination with a protein vaccine and a viral vector vesicular stomatitis virus immunologically reshapes the immune-excluded TC-1 tumor model as well as the inflamed MC-38 tumor model, leading to beneficial therapeutic efficacy. Furthermore, the treatment with a multi-epitope vaccine allowed us to appreciate the various repartition among three antigen-specific cytotoxic T-cell responses combined with the viral boost. The combination leads to improved efficacy in all animals and highlights the importance of combining tumor epitopes. Our vaccine strategy could be further extended to prophylactic cancer vaccines and beyond, for infectious diseases.Heterologous prime-boost settings with a protein vaccine and the viral vector vesicular stomatitis virus, both expressing tumor-associated antigens (KISIMA-TAA and VSV-GP-TAA), have been previously shown to generate potent antitumor immunity. In the cold TC-1 model (HPV antigen) and the immune-infiltrate MC-38 model (Adpgk, Reps1 and Rpl18 neo-antigens), we further investigated pivotal immune cells that educate CD8+ T cells. Heterologous prime-boost vaccination induced a superior antitumor response characterized by the increase in number and functionality of antigen-specific CD8+ T cells, recruitment of cross-presenting dendritic cells, and polarization of CD4+ T cells towards an antitumor Th1 phenotype within the tumor and tumor-draining lymph nodes, turning the cold TC-1 tumor into a hot, inflamed tumor. In the inflamed MC-38 tumor model, treatment combination markedly prolonged the overall survival of mice. Treatment with multi-epitope vaccines also induced high frequencies of multiple antigen specificities in the periphery and in the tumor. Prime-boost treatment reduced tumor-infiltrating regulatory CD4+ T cells whilst increasing cross-presenting dendritic cells in tumor-draining lymph nodes. In conclusion, heterologous prime-boost vaccination possesses the ability to induce a potent anti-tumor response in both immune-excluded and immune-infiltrated mouse tumor models. Additionally, this study highlights the design of a multi-epitope vaccine for cancer immunotherapy.

T cell and memory B cell responses in tetravalent DNA, tetravalent inactivated and tetravalent live-attenuated prime-boost dengue vaccines in rhesus macaques

We previously reported the efficacy of prime-boost vaccination using three tetravalent (T) dengue vaccines, DNA (TDNA), purified inactivated vaccine (TPIV), and live attenuated vaccine (TLAV). We demonstrated that the TPIV/TLAV prime-boost vaccination yielded the highest and most durable neutralizing antibodies and 100% protection to all 4 serotypes of dengue virus in rhesus macaques. This study compares gene transcription, T and B cell responses elicited by these prime-boost combinations in rhesus macaques.This study shows that the TLAV vaccine increased the expression of the innate immune genes, DDX58 and TLR7, IL1A, IL1B, TNF, CXCL8, CXCL10, IRF1, IRF7, and IFNB, more robustly as compared to TDNA and TPIV vaccines. Overall, two doses of TDNA and one dose of TLAV efficiently elicited a T cell IFNγ response to PrM/E with a comparable magnitude. Compared to TDNA vaccine, the TLAV vaccine elicited additional IFNγ response to C, NS1, NS3, and NS5. The TPIV vaccine alone produced poor IFNγ response; however, the TLAV significantly boosted its IFNγ response. The T cell response repertoire associated with TPIV/TLAV prime-boost was to both the structural C/PrM/E and NS proteins, and the T cells were multifunctional as the CD4+ T cells produced IFNγ, TNF α, and IL2 and the CD8+ cells produced TNF α and IFNγ. Opposite to the pattern of CMI, the TPIV vaccine alone elicited the highest BMem compared to the other two vaccines, which continuously remained as the highest after boosting.In summary, the TDNA and TLAV vaccines elicited a strong T cell response whereas the TPIV vaccine elicited a superior BMem. The T cell response of the TPIV vaccine was significantly boosted by the TLAV vaccine. The elevated T cell response may have provided T cell help for a sustained antibody response for TPIV/TLAV vaccines, which is required for a protective immunity against a live virus challenge.

Distinct patterns of whole blood transcriptional responses are induced in mice following immunisation with adenoviral and poxviral vector vaccines encoding the same antigen

BackgroundViral vectors, including adenovirus (Ad) and modified vaccinia Ankara (MVA), have gained increasing attention as vaccine platforms in recent years due to their capacity to express antigens from a wide array of pathogens, their rapid induction of humoral and cellular protective immune responses, and their relatively low production costs. In particular, the chimpanzee Ad vector, ChAdOx1, has taken centre stage as a leading COVID-19 vaccine candidate. However, despite mounting data, both clinical and pre-clinical, demonstrating effective induction of adaptive immune responses, the innate immune signals that precede the protective responses that make these vectors attractive vaccine platforms remain poorly understood.ResultsIn this study, a mouse immunisation model was used to evaluate whole blood gene expression changes 24 h after either a single dose or heterologous prime-boost regimen of an Ad and/or MVA vaccine. We demonstrate through comparative analysis of Ad vectors encoding different antigens that a transgene product-specific gene signature can be discerned from the vector-induced transcriptional response. Expression of genes involved in TLR2 stimulation and γδ T cell and natural killer cell activation were induced after a single dose of Ad, while MVA led to greater expression of type I interferon genes. The order of prime-boost combinations was found to influence the magnitude of the gene expression changes, with MVA/Ad eliciting greater transcriptional perturbation than Ad/MVA. Contrasting the two regimens revealed significant enrichment of epigenetic regulation pathways and augmented expression of MHC class I and II molecules associated with MVA/Ad.ConclusionThese data demonstrate that the order in which vaccines from heterologous prime-boost regimens are administered leads to distinct transcriptional responses and may shape the immune response induced by such combinations. The characterisation of early vaccine-induce responses strengthens our understanding of viral vector vaccine mechanisms of action ahead of their characterisation in human clinical trials and are a valuable resource to inform the pre-clinical design of appropriate vaccine constructs for emerging infectious diseases.

Surprisingly Effective Priming of CD8+ T Cells by Heat-Inactivated Vaccinia Virus Virions.

Robust priming of CD8+ T cells by viruses is considered to require infection and de novo expression of viral antigens. A corollary of this is that inactivated viruses are thought of as being inevitably poor vaccines for eliciting these responses. In contrast to this dogma, we found that some antigens present in vaccinia virus (VACV) virions prime strong CD8+ T cell responses when the virus was rendered noninfectious by heat. More surprisingly, in some cases these responses were similar in magnitude to those primed by infectious virus administered at an equivalent dose. Next, we tested whether this was a special property of particular antigens and their epitopes and found that foreign epitopes tagged onto three different VACV virion proteins were able to elicit CD8+ T cell responses irrespective of whether the virus was viable or heat killed. Further, the polyfunctionality and cytotoxic ability of the CD8+ T cells primed by these VACVs was equivalent irrespective of whether they were administered to mice as inactivated or live viruses. Finally, we used these VACVs in prime-boost combinations of inactivated and live virus and found that priming with dead virus before a live booster was the most immunogenic regime. We conclude that VACV virions can be efficient vectors for targeting antigens to dendritic cells for effective priming of CD8+ T cells, even when rendered noninfectious and speculate that this might also be the case for other viruses.IMPORTANCE The design of viral vectored vaccines is often considered to require a trade-off between efficacy and safety. This is especially the case for vaccines that aim to induce killer (CD8+) T cells, where there is a well-established dogma that links infection in vaccinated individuals with effective induction of immunity. However, we found that some proteins of vaccinia virus generate strong CD8+ T cell responses even when the virus preparation was inactivated by heat prior to administration as a vaccine. We took advantage of this finding by engineering a new vaccine vector virus that could be used as an inactivated vaccine. These results suggest that vaccinia virus may be a more versatile vaccine vector than previously appreciated and that in some instances safety can be prioritized by the complete elimination of viral replication without a proportional loss of immunogenicity.

Recombinant HIV-1 vaccine candidates based on replication-defective flavivirus vector

Multiple approaches utilizing viral and DNA vectors have shown promise in the development of an effective vaccine against HIV. In this study, an alternative replication-defective flavivirus vector, RepliVax (RV), was evaluated for the delivery of HIV-1 immunogens. Recombinant RV-HIV viruses were engineered to stably express clade C virus Gag and Env (gp120TM) proteins and propagated in Vero helper cells. RV-based vectors enabled efficient expression and correct maturation of Gag and gp120TM proteins, were apathogenic in a sensitive suckling mouse neurovirulence test, and were similar in immunogenicity to recombinant poxvirus NYVAC-HIV vectors in homologous or heterologous prime-boost combinations in mice. In a pilot NHP study, immunogenicity of RV-HIV viruses used as a prime or boost for DNA or NYVAC candidates was compared to a DNA prime/NYVAC boost benchmark scheme when administered together with adjuvanted gp120 protein. Similar neutralizing antibody titers, binding IgG titers measured against a broad panel of Env and Gag antigens, and ADCC responses were observed in the groups throughout the course of the study, and T cell responses were elicited. The entire data demonstrate that RV vectors have the potential as novel HIV-1 vaccine components for use in combination with other promising candidates to develop new effective vaccination strategies.

Arenavirus-based vector platform for massive tumor self-antigen-specific CD8 T cell immunity.

e14297 Background: The induction of powerful CD8+ T cell immunity to tumor associated self-antigens (TAAs) represents a critical yet challenging goal. Here we report on the development of an arenavirus-based delivery platform meeting this challenge. Previously we have shown that genetically engineered replication-attenuated lymphocytic choriomeningitis virus (LCMV) vectors, TheraT(LCMV), induce strong TAA-specific CD8 T cell immunity, but these responses can not be substantially augmented upon TheraT(LCMV) readministration. Counter to expectations, vector-neutralizing antibodies were not accountable for limited homologous prime-boosting capacity. Instead, dominant viral backbone-reactive CD8+ T cells competed against subdominant TAA-specific responses, limiting their magnitude. Methods: Herein we engineered and characterized delivery systems based on the arenaviruses Mopeia, Candid#1 and Pichinde (TheraT(MOP), TheraT(CAND), TheraT(PIC)). Results: We demonstrate that heterologous TheraT(CAND) – TheraT(LCMV) and TheraT(PIC)-TheraT(LCMV) prime-boost substantially augment TAA-specific CD8 T cell responses by rendering them immunodominant. Accordingly, intravenous administration of mice triggered up to 50% TAA epitope-specific CD8+ T cells and cured established tumors. Conversely, TheraT(MOP) – TheraT(LCMV) prime-boost was poorly immunogenic owing to cross-reactive T cell epitopes in the respective viral backbones. Conclusions: These findings establish heterologous arenavirus prime-boost combinations as a powerful new modality in tumor immunotherapy and highlight CD8 T cell epitope dominance as a significant hurdle to overcome in the vectored delivery of TAAs.

Nanoencapsulation of inactivated-viral vaccine using chitosan nanoparticles: Evaluation of its protective efficacy and immune modulatory effects in olive flounder (Paralichthys olivaceus) against viral haemorrhagic septicaemia virus (VHSV) infection

Viral haemorrhagic septicaemia virus (VHSV), a (−) ssRNA virus belonging to the genus Novirhabdovirus of rhabdoviridae family, is the aetiological agent of viral haemorrhagic septicaemia (VHS) disease which causes huge economic losses in farmed olive flounder (Paralichthys olivaceus) and significant mortalities among several other marine fish species in Korea, Japan, and China. Previously, we developed an inactivated vaccine viz., formalin-inactivated VHSV mixed with squalene as adjuvant which was effective in conferring protective immunity (58–76% relative percentage survival) against VHSV but the mode of administration was intraperitoneal injection which is not feasible for small sized fingerling fish. To overcome this limitation, we presently focused on replacing the injection route of vaccine delivery by oral and immersion routes. In this context, we encapsulated the inactivated VHSV vaccine with chitosan nanoparticles (CNPs-IV) by water-in-oil (W/O) emulsification method. After encapsulation, two sets of in vivo vaccination trials were conducted viz., preliminary trial-I and final trial-II. In preliminary trial-I, olive flounder fingerlings (10.5 ± 1.7 g) were vaccinated with CNPs-IV by different delivery strategies involving oral and immersion routes (single/booster dose) followed by challenge with VHSV (1 × 106 TCID50 virus/fish) to evaluate an effective method amongst different applied delivery strategies. Subsequently, a final trial-II was conducted to better understand the immune mechanism behind the efficacy of the employed delivery strategy and also to further improvise the delivery mechanism with prime-boost (primary immersion and oral boosting) combination in order to improve the transient anti-VHSV response in the host. Evaluation of RPS analysis in trial-I revealed higher RPS of 46.7% and 53.3% in the CNPs-IV (immersion) and CNPs-IV (immersion/immersion) groups, respectively compared to 0% RPS in the CNPs-IV (oral) group and 20% RPS in the CNPs-IV (oral/oral) group when calculated against 100% cumulative mortality percentage in the NVC (non-vaccinated challenged) control group, whereas, in the trial-II, RPS of 60% and 66.6% were obtained for CNPs-IV (immersion/immersion) and CNPs-IV (immersion/oral) groups, respectively. In addition, specific (anti-VHSV) antibody titre in the fish sera, skin mucus and intestinal mucus of the immunized groups were significantly (p < 0.05) enhanced following vaccination. Furthermore, CNPs-IV immunized fish showed significant (p < 0.05) upregulation of different immune gene transcripts (IgM, IgT, pIgR, MHC-I, MHC-II, IFN-γ, and Caspase3) compared to control, in both the systemic (kidney) and mucosal (skin and intestine) immune compartments of the host post immunization as well as post challenge. To conclude, mucosal immunization with CNPs-IV vaccine can orchestrate an effective immunization strategy in organizing a coordinative immune response against VHSV in olive flounder thereby exhibiting higher protective efficacy to the host with minimum stress.

Prime-boost vaccination strategy against avian influenza and Newcastle disease viruses reduces shedding of the challenge viruses.

In the present study, we carried-out assessment of efficacy of different immunization strategies using two bivalent vaccine formulations containing antigens of inactivated Newcastle disease virus (NDV-genotype VIId) and reassortant highly pathogenic avian influenza virus (H5N1-HPAIV) mixed with Montanide ISA71 and Montanide Gel02 as adjuvants. The efficacy of the prepared vaccines was evaluated by determining the cellular and humoral immune responses. In addition, protection against H5N1-AIV and NDV-genotype VIId challenge viruses post vaccination was assessed when Montanide-Gel02 based vaccine was inoculated in 10-days-old specific pathogen free chicks intraocularly once, twice or once followed by a boost with the Montanide ISA71 based vaccine. The cytokines profile analysis demonstrated that the prime-boost strategy induced the highest up-regulation in interferon-gamma (11.39-fold change) and interleukin-6 (14.12-fold change) genes expression. Also, enhanced lymphocytes proliferation was recorded beside increased antibody titers with protection levels reaching 50 and 60% against H5N1 and NDV challenge; respectively. Immunization with Montanide ISA71 inactivated vaccine induced 80% protection; however, the prime-boost combination afforded complete protection (100%) in the challenged chickens against mortality, clinical signs and virus shedding. Finally, these results highlight the significance of considering not only different vaccine platforms but also vaccination strategies to maximize protection against AIV and NDV with regards to the longevity of the vaccine-induced immune response.

MUC1- and Survivin-based DNA Vaccine Combining Immunoadjuvants CpG and interleukin-2 in a Bicistronic Expression Plasmid Generates Specific Immune Responses and Antitumour Effects in a Murine Colorectal Carcinoma Model.

DNA vaccination is a promising cancer treatment due to its safety, but poor immunogenicity limits its application. However, immunoadjuvants, heterogeneous prime-boost strategies and combination with conventional treatments can be used to improve the antitumour immune effects. A CpG motif and interleukin-2 (IL-2) cytokine are often used as adjuvants. In this study, a DNA vaccine containing a CpG motif was constructed to evaluate its adjuvant effect. The results show that the cytotoxicity of the DNA vaccine was increased fivefold, and survival lifetime was prolonged twofold by the CpG motif adjuvant. To simplify the industrial production process, a bicistronic plasmid was constructed to carry the fusion genes of survivin/MUC1 (MS) and IL-2 and with a CpG motif in its backbone. The results showed that the antitumour effect of the bicistronic vaccine was the same as that of the two vaccine co-injected regime. Furthermore, the vaccine could suppress metastatic tumour foci by 69.1% in colorectal carcinoma-bearing mice. Moreover, the vaccine induced survivin- and MUC1-specific immune responses in splenocytes and induced the immune promoting factor CCL-19 and GM-CSF upregulated, while metastatic-associated factor MMP-9 and immunosuppressing factor PD-L1 downregulated in tumour tissue. When combining the vaccine with the chemotherapy drug oxaliplatin, the survival was prolonged by about 2.5-fold. In conclusion, the DNA vaccine containing a CpG motif in bicistronic form showed good effects on colorectal cancer by inhibiting both tumour growth and metastasis, and combination with oxaliplatin could improve its antitumour effects.

Toxicity study in C57/BL6 mice after repeated intramuscular administration of the HIV-1 therapeutic prime-boost vaccine combination DNA.HTI and MVA.HTI

Toxicity study in C57/BL6 mice after repeated intramuscular administration of the HIV-1 therapeutic prime-boost vaccine combination DNA.HTI and MVA.HTI