Multigenic DNA vaccine induces protective cross-reactive T cell responses against heterologous influenza virus in nonhuman primates

Mosaic sarbecovirus nanoparticles elicit cross-reactive responses in pre-vaccinated animals

Immunization with mosaic-8b [60-mer nanoparticles presenting 8 SARS-like betacoronavirus (sarbecovirus) receptor-binding domains (RBDs)] elicits more broadly cross-reactive antibodies than homotypic SARS-CoV-2 RBD-only nanoparticles and protects against sarbecoviruses. To investigate original antigenic sin (OAS) effects on mosaic-8b efficacy, we evaluated effects of prior COVID-19 vaccinations in non-human primates and mice on anti-sarbecovirus responses elicited by mosaic-8b, admix-8b (8 homotypics), or homotypic SARS-CoV-2 immunizations, finding greatest cross-reactivity for mosaic-8b. As demonstrated by molecular fate-mapping in which antibodies from specific cohorts of B cells are differentially detected, B cells primed by WA1 spike mRNA-LNP dominated antibody responses after RBD-nanoparticle boosting. While mosaic-8b- and homotypic-nanoparticles boosted cross-reactive antibodies, de novo antibodies were predominantly induced by mosaic-8b, and these were specific for variant RBDs with increased identity to RBDs on mosaic-8b. These results inform OAS mechanisms and support using mosaic-8b to protect COVID-19 vaccinated/infected humans against as-yet-unknown SARS-CoV-2 variants and animal sarbecoviruses with human spillover potential.

Impact of progesterone on innate immunity and cell death after influenza A virus H1N1 2009 infection of lung and placental cells in vitro

The influenza A virus (IAV) 2009 H1N1 pandemic was associated with an increased risk of maternal mortality, preterm birth, and stillbirth. The underlying mechanism for severe maternal lung disease and stillbirth is incompletely understood, but IAV infection is known to activate innate immunity triggering the release of cytokines. Elucidating the impact of progesterone (P4), a key hormone elevated in pregnancy, on the innate immune and inflammatory response to IAV infection is a critical step in understanding the pathogenesis of adverse maternal-fetal outcomes. IAV H1N1 pdm/09 was used to infect cell lines Calu-3 (lung adenoma) and ACH-3P (extravillous trophoblast) with or without P4 (100 nM) at multiplicity of infections (MOI) 0, 0.5, and 3. Cells were harvested at 24 and 48 hours post infection (hpi) and analyzed for cytopathic effects (CPE), replicating virus (TCID50), cytotoxicity (Lactate Dehydrogenase (LDH) assay), and NLRP3 inflammasome activation (caspase-1 activity, fluorometric assay). Activation of antiviral innate immunity was quantified (RT-qPCR, Luminex) by measuring biomarker gene and protein expression of innate immune activation (IFIT1, IFNB), inflammation (IL6), interferon signaling (MXA), chemokines (IL-8, IL-10). Both Calu-3 and ACH-3P were highly permissible to IAV infection at each timepoint as demonstrated by CPE and recovery of replicating virus. In Calu-3, progesterone treatment was associated with a significant increase in cytotoxicity, increased gene expression of IL6, and increased protein expression of IFN-β, IL-6, and IL-18. Conversely, in ACH-3P, progesterone treatment was associated with significantly suppressed cytotoxicity, decreased gene expression of IFNB, IL6 and IL1B, and increased protein expression of IFN-β and IL-6. In both cell lines, caspase-1 activity was significantly decreased after progesterone treatment, indicating NLRP3 inflammasome activation was not underlying the higher cell death in Calu-3. In summary, these data provide evidence that progesterone plays a dual role by ameliorating viral infection in the placenta but exacerbating influenza A virus-associated injury in the lung through nongenomic modulation of the innate immune response.

Induction of food-specific IgG by Gene Gun-delivered DNA vaccines

Background

Shellfish and tree nut allergies are among the most prevalent food allergies, now affecting 2%–3% and 1% of the US population, respectively. Currently, there are no approved therapies for shellfish or tree nut allergies, with strict avoidance being the standard of care. However, oral immunotherapy for peanut allergy and subcutaneous immunotherapy for environmental allergens are efficacious and lead to the production of allergen-specific IgG, which causes suppression of allergen effector cell degranulation. Since allergen-specific IgG is a desired response to alleviate IgE-mediated allergies, we tested transcutaneously-delivered DNA vaccines targeting shellfish and tree nut allergens for their ability to induce antigen-specific IgG, which would have therapeutic potential for food allergies.

Methods

We assessed Gene Gun-delivered DNA vaccines targeting either crustacean shellfish or walnut/pecan allergens, with or without IL-12, in naïve mice. Three strains of mice, BALB/cJ, C3H/HeJ and CC027/GeniUnc, were evaluated for IgG production following vaccination. Vaccines were administered twice via Gene Gun, three weeks apart and then blood was collected three weeks following the final vaccination.

Results

Vaccination with shellfish allergen DNA led to increased shrimp-specific IgG in all three strains, with the highest production in C3H/HeJ from the vaccine alone, whereas the vaccine with IL-12 led to the highest IgG production in BALB/cJ and CC027/GeniUnc mice. Similar IgG production was also induced against lobster and crab allergens. For walnut/pecan vaccines, BALB/cJ and C3H/HeJ mice produced significantly higher walnut- and pecan-specific IgG with the vaccine alone compared to the vaccine with IL-12, while the CC027 mice made significantly higher IgG with the addition of IL-12. Notably, intramuscular administration of the vaccines did not lead to increased antigen-specific IgG production, indicating that Gene Gun administration is a superior delivery modality.

Conclusions

Overall, these data demonstrate the utility of DNA vaccines against two lifelong food allergies, shellfish and tree nuts, suggesting their potential as a food allergy therapy in the future.

STING Is Required in Conventional Dendritic Cells for DNA Vaccine Induction of Type I T Helper Cell- Dependent Antibody Responses

DNA vaccines elicit antibody, T helper cell responses and CD8⁺ T cell responses. Currently, little is known about the mechanism that DNA vaccines employ to induce adaptive immune responses. Prior studies have demonstrated that stimulator of interferon genes (STING) and conventional dendritic cells (cDCs) play critical roles in DNA vaccine induced antibody and T cell responses. STING activation by double stranded (dsDNA) sensing proteins initiate the production of type I interferon (IFN),but the DC-intrinsic effect of STING signaling is still unclear. Here, we investigated the role of STING within cDCs on DNA vaccine induction of antibody and T cell responses. STING knockout (STING^-/- ) and conditional knockout mice that lack STING in cDCs (cDC STING cKO), were immunized intramuscularly with a DNA vaccine that expressed influenza A nucleoprotein (pNP). Both STING^-/- and cDC STING cKO mice had significantly lower type I T helper (Th1) type antibody (anti-NP IgG_2C) responses and lower frequencies of Th1 associated T cells (NP-specific IFN-γ⁺CD4⁺ T cells) post-immunization than wild type (WT) and cDC STING littermate control mice. In contrast, all mice had similar Th2-type NP-specific (IgG₁) antibody titers. STING^-/- mice developed significantly lower polyfunctional CD8⁺ T cells than WT, cDC STING cKO and cDC STING littermate control mice. These findings suggest that STING within cDCs mediates DNA vaccine induction of type I T helper responses including IFN-γ⁺CD4⁺ T cells, and Th1-type IgG_2C antibody responses. The induction of CD8⁺ effector cell responses also require STING, but not within cDCs. These findings are the first to show that STING is required within cDCs to mediate DNA vaccine induced Th1 immune responses and provide new insight into the mechanism whereby DNA vaccines induce Th1 responses.

Animal Models Utilized for the Development of Influenza Virus Vaccines

Animal models have been an important tool for the development of influenza virus vaccines since the 1940s. Over the past 80 years, influenza virus vaccines have evolved into more complex formulations, including trivalent and quadrivalent inactivated vaccines, live-attenuated vaccines, and subunit vaccines. However, annual effectiveness data shows that current vaccines have varying levels of protection that range between 40–60% and must be reformulated every few years to combat antigenic drift. To address these issues, novel influenza virus vaccines are currently in development. These vaccines rely heavily on animal models to determine efficacy and immunogenicity. In this review, we describe seasonal and novel influenza virus vaccines and highlight important animal models used to develop them.

Effective inactivated influenza vaccine for the elderly using a single-stranded RNA-based adjuvant

There is an unmet need for new influenza vaccine strategies that compensate for impaired vaccine responses in elderly individuals. Here, we evaluated the effectiveness of a single-stranded RNA (ssRNA) as an adjuvant to enhance the efficacy of inactivated influenza vaccine (IIV) in mouse models. Immunization with the ssRNA along with IIV reduced viral titers as well as pathological and inflammatory scores in the lungs after influenza challenge in aged mice. ssRNA induced balanced Th1/Th2 responses with an increase in IgA titers. Moreover, the ssRNA adjuvant markedly increased the frequency of influenza HA-specific T cells and IFN-γ production along with the expression of genes related to innate and adaptive immune systems that could overcome immunosenescence in aged mice. Our findings indicate that ssRNA is an efficient vaccine adjuvant that boosts cellular and humoral immunity in aged mice, demonstrating its potential as a novel adjuvant for currently available influenza virus vaccines for elderly individuals.

Animal Models for Influenza Research: Strengths and Weaknesses

Influenza remains one of the most significant public health threats due to its ability to cause high morbidity and mortality worldwide. Although understanding of influenza viruses has greatly increased in recent years, shortcomings remain. Additionally, the continuous mutation of influenza viruses through genetic reassortment and selection of variants that escape host immune responses can render current influenza vaccines ineffective at controlling seasonal epidemics and potential pandemics. Thus, there is a knowledge gap in the understanding of influenza viruses and a corresponding need to develop novel universal vaccines and therapeutic treatments. Investigation of viral pathogenesis, transmission mechanisms, and efficacy of influenza vaccine candidates requires animal models that can recapitulate the disease. Furthermore, the choice of animal model for each research question is crucial in order for researchers to acquire a better knowledge of influenza viruses. Herein, we reviewed the advantages and limitations of each animal model-including mice, ferrets, guinea pigs, swine, felines, canines, and non-human primates-for elucidating influenza viral pathogenesis and transmission and for evaluating therapeutic agents and vaccine efficacy.

Advances in gene-based vaccine platforms to address the COVID-19 pandemic

The novel betacoronavirus, SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), has spread across the globe at an unprecedented rate since its first emergence in Wuhan City, China in December 2019. Scientific communities around the world have been rigorously working to develop a potent vaccine to combat COVID-19 (coronavirus disease 2019), employing conventional and novel vaccine strategies. Gene-based vaccine platforms based on viral vectors, DNA, and RNA, have shown promising results encompassing both humoral and cell-mediated immune responses in previous studies, supporting their implementation for COVID-19 vaccine development. In fact, the U.S. Food and Drug Administration (FDA) recently authorized the emergency use of two RNA-based COVID-19 vaccines. We review current gene-based vaccine candidates proceeding through clinical trials, including their antigenic targets, delivery vehicles, and route of administration. Important features of previous gene-based vaccine developments against other infectious diseases are discussed in guiding the design and development of effective vaccines against COVID-19 and future derivatives.

T Cell Immunity against Influenza: The Long Way from Animal Models Towards a Real-Life Universal Flu Vaccine

Current flu vaccines rely on the induction of strain-specific neutralizing antibodies, which leaves the population vulnerable to drifted seasonal or newly emerged pandemic strains. Therefore, universal flu vaccine approaches that induce broad immunity against conserved parts of influenza have top priority in research. Cross-reactive T cell responses, especially tissue-resident memory T cells in the respiratory tract, provide efficient heterologous immunity, and must therefore be a key component of universal flu vaccines. Here, we review recent findings about T cell-based flu immunity, with an emphasis on tissue-resident memory T cells in the respiratory tract of humans and different animal models. Furthermore, we provide an update on preclinical and clinical studies evaluating T cell-evoking flu vaccines, and discuss the implementation of T cell immunity in real-life vaccine policies.

The Next Generation of Influenza Vaccines: Towards a Universal Solution

Influenza viruses remain a constant burden in humans, causing millions of infections and hundreds of thousands of deaths each year. Current influenza virus vaccine modalities primarily induce antibodies directed towards the highly variable head domain of the hemagglutinin protein on the virus surface. Such antibodies are often strain-specific, meaning limited cross-protection against divergent influenza viruses is induced, resulting in poor vaccine efficacy. To attempt to counteract this, yearly influenza vaccination with updated formulations containing antigens from more recently circulating viruses is required. This is an expensive and time-consuming exercise, and the constant arms race between host immunity and virus evolution presents an ongoing challenge for effective vaccine development. Furthermore, there exists the constant pandemic threat of highly pathogenic avian influenza viruses with high fatality rates (~30–50%) or the emergence of new, pathogenic reassortants. Current vaccines would likely offer little to no protection from such viruses in the event of an epidemic or pandemic. This highlights the urgent need for improved influenza virus vaccines capable of providing long-lasting, robust protection from both seasonal influenza virus infections as well as potential pandemic threats. In this narrative review, we examine the next generation of influenza virus vaccines for human use and the steps being taken to achieve universal protection.

Protective efficacy of a polyvalent influenza A DNA vaccine against both homologous (H1N1pdm09) and heterologous (H5N1) challenge in the ferret model

This study describes the protective efficacy of a novel influenza plasmid DNA vaccine in the ferret challenge model. The rationally designed polyvalent influenza DNA vaccine encodes haemagglutinin and neuraminidase proteins derived from less glycosylated pandemic H1N1 (2009) and H3N2 (1968) virus strains as well as the nucleoprotein (NP) and matrix proteins (M1 and M2) from a different pandemic H1N1 (1918) strain. Needle-free intradermal immunisation with the influenza DNA vaccine protected ferrets against homologous challenge with an H1N1pdm09 virus strain, demonstrated by restriction of viral replication to the upper respiratory tract and reduced duration of viral shedding post-challenge. Breadth of protection was demonstrated in two heterologous efficacy experiments in which animals immunised with the influenza DNA vaccine were protected against challenge with a highly pathogenic avian influenza H5N1 virus strain with reproducible survival and clinical outcomes.

Vaccination into the Dermal Compartment: Techniques, Challenges, and Prospects

In 2019, an 'influenza pandemic' and 'vaccine hesitancy' were listed as two of the top 10 challenges to global health by the WHO. The skin is a unique vaccination site, due to its immune-rich milieu, which is evolutionarily primed to respond to challenge, and its ability to induce both humoral and cellular immunity. Vaccination into this dermal compartment offers a way of addressing both of the challenges presented by the WHO, as well as opening up avenues for novel vaccine formulation and dose-sparing strategies to enter the clinic. This review will provide an overview of the diverse range of vaccination techniques available to target the dermal compartment, as well as their current state, challenges, and prospects, and touch upon the formulations that have been developed to maximally benefit from these new techniques. These include needle and syringe techniques, microneedles, DNA tattooing, jet and ballistic delivery, and skin permeabilization techniques, including thermal ablation, chemical enhancers, ablation, electroporation, iontophoresis, and sonophoresis.

Immunogenicity and Protective Efficacy of Influenza A DNA Vaccines Encoding Artificial Antigens Based on Conservative Hemagglutinin Stem Region and M2 Protein in Mice

Background: Development of a universal vaccine capable to induce antibody responses against a broad range of influenza virus strains attracts growing attention. Hemagglutinin stem and the exposed fragment of influenza virus M2 protein are promising targets for induction of cross-protective humoral and cell-mediated response, since they contain conservative epitopes capable to induce antibodies and cytotoxic T lymphocytes (CTLs) to a wide range of influenza virus subtypes. Methods: In this study, we generated DNA vaccine constructs encoding artificial antigens AgH1, AgH3, and AgM2 designed on the basis of conservative hemagglutinin stem fragments of two influenza A virus subtypes, H1N1 and H3N2, and conservative M2 protein, and evaluate their immunogenicity and protective efficacy. To obtain DNA vaccine constructs, genes encoding the designed antigens were cloned into a pcDNA3.1 vector. Expression of the target genes in 293T cells transfected with DNA vaccine constructs has been confirmed by synthesis of specific mRNA. Results: Immunization of BALB/c mice with DNA vaccines encoding these antigens was shown to evoke humoral and T-cell immune responses as well as a moderated statistically significant cross-protective effect against two heterologous viruses A/California/4/2009 (H1N1pdm09) and A/Aichi/2/68 (H3N2). Conclusions: The results demonstrate a potential approach to creating a universal influenza vaccine based on artificial antigens.

Development of Universal Influenza Vaccines Targeting Conserved Viral Proteins

Vaccination is still the most efficient way to prevent an infection with influenza viruses. Nevertheless, existing commercial vaccines face serious limitations such as availability during epidemic outbreaks and their efficacy. Existing seasonal influenza vaccines mostly induce antibody responses to the surface proteins of influenza viruses, which frequently change due to antigenic shift and or drift, thus allowing influenza viruses to avoid neutralizing antibodies. Hence, influenza vaccines need a yearly formulation to protect against new seasonal viruses. A broadly protective or universal influenza vaccine must induce effective humoral as well as cellular immunity against conserved influenza antigens, offer good protection against influenza pandemics, be safe, and have a fast production platform. Nanotechnology has great potential to improve vaccine delivery, immunogenicity, and host immune responses. As new strains of human epidemic influenza virus strains could originate from poultry and swine viruses, development of a new universal influenza vaccine will require the immune responses to be directed against viruses from different hosts. This review discusses how the new vaccine platforms and nanoparticles can be beneficial in the development of a broadly protective, universal influenza vaccine.

The Quest for a Truly Universal Influenza Vaccine

There is an unmet public health need for a universal influenza vaccine (UIV) to provide broad and durable protection from influenza virus infections. The identification of broadly protective antibodies and cross-reactive T cells directed to influenza viral targets present a promising prospect for the development of a UIV. Multiple targets for cross-protection have been identified in the stalk and head of hemagglutinin (HA) to develop a UIV. Recently, neuraminidase (NA) has received significant attention as a critical component for increasing the breadth of protection. The HA stalk-based approaches have shown promising results of broader protection in animal studies, and their feasibility in humans are being evaluated in clinical trials. Mucosal immune responses and cross-reactive T cell immunity across influenza A and B viruses intrinsic to live attenuated influenza vaccine (LAIV) have emerged as essential features to be incorporated into a UIV. Complementing the weakness of the stand-alone approaches, prime-boost vaccination combining HA stalk, and LAIV is under clinical evaluation, with the aim to increase the efficacy and broaden the spectrum of protection. Preexisting immunity in humans established by prior exposure to influenza viruses may affect the hierarchy and magnitude of immune responses elicited by an influenza vaccine, limiting the interpretation of preclinical data based on naive animals, necessitating human challenge studies. A consensus is yet to be achieved on the spectrum of protection, efficacy, target population, and duration of protection to define a “universal” vaccine. This review discusses the recent advancements in the development of UIVs, rationales behind cross-protection and vaccine designs, and challenges faced in obtaining balanced protection potency, a wide spectrum of protection, and safety relevant to UIVs.

Improving Cross-Protection against Influenza Virus Using Recombinant Vaccinia Vaccine Expressing NP and M2 Ectodomain Tandem Repeats

Conventional influenza vaccines need to be designed and manufactured yearly. However, they occasionally provide poor protection owing to antigenic mismatch. Hence, there is an urgent need to develop universal vaccines against influenza virus. Using nucleoprotein (NP) and extracellular domain of matrix protein 2 (M2e) genes from the influenza A virus A/Beijing/30/95 (H3N2), we constructed four recombinant vaccinia virus-based influenza vaccines carrying NP fused with one or four copies of M2e genes in different orders. The recombinant vaccinia viruses were used to immunize BALB/C mice. Humoral and cellular responses were measured, and then the immunized mice were challenged with the influenza A virus A/Puerto Rico/8/34 (PR8). NP-specific humoral response was elicited in mice immunized with recombinant vaccinia viruses carrying full-length NP, while robust M2e-specific humoral response was elicited only in the mice immunized with recombinant vaccinia viruses carrying multiple copies of M2e. All recombinant viruses elicited NP- and M2e-specific cellular immune responses in mice. Only immunization with RVJ-4M2eNP induced remarkably higher levels of IL-2 and IL-10 cytokines specific to M2e. Furthermore, RVJ-4M2eNP immunization provided the highest cross-protection in mice challenged with 20 MLD₅₀ of PR8. Therefore, the cross-protection potentially correlates with both NP and M2e-specific humoral and cellular immune responses induced by RVJ-4M2eNP, which expresses a fusion antigen of full-length NP preceded by four M2e repeats. These results suggest that the rational fusion of NP and multiple M2e antigens is critical toward inducing protective immune responses, and the 4M2eNP fusion antigen may be employed to develop a universal influenza vaccine.

A prime-boost concept using a T-cell epitope-driven DNA vaccine followed by a whole virus vaccine effectively protected pigs in the pandemic H1N1 pig challenge model

Influenza A virus (IAV) vaccines in pigs generally provide homosubtypic protection but fail to prevent heterologous infections. In this pilot study, the efficacy of an intradermal pDNA vaccine composed of conserved SLA class I and class II T cell epitopes (EPITOPE) against a homosubtypic challenge was compared to an intramuscular commercial inactivated whole virus vaccine (INACT) and a heterologous prime boost approach using both vaccines. Thirty-nine IAV-free, 3-week-old pigs were randomly assigned to one of five groups including NEG-CONTROL (unvaccinated, sham-challenged), INACT-INACT-IAV (vaccinated with FluSure XP® at 4 and 7 weeks, pH1N1 challenged), EPITOPE-INACT-IAV (vaccinated with PigMatrix EDV at 4 and FluSure XP® at 7 weeks, pH1N1 challenged), EPITOPE-EPITOPE-IAV (vaccinated with PigMatrix EDV at 4 and 7 weeks, pH1N1 challenged), and a POS-CONTROL group (unvaccinated, pH1N1 challenged). The challenge was done at 9 weeks of age and pigs were necropsied at day post challenge (dpc) 5. At the time of challenge, all INACT-INACT-IAV pigs, and by dpc 5 all EPITOPE-INACT-IAV pigs were IAV seropositive. IFNγ secreting cells, recognizing vaccine epitope-specific peptides and pH1N1 challenge virus were highest in the EPITOPE-INACT-IAV pigs at challenge. Macroscopic lung lesion scores were reduced in all EPITOPE-INACT-IAV pigs while INACT-INACT-IAV pigs exhibited a bimodal distribution of low and high scores akin to naïve challenged animals. No IAV antigen in lung tissues was detected at necropsy in the EPITOPE-INACT-IAV group, which was similar to naïve unchallenged pigs and different from all other challenged groups. Results suggest that the heterologous prime boost approach using an epitope-driven DNA vaccine followed by an inactivated vaccine was effective against a homosubtypic challenge, and further exploration of this vaccine approach as a practical control measure against heterosubtypic IAV infections is warranted.

Self-destructing Salmonella via temperature induced gene E of phage PhiX174 improves influenza HA DNA vaccine immune protection against H1N1 infection in mice model

The delivery of DNA vaccines is the principle impediment for implementation of DNA vaccination on a mass scale. In this study, we report a temperature induced conditionally expressed phage PhiX174 gene E mediated lysis of Salmonella under in vivo conditions that can increase the immunogenicity of a DNA vaccine delivered via Salmonella carrier system. We electroporated gene E encoding lysis plasmid pJHL187 along with the pcDNA-HA plasmid encoding H1N1 HA into attenuated Salmonella Typhimurium, strain JOL1893. Using C57BL/6 mice as the model, we showed that the mice intragastrically vaccinated with JOL1893 induced significant production of HA-specific humoral and cell mediated immune responses compared to the JOL1837, which carry pcDNA-HA plasmid alone. Furthermore, mice vaccinated with JOL1893 vaccine were fully protected against the lethal H1N1 challenge compared to the JOL1837 strain, which showed 90% protection only. However, none of the animals survived treated with either the PBS or the Salmonella carrying empty vector. Taken together, our results indicate that mucosal immunization with conditional lysis enabled live attenuated S. Typhimurium as a DNA vaccine carrier can induce efficient systemic and mucosal immune responses, and improves immune protection against a highly pathogenic H1N1 infection in mice model.

Needle-free delivery of DNA: Targeting of hemagglutinin to MHC class II molecules protects rhesus macaques against H1N1 influenza

Conventional influenza vaccines are hampered by slow and limited production capabilities, whereas DNA vaccines can be rapidly produced for global coverage in the event of an emerging pandemic. However, a drawback of DNA vaccines is their generally low immunogenicity in non-human primates and humans. We have previously demonstrated that targeting of influenza hemagglutinin to human HLA class II molecules can increase antibody responses in larger animals such as ferrets and pigs. Here, we extend these observations by immunizing non-human primates (rhesus macaques) with a DNA vaccine encoding a bivalent fusion protein that targets influenza virus hemagglutinin (HA) to Mamu class II molecules. Such immunization induced neutralizing antibodies and antigen-specific T cells. The DNA was delivered by pain- and needle-free jet injections intradermally. No adverse effects were observed. Most importantly, the immunized rhesus macaques were protected against a challenge with influenza virus.

Universal Influenza Vaccines: Progress in Achieving Broad Cross-Protection In Vivo

Despite all we have learned since 1918 about influenza virus and immunity, available influenza vaccines remain inadequate to control outbreaks of unexpected strains. Universal vaccines not requiring strain matching would be a major improvement. Their composition would be independent of predicting circulating viruses and thus potentially effective against unexpected drift or pandemic strains. This commentary explores progress with candidate universal vaccines based on various target antigens. Candidates include vaccines based on conserved viral proteins such as nucleoprotein and matrix, on the conserved hemagglutinin (HA) stem, and various combinations. Discussion covers the differing evidence for each candidate vaccine demonstrating protection in animals against influenza viruses of widely divergent HA subtypes and groups; durability of protection; routes of administration, including mucosal, providing local immunity; and reduction of transmission. Human trials of some candidate universal vaccines have been completed or are underway. Interestingly, the HA stem, like nucleoprotein and matrix, induces immunity that permits some virus replication and emergence of escape mutants fit enough to cause disease. Vaccination with multiple target antigens will thus have advantages over use of single antigens. Ultimately, a universal vaccine providing long-term protection against all influenza virus strains might contribute to pandemic control and routine vaccination.

Early cellular innate immune responses drive Zika viral persistence and tissue tropism in pigtail macaques

The immunological and virological events that contribute to the establishment of Zika virus (ZIKV) infection in humans are unclear. Here, we show that robust cellular innate immune responses arising early in the blood and tissues in response to ZIKV infection are significantly stronger in males and correlate with increased viral persistence. In particular, early peripheral blood recruitment of plasmacytoid dendritic cells and higher production of monocyte chemoattractant protein (MCP-1) correspond with greater viral persistence and tissue dissemination. We also identify non-classical monocytes as primary in vivo targets of ZIKV infection in the blood and peripheral lymph node. These results demonstrate the potential differences in ZIKV pathogenesis between males and females and a key role for early cellular innate immune responses in the blood in viral dissemination and ZIKV pathogenesis.

A Review of DNA Vaccines Against Influenza

The challenges of effective vaccination against influenza are gaining more mainstream attention, as recent influenza seasons have reported low efficacy in annual vaccination programs worldwide. Combined with the potential emergence of novel influenza viruses resulting in a pandemic, the need for effective alternatives to egg-produced conventional vaccines has been made increasingly clear. DNA vaccines against influenza have been in development since the 1990s, but the initial excitement over success in murine model trials has been tempered by comparatively poor performance in larger animal models. In the intervening years, much progress has been made to refine the DNA vaccine platform-the rational design of antigens and expression vectors, the development of novel vaccine adjuvants, and the employment of innovative gene delivery methods. This review discusses how these advances have been applied in recent efforts to develop an effective influenza DNA vaccine.