The Protective Role of TLR3 and TLR9 Ligands in Human Pharyngeal Epithelial Cells Infected with Influenza A Virus

CD209d/e promotes inflammation and lung injury during influenza virus infection

Influenza virus infects millions each year, contributing greatly to human morbidity and mortality. Upon viral infection, pathogen-associated molecular patterns activate pattern recognition receptors on host cells, triggering an immune response. The CD209 protein family, homologs of DC-SIGN (dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin), is thought to modulate immune responses to viruses. The effects of the mouse functional DC-SIGN homolog CD209d/e on the lung immune responses during influenza viral infection are not known. Therefore, we generated mice that lack both CD209d and e isoforms to determine the role in influenza viral infection. We infected wild-type and CD209d/e gene-deficient (CD209d/e-/-) mice with influenza virus and measured the cellular response in bronchoalveolar lavage, the expression of proinflammatory cytokines, antiviral genes, toll-like receptors (TLRs) in the lung, and lung pathology. We found CD209d/e-/- mice had decreased viral burden, TLR3 and TLR9 expression, interferon response, macrophages in bronchoalveolar lavage, and parenchymal lung inflammation compared with control mice. We also found less influenza viral uptake in alveolar macrophages and bone marrow-derived macrophages isolated from CD209d/e-/- mice when compared with control mice. We further investigated the role CD209d/e by treating bone marrow-derived macrophages from control and CD209d/e-/- mice with TLR agonists. We found that lacking CD209d/e decreased the expression of TLR3, TLR9, RIG1, STAT1, and STAT2 compared with controls. Collectively these results show that CD209d/e plays an important role in viral sensing/uptake and inflammatory immune responses during influenza viral infection.

Recent Advances in Multifaceted Drug Delivery Using Natural Polysaccharides and Polyacrylamide-based Nanomaterials in Nanoformulation

Rapid growth in nanotechnology, also known as 21st-century technology, is occurring in response to the increasing diversity of diseases. The development of safe and effective drug delivery methods to enhance bioavailability is of paramount importance. Researchers have focused on creating safe, cost-effective, and environmentally friendly nanoparticle construction processes. Natural polysaccharides, a type of multifaceted polymer with a wide range of applications and advantages, are particularly well suited for nanoparticle formulations, as they can mitigate the adverse consequences of synthetic nanoparticle formulations and promote sustainability. This review summarizes various sources of natural-based polysaccharides and polyacrylamide-based nanomaterials in nanoparticle preparation. Additionally, it discusses the use of natural polysaccharides in formulations beyond nanotechnology, highlighting their importance in green synthesis and different preparation methods.

Imiquimod suppresses respiratory syncytial virus (RSV) replication via PKA pathway and reduces RSV induced-inflammation and viral load in mice lungs

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract disease and bronchiolitis in children, as well as an important cause of morbidity and mortality in elderly and immunocompromised individuals. However, there is no safe and efficacious RSV vaccine or antiviral treatment. Toll Like Receptors (TLR) are important molecular mediators linking innate and adaptive immunity, and their stimulation by cognate agonists has been explored as antiviral agents. Imiquimod is known as a TLR7 agonist, but additionally acts as an antagonist for adenosine receptors. In this study, we demonstrate that imiquimod, but not resiquimod, has direct anti-RSV activity via PKA pathway in HEp-2 and A549 cells, independently of an innate response. Imiquimod restricts RSV infection after viral entry into the host cell, interfering with viral RNA and protein synthesis. Probably as a consequence of these anti-RSV properties, imiquimod displays cytokine modulating activity in RSV infected epithelial cells. Moreover, in a murine model of RSV infection, imiquimod treatment improves the course of acute disease, evidenced by decreased weight loss, reduced RSV lung titers, and attenuated airway inflammation. Consequently, imiquimod represents a promising therapeutic alternative against RSV infection and may inform the development of novel therapeutic targets to control RSV pathogenesis.

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Imiquimod has direct anti-RSV activity via PKA pathway, independently of an innate response.

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Imiquimod restricts RSV infection after viral entry into the host cell, interfering with viral RNA and protein synthesis.

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Imiquimod reduces cytokine production in RSV infected epithelial cells, probably as a result of its anti-RSV properties.

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Imiquimod reduces RSV lung titers and decreases weight loss and airway inflammation in a murine model of RSV infection.

Pharyngeal Immunity in Early Vertebrates Provides Functional and Evolutionary Insight into Mucosal Homeostasis

The pharyngeal organ is located at the crossroad of the respiratory and digestive tracts in vertebrate, and it is continuously challenged by varying Ags during breathing and feeding. In mammals, the pharyngeal mucosa (PM) is a critical first line of defense. However, the evolutionary origins and ancient roles of immune defense and microbiota homeostasis of PM are still unknown. In this study, to our knowledge, we are the first to find that diffuse MALT is present in PM of rainbow trout, an early vertebrate. Importantly, following parasitic infection, we detect that strong parasite-specific mucosal IgT and dominant proliferation of IgT⁺ B cell immune responses occurs in trout PM, providing, to our knowledge, the first demonstration of local mucosal Ig responses against pathogens in pharyngeal organ of a nonmammal species. Moreover, we show that the trout PM microbiota is prevalently coated with secretory IgT and, to a much lesser degree, by IgM and IgD, suggesting the key role of mucosal Igs in the immune exclusion of teleost pharyngeal bacteria. Overall, to our knowledge, our findings provide the first evidence that pharyngeal mucosal immunity appear earlier than tetrapods.

Animal Models for Influenza A Virus Infection Incorporating the Involvement of Innate Host Defenses: Enhanced Translational Value of the Porcine Model

Influenza is a viral respiratory disease having a major impact on public health. Influenza A virus (IAV) usually causes mild transitory disease in humans. However, in specific groups of individuals such as severely obese, the elderly, and individuals with underlying inflammatory conditions, IAV can cause severe illness or death. In this review, relevant small and large animal models for human IAV infection, including the pig, ferret, and mouse, are discussed. The focus is on the pig as a large animal model for human IAV infection as well as on the associated innate immune response. Pigs are natural hosts for the same IAV subtypes as humans, they develop clinical disease mirroring human symptoms, they have similar lung anatomy, and their respiratory physiology and immune responses to IAV infection are remarkably similar to what is observed in humans. The pig model shows high face and target validity for human IAV infection, making it suitable for modeling many aspects of influenza, including increased risk of severe disease and impaired vaccine response due to underlying pathologies such as low-grade inflammation. Comparative analysis of proteins involved in viral pattern recognition, interferon responses, and regulation of interferon-stimulated genes reveals a significantly higher degree of similarity between pig, ferret, and human compared with mice. It is concluded that the pig is a promising animal model displaying substantial human translational value with the ability to provide essential insights into IAV infection, pathogenesis, and immunity.

Advax delta inulin adjuvant overcomes immune immaturity in neonatal mice thereby allowing single-dose influenza vaccine protection

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A single dose of Advax-adjuvanted influenza vaccine in 7-day-old pups protected against lethal influenza infection.

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Advax adjuvant enhanced both B-cell and T-cell memory in neonates.

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Influenza protection in Advax-immunized neonates was dependent on memory B-cells.

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Advax adjuvant confirmed to be safe and well tolerated in neonates.

Neonates are at high risk for influenza morbidity and mortality due to immune immaturity and lack of priming by prior influenza virus exposure. Inactivated influenza vaccines are ineffective in infants under six months and to provide protection in older children generally require two doses given a month apart. This leaves few options for rapid protection of infants, e.g. during an influenza pandemic. We investigated whether Advax™, a novel polysaccharide adjuvant based on delta inulin microparticles could help overcome neonatal immune hypo-responsiveness. We first tested whether it was possible to use Advax to obtain single-dose vaccine protection of neonatal pups against lethal influenza infection. Inactivated influenza A/H1N1 vaccine (iH1N1) combined with Advax™ adjuvant administered as a single subcutaneous immunization to 7-day-old mouse pups significantly enhanced serum influenza-specific IgM, IgG1, IgG2a and IgG2b levels and was associated with a 3–4 fold increase in the frequency of splenic influenza-specific IgM and IgG antibody secreting cells. Pups immunized with Advax had significantly higher splenocyte influenza-stimulated IFN-γ, IL-2, IL-4, and IL-10 production by CBA and a 3–10 fold higher frequency of IFN-γ, IL-2, IL-4 or IL-17 secreting T cells by ELISPOT. Immunization with iH1N1 + Advax induced robust protection of pups against virus challenge 3 weeks later, whereas pups immunized with iH1N1 antigen alone had no protection. Protection by Advax-adjuvanted iH1N1 was dependent on memory B cells rather than memory T cells, with no protection in neonatal μMT mice that are B-cell deficient. Hence, Advax adjuvant overcame neonatal immune hypo-responsiveness and enabled single-dose protection of pups against otherwise lethal influenza infection, thereby supporting ongoing development of Advax™ as a neonatal vaccine adjuvant.

Poly I:C adjuvanted inactivated swine influenza vaccine induces heterologous protective immunity in pigs

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Intranasal administration of Poly I:C adjuvanted bivalent swine influenza vaccine induced challenge virus-specific HI antibodies.

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Poly I:C adjuvanted vaccine also induced IgA and IgG antibodies in the lungs.

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Poly I:C adjuvanted vaccine provided protection against antigenic variant and heterologous swine influenza viruses.

Swine influenza is widely prevalent in swine herds in North America and Europe causing enormous economic losses and a public health threat. Pigs can be infected by both avian and mammalian influenza viruses and are sources of generation of reassortant influenza viruses capable of causing pandemics in humans. Current commercial vaccines provide satisfactory immunity against homologous viruses; however, protection against heterologous viruses is not adequate. In this study, we evaluated the protective efficacy of an intranasal Poly I:C adjuvanted UV inactivated bivalent swine influenza vaccine consisting of Swine/OH/24366/07 H1N1 and Swine/CO/99 H3N2, referred as PAV, in maternal antibody positive pigs against an antigenic variant and a heterologous swine influenza virus challenge. Groups of three-week-old commercial-grade pigs were immunized intranasally with PAV or a commercial vaccine (CV) twice at 2 weeks intervals. Three weeks after the second immunization, pigs were challenged with the antigenic variant Swine/MN/08 H1N1 (MN08) and the heterologous Swine/NC/10 H1N2 (NC10) influenza virus. Antibodies in serum and respiratory tract, lung lesions, virus shedding in nasal secretions and virus load in lungs were assessed. Intranasal administration of PAV induced challenge viruses specific-hemagglutination inhibition- and IgG antibodies in the serum and IgA and IgG antibodies in the respiratory tract. Importantly, intranasal administration of PAV provided protection against the antigenic variant MN08 and the heterologous NC10 swine influenza viruses as evidenced by significant reductions in lung virus load, gross lung lesions and significantly reduced shedding of challenge viruses in nasal secretions. These results indicate that Poly I:C or its homologues may be effective as vaccine adjuvants capable of generating cross-protective immunity against antigenic variants/heterologous swine influenza viruses in pigs.