A Replication-Defective Influenza Virus Harboring H5 and H7 Hemagglutinins Provides Protection against H5N1 and H7N9 Infection in Mice

A single immunization with H5N1 virus-like particle vaccine protects chickens against divergent H5N1 influenza viruses and vaccine efficacy is determined by adjuvant and dosage

The H5N1 subtype highly pathogenic avian influenza virus (HPAIV) reveals high variability and threatens poultry production and public health. To prevent the spread of H5N1 HPAIV, we developed an H5N1 virus-like particle (VLP) vaccine based on the insect cell-baculovirus expression system. Single immunization of the H5N1 VLP vaccines induced high levels of HI antibody titres and provided effective protection against homologous virus challenge comparable to the commercial inactivated vaccine. Meanwhile, we assessed the relative efficacy of different adjuvants by carrying out a head-to-head comparison of the adjuvants ISA 201 and ISA 71 and evaluated whether the two adjuvants could induce broadly protective immunity. The ISA 71 adjuvanted vaccine induced significantly higher levels of Th1 and Th2 immune responses and provided superior cross-protection against antigenically divergent H5N1 virus challenge than the ISA 201 adjuvanted vaccine. Importantly, increasing the vaccine dose could further enhance the cross-protective efficacy of H5N1 VLP vaccine and confer completely sterilizing protection against antigenically divergent H5N1 virus challenge, which was mediated by neutralizing antibodies. Our results suggest that the H5N1 VLP vaccine can provide broad-spectrum protection against divergent H5N1 influenza viruses as determined by adjuvant and vaccine dose.

A Computationally Optimized Broadly Reactive Hemagglutinin and Neuraminidase Vaccine Boosts Antibody-Secreting Cells and Induces a Robust Serological Response, Preventing Lung Damage in a Pre-Immune Model

The hemagglutinin (HA) and neuraminidase (NA) surface proteins are the primary and secondary immune targets for most influenza vaccines. In this study, H2, H5, H7, N1, and N2 antigens designed by the computationally optimized broadly reactive antigen (COBRA) methodology were incorporated into an adjuvant-formulated vaccine to assess the protective efficacy and immune response against A/Hong Kong/125/2017 H7N9 virus challenge in pre-immune mice. The elicited antibodies bound to H2, H5, H7, N1, and N2 wild-type antigens; cH6/1 antigens; and cH7/3 antigens, with hemagglutinin inhibition (HAI) activity against broad panels of the H2Nx, H5Nx, and H7Nx influenza strains. Mice vaccinated with the pentavalent COBRA HA/NA vaccine showed little to no weight loss, no clinical signs of diseases, and were protected from mortality when challenged with the lethal H7N9 virus. Virus titers in the lungs of vaccinated mice were lower and cleared more rapidly than in mock-vaccinated mice. Some vaccinated mice showed no detectable lung injury or inflammation. Antibody-secreting cells were significantly increased in COBRA-vaccinated mice, with higher total Ig and H7-specific ASC. Thus, the combination of H2, H5, H7, N1, and N2 COBRA antigens presents a potential for the formulation of a universal influenza virus vaccine.

Probenecid Inhibits Influenza A(H5N1) and A(H7N9) Viruses In Vitro and in Mice

Avian influenza (AI) viruses cause infection in birds and humans. Several H5N1 and H7N9 variants are highly pathogenic avian influenza (HPAI) viruses. H5N1 is a highly infectious bird virus infecting primarily poultry, but unlike other AIs, H5N1 also infects mammals and transmits to humans with a case fatality rate above 40%. Similarly, H7N9 can infect humans, with a case fatality rate of over 40%. Since 1996, there have been several HPAI outbreaks affecting humans, emphasizing the need for safe and effective antivirals. We show that probenecid potently inhibits H5N1 and H7N9 replication in prophylactically or therapeutically treated A549 cells and normal human broncho-epithelial (NHBE) cells, and H5N1 replication in VeroE6 cells and mice.

Lactoferrin Alleviates Inflammation and Regulates Gut Microbiota Composition in H5N1-Infected Mice

The impact of lactoferrin, an antimicrobial peptide (AMP) with iron-binding properties, on the intestinal barrier and microflora of mice infected with highly pathogenic avian influenza A (H5N1) virus remains unclear. To investigate the effects of lactoferrin on the histopathology and intestinal microecological environment, we conducted a study using H5N1-infected mice. H5N1 infection resulted in pulmonary and intestinal damage, as well as an imbalance in gut microbiota, significantly increasing the abundance of pathogenic bacteria such as Helicobacter pylori and Campylobacter. The consumption of lactoferrin in the diet alleviated lung injury and restored the downregulation of the INAVA gene and intestinal dysfunction caused by H5N1 infection. Lactoferrin not only reduced lung and intestinal injury, but also alleviated inflammation and reversed the changes in intestinal microflora composition while increasing the abundance of beneficial bacteria. Moreover, lactoferrin rebalanced the gut microbiota and partially restored intestinal homeostasis. This study demonstrated that lactoferrin exerts its effects on the intestinal tract, leading to improvements in gut microbiota and restoration of the integrity of both the intestinal wall and lung tissue. These findings support the notion that lactoferrin may be a promising candidate for systemic treatment of influenza by locally acting on the intestine and microbiota.

A replication-deficient H9N2 influenza virus carrying H5 hemagglutinin conferred protection against H9N2 and H5N1 influenza viruses in mice

H5N1 and H9N2 influenza viruses have been reported to cause human infections and are believed to have pandemic potential. The vaccine is an effective tool to prevent influenza virus infection. However, inactivated influenza vaccines sometimes result in low antigenicity as result leads to generating of incomplete immune protection in the form of low cellular and humoral immunity. While the low temperature adapted, traditional live attenuated influenza vaccine (LAIV) is associated with the potential risk to revert to a virulent phenotype, there appears an essential need for an alternative potent methodology to design and develop influenza vaccines with substantial safety and efficacy which may confer solid protection against H9N2 or H5N1 influenza virus infections. In the present study, a replication-deficient recombinant influenza virus, WM01ma-HA(H5), expressing hemagglutinin (HA) of both H9N2 and H5N1 subtypes was developed. The chimeric gene segment expressing HA(H5), was designed using the sequence of an open reading frame (ORF) of HA adopted from A/wild duck/Hunan/021/2005(H5N1)(HN021ma) which was flanked by the NA packaging signals of mouse-adapted strain A/Mink/Shandong/WM01/2014(H9N2)(WM01ma). Due to the absence of ORF of structural protein NA, the replication of this engineered H9N2 influenza viruses WM01ma-HA(H5) was hampered in vitro and in vivo but was well competent in MDCK cells stably expressing the NA protein of WM01ma. Intranasal vaccination of mice with WM01ma-HA(H5) stimulated robust immune response without any clinical signs and conferred complete protection from infection by H5N1 or H9N2 subtype influenza viruses.

Development and application of reverse genetic technology for the influenza virus

Influenza virus is a common virus in people's daily lives, and it has certain infectivity in humans and animals. Influenza viruses have the characteristics of a high mutation rate and wide distribution. Reverse genetic technology is primarily used to modify viruses at the DNA level through targeted modification of the virus cDNA. Genetically modified influenza viruses have a unique advantage when researching the transmission and pathogenicity of influenza. With the continuous development of oncolytic viruses in recent years, studies have found that influenza viruses also have certain oncolytic activity. Influenza viruses can specifically recognize tumor cells; activate cytotoxic T cells, NK cells, dendritic cells, etc.; and stimulate the body to produce an immune response, thereby killing tumor cells. This article will review the development and application of influenza virus reverse genetic technology.