Influenza virus‐like particles harboring H9N2 HA and NA proteins induce a protective immune response in chicken

Abstract

BackgroundAvian influenza viruses represent a growing threat of an influenza pandemic. The co‐circulation of multiple H9N2 genotypes over the past decade has been replaced by one predominant genotype—G57 genotype, which displays a changed antigenicity and improved adaptability in chickens. Effective H9N2 subtype avian influenza virus vaccines for poultry are urgently needed.ObjectiveIn this study, we constructed H9N2 subtype avian influenza virus‐like particle (VLP) and evaluated its protective efficacy in specific pathogen‐free (SPF) chickens to lay the foundation for developing an effective vaccine against influenza viruses.MethodsExpression of influenza proteins in VLPs was confirmed by Western blot, hemagglutination inhibition (HI), and neuraminidase inhibition (NI). The morphology was observed by electron microscopy. A group of 15 three‐week‐old SPF chickens was divided into three subgroups of five chickens immunized with VLP, commercial vaccine, and PBS. Challenge study was performed to evaluate efficacy of VLP vaccine.Results and ConclusionsThe hemagglutinin (HA) and neuraminidase (NA) proteins were co‐expressed in the infected cells, self‐assembled, and were released into the culture medium in the form of VLPs of diameter ~80 nm. The VLPs exhibited some functional characteristics of a full influenza virus, including hemagglutination and neuraminidase activity. In SPF chickens, the VLPs elicited serum antibodies specific for H9N2 and induced a higher HI titer (as detected by a homologous antigen) than did a commercial H9N2 vaccine (A/chicken/Shanghai/F/1998). Viral shedding from VLP vaccine subgroup was reduced compared with commercial vaccine subgroup and control subgroup.

Universal Vaccines and Vaccine Platforms to Protect against Influenza Viruses in Humans and Agriculture

“…Although these are non-replicating particles, they retain the morphology of the virus and, therefore, the antigenicity and can activate innate immunity. VLPs can be produced in several expression systems, including baculovirus-, insect cell-, bacteria-, or plant-derived systems (Low et al, 2014 ; Pillet et al, 2016 ; Valero-Pacheco et al, 2016 ; Li et al, 2017 ). In a double-blind, randomized phase I clinical trial, Low and colleagues showed that a non-adjuvanted H1NIpdm09 VLP vaccine was safe and resulted in seroconversion in more than 50% of the subjects with just one dose, and this percentage increased after boost (Low et al, 2014 ).…”

“…This cross-reactive response was also observed in chickens vaccinated with triple-subtype (H5, H7, and H9) VLPs that were protected against challenge with heterologous HPAI H5N2 and H7N3 and LPAI H9N2 (Pushko et al, 2017 ). Vaccination of chickens with adjuvanted VLPs expressing H9N2 HA and NA also induced robust HI antibodies and reduced viral shedding after homologous challenge (Li et al, 2017 ). In pigs, VLP antigens consisting of H1N1pdm09 HA, NA, and M1 proteins elicited robust levels of humoral and mucosal immune responses and protected pigs against homologous infection (Pyo et al, 2012 ).…”

Review: A systematic review of virus-like particles of coronavirus: Assembly, generation, chimerism and their application in basic research and in the clinic

“…Since influenza virus is a huge threat to public health, flu VLP development has been a hot research topic in recent years. Influenza VLPs have been generated by co-expressing its structural proteins: matrix 1 (M1) + hemagglutinin (HA) [88] , [89] , HA + neuraminidase (NA) [90] , HA + NA + M1 [91] , [92] , [93] , or HA + NA + M1 + matrix 2 (M2) [94] . Influenza VLPs have been shown to induce protective immune responses and can serve as a platform for the expression of foreign proteins.…”

Progress in the development of virus-like particle vaccines against respiratory viruses

“…Intramuscular immunization with M8-VLP induced long-lasting protective antibody responses against influenza virus in mice. Intramuscular immunization with Freund's adjuvanted H9N2 influenza VLP containing HA and NA induced high levels of HAI titers with significant reduction in virus shedding and substantial homologous protection in chickens [88]. Adjuvants Alum, CpG DNA, monophosphoryl lipid A (MPL), poly IC, gardiquimod, and cholera toxin (CT) have been used to assess immunity in combination with influenza VLPs in mice [89].…”