Studies on Nanoparticle Based Avian Influenza Vaccines to Present Immunogenic Epitopes of the Virus with Concentration on Ectodomain of Matrix 2 (M2e) Protein
Avian influenza is an infectious disease of avian species caused by type A influenza viruses with a significant economic impact on the poultry industry. Vaccination is the main prevention strategy in many countries worldwide. However, available vaccines elicit antibodies against two major surface protein of the virus hemagglutinin (HA) and neuraminidase (NA), where they constantly change by point mutations. Influenza viruses can also easily undergo gene reassortment. Therefore, to protect chickens against new strain of avian influenza virus, as well as control and prevent virus spread among farms, new vaccines needed to be designed which is a tedious, time consuming and expensive. Recently, conserved regions of the influenza genome have been evaluated as possible universal vaccines to eliminate constant vaccine updates based on circulating virus. In this study, peptide nanotechnology was used to generate vaccine nanoparticles that carry the highly conserved external domain of matrix 2 protein (M2e). These nanoparticles presented M2e in monomeric or tetrameric forms, designated as PSC-M2e-CH and BNSC-M2eN-CH, respectively. First, to demonstrate immunogenicity of these nanoparticles, we measured anti-M2e antibody in chickens, particularly when a high dose was applied. Prior to vaccination-challenge study, the challenge dose were determined by oculonasal inoculation of 106 EID50 or 107.7 EID50 of low pathogenicity AI virus HSN2 followed by measuring cloacal and tracheal virus shedding. A biphasic virus shedding pattern was observed with two peaks of virus shedding at days 4 and 8 for both tracheal and cloacal swabs. The chickens infected with 107.7 EID 50 had significant virus shedding as compared with 106 EID50.
Based on results of mentioned studies, a vaccination-challenge study was conducted by using 75μg of each vaccine construct per inoculation (with and without adjuvant) and higher dose of virus for challenge. BN5C-M2e-CH with adjuvant significantly reduced the tracheal virus shedding compared with the positive challenge control and offered significant protection by expediting clearance of the virus in infected chickens. Reduction in cloacal virus shedding was not significant because cloacal shedding is low by nature. These results demonstrate that nanoparticles are a promising platform for immunogenic epitope delivery and M2e is a promising vaccine candidate against low pathogenicity avian influenza (LPAI) viruses.