Abstract
Newcastle disease (ND) is a highly fatal, infectious, viral disease, and despite immunization with live and inactivated vaccines, the disease is still endemic, causing heavy morbidity and mortality leading to huge economic losses to the poultry industry in Pakistan. Therefore, the present study was aimed for the first time in the country at using novel virosomal technology to develop the ND vaccine using an indigenous highly virulent strain of the virus. ND virosome was prepared using Triton X-100, and SM2 Bio-Beads were used to remove the detergent and reconstitute the viral membrane into virosome. Confirmation was done by transmission electron microscopy and protein analysis by SDS-PAGE. In vitro cell adhesion property was observed by incorporating green fluorescent protein (GFP), producing plasmid into virosome and in vitro cell culture assay. Sterility, safety, and stability of the vaccine were tested before in vivo evaluation of immunogenicity and challenge protection study in commercial broiler. The virosome vaccine was administered (30 μg/bird) at days 7 and 14 through the intranasal route in comparison with commercially available live and inactivated ND vaccines. Results revealed significantly high (p < 0.05) and clinically protective hemagglutination inhibition (HI) antibody titers at 7, 14, 21, and 28 days postimmunization with the virosome vaccine in comparison to the negative control. The GMTs were comparable to live and inactivated vaccines with nonsignificant (p > 0.05) differences throughout the experiment. Antibody levels increased in all vaccinated groups gradually from the 7th day and were maximum at 28th-day postvaccination. In the virosome-administered group, GMT was 83.18 and 77.62 at 21st and 28th-days postvaccination, respectively. Challenge revealed 100%, 90%, and 80% protection in virosome, live, and inactivated vaccinated groups, respectively. Under given experimental conditions, we can conclude that ND virosome vaccine prepared from the indigenous virus was found to be safe and immunogenic.
Highlights
The poultry industry is one of the leading industries and a source of income for more than 21 million people, contributing 23.8% of total meat production in Pakistan
Indigenous ND virus was successfully isolated from field outbreaks of Newcastle disease in commercial broiler birds from in and around the Okara district of Punjab, Pakistan, from June 2017 to March 2018
The Mean Death Time (MDT) score was less than 50 hours and 108.5 Embryo Lethal Dose50 (ELD50)/ml, which indicates that all the local isolates of Newcastle disease virus (NDV) from filed outbreaks were highly virulent or velogenic
Summary
The poultry industry is one of the leading industries and a source of income for more than 21 million people, contributing 23.8% of total meat production in Pakistan. The outbreaks of ND have been reported from all continents of the world including Africa, Asia, Europe, Australia, and South and Central America [1, 2] This is one of the deadliest infections of poultry and results in heavy mortality in all ages of chicken [3, 4]. According to the International Committee on Taxonomy of Viruses (ICTV), Newcastle disease virus (NDV) belongs to the family Paramyxoviridae, subfamily Paramyxovirinae, and genus Avulavirus. It is the only member of Avian Paramyxovirus Type 1 (APMV-1) and affects all the domestic and wild birds [5]. These include a large RNA-dependent RNA polymerase (L), HemagglutininNeuraminidase (HN), Fusion protein (F), Matrix protein (M), Phosphoprotein (P), and Nucleoprotein (NP) [6, 7]
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