Improved hatchability and efficient protection after in ovo vaccination with live-attenuated H7N2 and H9N2 avian influenza viruses

Abstract

Mass in ovo vaccination with live attenuated viruses is widely used in the poultry industry to protect against various infectious diseases. The worldwide outbreaks of low pathogenic and highly pathogenic avian influenza highlight the pressing need for the development of similar mass vaccination strategies against avian influenza viruses. We have previously shown that a genetically modified live attenuated avian influenza virus (LAIV) was amenable for in ovo vaccination and provided optimal protection against H5 HPAI viruses. However, in ovo vaccination against other subtypes resulted in poor hatchability and, therefore, seemed impractical. In this study, we modified the H7 and H9 hemagglutinin (HA) proteins by substituting the amino acids at the cleavage site for those found in the H6 HA subtype. We found that with this modification, a single dose in ovo vaccination of 18-day old eggs provided complete protection against homologous challenge with low pathogenic virus in ≥70% of chickens at 2 or 6 weeks post-hatching. Further, inoculation of 19-day old egg embryos with 106 EID50 of LAIVs improved hatchability to ≥90% (equivalent to unvaccinated controls) with similar levels of protection. Our findings indicate that the strategy of modifying the HA cleavage site combined with the LAIV backbone could be used for in ovo vaccination against avian influenza. Importantly, with protection conferred as early as 2 weeks post-hatching, with this strategy birds would be protected prior to or at the time of delivery to a farm or commercial operation.

In ovodelivery of various biological supplements, vaccines and drugs in poultry: current knowledge

“…Plasmid DNA‐based ND vaccine constituting internal ribosome entry site‐HN/F has also been found to be suitable for in ovo application, inducing high antibody titer against NDV . Some workers have also reported that improved hatchability and efficient protection is achieved after in ovo vaccination with live‐attenuated H7N2 and H9N2 AI virus vaccines . In ovo vaccination against Marek's disease virus using turkey herpesvirus has been reported to hasten immune system maturation and can result in the production of immunocompetent chicks in a commercial set‐up …”

“…154 Some workers have also reported that improved hatchability and efficient protection is achieved after in ovo vaccination with live-attenuated H7N2 and H9N2 AI virus vaccines. 155 In ovo vaccination against Marek's disease virus using turkey herpesvirus has been reported to hasten immune system maturation and can result in the production of immunocompetent chicks in a commercial set-up. 156 Researchers have documented the positive effects of in ovo vaccination with diluent containing commercial coccidiosis vaccine (Inovocox EM1 vaccine) in Ross 708 broilers against coccidiosis by determining an increase in feed intake, BW gain, feed conversion ratio, and reduction in mortality up to the study period of 14 days of post-hatch age.…”

Live attenuated H5N1 vaccine with H9N2 internal genes protects chickens from infections by both Highly Pathogenic H5N1 and H9N2 Influenza Viruses

“…Thus, development of an effective vaccine is necessary to protect poultry and minimize human infections. Several approaches, including live attenuation and inactivation, have been carried out to develop a vaccine capable of protecting poultry from infection by H5N1 or H9N2 viruses 28–43 . An attractive approach for the vaccination of poultry would be a live attenuated vaccine, which can be inoculated on a large scale, and induces IgA antibodies that are important for mucosal immunity.…”

Development of Live-Attenuated Influenza Vaccines against Outbreaks of H5N1 Influenza

“…The temperature-sensitive H5N1 LAIV could provide effective protection for poultry and mice against the HPAI H5N1 virus challenge [20,21]. Moreover, their further research indicated that the modified WF10 backbone could be used to prepare H7N2 and H9N2 LAIVs for in ovo vaccination against avian influenza [35]. Due to the outbreak caused by the novel swine-origin influenza (H1N1) in 2009, Perez’s group further demonstrated that the double attenuating mutations implemented for the WF10 virus could be transferred to swine-like influenza viruses (A/turkey/Ohio/313053/04 (H3N2) or A/swine/Wisconsin/14094/99 (H3N2)), and the obtained H3N2 LAIV could induce excellent protection against aggressive H1N1 virus challenges in more than one animal model [36,37].…”