Effectiveness of vaccines against H5 HAPI in chickens
Employing vaccines to control HPAI emerges as a pivotal and significant approach. France has initiated the vaccination of commercial ducks as a recent measure. A new study in the scientific journal Vaccine by a team of American researchers examines the effectiveness of different vaccines. Three vaccines were evaluated for efficacy against TK/IN/22 which is representative of the H5 clade 2.3.4.4b lineage currently circulating (through October 2023) in much of the Americas.
1. An in-house inactivated reverse genetics (rg) vaccine produce with HA gene of TK/IN/22, modified to low pathogenic and a North American lineage N9 neuraminidase (NA) from A/blue winged teal/Wyoming/AH0099021/2016 (H7N9) (SEP-22-N9), in a PR8 backbone (6 genes).
2. rgH5N1 produced with the GF/WA/14 (clade 2.3.4.4c HA gene) and 7 genes from PR8 – Produced by Zoetis.
3. Sequivity vaccine: an alphavirus-derived replicon RNA vaccine (Merck), express the TK/IN/22 H5 HA modified to low pathogenic (an updated commercial RP vaccine).
Virus challenge: A/turkey/Indiana/3703-003/2022 H5N1 clade 2.3.4.4b H5 HPAIV isolate.
Three weeks post vaccination chickens were challenged with a target dose 6.0 log10 50% egg infectious doses (EID50) of TK/IN/22 in 0.1 ml by the intrachoanal route.
PR8 influenza strain = The PR8 strain cultured in chicken eggs is widely used for scientific research and the production of influenza vaccines. PR8 is a mouse-adapted H1N1 influenza virus that is known to cause severe infection in mice.
All vaccines provided 100% protection against mortality and morbidity and all vaccines reduced virus shed by the oropharyngeal and cloacal routes significantly compared to sham vaccinates. However, differences were observed among the vaccines in quantities of virus shed at two- and four-days post challenge (DPC). In conclusion, all three vaccines provided protection against morbidity and mortality and reduced virus shed, demonstrating that they could be utilized to protect against the clade 2.3.4.4 H5 HPAIVs that are currently infecting poultry in the Americas. Because two are licensed in the U.S. and other countries, they can be made available in a reasonably short time frame.
