|LE GROS, FRANCOIS-XAVIER|
Submitted to: Avian Influenza Symposium International Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2006
Publication Date: 4/3/2006
Citation: Bublot, M., Le Gros, F., Nieddu, D., Pritchard, N., Mickle, T.R., Swayne, D.E. 2006. Efficacy of two inactivated vaccines against an Asian HPAI H5N1 challenge. In: 6th International Symposium on Avian Influenza, April 3-6, 2006, Cambridge,United Kingdom. p.35.
Technical Abstract: The objective of the study was to compare the efficacy of inactivated vaccines containing either an American isolate (A/turkey/Wisconsin/68 H5N9; GALLIMUNE FLU H5N9 or H5N9-WI) or an Eurasian isolate (A/chicken/Italy/22A/98 H5N9 or H5N9-It). Three weeks-old SPF chickens were vaccinated and challenged three weeks later with an HPAI A/chicken/Thailand/04 H5N1 isolate. All unvaccinated birds died within 2 days, whereas 95% and 100% of chickens vaccinated with H5N9-WI and H5N9-It were protected. Cloacal shedding was detected in 2/20 and 0/20 chickens vaccinated with H5N9-WI and H5N9-It, respectively, whereas unvaccinated controls were all positive (20/20) with a mean titer of 3.9 log10 EID50/ml. Reduction of oral shedding was approx. 1.5 log10 and 2.2 log10 with H5N9-WI and H5N9-It vaccines, respectively. Additional chickens (H5N9-WI-vaccinated or not) were placed in contact with the non-vaccinated challenged birds 18 hours after challenge. All unvaccinated contact chickens died within 3 days, whereas all H5N9-WI vaccinated contact chickens were protected against mortality/morbidity. Cloacal shedding after contact challenge was not detected and oral shedding was reduced by more than 3.5 log10 in the H5N9-WI –vaccinated group. Chickens (vaccinated or not) were also placed in contact with challenged-vaccinated ones. All vaccinated chickens were protected after contact with these challenged-vaccinated birds. However, 10/10 and 5/10 unvaccinated chickens in contact with challenged-vaccinated birds (H5N9-WI and H5N9-It, respectively) died within 9 days. Altogether these data indicate that (1) both vaccines protected very well against mortality/morbidity and shedding induced by direct or contact HPAI Asian H5N1 challenge, (2) the amount of virus shed from vaccinated-challenged chickens was sufficient to infect non-vaccinated contacts but it was insufficient to infect vaccinated contacts, (3) the H5N9-It vaccine tended to be more protective than the H5N9-WI one.