Preparation of cell-associated vaccine from attenuated infectious laryngeotracheitis (ILT)‎ virus

Abstract EN

The present work was carried out to develop cell-associated (CA) vaccine prepared from chicken embryo fibroblast (CEF) cells infected with the tissue-culturemodified strain of infectious laryngotracheitis (ILT).

The titer of prepared vaccine was 6 log10 TCID50 before and 5.7 following preservation.

The vaccine was free from bacteria and other detectable viral agents by all the usual safety tests.

Immunization was successful by using the prepared ILT vaccine subcutaneously in one-day-old specified pathogen-free (SPF) chicks.

No clinical signs, gross and histopathological lesions related to ILT were observed in vaccinated group, as well as contact and control groups, in addition, the CA vaccine was safe when chickens were inoculated with 10 doses.

The use of serum neutralization test and ELISA indicated that chicks inoculated with prepared ILT vaccine acquired high virus-neutralizing antibody titers at 14, and 21 days postvaccination and these titers persisted in protective levels up to ten weeks post vaccination.

On challenge, 93.3 % protection was achieved in vaccinated groups.

On the contrary all the birds in control group and chicks contact-exposed to vaccinated groups showed sever clinical signs and microscopic tracheal lesions with high mortality rates post-challenge.

It is concluded that this experimental vaccine was effective for chickens, eliciting protection effect against challenge with a virulent strain of ILT virus without any clinical signs.