Protection against infectious bronchitis virus by spike ectodomain subunit vaccine

Area of Science:

• Veterinary Virology
• Immunology
• Molecular Biology

Background:

• Infectious bronchitis virus (IBV) spike (S) glycoprotein's S1 subunit mediates host cell attachment, while the S2 subunit facilitates membrane fusion.
• Current vaccination strategies using S1 alone provide inadequate protection against IBV challenge.
• The S2 ectodomain's contribution to binding chicken tissues suggests its potential role in enhancing vaccine efficacy.

Purpose of the Study:

• To evaluate the protective efficacy of recombinant IBV S-ectodomain protein compared to S1 protein in chickens.
• To investigate the role of the S2 domain in inducing protective immunity against IBV.

Main Methods:

• Chickens were immunized with either recombinant S1 or S-ectodomain proteins derived from IBV Arkansas-type (Ark).
• Immunization involved a prime and a boost, followed by challenge with virulent Ark IBV.
• Viral loads, tracheal mucosal thickness, and lesion scores were assessed post-challenge.

Main Results:

• Chickens immunized with S-ectodomain protein exhibited significantly reduced viral loads in tears and tracheas.
• Significantly lower tracheal mucosal thickness and lesion scores were observed in the S-ectodomain group.
• These findings indicate enhanced protection of tracheal integrity with S-ectodomain vaccination.

Conclusions:

• The S2 domain plays a crucial role in inducing protective immunity against IBV.
• Including the S2 domain with S1 in vaccine formulations may lead to improved viral vectored and subunit vaccines.
• Recombinant S-ectodomain protein shows promise for developing more effective IBV vaccines.