Protective Oral Vaccination against Infectious bursal disease virus Using the Major Viral Antigenic Protein VP2 Produced in Pichia pastoris

Omid Taghavian,Hafez M Hafez,Rainer Fischer,Holger Spiegel,Rüdiger Hauck,Stefan Schillberg,Anil Kumar Tyagi

doi:10.1371/journal.pone.0083210

Abstract

Infectious bursal disease virus (IBDV) causes economically important immunosuppressive disease in young chickens. The self-assembling capsid protein (VP2) from IBDV strain IR01 was expressed in Pichia pastoris resulting in the formation of homomeric, 23-nm infectious bursal disease subviral particles (IBD-SVPs) with a yield of 76 mg/l before and 38 mg/l after purification. Anti-IBDV antibodies were detected in chickens injected with purified IBD-SVPs or fed with either purified IBD-SVPs or inactivated P. pastoris cells containing IBD-VP2 (cell-encapsulated). Challenge studies using the heterologous classical IBDV strain (MB3) showed that intramuscular vaccination with 20 µg purified IBD-SVPs conferred full protection, achieved complete virus clearance and prevented bursal damage and atrophy, compared with only 40% protection, 0–10% virus clearance accompanied by severe atrophy and substantial bursal damage in mock-vaccinated and challenge controls. The commercial IBDV vaccine also conferred full protection and achieved complete virus clearance, albeit with partial bursal atrophy. Oral administration of 500 µg purified IBD-SVPs with and without adjuvant conferred 100% protection but achieved only 60% virus clearance with adjuvant and none without it. Moderate bursal damage was observed in both cases but the inclusion of adjuvant resulted in bursal atrophy similar to that observed with live-attenuated vaccine and parenteral administration of 20 µg purified IBD-SVPs. The oral administration of 250 mg P. pastoris cells containing IBD-VP2 resulted in 100% protection with adjuvant and 60% without, accompanied by moderate bursal damage and atrophy in both groups, whereas 25 mg P. pastoris cells containing IBD-VP2 resulted in 90–100% protection with moderate bursal lesions and severe atrophy. Finally, the oral delivery of 50 µg purified IBD-SVPs achieved 40–60% protection with severe bursal lesions and atrophy. Both oral and parenteral administration of yeast-derived IBD-VP2 can therefore induce a specific and protective immune response against IBDV without affecting the growth rate of chickens.

Highlights

Infectious bursal disease virus (IBDV) serotype I is an immunosuppressive virus that causes significant morbidity and mortality in young chickens
The 1323-bp mature IBD-VP2 cDNA sequence was amplified from IBDV strain IR01 and transferred to the pPICZ_B vector, containing a C-terminal His6-tag sequence for protein detection and purification
This strain does not grow well in embryonated Specific pathogen free (SPF) eggs and is not cell culture adapted, so birds were infected via the ocular route with 0.1 ml homogenized bursa of Fabricious (BF) from naturally infected chickens, passed through a 0.2-mm filter

Summary

Introduction

Infectious bursal disease virus (IBDV) serotype I is an immunosuppressive virus (genus Avibirnavirus, family Birnaviridae) that causes significant morbidity and mortality in young chickens. When susceptible chickens are infected, IBDV replicates in gut-associated macrophages and lymphoid cells, allowing it to reach the bursa of Fabricius (BF). The virus predominantly targets maturing B lymphocytes in the BF [4] via a4b1 integrin [5]. IBDV induces apoptosis in the peripheral lymphocytes [6] and causes severe immunosuppression and often death in chickens that are 3–6 weeks old, when the BF is in its critical development stage [7]. Infected chickens become susceptible to other diseases and their response to vaccination declines. Younger chickens are passively protected by maternal antibodies transmitted via the egg yolk [8]

Methods

Results

Conclusion