Cytokine expression, protection and shedding reduction induced by the combination of lipopolysaccharide with Montanoid ISA71 in oil-based Newcastle disease vaccine.

Oil-based inactivated ND vaccines are a commonly used control strategy for this endemic disease in Egypt. One of the major limitations of these inactivated vaccines is the time taken to develop a protective response in vaccinated birds. In the present study, we aimed to formulate an inactivated oil-based ND vaccine incorporated with lipopolysaccharide (LPS) that stimulates the early onset innate response to inactivated vaccines via proinflammatory cytokine production. Five groups of 21-day old SPF chicks were reared in isolators and were treated as follows: G1: Montanoid ISA71 adjuvanted NDV vaccinated group, G2: LPS and Montanoid ISA71 adjuvanted NDV vaccinated group, G3: LPS and Montanoid ISA71 with phosphate buffer saline received group and two non-vaccinated control groups. NDV specific antibodies and cell mediated immune responses were evaluated by hemagglutination inhibition and lymphocyte proliferation tests, respectively. Transcriptional responses of the TLR4, IFN-γ and IL-2 genes were analyzed in peripheral blood mononuclear cells (PBMCs) following vaccination by qRT-PCR. Protection % was determined after challenge with a lethal strain of NDV 106 EID50/0.5 ml. Viral shedding was assessed on oropharyngeal swabs by qRT-PCR and infectivity titration on SPF-ECE. The results revealed that the incorporation of LPS with ISA71 in the oil-based ND vaccine induced a synergistic response confirmed by significant humoral and lymphoproliferative responses with a significant increase in Th1 cytokine transcripts. The simultaneous use of both adjuvants in G2 demonstrated complete protection and a significant reduction in viral shedding compared to the ISA71-adjuvated ND vaccine in G1, which conferred 90 % protection.

Genotypes II and VIId-based inactivated Newcastle disease vaccine reduces virus shedding.

In Egypt, recent outbreaks were reported in NDV-vaccinated flocks. The isolated strain was characterized as class II velogenic genotype VIId of Newcastle disease virus (NDV). In this study, three inactivated NDV vaccine formulations were prepared, the first one is LaSota (genotype II), the second one is genotype VIId and the third one is combined Lasota and genotype VIId at a proportion of 1:1. The challenge trials were conducted in SPF chicks to evaluate the efficacy of the prepared vaccines using 106 EID50/0.5 ml of the Egyptian genotype VIId strain of Newcastle disease virus (NDV-B7-RLQP-CH-EG-12). Our results revealed that all three prepared vaccine formulations conferred 100% protection in the vaccinated chicks. However, the combined vaccine induced the highest haemagglutination inhibition (HI) titers and neutralization indices with significant reduction in virus shedding compared to other vaccine formulations. Histopathology examination of different organs collected from vaccinated chicks post challenge indicated the protective efficacy in vaccinated groups compared to the positive control group where a score of severe lesions was shown. This study reports the efficacy of combined inactivated Lasota and genotype VIId vaccine in reducing virus shedding which is very important in controlling NDV infection in chicken.