title: Adjuvant potential of resiquimod with inactivated Newcastle disease vaccine and its mechanism of action in chicken.
abstract: Resiquimod (R-848), an imidazoquinoline compound, is a potent synthetic Toll-like receptor (TLR) 7 agonist. Although the solitary adjuvant potential of R-848 is well established in mammals, such reports are not available in avian species hitherto. Hence, the adjuvant potential of R-848 was tested in SPF chicken in this study. Two week old chicks were divided into four groups (10 birds/group) viz., control (A), inactivated Newcastle disease virus (NDV) vaccine prepared from velogenic strain (B), commercial oil adjuvanted inactivated NDV vaccine prepared from lentogenic strain (C) and inactivated NDV vaccine prepared from velogenic strain with R-848 (D). Booster was given two weeks post primary vaccination. Humoral immune response was assessed by haemagglutination inhibition (HI) test and ELISA while the cellular immune response was quantified by lymphocyte transformation test (LTT) and flow cytometry post-vaccination. Entire experiment was repeated twice to check the reproducibility. Highest HI titre was observed in group D at post booster weeks 1 and 2 that corresponds to mean log2 HI titre of 6.4 ± 0.16 and 6.8 ± 0.13, respectively. The response was significantly higher than that of group B or C (P<0.01). LTT stimulation index (P ≤ 0.01) as well as CD4(+) and CD8(+) cells in flow cytometry (P<0.05) were significantly high and maximum in group D. Group D conferred complete protection against virulent NDV challenge, while it was only 80% in group B and C. To understand the effects of R-848, the kinetics of immune response genes in spleen were analyzed using quantitative real-time PCR after R-848 administration (50 μg/bird, i.m. route). Resiquimod significantly up-regulated the expression of IFN-α, IFN-β, IFN-γ, IL-1β, IL-4, iNOS and MHC-II genes (P<0.01). In conclusion, the study demonstrated the adjuvant potential of R-848 when co-administered with inactivated NDV vaccine in SPF chicken which is likely due to the up-regulation of immune response genes.
authors.affiliation: Immunology Section, Indian Veterinary Research Institute (IVRI), Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: Swati
authors.initials: S
authors.lastname: Sachan
authors.affiliation: Immunology Section, Indian Veterinary Research Institute (IVRI), Izatnagar, Bareilly, Uttar Pradesh 243122, India. Electronic address: dearsaromib@yahoo.com.
authors.forename: Saravanan
authors.initials: S
authors.lastname: Ramakrishnan
authors.affiliation: Immunology Section, Indian Veterinary Research Institute (IVRI), Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: Arunsaravanakumar
authors.initials: A
authors.lastname: Annamalai
authors.affiliation: Immunology Section, Indian Veterinary Research Institute (IVRI), Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: Bal Krishan
authors.initials: BK
authors.lastname: Sharma
authors.affiliation: Division of Veterinary Public Health, IVRI, Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: Hina
authors.initials: H
authors.lastname: Malik
authors.affiliation: Division of Parasitology, IVRI, Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: B C
authors.initials: BC
authors.lastname: Saravanan
authors.affiliation: Division of Biological Standardisation, IVRI, Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: Lata
authors.initials: L
authors.lastname: Jain
authors.affiliation: Division of Animal Biochemistry, IVRI, Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: Meeta
authors.initials: M
authors.lastname: Saxena
authors.affiliation: Division of Animal Biochemistry, IVRI, Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: Ajay
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Division of Animal Reproduction, IVRI, Izatnagar, Bareilly, Uttar Pradesh 243122, India.
authors.forename: Narayanan
authors.initials: N
authors.lastname: Krishnaswamy
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D002645:Chickens; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D006385:Hemagglutination Inhibition Tests; D007093:Imidazoles / Q000008:administration & dosage*; D008214:Lymphocytes / Q000276:immunology; D009521:Newcastle Disease / Q000517:prevention & control*; D015164:Vaccines, Inactivated / Q000008:administration & dosage; D014765:Viral Vaccines / Q000008:administration & dosage*
chemical_list: D000276:Adjuvants, Immunologic; D000914:Antibodies, Viral; D007093:Imidazoles; D015164:Vaccines, Inactivated; D014765:Viral Vaccines; C402365:resiquimod
keywords: Adjuvant; Chicken; Cytokines; Immune response genes; Newcastle disease; Resiquimod; TLR agonist