Effect of CpG-Oligonucleotide in Enhancing Recombinant Herpes Virus of Turkey-Laryngotracheitis Vaccine-Induced Immune Responses in One-Day-Old Broiler Chickens

Abstract

Infectious laryngotracheitis (ILT) is an economically important disease of chickens. While the recombinant vaccines can reduce clinical disease severity, the associated drawbacks are poor immunogenicity and delayed onset of immunity. Here, we used CpG-oligonucleotides (ODN) as an in ovo adjuvant in boosting recombinant herpesvirus of turkey-laryngotracheitis (rHVT-LT) vaccine-induced responses in one-day-old broiler chickens. Two CpG-ODN doses (5 and 10 μg/egg) with no adverse effect on the vaccine-virus replication or chick hatchability were selected for immune-response evaluation. Results showed that while CpG-ODN adjuvantation induced an increased transcription of splenic IFNγ and IL-1β, and lung IFNγ genes, the IL-1β gene expression in the lung was significantly downregulated compared to the control. Additionally, the transcription of toll-like receptor (TLR)21 in the spleen and lung and inducible nitric oxide synthase (iNOS) in the spleen of all vaccinated groups was significantly reduced. Furthermore, splenic cellular immunophenotyping showed that the CpG-ODN-10μg adjuvanted vaccination induced a significantly higher number of macrophages, TCRγδ+, and CD4+ T cells as well as a higher frequency of activated T cells (CD4+CD44+) when compared to the control. Collectively, the findings suggested that CpG-ODN can boost rHVT-LT-induced immune responses in day-old chicks, which may help in anti-ILT defense during their later stages of life.

In Ovo Vaccination with Recombinant Herpes Virus of the Turkey-Laryngotracheitis Vaccine Adjuvanted with CpG-Oligonucleotide Provides Protection against a Viral Challenge in Broiler Chickens

“…In the present study, we extended our previous findings [ 22 ] to evaluate the protective efficacy of class B CpG-ODN adjuvated rHVT-LT vaccine in broiler chickens challenged with ILTV. To determine the possible immune mechanisms, splenic immune gene expression and cellular responses were evaluated.…”

“…Spleens were collected from all the treatment groups ( n = 6) in RNAlater solution (Invitrogen, Carlsbad, CA, USA) from the chickens during terminal necropsy and stored at −80 °C until processing. The tissues were homogenized and the total RNA was extracted followed by cDNA synthesis, as described previously [ 22 ]. Quantitative real-time reverse-transcriptase PCR using SYBR Green was performed on the diluted cDNA using a QuantStudio 6 Flex System and QuantStudio Real-Time PCR Software (Applied Biosystems, Waltham, MA, USA).…”

“…Single-cell splenocyte preparations ( n = 8 per group) were made following a protocol described previously [ 22 ]. The cells were stained in three different panels of antibody staining due to the paucity of chicken antibody reagents available in multi-color formats.…”

“…For example, a class B CpG-ODN molecule administered in ovo has been shown to activate monocytes, B cells, and CD4+ T cells [ 17 , 18 , 19 ], and boost immune responses against vaccine antigens [ 19 , 20 , 21 ]. Recently, we showed that an adjuvantation of rHVT-LT with CpG-ODN (class B) can enhance rHVT-LT vaccine-induced immune responses in one-day-old broiler chickens [ 22 ]. We found that the adjuvanted vaccination resulted in significantly increased expressions of interferon (IFN)γ, interleukin (IL)-1β, and inducible nitric oxide synthase (iNOS) genes in the lung and spleen tissues, as well as an enhanced splenic macrophage, γδ T cells, and activated CD4+ T cell responses.…”

Mechanisms of type I interferon production by chicken TLR21

“…While the CpG-ODNs with the AACGTT motif are not well studied in birds, those with the CTCGTT or GACGTT motifs have already shown adjuvant activity (Lee et al, 2010). The broad CpG-ODN sequence recognition profile exhibited by chicken and duck TLR21 implies a wide range of CpG-ODN options that can be used as adjuvants in vaccines or as immune-modulators (Bavananthasivam et al, 2018; De Silva Senapathi et al, 2018; Gaghan et al, 2023; Scheiermann and Klinman, 2014). Moreover, CpG-ODN can be administered to chickens through different routes, including oral, intranasal, subcutaneous, and in ovo injections (De Silva Senapathi et al, 2018; Talebi and Arky-Rezai, 2019).…”