Work

Immunogenicity and Efficacy of CpG-Adjuvanted In-Ovo Recombinant HVT-LT and FPV-LT Vaccines Against Infectious Laryngotracheitis Challenge in 14-Day-Old Broiler Chickens

Year: 2026

Type: article

Abstract: Recombinant herpesvirus of turkey laryngotracheitis (rHVT-LT) and fowlpox virus (rFPV)-LT in-ovoin-ovo vaccines are used for ILT control in broiler chickens. Previously, we showed that in-ovoin-ovo CpG-oligodeoxynucleotide (CpG-ODN) adjuvantation of rHVT-LT can protect broilers against ILT at 28 days of age. Here, we evaluated the immunogenicity and protective efficacy of in-ovoin-ovo CpG-ODN-adjuvanted rHVT-LT and rFPV-LT in broilers when challenged at 14 days of age. Eighteen experimental groups incorporated CpG-ODN-only treatments or those receiving rHVT-LT or rFPV-LT with/without CpG-ODN or non-CpG control ODN in-ovoin-ovo, followed by ILTV challenge at 14 days of age. While none of the vaccinated groups provided significant clinical protection, rHVT-LT+CpG-ODN vaccination showed a numerical reduction (p = 0.0710) in disease severity following ILTV challenge compared with the unvaccinated control. CpG-ODN-only or CpG-ODN-adjuvanted vaccinations followed by challenge resulted in increased (p < 0.05) tracheal and/or splenic TLR21, IL-12, or IFNγ transcription, indicating TLR-mediated antiviral adjuvant effects. Furthermore, CpG-ODN+rHVT-LT/rFPV-LT groups receiving ILTV had increased (p < 0.05) splenic frequencies of macrophages, γδ T cells, B cells, and activated CD4+/CD8+ T cells. Collectively, our findings indicate that in-ovo CpG-ODN adjuvantation with recombinant-vectored ILT vaccines can induce measurable immune activation and a trend toward reduced ILT disease severity following early ILTV challenge in broiler chickens.

Source: Viruses

DOI: 10.3390/v18101096