In ovo CpG DNA delivery increases innate and adaptive immune cells in respiratory, gastrointestinal and immune systems post-hatch correlating with lower infectious laryngotracheitis virus infection

Abstract

Cytosine-guanosine deoxynucleotides (CpG) DNA can be delivered in ovo at embryo day (ED)18 for the stimulation of toll-like receptor (TLR)21 signaling pathway that ultimately protects chickens against a number of bacterial and viral infections. There is a dearth of information understanding the mechanisms of protection induced by in ovo delivered CpG DNA. The objective of this study was to determine the immune cell changes post-hatch following in ovo delivery of the TLR21 ligand, CpG DNA. In order to quantify changes of percentage of KUL01+, IgM+ B, cluster of differentiation (CD)4+ and CD8α+ cells, trachea, lung, duodenum, large intestine, spleen and bursa of Fabricius were collected on day 1 post-hatch. We found increased recruitments of KUL01+ cells, in organs of these body systems post-hatch following in ovo delivery of CpG DNA. Although IgM+ B cells, CD4+ and CD8α+ cells were increased in lungs and immune system organs, these cells were not quantifiable from the trachea, duodenum and large intestine immediately following the hatch. Furthermore, when CpG DNA is delivered in ovo and subsequently infected with infectious laryngotracheitis virus (ILTV) post-hatch on day 1, CpG DNA reduces morbidity and mortality resulting from ILTV infection. This study provides insights into the mechanisms of host responses elicited following in ovo delivery of CpG DNA in avian species.

The In Ovo Delivery of CpG Oligonucleotides Protects against Infectious Bronchitis with the Recruitment of Immune Cells into the Respiratory Tract of Chickens

“…The host survival after day 1 post-hatch IBV infection was seen as significant in the presence of CpG ODN administration in ovo compared with the controls, and a similar protective effect of in ovo delivered CpG ODNs has been recorded against the post-hatch ILTV infection [ 21 , 22 ], and E. coli and Salmonella Thypimurium septicemia [ 18 , 19 ]. In the current study, the protection-mediated by the in ovo administered CpG ODNs was associated with significantly lower IBV replication in the trachea and IBV genome loads in the lungs at 3 and 7 dpi.…”

“…In ovo delivery targets the deposition of CpG ODNs in the amniotic cavity. Subsequently, the ingestion of CpG ODNs containing amniotic fluid by the developing embryo distributes CpG ODNs in the respiratory and gastrointestinal tracts, leading to immune cell recruitment in these two body systems [ 22 ]. We have shown in this study that CpG ODNs when delivered in ovo are capable of protecting young chickens against a post-hatch IBV infection induced IB.…”

“…Several studies have demonstrated the immunostimulatory and therapeutic success of CpG oligodeoxynucleotides (ODNs) application in various host–pathogen interaction models [ 18 , 19 , 20 ]. The protection provided by CpG ODNs against lethal challenges of extracellular bacteria, such as Escherichia coli [ 18 ] and Salmonella Typhimurium [ 19 ], and viruses, such as low pathogenic avian influenza virus [ 20 ] and infectious laryngotracheitis virus (ILTV) [ 21 , 22 ], in chickens have been well documented. CpG ODNs are known to induce an array of cytokines; chemokines; and effecter molecules, such as interferon (IFN) α, β and γ, interleukin (IL)-1β, IL-6, IL-12, IL-8, tumor necrosis factor (TNF)-α, and nitric oxide (NO) [ 23 , 24 , 25 ].…”

Avian Pattern Recognition Receptor Sensing and Signaling

“…Furthermore, an increase in cells of adaptive immune system was noticed in spleen and bursa of hatched chicks. The increased cell recruitment correlated with a reduction in morbidity, mortality, and ILTV cloacal excretion due to ILTV challenge [197]. However, no reduction in oropharyngeal ILTV loads was noticed.…”

“…In ovo administration of class B CpG ODN 2007 in ED18 SPF embryos resulted in increased numbers of KUL01+ macrophages, IgM+ B cells, and CD4+ and CD8α+ cells in lungs of chicks on the day of hatch compared to non-CpG DNA or saline-inoculated embryos [197]. Furthermore, an increase in cells of adaptive immune system was noticed in spleen and bursa of hatched chicks.…”