Pathogen adaptations during host-pathogen co-evolution can cause the host balance between immunity and immunopathology to rapidly shift. However, little is known in natural disease systems about the immunological pathways optimised through the trade-off between immunity and self-damage. The evolutionary interaction between the conjunctival bacterial infection Mycoplasma gallisepticum (MG) and its avian host, the house finch (Haemorhous mexicanus), can provide insights into such adaptations in immune regulation. Here we use experimental infections to reveal immune variation in conjunctival tissue for house finches captured from four distinct populations differing in the length of their co-evolutionary histories with MG and their disease tolerance (defined as disease severity per pathogen load) in controlled infection studies. To differentiate contributions of host versus pathogen evolution, we compared house finch responses to one of two MG isolates: the original VA1994 isolate and a more evolutionarily derived one, VA2013. To identify differential gene expression involved in initiation of the immune response to MG, we performed 3'-end transcriptomic sequencing (QuantSeq) of samples from the infection site, conjunctiva, collected 3-days post-infection. In response to MG, we observed an increase in general pro-inflammatory signalling, as well as T-cell activation and IL17 pathway differentiation, associated with a decrease in the IL12/IL23 pathway signalling. The immune response was stronger in response to the evolutionarily derived MG isolate compared to the original one, consistent with known increases in MG virulence over time. The host populations differed namely in pre-activation immune gene expression, suggesting population-specific adaptations. Compared to other populations, finches from Virginia, which have the longest co-evolutionary history with MG, showed significantly higher expression of anti-inflammatory genes and Th1 mediators. This may explain the evolution of disease tolerance to MG infection in VA birds. We also show a potential modulating role of BCL10, a positive B- and T-cell regulator activating the NFKB signalling. Our results illuminate potential mechanisms of house finch adaptation to MG-induced immunopathology, contributing to understanding of the host evolutionary responses to pathogen-driven shifts in immunity-immunopathology trade-offs.

• Keywords
• adaptations diversifying populations, coevolution, emerging disease, host-pathogen interaction, inflammatory immune response, parasite, resistance, tolerance to infection,
• MeSH
• Immunity MeSH
• Conjunctiva MeSH
• Mycoplasma Infections * veterinary   microbiology   MeSH
• Finches * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

BACKGROUND: Interleukin-22 (IL-22) is a pro-inflammatory cytokine released during the immune response in chronic liver injury. Although IL-22 mediates tissue regeneration, its uncontrolled production may generate a carcinogenic environment resulting in hepatocellular carcinoma (HCC). This study aims to identify the effect of IL-22 on anti-apoptotic and metastatic genes and the molecular pathways responsible for IL-22-mediated hepatic carcinogenesis. METHODS AND RESULTS: Three cancerous liver lines, HepG2, SNU-387, Huh7, and one normal liver line, THLE2, were treated with IL-22. RT-qPCR analysis was conducted to study the role of IL-22 in altering the expression levels of anti-apoptotic genes, MCL-1 and BCL-2, and metastatic genes, MMP-7 and MMP-9. A significant increase in expression levels of these genes was observed after IL-22 treatment. Furthermore, to explore the major pathways involved in IL-22-mediated upregulation of anti-apoptotic and metastatic genes, cells were treated with inhibitors of JAK/STAT and PI3K/AKT pathways along with IL-22. Resultantly, a significant decrease in expression levels of target genes was observed, indicating the involvement of JAK/STAT and PI3K/AKT signaling cascades in IL-22-mediated oncogenesis. Finally, Cell Scratch assay was performed to check the effect of IL-22 and inhibitors of JAK/STAT and PI3K/AKT on the metastatic potential of liver cells. While migration was observed in Huh7 and THLE2 cells treated with IL-22, no migration was observed in cells treated with IL-22 along with JAK/STAT and PI3K/AKT inhibitors. Results indicate that IL-22 encourages metastasis in HCC cells via the JAK/STAT and PI3K/AKT pathways. CONCLUSION: Results showed that IL-22 upregulates anti-apoptotic and metastatic genes in HCC through JAK/STAT and PI3K/AKT signaling pathways.

• Keywords
• Hepatocellular carcinoma, IL-22, JAK/STAT pathway, PI3K/AKT pathway, Proinflammatory cytokine,
• MeSH
• Phosphatidylinositol 3-Kinase metabolism   MeSH
• Phosphatidylinositol 3-Kinases metabolism   MeSH
• Carcinoma, Hepatocellular * metabolism   MeSH
• Interleukin-22 MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Liver Neoplasms * metabolism   MeSH
• Cell Proliferation genetics   MeSH
• Proto-Oncogene Proteins c-akt metabolism   MeSH
• Signal Transduction MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Phosphatidylinositol 3-Kinase MeSH
• Phosphatidylinositol 3-Kinases MeSH
• Proto-Oncogene Proteins c-akt MeSH