Characterization of Canine Peyer's Patches by Multidimensional Analysis: Insights from Immunofluorescence, Flow Cytometry, and Single-Cell RNA Sequencing.

The oral route is effective and convenient for vaccine administration to stimulate a protective immune response. GALT plays a crucial role in mucosal immune responses, with Peyer's patches (PPs) serving as the primary site of induction. A comprehensive understanding of the structures and functions of these structures is crucial for enhancing vaccination strategies and comprehending disease mechanisms; nonetheless, our current knowledge of these structures in dogs remains incomplete. We performed immunofluorescence and flow cytometry studies on canine PPs to identify cell populations and structures. We also performed single-cell RNA sequencing (scRNA-seq) to investigate the immune cell subpopulations present in PPs at steady state in dogs. We generated and validated an Ab specifically targeting canine M cells, which will be a valuable tool for elucidating Ag trafficking into the GALT of dogs. Our findings will pave the way for future studies of canine mucosal immune responses to oral vaccination and enteropathies. Moreover, they add to the growing body of knowledge in canine immunology, further expanding our understanding of the complex immune system of dogs.

Crosstalk between the Intestinal Virome and Other Components of the Microbiota, and Its Effect on Intestinal Mucosal Response and Diseases.

In recent years, there has been ample evidence illustrating the effect of microbiota on gut immunity, homeostasis, and disease. Most of these studies have engaged more efforts in understanding the role of the bacteriome in gut mucosal immunity and disease. However, studies on the virome and its influence on gut mucosal immunity and pathology are still at infancy owing to limited metagenomic tools. Nonetheless, the existing studies on the virome have largely been focused on the bacteriophages as these represent the main component of the virome with little information on endogenous retroviruses (ERVs) and eukaryotic viruses. In this review, we describe the gut virome, and its role in gut mucosal response and disease progression. We also explore the crosstalk between the virome and other microorganisms in the gut mucosa and elaborate on how these interactions shape the gut mucosal immunity going from bacteriophages through ERVs to eukaryotic viruses. Finally, we elucidate the potential contribution of this crosstalk in the pathogenesis of inflammatory bowel diseases and colon cancer.