International Journal of Molecular Veterinary Research, 2025, Vol.15, No.1, 1-12 http://animalscipublisher.com/index.php/ijmvr 8 quickly evolving since they are at play in host-pathogen interactions (Sironi et al,. 2015; Sackton, 2019). For instance, the analysis of waterfowl immune systems unveiled genes involved in innate immunity and pathogen recognition and inhibition, such as toll-like receptors and antimicrobial peptides, to often be under positive selection, indicating that they have been significant during past resistance to pathogens (Jax et al., 2022). Similarly, evolutionary history of mammalian immune genes highlights the role of ancient infection in shaping genetic diversity and immune response (Sironi et al., 2015). 8.2 Modern threats: rabies, distemper, and zoonotic diseases New canids are also severely susceptible to rabies, distemper, and other zoonoses. Their quick immune gene evolution to the pathogens has been documented in various scientific studies. In one such study, for example, genomic analysis of the dolphin epidemic as a result of a morbillivirus outbreak isolated several candidate immunity-involving genes indicating the significance of genetic diversity in resisting viral invasion (Batley et al., 2021). In addition, studies on zoonotic pathogens like Bordetella hinzii in immunocompromised animals have shown how pathogens can rapidly adapt to novel hosts and the fluidity of host-pathogen dynamics (Launay et al., 2021). Bat comparative genomes have also revealed special immune adaptations that may be the cause of their reservoir status of zoonotic viruses and illuminated possible mechanisms for pathogen resistance among canids (Tian et al., 2023). 8.3 Potential for genomic monitoring of pathogen resistance The future for genomic monitoring of canid pathogen resistance is bright with the evolution of genomic technology. Whole genome sequencing and comparative genomics can exhibit genetic variation associated with immune response, facilitating surveillance of pathogen resistance through time (Batley et al., 2021). For instance, genomic patterns of immune genes can be employed to track resistance evolution to certain pathogens, as also seen in insect immune genes where fast evolution and positive selection are the rule (Sackton, 2019; Ngo et al., 2022). Moreover, the integration of population genetics and systems immunology can better establish determinants of variation in the immune response such that the conservation strategy can be adapted (Quintana-Murci, 2019). 9 Case Study: Evolution of the Major Histocompatibility Complex (MHC) in Canids 9.1 Overview of the MHC and its role in immune response Major Histocompatibility Complex (MHC) is one of the main components of the vertebrate immune system, with a focus on presenting peptide antigens to T-cells and triggering an adaptive immune response. MHC genes are some of the most polymorphic in the vertebrate genome, with extensive allelic diversity required to be able to recognize a wide variety of pathogens (Kaufman, 2018; Radwan et al., 2020; Abualrous et al., 2021). This polymorphism is maintained by balancing selection pressures such as heterozygote advantage and frequency-dependent selection, which depend on pathogen-mediated forces (Hedrick, 1994; Sommer, 2005; Dearborn et al., 2022). MHC is divided into class I and class II genes, with different roles in immune function. Class I MHC molecules present intracellular antigens, typically viruses, to CD8+ T cells, while class II MHC molecules present extracellular antigens to CD4+ T cells (Kaufman, 2018; Abualrous et al., 2021) (Figure 4). 9.2 Comparative analysis of MHC genes in wolves, coyotes, and dogs Comparative genomic studies have given good insights into the evolution and diversity of MHC genes in canids like wolves (Canis lupus), coyotes (Canis latrans), and domestic dogs (Canis familiaris). These studies have demonstrated that MHC genes in these canids have high polymorphism and are subjected to strong positive selection pressures (Kelley et al., 2004; Lapalombella, 2016; Bartocillo et al., 2021). For instance, research on Italian wolves has reported extensive genetic polymorphism of MHC class II genes that are critical for their survival and fitness to different environments (Lapalombella, 2016). Similarly, research on raccoon dogs, a non-model canid, has reported high allelic polymorphism of MHC class I genes with proof of long-term balancing selection and pathogen-mediated positive selection (Bartocillo et al., 2021). These findings emphasize the importance of MHC polymorphism to provide immune competence and versatility in natural populations.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==