Genetic diversity comparison of the DQA gene in European rabbit (Oryctolagus cuniculus) populations

Identification and characterization of a rabbit novel IFN-α unlocated in genome

The multigene family of rabbit IFN-α (RbIFN-α) is located on chromosome 1, which shows seven functional genes in type I IFN locus. A novel RbIFN-α that remains unlocated in the rabbit genome was amplified and designated as the first novel rabbit IFN-α (RbIFN-αNov1), which possesses the typical molecular characteristics of type I IFNs and could be induced in RK-13 cells and peripheral blood mononuclear cells. After the mature peptide of RbIFN-αNov1 was expressed, its antiviral activity, physicochemical characteristics, and cytotoxicity were determined in vitro. Results indicated that RbIFN-αNov1 exerted a high specific antiviral activity against VSV and a low cytotoxic effect on RK-13 cells. RbIFN-αNov1 showed high sensitivity to trypsin and remained relatively stable after acid, alkali, or heat treatment. RbIFN-αNov1 could induce Mx1 expression on RK-13 cells and activate the NF-κB, ISRE and BoIFN-β promoter activities on bovine testicular cells. Overall, our research on RbIFN-αNov1 not only enriches the knowledge about rabbit IFNs but also makes RbIFN-αNov1 have the potential to be used as an effective therapeutic agent for rabbit viral diseases.

Evolutionary study of leporid CD4 reveals a hotspot of genetic variability within the D2 domain

CD4 is the major receptor on T helper cells involved in the uptake of human immunodeficiency virus (HIV) or simian immunodeficiency virus (SIV) into their host cells. Evolutionary studies of CD4 in primates revealed signatures of positive selection in the D1 domain that interacts with primate exogenous lentivirus gp120 proteins. Here, we studied the evolution of CD4 in lagomorphs by comparing sequences obtained for the genera Oryctolagus, Sylvilagus, Lepus, and Ochotona. Our results reveal an overall higher divergence in lagomorphs compared to primates with highest divergence in the D2 domain. A detailed analysis of a small fragment of 33 nucleotides coding for amino acids 169 to 179 in the D2 domain showed dramatic amino acid alterations with a dN/dS value of 3.2 for lagomorphs, suggesting that CD4 is under strong positive selection in this particular region. Within each leporid genus, no significant amino acid changes were observed for the D2 domain which indicates that the genetic differentiation occurred in the ancestor of each genus before the species radiation. The rabbit endogenous lentivirus type K (RELIK) found in leporids shares high structural similarity with HIV which suggests a possible interaction between RELIK and CD4. The presence of RELIK in the studied leporids, the high structural similarity to modern-day exogenous lentiviruses and the absence of exogenous lentiviruses in leporids, allows us to hypothesize that this endogenous retrovirus, that was most probably exogenous in the past, drove the divergent evolution of leporid CD4.

An overview of the lagomorph immune system and its genetic diversity

Our knowledge of the lagomorph immune system remains largely based upon studies of the European rabbit (Oryctolagus cuniculus), a major model for studies of immunology. Two important and devastating viral diseases, rabbit hemorrhagic disease and myxomatosis, are affecting European rabbit populations. In this context, we discuss the genetic diversity of the European rabbit immune system and extend to available information about other lagomorphs. Regarding innate immunity, we review the most recent advances in identifying interleukins, chemokines and chemokine receptors, Toll-like receptors, antiviral proteins (RIG-I and Trim5), and the genes encoding fucosyltransferases that are utilized by rabbit hemorrhagic disease virus as a portal for invading host respiratory and gut epithelial cells. Evolutionary studies showed that several genes of innate immunity are evolving by strong natural selection. Studies of the leporid CCR5 gene revealed a very dramatic change unique in mammals at the second extracellular loop of CCR5 resulting from a gene conversion event with the paralogous CCR2. For the adaptive immune system, we review genetic diversity at the loci encoding antibody variable and constant regions, the major histocompatibility complex (RLA) and T cells. Studies of IGHV and IGKC genes expressed in leporids are two of the few examples of trans-species polymorphism observed outside of the major histocompatibility complex. In addition, we review some endogenous viruses of lagomorph genomes, the importance of the European rabbit as a model for human disease studies, and the anticipated role of next-generation sequencing in extending knowledge of lagomorph immune systems and their evolution.