Functional variation at an expressed MHC class II β locus associates with Ranavirus infection intensity in larval anuran populations

AbstractInfectious diseases are causing catastrophic losses to global biodiversity. Iridoviruses in the genusRanavirus are among the leading causes of amphibian disease-related mortality. Polymorphisms in major histocompatibility complex (MHC) genes are significantly associated with variation in amphibian pathogen susceptibility. MHC genes encode two classes of polymorphic cell-surface molecules that can recognize and bind to diverse pathogen peptides. While MHC class I genes are the classic mediators of viral-acquired immunity, larval amphibians do not express them. Consequently, MHC class II gene diversity may be an important predictor ofRanavirus susceptibility in larval amphibians, the life stage most susceptible toRanavirus. We surveyed natural populations of larval wood frogs (Rana sylvatica), which are highly susceptible toRanavirus, across 17 ponds and 2  years in Maryland, USA. We sequenced the peptide-binding region of an expressed MHC class IIβ locus and assessed allelic and genetic diversity. We converted alleles to functional supertypes and determined if supertypes or alleles influenced host responses toRanavirus. Among 381 sampled individuals, 26% were infected withRanavirus. We recovered 20 unique MHC class II β alleles that fell into two deeply diverged clades and seven supertypes. MHC genotypes were associated withRanavirus infection intensity, but not prevalence. Specifically, MHC heterozygotes and supertype ST1/ST7 had significantly lowerRanavirus infect...

Source: Immunogenetics - February 13, 2019 Category: Genetics & Stem Cells Source Type: research