Comparative analysis of SLA-1 and SLA-2 genetic diversity in exotic, hybrid, and local pig breeds of Cameroon in relation to adaptive immunity against African swine virus

Abstract

African swine fever is a severe hemorrhagic swine disease that greatly affects smallholder pig farm productivity in low-income countries as well as some developed countries. Research has shown that the indigenous pigs and wild suids in Africa are either tolerant or resistant to the disease. Also, resistance to disease and favourable production traits are attributed to polymorphism within the major histocompatibility complex (MHC), which is crucial for the vertebrate's adaptive immune response. The polymorphism within the swine leukocyte antigen (SLA) is attributable to host-pathogen co-evolution which results in improved resistance to disease as well as adaptation to diverse environments. While this makes the SLA essential for comparative diversity studies, comparative SLA studies are absent in this context. We undertook SLA-1 and SLA-2 exon-2 comparative genetic diversity study within the locally adapted (local) breed, hybrid (a cross between local and exotic), and the exotic breed of pigs in Cameroon using the polymerase chain reaction sequence-based typing method on 41 animals. Our data analyses provide evidence of positive balancing selection as well as conserved private alleles within the local breeds, the highest expected heterozygosity within the tolerant population while the exotic population had the highest number of haplotypes for both SLA-1 and SLA-2 . The results from this study contribute to our expanding knowledge of SLA genetic diversity while providing the first SLA data for the indigenous and exotic breeds of pigs in Cameroon.