Abstract

Morbillivirus is a genus in the family Paramyxoviridae that cause devastating disease in both animal and human populations. Viruses in this genus include measles virus, canine distemper virus, rinderpest virus, peste des petits ruminants virus, phocine distemper virus, and dolphin morbillivirus (DMV). While significant mortality events caused by DMV have been documented in the Atlantic, they have not been identified in the Pacific.

Host genetic predisposition plays a central role in disease. Morbilliviruses gain entry into susceptible hosts via the B-cell receptor signaling lymphocyte activation molecule (SLAM). In humans, single nucleotide polymorphisms (SNPs) in SLAM decrease the immune response to measles vaccination in individuals. It is thought that specific SNPs in SLAM make the receptor unsuitable for binding of the H protein. Therefore, understanding dolphin SLAM sequence variability may help in determining the risk for DMV infection in different populations as well as vaccine efficacy potential.

Total RNA was extracted from buffy coats of 32 Atlantic bottlenose dolphins, 1 Pacific bottlenose dolphin, and 2 Atlantic/Pacific hybrids. Primers were designed based on the bottlenose dolphin genome, and the RT-PCR products were sequenced and analyzed. No differences in nucleotide sequence in any of the bottlenose dolphin SLAM receptors were identified. This indicates that all individuals in this study are equally susceptible to viral binding to the SLAM receptor, and vaccination for morbillivirus should not be complicated by host receptor SNPs. While the individuals in this study with Pacific lineage showed complete homology to the Atlantic population's SLAM receptor, a larger sample size of the Pacific population is needed to better assess differences. We did find alternative splicing of the SLAM receptor. Further assessment of isoform variability among individuals from Atlantic and Pacific populations is needed to confirm that SLAM variability is not a factor in the differing DMV epidemiology in Atlantic and Pacific bottlenose dolphins.

Acknowledgements

This work was funded by ONR research grant N° N00014-06-1-0250. All protocols were approved by the University of Florida Institutional Animal Care and Use Committee (IACUC# C233). We would like to thank Kevin Carlin (USNMMP) for assistance with sample collection and Jennifer Burchell and Celeste Benham for laboratory assistance.