A complete genome of one of several species of elephant endotheliotropic herpesviruses (EEHV), associated with a deadly disease that strikes both managed and free ranging elephants, has now been sequenced by a team of researchers from Baylor College of Medicine and Johns Hopkins School of Medicine.
The finding, which appears in the online journal Genome Announcements, suggests that this particular virus is so unique it could warrant establishment of a new herpesvirus subfamily category.
"Within elephant endotheliotropic herpesvirus, EEVH1A has been found to be the most prevalent when it comes to the hemorrhagic disease found in Asian elephants, which is why we focused on this subspecies," said Dr. Paul Ling, associate professor of molecular virology and microbiology at BCM.
Ling and his team of researchers in molecular virology and microbiology and the Human Genome Sequencing Center at BCM, along with Dr. Gary S. Hayward’s team in the Viral Oncology Program at Johns Hopkins School of Medicine, were able to use a 12- year-old DNA sample to assemble the sequence.
While other species of EEHV have been partially characterized, the completed genome sequence of EEHV1A revealed that there are many genes unique to the EEHVs.
"All herpes viruses have certain core regions that are similar in terms of what they do, but with EEHV1A, we identified 60 genes that (appear to be unique relative to) not present in other herpesviruses," said Ling. "At this time, we think a new subfamily, in addition to the three subfamilies which categorize the 8 herpesviruses that infect humans, might be needed as we continue to learn more about this virus."
EEHV affects both Asian and African elephants but is most often fatal in Asian elephants. First identified in 1995, it wasn’t until 2010 that a real-time PCR test was developed through a collaboration between BCM and the Houston Zoo. The test diagnoses the virus before elephants begin showing symptoms. Once symptoms are seen it is usually too late to save the animal.
In addition to the PCR test, the complete sequence gives researchers another tool to develop better procedures to evaluate immune responses to potential vaccines, Ling said. It will also help researchers understand why some juvenile elephants become sick from the disease and some don’t.
Others who took part the genome sequencing include Dr. Jeffery Reid, Dr. Xiang Qin, Dr. Richard Gibbs (director of the HGSC), Dr. Joseph Petrosino, instructor Donna M. Muzny, research technician Rongsheng Peng, all with the Human Genome Sequencing Center at BCM; Jian-Chao Zong and Sarah Y. Heaggans both with the Viral Oncology Program at JHS.
This study was funded by a research grant from the Houston Zoo, Inc. and research grant AI24576 from the National Institutes of Health.