Boyd Professor and Head

Contact Information:
Email: docall@lsuhsc.edu
Office Phone: 318-675-5750
Laboratory Phone: 318-675-5759
Office Fax: 318-675-5764

Education/Training:
Postdoctoral Study, University of Alberta Medical Center
Ph.D., 1968, University of Mississippi Medical Center
B.S., 1962, Biology and Chemistry, Loyola University - New Orleans

Major Research Interests: Herpesvirus Gene Regulation, Persistent Infection, and Pathogenesis

Herpesvirus infection usually results in cell death and production of virus, but may result in persistent infection. Using equine herpesvirus as a model, we seek to identify which of the 80 viral genes and proteins play a role in gene regulation and in mediating herpesvirus persistent infection and the molecular mechanisms involved. Using technologies of recombinant DNA, gene cloning, in vitro translation, DNA microarrays, DNA sequencing, site-specific mutagenesis, PCR, trans-activation assays and expression vector technology, we are determining the functions of the regulatory genes of both the viral genome and the genome of defective interfering particles (DIP) that mediate persistent infection. Since the DIP genome lacks most viral genes and contains hybrid forms of regulatory genes, elucidation of the alterations in viral gene regulation may reveal the molecular events required for persistent infection.  Other studies seek to elucidate the role of viral-encoded microRNAs in the viral gene program and possibly in herpesvirus latency.

Representative Publications:

Buczynski, K., S.K. Kim, and D.J. O’Callaghan. 2005. Initial characterization of 17 viruses harboring mutant forms of the immediate-early gene of equine herpesvirus 1 Virus Genes 31: 229-239.

Ebner, P.D. and D.J. O’Callaghan. 2006. Genetic complexity of EHV-1 DI particles and identification of novel EICP22/EICP27 hybrid proteins produced during persistent infection.  Virus Genes 32:313-320.

Kim, S.K., C.B. Ahn, R.A. Albrecht, and D.J. O'Callaghan. 2006. The unique IR2 protein of equine herpesvirus 1 (EHV-1) negatively regulates EHV-1 gene expression. J. Virol.  80: 5041-5049.

von Einem, J. P.M. Smith, G. R. Van de Walle, D.J. O’Callaghan, and N. Osterrieder.   2007. In vitro and In vivo characterization of equine herpesvirus 1 (EHV-1) mutants devoid of the viral chemokine-binding glycoprotein G (gG).  Virology 362: 151-162.

Ahn, B.C., J. E. Breitenbach, S. K. Kim, and D.J. O’Callaghan.  2007. The equine herpesvirus-1 IR3 gene that lies antisense to the sole immediate-early (IE) gene is trans-activated by the IE protein, and is poorly expressed to a protein.  Virology 363: 15-25.

Van de Walle, G.R. S T. Peters, B C. VanderVen, D.J. O'Callaghan, and N. Osterrieder.  2008. Equine herpesvirus 1 entry via endocytosis is facilitated by V integrins and an RSD motif in glycoprotein D. J. Virol. 82: 11859-11868.

O’Callaghan, D.J. and N. Osterrieder.  2008.  Herpesviruses of horses.  Encyclopedia of Virology. 3rd.  B. Mahy and M. Van Regenmortel (ed.) Elsevier Publishing Co., Oxford, UK.  Vol. 2.  411-420.

Ebner, P.D., S.K. Kim, and D.J. O’Callaghan. 2008.  Biological and genotypic properties of defective interfering particles of equine Herpesvirus 1 that mediate persistent infection.  .Virology 381: 98-105.

Breitenbach, J.E., P.D. Ebner, and D.J. O’Callaghan.  2009.  The IR4 auxiliary regulatory protein expands the in vitro host range of equine herpesvirus 1 and is essential for pathogenesis in the murine model.  Virology 383: 188-194.

Ahn, B. C., Y. Zhang, and D. J. O’Callaghan. 2010.  The equine herpesvirus-1 (EHV-1) IR3 transcript downregulates expression of the IE gene and the absence of IR3 gene expression alters EHV-1 biological properties and virulence.  Virology in press