Subramaniam (Sri) Srikumaran
Rocky Crate D.V.M. and Wild Sheep Foundation Endowed Chair in Wild Sheep
Education & Training
BVSc: University of Ceylon
MS: University of Maryland
PhD: University of Maryland
Post-doctoral: Amherst College, Massachusetts
Sabbatical: University of Oxford, U.K.
My research program is focused on diseases of wild sheep in general, and
pneumonia in particular. The current focus is on understanding the
pathogenesis of pneumonia caused by Mannheimia and Pasteurella
species. Leukotoxin is the most important virulence factor of these
organisms, and is cytolytic to all subsets of leukocytes. Research in my
laboratory during the past few years has identified CD18, the β subunit of
β2-integrins, as the receptor for leukotoxin on the leukocytes of bighorn
sheep, domestic sheep, and cattle. More recent studies have mapped the
leukotoxin binding site on the CD18 molecule.
Current research projects on leukotoxin and its receptor include
Identification of CD18 peptide analogs that inhibit leukotoxin binding
Elucidation of the role of the α subunits of β2-integrins in leukotoxin
binding of CD18;
Analysis of the role of inflammatory cytokines IL-1-β and TNF-α in the
expression of leukotoxin receptor, and pathogenesis of pneumonia.
Bighorn sheep are much more susceptible than domestic sheep to pneumonia
Mannheimia and Pasteurella species. Polymorphonuclear
leukocytes (PMNs) of bighorn sheep are 8-16 fold more susceptible to
leukotoxin than those of domestic sheep. Our working hypothesis is that
bighorn sheep are more susceptible than domestic sheep to pneumonia because
their PMNs are more susceptible to leukotoxin than those of domestic sheep.
One facet of our research examines the molecular basis for the enhanced
susceptibility of bighorn sheep PMNs. Another facet examines the role of
other virulence factors in the pathogenesis of pneumonia. Yet another facet
of our research examines the possible role of viral infections in pneumonia
of bighorn sheep. The long term goal of my laboratory is to develop control
measures against pneumonia which has decimated bighorn sheep populations
time and time again in the past.