Defects in host immune function in tree frogs with chronic chytridiomycosis

Young, Sam, Whitehorn, Paul, Berger, Lee, Skerratt, Lee F., Speare, Rick, Garland, Stephen, and Webb, Rebecca (2014) Defects in host immune function in tree frogs with chronic chytridiomycosis. PLoS ONE, 9 (9). e107284. pp. 1-16.

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Abstract

The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has caused mass mortality leading to population declines and extinctions in many frog species worldwide. The lack of host resistance may be due to fungal immunosuppressive effects that have been observed when Bd is incubated with cultured lymphocytes, but whether in vivo host immunosuppression occurs is unknown. We used a broad range of hematologic and protein electrophoresis biomarkers, along with various functional tests, to assess immune competence in common green (Litoria caerulea) and white-lipped (L. infrafrenata) tree frogs experimentally infected with Bd. Compared with uninfected frogs, Bd infection in L. caerulea caused a reduction in immunoglobulin and splenic lymphocyte responses to antigenic stimulation with sheep red blood cells, along with decreased white blood cell and serum protein concentrations, indicating possible impaired immune response capability of Bd-infected frogs. This is the first in vivo study suggesting that infection with Bd causes multiple defects in systemic host immune function, and this may contribute to disease development in susceptible host species. Although L. infrafrenata failed to maintain Bd infection after exposure, white blood cell and serum globulin concentrations were lower in recovered frogs compared with unexposed frogs, but antigen-specific serum and splenic antibody, and splenic cellular, responses were similar in both recovered and unexposed frogs. This may indicate potential systemic costs associated with infection clearance and/or redirection of host resources towards more effective mechanisms to overcome infection. No clear mechanism for resistance was identified in L. infrafrenata, suggesting that localized and/or innate immune defense mechanisms may be important factors involved in disease resistance in this species.

Item ID: 35383
Item Type: Article (Research - C1)
ISSN: 1932-6203
Keywords: chytridiomycosis, Batrochytrium dendrobatidis, Litoria caerulea, Litoria infrafrenata, immunity, pathogenesis
Funders: Australian Government, Department of Environment, Water, Heritage and the Arts, Australian Research Council (ARC)
Projects and Grants: Australian Government grant number 60776, ARC grant number FT100100375, ARC grant number LP110200240
Date Deposited: 15 Sep 2014 05:27
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0707 Veterinary Sciences > 070707 Veterinary Microbiology (excl Virology) @ 50%
11 MEDICAL AND HEALTH SCIENCES > 1117 Public Health and Health Services > 111799 Public Health and Health Services not elsewhere classified @ 50%
SEO Codes: 92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920499 Public Health (excl. Specific Population Health) not elsewhere classified @ 50%
92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920108 Immune System and Allergy @ 50%
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