Dr. Dickerson studies the immune response of bony fishes (teleosts) to the common protozoan parasite Ichthyophthirius multifiliis. This virulent ciliate is well known among aquaculturists as the etiological agent of “white spot”, a disease that afflicts a wide range of freshwater fishes. While I. multifiliis is highly pathogenic, animals exposed to controlled infections develop a strong acquired resistance to the parasite. I. multifiliis and channel catfish provide a good host-parasite experimental system for research on the mechanisms of mucosal immunity. Ichthyophthirius is confined to the epidermal layers of the skin and gills, and therefore can be visualized by light microscopy from the time it invades the host until the time it exits. It provides a unique system for the in vivo study of host-parasite interactions. Studies in the Dickerson laboratory suggest that acquired protection of the host following exposure to the parasite involves a novel mechanism of humoral immunity affecting parasite behavior. Rather than being killed, parasites are forced to exit fish prematurely in response to antibody binding. The target antigens involved in this response are a class of highly abundant glycosylphosphatidly-inositol (GPI)-anchored coat proteins referred to as immobilization antigens (i-antigens). Antibodies against surface i-antigens have been used to serotype isolates of the parasite, which in turn has contributed to new knowledge regarding the epizootiology of disease outbreaks and virulence between and among isolates. Dr. Dickerson’s laboratory utilizes molecular genetic and biological approaches to study the expression and function of genes relevant to infection and immunity of I. multifiliis. His laboratory also investigates the mechanisms of teleost B cell induction and antibody production at mucosal surfaces. His laboratory has been funded since 1987 through grants from the USDA National Research Competitive Grants Program, NIH, NSF, and private contracts.
- Swennes, A. G., Noe, J. G., Findly, R. C. and Dickerson, H. W. 2006. Differences in virulence between two serotypes of Ichthyophthirius multifiliis. Diseases of Aquatic Organisms, 69(2-3):227-32.
- Maki, J. L. and Dickerson, H. W. 2003. Systemic and cutaneous mucus antibody responses of channel catfish immunized against the protozoan parasite Ichthyophthirius multifiliis. Clinical and Diagnostic Laboratory Immunology, 10(5):876-81.
- Everett, K. D.and Dickerson, H. W. 2003. Ichthyophthirius multifiliis and Tetrahymena thermophila tolerate glyphosate but not a commercial herbicidal formulation. Bulletin of Environmental Contamination and Toxicology, 70(4):731-8.
- Wang, X., Clark, T. G., Noe, J. and Dickerson, H. W. 2002. Immunisation of channel catfish, Ictalurus punctatus, with Ichthyophthirius multifiliis immobilisation antigens elicits serotype-specific protection. Fish and Shellfish Immunology, 3(5):337-50.
- Wang, X. and Dickerson, H. W. 2002. Surface immobilization antigen of the parasitic ciliate Ichthyophthirius multifiliis elicits protective immunity in channel catfish (Ictalurus punctatus). Clinical and Diagnostic Laboratory Immunology, 9(1):176-81.
- Everett, K. D., Knight, J. R. and Dickerson, H. W. 2002. Comparing tolerance of Ichthyophthirius multifiliis and Tetrahymena thermophila for new cryopreservation methods. Journal of Parasitology, 88(1):41-6.
- Maki, J. L., Brown, C. C. and Dickerson, H. W. 2001. Occurrence of Ichthyophthirius multifiliis within the peritoneal cavities of infected channel catfish Ictalurus punctatus. Diseases of Aquatic Organisms, 44(1):41-5.