The University of Georgia College of Veterinary Medicine

Georgia Veterinary Scholar Program

Georgia Veterinary Scholar	Faculty Mentor

Matthew Miller University of Georgia Class of 2003	Dr. Harry Dickerson

Schlieren Optic Analysis of Ichthyophthirius multifiliis Swimming Behavior in the Presence of Antigen-specific murine MAb.

Because of its ability to infect and kill virtually all naïve fish, the ciliate, Ichthyophthirius multifiliis, is considered to be one of the most economically important protozoan pathogens of fish. Based on previous experimental evidence, it is hypothesized that sub-immobilizing levels of antibody induce I. multifiliis to leave the epithelium of an immune host. To investigate this phenomenon further, we measured the change of behavior of I. multifiliis (serotype G5) in vitro when exposed to sub-immobilizing levels of mouse monoclonal antibody G3-61 (IgG1). This mAb reacts with the major surface protein (i-antigen) of the parasite and provides protection following passive transfer into naïve fish. After exposing I. multifiliis to varying dilutions of mAb G3-61, we determined that the minimum amount of antibody required to completely immobilize the parasite in vitro was 3.64 x 10-5 ug/mL. Sub-immobilizing amounts of mAb G3-61 were added to a 100 mL tank containing approximately 1000 I. multifiliis theronts. Filming was accomplished using a modified Schlieren optical pathway, illuminated with a monochromatic light source (HeNe laser) to achieve extremely high contrast in conjunction with great depth of field. Two cameras were mounted at right angles to each other to provide the three-dimensional coordinates for all objects in view. A Motion Analysis computer was then used to plot the coordinates of the parasites during specified periods of time. We found that the G5 serotype of I. multifiliis had a significant change in motion when exposed to sub-immobilizing amounts of mAb G3-61. This behavioral change was not detected when parasites were exposed to the control mAb 10H3 (IgG1) that reacts with a heterologous immobilization serotype of I. multifiliis. These results support a model of antibody-mediated immunity in which parasites are induced to leave the host in response to binding by antibody against i-antigen, and WitnessTM FeLV, WitnessTM FIV, ViraCHEKR FIV, and ViraCHEKR FeLV from Synbiotics Europe. Sensitivity, specificity, and positive and negative predictive values of each test will be calculated by comparing test results to Western immunoblot assay results for FIV and virus isolation and immunofluorescence assay results for FeLV.