Chemotactic response of fish macrophages to Legionella pneumophila: correlation with pathogenicity

Abstract

Chemotaxis is the directional migration of cells in response to a chemical stimulus. This phenomenon appears to be responsible for the accun~ulation of macrophages during inflammation This work represents an attempt to understand certain aspects of host-parasite relationships in Legionnaire's Disease. In the first phase of this study, we measured the chemotactic stimulation of fish macrophages by 2 strains of Legionella pneumophila, one virulent and one avirulent for guinea pigs. Results from this part of the study, coupled with the possibility that reduced chemotaxis may b e a factor contributing to increased virulence, led us to initiate the second phase of this work to determine the correlation between in vitro chemotaxis and the degree of virulence of L. pneumophila for spot Leiostonius xanthurus. These studies demonstrated that virulent cells did not attract n~acrophages to the extent that avirulent cells did. The percentage of macrophages migrating toward virulent Legionella at 90 min was 24 as compared to 61 for the avirulent strain. In vivo studies showed that intraperitoneal injection of 1 to 2 X 10'' viable cells of vlrulent L. pneumophjla killed 100 ":, of the fish within 2 d whereas the same number of avirulent L pneumophila resulted in death in only 58 '10 of the fish within 2 d after injection.

The macrophage chemotactic activity of Streptococcus agalactiae and Streptococcus iniae extracellular products (ECP)

“…The final volume was 200 mL À1 compartment. The chambers were incubated on a horizontal platform shaker (100 revolutions min À1 ) for 90 min at 25 C. Following incubation, the filters were removed, inverted, placed on precleaned slide, attached with clear fingernail polish, and stained with Leukostat [8]. Enumeration of migrating cells per field of view was done in five fields on the bottom surface of the filters using a light microscope at 400 Â magnification.…”

Use of Cell Cultures to Study the Interactions of Ciliates with Fish

“…This has been demonstrated with several species of Tetrahymena and several human pathogens, including Campylobacter jejuni, Salmonella enterica, and Legionella pneumophila. None of these would be considered fish pathogens, although L. pneumophila is found in freshwater and can kill fish in the laboratory [61]. However, the mechanisms by which the ciliates act likely apply to fish pathogens as well.…”

The macrophage chemotactic activity of Edwardsiella tarda extracellular products

“…Macrophages are crucial to inflammatory reactions and other immune responses through their ability to function in effector, helper and suppressor capacities (Nash, Fletcher & Thomson 1986; Zelikoff, Enanf, Bowser, Squibb & Frenkel 1991). The migration of macrophages from the blood and adjacent tissues to the site of microbial infiltration or injury is a critical initial step in the inflammatory process (Griffin 1984; Weeks, Sommer & Dalton 1988; Weeks‐Perkins & Ellis 1995; Klesius & Sealey 1996; Ellis 2001). The movement of macrophages and other leucocytes may involve chemotactic and chemokinetic mechanisms.…”