Experimental activation of peritoneal macrophages by interferon gamma (IFN-γ) resulted in the inhibition of Encephalitozoon cuniculi replication. However, E. cuniculi could replicate either in a non-activated cell line of murine macrophages PMJ2-R or in IFN-γ-activated PMJ2-R cells. Moreover, activation with IFN-γ led to faster replication of E. cuniculi in these cells. Opsonisation of E. cuniculi spores with anti-E. cuniculi polyclonal antibody did not affect E. cuniculi replication in both, non-activated and activated murine macrophages. In contrast, opsonisation of E. cuniculi spores caused the most effective replication of E. cuniculi in activated PMJ2-R cells. However, production of nitric oxide by these cells was significantly more intensive than that in non-activated, infected cells, where the parasite replicated to a much lesser extent. Our results support the hypothesis that E. cuniculi uses phagocytosis for the infection of host cells. They also indicate that the mechanism by which spores of E. cuniculi are killed by macrophages is not dependent on nitric oxide and they reveal that PMJ2-R cells cannot substitute peritoneal murine macrophages in immunological studies on E. cuniculi.
Monoclonal antibody B4 (mAb B4) was previously developed to the myxozoan parasite Tetracapsuloides bryosalmonae Canning, Curry, Feist, Longshaw et Okamura, 1999, the causative agent of proliferative kidney disease of salmonids. Here we describe the reaction of mAb B4 against Myxobolus cerebralis Hofer, 1903, the parasite that causes 'whirling disease' in salmonids. Tissues examined were collected from experimentally infected rainbow trout Oncorhynchus mykiss (Walbaum) and the aquatic oligochaete Tubifex tubifex (O.F. Müller), the two hosts involved in the life cycle of M. cerebralis. Paraffin sections of infected rainbow trout taken at 4 h and 3, 10, 17 and 54 days post-exposure to infective M. cerebralis actinospores were immunohistochemically stained with mAb B4. Longitudinal sections through infected T. tubifex sampled 120 days post-exposure to M. cerebralis myxospores were also examined using this method. The only phase of the M. cerebralis life cycle that expressed the mAb B4 antigen was during sporogenesis in the salmonid host. The immunohistochemical staining demonstrated that the antigen was released into the tissues surrounding the spore and sporogonic stages of the parasite. The localisation of the antigen was diffuse in the fish, suggesting that the possible effect of M. cerebralis infection is extensive through the head tissues and not limited to areas of cartilage destruction as previously thought.
Exposure of thylakoid membranes to high temperature in dark leads to the degradation of D1 protein. Maximum degradation of D1 protein occurred at 45 °C. Using N-terminal specific D1 antibody, a 23 kDa fragment of D1 protein was detected. The degradation of D1 protein could be prevented both by radical scavengers and inhibitors of serine protease and metallo-protease. These results suggest that degradation of D1 protein during exposure of thylakoid membranes to high temperature in dark is catalyzed by protease. and A. K. Singh, G. S. Singhal.