Toxoplasma gondii is an obligate intracellular protozoan parasite responsible for a common infection of the central nervous system. Interferon (IFN) γ is the key cytokine of host defence against T. gondii. However, T. gondii strains differ in virulence and T. gondii factors determining virulence are still poorly understood. In astrocytes IFN γ primarily induces immunity-related GTPases (IRGs), ...

The cDNA expression array technique is a powerful tool to determine, at one time from many genes, specific gene messages modulated by infection. In the present study, we identified genes modulated in response to virulent versus avirulent Legionella pneumophila infection of the alveolar macrophage cell line MH-S by the cDNA expression array technique. Many macrophage genes were found to be modul...

Rhodococcus equi is an intracellular pathogen of macrophages that causes rhodococcal pneumonia in foals and immunocompromised people. Evidence exists that neutrophils play a vital role in resistance to infection with R. equi; however, the means by which neutrophils exert their effects have not been clearly defined. In addition to directly killing bacteria, neutrophils also may exert a protectiv...

The direct F.A. Method has been used for diffe­rentiation of virulent and avirulent lines of influenza viruses. A positive fluorescence was obtained indi­cating the level of virus in the tissues, sorbing with dried mouse powder helped to reduce non-specific staining. The virulent line showed the greatest num­ber of fluorescent cells with the peak at 10 hours. the non-virulent lines showed a gra...

Type I interferons (IFNs) are essential components of the innate immune system. This study characterized the distinct IFN sensitivities of two closely related Semliki Forest virus (SFV) strains in cell culture. The virulent L10 strain was derived from the original virus isolate by propagation in mice. In contrast, the avirulent SFV strain, designated V42, was derived from an earlier passage of ...

We investigated the susceptibility of virulent and avirulent strains of Haemophilus ducreyi to the bactericidal activity of normal human serum and to phagocytosis and killing by human polymorphonuclear leukocytes (PMNL). Strains were defined as virulent if intradermal inoculation into a rabbit produced a typical necrotic lesion. Nonvirulent strains produced no cutaneous lesions in rabbits. Viru...

Macrophages from the mouse peritoneal cavity were examined by electron microscopy at various time intervals up to 24 h after intraperitoneal administration of each of three strains of staphylococci different in virulence for mice: high-virulent, low-virulent, and avirulent strains. After engulfment, avirulent bacteria were highly liable to intracellular digestion, resulting in almost complete d...

Although ethylene regulates a wide range of defense-related genes, its role in plant defense varies greatly among different plant-microbe interactions. We compared ethylene's role in plant response to virulent and avirulent strains of Xanthomonas campestris pv. vesicatoria in tomato (Lycopersicon esculentum Mill.). The ethylene-insensitive Never ripe (Nr) mutant displays increased tolerance to ...

Many pathogenic and non-pathogenic fungi possess the ability to alter their morphology. The major fungal pathogens can grow vegetatively in multiple morphologies, including yeast, pseudohyphae, and hyphae. Yeast are typically round or oval-shaped single cells, while the filamentous morphologies, pseudohyphae and hyphae, are comprised of elongated cells attached end to end. Pseudohyphae are elli...

Serum from normal mammals agglutinated and immobilized nonpathogenic Leptospira biflexa and agglutinated avirulent lines of pathogenic serotypes L. icterohaemorrhagiae and L. zanoni. Virulent lines of L. icterohaemorrhagiae and L. zanoni were not affected, nor were any of three strains of L. pomona, one of which was avirulent. The active principle in serum was a beta-macroglobulin which was hea...