Role of interferon-γ and nitric oxide in the neuropathogenesis of avirulent Semliki Forest virus infection

• Published in: Neuropathology and applied neurobiology Vol. 29; no. 6; pp. 553 - 562
• Main Authors: Keogh, B., Atkins, G. J., Mills, K. H. G., Sheahan, B. J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.12.2003; Blackwell Science
• Subjects: Alphavirus Infections - immunology; Alphavirus Infections - metabolism; Alphavirus Infections - pathology; Animals; Antigens, Viral - immunology; Antigens, Viral - metabolism; B cell; Biological and medical sciences; Brain - metabolism; Brain - pathology; Brain - virology; cytokine; Demyelinating Diseases - immunology; Demyelinating Diseases - virology; Disease Models, Animal; Enzyme-Linked Immunosorbent Assay; Experimental viral diseases and models; Immunohistochemistry; Infectious diseases; Interferon gamma Receptor; Interferon-gamma - metabolism; interferon-γ; macrophage; Macrophages - immunology; Medical sciences; Mice; Mice, Knockout; Necrosis; Neurons - pathology; Neurons - virology; nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase - deficiency; Nitric Oxide Synthase Type II; Receptors, Interferon - deficiency; Semliki Forest virus; Semliki forest virus - immunology; Semliki forest virus - metabolism; T cell; Th1 Cells - immunology; Viral diseases; Immunohistochemistry; Semliki forest virus; interferon-γ; Encephalomyelitis; Togaviridae; B cell; Arbovirus disease; Semliki forest disease; Nervous system diseases; T cell; Cytokine; Rodentia; macrophage; Cerebral disorder; Infection; Virus; Anatomic pathology; Vertebrata; Experimental disease; Mammalia; Mouse; Animal; Nitric oxide; Viral disease; Central nervous system disease; Alphavirus; Spinal cord disease; Gamma interferon
• ISSN: 0305-1846; 1365-2990
• DOI: 10.1046/j.1365-2990.2003.00492.x

Semliki Forest virus (SFV) infection of mice provides a useful model for the analysis of viral neuropathogenesis. In this study, the roles of interferon (IFN)‐γ and nitric oxide (NO) in the pathogenesis of SFV infection were assessed using mice deficient in inducible nitric oxide synthase (iNOS–/–), an enzyme important in the production of NO, and mice deficient in IFN‐γ receptor (IFN‐γR–/–). Gene‐knockout and wildtype mice were infected intranasally with the avirulent A7 strain of SFV and neuropathological lesions were correlated with levels of IFN‐γ, tumour necrosis factor (TNF)‐α and interleukin (IL)‐10 in the olfactory bulbs and frontal cortex. Lesions in IFN‐γR–/– mice were characterized by higher levels of neuronal necrosis than in wildtype mice. The higher levels of neuronal necrosis were associated with increased levels of SFV antigen in neurones and increased numbers of macrophages and B cells. Relative differences in the severity of demyelination between IFN‐γR–/– and wildtype mice were not detected. Similar levels of neuronal necrosis and SFV antigen labelling occurred in iNOS–/– mice and wildtype mice and levels of demyelination and macrophage infiltration in the iNOS–/– mice were lower than those in the wildtype strain. A rapid, but transient increase in the concentration of IFN‐γ was demonstrated in the frontal cortex of all infected mice samples. IL‐10 levels in the frontal cortex and olfactory bulbs of SFV‐infected iNOS–/– mice exceeded those present in the wildtype mice. This study, taken with our previous reports, provides further evidence that type 1 T cell responses are important in the control of brain viral clearance and the prevention of neuronal necrosis, but not in the development of demyelination.