Induction of Nitric Oxide (NO) during acute infectious bursal disease virus (IBDV) infection in chickens

Bhawna Poonia and S. Charan
Department of Veterinary Microbiology
CCS Haryana Agricultural University, Hisar - 125004 (Haryana)

Nitric oxide (NO) is synthesized from the substrate L-arginine by the enzymatic reaction of the NO synthases (NOS). As a signal molecule, it exhibits an enormous range of physiologically important functions in the host viz. anti-microbial (against viruses, intracellular bacteria, parasites), immuno-regulatory (a multi-functional mediator in immune defenses as a cytotoxic effecter molecule of the non-specific immune response) and has been implicated in the control of cancers, as neurotransmitter as well as vasodilator regulating the vascular permeability. Infectious bursal disease virus (IBDV) infection is an important disease of young chickens characterized by hemorrhage in thigh, pectoral muscle and bursa of fabricius. The exact mechanism of clinical disease is not clearly established as some birds with a fewer lesions can be found dead, while others despite extensive hemorrhages can survive. Recently, investigators have focused on the importance of NO in viral infections and it has been observed that during IBDV infection there is transient but significantly increased induction of NO.

In the present study, the levels of NO in the supernatants of phytohaemagglutinin (PHA) stimulated lymphocyte cultures from T-cell suppressed (treated with cyclosporin-A) and immune competent chickens were monitored in the experimentally infected birds. It was observed that PHA stimulated peripheral blood mononuclear cells from the immune competent chickens showed significantly increased levels of NO (16.5±3.2 - 18.3±2.6 m M) as compared to the uninfected chickens (5.5±1.6 m M) when inoculated with Georgia or a field strain of IBDV. Interestingly, the levels of NO in T-cell suppressed IBDV infected chickens (6.2±1.4 -7.8±2.2 m M) were almost comparable to uninfected control chickens in spite of markedly severe hemorrhagic lesions observed in this group. The significance of the transient induction of NO during IBDV infection will be discussed with respect to the lesion formation and its antiviral effect.

Source : IPSACON-2005

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