ABSTRACT
The purpose of this study was to determine to what extent nitric oxide (NO) may play a role in the antiviral-mediated effect of chicken IFN-gamma against the Marek's disease virus (MDV) RB-1B. NO-generating compounds S-nitroso-N-acetylpenicillamine (SNAP) and 3-morpholino-sydononimine (SIN-1) strongly inhibited RB-1B replication in chicken embryo fibroblasts (85%) in a dose-dependent manner. The addition of superoxide dismutase (SOD) did not alter the inhibitory effect of SIN-1, which is also known to generate superoxide anions. IFN-gamma-stimulated embryo fibroblasts almost totally suppressed viral replication and were high NO producers. Nevertheless, addition of N(G)-monomethyl-l-arginine (l-NMMA), a competitive inhibitor of NO synthase, inhibited NO production without preventing the dramatic viral suppression. IFN-gamma-stimulated chicken bone-marrow macrophages were good NO producers and demonstrated a specific cell dose-related inhibiting effect on RB-1B replication in bystander fibroblasts (around 60% at 10(6) macrophages). Adding l-NMMA together with oxygen scavengers such as SOD or d-mannitol restored viral replication almost completely. In conclusion, NO alone is a powerful inhibitor of MDV replication in chicken fibroblasts. Nevertheless, NO is not responsible for the direct inhibitory effect of the IFN-gamma treatment of fibroblasts and is only partially involved in the inhibitory effect of IFN-gamma-stimulated macrophages, which is also mediated by reactive oxygen intermediates.
Subject(s)
Herpesvirus 2, Gallid/physiology , Interferon-gamma/physiology , Nitric Oxide Donors/pharmacology , Nitric Oxide/physiology , Virus Replication/drug effects , Animals , Bone Marrow Cells/cytology , COS Cells , Cells, Cultured , Chick Embryo , Chickens , Chlorocebus aethiops , Coculture Techniques , Fibroblasts , Herpesvirus 2, Gallid/drug effects , Macrophages/physiology , Macrophages/virology , Molsidomine/analogs & derivatives , Molsidomine/pharmacology , Penicillamine/analogs & derivatives , Penicillamine/pharmacology , S-Nitroso-N-Acetylpenicillamine , Superoxide Dismutase/pharmacology , Superoxides/metabolism , Virus Replication/physiology , omega-N-Methylarginine/pharmacologyABSTRACT
Acemannan (ACM 1), a beta-(1,4) -acetylated mannan isolated from Aloe vera, can be used as an effective adjuvant in vaccination against some avian viral diseases. Our results demonstrate a quick and lasting in vivo priming effect of ACM 1 on macrophage response after intramuscular inoculation in chickens (500 microg per 2-month-old bird). In response to IFN-gamma in vitro, monocytes from ACM 1-treated chickens exhibited a strong enhancement of NO production from 3 to 9 days p.i., but a weaker effect on MHC II cell surface antigen expression on day 3 p.i. A stimulating effect of ACM 1 treatment was also observed on spontaneous and inducible NO production for splenocytes only on day 3 p.i. By that time, splenocytes exhibited a strong higher capacity to proliferate in response to the T cell-mitogen PHA. At the same time, the in vivo capacity to produce NO, measured by the (NO(-)(2)+NO(-)(3)) serum level after intravenous LPS injection, increased greatly from 3 to 9 days p.i. In conclusion, ACM 1 was able efficiently and durably to increase the activation capacity of macrophages from the systemic immune compartment (in particular from the blood and spleen after an intramuscular injection) in chickens, especially for NO production. These findings provide a better understanding of the adjuvant activity of ACM 1 for viral and tumoral diseases.
