Infectious salmon anemia virus specifically binds to and hydrolyzes 4-O-acetylated sialic acids.
Infectious salmon anemia virus (ISAV) is the causative agent of infections in farmed Atlantic salmon. ISAV presumably represents a new genus within the Orthomyxoviridae. ISAV has been shown earlier to exhibit a receptor-destroying activity, which was defined as an acetylesterase with unknown specificity. We have analyzed the substrate specificity of the ISAV esterase in detail. Purified ISAV hydrolyzed free 5-N-acetyl-4-O-acetyl neuraminic acid. In addition, the purified 9-O-acetylated sialic acid derivative was also hydrolyzed, but at lower rates. When we used a glycosidically bound substrate, ISAV was unable to hydrolyze 9-O-acetylated sialic acid, which represents the major substrate for the influenza C virus esterase. ISAV completely de-O-acetylated glycoprotein-bound 5-N-acetyl-4-O-acetyl neuraminic acid. Thus, the enzymatic activity of the hemagglutinin-esterase of ISAV is comparable to that of the sialate-4-O-esterases of murine coronaviruses and related group 2 coronaviruses. In addition, we found that ISAV specifically binds to glycoproteins containing 4-O-acetylated sialic acids. Both the ISAV esterase and recombinant rat coronavirus esterase specific for 4-O-acetylated sialic acids hydrolyzed ISAV receptors on horse and rabbit erythrocytes, indicating that this sialic acid represents a receptor determinant for ISAV.
Fish Health Section, National Veterinary Institute, N-0033 Oslo, Norway.
Audny
A
Hellebø
Ulrike
U
Vilas
Knut
K
Falk
Reinhard
R
Vlasak
D000107:Acetylation; D000115:Acetylesterase / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D004912:Erythrocytes / Q000378:metabolism; D006736:Horses; D006868:Hydrolysis; D009975:Orthomyxoviridae / Q000378:metabolism*; D011817:Rabbits; D020317:Salmo salar / Q000821:virology*; D012794:Sialic Acids / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
D012794:Sialic Acids; D000115:Acetylesterase