Serum albumin inhibits echovirus 7 uncoating

Echoviruses induce a wide spectrum of diseases in man, the most severe bein g meningitis. In neonates, however, a severe systemic infection can be obse rved, leading to death. Serum albumin is the most abundant protein in plasm a and most interstitial fluids, and its functions include osmoregulation an d transport and delivery of hydrophobic molecules such as fatty acids and s teroids. The results of cold-synchronized one-step growth analysis of echov irus 7 infection and sucrose-gradient analysis of A-particles suggest that physiological concentrations of albumin block echovirus 7 infection by inhi biting uncoating. The blockage was reversible and was still effective when albumin was added 30 min after virus adsorption. Inhibition of uncoating wa s confirmed by using rhodanine, a known specific inhibitor of echovirus unc oating. After removal of the albumin blockage, addition of rhodanine perpet uated the inhibition. Serum and interstitial albumin concentrations may lim it echovirus infection in vivo and thereby act as an extracellular determin ant for echovirus tropism.