Purification of a herpes-like virus from abalone ( Haliotis spp.) with ganglioneuritis and detection by transmission electron microscopy

Abstract

A herpes-like virus was for the first time purified from abalone diagnosed with ganglioneuritis. Pleuropedal ganglia, pedal nerve cords, head and epipodial tissue was collected and homogenized from abalone populations exhibiting high mortality and clinical signs consistent with herpes-virus like ganglioneuritis. Following ultracentrifugation by sucrose gradient prepared in sea-water, the purified virus was negatively stained and examined under a transmission electron microscope. Virus particles were observed to have an icosahedral capsid appearance surrounded by an envelope with numerous spikes on the external surface. The capsid ranged 92–109 nm in diameter and the enveloped virus was approximately 150 nm in diameter. Virus particles were found mainly at the interface of 40–50% sucrose gradients, and a few presented at the interface of 50–60% sucrose gradients. Isopycnic gradient centrifugation was performed in a potassium tartrate gradient and caesium chloride gradient, where the buoyant density of the herpes-like virus was determined to be 1.17–1.18 g/mL. The use of sea-water as the buffer in preparation of the gradient was critical in the preliminary purification of the herpes-like virus, and more efficient harvesting of the virus was achieved by sucrose and potassium tartrate gradients than caesium chloride gradient. The described method, whilst proving successful for purifying a herpes-like virus from abalone, may also be applicable to other viruses from marine animals.