Unusual production of gross murine leukemia virus (GrMuLV) in murine lymphoblasts as studied by electron microscopy

Abstract

The production of murine leukemia virus (GrMuLV) in a clonal line of Gross virus-induced murine lymphoblasts was studied by scanning and transmission electron microscopy (SEM and TEM, respectively). Most virions were found distributed randomly over the cell surface membrane as single particles. In rare cases, a large cluster of virions had accumulated on the cell surface membrane. SEM showed that, in such clusters, many virions with diameters ranging from 88 to 140 nm were tightly interconnected with one another, some appearing to bnd directly from the cell surface membrane. TEM revealed an abnormally large virion (165 nm in diameter) present in a cluster. The core structure of this virion was an open circle in which both free ends were further circled within the circle. The core length was longer (485 nm) than normal (220 nm). These observations suggest that GrMuLV can be produced in a cluster accompanying simultaneous production of an abnormally large virion with an atypical core structure.