Negative staining of a non-haemadsorbing strain of African swine fever virus

Since the application of negative staining, preceded by fixation, prevents the disruption and distortion of the capsid of the African swine fever virus, improved contrast and evaluation of the appearance and size of virus particles in the electron microscope is possible and, in addition, the icosahedral shape of the virus is demonstrable. The mature virus particle contains at least 2 capsid layers and an outer envelope.

Purification and physicochemical characteristics of African swine fever virus

Methods for the purification of African swine fever virus (ASFV) and its dissection into two fractions are described. The difficulties which have been encountered previously in attempts to purify the virus, namely contamination with large amounts of cellular constituents and aggregation of the virus particles, have been overcome by treatment with Tween 80 and by the use of 1 M-NaCl in the sucrose gradients. Five major polypeptides, mol. wt. 10(3) X 125 (VP1), 76 (VP2), 50 (VP3), 44 (VP4) and 39 (VP5) were found in the purified particles. The virus was dissected by treatment with Nonidet NP 40 into (a) a fraction which had the appearance of an empty capsid shell and capsid shell and contained the polypeptides VP2 and VP3 and (b) a structure containing VP1 and VP4. The location of VP5 was not ascertained.

Ultrastructural study of African swine fever virus replication in cultures of swine bone marrow cells

Cultures from pig bone marrow cells were infected with ASFV and the replication cycle was studied. In the cytoplasmic replication areas there are a differentiation of membrane segments. Some of them are polygonal, which give rise to virus particles. An over production of viral coded materials, including non-polygonal membranes seems to be an important feature of the replicative cycle of ASFV in this cell system. Viruses are released enveloped with a cellular membrane. Paracrystalline arrays of viruses are seldom seen in the cytoplasm. At no time did we see viruses in the nucleus. Infected cells showed marked cytopathic effect, beginning at early times post infection.