Search

This report describes the use of equilibrium gradients, RNA dependent DNA polymerase assays and electron microscopy (EM) in a combined assay for the rapid preliminary detection of intact retroviruses in crude preparations. Positive combined assays of platelets from preleukemic patients corresponded with karyotypic abnormalities found in these patients. Reconstruction experiments with Rauscher Leukemia Virus added to buffer or disrupted mouse spleen demonstrated the ease of detecting 10(9) or greater particles/g crude tissue, and the effects of buffer or added protein.

Neonatal ferrets were found to be highly via the intranasal route of inoculation to infection with wild type isolates of parainfluenza viruses. Wild type infection consistently resulted in deaths of these animals in 48 to 72 hours. Autopsy and histopathological findings in lung tissue were consistent with those of viral infection. Virus could consistently be isolated from lung tissues. Using wild green monkey kidney grown viruses and selected passage levels of egg adapted viruses, virus attenuation markers were observed by comparing infectivity in neonatal ferrets, propagation in cell cultures of human, primate, rabbit and chick embryo tissues, and in chick embryos and interferon induction. Adult pregant dams could be immunized (silently infected) and circulating hemagglutinin-inhibiting antibody could be detected within two weeks of intranasal instillation of wild and low egg passage types of virus. The animal model described could be valuable in studying immunity to parainfluenza virus infections.

A preliminary analysis of an RNA-directed DNA polymerase was made and a C-type virus-like particle was identified in platelets from 2 patients with the myeloproliferative disorder thrombocythemia (primary, essential, hemorrhagic, or idiopathic thrombocythemia). Platelet homogenates were centrifuged through a sucrose equilibrium density gradient. Both endogenous and exogenous DNA polymerase activity was found at a density of 1.19 g/ml. No activity was seen at comparable densities in control gradients. Electron micrographs of thin sections of these platelets revealed a particle with the morphologic characteristics of a C-type virus; however, the diameter of this particle was about 80 nm, slightly lower than that commonly found for C-type particles. Critical-point dried specimens, from the fractions of the sucrose gradient at which DNA polymerase activity was found, contained particles of the same size and morphology as those in the thin sections.

The effect of busulfan therapy on the activity of oncornavirus-like particles and chromosome patterns in patients with polycythemia vera and essential thrombocythemia was studied. Three patients had pretreatment platelet counts greater than 1 million/microliter, abnormal bone marrow karyotypes, and electron microscopic and biochemical evidence of oncornavirus. The results demonstrated that in all 3 patients virus-like particles and reverse transcriptase-like activity could no longer be found in the platelets within 2-4 weeks after the initiation of busulfan treatment. The platelet count was still elevated at this point for each patient, although the count returned to normal levels within 2-3 weeks after virus-like activity was no longer detectable. The chromosome patterns, characterized by aneuploidy (30-50%) before treatment, improved after therapy.

A chromosomal anomaly, 21q-, has been found in association with retroviral indicators in patients with myeloproliferative disorders (MPD) including polycythemia vera (PV), essential thrombocythemia (ET), chronic myelocytic leukemia (CML) and acute non-lymphocytic leukemia (ANLL). The viral indicators are found in platelet homogenates of thrombocythemic patients. Evidence is presented from 2 laboratories (Philadelphia, USA and Bologna, Italy) for the 21q- deletion in MPD patients. Thirty patients evaluated for the presence of both viral and chromosomal markers in Philadelphia showed positive correlations.

A new purification procedure was adopted for Eastern equine encephalitis virus which does not subject the virus to pelleting at any stage. Three- to 4-liter volumes were passed through a diethylaminoethyl cellulose column. The virus-containing fractions were banded on a sucrose cushion and finally concentrated in an isopycnic band in a linear sucrose gradient. This method reduced the volume 1,000-fold with a concomitant increase in viral titer, i.e., better than 90% recovery. Numerous criteria have been used to establish that this viral preparation was essentially free from cellular debris and nonviral material. Physical studies on this purified viral product were initiated. The sedimentation coefficient as determined by band sedimentation was 240S, the buoyant density in sucrose was 1.18 g/cc, and the diameter of the virus was 54 nm. From the diameter and the buoyant density it was possible to calculate the molecular weight of a spherical particle. In this case, the calculated molecular weight for Eastern equine encephalitis virus was 58 x 10(6) daltons.