Immunofluorescent analysis of murine leukemia virus-infected cells by flow microfluorometry.

Flow microfluorometric assay with a Cytofluorograf model 4801 in combination with immunofluorescence was applied to the quantitative assay of cells exogenously infected with mouse leukemia viruses and to the chemical induction of virus in AKR cells. The Cytofluorograf provides sensitivity equal to the visual method and is capable of assaying up to 5000 cells/sec with specificity equivalent to that of the direct visual immunofluorescence assay, thereby providing a large, statistically valid sampling in a fraction of the time required by visual counting. Flow microfluorometry also provides a method of quantitatively resolving fluorescent cell populations on the basis of relative size and degree of fluorescence.

Multiplicity of Scrapie virus in infected mouse spleen cells in vivo.

Subpopulations of spleen cells from scrapie virus-infected mice were used to determine the average virus content of infected cells in vivo at a time when virus was rapidly increasing in titer in lymphoreticular tissues. Comparison of the mean lethal doses of lysed to intact cells indicated averages of 2 to 6 infectious units per infected cell. In another experiment, preparations of cytoplasmic nucleic acids extracted from spleen cells of infected mice had no detectable infectivity, which suggests that the transmissible form of the virus is not a free nucleic acid.

Isolation from mouse spleen of cell populations with high specific infectivity for scrapie virus.

Spleen cells from mice infected with scrapie virus were separated into subpopulations on the basis of buoyant density in discontinuous gradients of isotonic albumin or differential adherence of cells to plastic. At three different intervals after infection, a population of "less dense" cells was found in albumin gradients that had 40-to 60-fold higher specific infectivity (cells per median lethal dose) than the total cell suspension before gradient sedimentation. The class of cells associated with high relative specific infectivity has a density characteristic of lymphoblasts, myeloblasts, and macrophages. Separation of "macrophage rich" cells on the basis of adherence to plastic did not result in significant enrichment of scrapie virus-infected cells.

Evaluation of an antimicrobial soap formula for virucidal efficacy in vitro against human immunodeficiency virus in a blood-virus mixture.

The virucidal efficacy of a health care personnel hand wash product containing 0.5% parachlorometaxylenol in a sodium C14-16 olefin sulfonate formula was evaluated in in vitro tests with human immunodeficiency virus type 1 (HIV-1) in the presence of 50% whole human blood. The HTLV-IIIRF strain of HIV-1 was suspended in 50% medium-50% whole human blood and exposed to various dilutions of the hand wash product for 30 or 60 s. Following detoxification, residual infectivity was determined by a lytic cytopathogenic assay in MT2 cell cultures. No infectious HIV could be detected after a 30-s exposure to the hand wash product at dilutions of 1:5 and 1:10 and after a 60-s exposure at dilutions of 1:5, 1:10, 1:20, and 1:30. More than 99.9% of the virus was inactivated at these dilutions and exposure times.

Potent and selective activity of a new carbocyclic nucleoside analog (carbovir: NSC 614846) against human immunodeficiency virus in vitro.

Carbocyclic 2',3'-didehydro-2',3'-dideoxyguanosine (Carbovir: NSC 614846), a novel nucleoside analog, emerged as a potent and selective anti-HIV agent from a large screening program conducted by the National Cancer Institute and its contractors. Its hydrolytic stability and its ability to inhibit the infectivity and replication of HIV in T-cells at concentrations of approximately 200- to 400-fold below toxic concentrations make carbovir a top-priority candidate for development as a potential antiretroviral agent in the treatment of AIDS patients.