Method of virus particle counting using millipore filtration

Electron microscopy of the nucleocapsid from disrupted Moloney murine leukemia virus and of associated type VI collagen-like filaments

To analyze the constituents of retroviruses, the Moloney murine leukemia virus was disrupted and observed by dark-field electron microscopy. Virus disruption was achieved by several methods: osmotic shock, freezing-thawing cycles, and exposure to urea up to 4 M, to NaCl up to 1 M, and to Triton X-100. Several components associated with broken Moloney murine leukemia virus were repeatedly found in preparations. These components have been described as rings, thick filaments, chain-like filaments, threads covered with proteins, threads with buckles, and naked threads. A quantitative analysis of the occurrence of these components has been carried out. Among them, the thick filaments composed of a compact helical arrangement of small beads 5 nm in diameter were considered to represent the nucleocapsid. The protease-sensitive buckles found on some threads could be a compact form of the viral RNA associated to the nucleocapsid protein NCp10. The RNase-sensitive naked threads are interpreted as the deproteinized viral RNA itself. The ubiquitous chain-like filaments possess a periodic structure identical to that of polymerized type VI collagen. It is proposed that this adhesive protein is associated with the viral envelope taken from the cell membrane during the budding process of retroviruses.

Inhibition of human immunodeficiency virus (HIV) type 1 multiplication by an avian cellular factor

A factor secreted from avian cells infected non productively with a non cytopathogenic mutant of vesicular stomatitis virus (VSV ts 1026) interferes with HIV replication in CEM cells and peripheral blood monocytes (PBL). Production of infectious particles is decreased and many virions lack cores and/or spikes. In CEM cells the prmRNA is spliced into 7.5, 4, and 2 kb mRNA. Residual virus contains less env encoded proteins and p 18; p 25 appears as several bands. The processing of tat, rev. and nef proteins differs in treated cells and in controls.

Replication of human immunodeficiency virus in HL-60 cells

HL-60 cells carrying the CD4 marker could be productively infected with human immunodeficiency virus (HIV) but did not form syncytia, though 11-14 days p.i., there was a transient decrease in cell multiplication and viability. After prolonged passage, a subpopulation of HL-60 cells was selected. The virus produced differed from the initial input virus grown on CEM cells: the virions lacked knobs, were either empty or had abnormal cores, had a higher ratio p24/gp41,gp110 and were less infectious. After prolonged passage, virus was produced which was fully infectious for CEM but not for fresh HL-60 cells, and which ressembled the input virus with respect to morphology and p24/gp41,gp110 ratio.

Virus expression in different tissues of normal and tumor-bearing mice inoculated with a murine leukemia virus

Evolution of virus expression in different lymphoid organs as well as in solid syngeneic tumors of mice inoculated with an MuLV was studied with the aid of in vitro XC co-culture technique. When normal adult mice of strain XLII were inoculated intraperitoneally with a cultured Rauscher virus (RC), the virus could be detected, 10 days after inoculation, only in bone marrow in small amounts and thereafter no virus could be found in any of the organs tested, including bone marrow, spleen, thymus, lymph node and kidney. However, when age- and sex-matched parallel mice bearing syngeneic subcutaneous non-viral tumors were inoculated similarly with the RC virus, the virus could be detected abundantly not only in bone marrow and spleen but also in tumors during the first 3 weeks and even 6 weeks after virus inoculation. Transitional decrease or disappearance of the virus was observed around the 25th-31st day in organs and tumors of the inoculated mice. When the tumor mass was removed from these mice by surgery, the virus disappeared rapidly and definitely from all the organs tested. The virus recovered from in vitro explanted and cultured tumors, taken from mice inoculated with the virus, induced typical lymphoid leukemia in BALB/c mice inoculated as newborns. However, from certain aspects (hypertrophy of the thymus and lymph nodes), this virus was different from the original RC virus.

A quantitative comparison between in vivo-and in vitro-derived Friend leukemia virus

The biological activities of RNA viruses derived from Friend leukemia cells in culture (TCV) were compared with those of viruses derived from the plasma (PV) of mice infected with Friend leukemia virus (FLV). The comparison was quantitatively based on the actual number of viruses used in each experiment as determined by counting under the electron microscope. Electron microscopy also provided a qualitative assessment of the structural integrity of the concentrated virus particles used in various bioassays. The data shows that the leukemogenic and spleen-focus-forming (SFF) activities of TCV, although demonstrable, are respectively 10(5) and 10(4) lower than those of PV. Moreover, TCV has 10(4) less helper activity (S+L- test) than PV. The level of reverse transcriptase activity is ten times lower in TCV than in PV which indicates that there is little correlation between polymerase activity and the other biological activities measured. The decreased biological activity of the in vitro grown virus is thought to be intrinsic to this type of virus although all extrinsic factors have not been ruled out.

Recovery of small quantities of viruses from clean waters on cellulose nitrate membrane filters

A method is described for quantitatively recovering small amounts of viruses from large volumes of buffered, distilled water. Development of the method was motivated by the anticipated need for testing large volumes of renovated sewage for viruses. The method consists of adsorbing viruses onto cellulose nitrate membrane filters (0.45 mum pore size) from water containing sufficient Na(2)HPO(4) to produce a molarity of 0.05 and sufficient citric acid to produce a pH of 7, and eluting the adsorbed viruses in 3% beef extract under extended sonic treatment. Complete recovery of poliovirus 1, echovirus 7, and coxsackievirus B3 resulted when less than 100 plaque-forming units were added to 1-liter quantities of water. Recoveries of reovirus 1 were almost as good. Preliminary studies indicate that good recoveries can be made from 25-gal quantities of water. The method described is efficient in waters of high quality and may be useful for recovering viruses in renovated, and perhaps in tap waters, but not in waters containing certain organic matter unless that matter is first removed.