Examination of latent infection in germfree mice for some murine viruses

Sera from some groups of germfree mice were examined for reactivity against Sendai, reo 3, Theiler's GD VII, ectromelia, and mouse hepatitis virus antigens. Of 51 sera collected in September and October 1976 and in August and September 1977 from one germfree mouse breeding colony, there was no positive reaction against all the antigens tested. Moreover, the attempt of virus isolation from homogenates of various organs including lungs, liver, kidneys, and intestines of 6 germfree mice was unsuccessful.

[A new method for the determination of serum human placental lactogen (HPL) by single radial immunodiffusion (author's transl)]

The general radioimmunoassay (RIA) currently employed for the determination of serum HPL requires a special apparatus and a complicated technique. Therefore, in order to simplify the assay we tried to develop a new method using single radial immunodiffusion (SRID). Basic examinations were made to establish a simplified HPL assay method by SRID. The optimal conditions finally decided for SRID were as follows: the thickness of the agar plate, 1.5 mm; the diameter of the well, 3 mm; the amount of antigen added, 10 microliter; antibody concentration, 1.0% for the measurement range from 1.0 microgram/ml to 16 microgram/ml and 0.5% for the measurement range from 0.25 microgram/ml to 1.0 microgram/ml. Under these conditions serum HPL was detectable after the 9th week of gestation, and antigen was measurable over 0.25 microgram/ml. Serum HPL values measured by RIA and SRID from the 9th to the 42nd week of gestation in 138 normal pregnant women were identical, and the correlation was highly significant (r = 0.842, p less than 0.001). This SRID method was as reliable and sensitive as the RIA and made it easier than the RIA to measure the serum HPL of pregnant women. Therefore, with regard to placental function its clinical application should prove to be certainly beneficial.

Suppression of interferon production in mouse spleen cells by cytochalasin D

Cytochalasin D is thought to impair microfilament function. The present study has investigated its effects on four different systems in which interferon is formed, namely (1) mouse fibroblasts induced with virus (2) mouse spleen cells induced with virus, or (3) with endotoxin or (4) by allogeneic stimulation. Cytochalasin D did not suppress formation of interferon by fibroblasts (L cells) or spleen cells stimulated with either HVJ or NDV. However it did suppress production of interferon by spleen cells in response to endotoxin or an allogeneic stimulation; here its action was apparently not on the secretion of interferon, but on some earlier event. It also suppressed the production of interferon by mouse spleen cells induced with HVJ if this had been u.v. irradiated for more than 15 min: this suggests that cytochalasin D sensitive structures do play some role in interferon production by mouse spleen cells when stimulated with HVJ, as well as when they are stimulated with endotoxin or an allogeneic stimulus.

Properties of the viruses selected during persistent infection of L cells with VSV

Two virus clones, VSV-mp and VSV-sp, were isolated from L cells persistently infected with VSV (New Jersey serotype). Both clones were more temperature sensitive than the parent virus, VSV-o, and grew more slowly, gave smaller plaques, less c.p.e. and lower virus yields in L cells. Unlike the parent virus, both persistent viruses induced interferon production in L cells. Stable carrier cultures could be obtained from L cells infected with VSV-sp at low multiplicities without pretreatment with interferon. This may be related to the fact that VSV-sp is more sensitive to interferon than either VSV-mp or VSV-o.

Tallysomycin, a new antitumor antibiotic complex related to bleomycin. III. Antitumor activity of tallysomycins A and B

The antitumor activity of tallysomycins A and B was determined in five experimental tumor systems in mice. Tallysomycins A and B were highly active against B16 melanoma, sarcoma 180 ascites tumor and Lewis lung carcinoma, and moderately active against P388 leukemia but were without effect on lymphoid leukemia L1210. The antitumor activity of tallysomycin A was 2 to 3 times that of tallysomycin B and 3 to 17 times that of bleomycin. Tallysomycin A was about 1.5 and 4 times more toxic for mice than tallysomycin B and bleomycin, respectively, in terms of subacute LD50 values.

Comparative studies on cytopathic effects induced by vesicular stomatitis virus in two cell types

Infection of mouse L cells with vesicular stomatitis virus (VSV) leads to an extensive cell fusion, while porcine kidney stable (PS) cells infected with VSV show only cell rounding. Therefore, comparative morphological studies on the infection of the two cell lines were carried out using a transmission or scanning electron microscope and an immunofluorescence microscope. PS cells infected with VSV contrasted to L cells infected with the same virus in the following two points; (1) the principal site of VSV maturation was the intracytoplasmic vacuolar membrane in PS cells and the plasma membrane in L cells. However, it was found that viral glycoprotein was present on the cell surface of infected PS cells; (2) the morphological changes at the cell surface of infected PS cells occurred much earlier and were severer than those at the cell surface of infected L cells. From these observations, we discuss the possibility that the surfaceembrane of PS cells is too sensitive to the VSV-induced cell damage to cause cell fusion.

Studies of L cells persistently infected with VSV: factors involved in the regulation of persistent infection

Infection of interferon-treated L cells with VSV led frequently to the establishment of L cells persistently infected with VSV (LVSV cells). These cells were characterized by the following properties; (I) no supplement of antiviral factors such as anti-VSV antiserum, interferon, was required for their maintenance; (2) virus antigens were detected in about 5 to 30% of the cells by immunofluorescence staining; (3) the cells were not only resistant to superinfection by homologous virus, but also resistant to challenge by heterologous viruses such as Mengo virus; (4) the cells were destroyed by co-cultivation with heterologous cells susceptible to VSV infection; (5) the cells could be cured by serial cultivation in medium containing antiviral antibody, and the cured cells were as susceptible to VSV as normal L cells. It was shown that at least three factors (interferon, defective interfering [DI] particles and a selection of small-plaque temperature-sensitive [ts] mutants) took part in the maintenance of LVSV cells although it was difficult to evaluate exactly the relative importance of these factors. The effect of antiviral antibody, interferon and incubation temperature upon the maintenance of LVSV cells are discussed further.

The effects of cytochalasin and colchicine on interferon production

The present study was undertaken to investigate the mechanism of interferon production by mouse spleen cells co-cultivated with BHK-HVJ cells, i.e. baby hamster kidney cells persistently infected with the HVJ (or Sendai) strain of para-influenza I virus. Cytochalasin B appears to inhibit an early stage in the process and colchicine a relatively late stage. It is suggested that microfilaments and microtubules may play in important role at an initial stage of interferon production in this system.

Polykaryocyte formation induced by VSV in mouse L cells

Infection of mouse L cells with VSV leads to the formation of polykaryocytes about 4 to 12 h p.i. When anti-VSV immune serum was added during the course of infection, progression of cell fusion was soon suppressed. Cycloheximide completely suppressed the cell fusion when the drug was added within 1 h p.i., while the cell fusion was not suppressed at all when the drug was added at and after 3 h. Early polykaryocyte formation, 'fusion from without', was observed only at a low level in cells infected at very high multiplicities. The development of cell fusion induced by VSV was found to be different in several cell types, although all these cells produced a rather high yield of virus: L and C-243-3 mouse cell lines showed a high level of polykaryocytosis (80 to 100%), BHK and RK-13 cells responded at low level, and PS and Vero cells showed no cell fusion in response to VSV infection. In PS cells, however, cell fusion occurred when VSV-infected L cells were co-cultivated. From these observations, the mechanism of cell fusion induced by VSV was discussed.

Relationship between establishment of persistent infection of haemagglutinating virus of Japan and the properties of the virus

The infectious virus (HVJ-pi) obtained from BHK cells persistently infected with haemagglutinating virus of Japan was found to be temperature-sensitive as well as causing little or no cytopathic effect (c.p.e.) and leading to establishment of carrier cultures in several cell lines at both permissive (32 degrees C) and non-permissive (38 degrees C) temperature. In order to obtain information about the role of HVJ-pi in the establishment of persistent infection, comparative studies were made of some phenotypic properties of HVJ-pi and HVJ-38 which was obtained by passing wild-type HVJ in eggs at 38 degrees C and was proved to be highly cytopathic. HVJ-pi differed from HVJ-38 in (1) temperature sensitivity in its ability to produce virus progeny, (2) infectivity for embryonated eggs, (3) neuraminidase activity, (4) the thermal stability of HA and neuraminidase activity, and (5) the polypeptide composition of BHK-grown viruses. B cells infected with HVJ-pi release haemagglutinin more efficiently, and less HA was accumulated on the cell membrane. In considering these results, it was concluded that the difference of envelope proteins might be involved in the striking difference in c.p.e. between HJV-pi and HVJ-38.

Pathogenesis of Sendai virus infection in the central nervous system of mice

The present study was aimed to clarify the pathogenesis of Sendai virus infection to the central nervous system (CNS) of mice. One-to 2-day-old suckling and 4-week-old mice were inoculated intracerebrally with the virus. The virus multiplied higher in suclings than in adults. Immunofluorescent studies in sucklings revealed that the viral antigens appeared initially in ependyma, choroid plexus epithelium, and meninges. Subsequently they spread to subependymal cells and finally were found in neurons of hippocampus for as long as 4 months postinfection. In adults, however, the viral antigens rapidly disappeared in the early stage. Most mice inoculated intracerebrally with Sendai virus appeared healthy, although hydropcephalus developed in a few mice. Virus-specific antibody and interferon production seemed to have no influence on the persistent infection of Sendai virus in the CNS of mice. One of the most significant findings may be that the viral antigens persist in the brain for as long as 4 months in a latent form. This may offer a useful model for the study of latent CNS infection of paramyxoviruses.

Effect of antitumor agents on sarcoma-180 tumor cells transplanted to liver, kidney, and lung

The survival time of animals, inhibition of the incorporation of thymidine-[6-3H] (3H-TdR) into DNA, and histopathological observation were made after the injection of Mitomycin-C, Bleomycin, cyclophosphamide, Daunomycin, Actinomycin-D, or 5-fluorouracil into mice transplanted with sarcoma-180 to their liver, kidney, and lung. The most prolonged survival time was obtained by the injection with cyclophosphamide and a moderate prolonged survival by Bleomycin and Actinomycin-D. In the case of 5-fluorouracil and Daunomycin, there were extreme variations in the survival time depending on the site of tumor growth. Cyclophosphamide and 5-fluorouracil showed greater and longer lasting inhibition of the incorporation of 3H-TdR into DNA of the tumor tissue, whereas the remaining agents caused transient inhibition on the tumor tissue. Inhibitory ratio and duration of the incorporation of 3H-TdR into DNA of normal site of the tissue of tumor-bearing organ were found to be more increased or almost the same compared with those of the tumor tissue. The most rapid recovery of the incorporation of 3H-TdR into DNA was observed in the small intestine among various organs and tumor in any treatment groups. From the histopathological observation, the degree of tumor cell damage by the agent was almost in agreement with inhibition of the incorporation of 3H-TdR up to 72 hr after the treatment.

Temperature-sensitive virus derived from BHK cells persistently infected with HVJ (Sendai virus)

BHK-HVJ cells, a cell line of baby hamster kidney cells persistantly infected with HVJ (Sendai virus), started to produce infectious virus by shifting down the incubation temperature from 38 to 32 C. The virus derived from BHK-HVJ cells, designated as HJV-pB, was effectively neutralized with antibody against wild-type virus (HVJ-W) which was used for the establishment of BHK-HVJ cells. HVJ-pB replicated in eggs at 32 C, but not at 38 C, while HVJ-W grew equally well at both temperatures. When BHK cells infected with HVJ-PB were incubated at 38 C, production of infectious virus, hemagglutinin, and neuraminidase was markedly restrained, whereas a considerable amount of viral nucleocapisid and envelope antigens was detected in the cells by complement fixation tests. These viral activities became detectable immediately after temperature shift-down from 38 to 32 C even at the later stage of infection. HVJ-pB was indistinguishable from HJV-W with respect to particle size, density, and morphological characteristics, but appeared to possess a higher neuraminidase activity and was inactivated more rapidly at 50 C than HVJ-W. HVJ-pB was less cytocidal and could easily cause latent infection in BHK and mouse L cells.