Biomedical subjects
Publications and source records attributed to H Schellekens.
In a double-blind trial renal allograft recipients were treated with fibroblast interferon preparations for 3 months in an attempt to prevent viral infections. Interferon therapy did not reduce the overall incidence of viral infections. No adverse effects were noted on liver function, platelet counts, or leucocyte counts, or acute rejection episodes.
The toxicity of interferon to bone marrow was studied by the use of in vitro colony forming assays for hemopoietic cells. In the same study the relative inhibitory effects of two clinically common interferon preparations, leukocyte and fibroblast interferons, were compared with regard to their effect on both myeloid [colony-forming unit, culture (CFUc)] and erythroid [colony-forming unit, erythroid (CFUe)] progenitor cells. CFUe formation in human bone marrow cells in vitro appeared to be fairly resistant to both interferons. Only high doses of both interferons gave a marked inhibition of CFUe. However, the toxicity of leukocyte and fibroblast interferon was divergent for CFUe in human bone marrow. Leukocyte interferon appeared to be considerably more inhibitory for CFUe than was fibroblast interferon. The effects of mouse interferon, induced in L929 cells, on the growth of CFUc and CFUe in murine bone marrow cells were comparable with those of fibroblast interferon on human cells. The toxicity of human and murine interferon was species specific. Except for the toxicity of leukocyte interferon to CFUc in human bone marrow, the toxicity of interferon was marked only with concentrations on interferon far exceeding the amount necessary to produce an antiviral state in vitro.
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The effect of interferon on the replication of vesicular stomatitis virus (VSV) and type-C oncornavirus in two Balb/c mouse cell lines, JLS-V5 and JLS-V9R, infected with MuLV-R was examined. VSV replication was inhibited threefold (0-5 log10) in both cell lines by 10 to 20 units of interferon/ml. In JLS-V5 cells C-type virus yields, as measured by 3H-uridine incorporation and reverse transcriptase activity, were also reduced threefold by 10 to 20 units of interferon/ml. However, in JLS-V9R cells, C-type virus replication was refractory to interferon at concentrations up to 1 x 10(4) units/ml. Infectious C-type virus transmitted from JLS-V9R cells to Balb/3TS cells was as sensitive to interferon as virus transmitted from JLS-V5 cells, indicating that resistance of C-type virus in JLS-V9R cells is a feature of the cells rather than of the virus strain.
The effect of emetine on the in vivo production of interferon by Swiss mice stimulated with poly-i: poly-C, was studied. 100 mug of emetine per mouse yielded a 16-fold increase in interferon production. Maximal production of interferon was achieved 2 h after the simultaneous injection of emetine and poly-I: poly-C.
Hepatitis delta (delta) virus (HDV), a satellite virus of the hepatitis B virus (HBV), causes a severe form of viral hepatitis in humans. Here we present evidence based on electron microscopy and electrophoretic behaviour that HDV contains a single stranded circular RNA molecule. This is the first animal virus identified with a circular RNA genome. Circular RNAs have only been found in plant viruses. We have obtained a partial complementary DNA clone representing approximately 25% of the total genome of HDV. Analysis of this cDNA revealed similarity to two plant viruses that may explain the origin of the virus.
This study was designed to test the hypothesis that T-cell effector mechanisms are required for protective immunity to malaria sporozoites. Administration of neutralizing monoclonal antibodies against gamma interferon (gamma IFN) to immune hosts, reversed sterile immunity to sporozoite challenge, by allowing the growth of exoerythrocytic forms (EEF) and thus the development of parasitaemia. Immune animals also developed infections when depleted in vivo of their suppressor/cytotoxic T cells expressing the CD8 antigen (CD8+) but not when depleted of helper T cells expressing CD4 antigen (CD4+), before sporozoite challenge. Passive transfer of immune immunoglobin alone, or adoptive transfer of immune T cells alone, conferred partial protection to naive recipients. Transfer of both immune components resulted in significantly greater protection. This transferred immunity was reversed by the in vivo neutralization of gamma IFN. Thus, sterile immunity to sporozoite challenge requires the neutralization of sporozoites by antibodies and the inhibition of EEF development by gamma IFN with the participation of CD8+ cells.
We studied the effect of rat rec-IFN-gamma, human rec-IL-2, and an IgG1 monoclonal antibody (DB1) directed against rat IFN-gamma on allograft survival in the rat in various experimental conditions. The DB1 monoclonal antibody did not prolong heart allograft survival in the (LEW/BN)F1 to LEW combination, even when used at high doses (2 mg/rat x 9 days). Rec-IFN-gamma induced major histocompatibility antigen expression in vivo, but its administration had no effect on the graft survival either of untreated LEW recipients of (LEW x BN)F1 heart allografts or of donor blood-transfused LEW recipients. In addition, rec-IFN-gamma alone had no effect on graft survival in cyclosporine-treated rats. In contrast, rec-IL-2 shortened heart allograft survival both in untreated and in cyclosporine-treated recipients. Rec-IFN-gamma partially reversed the effects of rec-IL-2 in cyclosporine-treated rats. The data suggest that in vivo administration of IFN-gamma in allograft recipients may have a suppressor effect, in addition to the postulated augmenting effect on the immune response by increasing MHC antigen expression.
In a study of 6,389 male cancer patients diagnosed and treated at the Cancer Control Agency of British Columbia from 1950-1975, several associations were detected between occupation and specific cancers. Elevated risks for lung cancer were seen in miners, metal processors and machinists, while a reduced risk was seen in farmers. Lip cancer excesses were detected in individuals involved in several outdoor occupations, and melanoma excesses were seen for three groups of predominantly indoor workers. These results confirm previous findings in the literature, whereas the following associations have not been previously reported. Fishermen were found to have an excess of Hodgkin's Disease (RR = 3.0, 95% C.I. = 1.4,6.5), engineers are at an elevated risk of cancer of the pancreas (RR = 4.2, C.I. = 1.8,9.9), and forestry workers have an elevated risk of bladder cancer (RR = 1.7, C.I. = 1.1,2.6). Further studies will be needed to replicate the new associations detected here.