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PURPOSE: The presence of replicating type C retrovirus in MBT-2 mouse bladder carcinoma cells is reported. This MBT-2 tumor cell line is nowadays globally distributed. The cells have been and are still used to study various aspects of bladder cancer. While studying the phagocytic capacity of MBT-2 cells for BCG organisms by electron microscopic methods, the presence of this retrovirus was noticed. MATERIALS AND METHODS: MBT-2 cells that were cultured in vitro as well as cells from intravesically and intradermally grown MBT-2 tumors from syngeneic mice were investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. RESULTS: All samples including the earliest generation MBT-2 cells that could be traced from stocks of other research groups contained the C type retrovirus, suggesting a contamination in all available generations of the MBT-2 cell line. CONCLUSIONS: As this tumor cell line is widely used in immunologic studies of the response to bladder cancer, it is important to consider the possible presence of type C viruses and associated antigens, since they could contribute to or interfere with the responses being measured. Studies should be initiated to determine whether viral antigen expression is involved in the immune rejection of MBT-2 bladder cancer. As a consequence, clinical implementation of immunological treatment strategies should not be based on results obtained with the MBT-2 model alone, but preferably should be confirmed with other (bladder) carcinoma models.

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Pasteurellaceae notably P. pneumotropica, have been associated with severe outbreaks of respiratory disease in several species of rodents. Host-specific parasitism of Pasteurellaceae in rodents has hardly been studied. Since host tropism in many bacteria involves adhesive mechanisms, we examined the hemagglutinating (HA) properties of 44 isolates from different rodent species (mouse (15) rat (8), hamster (9), gerbil (10) and Mastomys (2)). Only 13 mouse isolates and the 2 Mastomys isolates hemagglutinated human (type O Rh+) and canine red blood cells (RBCs). No HA was found using RBCs from 10 other animal species. HA was not inhibited by simple sugars and glycoconjugates, but was completely inhibited by heating of bacterial cells for 10 min at 80 or 100 degrees C, partially inhibited by glutaraldehyde and inhibited in a dose-dependent mode by NaIO4, suggesting the involvement of bacterial polysaccharide structures in the HA process. Enrichment procedures did not reveal the presence of HA- subpopulations in HA+ isolates or the presence of HA+ subpopulations in HA- isolates. Electron microscopy revealed the presence of fimbriae both in HA+ and HA- isolates. A regularly structured (RS) layer was detected on cells of part of the HA+ isolates only. Our results suggest that Pasteurellaceae of mice and Mastomys may be related and differ from isolates isolated from other rodent species.

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A virus with rhabdovirus morphology which proved to be antigenically distinct from rabies virus and vesicular stomatitis virus was isolated from a dolphin that had beached on the Dutch coast. Neutralizing antibodies to this virus were found in several European marine mammal species.

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Intravesical administration of Bacillus Calmette-Guérin (BCG) has been shown to be effective in the treatment of patients with superficial bladder cancer. For a better understanding of the mechanism of this antitumor activity, scanning and transmission electron microscope (SEM, TEM) studies were carried out to investigate morphological aspects of the interaction of BCG with the bladder wall in vivo and in vitro. Adherence of BCG to the bladder wall in vivo was studied 1 and 24 h after single or multiple (6x) BCG instillations in intact and in electrocauterized guinea pig bladders. Despite extensive search with SEM for its presence, virtually no BCG was found on the intact urothelium, and BCG was only occasionally observed in the coagulation lesions. SEM and TEM studies revealed adherence and phagocytosis of BCG by the T24 human bladder carcinoma cell line in vitro. Time sequence studies on the phagocytosis and fate of BCG showed that T24 cells are capable of progressively degrading the mycobacteria in phagolysosomes. However, BCG did not alter MHC class II antigen expression on T24 cells in vitro. In contrast, 54 urine sediments and bladder washings of 11 bladder cancer patients, taken prior to or after several intravesical BCG instillations, failed to demonstrate urothelial (tumor) cells showing evidence of BCG phagocytosis (682 cells screened by TEM), while BCG was phagocytized avidly by leukocytes. These data suggest that a direct interaction of BCG with urothelial bladder cells in vivo can be called in question.

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During a recent disease outbreak among harbour seals (Phoca vitulina) in the North and Baltic seas, more than 17,000 animals have died. The clinical symptoms and pathological findings were similar to those of distemper in dogs. Based on a seroepizootiological study, using a canine distemper virus (CDV) neutralization assay, it was shown that CDV or a closely related morbillivirus (phocid distemper virus-PDV) was the primary cause of the disease. The virus was isolated in cell culture from the organs of dead seals and characterized as a morbillivirus by serology (immunofluorescence neutralization and enzyme-linked immunosorbent assays) and by negative contrast electron microscopy. Experimental infection of SPF dogs resulted in the development of mild clinical signs of distemper and CDV-neutralizing antibodies. The disease was reproduced in seals by experimental inoculation of organ material from animals that had died during the outbreak. However, seals that had been vaccinated with experimental inactivated CDV vaccines were protected against this challenge. This fulfilled the last of Koch's postulates, confirming that the morbillivirus isolated from the seal organs, was the primary cause of the disease outbreak. The recent demonstration of the presence of a similar virus in Lake Baikal seals (Phoca sibirica), which infected these Siberian seals 1 year before the northwestern European seals were infected, raises new questions about the origin of this infectious disease in pinnipeds.

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Recently morbilliviruses were isolated from harbour seals (Phoca vitulina) in North West Europe (phocid distemper virus-1: PDV-1) and from Baikal seals (Phoca sibirica) in Siberia (phocid distemper virus-2: PDV-2) during outbreaks of severe disease which resembled distemper in dogs. PDV-1 and PDV-2 were passaged in SPF dogs, in which they caused distemper-like disease symptoms, and were subsequently passaged in Vero cells in which they caused cytopathic changes. PDV-1, PDV-2, and canine distemper virus (CDV) were compared with respect to their biological, morphological, physical, protein chemical, and antigenic properties. It was concluded that PDV-1 should be considered a newly recognized member of the genus Morbillivirus, whereas PDV-2 proved to be quite similar if not identical to CDV.

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The parallel application of two electron microscopic immunogold labeling procedures was used to assess the surface exposure and accessibility of gonococcal and meningococcal surface antigens. Monoclonal antibodies were used as markers for the surface antigens, i.e., outer membrane proteins and lipooligosaccharides. To evaluate the labeling densities obtained after incubation of whole bacteria in suspension or ultrathin cryosections of bacteria, a method of electron microscopic quantitation was developed. Incubation of whole bacterial suspensions with monoclonal antibodies and protein A-gold resulted in specific labeling of the bacterial surfaces. However, the labeling densities varied largely in each cell. By contrast, cryosections showed uniform heavy labeling densities at the surface of the outer membranes of all cells. Apparently, by sectioning the cells the antigen-masking barrier could be evaded, and steric hindrance was no longer restrictive. Thus, a better estimate of both the presence and the surface exposure, i.e., the accessibility of antigens, could be made. Such information is essential for us to better understand host-bacterial interactions and to develop new vaccines.

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A scanning electron microscopic study was carried out to compare the in vivo pathogenicity of two strains of Vibrio cholerae in an adult rabbit ligated-gut test model. V. cholerae C5 (serotype Ogawa, biotype El Tor), a motile strain possessing hemagglutinating activity in vitro, and C21 (serotype Ogawa, classical biotype), a nonmotile strain possessing no hemagglutinating activity, were tested. Tissue samples from small intestinal loops were examined 3, 6, 9, and 12 h postinoculation. Contradictory to most published data, neither hemagglutinating activity nor motility appeared to be essential prerequisites for the pathogenesis of cholera in the experimental animal model used: nonmotile hemagglutinin-negative strain C21 adhered to and colonized the small intestine at least to the same extent as did motile hemagglutinin-positive strain C5. Maximum colonization was seen at 9 h postinoculation for both strains. C5 and C21 vibrios caused comparable damage to the villi of the small intestine. The villous epithelium showed only mild changes during the first 9 h postinoculation. However, after 12 h the epithelium was seriously damaged concomitant with a decrease in the number of vibrios. Many villi showed partial or total denudation, owing to repelled epithelium, leaving a bare basal lamina with only some to moderate numbers of vibrios attached. Since similar changes were induced by pure cholera enterotoxin, these changes were likely the result of excessive fluid accumulation. From this study it is concluded that, at least in the animal model used, factors other than hemagglutinating activity and motility may also play a role in the association of V. cholerae with the small intestinal surface.

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The frequency of precursor cells capable of giving rise to cells with characteristics of mucosal mast cells in tissues from thymus-bearing and non-thymus-bearing (nude) mice orally infected with Trichinella spiralis was determined with an in vitro assay. Analysis of the frequency of mast cell precursors in bone marrow, blood, spleen and small intestinal tissue revealed similar frequencies of mast cell precursors in bone marrow from both thymus-bearing and athymic mice. These frequencies in bone marrow were not affected by infection. However, in blood and spleen from thymus-bearing mice at Day 7 post-infection (p.i.), and in the gut at Day 14 p.i., significant increases of mast cell precursor frequencies were detected. In contrast, no significant increase was observed in the tissues of infected nude mice. These data are in accordance with in vivo findings, indicating that a mucosal mast cell response in the gut is both thymus and antigen dependent. It was concluded that a mucosal mast cell response to infection with T. spiralis is probably due to local proliferation and maturation of residing mast cell precursors, that this response might be amplified by an influx of precursor cells from the blood into the gut, and that both phenomena are T-cell dependent.

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Immuno affinity chromatography with virus neutralizing monoclonal antibodies, directed to the haemagglutinating protein of canine parvovirus (CPV) was used to purify and concentrate CPV from infected cell culture. The procedure was monitored by testing the respective fractions in an infectivity titration system, in an ELISA, in a haemagglutination assay and by negative contrast electron microscopy to quantify CPV or CPV antigen. The degree of purification was further estimated by testing the fractions for total protein content in a colorimetric method, for bovine serum albumin content in an ELISA and by SDS-PAGE. Over 99% of the contaminating proteins proved to be removed, and 20% or 70-90% of infectious CPV or CPV antigen, respectively, was recovered.

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The histology of immunologically mediated tumor regression was studied in the syngenic strain 2 guinea pig/line 10 hepatocellular carcinoma tumor system. Tumor regression was induced non-specifically by the intralesional injection of living Bacillus Calmette-Guérin (BCG) in 7-day-old established tumors (diameter 8-10 mm). In untreated line 10 tumors at day 7 a mild to moderate inflammatory reaction was present, which consisted mainly of small mononuclear cells; in addition large mononuclear cells and basophils were present. Intratumoral BCG-treatment induced a prominent increase in the inflammatory reaction due to an influx of small and large mononuclear cells and neutrophils. Small mononuclear cells were identified mainly as lymphocytes whereas large mononuclear cells belonged mainly to the macrophage line. Intratumoral administration of BCG resulted in a granulomatous reaction. A time-related decrease in the number of tumor cells and an increase in inflammation, associated with purulent lysis of the granulomatous tissue, was observed. Specific immune-mediated tumor rejection occurred in animals both after active immunization and after adoptive transfer of immune spleen cells. In actively immunized animals the tumor cells were rapidly rejected and from day 4 onwards no tumor cells could be detected at the injection site. Lymphocytes were the major component of the inflammatory reaction; large mononuclear cells were present to a lesser extent and basophilic granulocytes were regularly observed. After adoptive transfer of immunity with immune spleen cells given simultaneously with an intradermal innoculation of tumor cells, an essentially similar rejection reaction was found, although tumor cell rejection was delayed. Lymphocytes and large mononuclear cells were found in equal proportions, whereas basophilic granulocytes were always present in smaller numbers. After BCG-induced regression and in adoptively transferred immune rejection, a fibroblast component was more prominent than in untreated control tumors. This reaction tended to isolate smaller tumor cell areas into islets of decreasing sizes. In contrast with the fibroblast component of growing tumors, the proliferative pre-existing fibrous tissue in tumors undergoing regression or rejection showed a loosely arranged architecture and contained a marked cellular infiltrate. From the results of the present study it was concluded that the morphological expression of line 10 tumor rejection varies. Without immune cells, BCG is needed for the induction of a local inflammatory reaction, which was granulomatous in type and eventually led to complete tumor cell eradication.(ABSTRACT TRUNCATED AT 400 WORDS)

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This report describes the first isolation and partial characterization of a herpesvirus from the harbor seal (Phoca vitulina). The virus was isolated during a disease outbreak in a group of young seals nursed in a seal orphanage in The Netherlands. Almost half of the seals died with symptoms of acute pneumonia and focal hepatitis and the virus was isolated of organs of most of the dead animals. Seven out of ten seals of which paired serum samples were obtained showed seroconversion in a virus neutralization test during this outbreak. The virus was tentatively characterized as a herpesvirus (seal herpesvirus: SeHV or phocid herpesvirus 1) on the basis of its characteristic morphology in electron microscopy, buoyant density in sucrose, sensitivity to ether and heat treatment and its antigenic relationship with other probable members of the Alphaherpesvirinae subfamily. The virus caused cytopathic changes within 24 hours after inoculation in seal kidney cells, consisting of a focal rounding of cells and syncytium formation. No cytopathic changes were observed in the cells of nine other mammalian species tested.

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The origin, kinetics and role of eosinophilic granulocytes in immune defense and inflammatory response in parasitism are reviewed. Particular attention was paid to the toxic action of eosinophilic granulocytes on parasites and the biochemical reactions which are of importance in these cases. Reference was also made to the regulatory role of eosinophilic granulocytes in inflammatory reactions, particularly in regard to mast cells. It was concluded that (1) several new insights into the role of eosinophilic granulocytes were gained in recent years, (2) that these cells can at any rate be said to have a dual function (viz. a directly parasitotoxic and regulatory role) and (3) a definite statement regarding the role of eosinophilic granulocytes in helminthic infections cannot so far be made.

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The capacity of non-infected rat total, eosinophil-enriched and eosinophil-depleted fractions of peritoneal exudate and bone marrow cells to adhere to and kill Trichinella spiralis newborn larvae with immune rat serum has been studied in vitro. The eosinophil-depleted peritoneal exudate cell fraction contained mainly mononuclear cells, whereas the corresponding bone marrow cell fraction consisted of a considerable number of neutrophils. All cell types either originating from the peritoneal cavity or the bone marrow, showed adherence and killing properties to the Trichinella newborn larvae. It was concluded that mononuclear cells and neutrophils are capable of and more effective than eosinophils in stage-specific killing of Trichinella in vitro.

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Virus-like particles were identified from the plasma of rabbits which developed pleural effusion disease after inoculation with different strains of Treponema pallidum. These particles were considered coronavirus-like on the basis of their size, morphology, and buoyant density. Clinical and pathological manifestations of pleural effusion disease, which is probably the same disease entity as rabbit cardiomyopathy, resembled those of feline infectious peritonitis which is caused by another probable member of the Coronaviridae family. Coronavirus-like particles also were demonstrated in the feces of rabbits which had been inoculated with a 450-nm fecal filtrate of rabbits which died from infectious intestinal disease.

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Cows of the Dutch Frisian and Maas-Rijn-IJssel breed with histologically confirmed ocular squamous cell carcinoma showed complete regression of the primary tumor in 70 or 60% of the cases after intralesional injection of a BCG cell wall or live BCG vaccine, respectively. Recurrence of the tumor was observed in 57% of the animals treated with BCG cell walls and in 25% of the animals treated with live BCG vaccine. Spontaneous regression was seen in 20% of the untreated cows. In a second control group, radical surgery, the most successful treatment for primary stage I tumors in humans, resulted in a 90% cure. Influence of immunotherapy on metastases could not yet be fully evaluated. White blood cell counts were not changed after therapy. It was not possible to link a favorable response to BCG therapy with the intensity of the delayed type hypersensitivity (DTH) reaction to purified protein derivative of mycobacteriae (PPD) or the formation of antibodies to BCG as determined by a micro-enzyme-linked immunosorbent assay. However, in animals that showed tumor regression, the DTH reaction to PPD had a tendency to persist for a longer period of time. It was concluded that 1) block resection was the best method of treatment for this tumor, 2) a single intralesional injection of a BCG cell wall vaccine was as effective as live BCG vaccine in the induction of complete regression of the primary tumor, 3) in this preliminary study BCG cell wall vaccine was less effective than live BCG vaccine in the prevention of recurrence, and 4) this naturally occurring tumor model is well suited for the study of the influence of BCG immunotherapy in a primary stage I tumor.

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Two independent outbreaks of ectromelia in mice occurred in The Netherlands. In both cases, the causative virus was isolated and identified as ectromelia virus on the basis of serology, demonstration of antigen by indirect immunofluorescence, negative contrast electron microscopy, morphology of lesions on chorioallantoic membranes of embryonated chicken eggs, and cytopathogenicity for mouse cells. Inoculation of the virus into the dermis of rabbits demonstrated a low virulence for this species.

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