Flow cytometric detection of DNA tumor virus nuclear oncogene products in unfixed cells: saponin FACS of viral oncogene products

Immunofluorescent analysis is a standard method for detecting DNA virus oncoproteins in transformed cells. Here we demonstrate the detection of DNA virus nuclear oncoproteins by flow cytometry of unfixed cells, after saponin permeabilization. This method could to be of value in the evaluation and quantitation of oncogene products in transformed cells.

Driving adenovirus type 12-transformed BALB/c mouse cells to express high levels of class I major histocompatibility complex proteins enhances, rather than abrogates, their tumorigenicity

The tumorigenicity of adenovirus type 12 (Ad12)-transformed cells has been attributed to the low levels of class I major histocompatibility complex (MHC) protein expression by these cells. These levels of class I proteins are thought to be below the threshold critical for cytotoxic T-lymphocyte recognition, a process that may be involved in tumor cell immunosurveillance. We have used gene transfer experiments to investigate the role played by class I protein expression in the tumorigenicity of Ad12-transformed BALB/c mouse cells in naive, syngeneic adult mice. Our Ad12-transformed mouse cells were tumorigenic in adult mice and were similar to other Ad12-transformed mammalian cells in that they expressed low levels of class I MHC mRNA and cell surface proteins. Despite these low levels of expression, the cells were highly immunogenic in syngeneic mice and were rejected as allografts by allogeneic mice. Transfection of genomic H-2Dd or H-2Ld fragments into these cells produced a variety of cell clones that expressed increased levels of cell surface class I proteins. These cells expressing high levels of class I protein were up to 16-fold more tumorigenic than the parental cells in syngeneic adult mice. Thus, by quantitative assays, the tumorigenicity of Ad12-transformed BALB/c mouse cells is not functionally related to the low levels of class I MHC proteins they express. The increased tumorigenicity expressed by H-2Dd- and H-2Ld-transfected cells was not detected in BALB/c nu/nu mice, suggesting that a thymus-dependent mechanism that is not mediated by evasion of cytotoxic T-lymphocyte recognition could contribute to the difference in tumorigenicity of Ad12-transformed BALB/c mouse cells that express low and high levels of class I MHC proteins.

Characterization of glutamine uptake in mouse two-cell embryos and blastocysts

Mouse two-cell embryos and blastocysts take up [3H]glutamine in vitro at a constant rate for at least 15 min, depending on the concentration of glutamine and developmental stage of the embryo. Uptake by two-cell embryos can be resolved into two saturable components. The major contributing system is Na+ independent, inhibited by alanine, methionine, 2-amino-2-norbornanecarboxylic acid (BCH) or leucine and has a Km of 3856 +/- 672 mumols l-1 and Vmax of 436 +/- 58 fmol per embryo per 10 min. These features are characteristics of the ubiquitous system L transporter. The second component is Na+ dependent with Km of 1064 +/- 914 mumols l-1 and Vmax 107 +/- 47 fmol per embryo per 10 min. Similar Vmax and inhibition of this component by glycine suggest a low reactivity with the gly-system. Blastocyst uptake of glutamine is mainly by a Na(+)-dependent saturable mechanism with Km of 524 +/- 75 mumols l-1 and Vmax of 1264 +/- 101 fmol per embryo per 10 min which is inhibited by alanine, isoleucine, leucine and BCH, features characteristic of the system B0,+. The increase in uptake capacity as a consequence of the appearance of the system B0,+ may be related to increased metabolic requirements for glutamine, in the rapidly expanding blastocyst.

Stimulation of protein synthesis and expansion of pig blastocysts by insulin in vitro

Present evidence indicates that insulin may act as a growth factor during preimplantation development. This hypothesis has been tested on pig blastocysts by determining the effect of insulin on protein synthesis and blastocyst expansion over 24 h. Blastocysts were collected from superovulated gilts or sows on Day 5 or 6 and incubated overnight in a modified BMOC2 medium. Those that were cultured with 1.7 nM insulin had 14% larger radii, and were 36% more active in their incorporation of [3H]leucine (protein synthesis) than those that had been cultured in non-supplemented medium. There was a significant linear correlation between the rate of protein synthesis and the radius of blastocysts when all blastocysts and only those cultured with insulin were examined, but the correlation for the blastocysts in non-supplemented medium was just outside statistical significance. The regression coefficient for the insulin-treated blastocysts was 132% of that for blastocysts cultured in unsupplemented medium; this suggests that insulin increased the size of blastocysts and the rate of protein synthesis per unit size. The results indicate that pig blastocysts respond to physiological levels of insulin in similar fashion to those of mice and cattle, supporting the hypothesis that insulin may act as a general embryonic growth factor. Because of the cross reaction between the insulin receptor and the ligands, insulin and insulin-like growth factor 1 (IGF-1), the results also suggest that IGF-1, reported to be present in pig uterine fluid, could be involved in this stimulation in utero.

E1A oncogene induction of cytolytic susceptibility eliminates sarcoma cell tumorigenicity

The manner in which oncogenes influence tumorigenicity beyond their ability to immortalize cells is uncertain. We tested the hypothesis that, in addition to subverting cellular growth controls, oncogenes can actively determine tumor-inducing capacity by affecting neoplastic cell susceptibility to destruction by the host cellular immune response. The adenovirus type 5 E1A oncogene, which induces susceptibility to lysis by natural killer cells and encodes epitopes recognized by cytotoxic T lymphocytes, was transfected into highly tumorigenic sarcoma cells. E1A expression in these sarcoma cells eliminated their tumorigenicity in recipients with natural killer cell activity that was competent to lyse these E1A-positive targets. Thymus-dependent responses were not required for tumor rejection. These results indicate that oncogene-regulated cellular pathways that affect neoplastic cell susceptibility to natural killer cell lytic mechanisms may influence tumor development in the immunocompetent host.

Syrian hamsters express diverse MHC class I gene products

MHC class I glycoproteins are highly diverse in most species. The Syrian hamster has long been thought to express monomorphic MHC class I molecules and thus be an exception to this rule. Here we show that Syrian hamsters express diverse MHC class I gene products. The nucleotide sequences of the alpha 1 and alpha-2 domains of classical Syrian hamster MHC class I molecules are highly variable and show evidence of having been under selective pressures at their Ag recognition sites. Interestingly, none of the Syrian hamster class I genes was closely related to their counterparts in the mouse. These observations suggest that Syrian hamsters in the wild may express diverse MHC class I molecules.

Syrian hamsters express diverse MHC class I gene products

MHC class I glycoproteins are highly diverse in most species. The Syrian hamster has long been thought to express monomorphic MHC class I molecules and thus be an exception to this rule. Here we show that Syrian hamsters express diverse MHC class I gene products. The nucleotide sequences of the alpha 1 and alpha-2 domains of classical Syrian hamster MHC class I molecules are highly variable and show evidence of having been under selective pressures at their Ag recognition sites. Interestingly, none of the Syrian hamster class I genes was closely related to their counterparts in the mouse. These observations suggest that Syrian hamsters in the wild may express diverse MHC class I molecules.

Expression of human immunodeficiency virus long terminal repeat in the human promonocyte cell line U937: effect of endotoxin and cytokines

Phagocytic macrophages are known to support noncytopathic, chronic infections of human immunodeficiency virus (HIV). Regulation of viral replication in such cells with either chronic low-grade or latent HIV infection is probably influenced by both viral and cellular factors acting on the viral long terminal repeat (LTR). This study identifies naturally occurring biological response modifiers which are able to affect the HIV-LTR linked to the chloramphenicol acetyl transferase (LTR-CAT) gene in a stable transfection of the human promonocyte cell line, U937, in the absence of other viral proteins. In this model system, endotoxin lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNF-alpha) are able to independently stimulate expression of LTR-CAT. Granulocyte/macrophage-colony-stimulating factor can enhance the effect of TNF-alpha or LPS, but other cytokines tested had minimal or no effect on LTR-CAT. In addition to effects on cellular susceptibility and immune function, the ability of naturally occurring factors to affect HIV-LTR in its integrated state may have particular relevance to progression of active disease from latent infection.

Biochemical properties of media conditioned by simian virus 40-induced hamster tumor cells: correlation with distinct cell phenotypes but not with oncogenicity

Hamster cells, transformed in vitro by SV40, have been reported to secrete an unidentified factor(s) that inhibits thymidine uptake (TU) by various normal cell types, including activated lymphocytes. It has been postulated that this apparent antiproliferative effect may play an in vivo role in the high tumorigenic capacity of SV40-transformed hamster cells. In keeping with this hypothesis, Adenovirus type 2-transformed hamster cells, which are only weakly tumorigenic, do not inhibit TU by indicator cells in vitro. To study the biological relevance of this phenomenon, we assayed 11 cell lines derived from different fibrosarcomas, induced in Syrian hamsters by SV40, for their ability to inhibit TU by normal rabbit kidney indicator cells. In contrast to cells transformed in vitro by SV40, media conditioned by 6 of 11 tumor-derived cell lines did not inhibit TU. Our results do not support the hypothesis that an antiproliferative factor secreted by SV40-transformed cells promotes the tumor-inducing capacity of these cells. Furthermore, inhibition of TU does not appear to be due to the production of a specific antimitotic peptide, but rather to other biochemical properties of the media conditioned by transformed cells. Finally, these biochemical properties do appear to correlate with specific morphological and growth characteristics of the tumor cells, but probably as an effect and not a cause.

Characterization of hamster tumors induced by simian virus 40 small t deletion mutants as true histiocytic lymphomas

Random bred Syrian hamsters given s.c. injections of SV40 small t deletion mutants dl883, dl884, and dl890 rapidly develop reticulum cell sarcomas in the abdominal cavity in addition to slowly developing s.c. fibrosarcomas at the site of virus inoculation. Injection of wild type SV40 s.c. induces only fibrosarcomas at the site of inoculation. In an attempt to understand why mutations in the SV40 small t gene should lead to this difference in tumor-inducing capacity in hamsters, we studied cells from 12 abdominal reticulum cell sarcomas which were induced by the s.c. injection of SV40 mutants. Morphological and functional analyses indicate that these tumor cells are derived from MAC-2+ macrophages. They are highly granulated, vacuolated, and multinucleated, and they generally adhere to glass and plastic. In addition, they (a) phagocytose latex beads; (b) express high levels of class II major histocompatibility complex antigens; (c) contain beta-glucuronidase, acid phosphatase, and fluoride-inhibited nonspecific esterase; (d) contain lysozyme and fibronectin; and (e) express cell surface MAC-2 antigens. Thus, the small t deletions in the SV40 genome appear to permit the virus to transform cells that are distant from the site of virus inoculation; at this distant site, the cells transformed are of a specific lineage, MAC-2+ peritoneal macrophages. This specific tropism may reflect a unique characteristic of MAC-2+ cells or their precursors that renders these cells susceptible to SV40 mutants which are otherwise restricted in the range of cells that they can transform.

A hospital outbreak of Serratia marcescens in neurosurgical patients

We report an outbreak of serious infections with Serratia marcescens in patients on a neurosurgery ward. The epidemiological investigations undertaken are described. Features of outbreaks of infection with serratia and control measures are discussed.

Viral gene inhibition of class I major histocompatibility antigen expression: not a general mechanism governing the tumorigenicity of adenovirus type 2-, adenovirus type 12-, and simian virus 40-transformed Syrian hamster cells

The association between the level of class I major histocompatibility (MHC) antigen expression and the tumorigenic phenotype was determined for cells from a series of 15 lines of adenovirus type 2 (Ad2)-, Ad12-, and simian virus 40 (SV40)-transformed hamster cells and 16 lines of cells established from hamster tumors induced by SV40 mutants. These cells range from nontumorigenic to highly tumorigenic in both syngeneic and allogeneic adult hamsters. The Ad2-transformed cells--cells that were nontumorigenic in syngeneic adult hamsters--expressed either high levels or low levels of class I MHC antigens. The SV40-transformed cells--cells transformed in vitro that produced tumors with equal efficiency in both syngeneic and allogeneic adult hamsters--or cells derived from SV40-induced tumors expressed very high levels of class I MHC antigens. The Ad12-transformed cells uniformly expressed low levels of class I MHC antigens; these cells produced tumors 200- to 1,000-fold less efficiently in allogeneic adult hamsters than in syngeneic adult hamsters and produced tumors with about the same efficiency in immunoimmature newborns and immunocompetent syngeneic adult hamsters. We conclude that the expression of either high levels or low levels of class I MHC antigens is, at most, a minor factor in the differences observed among these adenovirus- and SV40-transformed cells in their tumor-inducing capacity in naive, immunocompetent hamsters.

A test of the air-seeding hypothesis using sphagnum hyalocysts

"Air-seeding" is a proposed mechanism for the initiation of water stress embolism in dead plant cells. During air-seeding, external air is drawn into the lumen of a dead plant cell through a pore or crack in the cell wall. The resulting bubble may expand to fill the lumen, thus embolizing the cell. The data presented confirm that Sphagnum hyalocysts can embolize by air-seeding when the pressure difference across the air-water meniscus is given by DeltaP = 0.3/D (derived from the capillary equation), where DeltaP is the pressure difference across the meniscus (megapascal), and D is the diameter (micrometer) of the pore through which the air bubble enters.

Adenovirus E1A gene induction of susceptibility to lysis by natural killer cells and activated macrophages in infected rodent cells

Rodent cells immortalized by the E1A gene of nononcogenic adenoviruses are susceptible to lysis by natural killer (NK) cells and activated macrophages. This cytolysis-susceptible phenotype may contribute to the rejection of adenovirus-transformed cells by immunocompetent animals. Such increased cytolytic susceptibility has also been observed with infected rodent cells. This infection model provided a means to study the role of E1A gene products in induction of cytolytic susceptibility without cell selection during transformation. Deletion mutations outside of the E1A gene had no effect on adenovirus type 2 (Ad2) or Ad5 induction of cytolytic susceptibility in infected hamster cells, while E1A-minus mutant viruses could not induce this phenotype. E1A mutant viruses that induced expression of either E1A 12S or 13S mRNA in infected cells were competent to induce cytolytic susceptibility. Furthermore, there was a correlation between the accumulation of E1A gene products in Ad5-infected cells and the level of susceptibility of such target cells to lysis by NK cells. The results of coinfection studies indicated that the E1A gene products of highly oncogenic Ad12 could not complement the lack of induction of cytolytic susceptibility by E1A-minus Ad5 virus in infected cells and also could not block induction of this infected-cell phenotype by Ad5. These data suggest that expression of the E1A gene of nononcogenic adenoviruses may cause the elimination of infected cells by the immunologically nonspecific host inflammatory cell response prior to cellular transformation. The lack of induction of this cytolysis-susceptible phenotype by Ad12 E1A may result in an increased persistence of Ad12-infected cells in vivo and may lead to an increased Ad12-transformed cell burden for the host.

Immunological surveillance against DNA-virus-transformed cells: correlations between natural killer cell cytolytic competence and tumor susceptibility of athymic rodents

Adenovirus type 2 (Ad2)-transformed hamster and rat cells are susceptible to lysis by natural killer (NK) cells from the host of origin and are nontumorigenic in immunocompetent hamsters and rats, respectively. These NK-cell-susceptible, virus-transformed cells are, however, highly tumorigenic in athymic (nude) mice--animals with intact NK-cell responses. In vitro lysis of these xenogeneic, Ad2-transformed cells by nude-mouse NK cells was found to be defective. In contrast, Ad2-transformed hamster and rat cells were highly susceptible to lysis by nude-rat NK cells. Furthermore, xenogeneic, Ad2-transformed hamster cells were nontumorigenic in nude rats unless the NK-cell responses of the challenged animals were compromised. The results of the nude-rat studies show that thymus-dependent, cytotoxic T-lymphocyte-mediated, host cellular immune responses are not essential for rejection of xenogeneic cells transformed by nononcogenic Ad2. The data suggest instead that immunologically nonspecific host cellular immune responses, such as those mediated by NK cells, are sufficient for rejection of Ad2-transformed cells. These results indicate that biologically important differences exist in the NK-cell-mediated defenses mounted by nude mice and nude rats against transformed cells that may account for the different patterns of tumor induction by various neoplastic cell types in these athymic animals.

Tumorigenicity of hamster and mouse cells transformed by adenovirus types 2 and 5 is not influenced by the level of class I major histocompatibility antigens expressed on the cells

Inbred hamster and mouse cells transformed by the nononcogenic adenovirus (Ad) serotypes, Ad2 and Ad5, are nontumorigenic in syngeneic adult animals, while cells from these species transformed by the highly oncogenic Ad12 are tumorigenic in such rodents. By immunoprecipitation and flow cytometry, cells from four of six Ad2- and Ad5-transformed hamster and mouse lines expressed high levels of cell-surface class I major histocompatibility complex (MHC) antigens, while cells from two of these six lines expressed low levels of cell-surface class I MHC antigens. The levels of class I MHC proteins expressed by cells from these latter two lines were comparable to the levels of cell-surface class I MHC proteins expressed by cells from Ad12-transformed hamster and mouse lines. Moreover, an Ad2-transformed line that had become highly oncogenic after in vivo adaptation showed the same high level of MHC expression as the nononcogenic parent. The amounts of class I mRNA, analyzed by RNA blotting, were, in general, consistent with the levels of class I antigens expressed on the surfaces of these cells. These results indicate that there is no correlation between the tumorigenicity in immunocompetent syngeneic adult rodents of Ad2- and Ad5-transformed hamster and mouse cells and the level of class I MHC antigens expressed on the surfaces of these cells. Thus, the expression of different levels of class I MHC proteins does not seem to explain the differences in the oncogenicity between nononcogenic and highly oncogenic human Ad serotypes.

Faecal carriage rate of Yersinia species

A total of 1,203 unselected routine faecal samples from 1,006 patients were cultured for Yersinia species by a cold enrichment technique. Seventy-five specimens (6.1%) from 63 patients were culture-positive for Yersinia spp. Fifty-two were Yersinia enterocolitica, 22 Yersinia frederiksenii and 1 Yersinia intermedia. The predominant Y. enterocolitica isolates belonged to biotype 1 - serotype 0:6, 30 or serotype 0:5, 27. Y. frederiksenii strains were non-typable. Forty isolates were recovered from 33 patients with gastroenteritis. During the study period 83 Salmonella spp. from 33 patients, 17 Shigella sonnei from 13 patients and 13 Campylobacter jejuni from 12 patients were cultured. Yersinia spp. was isolated in association with salmonella on three occasions, twice with rotavirus and once each with Shigella sonnei, Campylobacter jejuni and Trichuris trichiura.

Expression of the adenovirus E1A oncogene during cell transformation is sufficient to induce susceptibility to lysis by host inflammatory cells

Mammalian cells transformed by nononcogenic human adenoviruses exhibit high susceptibility to destruction by host mononuclear inflammatory cells. We have analyzed the viral gene regulation of the susceptibility of transformed cells to lysis by natural killer cells and activated macrophages. Comparisons of target cell lines transformed by overlapping segments of the adenovirus E1-transforming gene region revealed that isolated expression of a single oncogene, E1A, was sufficient to cause increased cytolytic susceptibility in the absence of detectable transformed cell-surface expression of viral transplantation antigens and irrespective of histocompatibility antigen identity between killer cells and target cells. These results suggest that oncogene functions that are not linked to the expression of previously recognized cell-surface target structures may actively induce neoplastic cell elimination by components of the host immune surveillance system.

The level of expression of adenovirus type 2 transforming genes governs sensitivity to nonspecific immune cytolysis and other phenotypic properties of adenovirus 2-simian virus 40-transformed cell hybrids

Syrian hamster embryo cells transformed by adenovirus type 2 (Ad2) or simian virus 40 (SV40) differ markedly in morphology, tumorigenicity, and susceptibility to in vitro lysis by nonspecific cytotoxic cells. Hybrid cells formed by fusing Ad2- and SV40-transformed Syrian hamster embryo cells may express only SV40 T antigens or both SV40 and Ad2 T antigens. Hybrids that express only SV40 T antigens are indistinguishable from the nonhybrid SV40-transformed phenotype, whereas hybrid cells that express T antigens from both viruses closely resemble the nonhybrid parental Ad2-transformed phenotype. Because these hybrid cells have been useful in the study of neoplastic transformation, we determined the amount of viral antigens that they accumulate in an attempt to correlate the level of expression of the transforming viral genes with some of their phenotypic properties. Hybrid cells that expressed proteins from both viruses showed reduced levels of SV40 T antigens compared with those of hybrid cells that did not express Ad2 T antigens. We also found that the production of several cellular proteins that influence cytomorphology was inhibited in hybrid and nonhybrid cells that expressed Ad2 T antigens, and the repression of these cellular proteins correlated with a change in cytomorphology from fibroblastic to spherical. Finally, we showed that the susceptibility of our hybrid cells to in vitro lysis by natural killer cells and activated macrophages, two putative host-effector cells involved in defense against neoplasia, correlated closely with the level of expression of a 58,000-dalton Ad2 protein. The results reported here, together with the results of previous studies, indicate that the oncogenic potential of hybrid cells that express both Ad2 and SV40 antigens is extremely sensitive to Ad2 expression, whereas other phenotypic properties depend on Ad2 expression in a dose-dependent manner.

A new role for DNA virus early proteins in viral carcinogenesis

The T antigen proteins encoded by DNA tumor virus early genes are involved in the transformation of normal cells to immortalized neoplastic cells that may or may not be tumorigenic in immunocompetent animals. Studies have been made of the tumorigenicity of DNA virus-transformed cells and the interactions of these cells in vivo and in vitro with immunologically nonspecific host effector cells such as natural killer cells and macrophages. The results imply that the T proteins determine the capacity of transformed cells to induce tumors by governing the level of susceptibility that transformed cells express to destruction by such host cellular defenses.

Extrinsic duodenal obstruction by congenital bands in an adult patient

An adult patient with congenital malrotation of the gut, presenting as duodenal obstruction is reported.