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Biomedical subjects

E Skaletsky

Publications and source records attributed to E Skaletsky.

17 recordsLinked to original sources
PubMed1995

Antibody humanization predicted by computer graphic analysis.

Humanized antibodies continue to be evaluated in clinical trials, and each trial will yield valuable information for the design of the next generation of humanized antibodies. More attention will be given to the use of antibody fragments and the selection of human antibody specificities from phage libraries for human antibody therapeutics. Computer graphic analysis and molecular modeling of antibody structures will continue to be invaluable for predicting structural modifications for humanization of antibodies and for extracting structural information from antigen binding sites that can ultimately lead to small molecule therapeutics.

Animals↗
PubMed1993

Accessing three-dimensional chemical information in antibody molecules.

Important structural information can be obtained from monoclonal antibodies through X-ray crystallographic analysis and computer modeling of CDR loops. These applications of monoclonal antibody technology offer new insights and novel approaches to the modification of antibody molecules for disease treatment, diagnosis, and drug design.

Antibodies, Monoclonal↗
PubMed1992

Immunization of cats against feline infectious peritonitis with anti-idiotypic antibodies.

Anti-idiotypic antibodies (Ab2s) generated against neutralizing antibodies (Ab1s) specific for feline infectious peritonitis virus (FIPV) were shown to be specific for paratope-associated idiotopes of the Ab1s and not against isotypic determinants. In a study to determine the efficacy of an anti-idiotypic vaccine against feline infectious peritonitis (FIP), cats that were immunized with a pool of monoclonal Ab2s developed Ab3s that recognized the variable regions of the Ab2s as well as the natural antigen. In cats challenged with a lethal dose of virus the control group followed a predictable course of infection ultimately succumbing to FIP. Two immunized cats survived virus challenge and a third cat lived twice as long as the controls. The fourth immunized cat showed no evidence of protection. The ability to induce levels of protection against FIP lends support to the concept of using anti-idiotypic antibodies as a prophylactic vaccine.

Animals↗
PubMed1991

Characterization of crystals of an intact monoclonal antibody for canine lymphoma.

A monoclonal antibody of the subclass IgG2a specific for canine lymphoma cells has been crystallized by vapor diffusion from polyethylene glycol 8000. the crystals, which occasionally measure nearly a millimeter on edge, have been examined by X-ray diffraction. The crystals are of triclinic space group P1 with unit cell parameters of a = 66.39 A, b = 77.34 A, c = 101.42 A, alpha = 87.60 degrees, beta = 92.55 degrees, gamma = 97.54 degrees and cell volume of V = 4.84 x 10(5) A3. There is one entire antibody molecule as the asymmetric unit of the crystals. Three-dimensional X-ray diffraction data have been collected to 2.8 A resolution and a self rotation function calculation shows a pronounced peak indicating at least an approximate non-crystallographic dyad axis.

Animals↗
PubMed1988

A human monoclonal antibody to cytokeratin intermediate filament antigens derived from a tumor draining lymph node.

Human lymphocytes derived from a lymph node draining a primary breast adenocarcinoma were fused with the mouse myeloma P3X63Ag8.653 to generate human-mouse hybridomas secreting human monoclonal antibodies (MAbs) to tumor associated antigens (TAAs). One of the resulting human MAbs, YBB 190 (IgM) is described. Enzyme-linked immunosorbent assays (ELISA) employing membrane and cytosol fractions of human tissues demonstrated YBB 190 reactivity against cytosol but not membrane components of malignant and normal epithelial tissues. When tested by an indirect immunoperoxidase staining method against fresh frozen human tissue sections, YBB 190 reacted with malignant cells in 26 of 28 epithelial cancers and with normal epithelia in 11 different benign tissues. Preliminary western blot antigen characterization indicated that YBB 190 recognizes cytokeratin intermediate filaments, or a protein that is closely associated with cytokeratins. These data indicate that B cells with specificity for intermediate filaments are present in tumor draining lymph nodes. Our findings provide insights into the nature of potential autoimmune responses in cancer patients and suggest that improved tumor directed sensitization procedures may be required to more effectively utilize lymphocytes from tumor draining lymph nodes to generate therapeutically useful human MAbs to TAAs.

Adenocarcinoma↗
PubMed1987

Growth of malignant rabbit fibroma virus in lymphoid cells.

To understand better the immunosuppressive capacity of malignant rabbit fibroma virus (MV), we characterized MV growth in lymphoid cells. Replication of MV occurs in unstimulated normal spleen cells in vitro and is enhanced by adding T- or B-lymphocyte mitogens. In splenic T-lymphocyte preparations, comparable results are found: virus growth in the absence of mitogen, augmented by adding Con A. Unlike mature T cells, thymic lymphocytes support MV replication only when mitogen is added. When spleen cells from rabbits infected with MV in vivo are removed and cultured without mitogen, MV growth is again observed, with virus titer increasing about 10-fold per day of culture. In spleen cell populations from MV tumor-bearing rabbits, MV grows best in T lymphocytes, moderately in B lymphocytes, and least efficiently in adherent cells. When spleen cells are examined immediately following sacrifice, MV antigens are expressed solely on T lymphocytes from rabbits infected in vivo with MV 7 days previously. However, following overnight incubation in vitro a population of non-T lymphocytes displays cell membrane virus antigens. MV adapts itself somewhat to growth in lymphocytes, showing significantly greater growth in lymphocytes following passage in lymphocytes than is observed for non-lymphocyte-propagated virus. MV-infected lymphocytes also elaborate a factor that enhances MV growth in lymphocytes. Thus, MV replicates preferentially in mature T lymphocytes but will grow well in B cells as well. In vivo infection produces relatively small amounts of recoverable virus. However, when these lymphocytes are cultured in vitro virus replicates very well without added mitogens. These growth patterns may help to understand MV-induced immunologic dysfunction.

Animals↗
PubMed1986

Leporine acquired immune deficiency disease.

We have identified a recombinant leporipoxvirus that produces disseminated fibromas and a severe combined immune deficiency disease of sudden onset. The virus is recombinant between the SFV and the MV. MV was identified as a trace contaminant in stocks of SFV (Patuxent strain). Rabbits inoculated with the original uncloned stock of SFV prepared in vitro develop local tumors that subsequently regress. However, tumor extracts prepared from these animals, when injected into a second group of rabbits, produced MV syndrome. Rabbits with MV syndrome develop severe, usually lethal, Pasteurella or Bordetella infections and have disseminated fibroxanthosarcomas more similar to those produced by myxoma virus. The virus that induces this syndrome has been isolated by two cycles of plaque purification. This virus is indistinguishable from SFV using cross-neutralization and electron microscopy. Analyses of restriction enzyme digests of MV and plaque-purified SFV show them to be quite dissimilar and indicate that MV is recombinant between SFV and myxoma virus. This recombinational event resulted in approximately 5.5 kb of myxoma virus DNA within each of the inverted terminal repeats being replaced by a similar amount of DNA derived from the corresponding region of the SFV genome. Thus, MV contains approximately 149 kb of myxoma sequences and 11 kb of SFV sequences. Immunofluorescent studies of spleen and lymph nodes from MV-infected rabbits demonstrate that viral antigens are present predominantly in the sinusoidal lining cells in lymph nodes and in phagocytes in the splenic cords. This contrasts with the distribution of antigen observed in myxoma virus-infected rabbits where myxoma-specific antigens are present in large amounts in hyperplastic epithelium overlying tumors, particularly in the nasal mucosa and in spleen and lymph node cells. MV-infected rabbits essentially lose their lymphocyte proliferative response to T and B cell mitogens and are unable to initiate an antibody response to SRBC, as determined by a modified Jerne plaque assay. In vitro MV severely depresses the mitogen responses of normal B and T lymphocytes after two days of culture. Lymphoid cells and lysates of lymphoid cells from MV-infected rabbits will suppress mitogen- and antigen-induced responses in vitro. MV can grow in lymphocytes, but replication of MV is less efficient in lymphocytes than in RK-13 cells. Thus, MV produces a disseminated viral infection, systemic myxofibromas, and a severe combined immune deficiency in rabbits. The molecular and immunologic basis for these effects is now under study.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Inhibition of virus replication does not alter malignant rabbit fibroma virus-induced immunosuppression.

Malignant rabbit fibroma virus (MV) directly suppresses generation of antibody responses and mitogen induced T and B lymphocyte proliferation. We investigated whether this phenomenon required expression of the complete viral genome. Phosphonoacetic acid (PAA) inhibits poxvirus specific DNA polymerases. Adding PAA to cultures reduces both MV replication and mitogen-driven rabbit lymphocyte proliferation in a dose-dependent fashion. A dose of PAA adequate to inhibit MV replication by about 97%, but insufficient to reduce lymphocyte proliferation appreciably, does not affect the ability of MV to suppress lymphocyte proliferation or initiation of antibody production. Spleen cells from MV tumour-bearing rabbits contain very little virus, but inhibit the proliferative and antibody forming responses of normal spleen cells. This activity is shown here to reflect the production by T lymphocytes of a soluble mediator of greater than 25 kD molecular weight. Adding PAA to these mixed spleen cell cultures does not alter the ability of MV to induce T suppressor activity in host lymphocytes. Thus, these immunosuppressive capabilities of MV appear to reflect early MV gene functions.

Animals↗
PubMed1985

In vitro growth of two related leporipoxviruses in lymphoid cells.

We examined the in vitro growth patterns of two leporipoxviruses, malignant rabbit fibroma virus (MV) and Shope fibroma virus (SFV), in lymphoid cells. MV replicates well in normal spleen cells in vitro. At low m.o.i. (0.001), dramatic virus growth occurs in unstimulated cell cultures. This growth is enhanced by addition of the T lymphocyte mitogen, concanavilin A, or the B lymphocyte mitogen, Escherichia coli lipopolysaccharide. Shope fibroma virus does not grow in lymphocytes in culture, with or without mitogen stimulation. MV itself profoundly inhibits lymphocyte mitogenesis, while SFV does not. MV and SFV added to normal lymphocytes do not appear to alter their viability in culture. Thus, MV appears to be novel in its ability to replicate to high titer in resting lymphocytes. This growth pattern may be useful in understanding MV-induced immunologic dysfunction.

Animals↗
PubMed1984

Immunologic dysfunction during viral oncogenesis. II. Inhibition of cellular immunity to viral antigens by malignant rabbit fibroma virus.

The ability of two related viruses--Shope fibroma virus (SFV) and malignant rabbit fibroma virus (MV)--to induce virus-specific immune responses in lymphocytes of recipient animals was studied. SFV produces a benign local tumor which regresses in 12-14 days. Using an assay for virus-induced lymphocyte blastogenesis lymphocytes reactive to SFV were detected, both in rabbits bearing SFV-induced tumors and in rabbits whose SFV-induced tumor had regressed. These virus-reactive cells were detected in peripheral blood and spleen, and in lymph nodes draining the primary tumor. In contrast, MV produces a disseminated tumor and eventual death. MV does not induce detectable blastogenic responses in lymphocyte populations. SFV and MV are antigenically cross reactive: rabbits immune to SFV do not develop MV-induced tumors, and antisera to each virus neutralize both equally. Lymphocytes from SFV-infected rabbits proliferate in vitro in response to MV that has been inactivated by ultraviolet light (uv/MV) but not to infectious MV. In contrast, lymphocytes from rabbits infected with MV do not respond to uv-inactivated MV or to SFV. Thus, infectious MV inhibits the development of normal blastogenic responses in vivo and prevents the expression of those responses in lymphocytes from MV-resistant, SFV-immune rabbits in vitro. The relevance of this impairment to the differences in the clinical courses of SFV- and MV-induced tumors is discussed.

Animals↗
PubMed1984

Strain differences in Shope fibroma virus. An immunopathologic study.

The pathogenic effects of plaque-purified Boerlage and Patuxent strains of Shope fibroma virus (SFV) in neonatal rabbits are compared with results of previous reports which used nonpurified SFV. Clinically, the Boerlage strain produced large tumors; whereas the same dose of Patuxent strain SFV induced much smaller tumors locally. Neither virus caused metastatic or extensively invasive local spread in our study. Some Patuxent recipients died of respiratory infections prior to sacrifice. However, both groups of rabbits handled the tumor well; the tumor began regressing 15-20 days after inoculation. Histologically, the tumors produced by those viruses were identical. Patuxent strain recipients were otherwise normal. Boerlage strain recipients showed increased persistence of extramedullary hematopoiesis and scattered foci of parenchymal necrosis in their livers. They also showed considerable cell death in thymic lobules. In rabbits given Patuxent strain SFV, virus antigens were detected only in the tumor by immunohistologic examination. Boerlage viral antigens were found in the tumor and overlying skin. We also detected virus systemically in Boerlage recipients: it was present in fixed tissue phagocytes in the spleen and liver and also in parenchymal cells of the lungs, liver, and kidney. Boerlage strain SFV recipients also showed detectable virus in their thymus, both at the periphery of the thymic lobules and in the connective tissue separating thymic lobules from each other. Despite the disseminated nature of the infection, rabbits that received the latter strain fared as well as those receiving Patuxent strain SFV.

Animals↗
PubMed1983

Immunologic dysfunction during viral oncogenesis. I. Nonspecific immunosuppression caused by malignant rabbit fibroma virus.

Malignant rabbit fibroma virus (MV) is a potent oncogenic poxvirus that produces a rapidly progressive syndrome of disseminated myxosarcoma, immunosuppression, and fatal gram-negative infection. MV is probably a recombinant between Shope fibroma virus (SFV) and rabbit myxoma virus, and is capable of preventing or aborting the in vitro proliferative responses of rabbit lymphocytes to B and T lymphocyte mitogens. Proliferative responses to sheep erythrocytes (SRBC) are similarly affected, although MV does not alter ongoing antibody responses to SRBC. Splenic lymphocytes from MV tumor-bearing rabbits suppress antibody and proliferative responses to SRBC when added to lymphocytes from SRBC-primed rabbits. Finally, lysates of cultured splenic lymphocytes from rabbits given MV suppress both proliferative and antibody-forming responses to SRBC. When MV is removed from these lysates by UV inactivation or by centrifugation, the suppressive activity remains. We therefore conclude that MV induces immunologic unresponsiveness in rabbits by at least two mechanisms. First, a direct suppressive effect of added virus on in vitro lymphocyte proliferation is seen. There is no effect in this situation if an antibody response is already in progress. Second, spleen cells exposed to MV in vivo produce one or more soluble factors capable of suppressing both proliferative and antibody responses of normal lymphocytes.

Animals↗
PubMed1983

Malignant rabbit fibroma virus causes secondary immunosuppression in rabbits.

Shope fibroma virus (SFV) causes a localized, self-limited, fibroblastic proliferation in adult rabbits. Extracts of Shope fibroma tumors were found to contain a second virus that induces a rapidly progressive disseminated tumor. Dissemination of this malignant fibroma is associated with activation of commensal mucosal infection with Pasteurella multocida, causing purulent conjunctivitis and rhinitis and resulting in death from nasal obstruction. We have isolated this new agent by two cycles of plaque purification. It is a poxvirus that is antigenically virtually identical to SFV as measured by a plaque reduction assay, but behaves differently both in vivo and in vitro. We have called this virus malignant rabbit fibroma virus (MV). Electrophoresis of restriction digests made with HIND III indicates that despite the antigenic similarity of SFV and MV, the locations of HIND III sites in the two viral genomes are quite different. These experiments have enabled us to determine that MV was present in small quantities in our initial uncloned stock of Patuxent strain SFV. Lymphocytes from rabbits bearing MV-induced tumors responded poorly to both B and T lymphocyte mitogens. This nonspecific immunologic dysfunction is evident at or before the time when metastases and Gram-negative infection develop, and it becomes more profound as the disease progresses. MV-induced tumors may provide a model for Gram-negative infection and decreased immunologic responsiveness associated with malignancies.

Animals↗
PubMed1983

Immunity to pasteurellosis in compromised rabbits.

Pasteurellosis in the rabbit inoculated with a malignant variant of Shope fibroma virus (SFV-MV) is presented as a model for the study of immunosuppression and immunoprophylaxis in pasteurellosis. The rabbits, before the inoculation, were healthy carriers of Pasteurella multocida. They were intradermally inoculated with SFV-MV, and 3 to 6 days later, a primary tumor appeared at the site of inoculation. By postinoculation day (PID) 7 or 8, the rabbits had snuffles, conjunctivitis, and tumor metastases; death occurred on PID 10 to 14. Rabbits given the nonmalignant Patuxent strain of SFV developed local primary tumors, but not pasteurellosis nor metastases. In SFV-MV-inoculated rabbits, there was decreased responsiveness of spleen lymphocytes to B and T cell mitogens by day 6, and of spleen and peripheral blood lymphocytes by day 10. In addition, SFV-MV antigen was detected (by immunofluorescence) in mononuclear phagocytes in all major organs and in epithelial cells of the conjunctiva and nasal mucosa. Both nasal and conjunctival epithelia showed squamous metaplasia as well. These changes did not appear in SFV-infected rabbits. With SFV-MV-inoculated rabbits, we obtained partial protection against pasteurellosis by immunization with heat-killed P multocida or a cross-protective core lipopolysaccharide mutant of Escherichia coli (J5). Rabbits were immunized before the inoculation with SFV-MV which precipitated "spontaneous" pasteurellosis due to impaired defenses. Rabbits immunized with J5 or P multocida had less severe conjunctivitis and snuffles than nonimmunized controls, indicating that immunization with the J5 mutant may be useful as prophylaxis against pasteurellosis in compromised hosts.

Animals↗