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J L Portis

Publications and source records attributed to J L Portis.

At least 55 records · Page 3Linked to original sources
PubMed1987

Identification of two forms of an endogenous murine retroviral env gene linked to the Rmcf locus.

The Rmcf gene restricts the replication of recombinant murine mink cell focus-inducing (MCF) viruses in cell cultures derived from mice carrying the resistance allele (Rmcfr) and may play a role in resistance to retrovirus-induced leukemias in vivo. We have characterized the endogenous gp70 expressed by Rmcfr and Rmcfs mice with a panel of type-specific monoclonal antibodies which discriminate xenotropic and MCF gp70. Embryo and tail skin cultures derived from Rmcfr mice (DBA/2 and CBA/N) expressed gp70 bearing a determinant unique to MCF viruses, whereas cultures from Rmcfs mice expressed either no detectable gp70 (NFS/N and IRW) or a gp70 serologically related to a subgroup of xenotropic viruses (C57BL/6, CBA/J, and A/WySn). Studies of progeny embryos derived from a (C57BL/6 X DBA/2) X C57BL/6 backcross established that the Rmcf resistance allele was linked to the expression of the MCF gp70 and that the gene encoding the xenotropic gp70 expressed by C57BL/6 Rmcfs mice was allelic with the MCF gp70 from Rmcfr mice. These data indicate that the Rmcf locus contains an endogenous gp70 gene having two allelic forms, one of which inhibits exogenous MCF infection in vitro by a mechanism of viral interference.

Animals↗
PubMed1987

Horizontal transmission of murine retroviruses.

Both a feral mouse ecotropic virus (WM-E) and Friend ecotropic virus (F-MuLV) were transmitted horizontally among adult mice. Infection resulted in the production of antiviral antibody in the recipients, with no evidence of viremia or clinical disease. However, persistent low-level virus replication was detectable in the spleens of these mice as long as 8 months after initial infection. External secretions, including saliva, semen, and uterine secretions from viremic mice contained high concentrations of infectious virus. Nevertheless, transmission occurred only from viremic males to either males or females. Male-to-male transmission appeared to occur by parenteral inoculation of infectious saliva during fighting behavior. Evidence is presented that infection of females was by the venereal route. Of four mouse strains examined, NFS/N, IRW, and C57L females were all susceptible to venereal infection, whereas AKR mice were not. Since AKR mice are susceptible to infection by WM-E administered parenterally, this resistance appeared to be mediated by local viral interference due to the high-level expression of endogenous Akv gp70 within the female reproductive tract. Although both WM-E and F-MuLV were transmitted from viremic males to females, infection by WM-E was significantly more efficient than that by F-MuLV. This difference correlated with a distinct difference in cellular tropism of WM-E and F-MuLV within the epididymis of viremic males. F-MuLV gp70 was expressed only within stromal elements, whereas WM-E gp70 was seen largely within the epithelial lining cells and luminal contents of the duct. No evidence of virus expression within germ cells was observed. The possible influence of virus expression by epithelial cells of the female reproductive tract on infection of embryos is discussed.

Animals↗
PubMed1985

Infectious entry of murine retroviruses into mouse cells: evidence of a postadsorption step inhibited by acidic pH.

The entry into cells by many enveloped RNA viruses is accomplished by endocytosis and subsequent penetration of the endosomal membrane by an acidic pH-dependent fusion event. In the current study, we examined early events in the infectious entry of mouse retroviruses, using as a framework the observation that infection of a mouse tail skin cell line by the ecotropic virus Friend murine leukemia virus was inhibited at mildly acidic pH (pH 6). This inhibition operated on a postadsorption step, since binding of virus was unaffected at this pH. The rate of penetration of preadsorbed virus, which displayed first-order kinetics, was markedly affected by changes in the pH of the medium. The half-time for disappearance of infectious cell surface virus at 37 degrees C was approximately 10 min at pH 7.6. At pH 6.0, however, greater than 98% of the adsorbed infectivity remained at the cell surface after 45 min. This cell surface virus, though not infecting the cell at pH 6.0, retained its capacity to enter and infect the cell when the pH of the medium was raised. Acidic pH had little effect on the rate of fluid uptake by the cells, as measured by internalization of [3H]sucrose, indicating that global inhibition of endocytosis had not occurred. In contrast, cell fusion induced by Friend murine leukemia virus was optimal at pH 7.6 but markedly inhibited at a pH of less than 6.4. This inhibitory effect of acidic pH on membrane fusion is unique among the enveloped viruses which have been studied and would preclude entry of Friend murine leukemia virus from within acidified endocytic vesicles. Entry of other members of the ecotropic, mink cell focus-forming, and xenotropic host range groups displayed similar pH sensitivity. However, one xenotropic virus was relatively resistant to the effect of acidic pH, suggesting that differences might exist in the requirements for entry of different retroviruses.

Animals↗
PubMed1985

Monoclonal antibodies specific for wild mouse neurotropic retrovirus: detection of comparable levels of virus replication in mouse strains susceptible and resistant to paralytic disease.

We used AKR/J mice to produce monoclonal antibodies specific for a neurotropic ecotropic (WM-E) virus initially isolated from wild mice. The rationale for this approach involved the observation that these mice were immunologically hyporesponsive to endogenous ecotropic virus (Akv) but fully responsive to type-specific determinants of WM-E. Hybridoma cell lines derived from mice immunized with both denatured and viable virus produced antibodies with specificity for three viral membrane-associated polypeptides, gp70, p15(E), and p15gag. Epitopes specific for WM-E virus were detected in each of these polypeptides. Cross-reactivity with Friend ecotropic virus (Friend murine leukemia virus) was observed with some gp70- and p15gag-specific antibodies, but no reactivity with endogenous Akv ecotropic virus was seen. The majority of these antibodies did not react with either xenotropic or mink cell focus-forming viruses. Two WM-E-specific anti-gp70 antibodies reacting with different determinants had virus-neutralizing activity in the absence of complement, suggesting that the respective epitopes may participate in receptor binding or virus penetration events. We used these monoclonal antibodies in initial studies to examine the replication of WM-E virus in neonatally inoculated AKR/J mice which are fully resistant to the paralytic disease induced by this virus. Since these mice express high levels of endogenous ecotropic virus, standard assays for ecotropic virus cannot be used to study this question. We present evidence that the resistance to disease does not involve a resistance to virus replication, since these mice expressed levels of viremia and virus replication in spleen and lumbar spinal cord comparable to susceptible NFS/N mice at a time when the latter began to manifest clinical signs of lower-motor-neuron pathology.

Animals↗
PubMed1984

Identification of a unique erythroleukemia-associated retroviral gp70 expressed during early stages of normal erythroid differentiation.

Late in the course of Friend virus (FV)-induced erythroleukemia, leukemic spleen cells express a cell surface retroviral gp70 envelope protein not detected during the early proliferative phase of the disease. Characterization of this gp70 revealed it was unrelated to the input Friend murine leukemia virus (F-MuLV), but antigenically similar to a unique subset of endogenous xenotropic viruses. This gp70 was expressed by murine erythroleukemia cell lines but has not been identified on cell lines of other lineages. A monoclonal antibody (18-6) specifically reactive with this polypeptide was used to examine hematopoietic organs of normal uninoculated mice. This antibody detected a gp70 expressed by a majority of erythroid cells in fetal liver and by a small but significant percentage of normal adult spleen and bone marrow cells. Increased erythropoietic activity induced by treatment of adult mice with phenylhydrazine ( PHZ ) resulted in a seven- to eightfold increase in the frequency of spleen and bone marrow cells expressing this gp70. Peptide map analysis indicated that the 18-6 reactive gp70 expressed by Friend erythroleukemia cells and by cells from normal fetal liver were structurally identical. These results suggested that this unique gp70 was an erythroid-specific differentiation antigen.

Animals↗
PubMed1984

Monoclonal antibodies distinguish phase variants of Coxiella burnetii.

Monoclonal antibodies (MAbs) directed against phase I and II variants of Coxiella burnetii were produced by fusing myeloma SP2/O-AG 14 cells with spleen cells from mice immunized with the chloroform-methanol extraction residue of phase I whole cells. Two hybridoma clones which distinguished the phase variants by microimmunofluorescence assay were isolated and characterized. The MAbs showing specificity for phase I cells (MAbI-1, immunoglobulin G, subclass 3 kappa) reacted with the hot phenol-water extract of phase I C. burnetii in immunodiffusion and enzyme-linked immunosorbent assays. MAbI-1 reacted with high-molecular-weight components from phase I phenol-water extract and whole cell in an immunoblot assay. Specificity of MAbI-1 for a carbohydrate epitope in the phenol-water extract was demonstrated by periodic acid inactivation of binding by a competitive enzyme-linked immunosorbent assay. Phase I antigenic sites were apparently well represented on the surface of cells as demonstrated by complete fluorescence and microagglutination. The MAb showing specificity for phase II cells (MAbII-1, immunoglobulin G, subclass 2b kappa) reacted with whole cells in the microimmunofluorescence assay, microagglutination test, complement fixation test, and the enzyme-linked immunosorbent assay. MAbII-1 reacted specifically with a 29,500-dalton surface protein as demonstrated by immunoprecipitation of 125I-surface-labeled cells. Although MAbII-1 reacted with detergent-solubilized protein, it did not react with sodium-dodecyl sulfate-denatured protein by immunoblot assay. This protein was not exposed on the surface of phase I cells, but chloroform-methanol extraction of phase I cells exposed the phase II epitope.

Animals↗
PubMed1983

Effect of murine host genotype on MCF virus expression, latency, and leukemia cell type of leukemias induced by Friend murine leukemia helper virus.

Leukemias induced by neonatal inoculations of several mouse strains with different strains of Friend murine leukemia helper virus (F-MuLV) were followed for time of disease onset, cytochemical analysis of predominant cell types in leukemic organs, and expression of infectious mink cell focus-inducing (MCF) viruses detected by mink cell foci or MCF-specific monoclonal antibodies. Most BALB.B and IRW mice had a rapidly appearing, severe anemia and hepatosplenomegaly consisting of erythroid cells. MCF viruses were usually isolated from enlarged spleens of IRW mice. In contrast, C57BL/10 mice had a lower incidence of disease and much slower course. Splenomegaly and lymphadenopathy with mild anemia were seen, and the predominant cell types were either myeloid (chloroleukemia) or lymphoid. MCF viruses were never isolated from this mouse strain. (C57BL/10 X IRW)F1 mice were intermediate in latency, but all mice had disease by 8 months. Myeloid, lymphoid, and some mixed leukemias with an erythroid component were observed, but in no case did we see the severe anemia or pure erythroid involvement typical of IRW and BALB.B mice. MCF viruses were, however, isolated from 22% of these mice regardless of leukemia cell type. DBA/2 mice had a disease pattern similar to the (C57BL/10 X IRW)F1 mice, and MCF viruses were isolated from three of six mice tested. Inoculation of IRW mice with the low virulence B3 strain of F-MuLV produced disease with a longer latency than F-MuLV 57, but similar cell types were transformed by both viruses. In vitro cell lines were derived from 14 mice, and most were tumorigenic in vivo. Three lines released infectious MCF virus, and three others expressed MCF-specific cell surface antigens but did not release virus. Eight lines expressed no MCF infectious virus or viral antigens. Several lines released infectious xenotropic viruses and/or expressed xenotropic MuLV cell surface antigens recognized by monoclonal antibodies reactive with xenotropic viruses. The lack of MCF expression in many primary leukemic tissues as well as in in vitro derived leukemia cell lines of C57BL/10 and (B10 X IRW)F1 mice suggested that MCF virus generation and expression may not be required for leukemogenesis in some mouse strains or in some hemopoietic lineages.

Animals↗
PubMed1983

Monoclonal antibodies derived during graft-versus-host reaction. II. Antibodies detect unique determinants common to many MCF viruses.

Hybridoma cell lines were recovered from the spleens of 6-week-old (B6 X D2)F1 mice undergoing graft-versus-host reaction induced by the transfer of 5-week-old B6 parental spleen cells. These cell lines produced antibodies reactive with envelope polypeptides of a variety of MuLV. The viral specificity assessed by membrane immunofluorescence and virus-binding radioimmunoassay indicated that the reactivity of these antibodies was distinctly different from monoclonal antibodies recovered from (B6 X D2)F1 recipients of D2 spleen cells reported previously (Portis et al., Virology 118, 181-190, 1982). Ten out of 17 monoclonal antibodies in the current study reacted exclusively with MCF viruses and three of these antibodies detected envelope determinants which were shared by a broad panel of MCF viruses of diverse origin. These common MCF determinants were expressed by the gp70 molecule as determined by Western blot analysis. The production of these antibodies by young mice in the absence of exogenous virus inoculation suggests that these antigens may be encoded by endogenous MCF-like sequences.

Animals↗
PubMed1983

Naturally occurring leukemia viruses in H-2 congenic C57BL mice. III. Characterization of C-type viruses isolated from lymphomas induced by milk transmission of B-ecotropic virus.

The prevalence of different host-range classes of murine leukemia virus (MuLV) was studied in C57BL mice with (V+) and without (V-) milk transmission of a naturally occurring B-tropic ecotropic MuLV. Virus isolates were studied with respect to growth properties, XC-plaque formation, antigen profiles of their envelope proteins (gp70 and P15(E)), gp70 tryptic-peptide maps, and their potential to induce lymphomas after inoculation into newborn mice. B-tropic ecotropic MuLV with the capacity to cause plaques in XC cells was isolated from almost all lymphomas of both V+ and V- sublines. The reaction patterns of these ecotropic isolates with monoclonal antibodies reactive with MuLV-env proteins and the tryptic-peptide maps of the gp70 molecule indicate that they are similar to each other and differ only slightly from the ecotropic MuLV in the spleens of young V+ animals, which is identical to the milk-transmitted virus. XC-, B-tropic dualtropic mink cell focus-inducing (MCF) viruses were isolated from the majority of different types of lymphoma (B cell, T cell, or neither B nor T cell derived), but not from the spleens or milk of young V+ or V- animals. The env proteins of the MCF isolates are highly heterogeneous, but most isolates originating from B10.AV + T-cell lymphomas share MCF-related epitopes in their gp85 envelope precursor with AKR MCF-247 virus. Most MCF viruses isolated from non-T lymphomas do not possess these epitopes. The results indicate that also in this model the generation of dualtropic MCF viruses might be important in lymphoma induction, although only some of the cloned MCF viruses show enhanced oncogenic properties in comparison with ecotropic isolates. A cloned oncogenic MCF virus induced different lymphoma types in C57BL/10 (= B10, H-2b) and B10.A (H-2a) mice, similar to what was found earlier with the milk-transmitted virus. Hence, the lymphoma-type differences are not due to differences in the B-tropic ecotropic viruses transmitted through the milk in these strains, but reflect an influence of the H-2 complex on the phenotype of the virus-induced lymphomas.

Animals↗
PubMed1982

MCF-specific murine monoclonal antibodies made against AKR-247 MCF virus recognize a unique determinant associated with the gp70-p-15(E) complex.

Hybridomas obtained from (NFS X AKR)F mice immunized with syngeneic cells infected with AKR-247 MCF virus produced antibodies specific for only AKR-247 or closely related MCF viruses which hare a previously defined MCF antigen (MCFA-3). These monoclonal antibodies recognized a new type of viral antigenic determinant which appeared to be a conformational determinant associated with the env precursor polyprotein (pr80env) or its disulfide-linked gp70-p15(E) complex (gp80) but not with free gp70 or p15(E) or any other virion or virus-induced protein.

AKR murine leukemia virus↗
PubMed1981

Dissociation of H-2 recognition by antibody and cytotoxic T cells of a cloned murine leukemia cell line.

The differential expression of H-2 specificities recognized by antibody and by cytotoxic T lymphocytes (CTL) has been studied using a clone (FY7) of the C57BL/6 leukemia cell line FBL-3 (H-2b/H-2b). Unlike C57BL/10 spleen cells, EL-4 lymphoma cells and Y57-2C leukemia cells (all H-2b/H-2b), FY7 failed to induce the primary in vitro generation of anti-H-2b CTL by (B10.A x A)F1 (H-2a/H-2a) or B10.D2 x BALB/c)F1 (H-2d/H-2d) responder spleen cells. In addition, FY7 was not lysed by, and did not competitively inhibit anti-H-2b CTL. Quantitative absorption tests with H-2Kb and H-2Db antisera revealed that FY7 expressed these antigens in quantitatively similar amounts to EL-4. The H-2Kb product of FY7 appeared to be identical with that of C57BL/10 spleen cells both in apparent molecular weight and isoelectric point. Yet FY7 failed to inhibit anti-H-2Kb CTL competitively in a cold target inhibition assay. Possible mechanisms are discussed for the lack of T-lymphocyte recognition of the H-2Kb-gene product expressed by FY7.

Absorption↗
PubMed1979

Changes in the transplantability of a virus-induced murine leukemia tumor.

The subcutaneous growth potential of a Friend virus-induced murine leukemia cell line (FBL-3) passaged in the ascites form was found to change, depending on the interval of time spent in the peritoneal cavity. Injection sc of the original stock of FBL-3 (growth continuously in vitro) into C57BL/10 mice produced transient tumors uniformly rejected by days 20-40. The tumor cells passaged in the ascites form for 7 days behaved like the in vitro-grown cells, whereas ascites cells harvested at 14 days produced progressive lethal subcutaneous tumors in 50-70% of the recipients. The change in subcutaneous growth was reversible simply by alteration of the ascites passage schedule. Day 7 ascites cells (regressors) were converted to progressors by ip passage for 14 days, and day 14 ascites cells (progressors) were converted to regressors by ip passage for 7 days. The difference in growth potential between day 7 and day 14 ascites cells was not due to effects of nonneoplastic host cells accompanying the tumor cells in the ascites population, because neither dilution of nonneoplastic cells by in vitro culture nor selective killing of H-2a/b host cells by anti-H-2 serum and complement altered the subcutaneous growth behavior or either day 7 or day 14 ascites cells. These results indicated that the change in the growth potential of FBL-3 occurred at the level of the tumor cells. However, no quantitative differences were observed in the expression of serologically detectable tumor-associated antigens by these two populations. Possible mechanisms for this change in transplantability were considered.

Animals↗
PubMed1979

Deposition of IgA in renal glomeruli of mink affected with Aleutian disease.

The glomerular deposition of immunoglobulin (Ig) was studied in sapphire mink affected with terminal Aleutian disease (AD). Fluorescein conjugated Ig-class specific antiserums were used to evaluate and identify the glomerular Ig. Kidneys of all 28 mink with documented AD had deposits of IgA and beta 1 C in a capillary and mesangial distribution. Only 7 of 28 mink had demonstrable glomerular IgG and/or IgM. In addition, interstitial plasma cell infiltrates in 17 of 19 kidneys stained exclusively with anti-IgA. All antiserums used in this study were evaluated for Ig-class specificity by both gel diffusion and agarose-bead techniques. The striking Ig class restriction demonstrated for glomerular Ig deposition in AD is discussed in light of current knowledge of the pathogenesis of AD glomerulopathy.

Aleutian Mink Disease↗
PubMed1978

Vascular permeability changes in the central nervous system of rats with hyperacute experimental allergic encephalomyelitis induced with the aid of a substance from Bordetella pertussis.

Development of hyperacute experimental allergic encephalomyelitis in Lewis rats after intraperitoneal administration of a mixture of guinea pig spinal cord emulsion and pertussigen from Bordetella pertussis was accompanied by an increase in vascular permeability in the central nervous system. The increased permeability was most striking in the spinal cord and seemed to be associated with the ascending development of paralysis. Rats that had completely recovered from paralysis did not have any increased permeability in the central nervous system. Rats which developed paralysis after inoculation with either guinea pig spinal cord emulsion alone or with complete Freund adjuvant had only a small degree, if any, of increased permeability in the vascular system of the central nervous system.

Acute Disease↗
PubMed1976

Immune response in the garter snake (Thamnophis ordinoides).

Garter snakes (Thamnophis ordinoides) were immunized with hen egg albumin, human gamma-globulin and Keyhole limpet haemocyanin in Freund's adjuvant. Antibody was consistently detected by radioimmunoelectrophoresis and in three different gamma- and beta-globulin precipitin lines called IgM (approximately or equal to 20S), Ig-1 (approximately or equal to 9S) and Ig-2 (approximately or equal to 8-5S). Early antibody (day 31 after immunization) was frequently Ig-M whereas Ig-2 and especially Ig-1 were detectable for the longest duration (992 days). After immunization with antigen in Freund's adjuvant, Ig-1 serum concentration showed the greatest increase, from almost undetectable levels to the most prominent immunoglobulin in immune serum.

Animals↗