Neutralizing human monoclonal antibodies against Puumala virus, causative agent of nephropathia epidemica: a novel method using antigen-coated magnetic beads for specific B cell isolation

Human monoclonal antibodies (MAbs) against Puumala (PUU) virus were generated and characterized. Human spleen B lymphocytes were preselected for specific surface immunoglobulin (Ig) using magnetic beads coated with the viral glycoproteins, and subsequently immortalized by Epstein-Barr virus transformation. Four IgG-positive monoclonal lymphoblastoid cell lines (LCLs) were established and have remained stable MAb secretors for over 12 months. Analyses of the antigen and epitope specificities recognized by the MAbs showed overlapping binding patterns of four anti-glycoprotein 2-specific clones. Identical isotypes (IgGl lambda) and isoelectric points (9.2) of the four MAbs suggested that they were derived from the same original clone. The MAbs reacted with eight PUU virus-like strains, but were negative for Hantaan, Seoul, and Prospect Hill viruses in an immunofluorescence assay, indicating binding to a conserved epitope unique for strains associated with the European form of haemorrhagic fever with renal syndrome, nephropathia epidemica. The MAbs neutralized all investigated PUU virus-like strains in a focus reduction neutralization test. The MAb neutralizing activity was significantly enhanced in the presence of human or guinea-pig complement. To stabilize and increase antibody secretion and to reduce the demand for culture medium supplements (e.g. fetal calf serum), three of the monoclonal LCLs were fused with the non-secreting human x mouse partner SPAM-8. Several of the established human x (human x mouse) monoclonal triomas grew faster and produced larger amounts of MAbs when compared with the original LCLs.

Position-dependent nuclear accumulation of the retinoblastoma (RB) protein during in vitro myogenesis

The expression of the retinoblastoma (RB) protein has been studied during in vitro muscle differentiation by immunofluorescence staining with three different antibodies against RB protein. Proliferating mononucleate L6 rat myoblasts showed a low level of expression. As cells began to enter a nonreplicating G0 state, the cell population became heterogeneous. Some nonreplicating cells showed a high level of expression. Nuclei at the two ends of myotubes were strongly positive, whereas centrally located nuclei showed low RB expression. Overexpression of the human RB protein in rat L6 myotubes from a Semliki forest virus (SFV)-based, transient expression vector produced a similar picture. Terminally located nuclei expressed human RB at a much higher level than did the centrally located nuclei. The results suggest that individual nuclei with a multinucleated syncytium may undergo position-dependent specialization.

Double-blind trial of aspirin in primary prevention of myocardial infarction in patients with stable chronic angina pectoris. The Swedish Angina Pectoris Aspirin Trial (SAPAT) Group

Clinical trials have demonstrated a prophylactic role for aspirin in myocardial infarction and in unstable angina pectoris. The Swedish Angina Pectoris Aspirin Trial (SAPAT) is the first prospective study of aspirin in stable angina. 2035 patients were randomised double-blind to treatment with aspirin 75 mg daily or placebo. All patients were treated with sotalol for control of symptoms. The median duration of follow-up was 50 months. Compared with the placebo+sotalol group, the aspirin+sotalol group had a 34% (81 vs 124 patients) reduction in primary outcome events (myocardial infarction and sudden death; 95% confidence interval 24-49%; p = 0.003) and the reduction observed in secondary outcome events (vascular events, vascular death, all cause mortality, stroke) ranged from 22% to 32%. Treatment withdrawal caused by adverse events occurred in 109 patients in the aspirin+sotalol group and 100 in patients in the placebo+sotalol group; major bleeds, including haemorrhagic stroke, occurred in 20 and 13 patients, respectively (not significant). The addition of a low dose of aspirin to sotalol treatment showed significant benefit in terms of cardiovascular events, including a significant reduction in the incidence of first myocardial infarction in patients with symptoms of stable angina pectoris.

Anti-GM3-lactam monoclonal antibodies of the IgG type recognize natural GM3-ganglioside lactone but not GM3-ganglioside

Immunization of mice with a synthetic GM3-lactam-BSA (bovine serum albumin) conjugate (designed to emulate the corresponding natural GM3-lactone conjugate), followed by fusion of splenocytes with myeloma cells, gave rise to more than 300 monoclonal hybridomas producing antibodies to GM3-lactam-BSA, which did not react with Glc-BSA and BSA. Eight antibody clones were randomly chosen from the positive 300 hybridomas. The eight clones, all belonging to the IgG class, were unreactive against GM3-ganglioside, whereas two antibodies (P5-1 and P5-3, both IgG1, kappa) reacted with GM3-ganglioside lactone. Binding of these two antibodies to the GM3-lactam-BSA conjugate was inhibited by soluble glycosides of GM2-, GM3-, and GM4-lactam and by GM3- and GM4-lactam, respectively, but not by Gb3 or asialo-GM1 and GM2-saccharides. A third antibody (P3; IgG2b, kappa) was inhibited by GM2-, GM3-, and GM4-lactam, but did not recognize GM3-ganglioside lactone.

Short-term restraint stress and s.c. saline injection alter the tissue levels of substance P and cholecystokinin in the peri-aqueductal grey and limbic regions of rat brain

Rats were exposed to short-term restraint (held by the tail for 1 min), injected s.c. with saline or subjected to the combination of these treatments. Fifteen and 30 min after these treatments the means serum corticosterone level was significantly increased by more than four times, compared to rats taken directly from their home cages, indicating a stress response. In the peri-aqueductal grey, the level of substance P-like immunoreactivity was increased by 45% (P < 0.01) and 65% (P < 0.01) 30 and 60 min after the combined treatment, respectively. Significant increases of the level of substance P-like immunoreactivity in the peri-aqueductal grey were also found after restraint only and after a s.c. saline injection. Similar, but less marked, changes in the level of cholecystokinin-like immunoreactivity in the PAG were also seen. In the accumbens a significantly decreased level of substance P-like immunoreactivity was encountered at 15 and 30 min after treatment, while the levels of cholecystokinin- and neuropeptide Y-like immunoreactivity were not significantly changed. In other regions studied, no effects on peptide levels were seen. The changes in peptide levels had a time course similar to that of the increase in serum corticosterone. Also the successive removal of rats from a common cage was found to increase significantly the serum corticosterone and the substance P-like immunoreactivity in the peri-aqueductal grey in the animals that were taken late in sequence from the cage.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretion of thioredoxin after in vitro activation of human B cells

The redox-active enzyme thioredoxin (Trx) is secreted by various virus-transformed cell lines of B- and T-cell origin and has been considered to play an autoregulatory role as a cofactor during cellular growth processes. We show in this paper that exposure of B lymphocytes from normal, healthy donors and B cells from B-type chronic lymphocytic leukemia (B-CLL) to Staphylococcus aureus Cowan I (SAC) induced expression of Trx mRNA. By combining SAC, or the phorbol ester TPA, with IL-2 and the conditioned medium of a T-cell hybridoma (BSF-MP6), we could strongly enhance the Trx expression. After [35S]methionine labeling of stimulated B-CLL cells in vitro, Trx was immunoprecipitated both from cell extracts and from the medium with antibodies against human placenta Trx. Secretion of newly synthesized Trx was also confirmed by a quantitative radioimmunoassay for human Trx. During 24 h cultivation experiments, treatment with SAC induced a 5-fold increase of the Trx content of normal B lymphocytes as well as in B-CLL cells. Approximately two-thirds of the total amount of the enzyme was released into the medium.

Transcription of unrearranged Ig H chain genes in human B cell malignancies. Biased expression of genes encoded within the first duplication unit of the Ig H chain locus

Analysis of the H chain class switch recombination events on the productive and nonproductive alleles of several human B cell lines has demonstrated that, in the majority of cases, the two loci had rearranged different CH genes. The absence of a strict correlation between the two rearrangement events has been interpreted in favor of a stochastic switching mechanism in human B cells. Based on the accessibility model for the H chain class switch, we have considered an alternative explanation, namely, that transcriptional activation of more than one CH gene could render more than one isotype accessible for recombination. In order to test this possibility, we have stimulated a number of IgM-bearing B cell tumors and analyzed the transcriptional response of their unrearranged C gamma and C alpha H chain genes at the Ig class level by Northern hybridization and at the subclass level by RNA-RNA solution hybridization. Our data show that human clonal B cell populations can simultaneously express germ-line transcripts of both gamma and alpha genes. Our data also demonstrate a bias in the expression of the different isotypes in the B cell chronic lymphocytic leukemias analyzed, with the genes present with the first duplication unit of the H chain locus (gamma 3, gamma 1, and alpha 1) being expressed almost exclusively. These findings indicate that transcriptional activation of large chromosomal regions containing more than one CH gene could render all the genes available for recombination and, therefore, provide an explanation for the asymmetry in the rearrangement events that have previously been described in human B cell tumors. The possible relevance of our findings to the molecular mechanism of the H chain class switch is discussed.

Transcription of unrearranged Ig H chain genes in human B cell malignancies. Biased expression of genes encoded within the first duplication unit of the Ig H chain locus

Analysis of the H chain class switch recombination events on the productive and nonproductive alleles of several human B cell lines has demonstrated that, in the majority of cases, the two loci had rearranged different CH genes. The absence of a strict correlation between the two rearrangement events has been interpreted in favor of a stochastic switching mechanism in human B cells. Based on the accessibility model for the H chain class switch, we have considered an alternative explanation, namely, that transcriptional activation of more than one CH gene could render more than one isotype accessible for recombination. In order to test this possibility, we have stimulated a number of IgM-bearing B cell tumors and analyzed the transcriptional response of their unrearranged C gamma and C alpha H chain genes at the Ig class level by Northern hybridization and at the subclass level by RNA-RNA solution hybridization. Our data show that human clonal B cell populations can simultaneously express germ-line transcripts of both gamma and alpha genes. Our data also demonstrate a bias in the expression of the different isotypes in the B cell chronic lymphocytic leukemias analyzed, with the genes present with the first duplication unit of the H chain locus (gamma 3, gamma 1, and alpha 1) being expressed almost exclusively. These findings indicate that transcriptional activation of large chromosomal regions containing more than one CH gene could render all the genes available for recombination and, therefore, provide an explanation for the asymmetry in the rearrangement events that have previously been described in human B cell tumors. The possible relevance of our findings to the molecular mechanism of the H chain class switch is discussed.

Cell phenotype (CD23)-dependent variation in EBV genome copy numbers within lymphoblastoid cell lines (LCL)

Three Epstein-Barr-virus-transformed lymphoblastoid cell lines (LCL) were analysed on the basis of their CD23 expression. Levels of EBV-DNA were compared in the positive and negative subpopulations. Two lines were further analysed with regard to EBNA, cytoplasmic immunoglobulin (cIg) and lytic (EA/VCA) protein expression. Both subpopulations had a similar MHC class-II transcription, but the CD23- subpopulation had a lower plating efficiency and a lower rate of DNA synthesis. In the B6, NAD50 and 0467.3 cell lines, CD23- cells contained 2 +/- 0.2 - 6.4 +/- 3.0 times less EBV DNA than the corresponding CD23+ population. EBNA was expressed in 81 +/- 4.2% - 93 +/- 3.8% of the CD23+ cells and in 0 - 46 +/- 8.0% of the CD23- cells. No CD23+ cells in B6 or NAD50 contained any EA/VCA, while 19 +/- 2.8% - 24 +/- 4.2% of the CD23- cells were positive for the lytic-cycle-associated antigens. Of the CD23- cells, 70 +/- 8.6% - 86 +/- 6.0% were positive for cytoplasmic immunoglobulin compared to 14.7 +/- 2.7% - 14.9 +/- 1.8% in the corresponding CD23+ population. We have previously shown that only 18% of the cIg-positive cells were EBNA-positive in the B6 line compared to 94% in the cIg- population. This was open to 2 alternative interpretations: loss of EBV genomes from a fraction of the cells with subsequent differentiation to secretory immunoglobulin production, or down-regulation of EBNA expression in differentiating, EBV-genome-positive cells. Our present findings speak for the first alternative, indicating that a certain proportion of the cells may lose their EBV genomes in both long-established and freshly transformed LCLs. This is accompanied by a reduced percentage of EBNA-positive cells, the disappearance of at least one activation marker (CD23) associated with the virally induced blast transformation, and an increased synthesis of cIg.

Co-localization of the retinoblastoma protein and the Epstein-Barr virus-encoded nuclear antigen EBNA-5

A monoclonal antibody (aRB1C1) raised against an Rb fusion protein detects a limited number (4-10) of relatively large intranuclear foci in an EBV-immortalized cord blood cell line (IB4). These domains also bind an anti-EBNA-5 monoclonal antibody. The Rb antibody reactive sites also co-localize with the SV40 T antigen in transformed monkey cells (COS). The nuclear structures stained by aRB1C1 and EBNA-5 antibodies are distinct from the structures detected with antibodies against centromeric proteins and certain snRNP epitopes. EBNA-5/Rb-positive domains do not selectively react with antibodies against the La antigen known to associate with the small EBV-encoded nuclear RNA species designated as the EBERs.

Human B lymphocytes possess 5-lipoxygenase activity and convert arachidonic acid to leukotriene B4

Incubation of cell sonicates from monoclonal B cells with arachidonic acid led to the formation of leukotriene (LT) B4 and 5-hydroxy-eicosatetraenoic acid (5-HETE). In contrast, stimulation of intact B cells with the calcium ionophore A23187 +/- arachidonic acid did not, under similar conditions, lead to formation of LTB4. The identification of these products was based on reverse phase- and straight phase-HPLC analysis, UV-spectroscopy and gas chromatography-mass spectrometry. Cell sonicates of highly enriched human tonsillar B lymphocytes also converted arachidonic acid to LTB4 and 5-HETE. Activation of these cells with B cell mitogen and cytokines for three days led to an upregulation of 5-lipoxygenase activity. This study provides evidence for the biosynthesis of LTB4 from arachidonic acid in B cell lines and in normal human tonsillar B lymphocytes.

Intranuclear distribution of Epstein-Barr virus-encoded nuclear antigens EBNA-1, -2, -3 and -5

Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs) express at least seven virally encoded proteins. Their functional role, and their relationships to each other and to normal nuclear constituents are virtually unknown. As the first step towards a topographical study, the intranuclear distribution of EBV-encoded nuclear antigens EBNA-1, -2, -3 and -5 (abbreviated E1, E2 etc.) was examined in EBV-transformed LCLs by immunofluorescence and digital image analysis of fluorescence patterns. E1-E3 showed a finely granular distribution. The E2 patterns were virtually identical when comparing indirect staining using an E2-specific mouse monoclonal antibody with anticomplement immunofluorescence using a human antibody, rendered monospecific to E2 by absorption. The E1/E2 patterns showed 32% overlap and the E2/E3 10% overlap in the high overlap category (66.7-100%), while the E2/E2 comparison with two reagents showed 61% overlap in this category. This suggests that E2 and E3 largely appear in different nuclear structures, whereas E1 appears to be randomly distributed with regard to E2. The E5 pattern was radically different from that of E1, E2 and E3. The anti-E5 mouse monoclonal antibody detected 4–10 huge, globular, sharply circumscribed dots, located in dispersed chromatin areas, while the distribution of E1, E2 and E3 showed no obvious relationship to chromatin distribution. The methods described here allow a more refined topographical analysis of the EBNA protein family, mostly in relation to each other, in relation to other nuclear proteins, and with respect to specialized functional domains in interphase chromatin.(ABSTRACT TRUNCATED AT 250 WORDS)

An improved dot immunobinding assay for screening hybridoma supernatants. Non-purified antigen immobilized on nitrocellulose paper discs

This report describes a modified dot immunobinding assay (DIA) in microplates using a crude mixture of non-purified antigen. Nitrocellulose filter paper discs exposed to the antigen mixture were inserted into the wells and kept in place by a specially constructed device. To test the efficiency of the modification a set of monoclonal antibodies from a mouse immunized with 58 kDa trpE-Bmyc fusion protein were screened. The advantage of this modified method over conventional ELISA is that it permits the use of non-purified antigen for screening large numbers of monoclonal antibodies.

The effect of selective serotonergic neurotoxin treatment on tachykinin levels in the rat ventral spinal cord

The levels of 5-hydroxytryptamine and tachykinin neuropeptides substance P, neurokinin A, neurokinin B and neuropeptide K were measured in the spinal cord of rats treated by intraventricular injection of the selective serotonergic neurotoxin 5,7-dihydroxytryptamine. The spinal cord levels of 5-hydroxytryptamine as measured by high performance liquid chromatography with electrochemical detection decreased by more than 90% in the ventral and dorsal cord compared to controls. The levels of substance P as measured by radioimmunoassay were significantly reduced (66%, P less than 0.01) in the ventral lumbar cord only. In this region, neurokinin A, neurokinin B and neuropeptide K levels were determined by combined high performance liquid chromatography and radioimmunoassay. The neurotoxin treatment also caused a significant reduction of neurokinin A (72% reduction, P less than 0.01) and a non-significant reduction of neuropeptide K, but virtually no change in the neurokinin B level. Immunohistochemical studies of the ventral lumbar cord of sham-operated animals showed immunoreactivity for 5-hydroxytryptamine as well as for substance P and neurokinin A in nerve fibres around motor neurons. In neurotoxin-treated rats this region was devoid of immunohistochemically detectable substance P- and neurokinin A-positive fibres and showed very sparse or no 5-hydroxytryptamine immunoreactivity. We conclude that among the tachykinins both neurokinin A and substance P, but probably not neurokinin B, co-exist with 5-hydroxytryptamine in nerve terminals in the rat ventral spinal cord.

Abelson murine leukemia virus transforms preneoplastic Emu-myc transgene-carrying cells of the B-lymphocyte lineage into plasmablastic tumors

E mu-myc transgenic mice were back-crossed to BALB/c mice up to back-cross generation 3. The offspring that included transgene-carrying and -negative mice in approximately equal proportions were randomly divided into 2 groups. Thirty-four mice (group I) were treated with pristane, followed by A-MuLV, and 40 (group II) were injected with A-MuLV alone. Altogether, 16 lymphoid tumors developed in group I and 17 in group II. Nine of the tumors in group I and 4 in group II appeared as ascitic tumors. The ascites contained lymphoblasts and 10 to 45% plasmacytoid cells. These tumors were designated as plasmablastic lymphomas (PLs). All tumors except one were transgene-positive and did not carry translocations. An exceptional tumor in group I carried a variant 6;15 translocation but not the transgene. It obviously corresponds to the regular Abelson + pristane-induced plasmacytoma. Among 11 tested PLs, 10 had a single retroviral insertion site, while one tumor showed 3. Among 18 untreated transgenic descendants (group III), chosen randomly during serial back-crosses, 15 (83%) developed lymphomas, with no sign of plasmacytoid differentiation. The incidence was comparable in all 3 groups, assuming 50% of the mice in groups I and II to be transgenic. The time distribution of tumor development was also similar. Spleen cells from transgene-carrying mice with no clinical sign of lymphoma were infected in vitro with A-MuLV and transplanted i.p. into BALB/c recipients. PLs developed in 26 of 31 pristane-treated recipients, but in only one of 18 untreated recipients. One of 6 PLs tested was monoclonal, whereas the remaining 5 were oligoclonal. They all expressed v-abl. These results show that some of the preneoplastic B-cells that expressed constitutively active myc transgene turned into plasmablasts after infection with A-MuLV. Full development of their neoplastic potential was facilitated by the presence of pristane-granuloma.

Leukotriene B4 enhances activation, proliferation, and differentiation of human B lymphocytes

Highly purified human tonsillar B lymphocytes at different stages of activation were incubated with leukotriene B4 (LTB4). As a key marker for activation, we used the CD23 Ag. LTB4 enhanced the CD23 expression on resting B cells in synergy with B cell-stimulating factors from 4% to 50%. Maximal effect of LTB4 was observed at 10(-10) M to 10(-12) M. LTB4 also augmented the S and M phase entries as well as Ig secretion in synergy with IL-2 and IL-4. In contrast, 5S,12S-dihydroxyeicosatetraenoic acid, an isomer of LTB4, and leukotriene C4 lacked these effects. The results indicate that LTB4 amplifies lymphokine-driven activation, replication, and differentiation of human B lymphocytes.

Leukotriene B4 enhances activation, proliferation, and differentiation of human B lymphocytes

Highly purified human tonsillar B lymphocytes at different stages of activation were incubated with leukotriene B4 (LTB4). As a key marker for activation, we used the CD23 Ag. LTB4 enhanced the CD23 expression on resting B cells in synergy with B cell-stimulating factors from 4% to 50%. Maximal effect of LTB4 was observed at 10(-10) M to 10(-12) M. LTB4 also augmented the S and M phase entries as well as Ig secretion in synergy with IL-2 and IL-4. In contrast, 5S,12S-dihydroxyeicosatetraenoic acid, an isomer of LTB4, and leukotriene C4 lacked these effects. The results indicate that LTB4 amplifies lymphokine-driven activation, replication, and differentiation of human B lymphocytes.

Interleukin-2 and a T cell hybridoma (MP6) derived B cell-stimulatory factor act synergistically to induce proliferation and differentiation of human B-chronic lymphocytic leukemia cells

In this paper we communicate that cells of a selected B-CLL clone (I83), after 2 days of Staphylococcus aureus Cowan strain 1 (SAC) activation, respond to recombinant IL-2 (rIL-2) and a B cell stimulatory factor (BSF-MP6) and act in strong synergism with induction of simultaneous high-rate proliferation and differentiation. None of the factors alone or other lymphokines (IFN-gamma, TNF-alpha, 12 kDa BCGF, IL-1, IL-4, IL-5, IL-6) induced significant DNA synthesis in SAC-activated cells. However, low levels of IgM were produced by cells stimulated by SAC + rIL-2. The SAC activation was followed by an increase in IL-2 receptor (IL-2R; CD25) expression, and the proliferation induced by BSF-MP6 + rIL-2 could be blocked in a dose-dependent manner by alpha-CD25 antibody. Furthermore, flow cytometric cell cycle studies showed that SAC and BSF-MP6 + rIL-2 stimulated cells underwent a complete transition through the cell cycle to become arrested in G1. The induced proliferation by BSF-MP6 + rIL-2 was dependent on serum but independent of the 2.8% of CD4, CD8, CD14, and CD16 positive cells contaminating the I83 cell population. Previously, we reported that I83 cells activated by 12-O-tetradecanoylphorbol-13-acetate (TPA) were induced to differentiation only but that the addition of BSF-MP6 induced DNA synthesis concomitantly with the differentiation. This paper demonstrates that physiological stimuli can induce both high-rate proliferation and differentiation in a B-CLL clone in vitro. It also suggests that the low proliferation and the differentiation block in vivo, characteristic of most B-CLLs, may reflect a subnormal response of B-CLL cells to growth and differentiation factors, or a dysfunction in the factor production by the patients' T cells.