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Biomedical subjects

Y Masuho

Publications and source records attributed to Y Masuho.

At least 73 records · Page 4Linked to original sources
PubMed1994

Preparation and characterization of human rheumatoid arthritic synovial fluid phospholipase A2 produced by recombinant baculovirus-infected insect cells.

We prepared human rheumatoid arthritic synovial fluid phospholipase A2 (PLA2) [EC 3.1.1.4] from insect cells infected with a recombinant baculovirus. The PLA2 DNA was designed, changing the original codons to those used frequently in the polyhedrin gene. Sixteen oligo-deoxynucleotides ranging from 40 to 70 nucleotides were chemically synthesized and then assembled to form the whole PLA2 gene. The gene thus synthesized was then placed under the control of the polyhedrin promoter of Autographa californica nuclear polyhedrosis virus. The recombinant virus was infected into Spodoptera frugiperda cells. The infected cells secreted protein having PLA2 activity into the culture medium. The enzyme level in the medium reached about 3 mg/liter on day 4 after infection. The secreted protein was purified to a single band of 14,000 Da on SDS-PAGE, by means of cation exchange chromatography and reverse-phase HPLC. N-terminal amino acid sequence analysis revealed that the recombinant protein was recognized and cleaved at the signal sequence in the insect cell. The purified enzyme had almost the same specific enzyme activity, substrate specificity, pH optimum, Ca2+ ion dependency, and kinetic values as those of the natural enzyme.

Amino Acid Sequence↗
PubMed1994

Epitopes and biological activities of two monoclonal antibodies to platelet integrin alpha IIb beta 3.

We have developed two monoclonal antibodies (MAbs), B6A3 and C4G1. The whole molecules of the two MAbs inhibited in vitro human platelet aggregation induced by either ADP, collagen or thrombin, and their F(ab')2 fragments inhibited ex vivo platelet aggregation induced by ADP in monkey. The concentrations necessary for complete inhibition were 5 and 1 microgram/ml for B6A3 and C4G1, respectively. The Fab fragment of C4G1 but not B6A3 inhibited platelet aggregation. B6A3 and C4G1 bound to activated platelets with dissociation constants of 0.25 and 0.82 nM, respectively. B6A3 recognized an epitope on beta 3, which was sensitive to reduction and alkylation of cystine residues, and C4G1 recognized a conformational epitope on the alpha IIb beta 3 complex, which was sensitive to EDTA. The binding of fibrinogen to activated platelets was inhibited by both MAbs. However, the binding of fibrinogen to isolated alpha IIb beta 3 was inhibited by the whole molecule of C4G1 but not B6A3, although both MAbs bound to the isolated alpha IIb beta 3. The binding of these MAbs to the isolated alpha IIb beta 3 was not inhibited by either Arg Gly Asp Ser (RGDS) or fibrinogen gamma-peptide. In addition, B6A3 but not C4G1 bound to human endothelial cells. These MAbs should contribute to the elucidation of the mechanism of platelet aggregation.

Amino Acid Sequence↗
PubMed1994

Recombinant soluble CD59 inhibits reactive haemolysis with complement.

Three soluble forms of membrane attack complex inhibitory factor (MACIF or CD59) were prepared using recombinant baculovirus-infected insect cells. They consisted of 70, 77 and 86 amino acids, starting from the amino terminus of naturally occurring CD59, and were designated recombinant (r) CD59 70, 77 and 86, respectively. All three rCD59 lacked a glycosyl-phosphatidylinositol (GPI) anchor, unlike membrane CD59 which has a GPI anchor at the anchor at the carboxyl terminus (77th amino acid). Their activities in inhibiting complement activation were assayed with C5b-7 intermediate cells and C8 and C9 components. The inhibitory activity of rCD59 70 was as high as that of rCD59 77 and twice that of rCD59 86. In addition, it was one-fourth and one-hundredth lower than the activities of urine and erythrocyte CD59, respectively. However, when assayed in the presence of human serum at a final concentration of 50% (v/v), the activities of both urine and erythrocyte CD59 were greatly decreased to to one-tenth of that of rCD59 70. Purified rCD59 70 molecules were all glycosylated, but rCD59 77 and 86 were mixtures of glycosylated and non-glycosylated molecules. The inhibitory activities of rCD59 77 and 86 were the same for the glycosylated and non-glycosylated forms. These results suggest that the soluble rCD59 provide a means for elucidating the biological roles of CD59.

Amino Acid Sequence↗
PubMed1992

Generation and characterization of a human monoclonal antibody that neutralizes diverse HIV-1 isolates in vitro.

OBJECTIVE: The purpose of this study was to develop and characterize human monoclonal antibodies (HuMAb) that neutralize HIV-1. DESIGN: Based upon previous studies involving the generation of HuMAb that neutralize other enveloped viruses, we thought it feasible to generate HuMAb that might neutralize HIV-1. METHODS: A HuMAb was generated by fusing splenic B-cells from an HIV-positive patient with a mouse myeloma cell line. Flow cytometry was used to determine surface reactivity of the HuMAb on HIV-infected and non-infected cells. Radioimmunoprecipitation was employed to elucidate the antigen recognized by the HuMAb. A cell survival assay was used to determine the ability of the HuMAb to neutralize divergent isolates of HIV-1 in the presence or absence of complement. A gp120-CD4 inhibition enzyme-linked immunosorbent assay (ELISA) was developed in order to initiate studies to determine the mechanism of neutralization by the HuMAb. RESULTS: An anti-HIV HuMAb was generated that neutralized two HIV-1 isolates (IIIB and MN) without complement and which neutralized one divergent isolate (RF) and one clinical isolate in the presence of complement. This HuMAb, designated S1-1, was found, by flow cytometric analysis, to react with the surface of HIV-1-infected but not with uninfected cells. Radioimmunoprecipitation analysis demonstrated that S1-1 binds to native HIV gp120, but not dithiothreitol (DTT)-treated gp120. In addition, HuMAb S1-1 did not bind to denatured HIV antigens in Western blot analysis. HuMAb S1-1 effectively inhibited the binding of gp120 to soluble CD4 in ELISA. CONCLUSIONS: These results suggest that the epitope recognized by S1-1 is conformational and conserved among diverse HIV-1 isolates and may represent an uncharacterized HIV neutralizing domain within or close to the CD4 binding domain on gp120. HuMAb S1-1 might have a role to play in vaccine development or passive immunotherapy.

Antibodies, Monoclonal↗
PubMed1992

Neutralizing mechanisms of two human monoclonal antibodies against human cytomegalovirus glycoprotein 130/55.

The neutralization of human cytomegalovirus (HCMV) after adsorption to the cell surface at 4 degrees C was studied using two neutralizing monoclonal antibodies (C-23 and C-41) recognizing glycoprotein 130/55. HCMV adsorbed to cells was neutralized by C-23 (complement-independent), but not by C-41 (complement-dependent). Furthermore, the virus remained sensitive to C-23 for 120 min after shifting up from 4 degrees C to 37 degrees C, suggesting that C-23 might block an early stage of virus penetration into cells, and also that transition from virus attachment to virus penetration might be quite slow. The cell-to-cell infection of HCMV was also blocked only by C-23, and not by C-41. On the basis of the results presented here, we suggest that C-41 blocks the attachment of virus to the cell surface whereas C-23 prevents the penetration of virus into the cell.

Adsorption↗
PubMed1992

Sequence analyses of three immunoglobulin G anti-virus antibodies reveal their utilization of autoantibody-related immunoglobulin Vh genes, but not V lambda genes.

Accumulated sequence analyses of the antibody repertoire have revealed that most autoantibodies and developmentally regulated antibodies share a small set of germline Ig-variable region (V) genes. The findings have prompted speculation that certain autoantibodies are of developmental importance and may be instrumental in maintaining homeostasis of the adult antibody repertoire. In order to evaluate this hypothesis critically, it is first necessary to determine the V gene usage in human antibodies against foreign substances. Unfortunately, only a few such antibodies have had their heavy and light chains characterized. To rectify the situation, we adapted the anchored polymerase chain reaction to clone and analyze rapidly the expressed V genes for three anti-virus IgG antibodies. The results show that all three heavy chain V (Vh) genes are highly homologous to the known autoantibody-related Vh genes. In contrast, two light chain V (VL) genes of the V lambda 1 subgroup are similar to a non-autoantibody-related germline V lambda 1 gene. Taken together with the reported Vh and VL sequences of several antibodies against viruses and bacteria, the data show that many antipathogen antibodies may use the same small set of Vh genes that encode autoantibodies, but diverse VL genes that are distinct from autoantibody-related VL genes. Thus, only a small portion of the potentially functional germline Vh genes are used recurrently to generate most antibodies in a normal antibody repertoire, regardless of their reactivities with either self or non-self.

Amino Acid Sequence↗
PubMed1991

In vitro efficacy of anti-HIV immunotoxins targeted by various antibodies to the envelope protein.

Six different anti-HIV envelope antibodies and one irrelevant control antibody were coupled to ricin A chain and tested for their efficacy in inhibiting HIV tissue culture infections. The anti-HIV antibodies consisted of five monoclonals, three of murine and two of human origin, and one polyclonal preparation prepared by affinity purifying pooled serum antibodies from HIV-infected humans on rgp160. The binding specificity of the antibodies was defined by ELISA by using recombinant envelope proteins and synthetic peptides, and by flow cytometry on HIV-infected cells. The in vitro efficacy of the antibodies was tested by the abilities of the immunotoxins to inhibit protein synthesis in persistently infected cell lines and by their abilities to inhibit HIV production during both acute and persistent infection as measured with an HIV-specific focal immunoassay. The immunotoxins were tested against a panel of distinctly different HIV isolates. The results indicate the following: 1) A mAb to the immunodominant neutralizing loop was highly effective against homologous strains of HIV, but had no activity against heterologous HIV. 2) The efficacy of anti-gp41 mAb varied depending upon the epitope recognized and possibly the affinity of binding to gp41. 3) The polyclonal human anti-gp160 antibodies produced the immunotoxin with the broadest specificity for different HIV strains and the greatest specific activity. This is related to the polyclonal nature of the preparation rather than an increase in relative avidity of the antibody. 4) Activity of an immunotoxin is not a direct function of the binding of the antibody to the surface of infected cells. 5) The ability of an immunotoxin to halt the spread of infection through a tissue culture cell population is dependent upon the ability of the antibody to neutralize the virus as well as the activity of the toxin. Our data suggest that efficacious immunotoxins for the treatment of AIDS may be made with polyclonal anti-envelope antibodies derived from the serum of patients who have been infected with HIV or with appropriately chosen anti-gp41 antibodies.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Recognition of human immunodeficiency virus glycoproteins by natural anti-carbohydrate antibodies in human serum.

Anti-carbohydrate antibodies were isolated from Human immunodeficiency virus (HIV) negative human serum by affinity chromatography using yeast mannan followed by protein A. The purified mannan-binding IgG (MBIgG) bound to HIV glycoproteins gp 160, gp 120 and gp 41 in Western blot. Immunofluorescence revealed that MBIgG bound to HIV/IIIB-infected H9 cells but not to uninfected H9 cells, suggesting that carbohydrate structures recognized by MBIgG are specifically expressed on HIV-infected cells. MBIgG did not neutralize infectivity of HIV. These results show that normal human serum contains natural antibodies reactive to carbohydrate structures of HIV glycoproteins propagated in human cells.

Antibodies↗
PubMed1991

Structural study of the sugar moieties of monoclonal antibodies secreted by human-mouse hybridoma.

Six monoclonal antibodies, three each of human IgG1 and IgG2 subclasses, were obtained from human-mouse hybridomas. Structural study of their asparagine-linked sugar chains was performed to elucidate the regulatory mechanism of secreted monoclonal IgG glycosylation. The sugar moieties were quantitatively released as oligosaccharides from the polypeptide backbone by hydrazinolysis. They were converted into radioactive oligosaccharides by NaB3H4 reduction after N-acetylation. Structural study of each oligosaccharide by lectin affinity column chromatography, sequential exoglycosidase digestion, and methylation analysis indicated that almost all of them were biantennary complex-type sugar chains containing Man alpha 1----6(Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4 (+/- Fuc alpha 1----6)GlcNAc as core structures. Bisecting N-acetylglucosamine residue, which is present in human IgG but not in mouse IgG, could not be detected at all. The molar ratio of each oligosaccharide from the six IgG samples was different. However, no subclass specificity was detected except that all IgG1 contained neutral, mono-, and disialylated sugar chains, whereas IgG2 did not contain disialylated ones. The molar ratio of N-acetylneuraminic acid to N-glycolylneuraminic acid was also different for each IgG. All six IgGs contained monoantennary complex-type and high mannose-type oligosaccharides which had never been detected in serum IgGs of various mammals so far investigated. These results indicated that the processing of asparagine-linked sugar chains of IgG is less complete in human-mouse hybridoma than in human or mouse B cells, and that the glycosylation machinery of the mouse cells is dominant in the hybrid cells.

Animals↗
PubMed1991

Homotypic antibody responses to fresh clinical isolates of human immunodeficiency virus.

Human immunodeficiency virus type 1 (HIV-1) exhibits extensive genomic and antigenic diversity, which is thought to contribute to the failure of the host's immune response to control infection and prevent clinical progression. Part of this failure may be due to utilization by the virus of antigenic variation as a means to escape protective immune responses. Antibody-escape variants of HIV-1 were studied here using fresh clinical isolates and autologous plasmas. HIV-1 was isolated from the plasma of seven people who were all seropositive for at least 2 years, and symptomatic sometime during that period. Isolated viruses were confirmed as HIV-1 by the presence of reverse transcriptase activity in infected culture supernatants, and by positive immunofluorescence using human monoclonal antibody to HIV-1 core protein. Plasma from these people were positive by Western immunoblot (DuPont) for most major HIV-1 (strain IIIB) antigens. These plasmas neutralized three laboratory strains of HIV-1 (i.e., IIIB, RF, and MN) but did not neutralize the homotypic strain in five cases, and had greatly reduced neutralizing titers against the homotypic strain in two cases. Homotypic neutralizing antibodies were absent in autologous plasma obtained 3 months later. When antibody titers were measured by fixed-cell indirect immunofluorescence assays (IFAs), high titers of IgG (1:6400 to 1:25,600) were detected against HIV-1 IIIB, while low titers of only 1:20 to 1:160 were detected against homotypic viral antigens at the time of virus isolation, and remained low 12 and 16 weeks later. No class IgA, IgD, IgE, or IgM antibodies to homotypic viral antigens, as possible IgG-blocking antibodies, were detected by fixed-cell IFAs. Cross-reactions with heterologous donor's plasmas were observed in some cases, and in these cases the cross-reactions were unidirectional. Live-cell IFAs detected IgG in patient's plasma to HIV-1 IIIB-infected cells but not to cells infected with homotypic isolates. These results suggest that it is common for neutralization-resistant HIV-1 variants to appear during the course of infection, and that all or most antigens of these variants are capable of escaping antibody recognition.

AIDS-Related Complex↗
PubMed1991

Conjugates of superoxide dismutase with the Fc fragment of immunoglobulin G.

We constructed conjugates of superoxide dismutase (SOD) and the Fc fragment of human immunoglobulin G. The lysyl residues of bovine erythrocyte Cu,Zn-SOD were covalently linked with cysteine residues of the Fc fragment using N-succinimidyl 4-(N-maleimido)-butylate as a crosslinking agent. Analysis by gel filtration and SDS-PAGE revealed that the conjugates were composed of one molecule of SOD linked with one molecule of Fc [SOD-(Fc)1] and one SOD molecule linked with several Fc molecule [SOD-(Fc)n]. The resulting SOD-Fc conjugates retained more than 90% of the enzyme activity of SOD. When those conjugates were administered intravenously to mice, the half-lives of SOD activity in the circulation were 29 and 42 h for SOD-(Fc)1 and SOD-(Fc)n, respectively, while free SOD had a half-life of 5 min. Intravenous administration of the conjugates to mice markedly repressed the increase in serum glutamic-oxaloacetic transaminase (GOT) activity induced by paraquat. These results suggest that SOD-Fc conjugates, which have long half-lives, effectively perform dismutation of superoxide radicals and may be useful for preventing tissue injury caused by hazardous oxygen metabolites.

Animals↗
PubMed1991

Phase I study on human monoclonal antibody against cytomegalovirus: pharmacokinetics and immunogenicity.

MAb C23, a human immunoglobulin G1 (IgG1) monoclonal antibody (MAb) against cytomegalovirus, was administered to 20 healthy volunteers. Sixteen of them received a single infusion of a dose ranging from 5 to 80 mg. The plasma clearance curves fit a two-compartment model, with half-lives of 31.0 +/- 23.6 h in the diffusion phase and 24.2 +/- 5.8 days in the equilibration phase. The plasma after administration had the virus neutralization activities that were equivalent to the plasma MAb C23 levels. The remaining four subjects, who received three infusions of 60, 20, and 20 mg at 1-week intervals, showed pharmacokinetics that were very consistent with those of the single infusion. No antibody response against MAb C23 was observed in any of the subjects at any time, when monitored for approximately 60 days after the single infusion or the third infusion of the three repeated doses. None of the 20 subjects showed any treatment-related clinical signs or changes. These results suggest that a human IgG MAb has the same pharmacokinetic characteristics as those of natural human serum IgG, and that it is not immunogenetic and is safe in humans.

Antibodies, Anti-Idiotypic↗
PubMed1991

A human monoclonal antibody against varicella-zoster virus glycoprotein III.

Hybridomas producing human monoclonal antibodies (HMAbs) against varicella-zoster virus (VZV) were generated by fusing murine myeloma cells with human lymphocytes immunized in vitro. An assay system was developed to select anti-glycoprotein (gp)III HMAbs from the pool of anti-VZV HMAbs. A murine anti-gpIII MAb, 4B7, did not react with a VZV-infected cell homogenate, but did react with a VZV-infected cell monolayer, whereas anti-gpI and anti-gpII MAbs reacted with both antigens. Hybridomas were screened to obtain HMAbs having a reaction profile similar to that of 4B7 and one such clone, V3, stably produces human IgG1 (kappa). HMAb V3 immunoprecipitated a VZV antigen of 115K to 120K, which was not immunoabsorbed by an anti-gpII HMAb, implying that V3 recognizes gpIII. V3 neutralized VZV independently of complement, unlike anti-gpI and anti-gpII HMAbs. All five strains of VZV tested were completely neutralized by V3, and the dose of V3 required to reduce the number of virus plaques by 50% ranged from 0.027 to 0.15 micrograms/ml. V3 was also able to inhibit the spread of virus infection from infected to uninfected cells, whereas anti-gpI and anti-gpII HMAbs could not. In addition, V3 mediated antibody-dependent cellular cytotoxicity but not complement-dependent cytotoxicity of VZV-infected cells. The results suggest that an anti-gpIII HMAb may provide a new means of passive immunoprophylaxis and also help to identify an antigenic epitope appropriate for a subunit vaccine.

Animals↗
PubMed1991

Rapid diagnosis of cytomegalovirus infections by direct immunoperoxidase staining with human monoclonal antibody against an immediate-early antigen.

Direct immunoperoxidase technique using a horseradish peroxidase (HRP)-conjugated Fab' fragment of human monoclonal antibody (humab C7), designated HRP-C7, was evaluated as a rapid diagnosis of cytomegalovirus (CMV) infection. A total of 138 clinical specimens consisting of 124 urine samples and 14 oral swabs were examined for CMV by the direct HRP-C7 staining in comparison with conventional virus isolation. The number of CMV-positive samples by each method was 40 (29.0%) for the former and 37 (26.8%) for the latter, respectively. By HRP-C7 staining, CMV was identifiable within 24 hr after inoculation. By conventional isolation method, an average of 10.3 days had passed before cytopathic effect characteristic of CMV appeared in the cell culture. Some false-positive and false-negative cases were discussed in relation to toxicity of urine samples, storage of the samples, and amount of CMV in the sample. The sensitivity and specificity of HRP-C7 method against conventional isolation method were 89.2% and 93.1%, respectively. Thus, HRP-C7 staining is useful for a rapid diagnosis of CMV infections.

Antibodies, Monoclonal↗
PubMed1990

Preparation of human monoclonal antibodies against a cytomegalovirus glycoprotein complex of 130 and 55 kDa.

Nine human monoclonal antibodies (MAbs) with neutralization activity against cytomegalovirus (CMV) were obtained by screening human MAbs using a CMV glycoprotein complex of 130 and 55 kDa (gp130/55). The gp130/55 antigen was purified by immunoaffinity chromatography and the purified antigen used to detect anti-gp130/55 MAbs in an enzyme-linked immunosorbent assay. Relatively few of the human anti-CMV MAbs were directed against gp130/55 but all showed high neutralization activities to a variety of clinical isolates with titers (ED50 values) ranging from 0.15 to 7.9 micrograms/ml. Six of the nine anti-gp130/55 MAbs required complement for virus neutralization. Such human MAbs may prove to be useful for passive immunotherapy against CMV infection.

Antibodies, Monoclonal↗
PubMed1990

Human monoclonal antibodies to the human immunodeficiency virus type 1 (HIV-1) transmembrane glycoprotein gp41 enhance HIV-1 infection in vitro.

Three of 16 human monoclonal antibodies (hu-mAbs) enhanced human immunodeficiency virus type 1 (HIV-1) infection of MT-2 target cells by means of a mechanism that is dependent on complement. Enhanced infections are characterized by an increase in cytopathic effects and antigen synthesis as well as an increase in the production of progeny virus as detected by release of reverse transcriptase activity and infectious virus into the culture medium. Analyses by radioimmunoprecipitation, Western blot, and ELISA using the pENV9 envelope fragment localize the antigenic specificities of these three hu-mAbs to the N-terminal two-thirds of the transmembrane protein gp41. Competitive binding experiments indicate that the hu-mAbs are reactive with immunodominant epitopes of gp41 recognized by sera from essentially all HIV-1-infected subjects. Combination dose-effect experiments demonstrate that these hu-mAbs can act synergistically in vitro to enhance HIV-1 infection. These data demonstrate that hu-mAbs directed against the HIV-1 transmembrane glycoprotein gp41 can enhance HIV-1 infection in vitro. The availability of these reagents allows for the mapping of enhancing epitopes on HIV-1 and provides a means for studying whether deletion of such enhancing epitopes from candidate HIV-1 vaccines might improve the protective immune response to HIV-1 in immunized humans and chimpanzees.

Antibodies, Monoclonal↗