B4, a human B lymphocyte-associated antigen expressed on normal, mitogen-activated, and malignant B lymphocytes

The characterization of a new B cell-specific antigen (B4) is described in this report. With the use of a monoclonal antibody to B4, it was shown that B4 is present on B cells isolated from peripheral blood and lymphoid organs, on cell lines derived from normal and malignant B cells, and on tumor cells isolated from patients with B cell-derived neoplasms. B4, in contrast, was not detected on normal, activated, or malignant cells of T or myeloid origin. The B4 antigen is distinct from known B cell antigens, including sIg, Ia, B1, B2, Fc, and C3. Examination of mitogen-stimulated B lymphocytes suggests that the B4 antigen initially increases with B cell activation and then is lost at the terminal stage of B cell differentiation. Moreover, the observation that B4 is expressed on almost all early B cell tumors suggests that it may precede B1, CALLA, cytoplasmic mu, and B2 in early B cell ontogeny.     

Novel identification and differentiation of Brucella melitensis, B. abortus, B. suis, B. ovis, B. canis, and B. neotomae suitable for both conventional and real-time PCR systems

We describe the development of a novel PCR assay for the rapid detection of members of the Brucella genus, and the differentiation between six recognized Brucella species. The assay has proven to be highly specific with the additional advantage of being suitable for use with both conventional and real-time PCR.     

Absolute configurations of integracins A, B, and 15'-dehydroxy-integracin B

Integracins A (1) and B (2), potent HIV-1 integrase inhibitors, and 15'-dehydroxy-integracin B (3) were isolated for the first time from Chinese mangrove plant Sonneratia hainanensis. Their absolute configurations were determined by the Mosher's method and specific rotation analysis of alcohols (6 and 7) obtained from integracin A in two steps and by chemical correlation. Integracin A (1) also exhibited significant cytotoxicity against the tumor cell lines HepG2 and NCI-H460 with both 100% inhibitions at 25 μg/ml.     

Burkholderia species in human infections in Mexico: Identification of B. cepacia,B. contaminans,B. multivorans,B. vietnamiensis,B. pseudomallei and a new Burkholderia species

BackgroundBurkholderia sensu stricto is comprised mainly of opportunistic pathogens. This group is widely distributed in the environment but is especially important in clinical settings. In Mexico, few species have been correctly identified among patients, most often B. cepacia is described.Methodology/Principal findingsIn this study, approximately 90 strains identified as B. cepacia with the VITEK2 system were isolated from two medical centers in Mexico City and analyzed by MLSA, BOX-PCR and genome analysis. The initial identification of B. cepacia was confirmed for many strains, but B. contaminans, B. multivorans and B. vietnamiensis were also identified among clinical strains for the first time in hospitals in Mexico. Additionally, the presence of B. pseudomallei was confirmed, and a novel species within the B. cepacia complex was documented. Several strains misidentified as B. cepacia actually belong to the genera Pseudomonas, Stenotrophomonas and Providencia.Conclusions/SignificanceThe presence of different Burkholderia species in Mexico was confirmed. Correct identification of Burkholderia species is important to provide accurate treatment for immunosuppressed patients.     

Immune Checkpoints of the B7 Family. Part 2. Representatives of the B7 Family B7-H3, B7-H4, B7-H5, B7-H6, B7-H7, and ILDR2 and Their Receptors

Russian Journal of Bioorganic Chemistry - Immune checkpoints regulate polarity, strength, and termination of the immune response. The leading roles in these processes are played by molecules of the...     

B5, a new B cell-restricted activation antigen

The characterization of a new human B cell-restricted activation antigen (B5) is described in this report. With the use of a monoclonal antibody to B5, we show that B5 can be detected on peripheral blood or splenic B cells after 1 day of stimulation with either anti-immunoglobulin, protein A, Epstein Barr virus, or pokeweed mitogen. In contrast, B5 was not expressed on resting B, T, or myeloid cells. More important, B5 could not be detected on activated T cells or monocytes. The B5 antigen was expressed on some lymphoblastoid B cell lines and B cell neoplasms but was not expressed on leukemias or lymphomas of T or myeloid origin. The B5 antigen is distinct from previously reported B cell activation antigens by its m.w. and pattern of cellular expression. These studies suggest that B5 is a novel B cell-restricted activation antigen, which may be useful to study the events of early human B cell activation.     

Antigenic, immunologic and genetic characterization of rough strains B. abortus RB51, B. melitensis B115 and B. melitensis B18

The lipopolysaccharide (LPS) is considered the major virulent factor in Brucella spp. Several genes have been identified involved in the synthesis of the three LPS components: lipid A, core and O-PS. Usually, Brucella strains devoid of O-PS (rough mutants) are less virulent than the wild type and do not induce undesirable interfering antibodies. Such of them proved to be protective against brucellosis in mice. Because of these favorable features, rough strains have been considered potential brucellosis vaccines. In this study, we evaluated the antigenic, immunologic and genetic characteristics of rough strains B. abortus RB51, B. melitensis B115 and B. melitensis B18. RB51 derived from B. abortus 2308 virulent strain and B115 is a natural rough strain in which the O-PS is present in the cytoplasm. B18 is a rough rifampin-resistan mutant isolated in our laboratory. The surface antigenicity of RB51, B115 and B18 was evaluated by testing their ability to bind antibodies induced by rough or smooth Brucella strains. The antibody response induced by each strain was evaluated in rabbits. Twenty-one genes, involved in the LPS-synthesis, were sequenced and compared with the B. melitensis 16M strain. The results indicated that RB51, B115 and B18 have differences in antigenicity, immunologic and genetic properties. Particularly, in B115 a nonsense mutation was detected in wzm gene, which could explain the intracellular localization of O-PS in this strain. Complementation studies to evaluate the precise role of each mutation in affecting Brucella morphology and its virulence, could provide useful information for the assessment of new, attenuated vaccines for brucellosis.     

Production of Beauvericin, Moniliformin, Fusaproliferin, and Fumonisins B1, B2, and B3 by Fifteen Ex-Type Strains of Fusarium Species

Fifteen Fusarium species were analyzed by high-performance liquid chromatography for the production of six mycotoxins in corn grits cultures. Production of mycotoxins ranged from 66 to 2,500 μg/kg for fumonisin B₁, 0.6 to 1,500 μg/g for moniliformin, 2.2 to 720 μg/g for beauvericin, and 12 to 130 μg/g for fusaproliferin. Fumonisin B₂ (360 μg/kg) was produced by two species, fumonisin B₃ was not detected in any of the 15 species examined, and Fusarium bulbicola produced none of the six mycotoxins that we analyzed.     

Emericella astellata, a new producer of aflatoxin B, B and sterigmatocystin

AIMS: To report on aflatoxin B(1) and B(2) production from a species of Emericella. METHODS AND RESULTS: Aflatoxins and sterigmatocystin were determined by high-pressure liquid chromatography (HPLC) with diode array detection and confirmed by HPLC with mass spectrometry detection. Among 30 known species of Emericella only one species produced aflatoxin. Strains originating from the same geographical source material had different patterns of aflatoxin and sterigmatocystin production on different media, indicating that epigenetic factors may be involved in the regulation of aflatoxin production. However, two cultures from the same original genet were very similar. CONCLUSIONS: Emericella astellata can produce small amounts of sterigmatocystin and aflatoxin B(1) and B(2). SIGNIFICANCE AND IMPACT OF THE STUDY: Emericella has been used extensively in genetic studies and therefore the isolates producing aflatoxin can be used to elucidate the genetic, evolutionary and maybe ecological role of aflatoxins using molecular genetic methods.     

Immune Checkpoints of the B7 Family. Part 1. General Characteristics and First Representatives: B7-1, B7-2, B7-H1, B7-H2, and B7-DC

Russian Journal of Bioorganic Chemistry - T-cell response along with humoral response compose the basis of acquired immunity. Effective activation of T lymphocytes requires at least two signals....     

Lamin A, lamin B, and lamin B receptor analogues in yeast

Previous studies have shown that turkey erythrocyte lamin B is anchored to the nuclear envelope via a 58-kD integral membrane protein termed p58 or lamin B receptor (Worman H. J., J. Yuan, G. Blobel, and S. D. Georgatos. 1988. Proc. Natl. Acad. Sci. USA. 85:8531-8534). We now identify a p58 analogue in the yeast Saccharomyces cerevisiae. Turkey erythrocyte lamin B binds to yeast urea-extracted nuclear envelopes with high affinity, associating predominantly with a 58-kD polypeptide. This yeast polypeptide is recognized by polyclonal antibodies against turkey p58, partitions entirely with the nuclear fraction, remains membrane bound after urea extraction of the nuclear envelopes, and is structurally similar to turkey p58 by peptide mapping criteria. Using polyclonal antibodies against turkey erythrocyte lamins A and B, we also identify two yeast lamin forms. The yeast lamin B analogue has a molecular mass of 66 kD and is structurally related to erythrocyte lamin B. Moreover, the yeast lamin B analogue partitions exclusively with the nuclear envelope fraction, is quantitatively removed from the envelopes by urea extraction, and binds to turkey lamin A and vimentin. As many higher eukaryotic lamin B forms, the yeast analogue is chemically heterogeneous comprising two serologically related species with different charge characteristics. Antibodies against turkey lamin A detect a 74-kD yeast protein, slightly larger than the turkey lamin A. It is more abundant than the yeast lamin B analogue and partitions between a soluble cytoplasmic fraction and a nuclear envelope fraction. The yeast lamin A analogue can be extracted from the nuclear envelope by urea, shows structural similarity to turkey and rat lamin A, and binds to isolated turkey lamin B. These data indicate that analogues of typical nuclear lamina components (lamins A and B, as well as lamin B receptor) are present in yeast and behave as their vertebrate counterparts.     

Biosynthetic relationship among aflatoxins B1, B2, M1, and M2

Aflatoxins are a family of toxic, acetate-derived decaketides that arise biosynthetically through polyhydroxyanthraquinone intermediates. Most studies have assumed that aflatoxin B1 is the biosynthetic precursor of the other aflatoxins. We used a strain of Aspergillus flavus which accumulates aflatoxin B2 to investigate the later stages of aflatoxin biosynthesis. This strain produced aflatoxins B2 and M2 but no detectable aflatoxin B1 when grown over 12 days in a low-salt, defined growth medium containing asparagine. Addition of dichlorvos to this growth medium inhibited aflatoxin production with concomitant accumulation of versiconal hemiacetal acetate. When mycelial pellets were grown for 24, 48, and 72 h in growth medium and then transferred to a replacement medium, only aflatoxin B2 and M2 were recovered after 96 h of incubation. Addition of sterigmatocystin to the replacement medium led to the recovery of higher levels of aflatoxins B2 and M2 than were detected in control cultures, as well as to the formation of aflatoxins B1 and M1 and O-methylsterigmatocystin. These results support the hypothesis that aflatoxins B1 and B2 can arise independently via a branched pathway.     

Biosynthetic relationship among aflatoxins B1, B2, G1, and G2

Aspergillus parasiticus NIAH-26, a UV-irradiated mutant of A. parasiticus SYS-4 (NRRL 2999), produces neither aflatoxins nor precursors. When sterigmatocystin (ST) or O-methylsterigmatocystin was fed to this mutant in YES medium, aflatoxins B1 (AFB1) and G1 (AFG1) were produced. When dihydrosterigmatocystin (DHST) or dihydro-O-methylsterigmatocystin was fed to this mold, aflatoxins B2 (AFB2) and G2 (AFG2) were produced. The reactions from ST to AFB1 and DHST to AFB2 were also observed in the cell-free system and were catalyzed stepwise by the methyltransferase and oxidoreductase enzymes. In the feeding experiments of strain NIAH-26, the convertibility from ST to AFB1-AFG1 was found to be remarkably suppressed by the coexistence of DHST in the medium, and the convertibility from DHST to AFB2-AFG2 was also suppressed by the presence of ST. When some other mutants which endogenously produce a small amount of aflatoxins (mainly AFB1 and AFG1) were cultured with DHST, the amounts of AFB1 and AFG1 produced were significantly decreased, whereas AFB2 and AFG2 were newly produced. In similar feeding experiments in which 27 kinds of mutants including these mutants were used, most of the mutants which were able to convert exogenous ST to AFB1-AFG1 were also found to convert exogenous DHST to AFB2-AFG2. These results suggest that the same enzymes may be involved in the both biosynthetic pathways from ST to AFB1-AFG1 and DHST to AFB2-AFG2. The reactions described herein were not observed when the molds had been cultured in the YEP medium.     

Soluble, prolonged-acting insulin derivatives. II. Degree of protraction and crystallizability of insulins substituted in positions A17, B8, B13, B27 and B30

It has previously been found that insulins, to which positive charge has been added by substitutions in position B30, thus raising the isoelectric point towards pH 7, had a prolonged action when injected as slightly acidic solutions because such derivatives crystallize very readily upon neutralization. Positive charge has now been added by substituting the B13 and A17 glutamic acid residues with glutamines and B27 threonine with lysine or arginine. These substitutions were introduced by site-specific mutagenesis in a gene coding for a single-chain insulin precursor. By tryptic transpeptidation the single-chain precursors were transformed to the double-chain insulin structure, concomitantly with incorporation of residue B30. Thus insulins combining B13 glutamine, A17 glutamine and B27 lysine or arginine with B30 threonine, threonine amide or lysine amide were synthesized. The time course of blood glucose lowering effect and the absorption were studied after subcutaneous injection in rabbits and pigs. The prolonged action of B30-substituted insulins was markedly enhanced by B27 lysine or arginine substitutions and by B13 glutamine. The B27 residue is located on the surface of the hexamer, so a basic residue in this position presumably promotes the packing of hexamers at neutral pH. The B13 residues cluster in the centre of the hexamer. When the electrostatic repulsive forces from six glutamic acid residues are abolished by substitution with glutamine, a stabilization of the hexamer can be envisaged.(ABSTRACT TRUNCATED AT 250 WORDS)