Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Allelic MHC Class I Chain Related B (MICB) Molecules Affect the Binding to the Human Cytomegalovirus (HCMV) Unique Long 16 (UL16) Protein: Implications for Immune Surveillance: Kanya Klumkrathok , Amonrat Jumnainsong , Chanvit Leelayuwat; J. Microbiol. 2013;51(2):241-246. Published online April 27, 2013; DOI: https://doi.org/10.1007/s12275-013-2514-1

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Abstract: Unique long 16 (UL16) is a viral glycoprotein produced in a host cell infected with human cytomegalovirus (HCMV). It down regulates surface expression of MICB, one of the NKG2D ligands, by forming stable intracellular complexes and retained in the endoplasmic reticulum. Down expression of MICB renders cells less susceptible to NK cell lysis via the NKG2D receptor. Diverse UL16 sequences were identified from different strains of HCMV. MICB is known to be polymorphic. It is not known whether these polymorphisms affect the interactions between these molecules leading to alteration of the immune surveillance of HCMV. The soluble Fc fusion variant UL16 proteins from four laboratory and clinical isolates (AD169, Toledo, PH, and TR) were produced. Four allelic MICB alleles (008, 003, 004, and 00502) were cloned and stable cell lines expressing these MICB alleles were produced. The binding activities of variant UL16 to allelic MICB proteins were determined by flow cytometry. The variants of UL16 proteins did not affect the binding activities to allelic MICB proteins. However, diverse MICB alleles differentially bound UL16. We found that MICB*008 which contains methionine and asparagine at the amino acid positions 98 and 113, respectively, in the alpha 2 domain showed decreased binding activities to UL16 when compared to MICB*003, 004, and MICB*00502 containing isoleucine and aspartic acid, respectively. This finding may imply that MICB*008 is a protective allele and involved in the immune surveillance of HCMV infected patients.

Secretion of Truncated Recombinant Rabies Virus Glycoprotein with Preserved Antigenic Properties Using a Co-Expression System in Hansenula polymorpha: Weidong Qian , Frank Aguilar , Ting Wang , Bingsheng Qiu; J. Microbiol. 2013;51(2):234-240. Published online April 27, 2013; DOI: https://doi.org/10.1007/s12275-013-2337-0

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Abstract: Rabies virus infection remains a serious public health threat in the developing world, where cost-concerns make widescale public health interventions impractical. The development of novel and inexpensive ELISA diagnostic antigens is critical in early detection and prevention of complications. The transmembrane glycoprotein (G) of rabies virus (RV) contains an external domain capable of inducing the synthesis of anti-rabies, virus-neutralizing antibodies, in infected or immunized hosts. In our study, the external G domain was synthesized and fused in-frame with a polyhistidine-tag coding sequence present in the expression plasmid. Soluble truncated recombinant G was secreted in Hansenula polymorpha (H. polymorpha) using H. polymorpha-derived calnexin (HpCNE1) overproduction and found to be correctly N-glycosylated. The truncated recombinant G was purified from cell culture supernatant by Ni-agarose affinity chromatography and when compared with the full-length glycoprotein, found to be similarly immunogenic in vaccinated rabbits. These results subsequently led us to explore the potential of truncated recombinant G as a diagnostic antigen in ELISA. Our results show that the truncated recombinant G can detect antibodies directed to both whole virion and native glycoprotein. More sophisticated applications of truncated recombinant G would profit from the correctly N-glycosylated and soluble monomer.

NOTE] Envelope Diversity, Characteristics of V3 Region and Predicted Co-Receptor Usage of Human Immunodeficiency Viruses Infecting North Indians: Raiees Andrabi , Rajesh Kumar , Manju Bala , Ambili Nair , Prakash SS , Vandana Kushwaha , Kalpana Luthra; J. Microbiol. 2012;50(5):869-873. Published online November 4, 2012; DOI: https://doi.org/10.1007/s12275-012-2136-z

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Abstract: Subtypes of human immunodeficiency virus type 1 circulating in 21 north Indian patients were characterized based on the partial sequence of the gp120 envelope protein. A majority of viruses (85.7%, 18/21) were subtype C, while 14.3% (3/21) were subtype A. Sequence analysis revealed that the V3 region was highly conserved compared with V4 and V5. The predicted use of co-receptors indicated exclusive usage of R5, except for two subtype A viruses (AIIMS279 and AIIMS281). Our results demonstrate conservation within the V3 loop of subtype C viruses, and suggest the emergence of non-clade C viruses in the north Indian population.

Effect of Glycosylation on the Biochemical Properties of beta-Xylosidases from Aspergillus versicolor: Alexandre Favarin Somera , Marita Gimenez Pereira , Luis Henrique Souza Guimaraes , Maria de Lourdes Teixeira de Moraes Polizeli , Hector Francisco Terenzi , Rosa Prazeres Melo Furriel , Joao Atilio Jorge; J. Microbiol. 2009;47(3):270-276. Published online June 26, 2009; DOI: https://doi.org/10.1007/s12275-008-0286-9

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Abstract: Aspergillus versicolor grown on xylan or xylose produces two beta-xylosidases with differences in biochemical properties and degree of glycosylation. We investigated the alterations in the biochemical properties of these beta-xylosidases after deglycosylation with Endo-H or PNGase F. After deglycosylation, both enzymes migrated faster in PAGE or SDS-PAGE exhibiting the same Rf. Temperature optimum of xylan-induced and xylose-induced beta-xylosidases was 45oC and 40oC, respectively, and 35oC after deglycosylation. The xylan- induced enzyme was more active at acidic pH. After deglycosylation, both enzymes had the same pH optimum of 6.0. Thermal resistance at 55oC showed half-life of 15 min and 9 min for xylose- and xylan-induced enzymes, respectively. After deglycosylation, both enzymes exhibited half-lives of 7.5 min. Native enzymes exhibited different responses to ions, while deglycosylated enzymes exhibited identical responses. Limited proteolysis yielded similar polypeptide profiles for the deglycosylated enzymes, suggesting a common polypeptide core with differential glycosylation apparently responsible for their biochemical and biophysical differences.

Defining the N-Linked Glycosylation Site of Hantaan Virus Envelope Glycoproteins Essential for Cell Fusion: Feng Zheng , Lixian Ma , Lihua Shao , Gang Wang , Fengzhe Chen , Ying Zhang , Song Yang; J. Microbiol. 2007;45(1):41-47.; DOI: https://doi.org/2493 [pii]

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Abstract: The Hantaan virus (HTNV) is an enveloped virus that is capable of inducing low pH-dependent cell fusion. We molecularly cloned the viral glycoprotein (GP) and nucleocapsid (NP) cDNA of HTNV and expressed them in Vero E6 cells under the control of a CMV promoter. The viral gene expression was assessed using an indirect immunofluorescence assay and immunoprecipitation. The transfected Vero E6 cells expressing GPs, but not those expressing NP, fused and formed a syncytium following exposure to a low pH. Monoclonal antibodies (MAbs) against envelope GPs inhibited cell fusion, whereas MAbs against NP did not. We also investigated the N-linked glycosylation of HTNV GPs and its role in cell fusion. The envelope GPs of HTNV are modified by N-linked glycosylation at five sites: four sites on G1 (N134, N235, N347, and N399) and one site on G2 (N928). Site-directed mutagenesis was used to construct eight GP gene mutants, including five single N-glycosylation site mutants and three double-site mutants, which were then expressed in Vero E6 cells. The oligosaccharide chain on residue N928 of G2 was found to be crucial for cell fusion after exposure to a low pH. These results suggest that G2 is likely to be the fusion protein of HTNV.

Production and Characterization of Monoclonal Antibodies to Human Immunodeficiency Virus Type 1 gp120 Envelope Glycoprotein: Choi, Eui Yul , Ryu, Ji Yoon , Lee, Yoon , Ha, Sung Gil , Chung, So Young , Park, Sang Yeol , Nham, Sang Uk , Lee, Young Ik , Park, Jin Seu; J. Microbiol. 1998;36(1):59-65.

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Abstract: Monoclonal antibodies to human immunodeficiency virus type 1 envelope glycoprotein gp 120(HIV-1 gp120) were produced and characterized. For immunogen recombinant gp120 polypeptide expressed in bacteria was prepared and injected into mice. From two fusion experiments, twenty hybridomas secreting monoclonal antibodies against the recombinant gp120 were initially screened by immunodot blot analysis. Among the antibodies, 15 of them showed strong reactivities with the recombinant protein expressed in bacteria in Western blot and thus it was tested if these could react with the recombinant protein expressed in insect cells. All of the 15 antibodies immunostained the protein band with varing degrees of reactivities. Next, we tested whether the antibodies recognize authentic gp120 protein expressed in mammalian cells. COS-1 cells were tranfected with the cDNA encoding gp120 protein, and the transiently ecpressed protein were analyzed with the mAbs by Western blot analysis and immunofluorescence microscopy. Six of the monoclonal antibodies reacted with the protein band of authentic gp120 expressed in mammalian cells in the Western blot, and five stained the cell periphery of the transfected COS-1 cells in immunofluorescence. The mAbs described in this study should prove to be useful tools for the biochemical, immunological and structural analysis of HIV-1 gp120 envelope glycoprotein.

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