CHARACTERIZATION AND COMPARISON OF FELV-FAIDS RETROVIRUS ENVELOPE GLYCOPROTEINS

Important note: Information in this article was accurate in 1992. The state of the art may have changed since the publication date.

CHARACTERIZATION AND COMPARISON OF FELV-FAIDS RETROVIRUS ENVELOPE GLYCOPROTEINS

Diss Abstr Int [B]; 52(1):56 1991. Unique Identifier : AIDSLINE ICDB/92677103
Poss ML; Colorado State Univ.

Abstract: The envelope glycoprotein (gp70) of a molecularly cloned, replication defective feline leukemia virus (FeLV-FAIDS clone 61C) carries determinants for induction of fatal immunodeficiency disease. An infectious, probable parent genome clone (61E) induces viremia in cats but is minimally pathogenic. These two genomes are 98% homologous with the greatest divergence occurring in env. Although the glycoproteins produced are predicted to be the same length, 61C gp70 is predicted to contain a 6 amino acid deletion and 6 amino acid insertion near the amino and carboxyl terminal ends, respectively, of the glycoprotein. The proteins also differ by eleven single amino acid changes. Envelope chimeras generated between 61C and 61E (prototype EECC) demonstrate that the envelope gene or minimally the carboxyl-terminal 6 amino acid insertion is required for pathogenicity of a chimera. Several features distinguish the glycoproteins of chimera EECC from 61E. Cats immunized with the defective 61C generate antisera that recognizes only EECC glycoproteins. A monoclonal antibody (C5E5) to a transmembrane epitope (p15E) can recognize this epitope only on the envelope precursor (gp80) of EECC. Both gp80 and gp70 from EECC are larger by SDS-PAGE than the corresponding glycoproteins from 61E. Finally, EECC gp80 accumulates intracellularly due to a delay in processing to gp70 and p15E. The unique size and antigenic recognition properties of EECC are glycosylation dependent, since glycoproteins from both viruses produced in cells treated with an inhibitor of N-linked glycosylation, tunicamycin, can be recognized by C5E5 and are the same size. Furthermore, size, antigenic recognition and processing properties that distinguish EECC glycoproteins can be conferred to 61E glycoproteins if infected cells are grown in the presence of glucosidase inhibitors. Mannosidase inhibitors are incapable of reproducing this effect indicating that the earlier step of glucose trimming is likely to be involved in the unique properties of EECC glycoproteins. These distinguishing properties of EECC glycoproteins contribute to lymphocytopathicity, since 61E infected T-cells, normally an apathogenic infection, display cytopathicity if treated with castanospermine, a glucosidase inhibitor. The external glycoproteins from both viruses were purified from column purified virus by anion exchange and reverse phase chromatography. Apparent molecular sizes of the proteins were larger under denaturing conditions (81,000 and 77,100 for EECC and 61E, respectively) than under native conditions (59,000 and 60,600 for EECC and 61E, respectively). The pI determined under native conditions of both glycoproteins was 5.4-5.34. Lectin blots demonstrated that both viral glycoproteins contained high mannose, sialylated and galactosylated oligosaccharide chains. Purified gp70 from EECC was conjugated to FITC to be used for receptor binding studies. Saturation and equilibrium data produced indicated that equilibrium was established in 25 min at 4 C and 1 x 10(4) molecules of gp70-FITC were bound at equilibrium. (Full text available from University Microfilms International, Ann Arbor, MI, as Order No. AAD91-17200).

Keywords: Animal Antibodies, Monoclonal/DIAGNOSTIC USE Cats Defective Viruses/*CHEMISTRY/GENETICS Leukemia Virus, Feline/*CHEMISTRY/GENETICS Membrane Glycoproteins/*ANALYSIS/GENETICS/IMMUNOLOGY Molecular Weight Retroviridae Proteins, Oncogenic/*ANALYSIS/GENETICS/IMMUNOLOGY Viral Envelope Proteins/*ANALYSIS/GENETICS/IMMUNOLOGY THESIS
920228
M9220887

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