Skip to main content
PMC home page
The EMBO Journal logoLink to The EMBO Journal
. 1991 Jul;10(7):1653–1659. doi: 10.1002/j.1460-2075.1991.tb07688.x

Exposed epitopes on a Trypanosoma equiperdum variant surface glycoprotein altered by point mutations.

T Baltz 1, C Giroud 1, F Bringaud 1, H Eisen 1, C Jacquemot 1, C W Roth 1
PMCID: PMC452835  PMID: 1710978

Abstract

African trypanosomes are covered by a dense protein layer that is immunologically distinct on different trypanosome isolates and is termed the variant surface glycoprotein (VSG). The different VSGs are expressed in a general order, where some VSGs appear preferentially early in infection and others only later. The exposed epitopes on a late antigen, VSG 78, of T.equiperdum were studied by the technique of monoclonal antibody (MAb) escape selection. MAbs that neutralize trypanosomes bearing VSG 78 reacted with the VSG only when it was attached to the trypanosome surface, suggesting that the most immunogenic surface epitopes are conformational. Trypanosome clones resistant to one of the MAbs yet still expressing VSG 78 or 78(20) were isolated in vitro. Two independent variants resistant to MAb H3 changed Ser192 to Arg by a single base change in the VSG gene and a variant resistant to MAb H21 had a single base change that converted Gln172 to Glu. A variant resistant to MAb H7 had several changes in the VSG gene, a gene conversion in the 5' region and an isolated mutation in codon 220 that is proposed to be responsible for the resistance phenotype. The isotypic bias of the MAbs against VSG 78 and an analysis of the natural variants that are resistant to MAb 78H21 suggest that glycosylation plays a role in the immunogenicity of these proteins. The analysis defines some of the exposed amino acid residues and demonstrates that VSG genes are altered by mutations and small gene conversions as well as replaced by large gene conversion-like events. The results provide biological data supporting the model of VSG structure obtained by crystallographic studies.

Full text

PDF

Images in this article

1654Image
on p.1654

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Baltz T., Baltz D., Giroud C., Crockett J. Cultivation in a semi-defined medium of animal infective forms of Trypanosoma brucei, T. equiperdum, T. evansi, T. rhodesiense and T. gambiense. EMBO J. 1985 May;4(5):1273–1277. doi: 10.1002/j.1460-2075.1985.tb03772.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Baltz T., Baltz D., Pautrizel R. Affinité de la concanavaline A pour Trypanosoma equiperdum applications a l'isolement de la fraction glycoprotéique spécifique du type antigénique. Ann Immunol (Paris) 1976 Sep-Oct;127(5):761–774. [PubMed] [Google Scholar]
  3. Baltz T., Baltz D., Pautrizel R., Richet C., Lamblin G., Degand P. Chemical and immunological characterization of specific glycoproteins from Trypanosoma equiperdum variants. FEBS Lett. 1977 Oct 1;82(1):93–96. doi: 10.1016/0014-5793(77)80893-4. [DOI] [PubMed] [Google Scholar]
  4. Björklund M., Coutinho A. Isotype commitment in the in vivo immune responses. II. Polyclonal plaque-forming cell responses to lipopolysaccharide in the spleen and bone marrow. Eur J Immunol. 1983 Jan;13(1):44–50. doi: 10.1002/eji.1830130111. [DOI] [PubMed] [Google Scholar]
  5. Borst P., Greaves D. R. Programmed gene rearrangements altering gene expression. Science. 1987 Feb 6;235(4789):658–667. doi: 10.1126/science.3544215. [DOI] [PubMed] [Google Scholar]
  6. Capbern A., Giroud C., Baltz T., Mattern P. Trypanosoma equiperdum: etude des variations antigéniques au cours de la trypanosomose experimentale du lapin. Exp Parasitol. 1977 Jun;42(1):6–13. doi: 10.1016/0014-4894(77)90055-8. [DOI] [PubMed] [Google Scholar]
  7. Clarke M. W., McCubbin W. D., Kay C. M., Pearson T. W. Physical studies of Trypanosoma brucei variant surface glycoproteins and their antigenic determinants. Biochemistry. 1988 Jan 12;27(1):405–413. doi: 10.1021/bi00401a061. [DOI] [PubMed] [Google Scholar]
  8. Donelson J. E., Rice-Ficht A. C. Molecular biology of trypanosome antigenic variation. Microbiol Rev. 1985 Jun;49(2):107–125. doi: 10.1128/mr.49.2.107-125.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Freymann D. M., Metcalf P., Turner M., Wiley D. C. 6 A-resolution X-ray structure of a variable surface glycoprotein from Trypanosoma brucei. Nature. 1984 Sep 13;311(5982):167–169. doi: 10.1038/311167a0. [DOI] [PubMed] [Google Scholar]
  10. Freymann D., Down J., Carrington M., Roditi I., Turner M., Wiley D. 2.9 A resolution structure of the N-terminal domain of a variant surface glycoprotein from Trypanosoma brucei. J Mol Biol. 1990 Nov 5;216(1):141–160. doi: 10.1016/S0022-2836(05)80066-X. [DOI] [PubMed] [Google Scholar]
  11. Jähnig F., Bülow R., Baltz T., Overath P. Secondary structure of the variant surface glycoproteins of trypanosomes. FEBS Lett. 1987 Aug 31;221(1):37–42. doi: 10.1016/0014-5793(87)80348-4. [DOI] [PubMed] [Google Scholar]
  12. Laurent M., Pays E., Van der Werf A., Aerts D., Magnus E., Van Meirvenne N., Steinert M. Translocation alters the activation rate of a trypanosome surface antigen gene. Nucleic Acids Res. 1984 Nov 26;12(22):8319–8328. doi: 10.1093/nar/12.22.8319. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Longacre S., Eisen H. Expression of whole and hybrid genes in Trypanosoma equiperdum antigenic variation. EMBO J. 1986 May;5(5):1057–1063. doi: 10.1002/j.1460-2075.1986.tb04322.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Marck C. 'DNA Strider': a 'C' program for the fast analysis of DNA and protein sequences on the Apple Macintosh family of computers. Nucleic Acids Res. 1988 Mar 11;16(5):1829–1836. doi: 10.1093/nar/16.5.1829. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Metcalf P., Blum M., Freymann D., Turner M., Wiley D. C. Two variant surface glycoproteins of Trypanosoma brucei of different sequence classes have similar 6 A resolution X-ray structures. Nature. 1987 Jan 1;325(6099):84–86. doi: 10.1038/325084a0. [DOI] [PubMed] [Google Scholar]
  16. Pays E., Houard S., Pays A., Van Assel S., Dupont F., Aerts D., Huet-Duvillier G., Gomés V., Richet C., Degand P. Trypanosoma brucei: the extent of conversion in antigen genes may be related to the DNA coding specificity. Cell. 1985 Oct;42(3):821–829. doi: 10.1016/0092-8674(85)90278-8. [DOI] [PubMed] [Google Scholar]
  17. Pays E., Steinert M. Control of antigen gene expression in African trypanosomes. Annu Rev Genet. 1988;22:107–126. doi: 10.1146/annurev.ge.22.120188.000543. [DOI] [PubMed] [Google Scholar]
  18. Pays E., Van Assel S., Laurent M., Darville M., Vervoort T., Van Meirvenne N., Steinert M. Gene conversion as a mechanism for antigenic variation in trypanosomes. Cell. 1983 Sep;34(2):371–381. doi: 10.1016/0092-8674(83)90371-9. [DOI] [PubMed] [Google Scholar]
  19. Perlmutter R. M., Hansburg D., Briles D. E., Nicolotti R. A., Davie J. M. Subclass restriction of murine anti-carbohydrate antibodies. J Immunol. 1978 Aug;121(2):566–572. [PubMed] [Google Scholar]
  20. Reinwald E., Greiser-Wilke I., Artama W., Risse H. J., Mölling K. Characterization of epitopes on a variant surface glycoprotein from Trypanosoma congolense by six monoclonal antibodies. Eur J Biochem. 1987 Sep 15;167(3):525–532. doi: 10.1111/j.1432-1033.1987.tb13369.x. [DOI] [PubMed] [Google Scholar]
  21. Roth C. W., Longacre S., Raibaud A., Baltz T., Eisen H. The use of incomplete genes for the construction of a Trypanosoma equiperdum variant surface glycoprotein gene. EMBO J. 1986 May;5(5):1065–1070. doi: 10.1002/j.1460-2075.1986.tb04323.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Roth C., Bringaud F., Layden R. E., Baltz T., Eisen H. Active late-appearing variable surface antigen genes in Trypanosoma equiperdum are constructed entirely from pseudogenes. Proc Natl Acad Sci U S A. 1989 Dec;86(23):9375–9379. doi: 10.1073/pnas.86.23.9375. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Sanger F., Nicklen S., Coulson A. R. DNA sequencing with chain-terminating inhibitors. Proc Natl Acad Sci U S A. 1977 Dec;74(12):5463–5467. doi: 10.1073/pnas.74.12.5463. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Sherry B., Mosser A. G., Colonno R. J., Rueckert R. R. Use of monoclonal antibodies to identify four neutralization immunogens on a common cold picornavirus, human rhinovirus 14. J Virol. 1986 Jan;57(1):246–257. doi: 10.1128/jvi.57.1.246-257.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Wei G., Qualtiere L., Tabel H. Trypanosoma congolense: complement independent immobilization by a monoclonal antibody. Exp Parasitol. 1990 May;70(4):483–485. doi: 10.1016/0014-4894(90)90133-w. [DOI] [PubMed] [Google Scholar]
  26. Wiley D. C., Wilson I. A., Skehel J. J. Structural identification of the antibody-binding sites of Hong Kong influenza haemagglutinin and their involvement in antigenic variation. Nature. 1981 Jan 29;289(5796):373–378. doi: 10.1038/289373a0. [DOI] [PubMed] [Google Scholar]

Articles from The EMBO Journal are provided here courtesy of Nature Publishing Group

RESOURCES