The Molecular Biology of Antigenic Variation in Trypanosomes: Gene Rearrangements and Discontinuous Transcription

Abstract

This chapter presents a discussion on the molecular biology of trypanosome antigenic variation. The bloodstream-dwelling African trypanosomes are covered by a homogeneous layer of coat protein, variant surface glycoprotein (VSG), of which antigenically different types can be synthesized during a chronic infection. Every trypanosome may have as many as 1000 genes that code for VSG. The study of transcripts for VSG has uncovered a novel mode of mRNA synthesis that appears to be a general characteristic of the family of Trypanosomatidae. The first 35 nucleotides of many, if not all, mRNAs are the same and not encoded contiguously with the rest of the transcript. All trypanosomes and their allies discussed in the chapter belong to the family of the Trypanosomatidae for a comprehensive treatise on trypanosome biology. They are uniflagellated, parasitic protozoa with a DNA-containing kinetoplast. The trypanosomes that show antigenic variation belong to the section Salivaria of the genus Trypanosoma . Trypanosomes are relatively easy organisms for molecular biologists to study. Trypanosomes can be cloned and maintained in small laboratory rodents, such as mice and rats, or stored under liquid nitrogen. VSG genes can be activated in several ways.