title: Variation of the expression of Mycobacterium tuberculosis ppe44 gene among clinical isolates.
abstract: PPE44 is a member of the Mycobacterium tuberculosis PPE proteins, a polymorphic family of 69 glycine-rich proteins that predictively represent a source of antigenic variation. The genetic diversity of gene ppe44 among clinical isolates has been studied. No genomic polymorphism of ppe44 was found by a PCR-restriction fragment length polymorphism assay using three restriction enzymes. Nucleotide sequencing of gene ppe44 of a number of isolates, selected to represent the major phylogenetic lineages of M. tuberculosis, showed no nucleotide substitution, with the exception of isolates of the Beijing genotype. These findings indicate that gene ppe44 is basically conserved among M. tuberculosis strains. The expression of gene ppe44 was then determined at the transcriptional level by a real-time reverse transcriptase PCR assay. Extremely high quantitative variations in ppe44 expression were found among the isolates; ppe44 expression of the Beijing strains was significantly higher than the non-Beijing strains. To test whether differential expression of gene ppe44 has the potential to provide a dynamic antigen display, antibodies to PPE44 were titered in the sera of M. tuberculosis-infected subjects. Variation of antibody response to PPE44 was found with regard to both antibody titers and the proportion of responding subjects. These results indicate that the differential expression of genes ppe could influence the host's immune responsiveness, thus having implications in the immunopathogenesis of tuberculosis.
authors.affiliation: Dipartimento di Patologia Sperimentale, Biotecnologie Mediche, Infettivologia ed Epidemiologia, Università di Pisa, Pisa, Italy. rindi@biomed.unipi.it
authors.forename: Laura
authors.initials: L
authors.lastname: Rindi
authors.forename: Irene
authors.initials: I
authors.lastname: Peroni
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Lari
authors.forename: Daniela
authors.initials: D
authors.lastname: Bonanni
authors.forename: Enrico
authors.initials: E
authors.lastname: Tortoli
authors.forename: Carlo
authors.initials: C
authors.lastname: Garzelli
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D001426:Bacterial Proteins / Q000096:biosynthesis; D017124:Conserved Sequence; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D014644:Genetic Variation; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014376:Tuberculosis / Q000382:microbiology*
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D004269:DNA, Bacterial; C524728:PPE44 protein, Mycobacterium tuberculosis; D012329:RNA, Bacterial; D012333:RNA, Messenger