Biomedical subjects

Peter F Barnes

Publications and source records attributed to Peter F Barnes.

24 records · Page 2Linked to original sources

PubMed2002

Multiple Chlamydia pneumoniae antigens prime CD8+ Tc1 responses that inhibit intracellular growth of this vacuolar pathogen.

CD8(+) T cells play an essential role in immunity to Chlamydia pneumoniae (Cpn). However, the target Ags recognized by Cpn-specific CD8(+) T cells have not been identified, and the mechanisms by which this T cell subset contributes to protection remain unknown. In this work we demonstrate that Cpn infection primes a pathogen-specific CD8(+) T cell response in mice. Eighteen H-2(b) binding peptides representing sequences from 12 Cpn Ags sensitized target cells for MHC class I-restricted lysis by CD8(+) CTL generated from the spleens and lungs of infected mice. Peptide-specific IFN-gamma-secreting CD8(+) T cells were present in local and systemic compartments after primary infection, and these cells expanded after pathogen re-exposure. CD8(+) T cell lines to the 18 Cpn epitope-bearing peptides were cytotoxic, displayed a memory phenotype, and secreted IFN-gamma and TNF-alpha, but not IL-4. These CTL lines lysed Cpn-infected macrophages, and the lytic activity was inhibited by brefeldin A, indicating endogenous processing of CTL Ags. Finally, Cpn peptide-specific CD8(+) CTL suppressed chlamydial growth in vitro by direct lysis of infected cells and by secretion of IFN-gamma and other soluble factors. These studies provide information on the mechanisms by which CD8(+) CTL protect against Cpn, furnish the tools to investigate their possible role in immunopathology, and lay the foundation for future work to develop vaccines against acute and chronic Cpn infections.

Animals↗

PubMed2002

Transmission dynamics of tuberculosis in Tarrant county, Texas.

To understand the transmission dynamics of tuberculosis in Tarrant County, Texas, we performed a population-based study of 159 patients with culture-proven tuberculosis, combining restriction fragment length polymorphism (RFLP) analysis of Mycobacterium tuberculosis isolates with prospective interviewing to identify epidemiologic links between patients. Patients whose isolates had identical or closely related RFLP patterns were considered a cluster. Seventy-six (48%) of 159 patients were in 19 clusters, suggesting that recent transmission accounted for 36% of tuberculosis morbidity. Unconditional logistic regression showed that birth in the United States, continuous residence in Tarrant County, a history of homelessness, and a history of visiting or working in bars were independent predictors of clustering. Four homeless shelters and five bars were associated with specific clusters, suggesting that they were sites of tuberculosis transmission. Patients in some clusters recognized more photographs of patients in their cluster than did patients outside their cluster. We conclude that (1) homeless shelters and bars are important sites of tuberculosis transmission in Tarrant County, and (2) the use of photograph recognition of patients with tuberculosis, in combination with RFLP analysis, has the potential to enhance tuberculosis control by facilitating identification of epidemiologic links between patients.

Adult↗

PubMed2002

The NKp46 receptor contributes to NK cell lysis of mononuclear phagocytes infected with an intracellular bacterium.

We used human tuberculosis as a model to investigate the role of NK cytotoxic mechanisms in the immune response to intracellular infection. Freshly isolated NK cells and NK cell lines from healthy donors lysed Mycobacterium tuberculosis-infected monocytes to a greater extent than uninfected monocytes. Lysis of infected monocytes was associated with increased expression of mRNA for the NKp46 receptor, but not the NKp44 receptor. Antisera to NKp46 markedly inhibited lysis of infected monocytes. NK cell-mediated lysis was not due to reduced expression of MHC class I molecules on the surface of infected monocytes or to enhanced production of IL-18 or IFN-gamma. NK cell lytic activity against M. tuberculosis-infected monocytes and NKp46 mRNA expression were reduced in tuberculosis patients with ineffective immunity to M. tuberculosis compared with findings in healthy donors. These observations suggest that 1) the NKp46 receptor participates in NK cell-mediated lysis of cells infected with an intracellular pathogen, and 2) the reduced functional capacity of NK cells is associated with severe manifestations of infectious disease.

Cell Line↗

PubMed2002

Reduced expression of nuclear cyclic adenosine 5'-monophosphate response element-binding proteins and IFN-gamma promoter function in disease due to an intracellular pathogen.

Mycobacterium tuberculosis-induced IFN-gamma protein and mRNA expression have been shown to be reduced in tuberculosis patients, compared with healthy tuberculin reactors. To determine whether this decrease was associated with reduced activity of the IFN-gamma promoter, we first studied binding of nuclear proteins to the radiolabeled proximal IFN-gamma promoter (-71 to -40 bp), using EMSAs with nuclear extracts of freshly isolated peripheral blood T cells. Nuclear extracts of T cells from most tuberculosis patients showed markedly reduced expression of proteins that bind to the proximal IFN-gamma promoter, compared with findings in nuclear extracts of T cells from healthy tuberculin reactors. These DNA-binding complexes contained CREB proteins, based on competitive EMSAs, supershift assays, and Western blotting with an anti-CREB Ab. Transient transfection of PBLs with a luciferase reporter construct under the control of the IFN-gamma promoter revealed reduced IFN-gamma promoter activity in tuberculosis patients. Transient transfection of Jurkat cells with a dominant-negative CREB repressor plasmid reduced IFN-gamma promoter activity. These data suggest that reduced expression of CREB nuclear proteins in tuberculosis patients results in decreased IFN-gamma promoter activity and reduced IFN-gamma production.

Consensus Sequence↗

PubMed2002

Tuberculosis in patients with HIV infection.

In the past 5 years, there have been significant advances in the understanding of the pathogenesis of TB in people infected with HIV and in the approach to diagnosis, treatment, and prevention in patients with HIV. Nucleic acid amplification tests and restriction fragment length polymorphism can contribute to the clinical management of TB patients. New guidelines are available for the treatment of active and latent TB infection in patients with HIV.

HIV Infections↗

PubMed2002

Priming reverse transcription with oligo(dT) does not yield representative samples of Mycobacterium tuberculosis cDNA.

Several recent publications have suggested that oligo(dT) can prime reverse transcription of several mycobacterial mRNAs. To determine if this is the case for most Mycobacterium tuberculosis mRNA species, reverse transcription reactions of M. tuberculosis RNA were primed with oligo(dT) or with other primers that did not target polyadenylylated sequences, and the resultant cDNA product was evaluated. Priming with oligo(dT) yielded more cDNA than priming with an arbitrary primer for only 1 of 12 unrelated M. tuberculosis genes, as measured by competitive PCR. Priming with oligo(dT) yielded cDNA for only 30% of the genes primed for by 37 M. tuberculosis genome-directed oligonucleotides, as assessed by hybridization of cDNA with an M. tuberculosis microarray. These data demonstrate that priming of reverse transcription of mycobacterial mRNA with oligo(dT) does not yield representative samples of cDNA.

DNA Primers↗