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Biomedical subjects

Peter Andersen

Publications and source records attributed to Peter Andersen.

At least 55 records · Page 3Linked to original sources
PubMed2004

Healthy individuals that control a latent infection with Mycobacterium tuberculosis express high levels of Th1 cytokines and the IL-4 antagonist IL-4delta2.

The majority of healthy individuals exposed to Mycobacterium tuberculosis will not develop disease and identifying what constitutes "protective immunity" is one of the holy grails of M. tuberculosis immunology. It is known that IFN-gamma is essential for protection, but it is also apparent that IFN-gamma levels alone do not explain the immunity/susceptibility dichotomy. The controversy regarding correlates of immunity persists because identifying infected but healthy individuals (those who are immune) has been problematic. We have therefore used recognition of the M. tuberculosis virulence factor early secretory antigenic target 6 to identify healthy, but infected individuals from tuberculosis (TB)-endemic and nonendemic regions (Ethiopia and Denmark) and have compared signals for cytokines expressed directly ex vivo with the pattern found in TB patients. We find that TB patients are characterized by decreased levels of Th1 cytokines and increased levels of IL-10 compared with the healthy infected and noninfected community controls. Interestingly, the healthy infected subjects exhibited a selective increase of message for the IL-4 antagonist, IL-4delta2, compared with both TB patients or noninfected individuals. These data suggest that long-term control of M. tuberculosis infection is associated not just with elevated Th1 responses but also with inhibition of the Th2 response.

Adult↗
PubMed2004

Comparison of tuberculin skin test and new specific blood test in tuberculosis contacts.

The tuberculin skin test used to detect latent Mycobacterium tuberculosis infection has many drawbacks, and a new diagnostic test for latent tuberculosis (QuantiFERON-TB [QTF-TB]) has recently been introduced. This test measures the production of IFN-gamma in whole blood upon stimulation with purified protein derivative (PPD). The QTF-TB test addresses the operational problems with the tuberculin skin test, but, as the test is based on PPD, it still has a low specificity in populations vaccinated with the Bacille Calmette-Guérin (BCG) vaccine. We have modified the test to include the antigens ESAT-6 and CFP-10, which are not present in BCG vaccine strains or the vast majority of nontuberculous mycobacteria. This test was used to detect infection in contacts in a tuberculosis outbreak at a Danish high school. The majority of the contacts were BCG-unvaccinated, which allowed a direct comparison of the skin test and the novel blood test in individuals whose skin test was not confounded by vaccination. An excellent agreement between the two tests was found (94%, kappa value 0.866), and in contrast to the blood test based on PPD, the novel blood test was not influenced by the vaccination status of the subjects tested.

Adolescent↗
PubMed2004

Mapping immune reactivity toward Rv2653 and Rv2654: two novel low-molecular-mass antigens found specifically in the Mycobacterium tuberculosis complex.

New tools are urgently needed for the detection of latent tuberculosis (TB). We evaluated the diagnostic potential of 2 novel Mycobacterium tuberculosis complex-specific candidate antigens (Rv2653 and Rv2654) and investigated T cell recognition during natural infection in humans and experimental infection in guinea pigs. Peripheral blood mononuclear cells stimulated with peptide pools covering the full length of Rv2654 induced interferon- gamma release in 10 of 19 patients with TB. Neither Rv2654 single peptides nor Rv2654 pools were recognized by bacille Calmette-Guerin-vaccinated donors. However, peptides from Rv2653 were recognized by both patients group. The cross-reactive epitope(s) in Rv2653 were located in a 36-amino acid stretch in the center of the molecule. Rv2654 also induced M. tuberculosis-specific skin-test responses in 3 of 4 aerosol-infected guinea pigs. Rv2654 is a strongly recognized T cell antigen that is highly specific for TB and has potential as a novel cell-mediated immunity-based TB diagnostic agent.

Animals↗
PubMed2004

Highly resolved in vivo 1H NMR spectroscopy of the mouse brain at 9.4 T.

An efficient shim system and an optimized localization sequence were used to measure in vivo 1H NMR spectra from cerebral cortex, hippocampus, striatum, and cerebellum of C57BL/6 mice at 9.4 T. The combination of automatic first- and second-order shimming (FASTMAP) with strong custom-designed second-order shim coils (shim strength up to 0.04 mT/cm2) was crucial to achieve high spectral resolution (water line width of 11-14 Hz). Requirements for second-order shim strengths to compensate field inhomogeneities in the mouse brain at 9.4 T were assessed. The achieved spectral quality (resolution, S/N, water suppression, localization performance) allowed reliable quantification of 16 brain metabolites (LCModel analysis) from 5-10-microL brain volumes. Significant regional differences (up to 2-fold, P < 0.05) were found for all quantified metabolites but Asp, Glc, and Gln. In contrast, 1H NMR spectra measured from the striatum of C57BL/6, CBA, and CBA/BL6 mice revealed only small (<13%, P < 0.05) interstrain differences in Gln, Glu, Ins, Lac, NAAG, and PE. It is concluded that 1H NMR spectroscopy at 9.4 T can provide precise biochemical information from distinct regions of the mouse brain noninvasively that can be used for monitoring of disease progression and treatment as well as phenotyping in transgenic mice models.

Analysis of Variance↗
PubMed2004

CFP10 discriminates between nonacetylated and acetylated ESAT-6 of Mycobacterium tuberculosis by differential interaction.

ESAT-6 (the 6 kDa early secreted antigenic target) protein species in short-term culture filtrate of Mycobacterium tuberculosis were separated in a 4-5 narrow range pI gradient two-dimensional gel electrophoresis (2-DE). Eight ESAT-6 protein species were analyzed in detail by peptide mass fingerprinting matrix-assisted laser desorption/ionization-mass spectrometry as well as by electrospray ionization-tandem mass spectrometry. An N-terminal Thr acetylation was identified in four species and a C-terminal truncation was identified in two species. In 2-DE blot overlay assays, the recombinant 10 kDa culture filtrate protein (CFP10) discriminated N-terminal acetylated and nonacetylated ESAT-6 by differential interaction, whereas removal of the C-terminal 11 residues of ESAT-6 had no effects thereon. This example shows that the access to the protein species level can be a prerequisite to understand regulation of protein-protein interaction.

Acetylation↗
PubMed2004

ESAT-6 proteins: protective antigens and virulence factors?

The 6kDa early secreted antigenic target from Mycobacterium tuberculosis, ESAT-6, is the prototype of a novel family of small proteins of unknown function produced by Actinobacteria. Export of ESAT-6, a potent T-cell antigen, and related proteins requires a dedicated secretory apparatus that is encoded by a cluster of genes, several of which also code for proteins that are recognized strongly by T cells. ESAT-6 systems can thus be considered as immunogenicity islands and there is growing evidence that the corresponding genes are subject to selective pressure imposed by the immune system of the host. Recently, there has been major progress in understanding the biogenesis, secretion and antigenicity of ESAT-6 proteins and, at least in the case of ESAT-6 system 1, in unravelling their role in pathogenicity. Here, we discuss these findings and their implications for the development of new therapeutic and prophylactic interventions against tuberculosis.

Antigens, Bacterial↗
PubMed2004

TB diagnosis in non-human primates: comparison of two interferon-gamma assays and the skin test for identification of Mycobacterium tuberculosis infection.

In general non-human primates are highly susceptible to infections with Mycobacterium tuberculosis which therefore presents an explosive health threat to colonies. To screen for M. tuberculosis infections in non-human primates, the skin test is routinely used. However, the reliability of this test in primates is debatable. The aim of this study was to compare relatively easy in vitro diagnostic tests for TB with the skin test for detection of a tuberculosis (TB) infection. Two in vitro assays, a whole blood interferon-gamma (WB IFN-gamma) assay and in vitro stimulation of isolated lymphocytes (PBMC IFN-gamma) were evaluated during both experimental TB infections in macaques as well as during an outbreak of TB in a macaque quarantine facility. The WB IFN-gamma assay was also evaluated on healthy old and new world monkeys. Our results show that both in vitro assays detected TB infection in macaques. All experimentally infected animals showed TB-specific responses in both assays. In contrast, several TB animals were not diagnosed TB positive using the skin test. In addition, during the outbreak in the quarantine facility one animal was not detected using the routinely used skin test, but it showed strong positive responses in the WB assay. In conclusion, the in vitro assays are a valuable tool for screening non-human primates for TB infection, especially because the assays cause relatively less stress for the animals compared to the skin test and give reproducible and reliable results.

Animals↗
PubMed2004

Reactivation of tuberculosis during immunosuppressive treatment in a patient with a positive QuantiFERON-RD1 test.

A patient with polymyositis developed tuberculosis during immunosuppressive treatment. Tuberculin Skin Test and chest X-ray failed to demonstrate latent tuberculosis, whereas a blood sample that was tested with a modified QuantiFERON-TB-assay, using the recombinant ESAT-6 and CFP-10, was positive indicating that this patient was latently infected before immunosuppressive therapy. This case indicates the risk of progressing from latent to active tuberculosis given that the subject is RD1 responsive, and we believe that preventive anti-tuberculous treatment could have prevented this case of tuberculosis. We suggest that RD1 based tests are evaluated further in immunocompromised patients.

Antigens, Bacterial↗
PubMed2004

Protective effect of a tuberculosis subunit vaccine based on a fusion of antigen 85B and ESAT-6 in the aerosol guinea pig model.

A fusion protein of antigen 85B (Ag85B) and ESAT-6 administered in cationic lipid vesicles conferred a highly significant level of protection against Mycobacterium tuberculosis in the guinea pig aerosol model of infection. The protection was manifested as delayed clinical illness and prolonged survival. Neither Ag85B nor ESAT-6 (independently or as a cocktail) induced significant protection in this model.

Acyltransferases↗
PubMed2004

Association of tuberculin-boosted antibody responses with pathology and cell-mediated immunity in cattle vaccinated with Mycobacterium bovis BCG and infected with M. bovis.

Vaccine development and our understanding of the pathology of bovine tuberculosis in cattle would be greatly facilitated by definition of the immunological correlates of protection and/or pathology. In this study we analyzed humoral immune responses in Mycobacterium bovis BCG-vaccinated and control cattle (in particular, the relationship between the intradermal comparative tuberculin skin test and serum immunoglobulin G [IgG] responses) against a range of mycobacterial antigens (MPB59, MPB64, MPB70, MPB83, ESAT-6, CFP-10, Acr1, and PstS-1) by multiantigen print immunoassay and conventional enzyme-linked immunosorbent assay. Following M. bovis infection, the comparative tuberculin skin test strongly boosted IgG, IgG1, and IgG2 antibody responses, particularly against MPB83 and MPB70, in unvaccinated cattle but failed to boost these responses, or did so only weakly, in BCG-vaccinated calves. In addition, the skin test-induced increases in MPB83-specific IgG responses correlated positively with bacterial loads and ESAT-6-induced in vitro gamma interferon responses. In conclusion, both the negative correlation of skin test-enhanced MPB83-specific antibody responses with BCG-induced protection and their positive correlation with bacterial loads can serve as useful markers for vaccine efficacy after challenge.

Animals↗
PubMed2004

Protein-protein interactions of proteins from the ESAT-6 family of Mycobacterium tuberculosis.

In the present study, we demonstrate that, in analogy with the genes encoding ESAT-6 and CFP-10, the genes rv0287 and rv0288 from the ESAT-6 gene family are cotranscribed. Using Western-Western blotting and protein-print overlay methodologies, we demonstrate that ESAT-6 and CFP-10, as well as the protein pair Rv0288/Rv0287, interact pairwise in a highly specific way. Most notably, the ESAT-6 proteins interact directly with Rv3873, a possible cell envelope component of the ESAT-6 secretion pathway.

Antigens, Bacterial↗
PubMed2004

Specific T-cell epitopes for immunoassay-based diagnosis of Mycobacterium tuberculosis infection.

The currently used method for immunological detection of tuberculosis infection, the tuberculin skin test, has low specificity. Antigens specific for Mycobacterium tuberculosis to replace purified protein derivative are therefore urgently needed. We have performed a rigorous assessment of the diagnostic potential of four recently identified antigens (Rv2653, Rv2654, Rv3873, and Rv3878) from genomic regions that are lacking from the Mycobacterium bovis bacillus Calmette-Guérin (BCG) vaccine strains as well as from the most common nontuberculous mycobacteria. The fine specificity of potential epitopes in these molecules was evaluated by sensitive testing of the T-cell responses of peripheral blood mononuclear cells derived from M. bovis BCG-vaccinated healthy individuals to synthesized overlapping peptides. Three of the four molecules contained regions with significant specificity problems (Rv2653, Rv3873, and Rv3878). We selected and combined the specific peptide stretches from the four proteins not recognized by M. bovis BCG-vaccinated individuals. These peptide stretches were tested with peripheral blood mononuclear cells obtained from patients with microscopy- or culture-confirmed tuberculosis and from healthy M. bovis BCG-vaccinated controls. The combination of the most promising stretches from this analysis showed a sensitivity level (57%) comparable to the level found with the two well-known M. tuberculosis-specific proteins ESAT-6 and CFP-10 (75 and 66%, respectively). The combination of ESAT-6, CFP-10, and the novel specific peptide stretches gave an overall sensitivity of 84% at a specificity of 97%. In a validation experiment with new experimental groups, the sensitivities obtained were 57% for the combination of peptides and 90% for the combination of the peptides, ESAT-6, and CFP-10. This combination gave a specificity of 95%.

Adult↗
PubMed2003

Comparison of T-cell-based assay with tuberculin skin test for diagnosis of Mycobacterium tuberculosis infection in a school tuberculosis outbreak.

BACKGROUND: The diagnosis of latent tuberculosis infection relies on the tuberculin skin test (TST), which has many drawbacks. However, to find out whether new tests are better than TST is difficult because of the lack of a gold standard test for latent infection. We developed and assessed a sensitive enzyme-linked immunospot (ELISPOT) assay to detect T cells specific for Mycobacterium tuberculosis antigens that are absent from Mycobacterium bovis BCG and most environmental mycobacteria. We postulated that if the ELISPOT is a more accurate test of latent infection than TST, it should correlate better with degree of exposure to M tuberculosis. METHODS: A large tuberculosis outbreak in a UK school resulted from one infectious index case. We tested 535 students for M tuberculosis infection with TST and ELISPOT. We compared the correlation of these tests with degree of exposure to the index case and BCG vaccination. FINDINGS: Although agreement between the tests was high (89% concordance, kappa=0.72, p<0.0001), ELISPOT correlated significantly more closely with M tuberculosis exposure than did TST on the basis of measures of proximity (p=0.03) and duration of exposure (p=0.007) to the index case. TST was significantly more likely to be positive in BCG-vaccinated than in non-vaccinated students (p=0.002), whereas ELISPOT results were not associated with BCG vaccination (p=0.44). INTERPRETATION: ELISPOT offers a more accurate approach than TST for identification of individuals who have latent tuberculosis infection and could improve tuberculosis control by more precise targeting of preventive treatment.

Adolescent↗
PubMed2003

A novel TB vaccine; strategies to combat a complex pathogen.

Years of intense research aimed at developing a new and improved vaccine against tuberculosis (TB) are now moving from the laboratories and into the field. Many groups have provided strong evidence for the potential of novel vaccines using a variety of different strategies and the most promising are just beginning to enter human safety trials. As research has developed over the years, the complexity of the TB situation at the global level and its influence on vaccine development strategies has become more and more clear. From being mainly focused on the development of a vaccine that could be given at birth and provide lifelong protection, it is now clear that the current goal may need to be a vaccine to be given to a population where the majority is already sensitized either by previous infection, exposure to other mycobacteria or by Bacille Calmette-Guerin vaccination. With the increasing awareness of the different immune mechanisms operating under those circumstances, such a vaccine still represents a significant challenge for immunologists and microbiologists working in this field.

Animals↗
PubMed2003

Improved serodetection of Mycobacterium bovis infection in badgers (Meles meles) using multiantigen test formats.

Despite attempts to control bovine tuberculosis, the incidence of disease in Great Britain continues to rise. In GB, the European badger (Meles meles) is a reservoir of infection with Mycobacterium bovis. In an effort to improve the serodetection of badger tuberculosis, we examined sera from M. bovis culture-positive and culture-negative badgers for their ability to recognize M. bovis antigens, using a multi-antigen print immunoassay (MAPIA). Depending on the antigens used in the MAPIA, the assay had a sensitivity of 49-59% and a specificity of 84-88% Results from the MAPIA were used to select antigens for the development of a lateral-flow immunoassay. This so-called 'Rapid Test' used 5microl of serum and gave unambiguous results within 10 min. When applied to 178 badger sera, the Rapid Test had a sensitivity of 53% and a specificity of 95%. This represented an improvement over the performance of the existing ELISA Test, which had a sensitivity of 47% and a specificity of 89% on the same sera. This is the first report of a diagnostic test for badger tuberculosis that can be performed alongside the captive animal.

Animals↗
PubMed2003

The impact of malignant disease on facial nerve function after parotidectomy.

OBJECTIVES/HYPOTHESIS: Studies of immediate postoperative facial nerve function following parotidectomy focus on benign disease. The purpose of the study was to compare facial nerve function with regard to benign or malignant disease in patients undergoing superficial parotidectomy. STUDY DESIGN: Retrospective cohort study of consecutive patients undergoing parotidectomy between 1995 to 2002. METHODS: House-Brackmann (HB) grade was recorded or assigned at the first postoperative visit. For patients with HB grade of III or greater, final resolution of facial nerve function was recorded. A chi2 analysis for independence was conducted between patients with HB grade of II or less and those with HB grade of III or greater and final pathological finding (benign vs. malignant disease). Mean and median times to resolution were determined for patients with HB grade of III or greater. Times to resolution for benign and malignant disease for those with HB grade of III or greater were compared (Kaplan-Meier method). RESULTS: Sixty-seven patients with benign disease and 52 with malignant disease were included. Ninety-four percent of patients with benign disease had HB grade of II or less at first postoperative visit (mean period, 11.6 d) compared with 76.9% of patients with malignant disease (mean period, 12.4 d). A chi2 analysis found this difference significant (chi2 = 7.36, P =.0067). Time to resolution for HB grade of III or greater was 253.8 days (+/-168.2 d) with median time of 229.5 days for benign disease and 182.4 days (+/-134.6 d) with median time of 138 days for malignant disease. Kaplan-Meier comparison found no significant differences in time to final resolution (P =.83). Three patients in the group with malignant disease had unresolved dysfunction (one patient for >2 y). CONCLUSIONS: Patients with benign disease have a greater chance of having HB grade of II or less immediately following surgery; however, whether the disease is benign or malignant, long-term final facial nerve function is the same.

Adolescent↗