Assessment of an Interferon-gamma release assay for the diagnosis of latent tuberculosis infection in haemodialysis patient.

BACKGROUND: The accurate diagnosis of latent tuberculosis infection (LTBI) in haemodialysis patients remains elusive. Impaired immune function associated with chronic kidney failure causes a high number of anergic tuberculin skin tests (TST). Interferon-gamma (INF-gamma) release assays (IGRAs) measuring the INF-gamma secretion of tuberculosis specific T-cells have several advantages over the TST but their significance in dialysis patients is currently uncertain. METHODS: This study examines the test-performances of the QuantiFERON Gold InTube (QFT-GIT) in a cohort of 39 haemodialysis (HD) patients and 52 healthy individuals. RESULTS: INF-gamma secretion in HD patients was significantly lower than in healthy controls, however, mitogen-anergic QFT-GIT results were only found in 2.5% of HD-patients. INF-gamma secretion was independent of duration of HD treatment, dialysis quality and nutritional status. The QFT-GIT showed a closer association with TB risk factors as a proxy for past exposure to TB than the TST. CONCLUSIONS: We conclude that the QFT-GIT is a valid alternative to the TST. Together with the survey of TB risk factors, it may help to diagnose LTBI more accurately in HD-patients.

Expert opinion: guidelines for the use of natalizumab in multiple sclerosis patients previously treated with immunomodulating therapies.

Natalizumab (Tysabri) (anti-VLA4) is a novel agent for treatment of relapsing multiple sclerosis (MS) [Polman C.H., O'Connor P.W., Havrdova E. et al., 2006. A randomized, placebo-controlled trial of natalizumab for relapsing multiple sclerosis. N. Engl. J. Med. 354, 899-910.]. Controlled trials have shown considerable efficacy in preventing relapses, in excess of that seen for other EMEA-approved disease modulating drugs. While well-tolerated and generally safe, three cases of progressive multifocal leukoencephalopathy (PML) occurred in the context of 3 clinical trials encompassing some 3300 patients using this drug in multiple sclerosis and Crohn's disease. Immune compromised patients, such as those receiving immunosuppressive medications, are at a higher risk of developing PML. Natalizumab was recently approved for the treatment of relapsing forms of MS. This includes patients who had an inadequate response to other therapies and some of these patients will have already received immunosuppressants. These agents have the potential to cause prolonged effects on the immune system, even after dosing has been discontinued. Determining that these patients are not immunocompromised will be an important safety issue to consider prior to the initiation of natalizumab therapy. This short report summarizes interdisciplinary practical recommendations from specialists in neuroimmunology, rheumatology, transplantation medicine and clinical immunology.

The SGML standardization framework and the introduction of XML.

Extensible Markup Language (XML) is on its way to becoming a global standard for the representation, exchange, and presentation of information on the World Wide Web (WWW). More than that, XML is creating a standardization framework, in terms of an open network of meta-standards and mediators that allows for the definition of further conventions and agreements in specific business domains. Such an approach is particularly needed in the healthcare domain; XML promises to especially suit the particularities of patient records and their lifelong storage, retrieval, and exchange. At a time when change rather than steadiness is becoming the faithful feature of our society, standardization frameworks which support a diversified growth of specifications that are appropriate to the actual needs of the users are becoming more and more important; and efforts should be made to encourage this new attempt at standardization to grow in a fruitful direction. Thus, the introduction of XML reflects a standardization process which is neither exclusively based on an acknowledged standardization authority, nor a pure market standard. Instead, a consortium of companies, academic institutions, and public bodies has agreed on a common recommendation based on an existing standardization framework. The consortium's process of agreeing to a standardization framework will doubtlessly be successful in the case of XML, and it is suggested that it should be considered as a generic model for standardization processes in the future.

Conception of an XML-based ontology for a Web-based medical information service.

In order to be useful for practice, medical information on the World Wide Web must be relevant, reliable, well designed, and easy accessible. Approaches towards improving these requirements include evidence-based medical information services such as EVIMED. This research paper considers the question of how a user can be supported in accessing requested information from EVIMED and how further, semantically related information can easily be retrieved. The presented method of resolution is based on Schmid's concept of media and on Gruber's concept of the ontology. The use of the emerging Web standard eXtensible Markup Language (XML) in order to implement it, allows for the design of a component-based solution supporting an easy adaptation of the representational vocabulary in accordance with the conceptualization of the user, i.e., the practitioner.

An electronic study form to support collaborating agents in the management of clinical knowledge.

When dealing with biological organisms, one has to take into account some peculiarities which significantly affect the representation of knowledge about them. These are complemented by the limitations in the representation of propositional knowledge, i.e. the majority of clinical knowledge, by artificial agents. Thus, the opportunities to automate the management of clinical knowledge are widely restricted to closed contexts and to procedural knowledge. Therefore, in dynamic and complex real-world settings such as health care provision to HIV-infected patients human and artificial agents must collaborate in order to optimize the time/quality antinomy of services provided. If applied to the implementation level, the overall requirement ensues that the language used to model clinical contexts should be both human- and machine-interpretable. The eXtensible Markup Language (XML), which is used to develop an electronic study form, is evaluated against this requirement, and its contribution to collaboration of human and artificial agents in the management of clinical knowledge is analyzed.

Basic problems of serological laboratory diagnosis.

Serological laboratory diagnosis is inflicted with at least two kinds of basic problems. One type relates to the fact that the serological diagnosis of infectious diseases is double indirect: First, to diagnose an infectious disease, the identification of the microbial agent is sought that caused the disease. Second, to identify this infectious agent, the patient's immune response to potential agents is measured. So, the serological test is neither measuring directly disease nor the cause of the disease, but the patient's immune system. Another type of problem is based on the fact that each person's immune system is very individual. The exact physicochemical properties of antibodies are unique for each clone of antibodies. The way an individual's immune system sees an infectious agent depends not only on the genetic makeup of the person but also on the personal experience from former encounters with infectious agents. Both types of problems lead to complexities in selecting the appropriate test, in interpreting the results, and in standardizing serological tests. Therefore, a close collaboration of the laboratory with the clinic is mandatory to avoid erroneous conclusions from serological test results, which might lead to wrong decisions in patient care.

High frequency of non-B subtypes in newly diagnosed HIV-1 infections in Switzerland.

HIV-1 subtypes were determined in newly diagnosed residents of Switzerland. Blood was anonymously collected from patients with a first confirmed positive HIV-1 test result. Viral DNA from the env V3-V5 region was amplified by nested polymerase chain reaction (PCR) and screened for subtype B by heteroduplex mobility assay. All amplicons not identified as B were sequenced. From November 1996 to February 1998, 206 samples were analyzed. Main transmission risks were unprotected heterosexual (55.7%) or homosexual (27.1%) sexual contact or intravenous drug use (12.9%). Subtype B dominated in patients of Swiss, other European, American, or Asian citizenship; particularly high frequencies were found in homosexuals (97%) and drug users (94%). Non-B subtypes including A, C, D, E, F, G, H, a possible B/F recombinant, and a sequence related to J were present in 28.2% (95% confidence interval [CI], 22.9%-35.0%). Non-B were frequent in African citizens (95%), heterosexually infected individuals (44%), and women (43%). Heterosexually infected Swiss males harbored non-B strains in 18% and females in 33%. The results document a change in the epidemiology of newly diagnosed HIV-1 infections in Switzerland: predominance of heterosexual transmission and a high frequency of non-B subtypes.

Atypical, cytoplasmic and perinuclear anti-neutrophil cytoplasmic antibodies in patients with inflammatory bowel disease.

Atypical, cytoplasmic and perinuclear anti-neutrophil cytoplasmic antibodies (x-, c- and pANCA, respectively) are associated with a variety of inflammatory diseases, including inflammatory bowel disease (IBD). Anti-neutrophil cytoplasmic antibodies are more common in patients with ulcerative colitis (UC) than in patients with Crohn's disease (CD). Most publications only refer to p- and cANCA in relation to IBD. We have prospectively evaluated the reactivity of sera from 58 patients with IBD and 10 healthy controls against human neutrophils with emphasis on the distinction of the ANCA types. The sera were incubated with ethanol- and formaldehyde-fixed granulocytes to differentiate between c-, p- and xANCA. The results showed that 10 of 24 patients with UC were positive for ANCA, whereas only one of 34 patients with CD was ANCA positive. These results correspond to a sensitivity of 42%, a specificity of 97%, a negative predictive value of 91% and a positive predictive value of 75% in UC. Of the 11 ANCA-positive sera, two showed a cytoplasmic staining pattern, three showed a perinuclear and six an atypical staining pattern. The disease activity was not correlated to either the ANCA titre or to the presence of ANCA in the serum. In conclusion, ANCA are of limited value in differentiating between UC and CD. Because the majority of ANCA in patients with IBD are xANCA, these ANCA should be explored by not only incubating on ethanol-fixed granulocytes, but also on formaldehyde-fixed granulocytes.

Serological evidence of human granulocytic ehrlichiosis in Switzerland.

To investigate whether human granulocytic ehrlichiosis (HGE) is prevalent in Switzerland, 1515 human serum samples from individuals with different risks for tick exposure were tested for antibodies to Ehrlichia phagocytophila, a surrogate marker of the agent of HGE. The distribution of titres showed marked differences between sera of individuals with no or low risk for tick exposure and those with a high risk. The results of serological testing provided evidence of HGE in Switzerland as well as evidence of two types of coinfections: those with the agent of HGE and Borrelia burgdorferi, and those with the agent of HGE and the central European tickborne encephalitis virus.

Basic problems of serological laboratory diagnosis.

Serological testing and the use of immunochemical techniques are well established in the clinical laboratory and then uses are still rapidly increasing. Serological tests are applied for the diagnosis of infectious diseases, autoimmune disorders, allergies, and malignancies. Yet despite their widespread use, immunoassays are inflicted with a number of significant problems that lead to a substantial variation in reliability and accuracy of currently available tests. In the recent process of establishing procedures and criteria for quality assurance in the clinical laboratory an increased awareness of these problems has arisen among the clinical and reference laboratories as well as among the manufacturers of commercial test kits. The recognition of this situation prompted the US National Committee for Clinical Laboratory Standards (NCCLS) to create specific guidelines that address "the generrc problems of preparation and characterization of antigens and antibodies, testing using these reagents, and understanding the results" These guidelines are made public in the NCCLS document I/LA 18-A Specifications for Immunological Testing for Infectious Diseases; Approved Guideline, issued in December 1994 (1). References to this document will be made in this chapter where appropriate, and particularly, attempts will be made to adhere to the definitions of terms and procedures as they are laid down in the NCCLS consensus document.

[Disseminated mycobacteriosis with M. kansasii in a case of AIDS without HIV infection]. / Disseminierte Mykobakteriose mit M. kansasii bei einem Fall von Aids ohne HIV-Infektion.

M. kansasii is an environmental Mycobacterium that causes disease mainly in patients with local or systemic immunodeficiency. We present a case with disseminated M. kansasii infection which led to a severe febrile illness lasting for 9 months. The patient had a combined acquired immunodeficiency syndrome (AIDS) which included CD4+ and CD8+ T-lymphocytopenia, monocytopenia and a deficiency in the IgG subclasses 2 and 4. HIV testing was repeatedly negative. In the published literature only 4 of 10 similar patients (this patient included) survived a disseminated M. kansasii infection. Eleven years after the disseminated infection with M. kansasii a second opportunistic infection, disseminated mollusca contagiosa and hyperparathyroidism, developed, and 14 years later the immunologic abnormalities persist.

Infrequent detection of lipoarabinomannan antibodies in human immunodeficiency virus-associated mycobacterial disease. Swiss HIV Cohort Study.

A commercially available test for the serologic diagnosis of tuberculosis was evaluated for its applicability in human immunodeficiency virus (HIV)-positive patients. Antibodies to lipoarabinomannan were detectable in sera from only 9 of 85 HIV-positive patients with a confirmed diagnosis of tuberculosis. Given the low degree of sensitivity of the assay with sera from HIV-infected patients, the study does not support the use of this serologic assay for the diagnosis of tuberculosis in HIV-infected patients.

Clinical outcome and immunology of postoperative arginine, omega-3 fatty acids, and nucleotide-enriched enteral feeding: a randomized prospective comparison with standard enteral and low calorie/low fat i.v. solutions.

In a prospective randomized trial in patients undergoing major abdominal surgery, the impact of a new enteral formula supplemented with arginine, omega-3 fatty acids, and nucleotides (A, n = 14) on immunological parameters was compared with a standard enteral formula (B, n = 14) and a low calorie/low fat intravenous solution (C, n = 13). Four days postoperatively, a statistically significant decrease in total leukocyte count (A, 9.0 +/- 2.9; B, 8.0 +/- 2.4; C, 11.1 +/- 3.5 x 10(6) cells/mL; A versus C, B versus C; p < 0.05), higher percentage of lymphocytes (A, 14.3 +/- 4.9; C, 8.2 +/- 6.1; p < 0.05), and decreased median CRP levels (A, 80.4 [69.9]; B, 70 [74]; C, 88.5 [142] in mg/L; A versus C, p < 0.05; B versus C; p < 0.05) were observed in the enteral nutrition groups. The expression of activated surface antigen HLA-DR was diminished on CD14+ cells over 4 d (A, 58.2 [39.2]; B, 52.2 [36.2]; C, 76.6 [25.2] in %; A versus C, p < 0.05; B versus C, p < 0.05) and 8-10 d (A, 37.9 [31.4]; C, 58.5 [37.6]; p < 0.05) postoperatively. Significantly enhanced median phagocytic activity of CD14+ monocytes and granulocytes was observed in group C 8-10 days postoperatively (A, 83.3 [11.8]; B, 71.6 [34.1]; C, 87.4 [10.8]; A versus B, B versus C, p < 0.05; and A, 75.7 [10.0]; B, 69.0 [37.8]; C, 80.0 [10.1] in %, B versus C, p < 0.05, respectively). Postoperative hospital and intensive care unit stay was similar among the three groups; however, infectious complications were less frequent in group A (A versus C, p = 0.15). Thus, a modified enteral nutritional support and supplementation may influence the immune competence toward a more efficient defense response.

Pregnancy, immunosuppression and reactivation of latent toxoplasmosis.

Toxoplasmosis is a chronic, latent infection which can be reactivated in the presence of immunosuppression. The critical question in obstetrics is whether toxoplasmosis may be reactivated in the presence of the physiological "immunosuppression" of pregnancy. Standard in vitro tests, done in 24 healthy pregnant women and compared with the literature, show no significant changes in humoral and cellular immunity during pregnancy. However, the fact that some infections occur more frequently and more severely than in non-pregnant women (e.g. those due to cytomegalovirus (CMV) and human papilloma virus (HPV) points to a degree of pregnancy-associated immunosuppression. Non-rejection of the semiallogenic fetus is achieved in presence of maternal immunocompetence and is explained mainly by local changes in immune function, mediated by inhibitors of decidual, placental and fetal origin, and by the absence of class II histocompatibility antigens at the fetomaternal interface. Immune status allowing reactivation of toxoplasmosis was studied in a selected group of (predominantly male) AIDS patients from the Swiss HIV Cohort study. Shortly before (cerebral) reactivation of toxoplasmosis, 92% of these patients had very low CD4 lymphocyte counts (mean 50 cells/microliters, i.e. lower than ever recorded in a normal uncomplicated pregnancy). In a larger population of 48 women receiving immunosuppressive therapy after organ transplantation, not a single case of cerebral toxoplasmosis was observed during pregnancy, while in the 105 HIV-positive women in the Swiss HIV and Pregnancy study, there was only one case of cerebral toxoplasmosis during pregnancy and the puerperium (20 CD4/microliters), even though some 17% of those sampled (18/105) had CD4 levels below 200 cells/microliters on at least one occasion during pregnancy. These findings explain why latent toxoplasmosis is not reactivated in normal pregnancy, and why it is only likely in an immunosuppressed mother when her CD4 lymphocyte count is very low (< 200 cells/microliters). In such cases, a prophylactic treatment to prevent maternal reactivation and vertical transmission of toxoplasmosis may be useful.

Heterogeneous binding and killing behaviour of human gamma/delta-TCR+ lymphokine-activated killer cells against K562 and Daudi cells.

Effector-target conjugates, formed by coincubation of lymphokine-activated killer (LAK) cells with either K562 or Daudi cells, were separated from single cells by Percoll sedimentation. The occurrence of various CD molecules (CD3, CD56, CD57, CD16, gamma/delta-TCR) was compared in both fractions. Only LAK cells expressing the gamma/delta T cell receptor (TCR) were found in a significantly increased percentage in fractions containing conjugates indicating that gamma/delta-TCR+ LAK cells were preferably bound to target cells at the time of separation. In order to determine whether gamma/delta-TCR+ LAK cells also show a preferred killing activity against the targets, cultures enriched with or depleted of gamma/delta-TCR+ cells were established. Against K562 cells, gamma/delta-TCR(+)-enriched cultures showed a greatly reduced killing activity compared to LAK bulk cultures or cultures depleted of gamma/delta-TCR+ cells. Using Daudi cells as targets the enriched fraction revealed a slightly increased killing activity compared to bulk cultures or depleted fractions. Preincubation of gamma/delta-TCR+ LAK cells with anti-gamma/delta or anti-CD3 mAb resulted in a distinct increase of the killing activity against K562 cells, but in only a slightly enhanced activity against Daudi cells. It is postulated that gamma/delta-TCR+ LAK cells use the same adhesion mechanism for both targets but that only Daudi cells express a specific ligand for the gamma/delta-TCR. Occupation of the gamma/delta-TCR/CD3 complex by mAb, however, seems to substitute for the absent epitope on K562 cells by eliciting stimulatory signals in gamma/delta-TCR+LAK cells which, in combination with the binding stimulus, trigger cytolytic activity.

[The prognostic value of different patterns of change in the CD4 lymphocyte counts in 420 symptom-free HIV-1-infected persons]. / Prognostischer Wert verschiedener Verlaufsmuster der CD4-lymphozyten-Zahlen bei 420 symptomfreien HIV-1-Infizierten.

The pattern of change over time of CD4-lymphocyte counts was investigated prospectively in 420 patients infected with HIV-1 (106 women, 314 men; mean age 34.9 [21-70] years) to assess its value in prognosticating progression to AIDS. Only those CD4-lymphocyte values were taken into account which had been measured in the asymptomatic stage of the HIV infection and before introduction of antiviral treatment. An average of 4.5 (range 3-10) measurements per person were available. Mean observation time was 2.4 years, the mean annual CD4-lymphocyte decrease was 48 cells/microliters. 121 patients (28.8%) had a fall in CD4-lymphocyte count which in the regression analysis significantly differed from zero. In this group there occurred 19 progressions to AIDS (15.7%), in contrast to only 20 (6.6%) in the 299 patients with a nonsignificant CD4 fall (P < 0.01). Multivariate analysis with the Cox regression indicated that the annual reduction in the CD4 count and the initial CD4 count were the only values of prognostic significance regarding progression to AIDS. There was no evidence that percentage and absolute CD4-lymphocyte counts had a different predictive value. When the initial CD4 count was high (> 900 cells/microliters), there was on average a steeper reduction in CD4-lymphocyte counts than when it was lower. This findings argues against a linear CD4 fall during the total period of observation. The annual CD4 fall, described with linear regression, is a prognostic criterion on its own for early recognition of those patients at a high risk of progression to AIDS while still in the asymptomatic stage of HIV infection.

Using a neural network to identify potential HLA-DR1 binding sites within proteins.

The presentation by antigen-presenting cells of immunodominant peptide segments in association with major histocompatibility complex (MHC) encoded proteins is fundamental to the efficacy of a specific immune response. One approach used to identify immunodominant segments within proteins has involved the development of predictive algorithms which utilize amino acid sequence data to identify structural characteristics or motifs associated with in vivo antigenicity. The parallel-computing technique termed 'neural networking' has recently been shown to be remarkably efficient at addressing the problem of pattern recognition and can be applied to predict protein secondary structure attributes directly from amino acid sequence data. In order to examine the potential of a neural network to generalize peptide structural features related to binding within class II MHC-encoded proteins, we have trained a neural network to determine whether or not any given amino acid of a protein is part of a peptide segment capable of binding to HLA-DR1. We report that a neural network trained on a data base consisting of peptide segments known to bind to HLA-DR1 is able to generalize features relating to HLA-DR1-binding capacity (r = 0.17 and p = 0.0001).

T cell response to staphylococcal superantigens by asymptomatic HIV-infected individuals exhibits selective changes in T cell receptor V beta-chain usage.

Recognition that the murine mammary tumor C-type retrovirus and the replication-defective murine leukemia virus have "superantigen" properties raises the specter that human immunodeficiency virus might also generate T cell impairment and destruction as a result of inherent superantigen properties. The observation that individuals with AIDS lack the expression of several T cell receptor V beta-chain genes lends support to this hypothesis. Staphylococcal exotoxins represent another class of superantigen with a similar ability to stimulate large numbers of T cells bearing specific T cell receptor V beta-chain types. To examine the hypothesis that T cells from HIV-infected individuals may be exposed to a superantigen during the infection process, we have compared the ability of T cells from asymptomatic HIV-infected donors and healthy donors to respond to stimulation with several known staphylococcal exotoxin superantigens. Following in vitro stimulation with staphylococcal enterotoxin D and staphylococcal enterotoxin E, asymptomatic HIV-infected individuals responded with a significantly different T cell receptor V beta-chain usage to that observed for healthy individuals. This skewed V beta-chain usage is likely to reflect preferential conditioning of T cells bearing specific V beta-chains as a result of HIV infection, supporting the hypothesis of superantigen involvement early in the course of infection.