Skin Test-positive Individuals Research Articles

BCG Vaccination Induces M. avium and M. abscessus Cross-Protective Immunity.

Pulmonary non-tuberculous mycobacterial (NTM) infections particularly caused by Mycobacterium avium complex (MAC) and Mycobacterium abscessus (MAB) are becoming major health problems in the U.S. New therapies or vaccines which will help prevent the disease, shorten treatment duration and/or increase treatment success rates are urgently needed. This study was conducted with the objective of testing the hypothesis that Bacillus Calmette Guerin (BCG), a vaccine used for prevention of serious forms of tuberculosis (TB) in children and adolescents in tuberculosis hyperendemic countries, induces cross-protective T cell immunity against Mycobacterium avium (MAV) and MAB. Human TB and NTM cross-protective T cells were quantified using flow cytometric assays. The ability of BCG expanded T cells to inhibit the intracellular growth of MAV and MAB was assessed in co-cultures with infected autologous macrophages. In both BCG-vaccinated and M. tuberculosis (Mtb)-infected mice, NTM cross-reactive immunity was measured using IFN-γ ELISPOT assays. Our results demonstrate the following key findings: (i) peripheral blood mononuclear cells from TB skin test-positive individuals contain MAV and MAB cross-reactive T cells, (ii) both BCG vaccination and Mtb infection of mice induce MAV and MAB cross-reactive splenic cells, (iii) BCG-expanded T cells inhibit intracellular MAV and MAB, (iv) CD4, CD8, and γδ T cells play important roles in inhibition of intracellular MAV and MAB and (v) BCG vaccination of healthy volunteers induces TB and NTM cross-reactive T cells. In conclusion, BCG-vaccination induces NTM cross-reactive immunity, and has the potential for use as a vaccine or immunotherapy to prevent and/or treat pulmonary NTM disease.

Assessment of isoniazid preventive therapy in the reduction of tuberculosis among ART patients in Arba Minch Hospital, Ethiopia.

BackgroundTuberculosis (TB) is the most frequent life-threatening opportunistic disease among people living with HIV and remains a leading cause of mortality, even among persons receiving antiretroviral therapy (ART). Isoniazid preventive therapy (IPT) and cotrimoxazole prophylaxis have been recommended for the benefit of HIV/AIDS-infected individuals to prevent opportunistic infections. The aim of this study was to assess IPT prophylaxis in the reduction of TB among ART patients.MethodsThe study was a hospital-based retrospective study. A total of 271 study participants’ available information such as demographic data, the type of prophylaxis used, and TB/HIV coinfection status as well as other variables were collected from clinical laboratory and HIV care/ART follow-up clinic. Data analysis was performed using Statistical Package for the Social Sciences (SPSS) version 20.0.ResultsTB-infected ART patients were higher among non-IPT group (37 [27.8%]) compared to IPT group (12 [8.7%]). The finding showed that IPT prophylaxis significantly reduces acquiring TB with the relative risk =0.31 (95% confidence interval =0.122, 0.49) in ART patients of this study site where the tuberculosis prevalence is prominent. ART had significant contribution for CD4+ T-cell lymphocyte count improvement in both IPT and non-IPT groups (P<0.05) in this study.ConclusionIPT had significant contributions to reduce the burden of TB in ART patients than non-IPT group. This result highlights the use of IPT for the prevention of TB, especially for all ART patients. Other longitudinal studies are needed to observe the benefits and side effects of IPT prophylaxis in tuberculin skin test-positive individuals.

Cost-effectiveness of the Three I's for HIV/TB and ART to prevent TB among people living with HIV.

To evaluate the cost-effectiveness of the Three I's for HIV/TB (human immunodeficiency virus/tuberculosis): antiretroviral therapy (ART), intensified TB case finding (ICF), isoniazid preventive treatment (IPT), and TB infection control (IC). Using a 3-year decision-analytic model, we estimated the cost-effectiveness of a base scenario (55% ART coverage at CD4 count ⩿350 cells/mm(3)) and 19 strategies that included one or more of the following: 1) 90% ART coverage, 2) IC and 3) ICF using four-symptom screening and 6- or 36-month IPT. The TB diagnostic algorithm included 1) sputum smear microscopy with chest X-ray, and 2) Xpert® MTB/RIF. In resource-constrained settings with a high burden of HIV and TB, the most cost-effective strategies under both diagnostic algorithms included 1) 55% ART coverage and IC, 2) 55% ART coverage, IC and 36-month IPT, and 3) expanded ART at 90% coverage with IC and 36-month IPT. The latter averted more TB cases than other scenarios with increased ART coverage, IC, 6-month IPT and/or IPT for tuberculin skin test positive individuals. The cost-effectiveness results did not change significantly under the sensitivity analyses. Expanded ART to 90% coverage, IC and a 36-month IPT strategy averted most TB cases and is among the cost-effective strategies.

Increased Frequency of Myeloid-derived Suppressor Cells during Active Tuberculosis and after RecentMycobacterium tuberculosisInfection Suppresses T-Cell Function

Inadequacy of T-cell responses may result in the development of tuberculosis (TB). Myeloid-derived suppressor cells (MDSCs) have been described as suppressors of T-cell function in cancer biology and recently in several infectious diseases. To explore the presence and role of MDSCs in TB. We analyzed surface markers of MDSCs in peripheral blood and at the site of disease in TB cases and in patients with lung cancer, and in peripheral blood of asymptomatic tuberculin skin test-positive individuals with recent (household) or remote exposure to Mycobacterium tuberculosis (M.tb) and in uninfected healthy control subjects. To evaluate the suppressive capacity of MDSCs, cells of household contacts infected with M.tb and TB cases were isolated and cocultured with CD3(+) T cells. Our results demonstrate an increased presence of MDSCs after recent M.tb infection and disease. We confirm their suppression of CD4(+) T-cell function, including reduced cytokine responses and inhibition of CD4(+) T-cell proliferation. Only MDSCs from TB cases reduced T-cell activation, altered T-cell trafficking, and suppressed CD8(+) T-cell functions. M.tb-expanded MDSCs were associated with significantly higher IL-1β, IL-6, IL-8, granulocyte colony-stimulating factor, and monocyte chemotactic protein-1, and reduced granulocyte-macrophage colony-stimulating factor and macrophage inflammatory protein-1 beta levels in coculture. These data reveal that innate MDSCs are induced not only during active TB at similar levels as found in cancer, but also in healthy individuals after recent exposure to M.tb. These cells diminish protective T-cell responses and may contribute to the inability of hosts to eradicate the infection and add to the subsequent development of TB disease.

Interferon-Gamma Release Assays versus Tuberculin Skin Testing for the Diagnosis of Latent Tuberculosis Infection: An Overview of the Evidence.

A profusion of articles have been published on the accuracy and uses of interferon-gamma releasing assays. Here we review the clinical applications, advantages, and limitations of the tuberculin skin test and interferon-gamma release assays and provide an overview of the most recent systematic reviews conducted for different indications for the use of these tests. We conclude that both tests are accurate to detect latent tuberculosis, although interferon-gamma release assays have higher specificity than tuberculin skin testing in BCG-vaccinated populations, particularly if BCG is received after infancy. However, both tests perform poorly to predict risk for progression to active tuberculosis. Interferon-gamma release assays have significant limitations in serial testing because of spontaneous variability and lack of a validated definition of conversion and reversion, making it difficult for clinicians to interpret changes in category (conversions and reversions). So far, the most important clinical evidence, that is, that isoniazid preventive therapy reduces the risk for progression to disease, has been produced only in tuberculin skin test-positive individuals.

Prevalence of allergic sensitization to Russian thistle in Kingston and the South-eastern Ontario catchment area; a retrospective chart review

Background Russian thistle has only recently been identified as a potentially clinically important allergen. In the third phase of the National Health and Nutrition Examination Surveys conducted in the USA (1988 to1994) over 15% of tested individuals had positive skin-test responses to this extract. The rate of skin test positivity to Russian thistle in Canada is unknown. Objective To determine the prevalence of skin test positivity to Russian Thistle in patients from Kingston and the Southeastern Ontario catchment area, and the possible clinical significance of the same. Methods A retrospective chart review was performed to document the rate of sensitization amongst tested patients to Russian thistle extract (Hollister-Steir). Only patients with appropriate histamine responses were included. We collected demographic data in addition to the presence/ absence of relevant clinical symptoms. Results Of 410 charts reviewed, 170 underwent skin testing to Russian thistle. Of these, 17(10%) were positive. Of the test-positive cohort, 47% (8/17) had symptoms that correlated seasonally with the predominant Russian thistle pollen season (August-October). The mean age of skin-test positive individuals was 35.2 years. 82% and 52.9% of these had concomitant positive skin tests to ragweed and birch, respectively, allergens with known cross-reactivity. Conclusions This preliminary evaluation suggests that the prevalence of skin test positivity to Russian thistle in the studied area is approximately 10%, with about half of these individuals reporting correlative seasonal symptoms. Including Russian thistle in routine skin testing panel may better establish the clinical significance of this environmental allergen. This study was approved by the Queen’ sU niversity Health Sciences and Affiliated Teaching Hospitals Research Ethics Board, with no financial interest or funding provided.

T-Cell Recognition of the HspX Protein ofMycobacterium tuberculosisCorrelates with LatentM. tuberculosisInfection but Not withM. bovisBCG Vaccination

During stationary growth or in vitro conditions mimicking relevant aspects of latency, the HspX protein (Rv2031c) is specifically upregulated by Mycobacterium tuberculosis. In this study we compared T-cell responses against HspX and the secreted M. tuberculosis protein Ag85B (Rv1886c) in tuberculosis (TB) patients, tuberculin skin test-positive individuals, M. bovis BCG-vaccinated individuals, and healthy negative controls. Gamma interferon responses to HspX were significantly higher in M. tuberculosis-exposed individuals than in M. tuberculosis-unexposed BCG vaccinees. In contrast, no such differences were found with respect to T-cell responses against Ag85B. Therefore, BCG-based vaccines containing relevant fragments of HspX may induce improved responses against this TB latency antigen. To identify relevant major histocompatibility complex class I- and class II-restricted HspX-specific T-cell epitopes, we immunized HLA-A2/K(b) and HLA-DR3.Ab(0) transgenic (tg) mice with HspX. Two new T-cell epitopes were identified, p91-105 and p31-50, restricted via HLA-A*0201 and HLA-DRB1*0301, respectively. These epitopes were recognized by human T cells as well, underlining the relevance of HspX T-cell recognition both in vivo and in vitro. In line with the data in humans, BCG immunization of both tg strains did not lead to T-cell responses against HspX-derived epitopes, whereas nonlatency antigens were efficiently recognized. These data support the notion that BCG vaccination per se does not induce T-cell responses against the latency antigen, HspX. Thus, we suggest that subunit vaccines incorporating HspX and/or other latency antigens, as well as recombinant BCG strains expressing latency antigens need to be considered as new vaccines against TB.

Surprisingly High Specificity of the PPD Skin Test for M. tuberculosis Infection from Recent Exposure in The Gambia

BackgroundOptions for intervention against Mycobacterium tuberculosis infection are limited by the diagnostic tools available. The Purified Protein Derivative (PPD) skin test is thought to be non-specific, especially in tropical settings. We compared the PPD skin test with an ELISPOT test in The Gambia.Methodology/Principal FindingsHousehold contacts over six months of age of sputum smear positive TB cases and community controls were recruited. They underwent a PPD skin test and an ELISPOT test for the T cell response to PPD and ESAT-6/CFP10 antigens. Responsiveness to M. tuberculosis exposure was analysed according to sleeping proximity to an index case using logistic regression. 615 household contacts and 105 community controls were recruited. All three tests assessed increased significantly in positivity with increasing M. tuberculosis exposure, the PPD skin test most dramatically (OR 15.7; 95% CI 6.6–35.3). While the PPD skin test positivity continued to trend downwards in the community with increasing distance from a known case (61.9% to 14.3%), the PPD and ESAT-6/CFP-10 ELISPOT positivity did not. The PPD skin test was more in agreement with ESAT-6/CFP-10 ELISPOT (75%, p = 0.01) than the PPD ELISPOT (53%, p<0.0001). With increasing M. tuberculosis exposure, the proportion of ESAT-6/CFP-10 positive contacts who were PPD skin test positive increased (p<0.0001), and the proportion of ESAT-6/CFP-10 negative contacts that were PPD skin test negative decreased (p<0.0001); the converse did not occur.Conclusions/SignificanceThe PPD skin test has surprisingly high specificity for M. tuberculosis infection from recent exposure in The Gambia. In this setting, anti-tuberculous prophylaxis in PPD skin test positive individuals should be revisited.

Latex specific IgE: performance characteristics of the IMMULITE 2000 3gAllergy assay compared with skin testing

In the absence of a US Food and Drug Administration (FDA)-cleared latex skin testing reagent, in vitro tests remain important for the diagnosis of latex allergy. To evaluate the performance characteristics of IMMULITE 2000 3gAllergy (Immulite), a third-generation, FDA-cleared, continuous random-access immunoanalyzer, for the quantification of latex specific IgE. Stored serum samples (N = 201) from patients classified as having positive or negative latex puncture skin test results were measured for latex specific IgE levels using Immulite, and these data were compared with historical results from 3 second-generation, FDA-cleared IgE antilatex assays (AlaSTAT [Ala], AutoCAP [CAP], and HY*TEC enzyme immunoassay [HT]). The diagnostic performances of the CAP, Ala, and Immulite assays (> or = 0.35 kU/L cutoff value) were equivalent in sensitivity and specificity (P > .05). The HT assay (> or = 0.05 kU/L cutoff value) was more sensitive and less specific (P < .05). Immulite (> or = 0.10 kU/L cutoff value) had greater sensitivity than Ala and CAP and greater specificity than HT (P < .05 for both). Diagnostic efficiency was greater for Immulite than for CAP, Ala, and HT (P < .05). The Immulite system is superior in diagnostic performance, especially at the 0.10 kU/L or greater cutoff level, for the diagnosis of latex allergy compared with older, second-generation assays. Immulite still misclassifies 15.5% of puncture skin test-positive individuals as negative for latex specific IgE. Compared with second-generation assays, Immulite represents a technological advance, with enhanced speed and less operator intervention.

Enhancement of the human T cell response to culture filtrate fractions of Mycobacterium tuberculosis by microspheres

An improved method of assessment of the human immune response against Mycobacterium tuberculosis antigens will assist the development of new vaccines or diagnostic reagents. In this study, we have analyzed human T cell responses to culture filtrate fractions (CFF) of actively replicating M. tuberculosis strain H37Rv using peripheral blood mononuclear cells from healthy PPD skin test positive and negative individuals. Adsorption of CFF onto polystyrene microspheres, that were approximately the size of the M. tuberculosis (bead-adsorbed antigens, BAA) significantly enhanced IFN-γ production compared to soluble antigens (SA) in PPD skin test positive individuals in an antigen-specific manner. Further, BAA induced activation of both CD4 + and CD8 + T cell subsets. However, CD4 + responses in general were higher and their antigenic repertoire was wider than the CD8 + responses. By contrast, CD8 + responses were strongest to the lower molecular weight BAA. When CFF were chemically coupled to carboxyl modified microspheres (bead-coupled antigens, BCA), induction of IFN-γ was similar to BAA. Enhancement of T cell responses to particulate M. tuberculosis antigens may prove useful in vaccine design strategies.

Interaction of Mycobacterium tuberculosis-induced transforming growth factor beta1 and interleukin-10.

Mycobacterium tuberculosis is associated with the activation of cytokine circuits both at sites of active tuberculosis in vivo and in cultures of mononuclear cells stimulated by M. tuberculosis or its components in vitro. Interactive stimulatory and/or inhibitory pathways are established between cytokines, which may result in potentiation or attenuation of the effects of each molecule on T-cell responses. Here we examined the interaction of transforming growth factor beta1 (TGF-beta1) and interleukin-10 (IL-10) in purified protein derivative (PPD)-stimulated human mononuclear cell cultures in vitro. TGF-beta1 induced monocyte IL-10 (but not tumor necrosis factor alpha) production (by 70-fold, P < 0.02) and mRNA expression in the absence but not in the presence of PPD. Both exogenous recombinant (r) IL-10 and rTGF-beta1 independently suppressed the production of PPD-induced gamma interferon (IFN-gamma) in mononuclear cells from PPD skin test-positive individuals. Synergistic suppression of IFN-gamma in cultures containing both rTGF-beta1 and rIL-10 was only seen when the responder cell population were peripheral blood mononuclear cells (PBMC) and not monocyte-depleted mononuclear cells and when PBMC were pretreated with rTGF-beta1 but not with rIL-10. Suppression of PPD-induced IFN-gamma in PBMC containing both rTGF-beta1 (1 ng/ml) and rIL-10 (100 pg/ml) was 1.5-fold higher (P < 0.05) than cultures containing TGF-beta1 alone and 5.7-fold higher (P < 0.004) than cultures containing IL-10 alone. Also, neutralization of endogenous TGF-beta1 and IL-10 together enhanced PPD-induced IFN-gamma in PBMC in a synergistic manner. Thus, TGF-beta1 and IL-10 together potentiate the downmodulatory effect on M. tuberculosis-induced T-cell production of IFN-gamma, and TGF-beta1 alone enhances IL-10 production. At sites of active M. tuberculosis infection, these interactions may be conducive to the suppression of mononuclear cell functions.

CTL Response toMycobacterium tuberculosis: Identification of an Immunogenic Epitope in the 19-kDa Lipoprotein

AbstractThe successful resolution of infection with Mycobacterium tuberculosis (M.tb) is believed to involve the induction of CTLs that are capable of killing cells harboring this pathogen, although little information is known about the MHC restriction or fine specificity of such CTLs. In this study, we used knowledge of the HLA-A*0201-binding motif and an immunofluorescence-based peptide-binding assay to screen for potential HLA-A*0201-binding epitopes contained in the 19-kDa lipoprotein of M.tb (M.tb19). CD8+ T cells derived from HLA-A*0201+ patients with active tuberculosis (TB) as well as tuberculin skin test-positive individuals who had no history of TB were used as effector cells to determine whether these epitopes are recognized by in vivo-primed CTLs. An in vitro vaccination system using HLA-A*0201+ dendritic cells (DCs) as APCs was used to determine whether these epitopes can sensitize naive CD8+ T cells in vitro, leading to the generation of Ag-specific CTLs. The results show that an HLA-A*0201-binding peptide comprised of residues 88 to 97 of M.tb19 (P88–97) is recognized by circulating CD8+ CTLs from both healthy tuberculin skin test-positive individuals and patients with active TB but not by tuberculin skin test-negative subjects. Moreover, dendritic cells pulsed with this peptide induced class I MHC-restricted CTLs from the T cells of healthy unsensitized persons. Finally, CTL lines that were specific for P88–97 were shown to lyse autologous monocytes that had been infected acutely with the H37Ra strain of M.tb. These results demonstrate that M.tb19 elicits HLA class I-restricted CTLs in vitro and in vivo that recognize endogenously processed Ag. Epitopes of the type identified here may prove useful in the design of an M.tb vaccine.

Tuberculosis: an update.

1. Rosalind S. Abernathy, MD* 1. 2. *Associate Professor of Pediatrics, University of Arkansas for Medical Sciences; Pediatric Consultant, Tuberculosis, Arkansas State Department of Health, Little Rock, AR. 1. The majority of tuberculosis cases in children are from high-risk populations, that is, African-Americans, Hispanics, immigrants, and those living in poverty and in the inner cities. 2. The only acceptable tuberculin skin test is the intradermal Mantoux test with purified protein derivative (PPD), and three levels of positivity now are accepted. Children exposed to active disease who have findings suggestive of tuberculosis or who have human immunodeficiency virus (HIV) infection are positive at 5 to 9 mm; other high-risk groups are positive at 10 mm. 3. Diagnosis of childhood tuberculosis depends on a high index of suspicion coupled with suggestive epidemiologic data, tuberculin skin test results, and chest radiographic findings. Cultures are not routinely positive, and results are available only after treatment must be started. 4. Treatment is a uniform 6-month course of isoniazid, rifampin, and pyrazinamide for 2 months followed by 4 months of isoniazid and rifampin daily or twice weekly. Additional drugs are needed in cases of drug resistance. 5. Chemoprophylaxis for all children who have a positive tuberculin reaction will prevent future disease. Despite the availability of effective antituberculosis drugs since 1952, tuberculosis remains an important cause of morbidity, mortality, and health care cost in the United States. Tuberculosis case rates declined at a rate of 6% annually for more than 20 years until 1985 when they leveled off (Fig. 1⇓). Factors responsible for this include human immunodeficiency virus (HIV) infection; immigration of individuals from countries where tuberculosis rates are 10 to 30 times that of the United States; transmission of disease in hospitals, homeless shelters, and prisons; and poverty, overcrowded living, and poor access to medical care. While all this was occurring, funds for tuberculosis control by public health programs declined. Fortunately, the number of cases reported annually has decreased by 8.7% in the past 2 years, probably …

Potential role for interleukin-10 in the immunosuppression associated with kala azar.

Patients with acute kala azar are generally nonreactive in a number of immunologic assays, including T cell proliferation and generation of macrophage-activating cytokines, principally IFN-gamma, in response to leishmania antigens in vitro. To test for potential immunosuppressive factors, a series of T cell lines and clones were established from patients with acute kala azar, from patients after chemotherapy for kala azar, and from skin test-positive adults from the same endemic region. Although CD4+ T cell lines and clones could be readily established from the skin test-positive adults, lines and clones from acute or treated patients were heavily biased in expression of CD8+. The CD8+ cells from acute patients did not themselves release cytokines in response to leishmania antigens in vitro, but markedly affected the cytokine profile of peripheral blood mononuclear cells isolated 1 yr later after recovery. Addition of the CD8+ cells caused inhibition of lymphoproliferation and IFN-gamma release, with augmentation of IL-6 and IL-10 release. The inhibitory effects of the CD8+ cells could be partially abrogated by antibodies to IL-10 but not by antibodies to IL-4. Analysis of four patients with acute kala azar demonstrated release of IL-10 that could not be demonstrated in supernatants from asymptomatic skin test-positive individuals. Generation of IL-10 may contribute to the profound suppression of IFN-gamma release that occurs during kala azar due to Leishmania chagasi.

Allergenicity of the cat flea (Ctenocephalides felis felis)

Adult fleas, spent and unspent culture media were extracted and the radio-allergosorbent test (RAST) performed with sera of 48 cat flea skin test-positive individuals from the Tampa Bay area of Florida. Sixteen sera (33.6%) had a positive RAST to the cat flea extract prepared in our laboratory [1.7-11.4% of the total counts (TC) added]. Six of the 16 sera (12.5%) also contained specific IgE to allergens in the spent medium (0.8-3.3% TC). The allergen composition and strength were studied by RAST inhibition of two commercial cat flea extracts and compared with our in-house flea extract. The results demonstrated similar allergen compositions and different potencies. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the in-house flea extract showed several Coomassie blue-stained bands (10-85 kD). SDS-PAGE immunoblots revealed five IgE-binding bands at 34, 35, 39, 54 and 60 kD. Flea allergens were quantified in eight house dust samples using RAST inhibition assays and expressed as RAST inhibition units; five of these samples contained detectable levels. Cat flea allergens may contribute to the allergenicity of house dust in areas of heavy flea infestation.

Serum IgE antibodies to Trichophyton in patients with urticaria, angioedema, asthma, and rhinitis: Development of a radioallergosorbent test

A series of patients was identified who demonstrated immediate positive skin tests to intradermal Trichophyton extract. These skin responses did not correlate with other fungal skin tests and were present both in atopic and nonatopic patients. The individuals demonstrating positive immediate skin tests included patients with urticaria, angioedema, asthma, and/or rhinitis, as well as five of 34 normal control subjects. Most skin test positive individuals had a history of local fungal infection and clinical signs suggestive of fungal infection. By use of Trichophyton tonsurans extract linked to Sepharose as the immunosorbent, it was possible to measure IgE antibodies in 26/30 sera from skin test positive individuals. With strongly positive sera, RAST bound up to 30% of the radiolabeled anti-IgE added. The results confirm that most skin test positive individuals have IgE-mediated hypersensitivity to Trichophyton. These observations support the older view that absorption of dermatophyte allergen through the skin should be considered as a possible cause of allergic disease.

Use of a urease-antibody conjugate in an enzyme immunoassay for the detection of blastomycosis.

A urease-antibody conjugate was used in an enzyme-linked immunoassay (ELISA) for the detection of antibodies in blastomycosis. A Blastomyces dermatitidis immunodiffusion antigen was used as the reference antigen in a solid phase indirect ELISA procedure and the endpoints were determined visually. Urease ELISA results on serum specimens from patients with blastomycosis compared favorably (90%) with results obtained spectrophotometrically by the alkaline phosphatase enzyme system. Specificity was evaluated with assays on sera from patients with histoplasmosis (20% cross reactivity), coccidioidomycosis (0% cross reactivity) and on Histoplasma capsulatum skin-test positive individuals (0% cross reactivity). The ease of performance of the urease ELISA combined with no requirements for specialized spectrophometric equipment are factors that favor the continued development of the test as an alternative serodiagnostic method. The assay may prove to be useful and a valuable adjunct to fungal antibody screening procedures.

Leucocyte adherence inhibition assay for cell-mediated immunity and immunodiagnosis of pancreatic cancer.

The present study was conducted to determine whether the leucocyte adherence inhibition (LAI) assay was dependent on cell-mediated immunity and whether it was of potential use in diagnosis of pancreatic cancer. The LAI response was significantly positive in 15 PPD skin-test positive individuals but it was abated by pretreatment of sensitized mononuclear cells with anti-T cell antibody (OKT3) or by depletion of monocytes. Therefore, the LAI assay is probably related to cell-mediated immunity. The LAI assay was positive in 13 of 16 patients with pancreatic cancer using pancreatic cancer extract; however, a positive reaction was not found in 11 cases of chronic pancreatitis and 10 cases of hepatocellular carcinoma. Thus, the LAI assay appears rather specific. Mononuclear cells of pancreatic and gastric cancer patients showed LAI reactivity to autologous tumor extracts.

Initial clinical and immunologic evaluation of a new phase I Q fever vaccine and skin test in humans.

A new phase I Q fever skin test was administered to 74 subjects. Thirty-eight had less than 8 mm and 36 had greater than or equal to 10 mm erythema at 24 hr. Only 14 had circulating antibody. Three skin test-positive and 17 skin test-negative, seronegative individuals subsequently received 6 or 30 micrograms of vaccine in a single dose. All skin test-positive individuals and one skin test-negative individual developed mild local reactions. Seventeen of 18 recipients developed fluorescent antibody to phase II antigen, and five developed positive phase II complement fixation titers. Serial assays of specific lymphocyte proliferation (LT) performed in 15 individuals revealed an increase in phase II LT in nine and an increase in phase I LT in six. All local reactions occurred in individuals with preexisting phase II LT. On the basis of these results, this vaccine and skin-test preparation appear safe, effective, and promising for eventual use in at-risk personnel.

Enhancement of nitroblue tetrazolium dye reduction by leucocytes exposed to a factor released from sensitised lymphocytes.

Leucocytes from purified protein derivative (PPD) skin test positive individuals, after exposure to PPD in vitro, show a significant increase in nitroblue tetrazolium (NBT) dye reduction when compared to leucocytes from PPD negative donors. The active principle was shown to be soluble, and was released from lymphocytes after a rapid, immunologically specific interaction with the sensitising antigen.