Elimination of false-positive serum reactivity in latex agglutination test for cryptococcal antigen in human immunodeficiency virus-infected population

Flow cytometry crossmatch reactivity with pronase-treated T cells induced by non-HLA autoantibodies in human immunodeficiency virus-infected patients

Pronase treatment is used in the flow cytometry crossmatch (FCXM) to prevent nonspecific antibody binding on B cells. However, we have observed unexpected positive results with pronase-treated T cells in human immunodeficiency virus (HIV)-infected patients. In this study, 25 HIV-infected patients without HLA antibodies were tested with pronase-treated and nontreated cells. HIV-positive sera were pretreated with reducing agents and preabsorbed with pronase-treated and nontreated T or B cells before crossmatching. All patients displayed FCXM reactivity with pronase-treated T cells but not with nontreated T cells. None of the patients exhibited FCXM reactivity with pronase-treated and nontreated B cells. These patients displayed FCXM reactivity with pronase-treated CD4+ and CD8+ T cells but not with their nontreated counterparts. Preabsorption with pronase-treated T cells reduced the T cell FCXM reactivity. Preabsorption with pronase-treated B cells or nontreated T and B cells did not have any effect on the T cell FCXM reactivity. Pretreatment with reducing agents did not affect the T cell FCXM reactivity. 15 of 21 HIV-infected kidney allograft recipients with pronase-treated T cell FCXM reactivity display long-term graft survival (1193±631days). These data indicate that HIV-infected patients have nondeleterious autoantibodies recognizing cryptic epitopes exposed by pronase on T cells.

Cross-reactivity in Cryptococcus antigen latex agglutination test in two commercial kits

This article presents an examination of the cross-reactivity of pathogenic fungi with Cryptococcus neoformans in two commercial Cryptococcus antigen latex agglutination tests performed across 39 fungal strains. Some fungi were newly indicated as Cryptococcus cross-reactive, and the two kits showed differences in cross-reactive fungi.

Rare Association of Severe Cryptococcal and Tuberculosis in Central Nervous System in a case of Sarcoidosis

Sarcoidosis is a multisystem noncaseating granulomatous disease with a propensity for lung, eye, and skin which recently have been proposed that mycobacterium tuberculosis may contribute in its pathogenesis, and rarely involves central nervous system (CNS). Despite CD4+ lymphocytopenia, sarcoidosis by itself does not increase risk of opportunistic infections other than cryptococcosis. Nonetheless, simultaneous association of CNS cryptococcosis and tuberculosis infection remains extremely rare event in immunocompetent states, and has not been reported in sarcoidosis yet. We here presented such a case in a 42 years old man, a known case of sarcoidosis with diagnostic and therapeutic difficulties were encountered in a fourteen-month-long hospitalization period.

Central nervous system paracoccidioidomycosis in an AIDS patient: case report

Up to now, over 200 patients with paracoccidioidomycosis (PCM) associated to HIV infection have already been reported; however, the central nervous system involvement in this coinfection was rarely reported. This paper presents a 35-year-old Brazilian male AIDS patient who developed pulmonary PCM successfully treated with itraconazole. At the antiretroviral therapy starting, he had 32 CD4(+) T cells baseline count and high viral load levels. After 9 months, he presented severe fungal meningoencephalitis diagnosed by sublenticular enhanced nodular lesion at computerized tomography and magnetic resonance brain imaging and a positive Paracoccidiodes brasiliensis smear and culture from cerebrospinal fluid. At the time, a sixfold increase in CD4(+) T cell count and undetectable viral load level were evidenced. The patient received amphotericin B during 1 year presenting slow but progressive clinical improvement, and he is currently asymptomatic and without neurological disabilities. To our knowledge, this is the second case report of a patient with neuroparacoccidioidomycosis associated to HIV infection.

Significance of antibody detection in the diagnosis of cryptococcal meningitis

Cryptococcus neoformans is the causative agent of Cryptococcosis, a chronic and life-threatening infection common in AIDS patients. Sonicated proteins of cryptococci were reported to contain antigenic properties. In the present study antigens are prepared from cryptococcal culture filtrate and by sonication. Secretory antigens are prepared by precipitation of culture filtrate using saturated ammonium sulfate followed by dialysis. Prepared antigens are tested for the presence of antibodies in the CSF samples of cryptococcal meningitis cases by ELISA. Comparison is made between India ink staining, latex antigen test, and the antibodies to the sonicated and secretory antigens. The results indicate that although antigen could be detected in the majority of samples, antibody could also be detected to the extent of 80-85%. It is interesting to note that some samples that were negative for India ink staining also showed high antibody responses. Hence, antibody detection could be a valuable marker in association with India ink staining for the early diagnosis of the cryptococcal infection. This test may also counter false positivity encountered in latex antigen test. Antibody detection assay would be a viable alternative, which has 83% sensitivity and 100% specificity. Thus the presently described test aids in immunodiagnosis of cryptococcal infection.

Detection of Cryptococcus by conventional, serological and molecular methods

The rising incidence of cryptococcosis in India is posing a serious threat. Due to lack of sensitive methods for diagnosis, high morbidity and mortality are associated with the disease. Early diagnosis is essential to prevent serious complications. Therefore, we attempted to find highly sensitive and specific detection methods. A comparative evaluation of the detection of cryptococcosis was done by conventional (direct microscopy and culture) and rapid diagnostic [latex agglutination test (LAT), enzyme immunoassay (EIA) and PCR] methods. The study was done on 359 samples from 52 positive patients and 30 negative controls in an Indian set-up. Evaluation was done for cerebrospinal fluid (CSF), serum and urine separately. The diagnostic value of the tests was assessed in pre-treatment samples, and follow-up tests were also done on samples obtained after initiation of treatment. PCR had the highest sensitivity, followed by EIA and LAT, both before and after treatment. The positive detection by LAT, EIA and PCR was the longest in CSF (>90 days), followed by serum (∼65 days) then urine (∼45 days) after initiation of treatment. Our results indicated that the sensitivity and specificity of PCR and EIA were comparable in urine, CSF and serum for diagnosis of cryptococcosis.

Cryptococcosis

In the past 2 decades, Cryptococcus has emerged in its clinical significance and as a model yeast for understanding molecular pathogenesis. C neoformans and C gattii are currently considered major primary and secondary pathogens in a wide array of hosts that are known to be immunocompromised or apparently immunocompetent. A recent outbreak of C gattii infections further underscores the clinical importance of the yeast through its epidemiology and pathogenicity features. With an enlarging immunosuppressed population caused by HIV infection, solid organ transplantation, and clinical use of potent immunosuppressives, such as cancer chemotherapy, monoclonal antibodies, and corticosteroids, this fungus has become a well-established infectious complication of modern medicine. This article examines current issues in cryptococcal infections, including new classification, epidemiology, pathogenesis, and specific clinical aspects.

Utility of routine testing of bronchoalveolar lavage fluid for cryptococcal antigen

All cryptococcal antigen (CrAg) testing performed at our institution between 1989 and 1994 was reviewed for utility of routinely testing of bronchoalveolar lavage fluid (BAL) for this antigen. Forty-two of 1,506 BAL specimens were positive. Seventeen of these were felt to represent false positives (sensitivity, 71%; positive predictive value, 0.59). The data on CrAg in cerebrospinal fluid and serum and the fungal culture and histological results of BAL specimens did not support continued, routine testing of BALs for CrAg to diagnose cryptococcosis.

Simple monitoring of antiretroviral therapy with a signal-amplification-boosted HIV-1 p24 antigen assay with heat-denatured plasma

OBJECTIVE

Virus load determination has become indispensable for the management of HIV patients, but depends on expensive assays of a low throughput. We evaluated whether a highly improved HIV-1 p24 antigen detection procedure which involves heat-mediated immune complex dissociation and signal-amplification-boosted enzyme-linked immunosorbent assay (ELISA) was suitable for antiretroviral treatment monitoring.

DESIGN AND METHODS

Virus load in plasma was determined for 127 plasma samples taken at 0, 2, 6, 12, 18, 24, 30 and 36 weeks from 23 patients with CD4+ T cells < 50 x 10(6)/l who received indinavir 800 mg three times daily in addition to prior antiretroviral treatment. Tests included polymerase chain reaction (PCR) for viral RNA, measured prospectively with the Roche Amplicor kit, and retrospective batch testing of heat-denatured samples for p24 antigen by the DuPont HIV-1 p24 Core Profile ELISA linked with a tyramide signal amplification step. Particle-associated reverse transcriptase (RT) by the product-enhanced RT (PERT) assay was determined as an independent third-opinion viral load marker.

RESULTS

p24 antigen was detected as sensitively as viral RNA. Overall detection during a median observation time of 25 weeks (range, 0-39) amounted to 75.6% for antigen and 73.6% for RNA. The antigen detection limit was 0.2 pg/ml. Antigen was detectable in all 23 baseline samples, whereas RNA was undetectable in one. Antigen and RNA levels in 79 samples positive for both markers correlated with r = 0.714 (P < 0.0001). Average changes in levels of p24 antigen and RNA at eight timepoints correlated with r = 0.982 (P < 0.0001). In individual patients, the two parameters behaved similarly, and in certain cases virtually identically. RT activity was measurable in all samples.

CONCLUSIONS

The performance of this antigen detection procedure is comparable to RNA PCR, thus providing a simple, high throughput alternative in monitoring the efficacy of antiretroviral treatment.

Cryptococcosis in the era of AIDS--100 years after the discovery of Cryptococcus neoformans

Although Cryptococcus neoformans and cryptococcosis have existed for several millennia, a century has passed since the discovery of this encapsulated yeast and its devastating disease. With the advent of the AIDS pandemic, cryptococcal meningitis has emerged as a leading cause of infectious morbidity and mortality and a frequently life-threatening opportunistic mycosis among patients with AIDS. Both basic and clinical research have accelerated in the 1990s, and this review attempts to highlight some of these advances. The discussion covers recent findings, current concepts, controversies, and unresolved issues related to the ecology and genetics of C. neoformans; the surface structure of the yeast; and the mechanisms of host defense. Regarding cell-mediated immunity, CD4+ T cells are crucial for successful resistance, but CD8+ T cells may also participate significantly in the cytokine-mediated activation of anticryptococcal effector cells. In addition to cell-mediated immunity, monoclonal antibodies to the major capsular polysaccharide, the glucuronoxylomannan, offer some protection in murine models of cryptococcosis. Clinical concepts are presented that relate to the distinctive features of cryptococcosis in patients with AIDS and the diagnosis, treatment, and prevention of cryptococcosis in AIDS patients.

Interference by hydroxyethyl starch used for vascular filling in latex agglutination test for cryptococcal antigen

The glucuronoxylomannan component of the Cryptococcus neoformans capsular polysaccharide confers serotype specificity, and its detection in cerebrospinal fluid or serum by the latex agglutination test is used for diagnosis. Low-molecular-weight hydroxyethyl starches can be used as an alternative to albumin for vascular filling. This study reports the occurrence of a false-positive result with the Pastorex Cryptococcus test (Sanofi Diagnostics Pasteur, Marnes la Coquette, France) for a patient receiving hydroxyethyl starch characterized by a substitution ratio of 0.6 (Elohes, Biosedra, Sèvres, France).