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Immunohistochemistry of Pneumocystis carinii infection
S J Radio1, S Hansen, J Goldsmith
1Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha.
Abstract:
Pneumocystis carinii is the pre-eminent pulmonary pathogen and leading cause of death in patients with acquired immunodeficiency syndrome (AIDS). The diagnosis of this organism depends upon the morphologic demonstration of the cyst wall, trophozoite, or sporozoite in specimens from the lower respiratory tract. A variety of histochemical stains have been used to identify P. carinii, each with considerable limitations in specificity. Extrapulmonary spread and unusually destructive pulmonary patterns associated with P. carinii, although once considered rare, are seen occasionally in patients with AIDS. Traditional stains have proven to be less reliable in extrapulmonary sites. In 13 patients with AIDS, we stained formalin-fixed paraffin-embedded autopsy lung and other visceral organ sections using monoclonal antibody 3F6 (Dako, Santa Barbara, CA) to P. carinii. The antibody stained P. carinii in the lungs of seven patients with P. carinii pneumonia by Gomori methenamine silver stain (GMS). Numerous aggregates of P. carinii cysts were marked within alveoli, as is usually seen with other stains. No antibody staining was present in autopsy lung sections from non-AIDS patients with viral, fungal, or bacterial pneumonia. Clinically occult extrapulmonary P. carinii infection was seen in 4/7 (57%) patients with P. carinii pneumonia at autopsy. Monoclonal antibody to P. carinii stained organisms in all four (100%) patients with disseminated disease, as compared with 1/4 (25%) staining with GMS. Antibody staining of P. carinii was demonstrated in sections of thyroid, adrenal, and carinal lymph node (one patient), esophagus (one patient), kidney (one patient), and heart, thyroid, kidney, adrenal, liver, stomach, pancreas, spleen, and bone marrow (one patient).(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Pneumocystis pneumonia (PCP) is a leading cause of death in AIDS patients. A new monoclonal antibody effectively detects Pneumocystis carinii in lungs and extrapulmonary sites, outperforming traditional stains.
Area of Science:
- Medical Mycology
- Immunopathology
- Diagnostic Microbiology
Background:
- Pneumocystis carinii is a major opportunistic pathogen, particularly in individuals with acquired immunodeficiency syndrome (AIDS).
- Accurate diagnosis of P. carinii infections relies on identifying the organism in respiratory specimens, but traditional stains have limitations.
- Extrapulmonary spread of P. carinii, once rare, is increasingly observed in AIDS patients, posing diagnostic challenges.
Purpose of the Study:
- To evaluate the efficacy of a monoclonal antibody (3F6) for detecting P. carinii in formalin-fixed paraffin-embedded tissues.
- To compare the diagnostic performance of the monoclonal antibody with Gomori methenamine silver stain (GMS) in AIDS patients.
- To assess the utility of the antibody in identifying extrapulmonary P. carinii infections.
Main Methods:
- Autopsy lung and visceral organ sections from 13 AIDS patients were stained using monoclonal antibody 3F6.
- Sections were also stained using Gomori methenamine silver stain (GMS) for comparison.
- Control sections from non-AIDS patients with other pneumonias were included.
Main Results:
- Monoclonal antibody 3F6 successfully stained P. carinii in the lungs of seven patients with P. carinii pneumonia (PCP).
- Clinically occult extrapulmonary P. carinii infections were detected in 57% of PCP patients at autopsy using the antibody.
- The monoclonal antibody demonstrated superior sensitivity (100%) compared to GMS (25%) in disseminated disease cases.
Conclusions:
- Monoclonal antibody 3F6 is a sensitive and specific tool for diagnosing P. carinii infections, including extrapulmonary disease, in AIDS patients.
- This antibody offers improved diagnostic capabilities over traditional stains like GMS, especially in disseminated cases.
- The findings highlight the importance of considering extrapulmonary P. carinii in immunocompromised individuals.