Experimental Pulmonary Pneumocystis Carinii Infection in Rabbits

Abstract

Moderate to marked interstitial pneumonitis with many Pneumocystis organisms was found in rabbits treated with cortisone and antibiotics and instilled intranasally with a suspension of lung tissue from either a patient or a rabbit with this infection. Organisms and pulmonary lesions of similar severity and frequency were present in controls treated in the same manner but instilled with either saline or a boiled suspension of normal human lung tissue. The administration of antibiotics and infected rabbit lung suspension only produced less marked lung changes with fewer organisms. Rare organisms and minute foci of pneumonitis were encountered in normal rabbits which had received neither hormone, antibiotics, nor inoculum. The pulmonary lesions in the cortisone-treated rabbits resembled closely the findings in patients with the subclinical form of Pneumocystis pneumonitis. They did not reproduce the massive lesions of widespread Pneumocystis pneumonia in infants. The findings indicate that latent pulmonary Pneumocystis infection was widespread in these rabbits but do not establish the transmission of the disease. The activation of latent infection was dependent on an impairment of host resistance which in these experiments was produced most effectively by the administration of cortisone. The differences between the experimental lesions and those of typical Pneumocystis pneumonia in infants suggest that in man an unknown defect of host defenses other than that induced by prolonged hormone administration accounts for the increased susceptibility to the infection. It is concluded that in the presence of widespread latent Pneumocystis infection the development of active disease is a manifestation of altered host resistance.

Decreased Production of Local Immunoglobulin A toPneumocystis cariniiin Bronchoalveolar Lavage Fluid from Human Immunodeficiency Virus-Positive Patients

“…Three week-old New Zealand White rabbits (250 g) were immunosuppressed by oral administration of 20 mg of azathioprine/kg of body weight three times weekly. Amoxicillin was added to drinking water daily (20 mg/liter) to inhibit bacterial infection (32,34). After 2 weeks, rabbits were euthanized and aseptic lung biopsies were performed.…”

Association of Primary Pneumocystis carinii Infection and Sudden Infant Death Syndrome

“…Experimental evidence shows that the host response pattern associated with primary P. carinii infection in otherwise healthy animals is milder [3][4][5] than that associated with the usually massive infection seen in an immunocompromised host. Data for humans are scant: P. carinii in low numbers or mild focal pneumonitis has rarely been reported as an autopsy finding for presumably immunocompetent children, and then the infection has been judged to be latent, incidental organisms [6].…”

Pneumocystis Carinii Pneumonitis A Review

“…The susceptibility of the organisms to pentamidinc and thcir morphology [5,11,13, 23, 321 is consistent with classification as a protozoan organism, but this data only constitutes indirect evidence.…”

“…ops very slowly. At least three to six weeks are neccssary for the disease to involve most of the lung parenchyma [4,6,11,21,32,54,551. Since it is almost exclusively an intra-alveolar parasite, the surrounding pulmonary alveolar septa would be expected to show the most tissue reaction and fibrosis.…”