Demyelination and wasting associated with polyomavirus infection in nude (nu/nu) mice

Nude (nu/nu) mice bearing human tumour heterografts were affected with posterior paralysis and wasting. There was demyelination and infection of the oligodendrocytes of the spinal cord with a papovavirus. Similar virus particles and inclusion bodies were found in the bronchial epithelium, which showed histopathological changes. Similar changes were shown by the epithelia of the renal pelvis, ureter and choroid plexus. The virus was found in a transplantable human tumour, and evidence of spread by contact was also obtained. Intracerebral injection of spinal cord suspension from infected mice resulted in virus infected cutaneous carcinomata, demyelination with virus particles in the oligodendrocytes and posterior paralysis with wasting in adult nude mice. The suspension injected intraperitoneally into newborn Syrian hamsters produced tumours similar to those produced by murine polyoma. No evidence of infection was found in mice from the colony of origin. The virus was identified as murine polyoma Wild Type A2.     

Pneumocystis carinii infection in corticosteroid-treated cats

Corticosteroids were administered to produce Pneumocystis carinii infection in cats. Six of 10 cats, injected intramuscularly for 97-141 days with 2 mg/cat twice weekly of betamethasone sodium phosphate, developed a light infection with P. carinii. Six of 7 cats, injected intramuscularly for 11-168 days with 10-25 mg/cat weekly of prednisolone acetate, also developed a light infection with P. carinii. There was no significant difference in the infection rate between the sexes and ages of the cats. Using Giemsa staining and Gomori's methenamine silver nitrate stain, P. carinii organisms were indistinguishable morphologically from human and rat P. carinii. The cysts and trophozoites were usually present singly or in small groups, and they always were adhering to the periphery of alveoli. The inflammatory changes were inconspicuous except for the fact that alveolar macrophages often were seen. Corticosteroid-treated cats should be useful in the study of experimental P. carinii infection. This is the first reported case of experimentally induced P. carinii infection in cats.     

T cell costimulatory molecule function determines susceptibility to infection with Pneumocystis carinii in mice

Loss of T cell number and function during HIV infection or secondary to pharmacologic immunosuppression renders individuals susceptible to opportunistic infections, including Pneumocystis carinii pneumonia. Because costimulatory receptors are critical for optimal T cell function, we hypothesized that these proteins would regulate susceptibility to opportunistic infections. We found that despite normal T cell numbers, mice deficient in the costimulatory molecules CD2 and CD28 spontaneously developed P. carinii pneumonia. In experiments using intratracheal injection of P. carinii organisms to induce infection, the loss of CD28 alone was sufficient to render mice susceptible to acute infection; however, the organism was eventually cleared. Examination of inflammatory responses to P. carinii revealed that mice deficient in both CD2 and CD28 accumulated CD8(+) T cells in their lungs in response to infection and demonstrated markedly reduced specific Ab titers. Analysis of cytokine profiles suggested that regulation of IL-10 and IL-15 may be important elements of the response to this pathogen. Thus, costimulatory molecule function is critical in determining the initial susceptibility to infection with P. carinii. Analysis of immunologic responses in these mice may provide important insights into the defects that render individuals susceptible to opportunistic infection, and provide opportunities for novel immunologically based therapies.     

Cellular immune response in Pneumocystis carinii infection

Pneumocystis carinii is an important pulmonary pathogen causing disease in immunocompromised individuals. The majority o f conditions predisposing to Pneumocystis pneumonia are associated with profound defects in cellular immunity. Although our understanding o f the host response to the organism is still limited, advances in antigen preparation and the availability o f animal models have permitted an improved understanding of some aspects o f the cell-mediated immune response to Pneumocystis. In this review, George Smulian and Sue Theus will highlight recent advances in our knowledge regarding the role of macrophages, T cells and cytokines in the response to the organism.     

Identification of Pneumocystis carinii in immunodeficient mice

Various procedures were utilized to determine the most sensitive, cost and labor effective techniques for detection of Pneumocystis carinii in immunologically compromised mice. Immunoperoxidase staining techniques that utilized polyclonal antibodies directed against purified rat or mouse P. carinii were more sensitive and specific than staining with Gomori's methenamine silver. Indirect immunofluorescence microscopy on frozen sections was comparable to immunoperoxidase staining, but lacked fine cytologic detail. Impression smears were of limited value when stained with Diff-Quik Stain, Harleco's Hemacolor, Wright-Giemsa or Wright-Leishman stains. However, cysts could be detected consistently in imprints stained with Gomori's methanamine silver. Transmission electron microscopy showed ultrastructural detail of P. carinii, but this technique was too costly and time consuming for routine use. Thus, because of its sensitivity and specificity, immunohistochemistry on paraffin sections was the most satisfactory method for screening and identifying P. carinii in lungs of immunocompromised mice.     

免疫抑制大鼠肺孢子菌合并呼吸道细菌感染的研究

目的 探讨免疫抑制兼肺孢子菌感染大鼠下呼吸道合并细菌感染的菌群种类及其影响因素.方法 用腹膜内注射地塞米松的方法建立免疫抑制大鼠并诱导肺孢子菌感染模型.免疫抑制的实验组动物再分为经呼吸道吸入乙醚麻醉组和不实施乙醚麻醉组,以了解乙醚对呼吸道感染的影响.此外,设不经任何处理的正常对照组.免疫抑制剂注射8周后处死大鼠,取肺组织制成肺印片,染色后进行肺孢子菌感染的病原学鉴定,同时取气管末端进行细菌培养和鉴定.结果 成功地建立了免疫抑制和肺孢子菌感染大鼠模型.乙醚麻醉组肺孢子菌感染率和菌体负荷均高于非乙醚麻醉组(P＜0.05).感染的菌种主要为双歧杆菌、大肠埃希菌、流感嗜血杆菌、丙酸丙酸杆菌、金黄色葡萄球菌、纤维单胞菌、放线菌及肺炎克雷伯杆菌.其中,麻醉组和非麻醉组下呼吸道细菌感染率有差异的是大肠埃希菌、流感嗜血杆菌、丙酸丙酸杆菌和金黄色葡萄球菌(P＜0.05).结论 用乙醚麻醉方法建立大鼠肺孢子菌模型能有效提高大鼠感染肺孢子菌感染率和感染度,下呼吸道感染细菌多为混合感染且受乙醚麻醉影响.     

Pneumocystis carinii infection in a pediatric tuberculosis hospital

An outbreak of pneumocytosis in a children's tuberculosis hospital was analyzed. The infection was characterized by few signs and favourable progress. Antibiotic therapy failed. To eliminate the outbreak of pneumocystosis in the hospital it was necessary to detect all the children with pneumocystosis and carriers of pneumocysts among the patients and medical staff, to use furazolidone for etiotropic treatment of the patients with pneumocystosis and to perform one-stage sanation of the carriers with antiparasitic agents.     

Delayed-type hypersensitivity response in mice to Pneumocystis carinii.

Resistance to Pneumocystis carinii infection appears to be mediated by T lymphocytes but the mechanism and subsets of T cells involved are poorly understood. We used the BALB/c mouse model to study the delayed-type hypersensitivity (DTH) response to rat P. carinii. Mice were sensitized to P. carinii for seven days and then challenged with P. carinii antigens in the right rear footpads and normal rat lung antigens in the left rear footpads. A typical DTH response was observed in the right footpads as evidenced by significant swelling and substantial mononuclear cell infiltration at 24-h post-challenge. The DTH response could be transferred to naive syngeneic mice by adoptively transferring spleen cells from P. carinii-sensitized mice. In addition, by using anti-thy-1, anti-mouse Ig, anti-L3T4 and anti-Lyt-2.2 monoclonal antibodies in in vitro cytolysis experiments, we were able to demonstrate that the DTH response was dependent upon T lymphocytes. The response appeared to require cooperation between both L3T4+ and Lyt 2+ subsets of T lymphocytes.     

Susceptibility of various animals to Pneumocystis carinii infection.

Pneumocystis carinii (Pc) is an important opportunistic pathogen of immune compromised hosts, and is known to infect various animals. The present study observed the infection status of 6 mammals and 3 strains of albino rats with Pc after suppression of their immunity. Methyl-prednisolone was injected once a week and tetracycline was supplied with water for 5 to 21 weeks. Hamsters, guinea pigs, rabbits, dogs, cats and pigs were negative by impression smear, and only the rats were found infected by Pc. All of the three strains of rats, Sprague-Dawley(SD), Wistar(W) and Fisher(F), were infected by Pc but W rats showed heavier degree of infection in earlier period than F or SD rats. The present findings suggest that W rat is the best among the animals used in the present study for production of Pc.     

Interstitial pneumonia in immunocompetent laboratory rats caused by natural infection with Pneumocystis carinii

Pneumocystis (P.) carinii is known to cause fatal pneumonia in immunocompromised rats. Cases of P. carinii interstitial pneumonia in immunocompetent rats have been shown histologically to present with perivascular lymphoid cuffs, which have previously been attributed to rat respiratory virus. This study aims to determine the prevalence and pathological characteristics of P. carinii in immunocompetent laboratory rats in experimental facilities in Japan. An epidemiological survey for this agent was performed using PCR to assess 1,981 immunocompetent rats from 594 facilities in Japan. We observed that 6 of the 1,981 rats (0.30%) from 4 out of 594 facilities (0.67%) were positive for P. carinii without infection of other known pathogens. Gross pulmonary lesions were found in 4 of the 6 affected rats. The lungs of these rats contained scattered dark red/gray foci. Histopathologically, the lungs exhibited interstitial pneumonia with lymphoid perivascular cuffs: Pneumocystis cysts were observed using Grocott’s methenamine silver stain. To our knowledge, this report is the first to reveal the prevalence of natural P. carinii infection in immunocompetent laboratory rats in Japan.     

Pneumocystis carinii mutations associated with sulfa and sulfone prophylaxis failures in immunocompromised patients

Recent studies have shown that mutations in two amino acid positions of the Pneumocystis carinii dihydropteroate synthase gene are significantly more common in immunocompromised patients with P. carinii pneumonia who fail sulfa or sulfone prophylaxis. This paper reviews the studies that suggest that these mutations may be responsible for some failures of prophylaxis in P. carinii.     

Delayed inflammatory response to Pneumocystis carinii infection in neonatal mice is due to an inadequate lung environment

Challenge of neonatal mice with an intranasal inoculation of Pneumocystis carinii results in a subclinical infection that takes 6 wk to resolve, whereas adult mice resolve a comparable challenge within 3 wk. This delayed clearance is due to a delayed inflammatory response in neonatal mice; however, the reason for this delay has been unknown. To determine whether the neonatal lung environment is sufficient to attract immunocompetent lymphocytes into the lungs, an adoptive transfer strategy was employed in which splenocytes from adult BALB/c mice were transferred into P. carinii-infected neonatal or adult SCID mice. All adults, but no pups, resolved their infections by day 37 postreconstitution. Despite reconstitution with adult splenocytes, pups had a negligible lung inflammatory response until day 24, whereas adult mice had activated CD4(+) and CD8(+) cells in the lung by day 13. The delay in neonates corresponded to delayed kinetics of expression of lung cytokines TNF-alpha and IFN-gamma mRNA and chemokines lymphotactin, RANTES, and macrophage inflammatory protein-1ss mRNA. Phagocytic cells from neonatal mice were significantly less efficient than adult cells at migrating to the draining lymph nodes after phagocytosing fluorescent beads. There were fewer dendritic cells and Ia(+) myeloid cells in the lungs of P. carinii-infected neonatal mice compared with adults. These data indicate that the lung environment of neonatal mice is insufficient for migration of T cells, due at least in part to inefficient phagocytosis and migration of APCs to the lymph nodes as well as delayed chemokine and TNF-alpha mRNA expression.     

Opportunistic Pneumocystis carinii infection in red-bellied tamarins (Saguinus labiatus).

P. carinii infection in red-bellied tamarins (Saguinus labiatus), born and maintained in a laboratory breeding colony, was examined by histopathologic examination postmortem. P. carinii cysts were detected in 6 of 10 red-bellied tamarins examined, by using Grocott's, toluidine blue O and immunostaining with avidin-biotin complex using antisera for rat-, simian-, and human-P. carinii. The results obtained from the present studies imply that P. carinii may be an important pathogen in this species.     

Generalized immune response to Pneumocystis carinii infection in the lung.

We studied inflammatory cells retrieved by bronchoalveolar lavage (BAL) from immunocompromised patients with or without Pneumocystis carinii pneumonia (PCP). Twenty-four patients with PCP, and 20 patients without PCP underwent lavages of both an uninvolved lobe and the lobe involved in pulmonary infection. Patients without P. carinii, had a significant increase (p less than 0.02) in the percentages of neutrophils (22 +/- 7.1%, mean +/- SEM) and lymphocytes (16 +/- 3.8%) in the involved lobe compared to those in the uninvolved area (neutrophils: 9 +/- 4.8%; lymphocytes: 10 +/- 2.4%). Patients with PCP, had no differences between the % neutrophils or % lymphocytes in the involved vs. uninvolved lobes. Patients with PCP had more (p less than 0.01) P. carinii in the upper lobe (23 +/- 4.6 P. carinii clusters/500 cells) than the middle lobe (11 +/- 3.6). In PCP, despite regional infections, there was a diffuse inflammatory response.