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Ultrastructural and molecular characterization of Pneumocystis carinii isolated from a rhesus monkey (Macaca mulatta)
I Durand-Joly1, A E Wakefield, R J Palmer
1Department of Microbiology of Ecosystems, Pasteur Institute of Lille, France.
Abstract:
High levels of heterogeneity have been observed among isolates of Pneumocystis carinii derived from different mammalian host species. We report the characterization of P. carinii isolated from a rhesus monkey (Macaca mulatta), which was immunosuppressed as a result of infection with a chimeric simian-human immunodeficiency virus (SHIVsbg). Histopathological examination showed evidence of severe P. carinii pneumonia with a large predominance of trophozoite forms. Alveolitis consisted of typical foamy, honeycomb exudate, with only a few alveolar macrophages. The lung inflammatory response was rather moderate without type-2 pneumocyte hyperplasia or collagenosis. P. carinii organisms were sometimes observed in the bronchiolar lumen. Ultrastructurally, macaque-derived P. carinii was more similar to human- or rabbit-derived parasites than to mouse-derived P. carinii. Molecular studies were carried out on the macaque-derived P. carinii DNA at two genetic loci: the genes encoding the mitochondrial large subunit ribosomal RNA (mt LSU rRNA) and the mitochondrial small subunit ribosomal RNA (mt SSU rRNA). Comparison of the DNA sequences with those from P. carinii isolated from eight other host species demonstrated that the macaque-derived P. carinii was genetically distinct at both loci, and was more closely related to human-derived P. carinii than to P. carinii derived from non-primate sources. We propose that macaque-derived P. carinii be named Pneumocystis carinii f.sp. macacae.
Insights
Pneumocystis carinii from rhesus monkeys shows genetic distinctiveness, closely resembling human strains. This finding suggests a specific Pneumocystis carinii subspecies in macaques, impacting host-pathogen research.
Area of Science:
- Mycology
- Immunology
- Primate Virology
Background:
- Pneumocystis carinii exhibits significant heterogeneity across mammalian hosts.
- Immunosuppression in rhesus monkeys due to SHIV infection can lead to opportunistic infections like P. carinii pneumonia.
Purpose of the Study:
- To characterize Pneumocystis carinii isolated from an immunosuppressed rhesus monkey.
- To compare macaque-derived P. carinii with isolates from other host species using ultrastructural and molecular methods.
Main Methods:
- Histopathological examination of lung tissue.
- Ultrastructural analysis of P. carinii morphology.
- Molecular characterization of mitochondrial ribosomal RNA genes (mt LSU rRNA and mt SSU rRNA).
Main Results:
- Severe P. carinii pneumonia was observed, predominantly trophozoite forms.
- Ultrastructurally, macaque P. carinii resembled human and rabbit isolates more than mouse isolates.
- Molecular analysis revealed genetic distinctiveness at both mt LSU rRNA and mt SSU rRNA loci, with closer relation to human P. carinii.
Conclusions:
- Macaque-derived P. carinii is genetically distinct and more closely related to human isolates than non-primate isolates.
- A new subspecies, Pneumocystis carinii f.sp. macacae, is proposed for macaque-derived P. carinii.
- This research contributes to understanding P. carinii evolution and host specificity.