Genetic diversity and evolution of Pneumocystis fungi infecting wild Southeast Asian murid rodents.

Pneumocystis organisms are airborne-transmitted fungal parasites that infect the lungs of numerous mammalian species with strong host specificity. In this study, we investigated the genetic diversity and host specificity of Pneumocystis organisms infecting Southeast Asian murid rodents through PCR amplification of two mitochondrial genes and tested the co-phylogeny hypothesis among these fungi and their rodent hosts. Pneumocystis DNA was detected in 215 of 445 wild rodents belonging to 18 Southeast Asian murid species. Three of the Pneumocystis lineages retrieved in our phylogenetic trees correspond to known Pneumocystis species, but some of the remaining lineages may correspond to new undescribed species. Most of these Pneumocystis species infect several rodent species or genera and some sequence types are shared among several host species and genera. These results indicated a weaker host specificity of Pneumocystis species infecting rodents than previously thought. Our co-phylogenetic analyses revealed a complex evolutionary history among Pneumocystis and their rodent hosts. Even if a significant global signal of co-speciation has been detected, co-speciation alone is not sufficient to explain the observed co-phylogenetic pattern and several host switches are inferred. These findings conflict with the traditional view of a prolonged process of co-evolution and co-speciation of Pneumocystis and their hosts.

[Antibacterial immunity in respiratory tract: what role for the myeloid differentiation primary response protein 88 (MyD88) adaptor?]. / Immunité antibactérienne des voies respiratoires : quelle place pour la protéine adaptatrice myeloid diffentiation primary response protein 88 (MyD88) ?

As an essential interface between the external environment and the organism, the respiratory tract is particularly exposed to the potential injuries due to microorganisms, such as bacteria. Against these aggressions, the immune system has a key role, involving detection of germs followed by the establishment of innate and adaptive immune processes. During these responses, the adaptor protein MyD88 has a central place in the development of immune response: i) it contributes to innate immune response through the production of cytokines and chemokines, allowing recruitment and activation of effector cells; ii) it is involved secondarily in the development and orientation of antibacterial adaptive response, iii) and participates in sustaining immune homeostasis. Its importance is reflected in human pathology (MyD88 hereditary deficiency) by increasing susceptibility to few pathogenic bacteria responsible for respiratory infections which mainly occur in the upper respiratory tract. Since it has a key role, MyD88 is an essential factor for antibacterial immunity and more broadly for anti-infectious immunity. This protein might be therefore a possible therapeutic target.