Characterization of Virulence-Associated Traits in Mycoplasma penetrans Strains Acting as Likely Etiological Agents of Idiopathic Nongonococcal Urethritis.

Mycoplasma penetrans is an emerging pathogen with a reduced genome. This bacterium has only previously been cultured from individuals with chronic immunodeficiencies. Here we report the characteristics of 4 M. penetrans isolates from the urine of immunocompetent males with nongonococcal urethritis, in comparison with strain HF-2 from an immunocompromised patient. Several features exhibited distinct differences between these isolates and HF-2. Unlike HF-2, all 4 were resistant to azithromycin. They exhibited greater sialic acid-dependent binding to erythrocytes, gliding motility speed, and H2O2 production than HF-2. All new isolates produced thinner capsules than HF-2. Invasiveness varied, with some isolates being more invasive than HF-2 and some less invasive. Cytotoxicity to HeLa cells was similar to HF-2, and all strains could clear extracellular traps produced by innate immune cells. We conclude that subtle differences among M. penetrans strains may be critical for this organism to establish an infection in an otherwise healthy individual.

A simplified method for separating renal MPCs using SLAMF9.

Mononuclear phagocytes comprise an array of tissue-resident and monocyte-derived cells with important roles in tissue homeostasis and resistance to infection. Their diverse phenotypes make functional characterization within tissues challenging, because multiple surface markers are typically required for subset identification and isolation by cell sorting methods. Analysis of SLAMF9 expression within renal mononuclear phagocyte populations by multi-parametric flow cytometry indicates that SLAMF9 is a specific marker for identification of kidney-resident CD45+ CD11c+ MHC-II+ cells corresponding to prominent tissue-resident MPC populations derived from dendritic cell progenitors in adult mice. High SLAMF9 expression was sufficient to identify and sort these cells from disaggregated tissue using a user-operated cell sorter. The population can be further subdivided according to expression of CD11b and CD14 to identify IRF8high cDC1 cells and cleanly separate the CD11bhigh F4/80low and CD11bint F4/80high CD11c+ MPC subsets. Therefore, SLAMF9 expression allows for the identification and sorting of kidney-resident CD11b+ CD11c+ CD64+ F4/80+ CX3 CR1+ MHC-II+ MPCs without the need for complex antibody panels or reporter mice, simplifying isolation of these cells for study ex vivo.

Evidence for the loss and recovery of SLAMF9 during human evolution: implications on Dollo's law.

Signaling lymphocyte activation molecule family member 9 (SLAMF9) is a cell surface protein of the CD2/SLAM family of leukocyte surface receptors. It is conserved throughout mammals and has roles in the initiation of inflammatory responses and regulation of plasmacytoid dendritic cell function. Through comparison of reference sequences encoding SLAMF9 in human, mouse, and primate sequences, we have determined that the SLAMF9 gene underwent successive mutation events, resulting in the loss of the protein and subsequent recovery of a less stable version. The mutations included a single base pair deletion in the second exon and a change in the splice acceptor site of that same exon. These changes would have had the effect of creating and later repairing a frameshift in the coding sequence. These events took place since the divergence of the human lineage from the chimpanzee-human last common ancestor and represent the first known case of the functional loss and recovery of a gene within the human lineage.