Pushing the envelope: Immune mechanism and application landscape of macrophage-activating lipopeptide-2

Mycoplasma fermentans can cause respiratory diseases, arthritis, genitourinary tract infections, and chronic fatigue syndrome and have been linked to the development of the human immunodeficiency virus. Because mycoplasma lacks a cell wall, its outer membrane lipoproteins are one of the main factors that induce inflammation in the organism and contribute to disease development. Macrophage-activating lipopeptide-2 (MALP-2) modulates the inflammatory response of monocytes/macrophages in a bidirectional fashion, indirectly enhances the cytotoxicity of NK cells, promotes oxidative bursts in neutrophils, upregulates surface markers on lymphocytes, enhances antigen presentation on dendritic cells and induces immune inflammatory responses in sebocytes and mesenchymal cells. MALP-2 is a promising vaccine adjuvant for this application. It also promotes vascular healing and regeneration, accelerates wound and bone healing, suppresses tumors and metastasis, and reduces lung infections and inflammation. MALP-2 has a simple structure, is easy to synthesize, and has promising prospects for clinical application. Therefore, this paper reviews the mechanisms of MALP-2 activation in immune cells, focusing on the application of MALP-2 in animals/humans to provide a basis for the study of pathogenesis in Mycoplasma fermentans and the translation of MALP-2 into clinical applications.

in patient samples previously investigated for Mycoplasma pneumoniae infection

OBJECTIVES

To determine the presence and genotypic macrolide susceptibility of Mycoplasma amphoriforme, and the presence of Ureaplasma spp. and Mycoplasma fermentans among clinical samples from England previously investigated for Mycoplasma pneumoniae.

METHODS

Quantitative and conventional PCR methods were used to retrospectively screen a collection of 160 clinical samples previously submitted to Public Health England (PHE) for the detection of M. pneumoniae between October 2016 and December 2017. Samples which were positive for M. amphoriforme DNA were further investigated for mutations associated with genotypic macrolide resistance by sequencing domain V of the 23s rRNA.

RESULTS

M. amphoriforme was detected in 10/160 samples (6.3%), Ureaplasma parvum was detected in 4/160 samples (2.5%), and M. fermentans was not detected in any samples (0/160). Of the nine individuals (two samples were from the same patient) in which M. amphoriforme was detected, eight were male (age range 10-60 years) and one was female (age range 30-40 years). One individual with cystic fibrosis was positive for both M. amphoriforme and U. parvum. All M. amphoriforme DNA was genotypically susceptible to macrolides.

CONCLUSIONS

Mycoplasma amphoriforme was found in clinical samples, including lower respiratory tract samples of patients with pneumonia. In the absence of other respiratory pathogens, these data suggest a potential role for this organism in human disease, with no evidence of acquired macrolide resistance. Ureaplasma parvum was detected in cerebrospinal fluid and respiratory tract samples. These data suggest that there is a need to consider these atypical respiratory pathogens in future diagnostic investigations.

Analysis of DnaK Expression from a Strain of Mycoplasma fermentans in Infected HCT116 Human Colon Carcinoma Cells

Several species of mycoplasmas, including Mycoplasma fermentans, are associated with certain human cancers. We previously isolated and characterized in our laboratory a strain of human mycoplasma M. fermentans subtype incognitus (MF-I1) able to induce lymphoma in a Severe Combined Immuno-Deficient (SCID) mouse model, and we demonstrated that its chaperone protein, DnaK, binds and reduces functions of human poly-ADP ribose polymerase-1 (PARP1) and ubiquitin carboxyl-terminal hydrolase protein-10 (USP10), which are required for efficient DNA repair and proper p53 activities, respectively. We also showed that other bacteria associated with human cancers (including Mycoplasmapneumoniae, Helicobacterpylori, Fusobacteriumnucleatum, Chlamydiathrachomatis, and Chlamydia pneumoniae) have closely related DnaK proteins, indicating a potential common mechanism of cellular transformation. Here, we quantify dnaK mRNA copy number by RT-qPCR analysis in different cellular compartments following intracellular MF-I1 infection of HCT116 human colon carcinoma cells. DnaK protein expression in infected cells was also detected and quantified by Western blot. The amount of viable intracellular mycoplasma reached a steady state after an initial phase of growth and was mostly localized in the cytoplasm of the invaded cells, while we detected a logarithmically increased number of viable extracellular bacteria. Our data indicate that, after invasion, MF-I1 is able to establish a chronic intracellular infection. Extracellular replication was more efficient while MF-I1 cultured in cell-free axenic medium showed a markedly reduced growth rate. We also identified modifications of important regulatory regions and heterogeneous lengths of dnaK mRNA transcripts isolated from intracellular and extracellular MF-I1. Both characteristics were less evident in dnaK mRNA transcripts isolated from MF-I1 grown in cell-free axenic media. Taken together, our data indicate that MF-I1, after establishing a chronic infection in eukaryotic cells, accumulates different forms of dnaK with efficient RNA turnover.