Mycoplasma penetrans infection of Molt-3 lymphocytes induces changes in the lipid composition of host cells

Subversion of the Immune Response by Human Pathogenic Mycoplasmas

Mycoplasmas are a large group of prokaryotes which is believed to be originated from Gram-positive bacteria via degenerative evolution, and mainly capable of causing a wide range of human and animal infections. Although innate immunity and adaptive immunity play crucial roles in preventing mycoplasma infection, immune response that develops after infection fails to completely eliminate this bacterium under certain circumstances. Thus, it is reasonable to speculate that mycoplasmas employ some mechanisms to deal with coercion of host defense system. In this review, we will highlight and provide a comprehensive overview of immune evasion strategies that have emerged in mycoplasma infection, which can be divided into four aspects: (i) Molecular mimicry and antigenic variation on the surface of the bacteria to evade the immune surveillance; (ii) Overcoming the immune effector molecules assaults: Induction of detoxified enzymes to degradation of reactive oxygen species; Expression of nucleases to degrade the neutrophil extracellular traps to avoid killing by Neutrophil; Capture and cleavage of immunoglobulins to evade humoral immune response; (iii) Persistent survival: Invading into the host cell to escape the immune damage; Formation of a biofilm to establish a persistent infection; (iv) Modulation of the immune system to down-regulate the intensity of immune response. All of these features increase the probability of mycoplasma survival in the host and lead to a persistent, chronic infections. A profound understanding on the mycoplasma to subvert the immune system will help us to better understand why mycoplasma is so difficult to eradicate and ultimately provide new insights on the development of therapeutic regimens against this bacterium in future.

Preparation of reference stocks suitable for evaluation of alternative NAT-based mycoplasma detection methods

AIMS

The aim of this study was to optimize conditions for preparation and cryopreservation of mycoplasma reference materials suitable to evaluate alternative nucleic acid testing (NAT)-based assays and to compare their limits of detection (LODs) with those of conventional culture-based methods.

METHODS AND RESULTS

Acholeplasma laidlawii, Mycoplasma gallisepticum and Mycoplasma arginini stocks with low ratios of genomic copies to colony forming units (12, 8 and 4, respectively) harvested in early stationary phases of growth were preserved with different cryoprotective agents (CPAs) under slow (1°C min(-1)), moderate (8°C min(-1)), fast (13°C min(-1)) and 'snapshot' (60°C min(-1)) cooling rates. Depending on mycoplasma species, increasing the cooling rate from slow to snapshot enhanced cell survival up to 5-fold. The addition of 10% (v/v) dimethyl sulfoxide (DMSO) and 15% (v/v) glycerol significantly improved cell survival of all tested strains. Cryoprotected stocks maintained high and stable titres for at least 1 year during storage at -80°C. Sonication of cell cultures prior to cryopreservation enhanced cell dispersion and reduced of GC/CFU ratios.

CONCLUSIONS

It is feasible to prepare stable reference stocks of cryopreserved mycoplasma cells suitable to reliably compare NAT- and culture-based mycoplasma testing methods.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study describes experimental results demonstrating the preparation and storage of highly viable and dispersed mycoplasma reference stocks suitable for comparing alternative NAT-and conventional culture-based mycoplasma detection methods.

Exogenous mycoplasmal p37 protein alters gene expression, growth and morphology of prostate cancer cells

We previously showed that the Mycoplasma hyorhinis-encoded protein p37 can promote invasion of cancer cells in a dose-dependent manner, an effect that was blocked by monoclonal antibodies specific for p37. In this study, we further elucidated changes in growth, morphology and gene expression in prostate cancer cell lines when treated with exogenous p37 protein. Incubation with recombinant p37 caused significant nuclear enlargement, denoting active, anaplastic cells and increased the migratory potential of both PC-3 and DU145 cells. Microarray analysis of p37-treated and untreated cells identified eight gene expression clusters that could be broadly classified into three basic patterns. These were an increase in both cell lines, a decrease in either cell line or a cell line-specific differential trend. The most represented functional gene categories included cell cycle, signal transduction and metabolic factors. Taken together, these observations suggest that p37 potentiates the aggressiveness of prostate cancer and thus molecular events triggered by p37 maybe target for therapy.

Interaction of mycoplasmas with host cells

The mycoplasmas form a large group of prokaryotic microorganisms with over 190 species distinguished from ordinary bacteria by their small size, minute genome, and total lack of a cell wall. Owing to their limited biosynthetic capabilities, most mycoplasmas are parasites exhibiting strict host and tissue specificities. The aim of this review is to collate present knowledge on the strategies employed by mycoplasmas while interacting with their host eukaryotic cells. Prominant among these strategies is the adherence of mycoplasma to host cells, identifying the mycoplasmal adhesins as well as the mammalian membrane receptors; the invasion of mycoplasmas into host cells including studies on the role of mycoplasmal surface molecules and signaling mechanisms in the invasion; the fusion of mycoplasmas with host cells, a novel process that raises intriguing questions of how microinjection of mycoplasma components into eukaryotic cells subvert and damage the host cells. The observations of diverse interactions of mycoplasmas with cells of the immune system and their immunomodulatory effects and the discovery of genetic systems that enable mycoplasmas to rapidly change their surface antigenic composition have been important developments in mycoplasma research over the past decade, showing that mycoplasmas possess an impressive capability of maintaining a dynamic surface architecture that is antigenically and functionally versatile, contributing to the capability of the mycoplasmas to adapt to a large range of habitats and cause diseases that are often chronic in nature.

Infection by Mycoplasma hyorhinis strongly enhances uptake of antisense oligonucleotides: a reassessment of receptor-mediated endocytosis in the HepG2 cell line

This paper shows that the approximately 66 kDa band, previously isolated from the HepG2 cell line as an oligonucleotide (ON) plasma membrane 'receptor', is induced by Mycoplasma infection. Moreover, this band has been identified as the invariant membrane protein of Mycoplasma hyorhinis, p70, based on ribosomal DNA sequencing combined with ON ligand blotting after p70 immunoprecipitation by a monoclonal antibody. Whereas antibiotic treatment of infected HepG2 cells strongly decreased ON capture, as measured by a biochemical assay, conversely, deliberate infection of HeLa cells with M.hyorhinis dramatically promoted ON uptake but did not affect receptor-mediated endocytosis of transferrin. This was confirmed by confocal microscopy of infected HepG2 cells, which also showed an indistinguishable labelling pattern after exposure of living cells to fluorescent ON and after p70 immunolabelling in permeabilised fixed cells. We propose that ON binds to p70 on M.hyorhinis attached at the cell surface, after which the complex is internalised by 'piggy-back' endocytosis.