Endospores of B subtilis are pyrogenic and activate Mono Mac 6 cells: importance of the CD14 receptor

Effect of moist heat sterilisation on the pyrogenicity of cell wall components from Staphylococcus aureus

As opposed to endotoxins very little is known about the heat resistance of Gram positive pyrogens. The aim of this study is to examine the pyrogenic activity of the cell wall components lipoteichoic acid and peptidoglycan from Staphylococcus aureus after moist heat sterilisation. The pyrogenic activity is determined as the ability of the substances to induce interleukin-6 secretion in Mono Mac 6 cells. The standard terminal moist heat sterilisation procedures (121 degrees C for 15min and 134 degrees C for 3min) are not able to inactivate the pyrogenic activity of S. aureus lipoteichoic acid and peptidoglycan. However after longer treatment times the pyrogenic activity of lipoteichoic acid is removed at both 121 degrees C and 134 degrees C. In contrast the activity of peptidoglycan is not removed after 160min at neither 121 degrees C nor 134 degrees C where only a 2-log reduction is obtained. In conclusion the terminal moist heat sterilisation procedures described by the European Pharmacopoeia are not able to inactivate the interleukin-6 inducing activity of S. aureus lipoteichoic acid and peptidoglycan.

Pyrogenicity of CpG-DNA in mice: role of interleukin-6, cyclooxygenases, and nuclear factor-κB

Bacterial DNA containing unmethylated cytosine-phosphate-guanosine motif (CpG-DNA) has been identified as a pathogen-associated molecular pattern, which is recognized by Toll-like receptors and activates immune cells to produce cytokines. The aim of the study was to characterize the ability of CpG-DNA to induce fever in mice. Intravenous administration of unmethylated CpG-DNA 1826 triggered an elevation of body temperature (Tb) lasting several hours. The magnitude of Tbelevation increased with an increase of dose of the oligonucleotide (administered in a range from 0.01 mg/kg to 1.0 mg/kg). A fever-like increase of Tbin mice was partially dependent on IL-6, as IL-6 deficient mice responded with reduced fever to the CpG-DNA 1826. Meloxicam and sulindac sulfide, inhibitors of cyclooxygenases, reduced fever in mice challenged with CpG-DNA 1826, indicating that the process may also depend on prostaglandins. In fact, plasma levels of prostaglandin E2, as well as IL-6, increased at 4 h postinjection of CpG-DNA 1826 into mice. These data demonstrate that the pathophysiological mechanism of the increase of Tbinduced by CpG-DNA 1826 is similar to fever induced by LPS. Both LPS and CpG-DNA 1826 failed to produce elevation of Tbin mice deficient for a nuclear factor-κB (NF-κB) gene, further supporting the hypothesis that the two pyrogens provoke fever, using the same components of the cellular signaling metabolism. However, parthenolide, an inhibitor of I-κB kinase reduced fever due to CpG-DNA 1826, and did not affect fever to LPS, suggesting that the two structurally dissimilar pyrogens may affect different intracellular pathways leading to the upregulation of NF-κB. In support of this hypothesis, we demonstrate that C3H/HeJ mice, known to exhibit a mutation in the Toll-like receptor-4 gene, do not respond with fever to LPS. They respond, however, with fever after injection of CpG-DNA 1826. We conclude that bacterial DNA shares with components of the bacterial wall the capacity to elicit fever and may, consequently, be part of a novel class of exogenous pyrogens.

Utilization of the human cell line HL-60 for chemiluminescence based detection of microorganisms and related substances

In this paper we describe a new pyrogen assay using the human leukemia cell line HL-60. The cell line is differentiated using all-trans retinoic acid (ATRA) to generate a cell population that resembles mature granulocytes. The differentiated HL-60 cell is capable of generating reactive oxygen species (ROS) when challenged with pyrogenic substances. In a luminol enhanced chemilumimetric assay the responsiveness of differentiated HL-60 cells is tested towards Salmonella typhimurium, Bacillus subtilis, Saccharomyces cerevisiae, Candida albicans, lipopolysaccharide (LPS) and lipoteichoic acid (LTA). The results show a poor sensitivity to S. typhimurium but displays good sensitivity towards B. subtilis, LTA and LPS. Furthermore, the sensitivity towards the yeasts C. albicans and S. cerevisiae is considerably better than obtained in other in vitro cell systems. Overall these results indicate that the HL-60 cell assay possibly could be evolved to a supplementary assay for the known pyrogenic detection assays. Furthermore, the utilization of the assay for pyrogenic examination of recombinant drugs derived from yeast expression systems would be relevant to examine.

Dry and moist heat sterilisation cannot inactivate pyrogenicity of Gram positive microorganisms

In the monocytic cell line Mono Mac 6 pyrogens induce interleukin-6 secretion dose dependently. The aim of this study is to examine the interleukin-6 inducing capacity of Gram positive Staphylococcus aureus and Bacillus subtilis endospores after moist and dry heat sterilisation. Moist heat sterilisation of B. subtilis endospores for 15 min at 121 degrees C and 134 degrees C can only reduce the interleukin-6 inducing capacity to 57% and 63%, respectively, compared to untreated. Moist heat sterilisation of S. aureus for 60 min at 121 degrees C and 134 degrees C does not reduce the interleukin-6 inducing capacity of S. aureus. On the contrary moist heat sterilisation at 134 degrees C for 10, 20 and 40 min significantly increases the interleukin-6 inducing capacity compared to untreated S. aureus. This is confirmed in the rabbit pyrogen test. Dry heat sterilisation of B. subtilis endospores at 220 degrees C for 45 min reduces the interleukin-6 inducing capacity to 2% compared to untreated endospores. Dry heat treatment of S. aureus at 220 degrees C for 30 min only reduces the activity to 55%. However, after 250 degrees C for 30 min or 220 degrees C for 6h there is no detectable activity of S. aureus. In conclusion, neither the interleukin-6 inducing activity nor the pyrogenicity of S. aureus and endospores of B. subtilis can be inactivated by the heat sterilisation procedures described by the European Pharmacopoeia.