The cell wall component lipoteichoic acid of Staphylococcus aureus induces chemokine gene expression in bovine mammary epithelial cells.

Staphylococcus aureus (SA) is a major cause of bovine mastitis, but its pathogenic mechanism remains poorly understood. To evaluate the role of lipoteichoic acid (LTA) in the immune or inflammatory response of SA mastitis, we investigated the gene expression profile in bovine mammary epithelial cells stimulated with LTA alone or with formalin-killed SA (FKSA) using cap analysis of gene expression. Seven common differentially expressed genes related to immune or inflammatory mediators were up-regulated under both LTA and FKSA stimulations. Three of these genes encode chemokines (IL-8, CXCL6 and CCL2) functioning as chemoattractant molecules for neutrophils and macrophages. These results suggest that the initial inflammatory response of SA infection in mammary gland may be related with LTA induced chemokine genes.

Antigen presenting cells targeting and stimulation potential of lipoteichoic acid functionalized lipo-polymerosome: a chemo-immunotherapeutic approach against intracellular infectious disease.

Antigen presenting cells (APC) are well-recognized therapeutic targets for intracellular infectious diseases, including visceral leishmaniasis. These targets have raised concerns regarding their potential for drug delivery due to overexpression of a variety of receptors for pathogen associated molecular pathways after infection. Since, lipoteichoic acid (LTA), a surface glycolipid of Gram-positive bacteria responsible for recognition of bacteria by APC receptors that also regulate their activation for pro-inflammatory cytokine secretion, provides additive and significant protection against parasite. Here, we report the nanoarchitechture of APC focused LTA functionalized amphotericin B encapsulated lipo-polymerosome (LTA-AmB-L-Psome) delivery system mediated by self-assembly of synthesized glycol chitosan-stearic acid copolymer (GC-SA) and cholesterol lipid, which can activate and target the chemotherapeutic agents to Leishmania parasite resident APC. Greater J774A and RAW264.7 macrophage internalization of FITC tagged LTA-AmB-L-Psome compared to core AmB-L-Psome was observed by FACSCalibur cytometer assessment. This was further confirmed by higher accumulation in macrophage rich liver, lung and spleen during biodistribution study. The LTA-AmB-L-Psome overcame encapsulated drug toxicity and significantly increased parasite growth inhibition beyond commercial AmB treatment in both in vitro (macrophage-amastigote system; IC50, 0.082 ± 0.009 µg/mL) and in vivo (Leishmania donovani infected hamsters; 89.25 ± 6.44% parasite inhibition) models. Moreover, LTA-AmB-L-Psome stimulated the production of protective cytokines like interferon-γ (IFN-γ), interleukin-12 (IL-12), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase and nitric oxide with down-regulation of disease susceptible cytokines, like transforming growth factor-ß (TGF-ß), IL-10, and IL-4. These data demonstrate the potential use of LTA-functionalized lipo-polymerosome as a biocompatible lucrative nanotherapeutic platform for overcoming toxicity and improving drug efficacy along with induction of robust APC immune responses for effective therapeutics of intracellular diseases.

Scavenger receptor-like receptors for the binding of lipopolysaccharide and lipoteichoic acid to liver endothelial and Kupffer cells.

This study was undertaken to identify the role of scavenger receptors in the catabolism of lipopolysaccharide (LPS) and lipoteichoic acid (LTA). LPS is mainly cleared from the blood by the liver. The Kupffer cells are primarily responsible for this clearance. Although several binding sites have been described for LPS and LTA, only CD14 is involved in LPS signalling. Scavenger receptor type A (SR-A) is expressed in the liver on endothelial cells and Kupffer cells, and macrosialin (class D scavenger receptor) is expressed on Kupffer cells. Fucoidin and poly-I are both good inhibitors of scavenger receptors. Fucoidin significantly reduced the serum clearance of [125I]-LPS and decreased liver uptake of [125I]-LPS by approximately 40%. Poly-I inhibited the binding of [125I]-LPS to isolated Kupffer and endothelial cells by 75%, while poly-A, a polyanionic substrate that does not block scavenger receptors, had no effect. LPS significantly inhibited the binding of acetylated LDL and oxidized LDL (two well-described scavenger receptor ligands) to isolated Kupffer and liver endothelial cells. OxLDL and acLDL did not affect the binding of LPS to these cells. We conclude that on both endothelial cells and Kupffer cells, LPS mainly binds to scavenger receptors, but SR-A and macrosialin contribute to a limited extent to the binding of LPS. Injection of LTA into C57Bl6 mice resulted in a maximal liver uptake of 20% of the injected dose. In the liver, 50% was bound by the Kupffer cells, 20% by parenchymal cells and 30% by liver endothelial cells. The contribution of SR-A to the plasma clearance of LTA was limited. A main component in the catabolism of LTA is the interaction of LTA with plasma lipoproteins, which limit the uptake of LTA by tissues and extend the plasma half-life of LTA.

The effect of Triton X-100 on the in-vitro susceptibility of methicillin-resistant Staphylococcus aureus to oxacillin.

The effect of the non-ionic detergent, Triton X-100, on the in-vitro activity of oxacillin against methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) strains of Staphylococcus aureus was investigated. In the presence of Triton X-100, the MICs of oxacillin for both MRSA and MSSA isolates were reduced; this enhancing effect was particularly marked for the MRSA strains. Triton X-100 therefore counteracted the resistance to methicillin encoded by mecA. In the presence of oxacillin at subinhibitory concentrations, Triton X-100 induced the bacteriolysis of MRSA and potentiated the autolysis of these organisms. However, the detergent had no effect on the bacteriolytic enzyme profile or the susceptibility of the bacterial cell wall to bacteriolytic enzymes, nor did it promote the binding of oxacillin to the penicillin-binding protein (PBP) 2A. On the other hand, it stimulated the release from the bacteria of acylated lipoteichoic acid (LTA), a putative endogenous regulator of autolysins. Autolytic enzyme-deficient MRSA mutants were equally as sensitive as the parent strain to the effect of Triton X-100 on susceptibility to oxacillin. These results indicate that the enhanced in-vitro activity of oxacillin against MRSA in the presence of Triton X-100 cannot be accounted for simply by the induction of bacteriolysis following activation of autolytic enzymes by the detergent-stimulated release of LTA.

Deposition of circulating streptococcal lipoteichoic acid in mouse tissues.

The tissue binding properties of streptococcal lipoteichoic acid (LTA) were studied using normal and passively immunized BALB/c mice. After intraperitoneal injection in non-immunized mice, 3H-LTA concentrations in blood, heart, kidney and liver were highest between 24 and 30 h post-injection. LTA deposits in heart remained high for the next 24 h, whereas other tissue levels decreased. Constant amounts of 3H-LTA were detected in urine throughout the 48 h period. In passively immunized mice, the amount of tissue deposition of 3H-LTA was inversely proportional to the ratio of antibodies to LTA. Autoradiography revealed focal deposits of 3H-LTA in heart, kidney and liver. These observations indicate that LTA, released by streptococci growing at remote body sites, can be carried by the blood to internal organs where it can accumulate and participate in pathogenesis.