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Cytolytic pore-forming protein, perforin, has been associated with autoimmune destruction of pancreatic β-cells in type 1 diabetes mellitus (T1DM) once released from CD8 + T cells. Curiously, perforinopathy has also been implicated in numerous brain diseases. Therefore, inhibitors of perforin have been in demand with targeted delivery in mind. l-Type amino acid transporter 1 (LAT1) is known to be expressed in both the above-mentioned target tissues, in the pancreas as well as in the brain. Thus, in the present study, the distribution of two LAT1-utilizing prodrugs of investigational perforin inhibitors into the pancreas was explored after intraperitoneal (i.p., 30 μmol/kg) bolus injection to mice. The effects of prodrug 1 were also studied in lipopolysaccharide (LPS)-induced in vitro (50 μg/mL) and in vivo (250 μg/kg x 3 days) apoptosis and pancreatitis models by determining the cellular apoptotic levels with human umbilical vein endothelial cells (HUVEC) and pancreatic caspase-3/-7 activity in mice. Furthermore, the biocompatibility of prodrug 1 was explored in human plasma and towards red blood cells. According to the results, both prodrugs were accumulated more effectively into the pancreas than their parent drugs (in addition to the brain that has been previously reported). Prodrug 1 (30 μmol/kg) also decreased the pancreatic caspase-3/-7 activity (52%) and with 2.5 μM concentration, the number of early and late apoptotic cells (32-53%). Since prodrug 1 was also found to be hemocompatible and not affecting human plasma hemostasis or inducing hemolysis of erythrocytes at the concentration <50 μM, it can be considered biocompatible in systemic circulation and ready to be studied in the future as a dual-acting drug candidate (in the pancreas and brain) in diseases like T1DM with neurodegenerative comorbidities., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In time, diagnosis and detection of virulence factor and its pathogenomics study continues to grow and this leads to novel treatments for infectious diseases. The objective of this study was to detect and characterise virulence genes in a haemolytic strain of Staphylococcus aureus in vitro and molecular interaction studies with herbal essential oil components in silico. A hospital biosample-isolated strain of Staphylococcus aureus (BMS-2) was resistant towards Cephalosporin. The PCR-amplified FASTA nucleotide sequence was identical with S. aureus strains absolutely. The calculated GC value was 34.05%. The translated protein sequence was identified with a conserved domain of hlyII β-channel forming cytolysin belonging to leukocidin superfamily and was predicted as a stable, non-transmembrane protein comprising B cell epitopes. Structurally, the protein was found to be composed of α helix, π-helix, extended strands, β-sheet, turn and bends with atomic composition as C 658 H 1026 N 174 O 200 S 2 . The molecular docking studies made between the HlyII cytolysin (receptor) and wet lab studied essential oil components (citral a, citronellol, eucalyptol, eugenol, geraniol, linalool, menthol, piperine and thymol) as ligands using Autodock 1.5.6 tool had inferred about prevalence of hydrogen bonds as well as covalent bonds in the intermolecular interactions. Amino acids like Tyr68, Tyr 69, Asn106, Asp67 and Asn106 were observed to be the most active residues for H-bond and hydrophobic bonds respectively. Only geraniol had interaction with glycine residue of the toxin molecule. In conclusion, geraniol with the highest ligand efficiency was observed to be the most potent phyto-constituent interacting with the in vitro detected hlyII cytotoxin.

The cytolytic protein perforin has a crucial role in infections and tumor surveillance. Recently, it has also been associated with many brain diseases, such as neurodegenerative diseases and stroke. Therefore, inhibitors of perforin have attracted interest as novel drug candidates. We have previously reported that converting a perforin inhibitor into an L-type amino acid transporter 1 (LAT1)-utilizing prodrug can improve the compound's brain drug delivery not only across the blood-brain barrier (BBB) but also into the brain parenchymal cells: neurons, astrocytes, and microglia. The present study evaluated whether the increased uptake into mouse primary cortical astrocytes and subsequently improvements in the cellular bioavailability of this brain-targeted perforin inhibitor prodrug could enhance its pharmacological effects, such as inhibition of production of caspase-3/-7, lipid peroxidation products and prostaglandin E 2 (PGE 2 ) in the lipopolysaccharide (LPS)-induced neuroinflammation mouse model. It was demonstrated that increased brain and cellular drug delivery could improve the ability of perforin inhibitors to elicit their pharmacological effects in the brain at nano- to picomolar levels. Furthermore, the prodrug displayed multifunctional properties since it also inhibited the activity of several key enzymes related to Alzheimer's disease (AD), such as the β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1), acetylcholinesterase (AChE), and most probably also cyclooxygenases (COX) at micromolar concentrations. Therefore, this prodrug is a potential drug candidate for preventing Aβ-accumulation and ACh-depletion in addition to combatting neuroinflammation, oxidative stress, and neural apoptosis within the brain. Graphical abstract.

Perforin is a key effector protein in the vertebrate immune system and is secreted by cytotoxic T lymphocytes and natural killer cells to help eliminate virus-infected and transformed target cells. The ability to modulate perforin activity in vivo could be extremely useful, especially in the context of bone marrow stem cell transplantation where early rejection of immunologically mismatched grafts is driven by the recipient's natural killer cells, which overwhelmingly use perforin to kill their targets. Bone marrow stem cell transplantation is a potentially curative treatment for both malignant and nonmalignant disorders, but when the body recognizes the graft as foreign, it is rejected by this process, often with fatal consequences. Here we report optimization of a previously identified series of benzenesulfonamide-based perforin inhibitors for their physicochemical and pharmacokinetic properties, resulting in the identification of 16 , the first reported small molecule able to prevent rejection of transplanted bone marrow stem cells in vivo by blocking perforin function.

Quantitative structure-activity relationship (QSAR) studies were performed on a series of 5-arylidene-2thioxoimidazolidin-4-ones derivatives as the inhibitors of perforin and to gain insights about the structural determinants for designing new drug molecules. The heuristic method could explore the descriptors responsible for bioactivity and gain a best linear model with R 2 .82. Gene expression programming method generated a novel nonlinear function model with R 2 .92 for training set and R 2 .85 for test set. The predicted IC 50 by QSAR, molecular docking analysis, and property explorer applet show that 42a acts as a well-pleasing potent inhibitor for perforin. This study may lay a reliable theoretical foundation for the development of designing perforin inhibitor structures., (© 2017 John Wiley & Sons A/S.)

The structure-activity relationships for a series of arylsulphonamide-based inhibitors of the pore-forming protein perforin have been explored. Perforin is a key component of the human immune response, however inappropriate activity has also been implicated in certain auto-immune and therapy-induced conditions such as allograft rejection and graft versus host disease. Since perforin is expressed exclusively by cells of the immune system, inhibition of this protein would be a highly selective strategy for the immunosuppressive treatment of these disorders. Compounds from this series were demonstrated to be potent inhibitors of the lytic action of both isolated recombinant perforin and perforin secreted by natural killer cells in vitro. Several potent and soluble examples were assessed for in vivo pharmacokinetic properties and found to be suitable for progression to an in vivo model of transplant rejection., (Copyright © 2017 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

The pore-forming protein perforin is a key component of mammalian cell-mediated immunity and essential to the pathway that allows elimination of virus-infected and transformed cells. Perforin activity has also been implicated in certain auto-immune conditions and therapy-induced conditions such as allograft rejection and graft versus host disease. An inhibitor of perforin activity could be used as a highly specific immunosuppressive treatment for these conditions, with reduced side-effects compared to currently accepted therapies. Previously identified first-in-class inhibitors based on a 2-thioxoimidazolidin-4-one core show suboptimal physicochemical properties and toxicity toward the natural killer (NK) cells that secrete perforin in vivo. The current benzenesulphonamide-based series delivers a non-toxic bioisosteric replacement possessing improved solubility., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

We have recently reported that by converting a perforin inhibitor into an l-type amino acid transporter 1 (LAT1)-utilizing prodrug its cellular uptake can be greatly increased. The aim of the present study was to determine the in vivo and brain pharmacokinetics of two perforin inhibitors and their LAT1-utilizing prodrugs 1 and 2. In addition, the brain uptake mechanism and entry into primary mouse cortical neurons and astrocytes were evaluated. After 23 μmol/kg i.p. bolus injection, the prodrugs' unbound area under the concentration curve in brain was 0.3 nmol/g × min, whereas the parent drugs could not reach the brain. The unbound brain concentrations of the prodrugs after 100 μM in situ mouse brain perfusion were 521.4 ± 46.9 and 126.9 ± 19.9 pmol/g for prodrugs 1 and 2, respectively. The combination of competing transporter substrates for LAT1, l-tryptophan, and for organic anion transporting polypeptides, probenecid, decreased the brain concentrations to 352.4 ± 44.5 and 70.9 ± 7.0 pmol/g, respectively. In addition, in vitro uptake studies showed that at 100 μM prodrug 1 had 3.4-fold and 4.5-fold higher uptake rate into neurons and astrocytes, respectively, compared to its parent drug. Thus, the prodrugs enhance significantly the therapeutic potential of the parent drugs for the treatment of disorders of central nervous system in which neuroinflammation is involved.

Perforin is a cytolytic pore-forming glycoprotein secreted by cytotoxic effector cells. It is a key component of the immune response against virus-infected and transformed cells and has been implicated in a number of human diseases. Perforin activity can be inhibited by small-molecular-weight compounds, although less is known about their delivery to the site of action. Therefore, in the present study, it was explored if perforin inhibitors could be efficiently and site-selectively delivered firstly into the cytotoxic effector cells and secondly into lytic granules, in which perforin is stored. This was accomplished by designing and synthesizing four prodrugs of perforin inhibitors that could utilize l-type amino acid transporter (LAT1), since activated immune cells are known to over-express LAT1. The results demonstrate that cellular uptake of perforin inhibitors can be increased by LAT1-utilizing prodrugs (into human breast adenocarcinoma cells (MCF-7)). Furthermore, these prodrugs were also able to deliver perforin inhibitors into the cell organelles having lower pH (rat liver lysosomes). Therefore, by using these prodrugs, intracellular mechanisms of perforin inhibitory activity can be studied more thoroughly in future. Moreover, this prodrug approach can be applied for other drugs that would benefit from targeted delivery into cells expressing LAT1, such as cancer., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Evolution from a furan-containing high-throughput screen (HTS) hit (1) resulted in isobenzofuran-1(3H)-one (2) as a potent inhibitor of the function of both isolated perforin protein and perforin delivered in situ by intact KHYG-1 NK cells. In the current study, structure-activity relationship (SAR) development towards a novel series of diarylthiophene analogues has continued through the use of substituted-benzene and -pyridyl moieties as bioisosteres for 2-thioxoimidazolidin-4-one (A) on a thiophene (B) -isobenzofuranone (C) scaffold. The resulting compounds were tested for their ability to inhibit perforin lytic activity in vitro. Carboxamide (23) shows a 4-fold increase over (2) in lytic activity against isolated perforin and provides good rationale for continued development within this class., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The cytolytic protein perforin is a key component of the immune response and is implicated in a number of human pathologies and therapy-induced conditions. A novel series of small molecule inhibitors of perforin function have been developed as potential immunosuppressive agents. The pharmacokinetics and metabolic stability of a series of 16 inhibitors of perforin was evaluated in male CD1 mice following intravenous administration. The compounds were well tolerated 6 h after dosing. After intravenous administration at 5 mg/kg, maximum plasma concentrations ranged from 532 ± 200 to 10,061 ± 12 ng/mL across the series. Plasma concentrations were greater than the concentrations required for in vitro inhibitory activity for 11 of the compounds. Following an initial rapid distribution phase, the elimination half-life values for the series ranged from 0.82 ± 0.25 to 4.38 ± 4.48 h. All compounds in the series were susceptible to oxidative biotransformation. Following incubations with microsomal preparations, a tenfold range in in vitro half-life was observed across the series. The data suggests that oxidative biotransformation was not singularly responsible for clearance of the compounds and no direct relationship between microsomal clearance and plasma clearance was observed. Structural modifications however, do provide some information as to the relative microsomal stability of the compounds, which may be useful for further drug development.

A series of novel 5-arylidene-2-thioxoimidazolidin-4-ones were investigated as inhibitors of the lymphocyte-expressed pore-forming protein perforin. Structure-activity relationships were explored through variation of an isoindolinone or 3,4-dihydroisoquinolinone subunit on a fixed 2-thioxoimidazolidin-4-one/thiophene core. The ability of the resulting compounds to inhibit the lytic activity of both isolated perforin protein and perforin delivered in situ by natural killer cells was determined. A number of compounds showed excellent activity at concentrations that were nontoxic to the killer cells, and several were a significant improvement on previous classes of inhibitors, being substantially more potent and soluble. Representative examples showed rapid and reversible binding to immobilized mouse perforin at low concentrations (≤2.5 μM) by surface plasmon resonance and prevented formation of perforin pores in target cells despite effective target cell engagement, as determined by calcium influx studies. Mouse PK studies of two analogues showed T1/2 values of 1.1-1.2 h (dose of 5 mg/kg i.v.) and MTDs of 60-80 mg/kg (i.p.).

An aryl-substituted isobenzofuran-1(3H)-one lead compound was identified from a high throughput screen designed to find inhibitors of the lymphocyte pore-forming protein perforin. A series of analogs were then designed and prepared, exploring structure-activity relationships through variation of 2-thioxoimidazolidin-4-one and furan subunits on an isobenzofuranone core. The ability of the resulting compounds to inhibit the lytic activity of both isolated perforin protein and perforin delivered in situ by intact KHYG-1 natural killer effector cells was determined. Several compounds showed excellent activity at concentrations that were non-toxic to the killer cells. This series represents a significant improvement on previous classes of compounds, being substantially more potent and largely retaining activity in the presence of serum., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Modulation of CD4(+)CD28null T cells through K+ channels could provide potential novel targets for the treatment acute coronary syndrome (ACS). However, the surface phenotype and K+ channel expression of CD4(+)CD28null T cells in patients with ACS is unclear. The aim of this study was to investigate the surface phenotype and K+ channel expression of CD4(+)CD28null T cells in patients with ACS. We found that more than 80% of CD4(+)CD28null T cells in patients with ACS showed a CD45RA(-)CD45RO(+)CCR7- surface phenotype. CD4(+)CD28(null) T expressed small numbers of the voltage-gated Kv1.3 and intermediate-conductance Ca2+-activated K+ channel KCa3.1 when quiescent, but increased Kv1.3 expression 4-fold with little change in KCa3.1 levels upon activation. Consistent with their channel phenotypes, the production of interferon-γ and perforin in CD4(+)CD28null T cells was suppressed by the specific Kv1.3 blocker 5-(4-phenoxybutoxy)psoralen PAP-1. Therefore, selective targeting of Kv1.3 in CD4(+)CD28null T cells may hold potential therapeutic promise for ACS., (Copyright © 2011 Elsevier Inc. All rights reserved.)

We aimed to analyse granulysin (GNLY)-mediated cytotoxicity in the peripheral blood of patients with non-ST-segment elevation myocardial infarction (NSTEMI) treated with anti-ischaemic drug therapy. Thirty-nine NSTEMI patients with a median age of 70 years and 28 age-matched healthy subjects were enrolled in this study. On day 7 after MI, the number of GNLY(+) lymphocytes in the peripheral blood increased approximately six-fold of that in the healthy subjects, measured by flow cytometry. On day 14, the number of GNLY(+) cells significantly decreased in T, NKT, and both CD56(+dim) and CD56(+bright) NK subsets. GNLY(+) CD3(+) and GNLY(+) CD56(+) cells infiltrated central zone of myocardial infarction (MI). In persons who died in the first week after MI, GNLY(+) cells were found within accumulation of apoptotic leucocytes and reached the apoptotic cardiomyocytes in border MI zones probably due to the influence of interleukin-15 in peri-necrotic cardiomyocytes, as it is was shown by immunohistology. By day 28, the percentage of GNLY(+) lymphocytes in peripheral blood returned to the levels similar to that of the healthy subjects. Anti-GNLY mAb decreased apoptosis of K562 targets using peripheral blood NK cells from days 7 and 28 after MI, while in assays using cells from days 1 and 21, both anti-GNLY and anti-perforin mAbs were required to significantly decrease apoptosis. Using NK cells from day 14, K562 apoptosis was nearly absent. In conclusion, it seems that GNLY(+) lymphocytes, probably attracted by IL-15, not only participate partially in myocardial cell apoptosis, but also hasten resolution of cardiac leucocyte infiltration in patients with NSTEMI., (© 2011 The Authors. Scandinavian Journal of Immunology © 2011 Blackwell Publishing Ltd.)

A high throughput screen showed the ability of a 1-amino-2,4-dicyanopyrido[1,2-a]benzimidazole analogue to directly inhibit the lytic activity of the pore-forming protein perforin. A series of analogues were prepared to study structure-activity relationships (SAR) for the this activity, either directly added to cells or released in situ by KHYG-1 NK cells, at non-toxic concentrations. These studies showed that the pyridobenzimidazole moiety was required for effective activity, with strongly basic centres disfavoured. This class of compounds was relatively unaffected by the addition of serum, which was not the case for a previous class of direct inhibitors., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Background: Cytolysins are pore-forming toxins that show anticancer activity by a mechanism hitherto poorly investigated., Materials and Methods: To investigate how cytolysins are cytotoxic to resistant cancer cells, proliferation and cell death were evaluated on U87 glioblastoma cells treated with toxin Bc2 or equinatoxin-II (EqTx-II)., Results: Toxins Bc2 and EqTx-II decreased cell viability and increased lactate dehydrogenase (LDH) release in a concentration-dependent manner. Swollen, dead or dying cells were negative for TUNEL staining. The pre-treatment with inhibitors of mitogen-activated/extracellular regulated kinase (MEK1), protein kinase C (PKC) or Ca(2+)/calmodulin-dependent kinase II (CaMKII) blocked the toxic effects of toxin Bc2 and EqTx-II, suggesting that calcium entry, activation of MEK1, PKC and CaMKII pathways are involved in the cytotoxicity induced by these cytolysins., Conclusion: Cytolysins were shown to be toxic to glioblastoma cells by activating several intracellular signaling pathways and resulting in necrosis-like cell death.

Background: There is mounting evidence that perforin and granzymes are important mediators in the lung destruction seen in COPD. We investigated the characteristics of the three main perforin and granzyme containing peripheral cells, namely CD8+ T lymphocytes, natural killer (NK; CD56+CD3-) cells and NKT-like (CD56+CD3+) cells., Methods: Peripheral blood mononuclear cells (PBMCs) were isolated and cell numbers and intracellular granzyme B and perforin were analysed by flow cytometry. Immunomagnetically selected CD8+ T lymphocytes, NK (CD56+CD3-) and NKT-like (CD56+CD3+) cells were used in an LDH release assay to determine cytotoxicity and cytotoxic mechanisms were investigated by blocking perforin and granzyme B with relevant antibodies., Results: The proportion of peripheral blood NKT-like (CD56+CD3+) cells in smokers with COPD (COPD subjects) was significantly lower (0.6%) than in healthy smokers (smokers) (2.8%, p < 0.001) and non-smoking healthy participants (HNS) (3.3%, p < 0.001). NK (CD56+CD3-) cells from COPD subjects were significantly less cytotoxic than in smokers (16.8% vs 51.9% specific lysis, p < 0.001) as were NKT-like (CD56+CD3+) cells (16.7% vs 52.4% specific lysis, p < 0.001). Both cell types had lower proportions expressing both perforin and granzyme B. Blocking the action of perforin and granzyme B reduced the cytotoxic activity of NK (CD56+CD3-) and NKT-like (CD56+CD3+) cells from smokers and HNS., Conclusion: In this study, we show that the relative numbers of peripheral blood NK (CD56+CD3-) and NKT-like (CD56+CD3+) cells in COPD subjects are reduced and that their cytotoxic effector function is defective.

Lysophosphatidic acid (LPA) is an activator and chemoattractant of NK cells, which are critical members of the immunological tumor surveillance machinery. Here, we analyzed the influence of LPA on the interaction of human NK cells with tumor cells such as the Burkitt lymphoma cell line Raji and the human melanoma cell line A2058. Thereby we found that LPA inhibits the release of perforin and cytotoxic activity of NK cells. Analysis of signal transduction showed that LPA induces common signaling pathways of chemotaxins such as G(i) protein-dependent actin re-organization, activation of the mitogen-activated protein kinase p38 as well as phosphatidylinositol-3-kinase-dependent signal molecules [protein kinase B/Akt and glycogen synthase kinase-3beta (GSK-3beta)]. In contrast to most chemotaxins, LPA is also able to activate G(s)-dependent signaling molecules. This signaling cascade involves the LPA receptor type-2, increase cAMP levels and protein kinase A (PKA) activation, which in turn are responsible for the modulatory effect of LPA on NK cell-mediated cytotoxicity. Moreover, blocking the regulatory subunits of PKA I abrogates the inhibitory effect of LPA, whereas the catalytic subunits are not involved. Based on our data, one can assume that LPA contributes to the tumor escape from the immunological surveillance machinery.

The maturation of naive CD8(+) T cells into effector CTLs is a critical feature of a functional adaptive immune system. Development of CTLs depends, in part, upon the expression of the transcriptional regulator eomesodermin (EOMES), which is thought to regulate expression of two key effector molecules, perforin and granzyme B. Although EOMES is important for effector CTL development, the precise mechanisms regulating CD8(+) effector cell maturation remains poorly understood. In this study, we show that Notch1 regulates the expression of EOMES, perforin, and granzyme B through direct binding to the promoters of these crucial effector molecules. By abrogating Notch signaling, both biochemically as well as genetically, we conclude that Notch activity mediates CTL activity through direct regulation of EOMES, perforin, and granzyme B.

Perforin, a membrane-permeabilizing protein, is important to T cell cytotoxic action. Perforin has potential to damage the T cell in the endoplasmic reticulum (ER), is sequestered in granules, and later is exocytosed to kill cells. In the ER and after exocytosis, calcium and pH favor perforin activity. We found a novel perforin inhibitor associated with cytotoxic T cell granules and termed it Cytotoxic Regulatory Protein 2 (CxRP2). CxRP2 blocked lysis by granule extracts, recombinant perforin and T cells. Its effects lasted for hours. CxRP2 was calcium stable and refractory to inhibitors of granzyme and cathepsin proteases. Through mass spectrometric analysis of active 50-100 kDa proteins, we identified CxRP2 candidates. Protein disulfide isomerase A3 was the strongest candidate but was unavailable for testing; however, protein disulfide isomerase A1 had CxRP2 activity. Our results indicate that protein disulfide isomerases, in the ER or elsewhere, may protect T cells from their own perforin.

Dihydrofuro[3,4-c]pyridinones are the first class of small molecules reported to inhibit the cytolytic effects of the lymphocyte toxin perforin. A lead structure was identified from a high throughput screen, and a series of analogues were designed and prepared to explore structure-activity relationships around the core bicyclic thioxofuropyridinone and pendant furan ring. This resulted in the identification of a submicromolar inhibitor of the perforin-induced lysis of Jurkat T-lymphoma cells.

We previously identified a subpopulation of monocyte/macrophage lineage cells expressing both CD4 and CD8. This subpopulation was expanded in rat peripheral blood and spleen after immunization with adjuvants containing killed tuberculosis germs. CD4+CD8+ monocytes/macrophages obtained from preimmunized rats exhibited a Th1-type cytokine/chemokine profile, expressed high levels of Fas ligand, perforin, granzyme B, and NKR-P2 (rat ortholog of human NKG2D), and killed certain tumor cells. In the present study, we confirmed that CD4+CD8+ monocytes/macrophages are distinct from splenic dendritic cells (DCs) or IFN-producing killer DCs. In vitro cytotoxic assays revealed that CD4+CD8+ macrophages killed tumor cells in a cell-cell contact-dependent manner and that expression of the retinoic acid early transcript 1 (a ligand for NKG2D) made tumor cells susceptible to killing by CD4+CD8+ macrophages. Furthermore, inhibitors of granzyme and perforin significantly decreased cytotoxic activities of CD4+CD8+ macrophages. Consistent with these in vitro findings, preimmunization with adjuvants containing killed tuberculosis germs elevated the expression of granzyme B in tumor-infiltrating CD4+CD8+ macrophages and significantly inhibited the growth of inoculated tumor cells. Our current work demonstrates that CD4+CD8+ macrophages are a unique subpopulation of monocyte/macrophage lineage cells that kill tumor cells in an NKG2D- and granzyme/perforin-dependent mechanism.

Lipoprotein plays a role in the host defense against bacterial infection, and its serum level has been demonstrated to be an important prognosis factor of survival. We have previously demonstrated that LDL directly inactivates the hemolytic activity of Vibrio vulnificus cytolysin (VVC) in vitro. The object of this study was therefore to examine whether the LDL-mediated inactivation of VVC leads to protection against lethal infection of V. vulnificus in vivo, using wild and VVC-deficient V. vulnificus strains. Unexpectedly, we found that LDL protects mouse lethality induced by VVC-deficient as well as wild V. vulnificus strain. We also demonstrated that LDL blocks V. vulnificus LPS-induced lethality in mice. These results suggest that LDL preferentially act on endotoxin rather than exotoxin in the protection against V. vulnificus-induced mice lethality.