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P J Lachmann

Publications and source records attributed to P J Lachmann.

At least 19 recordsLinked to original sources
PubMed2006

Inhibition of antimicrobial peptides by group A streptococci: SIC and DRS.

SIC (streptococcal inhibitor of complement) is a 31 kDa protein secreted by a few highly virulent strains of GAS (group A streptococci), predominantly by the M1 strain. Initially described as an inhibitor of the membrane attack complex of complement, it has turned out to be a polyfunctional inhibitor of the innate mucosal immune response. The SIC protein sequence contains three domains: an N-terminal SRR (short repeat region), followed by three longer tandem repeats [LRR (long repeat region)] and a C-terminal PRR (proline-rich region). SIC inhibits the antibacterial activity of a wide range of antimicrobial peptides and proteins: i.e. lysozyme, SLPI (secretory leucocyte proteinase inhibitor), LL-37, hNP-1 (human neutrophil peptide-1) and the human beta-defensins 1, 2 and 3. Analysis of the functional properties of recombinant domains of SIC shows that binding and inhibition of lysozyme and human beta-defensin-3 require the SRR+LRR, as does binding to SLPI. Complement inhibition is confined to the SRR. M12 GAS secrete a protein 'distantly related to SIC' (DRS). DRS contains a C-terminal PRR which is significantly similar to that of SIC, but it has no central LRR and the N-terminal SRR is very different. DRS inhibits human beta-defensin-3, but has no effect on lysozyme, SLPI or complement.

Animals↗
PubMed2004

Antimicrobial peptides: mediators of innate immunity as templates for the development of novel anti-infective and immune therapeutics.

Antimicrobial molecules are ancient and essential small cationic molecules of the host defence system which are found in a wide variety of species. They display antimicrobial activity against a wide range of bacteria, fungi and viruses, an activity that has been mostly attributed to the disruption of microbial membranes. In this article, we will review the "classical" functions of 3 classes of antimicrobial molecules, namely defensins, cathelicidins, and the four-disulfide core proteins secretory leukocyte proteinase inhibitor (SLPI) and elafin. In addition to the study of their expression in a variety of cell types and the regulation of their production, we will also describe novel properties of these molecules that have been highlighted by recent studies. These include their ability to chemoattract a variety of inflammatory, immune and other cell types (neutrophils, macrophages, monocytes, lymphocytes, mast cells, epithelial cells) in vitro and in vivo. In addition, we will discuss the potential use of these newly discovered properties for therapeutic or vaccination purposes, using protein- or gene-transfer based methodologies. Finally, we will examine in an extensive fashion the strategies used by microorganisms to circumvent and subvert host defence mechanisms, such as the modifications of cell membranes and walls, the secretion of inactivating proteins and proteases and the down-regulation of expression of antimicrobial molecules. Increased understanding of the mechanisms used by both the host and the microbes to 'win the battle' may ultimately lead to new therapeutic strategies aimed to treat infectious diseases.

Amino Acid Sequence↗
PubMed2003

Determination of CD59 protein in normal human serum by enzyme immunoassay, using octyl-glucoside detergent to release glycosyl-phosphatidylinositol-CD59 from lipid complex.

In this study we have optimised the enzyme immunoassay (ELISA) to quantify CD59 antigen in human serum or plasma. The glycosyl-phosphatidylinositol (GPI)-linked form of CD59 is known to complex with serum high-density lipoprotein. For ELISA optimisation, therefore, we investigated the effect of detergents, added to the sample diluent, on the determined values of CD59. Values obtained in the presence of octyl-glucoside (OG) for 20 adults aged 18-35 years and 17 children 1-5 years old were, respectively, 33-119 ng/ml (mean +/- S.D.: 66+/-22 ng/ml) and 37-143 ng/ml (76+/-33 ng/ml). These results were higher than those measured without OG and were in contrast with published results showing absence, or eight to nine times lower levels, of the protein in serum. A known range for serum concentrations of CD59 in healthy individuals will establish an important reference point for clinical work and for the investigation of diseases involving the complement membrane attack complex (MAC) and its regulation.

Adolescent↗
PubMed2003

Lupus and desoxyribonuclease.

The dominant autoantigen in SLE is the nucleosome and immune complexes involving nucleosomes are the major cause of tissue damage. Nucleosomes can be broken down in vivo with Desoxyribonuclease 1. DNase 1 from humans and mice is inhibited by actin and it is proposed that the release of platelet actin at inflammatory sites is one mechanism which causes nucleosomes to become antigenic. Rats whose DNase 1 is not inhibited by actin do not get lupus. Treatment of NZB/W mice with recombinant DNase slows the onset of their disease if given early and improves the renal disease if given later. This disease can also be entirely prevented by treatment with dexamethasone. Mice whose DNase 1 gene is knocked out are known to develop lupus and to be otherwise normal. DNase 1 especially in its mutant actin and salt resistant forms remains an attractive candidate for the treatment of SLE.

Deoxyribonucleases↗
PubMed2002

The risk to the United Kingdom population of zinc cadmium sulfide dispersion by the Ministry of Defence during the "cold war".

OBJECTIVES: To estimate exposures to cadmium (Cd) received by the United Kingdom population as a result of the dispersion of zinc Cd sulfide (ZnCdS) by the Ministry of Defence between 1953 and 1964, as a simulator of biological warfare agents. METHODS: A retrospective risk assessment study was carried out on the United Kingdom population during the period 1953-64. This determined land and air dispersion of ZnCdS over most of the United Kingdom, inhalation exposure of the United Kingdom population, soil contamination, and risks to personnel operating equipment that dispersed ZnCdS. RESULTS: About 4600 kg ZnCdS were dispersed from aircraft and ships, at times when the prevailing winds would allow large areas of the country to be covered. Cadmium released from 44 long range trials for which data are available, and extrapolated to a total of 76 trials to allow for trials with incomplete information, is about 1.2% of the estimated total release of Cd into the atmosphere over the same period. "Worst case" estimates are 10 microg Cd inhaled over 8 years, equivalent to Cd inhaled in an urban environment in 12100 days, or from smoking 100 cigarettes. A further 250 kg ZnCdS was dispersed from the land based sites, but significant soil contamination occurred only in limited areas, which were and have remained uninhabited. Of the four personnel involved in the dispersion procedures (who were probably exposed to much higher concentrations of Cd than people on the ground), none are suspected of having related illnesses. CONCLUSION: Exposure to Cd from dissemination of ZnCdS during the "cold war" should not have resulted in adverse health effects in the United Kingdom population.

Air Pollution↗
PubMed2001

Antibodies raised to short synthetic peptides with sequences derived from HIV-1 SF2 gp120 can both neutralize and enhance HIV-1 SF13: a later variant isolated from the same host.

HIV-1 SF13 emerged in a patient with immunity to HIV-1 SF2. This study determined the effect of antibodies raised to HIV-1 SF2 on the replication of the later variant. Antisera in rats were raised previously to a complete set of overlapping, synthetic 15mer peptides following the sequence of HIV-1 SF2 gp120. These sera have now been used in neutralization and enhancement assays against viruses derived from molecular clones of both variants. The sets of peptides inducing neutralizing antibodies to the two variants overlap. Antibodies to the third variable region of HIV-1 SF2 only neutralize the homologous virus whereas those to the second and fourth variable regions neutralize both variants. In contrast, the sets of major epitopes involved in enhancement do not overlap. Epitopes for both variants form two clusters when superimposed on the conformation of the conserved regions. To determine if antibodies with the potential to enhance or neutralize HIV-1 SF2 change over time in infected individuals sera from chimpanzees were used because no material was still available from the original patient. Antibodies to HIV-1 SF2 neutralizing epitopes and HIV-1 SF13 enhancing epitopes were present in the circulation of chimpanzees infected with HIV-1 SF2. Once antibodies to the neutralizing epitopes were induced they persisted whereas antibodies to the enhancing epitopes varied with time after infection. Conditions may therefore exist within individual hosts where not only neutralizing but also enhancing antibodies have the potential to contribute to the selection pressure operating on the circulating population of polymorphic variants.

Animals↗
PubMed2001

Streptococcal inhibitor of complement (SIC) inhibits the membrane attack complex by preventing uptake of C567 onto cell membranes.

Streptococcal inhibitor of complement (SIC) was first described in 1996 as a putative inhibitor of the membrane attack complex of complement (MAC). SIC is a 31 000 MW protein secreted in large quantities by the virulent Streptococcus pyogenes strains M1 and M57, and is encoded by a gene which is extremely variable. In order to study further the interactions of SIC with the MAC, we have made a recombinant form of SIC (rSIC) in Escherichia coli and purified native M1 SIC which was used to raise a polyclonal antibody. SIC prevented reactive lysis of guinea pig erythrocytes by the MAC at a stage prior to C5b67 complexes binding to cell membranes, presumably by blocking the transiently expressed membrane insertion site on C7. The ability of SIC and clusterin (another putative fluid phase complement inhibitor) to inhibit complement lysis was compared, and found to be equally efficient. In parallel, by enzyme-linked immunosorbent assay both SIC and rSIC bound strongly to C5b67 and C5b678 complexes and to a lesser extent C5b-9, but only weakly to individual complement components. The implications of these data for virulence of SIC-positive streptococci are discussed, in light of the fact that Gram-positive organisms are already protected against complement lysis by the presence of their peptidoglycan cell walls. We speculate that MAC inhibition may not be the sole function of SIC.

Bacterial Proteins↗
PubMed2001

Interaction between host complement and mosquito-midgut-stage Plasmodium berghei.

After ingestion by mosquitoes, gametocytes of malaria parasites become activated and form extracellular gametes that are no longer protected by the red blood cell membrane against immune effectors of host blood. We have studied the action of complement on Plasmodium developmental stages in the mosquito blood meal using the rodent malaria parasite Plasmodium berghei and rat complement as a model. We have shown that in the mosquito midgut, rat complement components necessary to initiate the alternative pathway (factor B, factor D, and C3) as well as C5 are present for several hours following ingestion of P. berghei-infected rat blood. In culture, 30 to 50% of mosquito midgut stages of P. berghei survived complement exposure during the first 3 h of development. Subsequently, parasites became increasingly sensitive to complement lysis. To investigate the mechanisms involved in their protection, we tested for C3 deposition on parasite surfaces and whether host CD59 (a potent inhibitor of the complement membrane attack complex present on red blood cells) was taken up by gametes while emerging from the host cell. Between 0.5 and 22 h, 90% of Pbs21-positive parasites were positive for C3. While rat red and white blood cells stained positive for CD59, Pbs21-positive parasites were negative for CD59. In addition, exposure of parasites to rat complement in the presence of anti-rat CD59 antibodies did not increase lysis. These data suggest that parasite or host molecules other than CD59 are responsible for the protection of malaria parasites against complement-mediated lysis. Ongoing research aims to identify these molecules.

Animals↗
PubMed2000

Neutrophil lactoferrin release induced by IgA immune complexes differed from that induced by cross-linking of fcalpha receptors (FcalphaR) with a monoclonal antibody, MIP8a.

The human IgA Fc receptor (FcalphaR, CD89) plays an important role in host defence against invading pathogens. To study the properties of the receptor, 12 MoAbs, namely, MIP7c, MIP8a, MIP9a, MIP10c, MIP11c, MIP14b, MIP15b, MIP38c, MIP59c, MIP65c, MIP68b and MIP71a, were generated. The inhibitory effects of the antibodies on FcalphaR functions were tested. Three of the antibodies, MIP7c, MIP8a and MIP59c, were able to block up to 90% of soluble FcalphaR binding to IgA-coated beads and 70-80% of neutrophil phagocytosis of IgA immune complexes (IC). MIP8a could also inhibit IgA IC-induced neutrophil lactoferrin release, while cross-linking of FcalphaR with MIP8a and anti-mouse IgG could elicit neutrophil lactoferrin release. However, IgA IC-induced lactoferrin release required both extracellular calcium and magnesium, whereas MIP8a-induced release did not require extracellular magnesium and only partially required extracellular calcium. In addition, the time course of IgA IC-induced lactoferrin release was slow. Lactoferrin was not detectable if the incubation time was less than 0.5 h. In contrast, MIP8a-induced lactoferrin release was fast. Lactoferrin could be detected within 5 min of incubation. Therefore, neutrophil lactoferrin release induced by IgA IC differed from that induced by cross-linking of FcalphaR with MIP8a.

Animals↗
PubMed1999

Comparison of C1q-receptors on rat microglia and peritoneal macrophages.

A comparison of the expression and ligand specificity of the C1q (first complement component) receptor on rat microglia and peritoneal macrophages was made. This revealed that radiolabelled C1q was competed from the peritoneal macrophages with intact C1q, and additively displaced by calf-skin collagen and purified C1q globular heads, suggesting the presence of at least two receptors. This was in contrast to microglia, where radiolabelled C1q was displaced with intact C1q and to a modest degree with collagen, but not with globular heads. Taken together, this implies that under these conditions, peritoneal macrophages and microglia both express a C1q receptor which binds to the collagen-like region, and that peritoneal macrophages additionally express a molecule which binds to the globular head of C1q. Analysis of the ligand bound by these cells reflected the differences observed in the competitive binding experiments, with the novel identification of naturally-occurring peptides from the globular head of C1q bound to the peritoneal macrophages, but not the microglia.

Amino Acid Sequence↗
PubMed1999

Anti-DNA antibodies in the urine of lupus nephritis patients.

BACKGROUND: It has previously been reported that patients with systemic lupus erythematosus (SLE) and glomerulonephritis do not have anti- (deoxyribonucleic acid) DNA antibodies in their urine. This finding was attributed to specific entrapment of anti-DNA antibodies by the immune complexes in the glomerular capillary walls. METHODS: This phenomenon has been re-investigated as part of a study of the use of desoxyribonuclease 1 (DNase 1) to treat lupus nephritis (LN). For this purpose an ELISA was developed for the detection of anti-DNA antibodies in urine. It was found that such an assay was very susceptible to the presence of DNase in urine which destroys the antigen coating the plates and gives rise to false negative results. For this reason, it is essential that all tests for anti-DNA antibodies in the urine are carried out in the presence of EDTA to inhibit the endogenous DNase 1 activity. RESULTS: Using this assay to test the urine from 24 patients with LN and non-selective proteinurea, it was found that they all contained anti-DNA antibodies. The amount of anti-DNA antibodies detected in the urine was compared with that expected by calculations from the anti-DNA antibody titre in the serum and total immunoglobulin levels in serum and in urine. It showed that in 20 patients there was neither specific entrapment nor specific excretion of anti-DNA in urine, only the expected amount of leakage. In only three patients was any appreciable entrapment demonstrated and in only one, any excess excretion. CONCLUSIONS: It is suggested that the failure to detect anti-DNA antibodies in the urine in the previous work was due to failure to inhibit the endogenous urinary DNase. It remains to be determined whether the retention of anti-DNA antibodies or excessive secretion is correlated with clinical phases of LN.

Antibodies, Antinuclear↗
PubMed1998

Neuronal protection of oligodendrocytes from antibody-independent complement lysis.

Cultured rat oligodendrocytes are lysed by complement via antibody-independent activation of the classical pathway. This susceptibility to complement lysis has been demonstrated to be due to lack of CD59, a complement regulatory protein which inhibits assembly of the membrane attack complex. In this study the effects of homologous and heterologous complement were examined in a co-culture system of rat oligodendrocytes and peripheral neurones, where axonal ensheathment was observed as early as 4 days after the addition of glial progenitors to the neurones. Following exposure to complement, ensheathing oligodendrocytes were markedly less sensitive to antibody-independent but not antibody-dependent complement lysis than were cells grown without neurones. Immunocytochemical data revealed that co-cultured oligodendrocytes remained CD59 negative, but in contrast to oligodendrocytes cultured alone, were negative for C3b when incubated with C7-deficient serum. Taken together these data indicate that the decreased sensitivity of co-cultured oligodendrocytes to complement lysis is not attributed to the increased expression of CD59, but rather in a failure to activate complement. Incubation of oligodendrocytes with neurone-conditioned medium afforded significant protection (68%), against antibody-independent complement attack, suggesting that soluble neuronal factors can protect oligodendrocytes from complement-mediated lysis.

Animals↗
PubMed1998

Microbial immunology: a new mechanism for immune subversion.

The number of mechanisms that have evolved in microbes to subvert the immune response seems limitless. Tubercle bacilli have found a novel way to coat themselves with the C3 complement protein and invade macrophages by interactions with complement receptors.

Bacterial Proteins↗
PubMed1998

Public health and bioethics.

Conduct that satisfies certain bioethical doctrines may come into conflict with the needs and ethics of public health. The growth of antibiotic resistance in bacteria and the spread of HIV both contribute to the difficulty of controlling infectious disease. These two sets of priorities need to be reconciled and this is likely to require a reassessment of prevailing ethical doctrines in the face of the needs of public health.

Bioethics↗