Generation of lyso-phospholipids from surfactant in acute lung injury is mediated by type-II phospholipase A2 and inhibited by a direct surfactant protein A-phospholipase A2 protein interaction.

Lyso-phospholipids exert a major injurious effect on lung cell membranes during Acute Respiratory Distress Syndrome (ARDS), but the mechanisms leading to their in vivo generation are still unknown. Intratracheal administration of LPS to guinea pigs induced the secretion of type II secretory phospholipase A2 (sPLA2-II) accompanied by a marked increase in fatty acid and lyso-phosphatidylcholine (lyso-PC) levels in the bronchoalveolar lavage fluid (BALF). Administration of LY311727, a specific sPLA2-II inhibitor, reduced by 60% the mass of free fatty acid and lyso-PC content in BALF. Gas chromatography/mass spectrometry analysis revealed that palmitic acid and palmitoyl-2-lyso-PC were the predominant lipid derivatives released in BALF. A similar pattern was observed after the intratracheal administration of recombinant guinea pig (r-GP) sPLA2-II and was accompanied by a 50-60% loss of surfactant phospholipid content, suggesting that surfactant is a major lung target of sPLA2-II. In confirmation, r-GP sPLA2-II was able to hydrolyze surfactant phospholipids in vitro. This hydrolysis was inhibited by surfactant protein A (SP-A) through a direct and selective protein-protein interaction between SP-A and sPLA2-II. Hence, our study reports an in vivo direct causal relationship between sPLA2-II and early surfactant degradation and a new process of regulation for sPLA2-II activity. Anti-sPLA2-II strategy may represent a novel therapeutic approach in lung injury, such as ARDS.

DNA rearrangements and antigenic variation in Trypanosoma equiperdum: multiple expression-linked sites in independent isolates of trypanosomes expressing the same antigen.

African trypanosomes resist the immune response of their mammalian hosts by varying the surface glycoprotein which constitutes their antigenic identity. The molecular mechanism of this antigenic variation involves the successive activation of a series of genes which code for different variant surface glycoproteins (VSGs). We have studied the expression of two VSG genes (those of VSG-1 and VSG-28) in Trypanosoma equiperdum, and we report the following findings. (i) The expression of both VSG genes is associated with the duplication and transposition of corresponding basic copy genes. (ii) The duplicated transposed copy appears to be the expressed copy. (iii) Although there are multiple genes which cross-hybridize with the VSG-1 cDNA probe, only one of these appears to be used as a template for the expression-linked copy in four independent BoTat-1 clones. (iv) Analysis of the genomic environments of the expressed VSG-1 genes from each of four independently derived BoTat-1 trypanosome clones revealed that there are at least three different sites into which the expression-linked copy can be inserted.

DNA rearrangements and antigenic variation in Trypanosoma equiperdum: expression-independent DNA rearrangements in the basic copy of a variant surface glycoprotein gene.

Antigenic variation in Trypanosoma equiperdum is associated with the sequential expression of variant surface glycoprotein (VSG) genes in a process which involves gene duplication and transposition events. In this paper we present evidence that the genomic environment of the VSG-1 basic copy gene, the template for duplicated, expression-linked VSG-1 genes, differs in every trypanosome clone examined. This variation is thus independent of the expression of the VSG-1 gene, and it also appears to be restricted to the 3' genomic environment. It is also demonstrated that the DNA located 3' to the VSG-1 basic copy gene is moderately sensitive to digestion when the nuclei of either expressor or non-expressor trypanosomes are treated with DNase I.

Crystal structure of a Fab complex formed with PfMSP1-19, the C-terminal fragment of merozoite surface protein 1 from Plasmodium falciparum: a malaria vaccine candidate.

Merozoite surface protein 1 (MSP1) is the major protein component on the surface of the merozoite, the erythrocyte-invasive form of the malaria parasite Plasmodium. Present in all species of Plasmodium, it undergoes two distinct proteolytic maturation steps during the course of merozoite development that are essential for invasion of the erythrocyte. Antibodies specific for the C-terminal maturation product, MSP1-19, can inhibit erythrocyte invasion and parasite growth. This polypeptide is therefore considered to be one of the more promising malaria vaccine candidates. We describe here the crystal structure of recombinant MSP1-19 from P.falciparum (PfMSP1-19), the most virulent species of the parasite in humans, as a complex with the Fab fragment of the monoclonal antibody G17.12. This antibody recognises a discontinuous epitope comprising 13 residues on the first epidermal growth factor (EGF)-like domain of PfMSP1-19. Although G17.12 was raised against the recombinant antigen expressed in an insect cell/baculovirus system, it binds uniformly to the surface of merozoites from the late schizont stage, showing that the cognate epitope is exposed on the naturally occurring MSP1 polypeptide complex. Although the epitope includes residues that have been mapped to regions recognised by invasion-inhibiting antibodies studied by other workers, G17.12 does not inhibit erythrocyte invasion or MSP1 processing.

Plasmodium vivax merozoite surface protein 1 C-terminal recombinant proteins in baculovirus.

Recombinant proteins derived from the Plasmodium vivax merozoite surface protein 1 have been produced in the baculovirus expression system. These proteins correspond approximately to the Plasmodium vivax analogs of the 42-kDa or 19-kDa C-terminal processing products previously described for Plasmodium falciparum. Each was produced in two versions, either as a membrane-bound entity located on the cell surface and probably carrying a glycosylphosphatidylinositol addition, or as a secreted entity lacking a membrane anchor. Many native conformational epitopes appear to be accurately reproduced in these molecules. Both the 42-kDa and 19-kDa analogs can be N-glycosylated in the baculovirus system and the N-glycosylation appears to be necessary for efficient secretion of both the 42-kDa and 19-kDa recombinant proteins.

Absorption and disposition of 14C-labelled Kathon biocide, a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one, following intravenous or dermal administration to male Sprague-Dawley rats.

Kathon biocide (KB), a 75:25 mixture of 5-chloro-2-methyl-4-isothiazolin-3-one (KI) and 2-methyl-4-isothiazolin-3-one (KII), is a broad-spectrum antimicrobial agent. The absorption and disposition of 14C label were studied in male Sprague-Dawley rats following iv or dermal administration of KB 14C labelled in the carbonyl carbon of either KI or KII. KI-labelled Kathon was distributed rapidly following an iv dose (0.8 mg/kg). Total 14C label in the plasma was rapidly eliminated, with the data best described by a three-compartment model. Total 14C label concentration in the blood, however, remained constant at 3 ppm from 6 to 96 hr after administration and represented 29% of the dose, indicating that KI-labelled Kathon and/or metabolites was sequestered by the cellular fraction of blood. Elimination of 14C label from the tissues examined was biphasic, with a terminal half-life of more than 4 days; by 96 hr, faeces, urine and CO2 accounted for 35, 31 and 4% of the dose, respectively. Following a single 24-hr dermal application of 0.2 ml of an aqueous solution containing 2000 ppm [14C]KB (400 micrograms), rats absorbed 94% of KI-labelled KB and 82% of KII-labelled KB. However, the systemic bioavailability of KB was substantially less than this, since approximately half of the absorbed KB was associated with the skin at the application site 24 hr after the application. Percutaneous absorption was not affected by concentration over the range 500-4000 ppm. As the concentration of KI-labelled KB in the applied solution increased from 500 to 4000 ppm, the relative amount of 14C label associated with the skin decreased, while that in the excreta increased, indicating greater systemic penetration at higher concentrations. Low amounts of 14C label were found in the testes (less than 2 ppb) and blood (24 ppb) 28 days after a single dermal application of KI-labelled KB. Four consecutive daily applications of KI-labelled KB did not influence the proportion of the dose absorbed from the skin. However, the proportion of the dose excreted was higher than after a single application of an equivalent amount of KB.

Expression of whole and hybrid genes in Trypanosoma equiperdum antigenic variation.

A rapid technique involving the S1 nuclease resistance of RNA:DNA duplexes has been used to screen four Trypanosoma equiperdum variant surface glycoprotein (VSG) genes for evidence of hybrid gene structure in their transcribed regions. The results suggest that VSGs appearing early in a chronic infection each have a complete co-linear basic copy (BC) of their expressed gene while VSGs appearing later in infection are particularly associated with BC genes which are recombined before being expressed. The intensities of the S1-protected bands from hybrid VSGs indicate that the basic and expression linked copies are present in equivalent gene dosages. In addition, studies are presented on the expression of two additional VSG genes in T. equiperdum, VSG 4 and VSG 78, which (i) show that the basic copies are not located on telomeres even though one (VSG 4) is expressed early in infection and (ii) emphasize the role of a predominant expression site in T. equiperdum while nevertheless confirming the presence of multiple expression sites.

Azacytidine-induced reactivation of adenosine deaminase in a murine cytotoxic T cell line.

In C57BL/6 mice, cytotoxic T lymphocyte (CTL) lines have previously been found to exhibit low (less than 150 U/mg) or undetectable (less than 20 U/mg) adenosine deaminase (ADA) levels (Minkowski, Castellazzi and Buttin, J. Immunol. 1984. 133: 52) in contrast to what has been seen in T helper lines (1770 +/- 340 U/mg; Minkowski and Bandeira, Cell. Immunol. 1985. 95: 380). Treatment of one of these CTL ADA- lines with the demethylating agent 5-azacytidine gave rise to an ADA+ population. Subsequent cloning allowed the recovery of pure ADA+ clones showing a rather narrow range of activity with an average value of 2030 +/- 504 U/mg. The restored ADA+ activity is stable over several months of continuous growth. It is identical to the activity of C57BL/6 thymic cells or C57BL/6 T tumor lines regarding its sensitivity to ADA inhibitors 2-deoxycoformycin and erythro-9-(2-hydroxyl-3-nonyl)adenine, and its electrophoretic mobility under nondenaturing conditions (starch gel and isoelectric focusing). An ADA-specific, 1.4-kb mRNA is present in the reactivated clones but is undetectable in the CTL ADA- parental line. These results demonstrate that the ADA- phenotype is due to an extinction of the corresponding gene. They suggest that the extinction of the ADA gene which appears to be specific for CTL and to take place in vivo during T cell differentiation may result from increased methylation in or near the ADA gene. This extinction seems to affect specifically ADA since nucleoside phosphorylase, the enzyme which follows ADA in the purine salvage pathway, is present at equivalent levels in the ADA- and ADA+ CTL clones.

A precise quantitation of gene number by saturation hybridization using cloned DNA.

This paper describes a precise method of gene titration as applied to the alpha- and beta-globin genes in the mouse. The three salient features of the method are: (i) the use of saturation hybridization in probe cDNA excess, (ii) the use of highly purified cDNA probes prepared by preparative hybridization with cloned globin sequences (Longacre and Mach (1978) J. Biol. Chem. 253, 7500) and (iii) the use of cloned globin sequences to calibrate the system internally. The results indicate that there are two genes for alpha-globin and two genes for beta-globin in the BALB/c mouse. The significance of these results are discussed in relation to other data regarding adult and embryonic globin genes.

Purification of specific DNA sequences by sulfhydryl-Sepharose chromatography of mercurated polynucleotides.

Recombinant plasmid DNA has been used to purify complementary cDNA by hybridization using a modification of sulfhydryl-Sepharose chromatography described by Dale and Ward ((1975) Biochemistry 14, 2458). Plasmid DNA containing cloned mouse globin or immunoglobulin sequences was mercurated and hybridized in solution to unpurified cDNA. The resulting hybrids were passed over a sulfhydryl-Sepharose column where mercurated polynucleotides are retained. After washing, cDNA hybridized to the mercurated plasmid DNA was melted in situ and eluted while the mercurated plasmid DNA remained bound to the column. The conditions for purification of DNA and RNA sequences are described. The purity of the cDNAs obtained by this method is analyzed by polyacrylamide gel electrophoresis and by hybridization. In addition, this nucleic acid purification procedure has been applied to two problems of general interest: (i) the sensitive titration of specific genes by saturation hybridization; (ii) the purification of DNA fragments bearing specific sequences from restriction endonuclease digests of total cellular DNA. The procedure is generally applicable to the purification by hybridization of any DNA or RNA sequence complementary to an available probe.

Isolation of chicken hemoglobin mRNA and synthesis of complementary DNA.

Chicken globin mRNA has been purified and partially characterized. Globin-specific sequences are found primarily as 9 S RNA, but also are found with ribosomal RNA, preferentially the 28 S moiety. The chicken globin mRNA preparation has been translated in the wheat germ and Krebs ascites cell-free systems. The products have been identified by sodium dodecyl sulfate-gel electrophoresis as the alpha- and beta-globin polypeptides. The globin mRNA is resolved into two asymmetric peaks by polyacrylamide gel electrophoresis in 98% formamide. The minor rapidly migrating peak consists primarily of alpha message while the major slowly migrating peak contains a mixture of alpha and beta messages. The synthesis of cDNA has been optimized and the products analyzed by polyacrylamide gel electrophoresis in 98% formamide. The products consist primarily of full copy transcripts that can be resolved into three discrete species.

Nucleotide polymerases in the developing avian erythrocyte.

Avian erythroid cells were separated into five developmental stages by sedimentation on discontinuous isotonic albumin gradients. Solubilized enzyme activities from whole cells were partially purified and characterized by ion exchange and ion filtration chromatography and velocity sedimenttation analysis. Three nucleotide polymerase types were investigated: (a) DNA-dependent RNA polymerases; (b) RNA-dependent terminal ribonucleotidyltransferases, and (c) DNA-dependent DNA polymerases. The two characteristic forms of eucaryotic DNA-dependent RNA polymerases, polymerase I (nucleolar) and polymerase II (nucleoplasmic), were identified. Polymerase III was only marginally detectable even in the earliest developmental populations. At least two species of RNA-dependent terminal ribosyltransferases were present. One apparently was the poly(A) polymerase observed in other systems. The other terminal transferase was present in two chromatographic forms, required an RNA primer, and used UTP and/or CTP as particularly efficient substrates. Three DNA polymerase activities were resolved, two of which were characteristic of the alpha and beta DNA polymerases described in other eucaryotic systems. The third polymerase was not the gamma polymerase but a separate entity. Poly(dC)-dependent RNA polymerase activity, associated with the alpha polymerase, was relatively enriched in the third DNA polymerase species. The activity levels of the nucleotide polymerases were monitored as a function of red cell maturation. Characteristic declining patterns of activity were obtained for each enzyme which correlate well with the synthetic rates of their in vivo products where these are known. These results correlate well with the synthetic rates of their in vivo products where these are known. These results are consistent with the postulate that the general transcriptive and replicative control processes operating during development may involve changes in the level of the requisite polymerases.

The use of incomplete genes for the construction of a Trypanosoma equiperdum variant surface glycoprotein gene.

The expression of Trypanosoma equiperdum variant surface protein (VSG) 78 is accomplished by the duplicative transposition of silent basic copy (BC) genes into a telomer-linked expression site to form an expression-linked copy (ELC). In two independent isolates expressing VSG 78, the ELC is a composite gene. The analysis of VSG 78 cDNA clones from these two Bo Tat 78 isolates and the respective BC genes revealed that both ELCs were constructed from the same three BC genes, a 3' BC which donated the last 255 bp of each ELC and two closely related 5' BCs. Although sequences of both 5' BC genes were found in each ELC, the junction with the 3' BC was provided by the same 5' BC in both cases. This 5' BC is an incomplete gene with insufficient open reading frame to code for a complete VSG and thus can only be used when joined to a competent 3' end. Furthermore, both 5' BC genes lack a conserved 14 nucleotide sequence found on all VSG mRNAs. These results support a model in which composite gene formation plays a role in the determination of the order of VSG expression. They also illustrate similarities between immunoglobulin gene and VSG gene construction.

Primary structure of the merozoite surface antigen 1 of Plasmodium vivax reveals sequences conserved between different Plasmodium species.

Merozoite surface antigen 1 (MSA1) of several species of plasmodia has been shown to be a promising candidate for a vaccine directed against the asexual blood stages of malaria. We report the cloning and characterization of the MSA1 gene of the human malaria parasite Plasmodium vivax. This gene, which we call Pv200, encodes a polypeptide of 1726 amino acids and displays features described for MSA1 genes of other species, such as signal peptide and anchoring sequences, conserved cysteine residues, number of potential N-glycosylation sites, and repeats consisting here of 23 glutamine residues in a row. When the nucleotide and deduced amino acid sequences of the MSA1 of P. vivax are compared to those of another human malaria parasite, Plasmodium falciparum, and to those of the rodent parasite Plasmodium yoelii, 10 regions of high amino acid similarity are observed despite the very different dG + dC contents of the corresponding genes. All of the interspecies conserved regions reside within the conserved or semiconserved blocks delimited by the sequences of different alleles of the MSA1 gene of P. falciparum.