Inhibition of HIV‐1 or bacterial activation of macrophages by products of HIV‐1‐resistant human cells

We have recently described the molecular basis of HIV-1 resistance factor (HRF)-mediated anti-viral activity in primary and transformed CD4 T cells. HRF+ cell culture supernatants or partially purified HRF were found to incapacitate the formation of the NF-kappaB/DNA complex, which is indispensable for long terminal promoter-driven transcription of virus genes. In this study, we tested whether HRF might have much broader activity against other organisms whose pathogenesis is linked to NF-kappaB activation. Specifically, we tested the effects of HRF on the NF-kappaB-mediated responses of primary macrophages to HIV-1 or several bacterial antigens. We found that exposure to HRF inhibited HIV-1 expression in macrophages and also induced the production of HRF-like activity by macrophages, which prevented replication of virus in HIV-1-infected peripheral blood lymphocytes cultured in the adjacent compartment. We investigated the mechanism of this inhibition and found that HRF impeded NF-kappaB/DNA binding in macrophages induced by either HIV-1 or lipopolysaccharide from several bacteria species, resulting in impaired tumor necrosis factor-alpha responses to these organisms.

Trypsin inhibitors from the garden four o'clock (Mirabilis jalapa) and spinach (Spinacia oleracea) seeds: isolation, characterization and chemical synthesis

Five serine proteinase inhibitors (Mirabilis jalapa trypsin inhibitors, MJTI I and II and Spinacia oleracea trypsin inhibitors, SOTI I, II, and III) from the garden four-o'clock (M. jalapa) and spinach (S. oleracea) seeds were isolated. The purification procedures included affinity chromatography on immobilized methylchymotrypsin in the presence of 5M NaCl, ion exchange chromatography and/or preparative electrophoresis, and finally RP-HPLC on a C-18 column. The inhibitors, crosslinked by three disulfide bridges, are built of 35 to 37 amino-acid residues. Their primary structures differ from those of known trypsin inhibitors, but showed significant similarity to the antimicrobial peptides isolated from the seeds of M. jalapa (MJ-AMP1, MJ-AMP2), Mesembryanthemum crystallinum (AMP1), and Phytolacca americana (AMP-2 and PAFP-S) and from the hemolymph of Acrocinus longimanus (Alo-1, 2 and 3). The association equilibrium constants (K(a)) with bovine beta-trypsin for the inhibitors from M. jalapa (MJTI I and II) and S. oleracea (SOTI I-III) were found to be about 10(7)M(-1). Fully active MJTI I and SOTI I were obtained by solid-phase peptide synthesis. The disulfide bridge pattern in both inhibitors (Cys1-Cys4, Cys2-Cys5 and Cys3-Cys6) was established after their digestion with thermolysin and proteinase K followed by the MALDI-TOF analysis.

Selection of new chromogenic substrates of serine proteinases using combinatorial chemistry methods

Chemical synthesis, physicochemical characterization and kinetic investigations of a tetrapeptide library of chromogenic substrates containing the amide of 5-amino-2-nitrobenzoic acid (Anb(5,2)-NH(2)) at their C-termini are reported. Anb(5,2)-NH(2) served as a chromophore released upon enzymatic action. The library consisting of 9567 peptides was synthesized using the portioning-mixing method and was screened against bovine a-chymotrypsin and human leukocyte elastase in solution applying an iterative approach. The selected chromogenic substrates were resynthesized and further modified at their N- and C-termini. Finally, two sequences, Z-Phe-Ala-Thr-Tyr-Anb(5,2)-NH(2) and Z-Phe-Phe-Pro-Val-Anb(5,2)-NH(2), were obtained as highly specific substrates for bovine alpha-chymotrypsin and human leukocyte elastase, respectively. The method of synthesis and selection of chromogenic substrates of serine proteinases described herein is straightforward and can be applied to design substrates for other proteases.

A soluble factor secreted by an HIV-1-resistant cell line blocks transcription through inactivating the DNA-binding capacity of the NF-kappa B p65/p50 dimer

The identity and activity of several anti-HIV soluble factor(s) secreted by CD8 and CD4 T lymphocytes have been determined; however, some of them still await definition. We have established an HIV-1-resistant, transformed CD4 T cell line that secretes HIV-1 resistance protein(s). Our studies indicate that this protein(s), called HIV-1 resistance factor (HRF), inhibits transcription of the virus by interfering with the activity of NF-kappaB. In the present report we identified the site at which HRF exerts this inhibition by evaluating a set of discrete events in NF-kappaB action. We tested the kappaB oligonucleotide binding activity in nuclei of resistant cells, nuclear translocation and binding to the HIV-1 long terminal repeat of p65 and p50 proteins from susceptible cells after exposure to HRF, and the binding of recombinant p50 to the kappaB oligonucleotide in vitro as affected by prior or simultaneous exposure to HRF. The results of this experimental schema indicate that HRF interacts with p50 after it enters the nucleus, but before its binding to DNA and that this interaction impedes the formation of an NF-kappaB-DNA complex required for the promotion of transcription. These findings suggest that HRF mediates a novel innate immune response to virus infection.

Monoubiquitinated histone H1B is required for antiviral protection in CD4(+)T cells resistant to HIV-1

Linker histone H1B (H1B) coeluted with an antiviral activity during the purification of HIV-1 resistance factor (HRF) from supernatants of HRF(+) cells. Western blot analysis of the supernatant using alpha-H1 and alpha-ubiquitin antibodies detected the same band of roughly 46 kDa; this band was absent from the control supernatant. Depletion of histone from biologically active material did not affect its potential, suggesting that ubiquitinated H1B is not required for the HRF-mediated antiviral protection in HIV-1 susceptible target cells; however, specific silencing of histone H1B via RNAi in HRF(+) cells reduced the biological activity of cell culture supernatants by 96% and reversed the HIV-1 resistance phenotype of HRF(+) cells. Exposure to HRF induced ubiquitination and secretion of H1B from target HIV-1 susceptible cells, suggesting that ubiquitinated H1B is a cofactor of HRF, possibly regulating its expression and secretion from CD4(+)T cells induced to resist HIV-1 infection.

Microarray analysis of differentially expressed genes in cells resistant to HIV-1

We have previously isolated two matched transformed human T cell clones: one of which is resistant to HIV-1 replication and secretes an HIV-1 resistance factor(s) (HRF) and the second which retains the susceptibility of the parental cell line to HIV-1 infection. We employed cDNA arrays to investigate the spectrum of changes in cellular gene expression that correlate with the acquisition of HIV-1 resistance and the secretion of HRF. Using a tissue based immunology/hematology array, we identified 29 transcripts that were differentially expressed by HRF(+) and HRF(-) cells. HRF(+) cells showed a selective down-regulation of 11 genes involved in transcription, several of which are implicated in either susceptibility of cells to HIV-1 or the promotion of HIV-1 transcription itself. In the group of the up-regulated genes, three were linked directly to the cellular resistance to HIV-1. One of the cDNAs placed on the array, representing the hypothetical protein KIAA0117 hybridized only with poly A+ RNA probes derived from HRF(+) cells. The specific up-regulation of two genes, the transcription repressor (CTCF) and hypothetical protein KIAA0117 was confirmed by RT-PCR and Northern blot. The role of KIAA0117 transcript in the resistance to HIV-1 replication needs to be determined.

A simple method for selection of trypsin chromogenic substrates using combinatorial chemistry approach

A tetrapeptide combinatorial library, considered as chromogenic substrates of bovine beta-trypsin, was synthesized by the solid phase method. The peptides contain an analog of p-nitroanilide, obtained by attaching 5-amino-2-nitrobenzoic acid (Anb(5,2)) to the C-termini. Deconvolution of the peptide library, performed in solution using an iterative method, yielded four efficient trypsin substrates. The most active one, Phe-Val-Pro-Arg-Anb(5,2)-NH(2), appeared to be 125-fold more active than Bz-D,L-Arg-pNA (BAPNA) used as a reference compound. The reported method of designing trypsin chromogenic substrate libraries is straightforward. Such p-nitroanilides may be useful for the investigation of any protease substrate specificity.

Induction of secreted human immunodeficiency virus type 1 (HIV-1) resistance factors in CD4-positive T lymphocytes by attenuated HIV-1 infection

This report describes induction of HIV-1 resistance and synthesis of resistance factors in immortal CD4-positive T lymphocytes. SupT1 cells were infected by NL4-3 attenuated by a defect in the vif gene through coculture with infected primary lymphocytes. Cell lines from this infection, termed R1, expressed CD4 and CXCR4, carried low levels of HIV-1 DNA, but expressed no other detectable viral products and were resistant to infection by wild-type HIV-1. Investigation of challenge infection in resistant R1 lines demonstrated entry, reverse transcription, and integration by incoming HIV-1 but no synthesis of viral RNA. By assay of marker gene expression, we found that Tat was unable to activate LTR-driven transcription in R1 lines. HIV-1-resistant R1 lines secreted soluble factors that inhibited productive infection of primary lymphocytes by several strains of HIV-1 and blocked viral RNA synthesis in newly infected cells. Resistance factors also blocked the induction of HIV-1 transcription in ACH-2 cells as assayed by viral antigen expression and Northern blot of viral RNA. Soluble factors produced by HIV-1-resistant, immortal R1 cells may form the basis of new approaches to control HIV-1 infection.

Chromogenic substrates of bovine beta-trypsin: the influence of an amino acid residue in P1 position on their interaction with the enzyme

The Cucurbita maxima trypsin inhibitor CMTI-III molecule was used as a vehicle to design and synthesize a series of trypsin chromogenic substrates modified in position P1: Ac-Ala-Val-Abu-Pro-X-pNA, where X = Orn, Lys, Arg, Har, Arg(NO(2)), Cit, Hci, Phe(p-CN), Phe(p-NH(2)); pNA = p-nitroanilide. The most active compounds (as determined by specificity constant k(cat)/K(m)) were peptides with the Arg and Lys residues in the position discussed. Changes in the length and the decrease of the positive charge of the amino acid residue side chain in position P(1) resulted in the decrease or loss of the affinity towards bovine beta-trypsin. Among peptides containing amino acid residues with uncharged side chains in position P1, only one with p-cyano-l-Phe revealed activity. These results correspond well with trypsin inhibitory activity of CMTI-III analogues modified in the equivalent position, indicating the same type of interaction between position P1 of the substrate or inhibitor and S1 site specificity of trypsin.

Synthesis, activity on NK-3 tachykinin receptor and conformational solution studies of scyliorhinin II analogs modified at position 16

Two analogs of a tachykinin family peptides - scyliorhinin II (ScyII): [Aib(16)]ScyII and [Sar(16)]ScyII were synthesized by the solid-phase method using Fmoc chemistry. Conformational studies in water and DMSO-d(6) on these peptides were performed using a combination of two-dimensional NMR and theoretical conformational analysis. The solution structure of the peptides studied is interpreted as an equilibrium of several conformers with different statistical weights. The structure of [Sar(16)]ScyII in water appeared to be more flexible, especially in the C-terminal fragment. A better defined structure for this analog was obtained in DMSO-d(6), in which the analysis resulted in a family of conformers with similar shapes. Some of these conformers were characterized by the presence of a 3(10)-helix in the N-terminal fragment and middle part of the molecule. The introduction of the Aib residue in position 16 significantly rigidifies the structure. For [Aib(16)]ScyII in both solvent systems very similar populations of conformations were obtained which are characterized by the presence of a 3(10)-helix in the 13-18 fragment. A common structural motif was found in conformationally constrained Cys(7)-Cys(13) fragment, which resembles the Greek letter 'omega'. The differences in the solution structure of the C-terminal fragment of the peptides studied are responsible for their specificity. [Aib(16)]ScyII showed 25% the agonistic activity of selective NK-3 agonist - senktide, but it also showed antagonist effect vs. this peptide, whereas [Sar(16)]ScyII appeared to be a full agonist of NK-3 tachykinin receptor.

Design, chemical synthesis and kinetic studies of trypsin chromogenic substrates based on the proteinase binding loop of Cucurbita maxima trypsin inhibitor (CMTI-III)

A series of trypsin chromogenic substrates with formula: Y-Ala-X-Abu-Pro-Lys-pNA, where X = Gly, Ala, Abu, Val, Leu, Phe, Ser, Glu and Y = Ac, H; pNA = p-nitroanilide was synthesized. The Cucurbita maxima trypsin inhibitor CMTI-III molecule was used as a vehicle to design the trypsin substrates. To evaluate the influence of position P(4) on the substrate-enzyme interaction, kinetic parameters of newly synthesized substrates with bovine beta-trypsin were determined. The increasing hydrophobicity of the amino acid residue (Gly, Ala, Abu, Val) introduced in position P(4) significantly enhanced the substrate specificity (k(cat)/K(m)) which was over 8 times higher for the last residue than that for the first one. The introduction of residues with more hydrophilic side chain (Glu, Ser) in this position reduced the value of this parameter. These results correspond well with those obtained using molecular dynamics of bovine beta-trypsin with monosubstituted CMTI-I analogues, indicating that in both trypsin substrate and inhibitor position 4 plays an important role in the interaction with the enzyme.

Distance between the basic group of the amino acid residue's side chain in position P1 of trypsin inhibitor CMTI-III and Asp189 in the substrate pocket of trypsin has an essential influence on the inhibitory activity

Three new analogues of trypsin inhibitor CMTI-III were synthesized by the solid-phase method: [Lys5]-CMTI-III, [Orn5]CMTI-III and [Dab5]CMTI-III. Only one analogue with L-lysine residue in position P1 showed inhibitory activity of the same order of magnitude as did wild CMTI-III. Two remaining analogues were completely inactive. A conclusion was drawn that the distance between the basic group of the amino acid residue's side chain in position P1 of the trypsin inhibitor CMTI-III and Asp189 in the substrate pocket of trypsin plays an essential role for the trypsin-inhibitor interaction.