Angiogenic activity of human CC chemokine CCL15 in vitro and in vivo

CCL15 is a novel human CC chemokine and exerts its biological activities on immune cells through CCR1 and CCR3. Because a number of chemokines induce angiogenesis and endothelial cells express CCR1 and CCR3, we investigated the angiogenic activity of CCL15. Both CCL15(1-92) and N-terminal truncated CCL15(25-92) stimulate the chemotactic endothelial cell migration and differentiation, but CCL15(25-92) is at least 100-fold more potent than CCL15(1-92). Treatment with pertussis toxin (PTX), with anti-CCR1, or with anti-CCR3 antibody inhibits the CCL15(25-92)-induced endothelial cell migration. CCL15(25-92) also stimulates sprouting of vessels from aortic rings and mediates angiogenesis in the chick chorioallantoic membrane assay. Our findings demonstrate that CCL15(25-92) has in vitro and in vivo angiogenic activity, and suggest roles of the chemokine in angiogenesis.     

A myriad of functions and complex regulation of the CCR7/CCL19/CCL21 chemokine axis in the adaptive immune system

The chemokine receptor CCR7 and its ligands CCL19 and CCL21 control a diverse array of migratory events in adaptive immune function. Most prominently, CCR7 promotes homing of T cells and DCs to T cell areas of lymphoid tissues where T cell priming occurs. However, CCR7 and its ligands also contribute to a multitude of adaptive immune functions including thymocyte development, secondary lymphoid organogenesis, high affinity antibody responses, regulatory and memory T cell function, and lymphocyte egress from tissues. In this survey, we summarise the role of CCR7 in adaptive immunity and describe recent progress in understanding how this axis is regulated. In particular we highlight CCX-CKR, which scavenges both CCR7 ligands, and discuss its emerging significance in the immune system.     

In vitro selection of RNA aptamers that inhibit the activity of type A botulinum neurotoxin

The category A agent, botulinum neurotoxin (BoNT), is the most toxic molecule known to mankind. The endopeptidase activity of light chain domain of BoNT is the cause for the inhibition of the neurotransmitter release and the flaccid paralysis that leads to lethality in botulism. Currently, antidotes are not available to reverse the flaccid paralysis caused by BoNT. In the present study, we have identified three RNA aptamers through SELEX-process, which bind strongly to the light chain of type A BoNT (BoNT/A) and inhibit the endopeptidase activity, with IC₅₀ in low nM range. Inhibition kinetic studies reveal low nM K_I and non-competitive nature of their inhibition. Aptamers are unique group of molecules as therapeutics, and this is first report of their development as an antidote against botulism. These data on K_I and IC₅₀ strongly suggest that the aptamers have strong potential as antidotes that can reverse the symptom caused by BoNT/A.     

In vitro selection of RNA aptamers that selectively bind danofloxacin

Danofloxacin is a synthetic fluoroquinolone with broad spectrum antibacterial activity that is used for the treatment of respiratory diseases in animal husbandry. However, danofloxacin has many adverse reactions and is toxic to humans. Especially, it detrimentally affects muscle, central nerve system, peripheral nerve system, liver, and skin in those who ingest foods in which danofloxacin has accumulated. Prescreening and determination of the level of danofloxacin in foods or food products is necessary for human health. Aptamers are composing of oligonucleotides that specifically interact with target molecules. They are emerging as detection/diagnostic ligands. Here, we used the SELEX in vitro selection technology to identify specific and high-affinity RNA aptamers with 2′-fluoro-2′-deoxyribonucleotide modified pyrimidine nucleotides against danofloxacin. Selected RNA aptamers bound specifically to danofloxacin, but not to tetracycline. Truncation of RNA aptamer up to 36 mer did not comprise specificity and affinity. The truncated RNA aptamer specifically bound to target chemical, allowing the discrimination of danofloxacin from other fluoroquinolones. The isolated specific aptamer could be a potential agent used for the rapid and cost-effective detection and sensing of danofloxacin, replacing instrumental methods including the more expensive and time-consuming methods of high performance liquid chromatography and liquid chromatography/mass spectrometry.     

Differential CCR1-mediated chemotaxis signaling induced by human CC chemokine HCC-4/CCL16 in HOS cells

Human CC chemokine-4 (HCC-4)/CCL16 is a chemoattractant for monocytes and lymphocytes. Although HCC-4 binds to multiple CC chemokine receptors, the receptor-mediated signal transduction pathway induced by HCC-4 has not been characterized. Human osteogenic sarcoma cells stably expressing CCR1 were used to investigate HCC-4-mediated chemotaxis signaling events via CCR1. The chemotactic activity of HCC-4 as well as those of other CCR1-dependent chemokines including MIP-1alpha/CCL3, RANTES/CCL5, and Lkn-1/CCL15 was inhibited by the treatment of pertussis toxin, an inhibitor of Gi/Go protein, U73122, an inhibitor of phospholipase C (PLC), and rottlerin, a specific inhibitor of protein kinase Cdelta (PKCdelta). These results indicate that HCC-4-induced chemotaxis signaling is mediated through Gi/Go protein, PLC, and PKCdelta. SB202190, an inhibitor of p38 mitogen activated protein kinase, only blocked the chemotactic activity of HCC-4, but not those of other CCR1-dependent chemokines. SB202190 inhibited HCC-4-induced chemotaxis in a dose-dependent manner (P < 0.01). HCC-4 induces p38 activation in both a time and dose-dependent manner. However, such p38 activation was not induced by other CCR1-dependent chemokines. To further investigate the differential effect of HCC-4, the Ca2+ mobilization was examined. HCC-4 induced no intracellular Ca2+ flux in contrast to other CCR1-dependent chemokines. These results indicate that HCC-4 transduces signals differently from other CCR1-dependent chemokines and may play different roles in the immune response.     

In vitro selection of DNA aptamers binding pesticide fluoroacetamide

Fluoroacetamide (Mw = 77.06) is a lethal rodenticide to humans and animals which is still frequently abused in food storage somewhere in China. The production of antibodies for fluoroacetamide is difficult due to its high toxicity to animals, which limits the application of immunoassay method in poison detection. In this work, aptamers targeting N-fluoroacetyl glycine as an analog of fluoroacetamide were selected by a specific systematic evolution of ligands by exponential enrichment (SELEX) strategy. The binding ability of the selected aptamers to fluoroacetamide was identified using surface plasmon resonance (SPR)-based assay. The estimated K_D values in the low micromolar range showed a good affinity of these aptamers to the target. Our work verified that the SELEX strategy has the potential for developing aptamers targeted to small molecular toxicants and aptamers can be employed as new recognition elements instead of antibodies for poison detection.     

In vitro selection of high-affinity DNA aptamers for streptavidin

In this study, we developed a systematic evolution of ligands by exponential enrichment （SELEX） method using a combination of magnetic beads immobilization and flow cytometric measurement. As an example, the selection of streptavidin-specific aptamers was performed. In this protocol, the conventional SELEX procedure was optimized, fiirst using magnetic beads for target immobilization to facilitate highly efficient separation of the binding single-stranded DNA （ssDNA） aptamers from the unbound ssDNAs, and second using flow cytometry and fluorescein labeling to monitor the enrichment. The sensitivity of flow cytometry was adequate for ssDNA quantification during the SELEX procedures. The streptavidin-specific aptamers obtained in this work can be used as tools for characterization of the occupancy of streptavidin-modified surfaces with biotinylated target molecules. The method described in the study is also generally applicable to target molecules other than streptavidin.     

In vitro selection of DNA aptamers binding ethanolamine

We have identified aptamers (synthetic oligonucleotides) binding to the very small molecule ethanolamine with high affinity down to the low nanomolar range. These aptamers were selected for their ability to bind to ethanolamine immobilised on magnetic beads, from an 96mer library of initially about 1 x 10(16) randomised ssDNA molecules. The dissociation constants of these aptamers range between K(D)=6 and K(D)=19 nmol L(-1). The aim of the development of ethanolamine aptamers is their use for the detection of this substance in clinical and environmental analysis. Ethanolamine is associated with several diseases. Moreover, ethanolamine and its derivatives di- and tri-ethanolamine are used in chemical and cosmetic industries. The use of biosensors with ethanolamine aptamer as new molecular recognition element could be an innovative method for an easy and fast detection of ethanolamine.     

The discovery of BMS-457, a potent and selective CCR1 antagonist

A series of compounds which exhibited good human CCR1 binding and functional potency was modified resulting in the discovery of a novel series of high affinity, functionally potent antagonists of the CCR1 receptor. Issues of PXR activity, ion-channel potency, and poor metabolic stability were addressed by the addition of a hydroxyl group to an otherwise lipophilic area in the molecule resulting in the discovery of preclinical candidate BMS-457 for the treatment of rheumatoid arthritis.     

In vitro selection of DNA aptamers against the HIV-1 TAR RNA hairpin

In vitro selection was performed to identify DNA aptamers against the TAR RNA stem-loop structure of HIV-1. A counterselection step allowed the elimination of kissing complex-forming aptamers previously selected (Boiziau et al. J. Biol. Chem. 1999; 274:12730). This led to the emergence of oligonucleotides, most of which contained two consensus sequences, one targeted to the stem 3'-strand (5'-CCCTAGTTA) and the other complementary to the TAR apical loop (5'-CTCCC). The best aptamer could be shortened to a 19-mer oligonucleotide, characterized by a dissociation constant of 50 nM. A 16-mer oligonucleotide complementary to the TAR stem 3'-strand could also be derived from the identified aptamers, with an equal affinity (Kd = 50 nM). Experiments performed to elucidate the interaction between TAR and the aptamers (UV melting measures, enzymatic and chemical footprints) demonstrated that the TAR stem 5'-strand was not simply displaced as a result of the complex formation but unexpectedly remained associated on contact with the antisense oligonucleotide. We suggest that a multistranded structure could be formed.     

First report of in vitro selection of RNA aptamers targeted to recombinant Loxosceles laeta spider toxins

Background

Loxoscelism is the envenomation caused by the bite of Loxosceles spp. spiders. It entails severe necrotizing skin lesions, sometimes accompanied by systemic reactions and even death. There are no diagnostic means and treatment is mostly palliative. The main toxin, found in several isoforms in the venom, is sphingomyelinase D (SMD), a phospholipase that has been used to generate antibodies intended for medical applications. Nucleic acid aptamers are a promising alternative to antibodies. Aptamers may be isolated from a combinatorial mixture of oligonucleotides by iterative selection of those that bind to the target. In this work, two Loxosceles laeta SMD isoforms, Ll1 and Ll2, were produced in bacteria and used as targets with the aim of identifying RNA aptamers that inhibit sphingomyelinase activity.

Results

Six RNA aptamers capable of eliciting partial but statistically significant inhibitions of the sphingomyelinase activity of recombinant SMD-Ll1 and SMD-Ll2 were obtained: four aptamers exert ~17% inhibition of SMD-Ll1, while two aptamers result in ~25% inhibition of SMD-Ll2 and ~18% cross inhibition of SMD-Ll1.

Conclusions

This work is the first attempt to obtain aptamers with therapeutic and diagnostic potential for loxoscelism and provides an initial platform to undertake the development of novel anti Loxosceles venom agents.     

Clinical grade production and characterization of a fusion protein comprised of the chemokine CCL2-ligand genetically fused to a mutated and truncated form of the Shiga A1 subunit

First generation chemokine ligand-Shiga A1 (SA1) fusion proteins (leukocyte population modulators, LPMs) were previously only obtained in small quantities due to the ribosomal inactivating protein properties of the SA1 moiety which inhibits protein synthesis in host cells. We therefore employed 4-aminopyrazolo[3,4-d]-pyrimidine, an inhibitor of Shiga A1, to allow the growth of these cells prior to induction and during the expression phase post-induction with IPTG. Scale-up allowed the production of gram quantities of clinical grade material of the lead candidate, OPL–CCL2–LPM. A manufacturing cell bank was established and used to produce OPL–CCL2–LPM in a fed-batch fermentation process. Induction of the expression of OPL–CCL2–LPM led to the production of 22.47 mg/L per OD₆₀₀ unit. The LPM was purified from inclusion bodies using solubilization, renaturation, refolding and chromatography steps. The identity and purity of the OPL–CCL2–LPM was determined using several analytical techniques. The product retained the ability of the SA1 moiety to inhibit protein synthesis as measured in a rabbit reticulocyte lysate cell-free protein synthesis assay and was cytotoxic to target cells. Binding studies established that the protein exerts its effects via CCR2, the cognate receptor for CCL2. Clinical trials in inflammatory nephropathies are planned.     

In vitro selection of an archaeal RNase P RNA mimics natural variation

Archaeal and bacterial RNase P RNAs are similar in sequence and secondary structure, but in the absence of protein, the archaeal RNAs are much less active and require extreme ionic conditions for activity. To assess how readily the activity of the archaeal RNA alone could be improved by small changes in sequence, in vitro selection was used to generate variants of a Methanobacterium formicicum RNase P RNA: Bacillus subtilus pre-tRNA(Asp) self-cleaving conjugate RNA. Functional variants were generated with a spectrum of mutations that were predominately consistent with natural variation in this RNA. Variants generated from the selection had cleavage rates comparable to that of wild type; variants with improved cleavage rates or lower ionic requirements were not obtained. This suggests that the RNase P RNAs of Bacteria and Archaea are globally optimized and the basis for the large biochemical differences between these two types of RNase P RNA is distributed in the molecule.     

In vitro selection of novel RNA ligands that bind human cytomegalovirus and block viral infection

Ribonuclease-resistant RNA molecules that bind to infectious human cytomegalovirus (HCMV) were isolated in vitro from a pool of randomized sequences after 16 cycles of selection and amplification. The two ligands (L13 and L19) characterized exhibited high HCMV-binding affinity in vitro and effectively inhibited viral infection in tissue culture. Their antiviral activity was also specific as they only reacted with two different strains of HCMV but not with the related herpes simplex virus 1 and human cells. These two ligands appeared to function as antivirals by blocking viral entry. Ultraviolet (UV) crosslinking studies suggested that L13 and L19 bind to HCMV essential glycoproteins B and H, respectively. Thus, RNA ligands that bind to different surface antigens of HCMV can be simultaneously isolated by the selection procedure. Our study demonstrates the feasibility of using these RNA ligands as a research tool to identify viral proteins required for infectivity and as an antiviral agent to block viral infection.     

PLP2/A4 interacts with CCR1 and stimulates migration of CCR1-expressing HOS cells

Multiple CC chemokines bind to CCR1, which plays important roles in immune and inflammatory responses. To search for proteins involved in the CCR1 signaling pathway, we screened a yeast two-hybrid library using the cytoplasmic tail of CCR1 as the bait. One of the positive clones contained an open reading frame of 456bp, of which the nucleotide sequence was identical to that of proteolipid protein 2 (PLP2), also known as protein A4. Mammalian two-hybrid and coimmunoprecipitation analyses demonstrated the association of PLP2/A4 with CCR1. Indirect immunofluorescence analysis revealed that PLP2/A4 was predominantly located in plasma membrane and colocalized with CCR1 in transfected human HEK293 cells. In addition, focal staining of CCR1 appeared on the periphery of the membrane upon short exposure to Leukotactin-1(Lkn-1)/CCL15, a CCR1 agonist, and was costained with PLP2/A4 on the focal regions. PLP2/A4 mRNAs were detected in various cells such as U-937, HL-60, HEK293, and HOS cells. Overexpression of PLP2/A4 stimulated a twofold increase in the agonist-induced migration of HOS/CCR1 cells, implicating a functional role for PLP2/A4 in the chemotactic processes via CCR1.     

In vitro selection of RNA aptamers that bind to colicin E3 and structurally resemble the decoding site of 16S ribosomal RNA

Colicin E3 is a ribonuclease that specifically cleaves at the site after A1493 of 16S rRNA in Escherichia coli ribosomes, thus inactivating translation. To analyze the interaction between colicin E3 and 16S rRNA, we used in vitro selection to isolate RNA ligands (aptamers) that bind to the C-terminal ribonuclease domain of colicin E3, from a degenerate RNA pool. Although the aptamers were not digested by colicin E3, they specifically bound to the protein (K(d) = 2-14 nM) and prevented the 16S rRNA cleavage by the C-terminal ribonuclease domain. Among these aptamers, aptamer F2-1 has a sequence similar to that of the region around the cleavage site from residue 1484 to 1506, including the decoding site, of E. coli 16S rRNA. The secondary structure of aptamer F2-1 was determined by the base pair covariation among the variants obtained by a second in vitro selection, using a doped RNA pool based on the aptamer F2-1 sequence. The sequence and structural similarities between the aptamers and 16S rRNA provide insights into the recognition of colicin E3 by this specific 16S rRNA region.