Endolysin polypeptide

Abstract

The invention relates to the field of medicine, specifically to the field of treatment of conditions associated with Staphylococcus infection. The invention relates to a novel endolysin polypeptide specifically targeting a bacterial Staphylococcus cell. The invention further relates to said endolysin polypeptide for medical use, preferably for treating an individual suffering from a condition associated with Staphylococcus infection.

Claims

1. An endolysin polypeptide specific for Staphylococcus, said polypeptide comprising: a polypeptide with an amino acid sequence that has at least 90% sequence identity with SEQ ID NO: 2 over its entire length, or a polypeptide with an amino acid sequence that has at least 90% sequence identity with SEQ ID NO: 1 and having a truncation of at least 5, 10, 20, 30, or 40 amino acids in the region of amino acids 156 to 199 of SEQ ID NO: 1, wherein the endolysin polypeptide has enhanced specific activity and/or reduced immunogenicity than an endolysin polypeptide with the amino acid sequence according to SEQ ID NO: 1, and wherein the polypeptide is a synthetic molecule.

2. The endolysin polypeptide according to claim 1 with an amino acid sequence according to SEQ ID NO: 2.

3. A composition comprising the endolysin polypeptide of claim 1.

4. The composition according to claim 3, wherein the composition further comprises a pharmaceutically acceptable excipient.

5. The composition according to claim 3, wherein the composition further comprises an additional active ingredient.

6. A method of treatment of a condition associated with infection with a Staphylococcus, comprising administrating in a subject in need thereof an endolysin polypeptide according to claim 1.

7. A method for antimicrobial disinfection comprising contacting a device or equipment with an endolysin polypeptide according to claim 1.

Description

FIGURE LEGENDS

(1) FIG. 1. Representative image of minimal inhibitory concentrations (MIC) of an endolysin polypeptide according to the invention.

(2) FIG. 2. Thermal stability and specific activity of endolysin polypeptide according to the invention.

(3) FIG. 3. Turbidity reduction assays comparing SA.100 (upper pane and mid pane) with XZ.700 (lower pane).

EXAMPLES

(4) Materials and Methods

(5) Bacterial Strains, Culture Conditions, Phages and Plasmids

(6) E. coli XL1BlueMRF and E. coli Sure was used for the over-expression of polypeptides according to the invention, essentially as in WO2013/169102. Both strains were cultured in LB-PE medium at 30 C. with 100 g/ml ampicillin and 30 g/ml tetracycline for plasmid selection.

(7) DNA Techniques and Cloning Procedures Standard techniques according to Sambrook, Maniatis et al. (1989) were employed for cloning.

(8) Expression and Purification of Recombinant Endolysin Polypeptides

(9) Protein overexpression and partial purification was essentially done as previously described by others (Loessner et al., 1996, Schmelcher et al., 2010). In brief, plasmid bearing E. coli were grown in 250 ml modified LB medium (15 g/l tryptose, 8 g/l yeast extract, 5 g/l NaCl, pH 7.8) to an optical density at 600 nm (OD600 nm) of 0.4 to 0.6 and induced with 1 mM IPTG. Cells were further incubated for 4 hours at 30 C., or 18 hours at 20 C., cooled to 4 C., and harvested by centrifugation. Cell pellets were suspended in 5 ml immobilization buffer (50 mM NaH.sub.2PO.sub.4, 500 mM NaCl, 5 mM imidazole, 0.1% polysorbate20, pH 7.4). Cytosolic E. coli contents containing soluble recombinant proteins were liberated by a double passage through a French Pressure Cell Press (1200 psi, SLM Aminco, Urbana, Ill., U.S.) operated at 1200 psi. Other downstream processing steps included removal of insoluble cell debris by centrifugation, filter sterilization (0.2 m PES membrane, Millipore), and Immobilized Metal Affinity Chromatography (IMAC) purification using MicroBiospin (Bio-Rad, Hercules, Calif., U.S.) columns packet with low density Ni-NTA Superflow resin (Chemie Brunschwig AG, Basel, Switzerland). Ni-NTA immobilized proteins were on-column gravity flow washed with 5-10 column volumes immobilization buffer. Protein fractions were then eluted with elution buffer (50 mM NaH.sub.2PO.sub.4, 500 mM NaCl, 125 mM imidazole, 0.1% polysorbate20, pH 7.4) and dialyzed against two changes of dialysis buffer (50 mM NaH.sub.2PO.sub.4, 100 mM NaCl, 0.1% polysorbate20, pH 7.4). Protein concentrations were defined in a NanoDrop ND-1000 spectrophotmeter, corrected for specific absorbance at 280 nm as calculated from the primary amino acid sequence with Vector NTI software (Invitrogen, Carlsbad, Calif., U.S.) and estimated for purity by SDS-PAGE. Aliquots were stored at 20 C. mixed with 50% glycerol.

(10) Lyophilization of Recombinant Proteins

(11) IMAC purified proteins were dialyzed against 3 changes of 300 ml lyophilization buffer (50 mM phosphate or Tris, 500 mM sucrose, 200 mM mannitol, pH 7.4) aliquot and frozen in the gaseous phase of liquid nitrogen. The freeze-drying was done at 40 C. and vacuum at 75 mTorr for 60 minutes, followed by increasing temperature during 5 hours to 10 C. and another 60 minutes at 10 C. at the same vacuum levels. As final step, temperature was increased to 25 C. during 10 hours. Samples were reconstituted prior to testing in lysis assays by the addition of water.

(12) Turbidity Lysis Assays

(13) Substrate cells for lytic activity assays were grown to an optical density at 595 nm (OD595) of 0.4, washed twice with PBST pH 7.4 and re-suspended in 15% glycerol containing PBS buffer pH 7.4 concentrating it at the same time 100 fold. The cells were stored at 20 C. For further use in binding or lytic activity assays the cells were thaw, washed with PBS pH 7.4 and diluted to an OD595 of 10.05. In standard lytic activity assays protein samples were diluted to equimolar amounts and distributed in transparent 96-well tissue culture test plates (SPL life sciences, Pocheon, Korea). Substrate cells were added to a final volume and drop in optical density at 595 nm (OD595 nm) were recorded for about 1 hour at 37 C.

(14) Decrease in optical density at 595 nm (OD595) was measured using a Victor3 1420 Multilabel Counter instrument (Perkin Elmer) during 1 hour. Plates were shaken vigorously for 1 second (double orbit, 0.1 mm diameter) after every single read out. As positive control served N-terminal 6His tagged Lysostaphin (HLST), commercially available Lysostaphin (recombinant, E. coli originated, Sigma). As negative control we applied MilliQ water.

(15) Minimal Inhibitory Concentration (MIC) Assay

(16) Two-fold serial dilutions (2000 nM to 4 nM) of endolysin in casein peptone soybean flour peptone broth (CASO broth (Carl Roth, Germany)) were distributed in sterile crystal clear 96-well plates at 100 l/well. S. aureus Newbold were grown in CASO broth to mid log phase (OD600 nm-0.5) and diluted with fresh CASO broth to 1E+6 cfu/ml. The cells were then distributed in the endolysin containing wells resulting in endolysin concentrations of 1000 nM to 2 nM and 10E+5 cfu/well. The 96-well plates were covered with the lid and incubated for 20 hours at 30 C. Images were takes using a gel scanner. As positive control served CASO broth without endolysin, and as negative control CASO broth without S. aureus cells was used.

(17) Results

(18) Determination of Specific Activity of an Endolysin Polypeptide According to the Invention by Minimal Inhibitory Concentration Analysis

(19) The specific activity of XZ.700, an endolysin polypeptide with an amino acid sequence according to SEQ ID NO: 2 was compared to that of SA.100, a reference endolysin polypeptide with an amino acid sequence according to SEQ ID NO: 1. The results are depicted in FIG. 1. MIC values were obtained by exposure of 2-3E+5 cfu S. aureus Newbold to serial dilutions of Staphefekt in a 200 l format. The image was taken after 20 h incubation in CASO medium. The MIC value of SA.100 was 62.5 nM and MIC value of XZ.700 was 15.6 nM in three independent assays; i.e. the MIC value of XZ.700 is four-fold lower that of SA.100, indicative of a four-fold higher specific activity of XZ.700.

(20) Determination of Thermal Stability and Specific Activity of an Endolysin Polypeptide According to the Invention by Turbidity Assay

(21) The thermal stability and specific activity of XZ.700, an endolysin polypeptide with an amino acid sequence according to SEQ ID NO: 2 were compared to those of SA.100, a reference endolysin polypeptide with an amino acid sequence according to SEQ ID NO: 1. In brief, 200 mM of SA.100 and XZ.700 were subjected to 10 minutes heat exposure (X-axis) followed by cooling on ice. The relative activity in view of SA.100 at 20 degrees Celsius was subsequently determined by turbidity lysis assay. It can clearly be observed in FIG. 2 that the activity of XZ.700 is somewhat lower than SA.100 from about 55 degrees Celsius and higher, whereas the activity of XZ.700 is significantly higher than SA.100 up to about 55 degrees Celsius. At room temperature, the activity of ZX.700 is about 70% higher than SA.100.

(22) Specific activity and thermal stability were also determined using a kinetic assay. XZ.700 and SA.100 at concentrations of 200 nM were heat exposed between 42 degrees Celsius and 72 degrees Celsius for 10 minutes in PBS buffer in a gradient thermocycler. After subsequent cooling on ice, lysis kinetics in standard dynamic turbidity reduction assays were recorded at 100 nM protein concentrations against S. aureus SA.113 in PBS buffer pH 7.4. The lysis curves are depicted in FIG. 3 and show optical density reductions (Y-axis, initial OD600 nm1) over time (X-axis, duration 1 h). It can clearly be observed that up to 60 degrees Celsius ZX.700 has a significantly steeper curve than SA.100, indicating higher specific activity.

(23) Immunogenicity Prediction of an Endolysin Polypeptide According to the Invention.

(24) Immunogenicity predictions were performed on the XZ.700 and SA.100 polypeptide sequences (SEQ ID NO: 1 and SEQ ID NO: 2, respectively) using the tools.immuneepitope.org/bcell/webpage with parameters: centre position 4, window size 7, and threshold 1.0. The results are depicted in Table 1. It is clear that the immunogenic peptide fragment VKELKHIYSNH (position 197-207 in SA.100) is not present in XZ.700.

(25) Altogether, in this non-limiting example, it was demonstrated that endolysin polypeptide according to the invention XZ.700 has a higher specific activity and lower immunogenicity than prior art endolysin polypeptide SA.100.

(26) TABLE-US-00001 TABLE1 Kolaskar&TongaonkarImmunogenicitypredictionofpeptidespresentin StaphefektSA.100(left)andStaphefektXZ.700(right).

(27) TABLE-US-00002 SEQUENCES SEQIDNO:1 MAATHEHSAQWLNNYKKGYGYGPYPLGINGGMHYGVDFFMNIGTPVK AISSGKIVEAGWSNYGGGNQIGLIENDGVHRQWYMHLSKYNVKVGDY VKAGQIIGWSGSTGYSTAPHLHFQRMVNSFSNSTAQDPMPFLKSAGY GKAGGTVTPTPNTGELLRPKDAKKDEKSQVCSGLAMEKYDITNLNAK QDKSKNGSVKELKHIYSNHIKGNKITAPKPSIQGVVIHNDYGSMTPS QYLPWLYARENNGTHVNGWASVYANRNEVLWYHPTDYVEWHCGNQWA NANLIGFEVCESYPGRISDKLFLENEEATLKVAADVMKSYGLPVNRN TVRLHNEFFGTSCPHRSWDLHVGKGEPYTTTNINKMKDYFIKRIKHY YDGGKLEVSKAATIKQSDVKQEVKKQEAKQIVKATDWKQNKDGIWYK AEHASFTVTAPEGIITRYKGPWTGHPQAGVLQKGQTIKYDEVQKFDG HVWVSWETFEGETVYMPVRTWDAKTGKVGKLWGEIK SEQIDNO:2 MAATHEHSAQWLNNYKKGYGYGPYPLGINGGMHYGVDFFMNIGTPVK AISSGKIVEAGWSNYGGGNQIGLIENDGVHRQWYMHLSKYNVKVGDY VKAGQIIGWSGSTGYSTAPHLHFQRMVNSFSNSTAQDPMPFLKSAGY GKAGGTVTPTPNTGLKHIYSNHIKGNKITAPKPSIQGVVIHNDYGSM TPSQYLPWLYARENNGTHVNGWASVYANRNEVLWYHPTDYVEWHCGN QWANANLIGFEVCESYPGRISDKLFLENEEATLKVAADVMKSYGLPV NRNTVRLHNEFFGTSCPHRSWDLHVGKGEPYTTTNINKMKDYFIKRI KHYYDGGKLEVSKAATIKQSDVKQEVKKQEAKQIVKATDWKQNKDGI WYKAEHASFTVTAPEGIITRYKGPWTGHPQAGVLQKGQTIKYDEVQK FDGHVWVSWETFEGETVYMPVRTWDAKTGKVGKLWGEIK