Patent Application
20050287146
The present invention relates to the use of an immunoglobulin product obtained from purified donor plasma containing high antibody titers to MSCRAMM proteins ClfA and SdrG in the prevention and treatment of infections from Candida yeast, including Candida species late-onset sepsis and other Candida systemic infections.
Low birth weight (LBW) infants comprise 1.4% of all births in the United States, and over 57,000 infants per year are very low birth weight (VLBW) defined as <1,500 gm.1 Advances in medical care provided by neonatal intensive care units (NICUs) throughout the country have dramatically improved the survival for these premature infants. One of the costs of prolonged survival among premature infants is an increased frequency of complications, especially nosocomial (hospital acquired) infections. In one study, the overall rate of late-onset infection among VLBW infants (“VLBWI”) 501 to 1,500 gm was 16% but the rate increased with decreasing birth weight and gestational age, rising rapidly to 40% among the smallest infants (500 to 600 gm).2
In a study of infants 401 to 1,500 gm birth weight admitted to the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network centers, the rate of infection among infants of birth weight 401 to 1500 g after day three of life was 21%, essentially unchanged from previous estimates.3 In fact, late-onset sepsis has become the most common cause of death among premature infants after the third day of life.4
Reasons for the increased risk of infection among neonates include iatrogenic factors such as the use of vascular catheters, but also host factors. Immunoglobulin G (IgG), a critical part of immunity against bacterial pathogens, is transferred from mother to infant selectively through the placenta beginning at 8 to 10 weeks of gestation and accelerating during the last trimester. Infants born prior to 32 weeks gestation are relatively deficient in IgG. In vitro studies have demonstrated the importance of IgG directed against staphylococci for host defense.5-7 Low levels of IgG at birth is an identified risk factor for late-onset sepsis in LBW infants.2
The predominant organism for late-onset sepsis in recent studies is S. epidermidis and similar species collectively referred to as coagulase-negative staphylococci (CoNS).2, 8-10 While the mortality attributed specifically to CoNS is considered to be less than that of other organisms, the public health implications of CoNS infections are significant. Widespread use of antibiotics, especially vancomycin, for the treatment of suspected or proven nosocomial infection applies selective pressure for the emergence of antibiotic-resistant bacteria in intensive care units. Stoll et al. remarked “It is alarming that 44% of infants in this cohort (whether or not they had documented CoNS infection) were treated with vancomycin.”3 Vancomycin resistant strains of CoNS have been rarely reported, but the possibility of wider emergence of such strains would be disastrous.11, 12
In addition to staphylococcal late-onset sepsis, fungal sepsis in VLBWI is significant medical problem. In a prospective study by Conner et al., among 1,111 VLBWI, 5% developed fungal sepsis within the first 28 days of life. The predominant fungal pathogen was Candida species of yeast (82%). In a similar study, the mortality rate associated with Candida species late-onset sepsis in VLBWI was 43.9%. However, despite the very severe pathological conditions caused by Candida-related infections, there have been very few effective treatment regimens against these extremely dangerous infections. Even further, it has not heretofore been possible to develop a treatment regimen which can address both infections caused by staphylococcal organisms and at the same time be effective against Candida-related infections.
It is therefore imperative that new strategies be developed which can address the critical problem of hospital-acquired infections in premature infants, and in particular, it is highly desirable to develop treatments and compositions which can be useful in treating and preventing Candida-related infections and at the same time be useful in inhibiting the progression of staphylococcal infections.
It is thus an object of the present invention to provide compositions and methods for diagnosing, treating, and/or preventing infections caused by Candida species of yeast.
It is thus another object of the present invention to provide compositions and methods which are particularly useful in fighting late-onset sepsis in neonates and which can inhibit the growth and severity of infections caused by Candida species of yeast and staphylococcal infections at the same time.
It is still further an object of the present invention to provide donor selected or donor stimulated immunoglobulin compositions that can be effective in identifying and isolating surface antigens from Candida albicans and which can be useful in treating or preventing Candida-related diseases.
These and other objects are provided by the present invention wherein a donor immunoglobulin composition having high titers of antibodies to the proteins ClfA from S. aureus and SdrG from S. epidermidis can be administered to a patient in need of treatment for or protection against an infection caused by yeast of the species Candida such as Candidiasis, and this composition will be effective in inhibiting the yeast and enabling the effective treatment or prevention of the Candida infection. In addition, in another embodiment of the invention, an immunoglobulin composition of the invention can be prepared which includes a high titer to antigen from a Candida species yeast such as Candida albicans, and this composition can also be used effectively to inhibit Candidial yeast and thus treat or prevent a Candidial infection. Further, because of its ability to recognize surface proteins in Candida, the immunoglobulin compositions of the present invention will also be useful in identifying and isolating surface proteins from Candida yeast and in diagnosing Candida infections. The present compositions and methods will thus be particularly effective in treating or preventing late-onset sepsis in low birth weight neonates.
These and other objects of the present invention are obtained through the compositions and methods as set forth in the detailed description of the invention provided hereinbelow.
In accordance with the present invention, there is provided a method for inhibiting infections caused by Candidial yeast, and this method comprises administering an effective amount of a purified human donor plasma containing a higher than normal antibody titer to the adhesin ClfA (clumping factor A) from Staphylococcus aureus and a higher than normal antibody titer to the adhesin SdrG, an Sdr (serine-aspartate repeat) protein from Staphylococcus epidermidis. This donor plasma can be obtained using either the selection approach or the stimulation approach as set forth as disclosed in U.S. Pat. No. 6,692,739, incorporated herein by reference. The use of either method results in immunoglobulin compositions that have an antibody titer to each of the selected adhesins in an amount that is higher than that found in pooled intravenous immunoglobulin obtained from unselected donors. As disclosed in U.S. Pat. No. 6,692,739, the desired immunoglobulin compositions can be obtained through the selection of donors identified as having high titers to the desired adhesins of interest or through the stimulation of donors by vaccination with the desired adhesin or adhesins. In accordance with the present invention, these donor immunoglobulin compositions have now unexpectedly have been discovered to recognize surface proteins from Candida species of yeast and can thus be used in methods of inhibiting, diagnosing, treating or preventing infection from Candidial yeast, as set forth in more detail below.
As indicated above, the present method comprises the administration of an effective amount of a donor immunoglobulin composition as described above to a patient in need thereof so as to inhibit, treat or prevent an infection from a Candida yeast such as Candida albicans. By effective amount, as would be recognized by one skilled in the art, is meant that amount which will be effective in inhibiting infection from Candida yeast so as to treat or prevent a condition caused by this yeast species, and one would readily recognize that this amount will vary greatly depending on the nature of the infection and the condition of a patient. Accordingly, an “effective amount” of the immunoglobulin compositions in accordance with the invention generally comprises a nontoxic but sufficient amount of the composition or effective agent therein such that the desired prophylactic or therapeutic effect is produced. Thus, the exact amount of the immunoglobulin composition that is required will vary from subject to subject, depending on the species, age, and general condition of the subject, the severity of the condition being treated, the particular carrier or adjuvant if being used, its mode of administration, and the like. Accordingly, the “effective amount” of any particular donor composition will vary based on the particular circumstances, and an appropriate effective amount may be determined in each case of application by one of ordinary skill in the art using only routine skills. The exact amount administered to patients will thus be adjusted to suit the individual to whom the composition is administered and will vary with age, weight and metabolism of the individual. The compositions may additionally contain stabilizers or pharmaceutically acceptable preservatives, such as thimerosal(ethyl(2-mercaptobenzoate-S)mercury sodium salt) (Sigma Chemical Company, St. Louis, Mo.).
In accordance with the invention, purified donor immunoglobulin compositions are obtained in accordance with any of the methods described in U.S. Pat. No. 6,692,739, and such compositions will contain a higher than normal antibody titer to the Clumping Factor A (ClfA) protein from S. aureus, as further described, e.g., in U.S. Pat. Nos. 6,008,341 and 6,177,084, incorporated herein by reference, and the serine-aspartate dipeptide repeat G (SdrG) protein from S. epidermidis as described in more detail in U.S. Pat. No. 6,635,473, incorporated herein by reference. One such formulation is INH-A21 which has been obtained from donor-selected staphylococcal human immune globulin and which has previously been shown to be useful for the prevention and treatment of staphylococcal infections in low birth weight (LBW) and very low birth weight (VLBW) infants. In the preferred embodiment, prior to administration to patients in order to inhibit, treat or prevent a Candidial infection, INH-A21 is preferably nanofiltered, and solvent-detergent treated to remove and inactivate viruses. It is generally desired that formulations in accordance with the invention such as INH-A21 contain at least 5% IgG in a suitable sodium chloride concentration and preferably does not contain sucrose or preservatives. In a preferred form, INH-A21 contains IgG, 5% weight per volume of which >95% is monomer. Other classes of immune globulin are present in low amounts, with IgM <0.5% and IgA <0.5%. The range of IgG subclass composition is similar to that found in normal human plasma and is within the following ranges: IgG1, 50-75%; IgG2, 20-40%; IgG3, 1-10%; and IgG4 less than 5%.
In the particularly preferred embodiment, plasma used in the production of INH-A21 is derived from donors specifically selected for elevated levels of antibodies against the staphylococcal fibrinogen binding proteins, SdrG and ClfA. These surface expressed molecules belong to a family of proteins called Microbial Surface Components Recognizing Adhesive Matrix Molecules (MSCRAMM®). SdrG and ClfA are found on the surface of >95% of strains of Staphylococcus epidermidis and Staphylococcus aureus, respectively. These antigens play an important role in the adherence of bacteria to host tissues, which is the initiating step in establishment of infection. It has now been demonstrated that in addition to higher titers of antibodies to the staphylococcal adhesins described above, the composition INH-A21 in accordance with the present invention also contains elevated levels of antibodies to antigens expressed by Candida species. This is a very important scientific finding with significant clinical ramifications, since Candida infections are often difficult to detect and treat. Accordingly, formulations in accordance with the present invention such as INH-A21 can be useful for the prevention and treatment of Candida infections, particularly in low and very-low birth weight infants. As indicated above, in the preferred method of the invention, the method comprises administering to a patient in need thereof, such as a low or very-low birth weight infant, a purified immunoglobulin composition with high titers of antibodies to ClfA and SdrG, and this composition is administered in an amount and for a time effective to achieve the therapeutic treatment goals, namely inhibition, treatment or prevention of a Candidial infection.
In another embodiment of the present invention, plasma used in the production of a purified immunoglobulin composition may be prepared by screening for donors which have a high titer against an antigen from a Candida yeast such as Candida albicans, and preparing a purified immunoglobulin composition in the manner set forth above which in this case will have an antibody titer to an antigen from Candida which is higher than that which is found in pooled intravenous immunoglobulin obtained from unselected donors. In particular, immunoglobulin compositions may be provided in accordance with the invention which have a higher than normal titer to a surface antigen from a Candida yeast such as Candida albicans. In accordance with the present invention, these antigens can be selected from the group consisting of the Als proteins, enolase, INO1-myo-inositol phosphate synthase, glucose-6-phosphate dehydrogenase, methionine synthase, ADH1/alcohol dehydrogenase; FBA1/fructose-biphosphate aldolase and the homologue of S. cerevisiae HEM13 which is involved in HEME synthesis. As described above, the preferred method of treating patients such as low and very-low birth weight infants is by administering to a patient in need thereof the purified immunoglobulin composition with high titers of antibodies to Candida antigens in an amount and for a time effective to achieve the therapeutic treatment goals, namely inhibition, treatment or prevention of a Candidial infection.
In light of the fact that the immunoglobulin compositions of the invention can recognize a series of Candidial antigens, in another embodiment of the present invention, a method of diagnosing a Candidial infection is provided which comprises introducing an immunoglobulin composition having an antibody titer to an S. aureus Clumping Factor A (ClfA) protein in combination with an antibody titer to an S. epidermidis serine-aspartate repeat G (SdrG) protein in an amount higher that that found in pooled intravenous immunoglobulin obtained from unselected donors to a sample suspected of containing antigens from Candida yeast for a time sufficient to allow the Candida antigens to bind to the antibodies in the immunoglobulin composition, and diagnosing a Candidial infection by determining if Candida antigens in the sample have bound to the antibodies in the immunoglobulin composition.
The property of the immunoglobulin compositions of the invention to recognize Candidial surface antigens also makes it possible to identify these surface antigens in accordance with the invention. For example, as shown in
One set of antigens from Candida albicans that is recognized by the immunoglobulin compositions of the present invention is the group of Als proteins whose sequences are shown in
Accordingly, in another embodiment of the present invention, a method of identifying Candidial surface antigens is provided which comprises obtaining a cell wall extract from a culture of Candida yeast cells, introducing into the extract an immunoglobulin composition having an antibody titer to an S. aureus Clumping Factor A (ClfA) protein in combination with an antibody titer to an S. epidermidis serine-aspartate repeat G (SdrG) protein in an amount higher that that found in pooled intravenous immunoglobulin obtained from unselected donors, and detecting Candida antigens that have bound to the antibodies in the immunoglobulin composition. As shown in
In still another aspect of the present invention, it has been observed that antibodies (both polyclonal and monoclonal) raised against the MSCRAMM ClfA also are capable of binding to an antigen from Candida albicans, namely an Als protein (see
In short, the high titer immunoglobulin compositions of the present invention which recognize and which are capable of binding to surface antigens on Candida albicans can be useful in the diagnosis, inhibition, treatment and prevention of infections from Candidial yeast. These compositions will thus also be capable of treating staphylococcal infections at the same time, and their application will be particularly useful in infectious conditions such as late-onset sepsis which affects low and very-low weight newborn infants.
The following examples are provided which exemplify aspects of the preferred embodiments of the present invention and which additional details regarding making and using the invention, and detail the usefulness of the invention in providing methods for treating or preventing Candida species-related infections. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventors to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.
Source Plasma
Source Plasma is collected according to the method as disclosed in U.S. Pat. No. 6,692,739, incorporated herein by reference. Source Plasma is obtained from normal, non-immunized donors meeting FDA requirements and iQPP standards for Source Plasma donation. Source Plasma units undergo viral marker testing in accordance with current FDA 21 CFR 640 requirements, that is, the units must be nonreactive or negative for the following:
Each plasma unit must also contain an alanine aminotransferase (ALT) level less than twice the upper baseline limit of normal.
Plasma Screening for Antibodies Recognizing MSCRAMM® Proteins ClfA and SdrG
Samples from plasma donors are screened for elevated levels of antibodies to ClfA and SdrG. The screening processes is described in U.S. Pat. No. 6,692,739, incorporated herein be reference. ClfA is described further in U.S. Pat. Nos. 6,008,341 and 6,177,084, incorporated herein by reference. The SdrG protein is described in more detail in U.S. Pat. No. 6,635,473, incorporated herein by reference. Antibody levels specific for ClfA and SdrG in normal IGIV products were previously established by testing commercially available preparations of IGIV and creating a standard reference.
Measurement of Anti-ClfA Titers
Human plasma samples are screened by Inhibitex using an ELISA procedure to assess anti-ClfA (Clf40; amino acids 40-559) MSCRAMM® IgG concentration. Costar plates (VWR# 29442-314) or the equivalent are incubated with a 1 μg/mL Clf40 solution for 12 to 24 hours at 2-8° C. The plates are washed with a solution of PBS and Tween 20, and incubated for 2 to 4 hours at room temperature with a 1% solution of BSA. Following the incubation, plates are washed and the coated wells are overlaid with a 1:200 dilution of each sample to be tested, a Clf40 Calibration Standard (Staphgam MS501, obtained from Cangene Corp., Winnipeg, Canada), or a quality control sample. Plates are incubated for 55 to 65 minutes at room temperature and washed. The plates are incubated for 55 to 65 minutes at room temperature with alkaline phosphatase conjugated goat anti-human IgG (Rockland, Gilbertsville, Pa.) or equivalent, then washed. The plates are subsequently developed for 45 to 55 minutes at room temperature with a 1 mg/mL solution of p-nitrophenylphosphate, disodium (Sigma, St. Louis, Mo.) or the equivalent prepared in diethanolamine substrate buffer (Pierce, Rockford, Ill.). Following plate development, 50 μL of 2N NaOH (LabChem Inc., Pittsburgh, Pa.) is added to each well. Plates are read at 405 nm with a Spectra MAX 250 Bio-Assay plate reader (Molecular Devices Corp., Sunnyvale, Calif.) or equivalent for the presence of anti-ClfA antibodies.
Measurement of Anti-SdrG Titers
Human plasma samples are screened by Inhibitex using an ELISA procedure to assess anti-SdrG (SdrG; amino acids 50-597) MSCRAMM® IgG concentration. Costar plates (VWR# 29442-314) or the equivalent are incubated With a 1 μg/mL SdrG solution for 12 to 24 hours at 2-8° C. The plates are washed with a solution of PBS and Tween 20, and incubated for 2 to 4 hours at room temperature with a 1% solution of BSA. Following the incubation, plates are washed and the coated wells are overlaid with a 1:200 dilution of each sample to be tested, a SdrG Calibration Standard (INH-A21 Inhibitex, Alpharetta, Ga.), or a quality control sample. Plates are incubated for 55 to 65 minutes at room temperature and washed. The plates are incubated for 55 to 65 minutes at room temperature with alkaline phosphatase conjugated goat anti-human IgG (Rockland, Gilbertsville, Pa.).or equivalent then washed. The plates are subsequently developed for 45 to 55 minutes at room temperature with a 1.0 mg/mL solution of p-nitrophenylphosphate disodium (Sigma, St. Louis, Mo.) or equivalent prepared in diethanolamine substrate buffer (Pierce, Rockford, Ill.). Following plate development, 50 μL of 2N NaOH (LabChem Inc., Pittsburgh, Pa.) is added to each well. Plates are read at 405 nm with a Spectra MAX 250 Bio-Assay plate reader (Molecular Devices Corp., Sunnyvale, Calif.) or equivalent for the presence of anti-SdrG antibodies.
The INH-A21 preparation, containing Candida specific antibodies, and prepared as described above was used in both preclinical animal models and a Phase II clinical trial and was shown to be effective in preventing infections caused by Candida species microorganisms, as shown in the following examples:
Flow Cytometric Analysis of Candida Cell Surface Antigens
Candida Preparation—Overnight cultures were prepared from a few colonies of each Candida strain picked with an inoculum loop off a streak plate that had been prepared from a frozen stock of the strain. The colonies were used to inoculate 10 ml YPD broth cultures and the cultures were grown at 30° C. with 250 rpm rotation. The following day 4 hr cultures were prepared by mixing 1 ml of overnight culture with 9 ml of fresh YPD broth and growing cultures at 30° C. with 250 rpm rotation.
All cultures were stored on ice after growth period. The cultures were washed twice in cold 1× PBS (10 ml per wash). The cultures was adjusted to an OD600 of 1.5 to 2.0 in 1× PBS. 1 ml of the culture at this concentration were retained for blocking.
Blocking—0.1 mg of purified rabbit IgG was mixed with cells in 1× PBS by vortex and incubated for 30 minutes on ice. At 15 minute intervals each strain was vortexed during each incubation.
Antibody Preparation—A 1 mg/ml dilution of INH-A21 in PBSA (2.5% BSA in 1× PBS) was prepared. In addition, a 0.1 mg/ml INH-A21 dilution followed by ten additional 1:2 dilutions were prepared. Solutions were stored on ice.
Primary Ab Incubation—The assay was performed in Bio Rad titertubes for ease in handling. Using a multi-channel pipette, 20 μl of blocked Candida cells were added each tube. 0.5 ml of INH-A21 dilution was then added to the designated tubes. All tubes were vortexed and incubated on ice for 30 minutes. Cells were vortexed at 15 min. intervals. Following the incubation each tube was centrifuged in plate rotor at 3000 RPM for 10 minutes. The supernatant was decanted by hand for each tube. The Candida cells were washed twice in cold PBSA.
Secondary PE F(ab′)2 Incubation—Each tube received 0.5 ml of a 1:200 dilution of PE conjugated goat F(ab′)2 anti-human IgG(H+L) secondary antibody. The Candida cells were resuspended and mixed by vortexing. The tubes were incubated on ice for 30 minutes vortexing twice at ten minute intervals. Following this incubation the Candida cells were washed twice with a final resuspension in PBSA. The tubes were stored on ice until FACS analysis.
FACS Analysis—Each titertube was transferred to a 12×75 mm flow tube. The FL-2 detector was adjusted so that the isotype control PE emission was detected in the first decade of the FL-2 histogram scale (
Cell cultures. Candida albicans s.c 5314 cells were cultured in YPD at 30° C. and used as whole yeast cell to absorb INH-A21 (Lots 802546B & 803718) or normal immunoglobulin(Gammagard S/D, Lot 02129AX11, Baxter Healthcare & Gamma-PIV, Lot X517911, Aventis Behring). The cell pellet from the YPD culture was re-suspended in Lee's medium (Ref) and cultured for 6 hrs at 30° C. Cells from the Lee's medium were re-suspended in sterile water and incubated at 4° C. for 3 days for “starvation”. After the starvation, cells were cultured in Lee's medium at 37° C. for 6 hrs. to induce the formation of hyphae.
Preparation of cell wall extracts. The yeast cells were treated in 20 mM phosphate buffer (pH 7.2) containing 1M sorbitol, 20 mM DTT, complete proteinase inhibitor cocktail, and 10 mg/ml zymolyase 20-T for 1 hr at 37° C. After the treatment, the tube was spun at top speed in a benchtop microcentrifuge for 15 min. and the supernatant was collected.
Absorption of immunoglobulins by the whole yeast cells. About 25 mg of each immunoglobulin sample was mixed with 0.1 ml pellet of the yeast cell and incubated at 4° C. for 6 hrs. The yeast cells were removed by centrifugation at top for 10 min. in a benchtop microcentrifuge and the immunoglobulins were collected.
2-D gel electrophoresis and Western blotting. Cell wall extracts from the hyphae of Candida albicans s.c. 5314 were separated by 2-D gel electrophoresis in the ZOOM IPGRunner System (Invitrogen) according to the instruction. The proteins were transferred onto PVDF membrane and incubated with the yeast-absorbed immunoglobulins. The mouse anti-human IgG conjugated to HRP was used as secondary antibody and the protein spots were detected with the Supersignal pico west substrate (PIRECE) (
To further identify the antigens that are recognized preferentially by INH-A21, cell wall extracts from the Candida albicans s.c. 5314 were separated by 2-D gel electrophoresis in the ZOOM IPGRunner System (Invitrogen) according to the instruction. Duplicate 2D gels were run using the cell wall extracts. One gel was transferred to nitrocellulose and probed as described in Example 3 then visualized on Kodak BioMax XAR film. The second gel was stained with colloidal Coomassie Blue to visualize the bands. In order to excise the band corresponding to individual Western spots, a second film was produced. The immunoreactive bands of interest were cut out of this film and overlaid onto the stained gel. Using the hollowed out film as a guide, a sterile, disposable scalpel blade was used to excise the stained band of interest. The gel slice was placed in a clear, dry microfuge tube that was previously rinsed with HPLC grade water and HPLC grade methanol. The gel slice was than washed twice for 2 minutes each with 0.5 mL of 50% acetonitrile in HPLC grade water. After removing the excess liquid, the moist gel slice was stored at −80° C. until analyzed. Additionally, an equivalent unstained area of the gel was excised and stored in the same manner to control for chemical and generalized nonspecific protein background noise during analysis. The excised band was homogenized in an aqueous buffer and subjected to proteolysis using trypsin. The proteolyzed sample was then filtered and analyzed by microcapillary reverse-phase HPLC nano-spray tandem mass spectrometry on a Finnigan LCQ DECA XP Plus quadrupole ion trap mass spectrometer. This instrument configuration is capable of acquiring individual sequence (MS/MS) spectra on-line at high sensitivity (<<1 femtomole) for multiple peptides in the chromatographic run. These MS/MS spectra are correlated with known sequences using the algorithm Sequest developed at the University of Washington (16), and by programs developed at Harvard (17). The MS/MS peptide sequences were reviewed by a scientist for consensus with known proteins and the results manually confirmed for fidelity. The proteins identified from the 2D gel were Als1 (spot 2), Als3 (spot 3), and enolase (spot 1).
More information concerning the Als proteins and antibodies thereto is disclosed in U.S. patent application Pub. No. 2003/0124134, said application incorporated herein by reference.
Mice were used in preclinical studies of INH-A21 to explore the prophylactic activity of INH-A21 an in vivo model of Candida mediated mortality. To demonstrate biologic activity conferred by the selection of antibodies against SdrG and ClfA, with cross-reactivity against Candida antigens, Candida albicans was used as the infecting organism in this model.
Mice were administered INH-A21 or a non-donor selected or normal IGIV (Panglobulin®, American Red Cross Plasma Services). INH-A21 or Panglobulin® was given as a single dose of 12.5 mg/kg. Eighteen hours after dosing, animals were challenged intravenously with Candida albicans. Efficacy was measured as survival at 14 days following the fungal challenge. These data demonstrate that INH-A21 protects against IV challenge with C. albicans (
With the exception of elevated levels of antibodies to ClfA, SdrG, and Candidial antigens, INH-A21 is a human IGIV manufactured by methods common to other commercially available IGIV products. A review of the efficacy of prior clinical trials in premature infants using these products is appropriate to evaluate the potential efficacy in this population. In a study reported by Baker et al., 287 infants (birth weight 500 to 1750 grams) received 1,125 infusion of IGIV, and 297 infants received 1,163 infusions of placebo.13 There was not a reduction in the incidence of late-onset fungal sepsis between the IVIG group and placebo. Weisman et al. randomized 372 infants (birth weight 560 to 2000 grams) to receive IGIV and 381 to receive albumin.14 There was not a reduction in the incidence of late-onset fungal sepsis between the IVIG group and placebo. In a study by Fanaroff et al., 1204 infants received IGIV (n=1204), while control infants (n=1212) received albumin, or during a second phase of the study, no infusion.15 There was not a reduction in the incidence of late-onset fungal sepsis between the IVIG group and placebo.
INH-A21 Reduces Candida Infection in VLBW Infants.
In a Phase II, placebo-controlled, double-blind study in VLBWI (500-1,250 g), prophylactic administration of INH-A21 (750 mg/kg) was shown to reduce the incidence of late-onset candidial sepsis by 67% when compared to placebo (Table 1). In addition to reducing the incidence of candidemia, INH-A21 also reduced the incidence of S. aureus infection by 63%, and all-cause mortality by 36%. Despite the numerous clinical trials conducted with immune globulins in neonates, the magnitude in the reduction of candidial infection demonstrated with INH-A21 in this clinical trial has not been seen previously.
Antibodies generated against a previously discovered family of structurally related surface proteins (MSCRAMMs) on Gram-positive bacteria have been shown to be useful as preventive and therapeutic agents (Hall et al., 2003. Infect. Immun. 71, 6864-6870). We have recently recognized that a previously described family of proteins on the surface of Candida albicans, the Als proteins, is structurally and immunologically similar to the bacterial MSCRAMMs. Like MSCRAMMs, the Als cell-surface proteins have a multi-domain structure. Each Als protein has a very well conserved N-terminal domain followed by a central domain formed by tandemly repeated motifs and a serine-threonine-rich C-terminal domain that can be variable in length. The C-terminal residues of the mature Als proteins are covalently linked to the C. albicans cell wall by β1, 6-glucan chains. Similarity of the Als N-terminal domains to the sequence of Saccharomyces cerevisiae α-agglutinin and Staphylococcus aureus ClfA, both cell-surface adhesins, suggests that the Als proteins are adhesins, mediating the C. albicans attachment to host surfaces.
The use of polyclonal or monoclonal antibodies reacting with Als proteins constitutes a new potential strategy for the prevention and treatment of infections caused by C. albicans and related organisms. An analogous strategy, using antibodies targeted to the MSCRAMM ClfA, has been effective in animal models for the treatment and prevention of infections caused by S. aureus. The overall structural features of the Als proteins are strikingly similar to those found in bacterial MSCRAMMs. As shown on
One of the most surprising and unexpected observations that was made is that antibodies (both polyclonal and monoclonal) raised against an MSCRAMM (ClfA in this example) can recognize a recombinant version of an Als protein (
We have cloned the regions of the Als5 and Als7 genes predicted to encode the N-terminal regions homologous to the S. aureus ClfA ligand-binding domain. These constructs encompass amino acids 22-371 in Als5 and 23-372 in Als7. Initially, these constructs were expressed in E. coli, however, to promote native protein folding, they will be overexpressed in a yeast heterologous host, Pichia pastoris.
In addition, we have performed experiments showing that the recombinant Als5 N-terminal domain binds to extracellular matrix proteins such as fibrinogen, fibronectin and collagen Type I (
Other aspects of the present experiments include the overexpression of Als5 and Als7 (the most and least conserved sequences in the Als family), and the generation of both monoclonal and polyclonal antibodies against these recombinant proteins. In accordance with the invention, antibodies to Als proteins such as Als5 and Als7 will be useful in the inhibition of C. albicans and the treatment and prevention of C. albicans infections.
The present invention is thus particularly useful because of the fact that since infections caused by C. albicans and related organisms are difficult to diagnose, these organisms can survive in the host without causing detectable disease symptoms, or can cause symptoms that vary in site and severity. C. albicans has numerous mechanisms to adapt in the host, including differential gene expression that leads to switching between two morphologies: the blastospore (yeast form) and filamentous forms (hyphae and pseudohyphae). The ability to change from a blastospore to a filamentous form is a key virulence factor, since it has been shown that the hyphae and pseudohyphae are the virulent, invasive forms that cause disease (Hoyer L. L. et al., 1995. Mol. Microbiol 15: 39-54). The identification and characterization of hyphae-surface proteins involved in virulence, such as the Als proteins, enables immunotherapeutic strategies that are superior to existing antifungal agents. While existing antifungal agents are microbicidal for Candida in vitro, the attributable mortality for candidemia is 38%, even during treatment with antifungal agents such as amphotericin B. Therefore, either passive or active immunotherapy to treat or prevent disseminated candidiasis in accordance with the invention will be a promising complement or alternative to standard antifungal therapy.
The existing patent US2003/0124134 A1, incorporated herein by reference, describes pharmaceutical compositions and methods to vaccinate against candidiasis using Als1 N-terminal region (amino acids 17-432) as an immunogen. However, in accordance with the present invention, the described constructs for Als5(22-371) and Als7(23-372) may be used as immunogens, and this will likely give a more effective preparation because:
(a) they represent a structurally defined region homologous to those present in bacterial proteins of similar function (
(b) they bind to extracellular matrix proteins (
(c) antibodies present in Veronate® and Aurexis® recognize them (
As referred to in this application, Veronate® refers to a donor selected or donor-stimulation human immunoglobulin composition such as described in U.S. Pat. No. 6,692,739, incorporated herein by reference, and Aurexis® refers to a composition comprising a monoclonal antibody to ClfA as disclosed in co-pending U.S. patent Ser. No. 10/156,052, published as U.S. patent application Pub. 2003/0099656, incorporated herein by reference.
The advantage of using the Als5 and Als7 N-terminal regions and antibodies generated against them as a treatment strategy for the prevention of C. albicans infections is that the humanized antibodies are very effective and do not cause secondary adverse reactions. This is a significant improvement over the antifungal therapies that can be toxic to the host at high or prolonged doses.
The following references referred to above are hereby incorporated into the above specification as if set forth in their entirety:
This application claims the benefit of U.S. Provisional Applications Ser. No. 60/566,082, filed Apr. 29, 2004, Ser. No. 60/561,540, filed Apr. 13, 2004, and Ser. No. 60/530,654, filed Dec. 19, 2003, all of said applications incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60566082 | Apr 2004 | US | |
| 60561540 | Apr 2004 | US | |
| 60530654 | Dec 2003 | US |
