Posts Tagged ‘bayhill therapeutics’

DNA Vaccination to Multiple Sclerosis Depends on Interferon Beta

Sunday, June 28th, 2009

We previously discussed that interferon beta therapy is associated with upregulation of T regulatory cell (Treg) activity in patients with multiple sclerosis, and that this may be one of the mechanisms by which it mediates its therapeutic effect.  We also discussed the point that current methods of measuring Treg activity are somewhat limited in that they do not measure the specific Treg that protect the body against the specific autoreactive T cells that are attacking the myelin, but measure activity of all the Tregs as a whole.

Here we are going to discuss a publication (Andersson et al. Impaired autoimmune T helper 17 cell responses following DNA vaccination against rat experimental autoimmune encephalomyelitis. PLoS One 2008;3(11):e3682) that seems to demonstrate, at least in the rat model, that protection from multiple sclerosis (well actually EAE) by DNA immunization with autoantigen is dependent on production of interferon beta by the immunized animal.

To induce EAE (experimental allergic encephalomyelitis) the investigators vaccinated the rats with peptide 91-108 of the myelin oligodendrocyte glycoprotein in Complete Freund’s Adjuvant.  This stimulates an autoimmune reaction against the rat myelin, and rats develop a progressive disease that resembles multiple sclerosis. 

When rats were administered a DNA vaccine encoding the same peptide that the animals were immunized with to induce EAE, the progress of the disease was potently inhibited.  This is similar to what we discussed about in multiple sclerosis patients who were administered the DNA vaccine made by Bayhill Therapeutics against myelin basis protein.  In that situation, specific inhibition of the autoimmune responses was also observed.

What is interesting about the current study is that experiments were performed to determine through what molecular mechanism the DNA vaccine was mediating protection against disease.  It was found that T cells isolated from animals at the peak of disease had a much higher expression of the cytokine IL-17 when restimulated in vitro with the antigen myelin oligodendrocyte glycoprotein 91-108.  Animals that were treated with the DNA vaccine had a lower amount of IL-17 production.  Since IL-17 is associated with multiple sclerosis in both mice and human, it would make sense that a protective vaccine would reduce IL-17 production.  As a quick aside, the anti-diabetes drug metformin, which inhibits EAE, also suppresses production of IL-17 by autoreactive T cells.  Additionally, vitamin D has been demonstrated to reduce IL-17.

With the knowledge that the DNA vaccine seems to reduce ability of autoreactive T cells to produce the “bad” cytokine IL-17, the investigators next wanted to see what exactly is it that is responsible for this reduction in IL-17 producing cells.  So the DNA microarray technique was used to analyze 6240 genes at once to randomly see expression of which genes goes and which goes down after DNA vaccination. 

What was found was that the gene for interferon beta, as well as other genes that are associated with interferon beta were upregulated after immunization.  We know that interferon beta is part of the current-day treatment of multiple sclerosis, but also that it has several systemic side effects.  Therefore this study may be suggesting that DNA vaccination seems to be stimulating the body to make its own interferon beta.  This would be a much more attractive approach as compared to what is currently being performed for two reasons.  Firstly, the DNA vaccination encodes a specific antigen, therefore in addition to receiving interferon beta, the vaccination may offer the possibility of inducing tolerance to the autoantigen selectively.  Secondly, the production of interferon beta stimulating by the DNA vaccine would hypothetically be released at smaller and more localized concentrations, thus not having to “flood” the body with interferon beta from the outside and hopefully reducing the side effects.

But here is the catch…how do we know that the interferon beta being produced as a result of the DNA vaccination is actually responsible for suppression of disease progression?  In order to address this, the investigators created a DNA plasmid for vaccination that not only induced expression of the myelin oligodendrocyte glycoprotein peptide, but also short interferon RNA to target gene expression of interferon beta. 

In other words, the investigators repeated their experiments using two sets of DNA plasmids, one that has previously been shown to protect from disease by inducing expression of the myelin oligodendrocyte glycoprotein peptide, and another one in which the peptide is expressed but interferon beta gene is silenced (actually they used more controls, but these are the main ones to make the point).  It was found that suppression of the interferon beta gene expression resulted in loss of the therapeutic effect !  Also, recall response to peptide in terms of IL-17 secretion was augmented 20-fold if interferon beta was silenced.

What does all this mean?

Firstly, why would interferon beta be made by the simple procedure of DNA vaccination?  After all, DNA vaccination is performed as an alternative delivery of antigen.  Instead of injecting protein or peptides of the protein with adjuvant (which in the case of myelin oligodendrocyte glycoprotein results in disease) one injects DNA encoding the protein or peptide so that the cell generates the protein or peptide internally.  So if its the same protein or peptide being made, then why would one cause disease (direct injection of protein or peptide) but the other (DNA vaccination of the same thing) cause protection from disease and interferon beta production?

The authors state that one likely explanation is that the DNA vaccine backbone (the other parts of the DNA plasmid that do not encode the protein or peptide) has CpG motifs.  CpG motifs are parts of DNA that are recognized by human cells as being foreign and induce production of interferons, including interferon beta.  So it may be the interact effect of the CpG motifs that is responsible for protection.  In fact, the authors cite several papers, such as (Lobell et al. J Immunol 2003 Feb 15;170(4):1806-13) that demonstrate removal of CpG motifs from plasmid backbone used to “immunize” animals from autoimmunity, results in loss of effect.

In conclusion, the study discussed seems to provide a very interesting concept…that DNA vaccination can concurrently induce a cytokine that is therapeutic for multiple sclerosis, while at the same time antigen-specifically modulating an immune response.  It will be very interesting to see how the trials of Bayhill Therapeutics progress using a similar antigen-specific DNA-”vaccine” based approach.

Plasma Exchange on 20 Steroid Unresponsive Multiple Sclerosis Patients

Monday, June 15th, 2009

Plasma exchange (also called plasmapheresis) is the procedure in which blood is taken from the patient, the plasma is removed and replaced with donor plasma (or sometimes plasma replacements such as albumin), and reintroduced into the body with the original cellular component.

The aim of the procedure is to deplete the blood of various immunological factors, such as antibodies, that may be associated with pathology, or causing of the disease process.  Obviously this is a short-term solution since antibodies are made by B cells and the original B cells that are making putatively harmful antibodies will still be in the patient after the plasmapheresis is complete.  However it may be that the plasmapheresis gives the immune system time to “re-adjust itself”.  An extreme example of the immune system re-adjusting itself is in the clinical trials where they patient’s hematopoietic (blood making) stem cells are extracted, the patient’s immune system is destroyed on purpose, and then the hematopoietic stem cells are placed back into the patient to create a “re-adjusted” immune system that hopefully will not be attacking the myelin sheath anymore.  Obviously this process has many possible side effects and at least theoretically, it seems more attractive to use your own fat derived stem cells for multiple sclerosis

In any case, plasma exchange offers the possibility of removing some of the pathological components so that the immune system may try to “self-regulate” itself.  How could this be?  One possibility of this is through giving T regulatory cells a chance by reducing the inflammation-creating cytokines and antibodies found in the plasma of multiple sclerosis patients.  On the other hand, the actual effector cells in multiple sclerosis are the CD4 T cells, which activate macrophages and myeloid cells to infiltrate the central nervious system, so would removal of antibodies and soluble components really have a significant impact?

The area of plasma exchange for multiple sclerosis appears to be rather controversial.  On its website, the National MS Society states: “It is not clear whether plasmapheresis is of benefit in the short- or long-term treatment of MS, and its use in MS remains controversial.

We write about plasma exchange for multiple sclerosis today because a recent paper was published (Trebst et al. Plasma Exchange Therapy in Steroid-Unresponsive Relapses in Patients with Multiple Sclerosis. Blood Purif. 2009 Jun 11;28(2):108-115) in which 20 patients who were unresponsive to steroids were reported upon. 

The investigators from the Department of Neurology, Medical School Hannover, Hannover, Germany, reported ”a marked-to-moderate clinical response with clear gain of function in 76% of patients with uni- or bilateral optic neuritis and in 87.5% of patients with relapses other than optic neuritis was observed.”

The concluded that “Plasma exchange is an effective and well tolerated therapeutic option for steroid-unresponsive MS relapses.

It will be interesting to elucidate the immunological mechanisms by which plasma exchange may mediate its effects, and if it may be incorporated into other immune modulatory therapies.  Such a simple incorporation could be the combination of plasma exchange and antigen-specific immunization to achieve tolerance.  We previously discussed here that immunization in the presence of inflammation or “danger” is often associated with immune activation, whereas introduction of antigen in absence of inflammation can be associated with tolerance.  Therefore by “washing the body” of inflammatory agents, one may achieve even better effects with agents such as BioMS’s MBP8298 product or Bayhill Therapeutic’s myelin basic protein DNA vaccine called BHT-3009

It is possible that in the future be combined with agents that increase existing nerve condition such as fampridine and of course mesenchymal stem cells.

DNA Vaccination for Multiple Sclerosis: Phase I/II Trial Results

Wednesday, June 10th, 2009

As we discussed here on StemNow.com, the possibility of antigen-specific tolerance for multiple sclerosis is, along with regenerative medicine, the most promising area of research in this field. 

Clinical trials have previously tried to induce tolerance in multiple sclerosis by selectively inducing immune response against the autoreactive T cells, with some degree of effect. 

The current clinical trial that we will discuss here uses immunization with a DNA vaccine encoding myelin basic protein to induce antigen-specific tolerance, or inhibition of immunity.   It was published as a collaboration between the company Bayhill Therapeutics, and several academic centers (Bar-Or et al. Induction of antigen-specific tolerance in multiple sclerosis after immunization with DNA encoding myelin basic protein in a randomized, placebo-controlled phase 1/2 trial. Arch Neurol 2007 Oct;64(10):1407-15). 

Since myelin basic protein is what the immune system is attacking in multiple sclerosis, or at least one of the main targets, the idea was that if myelin basic protein could be administered intramuscularly, or better said, expressed intramuscularly, then through the immune system may actually be suppressed in response to it.  Below is a picture of the plasmid that was used for injection. 

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The clinical trial was performed on 30 patients with either secondary progressive or relapse-remitting multiple sclerosis.  Patients had to have 1-5 gadolinium lesions on MRI, disease worsening in the past 2 years, or relapse.  Additionally, patients were not allowed to be taking other drugs or therapies that may modify the course of multiple sclerosis progression.
Three doses of plasmid were administered at weeks 1,3, 5, and 9 intramuscularly in PBS.  Patients were also given atrovastatin calcium (which ended up having no effect). 
At the end of the study, patients receiving the DNA vaccine had less autoreactive T cells, however no statistically significant improvement in MRI lesion size was observed. 

This study is interesting because it is, to our knowledge, the first time that DNA vaccination was used for induction of immunological tolerance in patients in an antigen-specific manner.  Unfortunately, the lack of actual efficacy in MRI lesion size, or even lack of symptomological improvement (it was not discussed), suggests that numerous other modifications, or at least large sample sizes, need to be performed to see an effect.

On a positive note, one of the interesting features of this study was that even though the antigen myelin basic protein was administered as a “tolerogen”, inhibition of immune responses against other autoantigens, such as PLP.  This suggests that the immune system may be somehow “re-educating itself”.  We proposed the concept of “epitope spreading” in the context of immune regulation many years ago, and this may be an excellent example.

Given that autologous stromal vascular fraction contains antiinflammatory cells in addition to regenerative mesenchymal stem cells, it may be worthwhile to see whether adipose non-expanded stem cell therapy affects epitope spreading both from the pathogenic and regulatory perspective.