Hepatic expression of GAA results in enhanced enzyme bioavailability in mice and non-human primates

Pompe disease (PD) is a severe neuromuscular disorder caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). PD is currently treated with enzyme replacement therapy (ERT) with intravenous infusions of recombinant human GAA (rhGAA). Although the introduction of ERT represents a breakthrough in the management of PD, the approach suffers from several shortcomings. Here, we developed a mouse model of PD to compare the efficacy of hepatic gene transfer with adeno-associated virus (AAV) vectors expressing secretable GAA with long-term ERT. Liver expression of GAA results in enhanced pharmacokinetics and uptake of the enzyme in peripheral tissues compared to ERT. Combination of gene transfer with pharmacological chaperones boosts GAA bioavailability, resulting in improved rescue of the PD phenotype. Scale-up of hepatic gene transfer to non-human primates also successfully results in enzyme secretion in blood and uptake in key target tissues, supporting the ongoing clinical translation of the approach.

Gene therapy with secreted acid alpha-glucosidase rescues Pompe disease in a novel mouse model with early-onset spinal cord and respiratory defects

Background

Pompe disease (PD) is a neuromuscular disorder caused by deficiency of acidalpha-glucosidase (GAA), leading to motor and respiratory dysfunctions. Available Gaa knock-out (KO) mouse models do not accurately mimic PD, particularly its highly impaired respiratory phenotype.

Methods

Here we developed a new mouse model of PD crossing Gaa KO^B6;129 with DBA2/J mice. We subsequently treated Gaa KO^DBA2/J mice with adeno-associated virus (AAV) vectors expressing a secretable form of GAA (secGAA).

Findings

Male Gaa KO^DBA2/J mice present most of the key features of the human disease, including early lethality, severe respiratory impairment, cardiac hypertrophy and muscle weakness. Transcriptome analyses of Gaa KO^DBA2/J, compared to the parental Gaa KO^B6;129 mice, revealed a profoundly impaired gene signature in the spinal cord and a similarly deregulated gene expression in skeletal muscle. Muscle and spinal cord transcriptome changes, biochemical defects, respiratory and muscle function in the Gaa KO^DBA2/J model were significantly improved upon gene therapy with AAV vectors expressing secGAA.

Interpretation

These data show that the genetic background impacts on the severity of respiratory function and neuroglial spinal cord defects in the Gaa KO mouse model of PD. Our findings have implications for PD prognosis and treatment, show novel molecular pathophysiology mechanisms of the disease and provide a unique model to study PD respiratory defects, which majorly affect patients.

Funding

This work was supported by Genethon, the French Muscular Dystrophy Association (AFM), the European Commission (grant nos. 667751, 617432, and 797144), and Spark Therapeutics.

Rescue of Advanced Pompe Disease in Mice with Hepatic Expression of Secretable Acid α-Glucosidase

Pompe disease is a neuromuscular disorder caused by disease-associated variants in the gene encoding for the lysosomal enzyme acid α-glucosidase (GAA), which converts lysosomal glycogen to glucose. We previously reported full rescue of Pompe disease in symptomatic 4-month-old Gaa knockout (Gaa^−/−) mice by adeno-associated virus (AAV) vector-mediated liver gene transfer of an engineered secretable form of GAA (secGAA). Here, we showed that hepatic expression of secGAA rescues the phenotype of 4-month-old Gaa^−/− mice at vector doses at which the native form of GAA has little to no therapeutic effect. Based on these results, we then treated severely affected 9-month-old Gaa^−/− mice with an AAV vector expressing secGAA and followed the animals for 9 months thereafter. AAV-treated Gaa^−/− mice showed complete reversal of the Pompe phenotype, with rescue of glycogen accumulation in most tissues, including the central nervous system, and normalization of muscle strength. Transcriptomic profiling of skeletal muscle showed rescue of most altered pathways, including those involved in mitochondrial defects, a finding supported by structural and biochemical analyses, which also showed restoration of lysosomal function. Together, these results provide insight into the reversibility of advanced Pompe disease in the Gaa^−/− mouse model via liver gene transfer of secGAA.

Biosafety Studies of a Clinically Applicable Lentiviral Vector for the Gene Therapy of Artemis-SCID

Genetic deficiency of the nuclease DCLRE1C/Artemis causes radiosensitive severe combined immunodeficiency (RS-SCID) with lack of peripheral T and B cells and increased sensitivity to ionizing radiations. Gene therapy based on transplanting autologous gene-modified hematopoietic stem cells could significantly improve the health of patients with RS-SCID by correcting their immune system. A lentiviral vector expressing physiological levels of human ARTEMIS mRNA from an EF1a promoter without post-transcriptional regulation was developed as a safe clinically applicable candidate for RS-SCID gene therapy. The vector was purified in GMP-comparable conditions and was not toxic in vitro or in vivo. Long-term engraftment of vector-transduced hematopoietic cells was achieved in irradiated Artemis-deficient mice following primary and secondary transplantation (6 months each). Vector-treated mice displayed T and B lymphopoiesis and polyclonal T cells, had structured lymphoid tissues, and produced immunoglobulins. Benign signs of inflammation were noted following secondary transplants, likely a feature of the model. There was no evidence of transgene toxicity and no induction of hematopoietic malignancy. In vitro, the vector had low genotoxic potential on murine hematopoietic progenitor cells using an immortalization assay. Altogether, these preclinical data show safety and efficacy, and support further development of the vector for the gene therapy of RS-SCID.

Temporary Reduction of Membrane CD4 with the Antioxidant MnTBAP Is Sufficient to Prevent Immune Responses Induced by Gene Transfer

Unexpectedly, the synthetic antioxidant MnTBAP was found to cause a rapid and reversible downregulation of CD4 on T cells in vitro and in vivo. This effect resulted from the internalization of membrane CD4 T cell molecules into clathrin-coated pits and involved disruption of the CD4/p56^Lck complex. The CD4 deprivation induced by MnTBAP had functional consequences on CD4-dependent infectious processes or immunological responses as shown in various models, including gene therapy. In cultured human T cells, MnTBAP-induced downregulation of CD4 functionally suppressed gp120- mediated lentiviral transduction in a model relevant for HIV infection. The injection of MnTBAP in mice reduced membrane CD4 on lymphocytes in vivo within 5 days of treatment, preventing OVA peptide T cell immunization while allowing subsequent immunization once treatment was stopped. In a mouse gene therapy model, MnTBAP treatment at the time of adenovirus-associated virus (AAV) vector administration, successfully controlled the induction of anti-transgene and anti-capsid immune responses mediated by CD4⁺ T cells, enabling the redosing mice with the same vector. These functional data provide new avenues to develop alternative therapeutic immunomodulatory strategies based on temporary regulation of CD4. These could be particularly useful for AAV gene therapy in which novel strategies for redosing are needed.

AAV Gene Transfer with Tandem Promoter Design Prevents Anti-transgene Immunity and Provides Persistent Efficacy in Neonate Pompe Mice

Hepatocyte-restricted, AAV-mediated gene transfer is being used to provide sustained, tolerogenic transgene expression in gene therapy. However, given the episomal status of the AAV genome, this approach cannot be applied to pediatric disorders when hepatocyte proliferation may result in significant loss of therapeutic efficacy over time. In addition, many multi-systemic diseases require widespread expression of the therapeutic transgene that, when provided with ubiquitous or tissue-specific non-hepatic promoters, often results in anti-transgene immunity. Here we have developed tandem promoter monocistronic expression cassettes that, packaged in a single AAV, provide combined hepatic and extra-hepatic tissue-specific transgene expression and prevent anti-transgene immunity. We validated our approach in infantile Pompe disease, a prototype disease caused by lack of the ubiquitous enzyme acid-alpha-glucosidase (GAA), presenting multi-systemic manifestations and detrimental anti-GAA immunity. We showed that the use of efficient tandem promoters prevents immune responses to GAA following systemic AAV gene transfer in immunocompetent Gaa−/− mice. Then we demonstrated that neonatal gene therapy with either AAV8 or AAV9 in Gaa−/− mice resulted in persistent therapeutic efficacy when using a tandem liver-muscle promoter (LiMP) that provided high and persistent transgene expression in non-dividing extra-hepatic tissues. In conclusion, the tandem promoter design overcomes important limitations of AAV-mediated gene transfer and can be beneficial when treating pediatric conditions requiring persistent multi-systemic transgene expression and prevention of anti-transgene immunity.

Rescue of Pompe disease in mice by AAV-mediated liver delivery of secretable acid α-glucosidase

Glycogen storage disease type II or Pompe disease is a severe neuromuscular disorder caused by mutations in the lysosomal enzyme, acid α-glucosidase (GAA), which result in pathological accumulation of glycogen throughout the body. Enzyme replacement therapy is available for Pompe disease; however, it has limited efficacy, has high immunogenicity, and fails to correct pathological glycogen accumulation in nervous tissue and skeletal muscle. Using bioinformatics analysis and protein engineering, we developed transgenes encoding GAA that could be expressed and secreted by hepatocytes. Then, we used adeno-associated virus (AAV) vectors optimized for hepatic expression to deliver the GAA transgenes to Gaa knockout (Gaa^-/-) mice, a model of Pompe disease. Therapeutic gene transfer to the liver rescued glycogen accumulation in muscle and the central nervous system, and ameliorated cardiac hypertrophy as well as muscle and respiratory dysfunction in the Gaa^-/- mice; mouse survival was also increased. Secretable GAA showed improved therapeutic efficacy and lower immunogenicity compared to nonengineered GAA. Scale-up to nonhuman primates, and modeling of GAA expression in primary human hepatocytes using hepatotropic AAV vectors, demonstrated the therapeutic potential of AAV vector-mediated liver expression of secretable GAA for treating pathological glycogen accumulation in multiple tissues in Pompe disease.

Rescue of GSDIII Phenotype with Gene Transfer Requires Liver- and Muscle-Targeted GDE Expression

Glycogen storage disease type III (GSDIII) is an autosomal recessive disorder caused by a deficiency of glycogen-debranching enzyme (GDE), which results in profound liver metabolism impairment and muscle weakness. To date, no cure is available for GSDIII and current treatments are mostly based on diet. Here we describe the development of a mouse model of GSDIII, which faithfully recapitulates the main features of the human condition. We used this model to develop and test novel therapies based on adeno-associated virus (AAV) vector-mediated gene transfer. First, we showed that overexpression of the lysosomal enzyme alpha-acid glucosidase (GAA) with an AAV vector led to a decrease in liver glycogen content but failed to reverse the disease phenotype. Using dual overlapping AAV vectors expressing the GDE transgene in muscle, we showed functional rescue with no impact on glucose metabolism. Liver expression of GDE, conversely, had a direct impact on blood glucose levels. These results provide proof of concept of correction of GSDIII with AAV vectors, and they indicate that restoration of the enzyme deficiency in muscle and liver is necessary to address both the metabolic and neuromuscular manifestations of the disease.

Efficacy and biodistribution analysis of intracerebroventricular administration of an optimized scAAV9-SMN1 vector in a mouse model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive disease of variable severity caused by mutations in the SMN1 gene. Deficiency of the ubiquitous SMN function results in spinal cord α-motor neuron degeneration and proximal muscle weakness. Gene replacement therapy with recombinant adeno-associated viral (AAV) vectors showed therapeutic efficacy in several animal models of SMA. Here, we report a study aimed at analyzing the efficacy and biodistribution of a serotype-9, self-complementary AAV vector expressing a codon-optimized human SMN1 coding sequence (coSMN1) under the control of the constitutive phosphoglycerate kinase (PGK) promoter in neonatal SMNΔ7 mice, a severe animal model of the disease. We administered the scAAV9-coSMN1 vector in the intracerebroventricular (ICV) space in a dose-escalating mode, and analyzed survival, vector biodistribution and SMN protein expression in the spinal cord and peripheral tissues. All treated mice showed a significant, dose-dependent rescue of lifespan and growth with a median survival of 346 days. Additional administration of vector by an intravenous route (ICV+IV) did not improve survival, and vector biodistribution analysis 90 days postinjection indicated that diffusion from the cerebrospinal fluid to the periphery was sufficient to rescue the SMA phenotype. These results support the preclinical development of SMN1 gene therapy by CSF vector delivery.

Longitudinal in vivo muscle function analysis of the DMSXL mouse model of myotonic dystrophy type 1

Myotonic dystrophy is the most common adult muscle dystrophy. In view of emerging therapies, which use animal models as a proof of principle, the development of reliable outcome measures for in vivo longitudinal study of mouse skeletal muscle function is becoming crucial. To satisfy this need, we have developed a device to measure ankle dorsi- and plantarflexion torque in rodents. We present an in vivo 8-month longitudinal study of the contractile properties of the skeletal muscles of the DMSXL mouse model of myotonic dystrophy type 1. Between 4 and 12 months of age, we observed a reduction in muscle strength in the ankle dorsi- and plantarflexors of DMSXL compared to control mice although the strength per muscle cross-section was normal. Mild steady myotonia but no abnormal muscle fatigue was also observed in the DMSXL mice. Magnetic resonance imaging and histological analysis performed at the end of the study showed respectively reduced muscle cross-section area and smaller muscle fibre diameter in DMSXL mice. In conclusion, our study demonstrates the feasibility of carrying out longitudinal in vivo studies of muscle function over several months in a mouse model of myotonic dystrophy confirming the feasibility of this method to test preclinical therapeutics.

A phase I trial of adeno-associated virus serotype 1-γ-sarcoglycan gene therapy for limb girdle muscular dystrophy type 2C

γ-Sarcoglycanopathy or limb girdle muscular dystrophy type 2C is an untreatable disease caused by autosomal recessively inherited mutations of the γ-sarcoglycan gene. Nine non-ambulatory patients (two males, seven females, mean age 27 years; range 16-38 years) with del525T homozygous mutation of the γ-sarcoglycan gene and no γ-sarcoglycan immunostaining on muscle biopsy were divided into three equal groups to receive three escalating doses of an adeno-associated virus serotype 1 vector expressing the human γ-sarcoglycan gene under the control of the desmin promoter, by local injection into the extensor carpi radialis muscle. The first group received a single injection of 3 × 10(9) viral genomes in 100 µl, the second group received a single injection of 1.5 × 10(10) viral genomes in 100 µl, and the third group received three simultaneous 100-µl injections at the same site, delivering a total dose of 4.5 × 10(10) viral genomes. No serious adverse effects occurred during 6 months of follow-up. All nine patients became adeno-associated virus serotype 1 seropositive and one developed a cytotoxic response to the adeno-associated virus serotype 1 capsid. Thirty days later, immunohistochemical analysis of injected-muscle biopsy specimens showed γ-sarcoglycan expression in all three patients who received the highest dose (4.7-10.5% positively stained fibres), while real-time polymerase chain reaction detected γ-sarcoglycan messenger RNA. In one patient, γ-sarcoglycan protein was detected by western blot. For two other patients who received the low and intermediate doses, discrete levels of γ-sarcoglycan expression (<1% positively stained fibres) were also detectable. Expression of γ-sarcoglycan protein can be induced in patients with limb girdle muscular dystrophy type 2C by adeno-associated virus serotype 1 gene transfer, with no serious adverse effects.

Evidence for long-term efficacy and safety of gene therapy for Wiskott-Aldrich syndrome in preclinical models

Wiskott-Aldrich Syndrome (WAS) is a life-threatening X-linked disease characterized by immunodeficiency, thrombocytopenia, autoimmunity, and malignancies. Gene therapy could represent a therapeutic option for patients lacking a suitable bone marrow (BM) donor. In this study, we analyzed the long-term outcome of WAS gene therapy mediated by a clinically compatible lentiviral vector (LV) in a large cohort of was(null) mice. We demonstrated stable and full donor engraftment and Wiskott-Aldrich Syndrome protein (WASP) expression in various hematopoietic lineages, up to 12 months after gene therapy. Importantly, we observed a selective advantage for T and B lymphocytes expressing transgenic WASP. T-cell receptor (TCR)-driven T-cell activation, as well as B-cell's ability to migrate in response to CXCL13, was fully restored. Safety was evaluated throughout the long-term follow-up of primary and secondary recipients of WAS gene therapy. WAS gene therapy did not affect the lifespan of treated animals. Both hematopoietic and nonhematopoietic tumors arose, but we excluded the association with gene therapy in all cases. Demonstration of long-term efficacy and safety of WAS gene therapy mediated by a clinically applicable LV is a key step toward the implementation of a gene therapy clinical trial for WAS.

Expression of mdr1 is required for efficient long term regeneration of dystrophic muscle

The mouse mdr1a and mdr1b genes are expressed in skeletal muscle, though their precise role in muscle is unknown. Dystrophic muscle is characterized by repeated cycles of degeneration and regeneration. To explore the role of the mdr1 genes during muscle regeneration, we have created a triple knockout mouse lacking the mdr1a, mdr1b, and the dystrophin genes. The resulting ReX mice developed normally and were fertile. However, as adults, ReX had a higher proportion of degenerating muscle fibers and greater long-term loss of muscle mass than mdx. ReX muscles were also characterized by a reduced proportion of muscle side population (mSP) cells, of myogenic cells, and a reduced capacity for muscle regeneration. We found too that mSP cells derived from dystrophic muscle are more myogenic than those from normal muscle. Thus, in dystrophic muscle, the mdr1 gene plays an important role in the preservation of the mSP and of the myogenic regenerative potential. Moreover, our results suggest a hitherto unappreciated role of mdr1 in precursor cells of regenerating tissue; they therefore provide an important clue to the physiological significance of mdr1 expression in stem cells.

CD4+CD25+ regulatory T cells inhibit immune-mediated transgene rejection

Like cellular transplantation, gene therapy is often limited by immune rejection of the newly expressed antigen. In a model of gene transfer in muscle, delivery of the influenza hemagglutinin (HA) membrane protein by adeno-associated virus (AAV) is impaired by a strong immune response that leads to a rapid rejection of the transduced fibers. We show here that injection of HA-specific CD4+CD25+ T cells from T-cell receptor (TCR)-transgenic animals, concomitant with gene transfer, down-regulates the anti-HA cytotoxic and B-lymphocyte responses and enables persistent HA expression in muscle. This demonstrates for the first time that adoptive transfer of antigen-specific CD4+CD25+ regulatory T cells can be used to induce sustained transgene engraftment in solid tissues.

Regulatory function of in vivo anergized CD4(+) T cells

It has been suggested that anergic T cells may not be only inert cells but may rather play an active role, for example by regulating immune responses. We have previously reported the existence of "anergic" IL-10-producing CD4(+) T cells generated in vivo by continuous antigenic stimulation. Using a gene transfer system where the antigen recognized by such T cells is expressed in skeletal muscle by two different DNA viral vectors, we show that these cells not only remain tolerant toward their cognate antigen but also can suppress the immune response of naive T cells against the immunogenic adenoviral proteins. Furthermore, they can completely inhibit tissue destruction that takes place as a result of an immune response. The system presented here is unique in that the T cells have been anergized in vivo, their antigen specificity and functional status are known, and the amount, form, and timing of antigen expression can be manipulated. This model will therefore permit us to carefully dissect the mechanisms by which these anergic T cells regulate the priming and/or effector function of naive T cells.

Successful interference with cellular immune responses to immunogenic proteins encoded by recombinant viral vectors

Vectors derived from the adeno-associated virus (AAV) have been successfully used for the long-term expression of therapeutic genes in animal models and patients. One of the major advantages of these vectors is the absence of deleterious immune responses following gene transfer. However, AAV vectors, when used in vaccination studies, can result in efficient humoral and cellular responses against the transgene product. It is therefore important to understand the factors which influence the establishment of these immune responses in order to design safe and efficient procedures for AAV-based gene therapies. We have compared T-cell activation against a strongly immunogenic protein, the influenza virus hemagglutinin (HA), which is synthesized in skeletal muscle following gene transfer with an adenovirus (Ad) or an AAV vector. In both cases, cellular immune responses resulted in the elimination of transduced muscle fibers within 4 weeks. However, the kinetics of CD4(+) T-cell activation were markedly delayed when AAV vectors were used. Upon recombinant Ad (rAd) gene transfer, T cells were activated both by direct transduction of dendritic cells and by cross-presentation of the transgene product, while upon rAAV gene transfer T cells were only activated by the latter mechanism. These results suggested that activation of the immune system by the transgene product following rAAV-mediated gene transfer might be easier to control than that following rAd-mediated gene transfer. Therefore, we tested protocols aimed at interfering with either antigen presentation by blocking the CD40/CD40L pathway or with the T-cell response by inducing transgene-specific tolerance. Long-term expression of the AAV-HA was achieved in both cases, whereas immune responses against Ad-HA could not be prevented. These data clearly underline the importance of understanding the mechanisms by which vector-encoded proteins are recognized by the immune system in order to specifically interfere with them and to achieve safe and stable gene transfer in clinical trials.

Sex and parity modulate cytokine production during murine ageing

We have previously shown that physiological hormone differences related to pregnancy or sex affect the age-related distribution of mononuclear cell populations during murine ageing. To determine whether such changes are involved in the age-related changes in functions of T cells, we examined the secretion of major T cell immunoregulatory cytokines (IL-2, IL-4, interferon-gamma (IFN-gamma), IL-3, IL-6 and granulocyte-macrophage colony-stimulating factor (GM-CSF)) of in vitro concanavalin A-activated spleen cells of C57B1/6 mice. The study included multiparous and virgin females and males at 2, 8, 15 and 23 months of age. Short-term effects of parity (8 months) were evidenced by the decrease of IFN-gamma and the preserved IL-2 production in multiparous females (8 months), while IFN-gamma was unchanged and IL-2 decreased in virgin mice. The increase in IL-4 production appeared earlier in multiparous females (15 months) than in virgin mice (23 months). The increase in IL-4/IFN-gamma and IL-4/IL-2 ratios at 8 and 15 months, respectively, in multiparous females, suggests that pregnancy modifies the Th1/Th2 equilibrium. In late adulthood (15 months), IL-6 and GM-CSF production was higher in multiparous females than in virgin males or females. Sex differences were also noticed: IFN-gamma secretion capacity was lower in males than in females during ageing. This study underlines that the onset, magnitude and kinetics of the age-related changes in cytokine production are parity- and sex-dependent. These changes probably influence the incidence of age-related diseases and may explain the greater longevity of females.

Angiogenic and inflammatory responses following skeletal muscle injury are altered by immune neutralization of endogenous basic fibroblast growth factor, insulin-like growth factor-1 and transforming growth factor-beta 1

Injured skeletal muscle degeneration comprises early microvascular changes and inflammatory cell infiltration, possibly under the control of several growth factors. We have studied the role of basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF1), and transforming growth factor beta-1 (TGF beta 1), by injecting specific anti-growth factor neutralizing antibodies into mouse extensor digitorum longus muscle at the time of injury (denervation and devascularization). Four days later, at the height of damaged myofiber phagocytosis, we assessed quantitatively revascularization, phagocytic activity, and inflammation. The immune neutralization of bFGF reduced the number of capillaries, macrophages and mast cells, and delayed necrotic myofiber phagocytosis. The immune neutralization of IGF1 or TFG beta 1 promoted muscle revascularization, macrophage infiltration and necrotic myofiber phagocytosis. While IGF1 neutralization reduced the number of mast cells and did not modify that of T-cells or neutrophils, TGF beta 1 neutralization increased the number of all of these cells. This study strongly suggests differing roles for bFGF, IGF1 and TFG beta 1 in angiogenic and inflammatory responses during muscle degeneration, apart from their known effects on the behaviour of myogenic cells.

Factors inducing mast cell accumulation in skeletal muscle

It has been suggested that mast cells contribute to the phenotype of dystrophinopathies, but the mechanisms of their recruitment into the skeletal muscle remain hypothetical. The aim of this study is to quantify the presence of mast cells in muscle during the cellular events of myofibre degeneration and regeneration. For this purpose, we compare the mast cell profile in dystrophin-deficient mdx mice in which muscles exhibit spontaneous cycles of degeneration-regeneration from 3 weeks of age, with that in Swiss mice in which muscles were injured either by ischaemia or by notexin injection. Notexin is an A2-type phospholipase that rapidly disrupts myofibre plasma membranes, while ischaemia results in a slower process of degeneration. Both lesions are followed by a successful regeneration. In intact muscles, mast cell counts (mean +/- SEM/mm2) range from 1.8 +/- 1 to 4.3 +/- 1.6. The injection of notexin is far more potent in recruiting mast cells into damaged muscle than is ischaemia (118.5 +/- 13.0 vs 12.3 +/- 1.8/mm2). Thus we conclude that the early disruption of the myofibre membrane could elicit mast cell accumulation in skeletal muscle. This may explain the elevated number of mast cells observed in mdx muscles, as dystrophin deficiency is though to induce myofibre membrane leakage. On the other hand, mast cells are more numerous in muscles of young and adult mdx mice that are allowed to regenerate, than in muscles of older animals in which there is little regeneration and fibrosis develops. In injured muscles, the peak of mast cell number is at the onset of regeneration (by day 3 after notexin injection, and by day 11 after ischaemia), rather than during the phase of myofibre necrosis. Therefore, we suggest that the mast cells, through the effects of released mediators, could contribute to muscle regeneration.

Adjuvant activity of polar glycopeptidolipids of Mycobacterium chelonae (pGPL-Mc) on the immunogenic and protective effects of an inactivated influenza vaccine

Mice injected intraperitoneally with 2.5 or 25 mg/kg of pGPL-Mc, before, during or after the administration of a monovalent inactivated influenza vaccine (8 IU of A/New Jersey/X53), exhibited significantly very high haemagglutination inhibition (HI) antibody titers (up to 8 fold) as compared to vaccine controls. Treatment with pGPL-Mc has increased the protective effect of the vaccine by completely abolishing, in certain treatment groups, the onset of symptoms of disease and mortality after a lethal challenge with 5 LD50 of A/PR/8/34 virus, 60 days after the first vaccination. Moreover, the development of visible pulmonary lesions significantly decreased in surviving vaccinated mice treated with 25 mg/kg of pGPL-Mc on day D0. These results suggest that pGPL-Mc is a potent adjuvant to the immunogenic and protective effect of inactivated influenza vaccines.