Targeted Diet Modification Reduces Multiple Sclerosis-like Disease in Adult Marmoset Monkeys from an Outbred Colony.

Experimental autoimmune encephalomyelitis (EAE) in common marmosets is a translationally relevant model of the chronic neurologic disease multiple sclerosis. Following the introduction of a new dietary supplement in our purpose-bred marmoset colony, the percentage of marmosets in which clinically evident EAE could be induced by sensitization against recombinant human myelin oligodendrocyte glycoprotein in IFA decreased from 100 to 65%. The reduced EAE susceptibility after the dietary change coincided with reduced Callitrichine herpesvirus 3 expression in the colony, an EBV-related γ1-herpesvirus associated with EAE. We then investigated, in a controlled study in marmoset twins, which disease-relevant parameters were affected by the dietary change. The selected twins had been raised on the new diet for at least 12 mo prior to the study. In twin siblings reverted to the original diet 8 wk prior to EAE induction, 100% disease prevalence (eight out of eight) was restored, whereas in siblings remaining on the new diet the EAE prevalence was 75% (six out of eight). Spinal cord demyelination, a classical hallmark of the disease, was significantly lower in new-diet monkeys than in monkeys reverted to the original diet. In new-diet monkeys, the proinflammatory T cell response to recombinant human myelin oligodendrocyte glycoprotein was significantly reduced, and RNA-sequencing revealed reduced apoptosis and enhanced myelination in the brain. Systematic typing of the marmoset gut microbiota using 16S rRNA sequencing demonstrated a unique, Bifidobacteria-dominated composition, which changed after disease induction. In conclusion, targeted dietary intervention exerts positive effects on EAE-related parameters in multiple compartments of the marmoset's gut-immune-CNS axis.

A B Cell-Driven Autoimmune Pathway Leading to Pathological Hallmarks of Progressive Multiple Sclerosis in the Marmoset Experimental Autoimmune Encephalomyelitis Model.

The absence of pathological hallmarks of progressive multiple sclerosis (MS) in commonly used rodent models of experimental autoimmune encephalomyelitis (EAE) hinders the development of adequate treatments for progressive disease. Work reviewed here shows that such hallmarks are present in the EAE model in marmoset monkeys (Callithrix jacchus). The minimal requirement for induction of progressive MS pathology is immunization with a synthetic peptide representing residues 34-56 from human myelin oligodendrocyte glycoprotein (MOG) formulated with a mineral oil [incomplete Freund's adjuvant (IFA)]. Pathological aspects include demyelination of cortical gray matter with microglia activation, oxidative stress, and redistribution of iron. When the peptide is formulated in complete Freund's adjuvant, which contains mycobacteria that relay strong activation signals to myeloid cells, oxidative damage pathways are strongly boosted leading to more intensive pathology. The proven absence of immune potentiating danger signals in the MOG34-56/IFA formulation implies that a narrow population of antigen-experienced T cells present in the monkey's immune repertoire is activated. This novel pathway involves the interplay of lymphocryptovirus-infected B cells with MHC class Ib/Caja-E restricted CD8+ CD56+ cytotoxic T lymphocytes.

Reverse translation of failed treatments can help improving the validity of preclinical animal models.

A major challenge in translational research is to reduce the currently high proportion of new candidate treatment agents for neuroinflammatory disease, which fail to reproduce promising effects observed in animal models when tested in patients. This disturbing situation has raised criticism against the currently used animal models in preclinical research and calls for improvement of these models. This seems a difficult task as the cause of failure is often not known. Here we propose a potentially useful strategy for investigating why a promising strategy fails as a guidance for improving the validity of the animal model(s).

The translational value of non-human primates in preclinical research on infection and immunopathology.

The immune system plays a central role in the defense against environmental threats - such as infection with viruses, parasites or bacteria - but can also be a cause of disease, such as in the case of allergic or autoimmune disorders. In the past decades the impressive development of biotechnology has provided scientists with biological tools for the development of highly selective treatments for the different types of disorders. However, despite some clear successes the translation of scientific discoveries into effective treatments has remained challenging. The often-disappointing predictive validity of the preclinical animal models that are used in the selection of the most promising vaccine or drug candidates is the Achilles heel in the therapy development process. This publication summarizes the relevance and usage of non-human primates as pre-clinical model in infectious and autoimmune diseases, in particular for biologicals, which due to their high species-specificity are inactive in lower species.

Apocynin, a low molecular oral treatment for neurodegenerative disease.

Accumulating evidence suggests that inflammatory mediators secreted by activated resident or infiltrated innate immune cells have a significant impact on the pathogenesis of neurodegenerative diseases. This may imply that patients affected by a neurodegenerative disease may benefit from treatment with selective inhibitors of innate immune activity. Here we review the therapeutic potential of apocynin, an essentially nontoxic phenolic compound isolated from the medicinal plant Jatropha multifida. Apocynin is a selective inhibitor of the phagocyte NADPH oxidase Nox2 that can be applied orally and is remarkably effective at low dose.

Oral treatment with the NADPH oxidase antagonist apocynin mitigates clinical and pathological features of parkinsonism in the MPTP marmoset model.

This study evaluates the therapeutic efficacy of the NADPH oxidase inhibitor apocynin, isolated as principal bioactive component from the medicinal plant Picrorhiza kurroa, in a marmoset MPTP model of Parkinson's disease (PD). The methoxy-substituted catechol apocynin has a similar structure as homovanillic acid (HVA), a metabolite of dopamine (DA). Apocynin acquires its selective inhibitory capacity of the reactive oxygen species generating NADPH oxidase via metabolic activation by myeloperoxidase (MPO). As MPO is upregulated in activated brain microglia cells of PD patients and in MPTP animal models, the conditions for metabolic activation of apocynin and inhibition of microglia NADPH oxidase are in place. Marmoset monkeys received oral apocynin (100 mg/kg; p.o.) (n = 5) or Gum Arabica (controls; n = 5) three times daily until the end of the study, starting 1 week before PD induction with MPTP (1 mg/kg s.c. for 8 days). Parkinsonian symptoms, motor function, home-cage activity and body weight were monitored to assess the disease development and severity. Post-mortem numbers of the tyrosine hydroxylase expressing DA neurons in the substantia nigra were counted. During the MPTP injections, apocynin limited the body weight loss and relieved parkinsonian symptoms compared to controls (Linear regression, P < 0.05) indicating a reduction of disease progression. During the last test week, apocynin also improved the hand-eye coordination performance compared with vehicle treatment (resp. 39.3 ± 4.5 % and 17.7 ± 6.7 %; P = 0.048) and improved the home cage activity with 32 % (P = 0.029), indicating anti-Parkinson efficacy. Apocynin also increased the number of surviving DA neurons in MPTP-treated marmosets with 8.5 % (P = 0.059), indicating a tendency towards a neuroprotective efficacy. In conclusion, compensation for the loss of DA and its metabolite HVA by apocynin mitigates the PD progression and limits the parkinsonian signs and motor-function deterioration.

The marmoset monkey: a multi-purpose preclinical and translational model of human biology and disease.

The development of biologic molecules (monoclonal antibodies, cytokines, soluble receptors) as specific therapeutics for human disease creates a need for animal models in which safety and efficacy can be tested. Models in lower animal species are precluded when the reagents fail to recognize their targets, which is often the case in rats and mice. In this Feature article we will highlight the common marmoset, a small-bodied nonhuman primate (NHP), as a useful model in biomedical and preclinical translational research.

B-cell depletion attenuates white and gray matter pathology in marmoset experimental autoimmune encephalomyelitis.

This study investigated the effect of CD20-positive B-cell depletion on central nervous system (CNS) white and gray matter pathology in experimental autoimmune encephalomyelitis in common marmosets, a relevant preclinical model of multiple sclerosis. Experimental autoimmune encephalomyelitis was induced in 14 marmosets by immunization with recombinant human myelin oligodendrocyte glycoprotein in complete Freund adjuvant. At 21 days after immunization, B-cell depletion was achieved by weekly intravenous injections of HuMab 7D8, a human-anti-human CD20 antibody that cross-reacts with marmoset CD20. In vivo magnetic resonance imaging showed widespread brain white matter demyelination in control marmosets that was absent in CD20 antibody-treated marmosets. High-contrast postmortem magnetic resonance imaging showed white matter lesions in 4of the 7 antibody-treated marmosets, but these were significantly smaller than those in controls. The same technique revealed gray matter lesions in 5 control marmosets, but none in antibody-treated marmosets. Histologic analysis confirmed that inflammation, demyelination, and axonal damage were substantially reduced in brain, spinal cord, and optic nerves of CD20 antibody-treated marmosets. In conclusion, CD20-postive B-cell depletion by HuMab 7D8 profoundly reduced the development of both white and gray matter lesions in the marmoset CNS. These data underline the central role of B cells in CNS inflammatory-demyelinating disease.

Induction of progressive demyelinating autoimmune encephalomyelitis in common marmoset monkeys using MOG34-56 peptide in incomplete freund adjuvant.

Experimental autoimmune encephalomyelitis in the neotropical primate common marmoset (Callithrix jacchus) is a relevant autoimmune animal model of multiple sclerosis. T cells specific for peptide 34 to 56 of myelin/oligodendrocyte glycoprotein (MOG34-56) have a central pathogenic role in this model. The aim of this study was to assess the requirement for innate immune stimulation for activation of this core pathogenic autoimmune mechanism. Marmoset monkeys were sensitized against synthetic MOG34-56 peptide alone or in combination with the nonencephalitogenic peptide MOG74-96 formulated in incomplete Freund adjuvant, which lacks microbial components. Experimental autoimmune encephalomyelitis development was recorded by monitoring neurological signs, brain magnetic resonance imaging, and longitudinal profiling of cellular and humoral immune parameters. All monkeys developed autoimmune inflammatory/demyelinating central nervous system disease characterized by massive brain and spinal cord demyelinating white matter lesions with activated macrophages and CD3+ T cells. Immune profiling ex vivo demonstrated the activation of mainly CD3+CD4+/8+CD56+ T cells against MOG34-56. Upon ex vivo stimulation, these T cells produced more interleukin 17A compared with TH1 cytokines (e.g. interferon-gamma) and displayed peptide-specific cytolytic activity. These results indicate that the full spectrum of marmoset experimental autoimmune encephalomyelitis can be induced by sensitization against a single MOG peptide in incomplete Freund adjuvant lacking microbial compounds for innate immune activation and by eliciting antigen-specific T-cell cytolytic activity.

Preclinical models of arthritic disease in non-human primates.

The costs for the development of new drugs have increased dramatically over the past 30 years. One of the main reasons for this increase is the low success rate of new drugs being approved for patient use, which is, in part, a consequence of the common use of rodent models for preclinical validation of efficacy. Especially in the development of biologicals, which are now successfully used in the treatment of rheumatoid arthritis, the selection of the right animal model is pivotal. Non-human primates could help to bridge the evolutionary gap between rodent models and human patients.

Suppression of ongoing disease in a nonhuman primate model of multiple sclerosis by a human-anti-human IL-12p40 antibody.

IL-12p40 is a shared subunit of two cytokines with overlapping activities in the induction of autoreactive Th1 cells and therefore a potential target of therapy in Th1-mediated diseases. We have examined whether ongoing disease in a nonhuman primate model of multiple sclerosis (MS) can be suppressed with a new human IgG1kappa Ab against human IL-12p40. Lesions developing in the brain white matter were visualized and characterized with standard magnetic resonance imaging techniques. To reflect the treatment of MS patients, treatment with the Ab was initiated after active brain white matter lesions were detected in T2-weighted images. In placebo-treated control monkeys we observed the expected progressive increase in the total T2 lesion volume and markedly increased T2 relaxation times, a magnetic resonance imaging marker of inflammation. In contrast, in monkeys treated with anti-IL-12p40 Ab, changes in the total T2 lesion volume and T2 relaxation times were significantly suppressed. Moreover, the time interval to serious neurological deficit was delayed from 31 +/- 10 to 64 +/- 20 days (odds ratio, 0.312). These results, in a disease model with high similarity to MS, are important for ongoing and planned trials of therapies that target IL-12 and/or IL-23.

Evaluating the validity of animal models for research into therapies for immune-based disorders.

The last few decades of the 20th century have shown an intensified search for safer and more effective medications against chronic diseases that burden ageing societies of the western world. The impressive development of biotechnological production techniques has greatly facilitated the pharmaceutical development of relatively non-toxic biological molecules. However, despite the huge investments, only a few effective therapies for immune-based diseases have reached the clinic. In this article we use examples from monoclonal antibody trials to discuss the validity and predictive strength of the animal models currently used for the development of effective therapies.