Individual and Familial Susceptibility to MPTP in a Common Marmoset Model for Parkinson's Disease.

INTRODUCTION: Insight into susceptibility mechanisms underlying Parkinson's disease (PD) would aid the understanding of disease etiology, enable target finding and benefit the development of more refined disease-modifying strategies. METHODS: We used intermittent low-dose MPTP (0.5 mg/kg/week) injections in marmosets and measured multiple behavioral and neurochemical parameters. Genetically diverse monkeys from different breeding families were selected to investigate inter- and intrafamily differences in susceptibility to MPTP treatment. RESULTS: We show that such differences exist in clinical signs, in particular nonmotor PD-related behaviors, and that they are accompanied by differences in neurotransmitter levels. In line with the contribution of a genetic component, different susceptibility phenotypes could be traced back through genealogy to individuals of the different families. CONCLUSION: Our findings show that low-dose MPTP treatment in marmosets represents a clinically relevant PD model, with a window of opportunity to examine the onset of the disease, allowing the detection of individual variability in disease susceptibility, which may be of relevance for the diagnosis and treatment of PD in humans.

Unravelling the T-cell-mediated autoimmune attack on CNS myelin in a new primate EAE model induced with MOG34-56 peptide in incomplete adjuvant.

Induction of experimental autoimmune encephalomyelitis (EAE) has been documented in common marmosets using peptide 34-56 from human myelin/oligodendrocyte glycoprotein (MOG(34-56) ) in incomplete Freund's adjuvant (IFA). Here, we report that this EAE model is associated with widespread demyelination of grey and white matter. We performed an in-depth analysis of the specificity, MHC restriction and functions of the activated T cells in the model, which likely cause EAE in an autoantibody-independent manner. T-cell lines isolated from blood and lymphoid organs of animals immunized with MOG(34-56) displayed high production of IL-17A and specific lysis of MOG(34-56) -pulsed EBV B-lymphoblastoid cells as typical hallmarks. Cytotoxicity was directed at the epitope MOG(40-48) presented by the non-classical MHC class Ib allele Caja-E, which is orthologue to HLA-E and is expressed in non-inflamed brain. In vivo activated T cells identified by flow cytometry in cultures with MOG(34-56,) comprised CD4(+) CD56(+) and CD4(+) CD8(+) CD56(+) T cells. Furthermore, phenotypical analysis showed that CD4(+) CD8(+) CD56(+) T cells also expressed CD27, but CD16, CD45RO, CD28 and CCR7 were absent. These results show that, in the MOG34-56/IFA marmoset EAE model, a Caja-E-restricted population of autoreactive cytotoxic T cells plays a key role in the process of demyelination in the grey and white matter.

Brain Inflammation and Intracellular α-Synuclein Aggregates in Macaques after SARS-CoV-2 Infection.

SARS-CoV-2 causes acute respiratory disease, but many patients also experience neurological complications. Neuropathological changes with pronounced neuroinflammation have been described in individuals after lethal COVID-19, as well as in the CSF of hospitalized patients with neurological complications. To assess whether neuropathological changes can occur after a SARS-CoV-2 infection, leading to mild-to-moderate disease, we investigated the brains of four rhesus and four cynomolgus macaques after pulmonary disease and without overt clinical symptoms. Postmortem analysis demonstrated the infiltration of T-cells and activated microglia in the parenchyma of all infected animals, even in the absence of viral antigen or RNA. Moreover, intracellular α-synuclein aggregates were found in the brains of both macaque species. The heterogeneity of these manifestations in the brains indicates the virus' neuropathological potential and should be considered a warning for long-term health risks, following SARS-CoV-2 infection.

Effect of Housing Conditions on Cortisol and Body Fat Levels in Female Rhesus Macaques.

Macaques are among the most commonly used non-human primates in biomedical research. They are highly social animals, yet biomedical studies often require group-living animals to be pair-housed in a controlled environment. A change in environment causes only short-term stress in adapting individuals, while non-adapting animals may experience long-term stress that can adversely affect study results. Individuals likely differ in their ability to adapt depending on individual characteristics. Changes in cortisol and body fat levels may reflect these different individual responses. Here, we investigate the long-term effect of a change from group- to pair-housing on cortisol and body fat levels in 32 female rhesus macaques, exploring whether age, dominance rank, original cortisol, and body fat levels are related to long-term stress in pair-housing. Hair samples were analyzed for cortisol levels, while anthropometric measurements and computed tomography were performed to quantify body fat. Monkeys served as their own control with a 7.5-month period between the measurements. Cortisol levels increased, while average body fat levels did not differ when individuals were moved from group- to pair-housing. Cortisol and body fat levels were not significantly correlated. Changes in cortisol were independent of age and dominance rank, whereas individual variation in body fat alterations was related to the group-housed body fat level and dominance rank. Although this study did not identify individual characteristics related to long-term stress in pair-housing, the individual variation confirms that some individuals are more resilient to change than others and provides possibilities for future refinement studies.

Involvement of the Red Nucleus in the Compensation of Parkinsonism may Explain why Primates can develop Stable Parkinson's Disease.

Neurological compensatory mechanisms help our brain to adjust to neurodegeneration as in Parkinson's disease. It is suggested that the compensation of the damaged striato-thalamo-cortical circuit is focused on the intact thalamo-rubro-cerebellar pathway as seen during presymptomatic Parkinson, paradoxical movement and sensorimotor rhythm (SMR). Indeed, the size of the red nucleus, connecting the cerebellum with the cerebral cortex, is larger in Parkinson's disease patients suggesting an increased activation of this brain area. Therefore, the red nucleus was examined in MPTP-induced parkinsonian marmoset monkeys during the presymptomatic stage and after SMR activation by neurofeedback training. We found a reverse significant correlation between the early expression of parkinsonian signs and the size of the parvocellular part of the red nucleus, which is predominantly present in human and non-human primates. In quadrupedal animals it consists mainly of the magnocellular part. Furthermore, SMR activation, that mitigated parkinsonian signs, further increased the size of the red nucleus in the marmoset monkey. This plasticity of the brain helps to compensate for dysfunctional movement control and can be a promising target for compensatory treatment with neurofeedback technology, vibrotactile stimulation or DBS in order to improve the quality of life for Parkinson's disease patients.

Sensorimotor rhythm neurofeedback as adjunct therapy for Parkinson's disease.

Neurofeedback may enhance compensatory brain mechanisms. EEG-based sensorimotor rhythm neurofeedback training was suggested to be beneficial in Parkinson's disease. In a placebo-controlled study in parkinsonian nonhuman primates we here show that sensorimotor rhythm neurofeedback training reduces MPTP-induced parkinsonian symptoms and both ON and OFF scores during classical L-DOPA treatment. Our findings encourage further development of sensorimotor rhythm neurofeedback training as adjunct therapy for Parkinson's disease which might help reduce L-DOPA-induced side effects.

No synergy between ATG induction and costimulation blockade induced kidney allograft survival in rhesus monkeys.

BACKGROUND: Costimulation blockade with antibodies directed against human CD40 and CD86 leads to prolonged kidney allograft survival in rhesus monkeys, but fails to induce permanent graft acceptance. We have tested whether costimulation blockade is more effective after peripheral T-cell ablation with antithymocyte globulin (ATG), with the aim to remove already primed autoreactive cells present in the normal repertoire. METHODS: Rhesus monkeys were transplanted with a mismatched kidney allograft. ATG was given around the time of transplantation (day -1 and 0). Costimulation blockade with anti-CD40+anti-CD86 was given at tapering dosages from day -1 to 56. Cyclosporin A (CsA) was given from day 42 onwards and first rejections occurring after day 42 were treated with prednisone. RESULTS: We observed accelerated rejection in ATG-treated monkeys, compared to animals receiving only costimulation blockade. The accelerated rejection of the kidney allograft occurred despite the application of rejection therapy with steroids and CsA. Three of the five ATG-treated animals were found seropositive for donor-specific alloantibodies. Early biopsies (day 21) from animals treated with ATG and anti-CD40+anti-CD86 show substantially reduced expression of cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and forkhead box P3 (FOXP3) in focal infiltrates as compared to animals treated with only costimulation blockade. Furthermore, we observed the rapid reappearance of CD8 T-cells with a memory phenotype (disappearance of naive CD95/CD11a T-cells) in peripheral blood. CONCLUSION: We conclude that (subtotal) T-cell depletion using ATG does not add to costimulation blockade induced kidney allograft survival.

Costimulation blockade followed by a 12-week period of cyclosporine A facilitates prolonged drug-free survival of rhesus monkey kidney allografts.

Costimulation blockade as a single immunosuppressive treatment modality is not sufficient to prevent graft rejection. Here, we report an induction therapy using antagonistic antibodies against CD40 and CD86, given twice weekly from day -1 until day 56, followed by a delayed 12-week course of low-dose cyclosporine A (CsA) treatment in the rhesus monkey kidney-allograft model. Low-dose CsA treatment was initiated on day 42 and tapered until total cessation of all treatment on day 126. Treatment with anti-CD40/86 alone resulted in graft survival of 61, 71, 75, 78, and 116 days. Costimulation blockade followed by CsA resulted in more than 3-year drug-free survival in two of four animals. None of the animals developed donor-specific alloantibodies. Transforming growth factor-beta producing cells are present in early as well as in late kidney-graft biopsies and could play a role in the observed long-term drug-free graft survival.

Lymphoid-Like Structures with Distinct B Cell Areas in Kidney Allografts are not Predictive for Graft Rejection. A Non-human Primate Study.

Kidney allograft biopsies were analyzed for the presence of B cell clusters/aggregates using CD20 staining. Few B cells were found in the diffuse interstitial infiltrates, but clusters of B cells were found in nodular infiltrates. These nodular infiltrates were smaller shortly after transplantation, and their size increased over time. At the time of clinical rejection, the nodules often presented as tertiary lymphoid structures (TLS) with lymphoid-like follicles. The presence of small B cell clusters during the first 2 months after transplantation was not associated with early rejection. Even in animals that did not reject their allograft, TLS-like structures were present and could disappear over time. Although TLS were more often found in samples with interstitial fibrosis and tubular atrophy (IFTA), TLS were also present in samples without IFTA. The presence and density of clusters resembling tertiary lymphoid structures most likely reflect an ongoing immune response inside the graft and do not necessarily signify a poor graft outcome or IFTA.

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.

Induction of encephalitis in rhesus monkeys infused with lymphocryptovirus-infected B-cells presenting MOG(34-56) peptide.

The overlapping epidemiology of multiple sclerosis (MS) and Epstein-Barr virus (EBV), the increased risk to develop MS after infectious mononucleosis (IM) and the localization of EBV-infected B-cells within the MS brain suggest a causal link between EBV and MS. However, the underlying mechanism is unknown. We hypothesize that EBV-infected B-cells are capable of eliciting a central nervous system (CNS) targeting autoimmune reaction. To test this hypothesis we have developed a novel experimental model in rhesus monkeys of IM-like disease induced by infusing autologous B-lymphoblastoid cells (B-LCL). Herpesvirus papio (HVP) is a lymphocryptovirus related to EBV and was used to generate rhesus monkey B-LCL. Three groups of five animals were included; each group received three intravenous infusions of B-LCL that were either pulsed with the encephalitogenic self peptide MOG(34-56) (group A), a mimicry peptide (981-1003) of the major capsid protein of cytomegalovirus (CMVmcp(981-1003); group B) or the citrullinated MOG(34-56) (cMOG(34-56); group C). Groups A and B received on day 98 a single immunization with MOG(34-56) in incomplete Freund's adjuvant (IFA). Group C monkeys were euthanized just prior to day 98 without booster immunization. We observed self-peptide-specific proliferation of T-cells, superimposed on similar strong proliferation of CD3(+)CD8(+) T-cells against the B-LCL as observed in IM. The brains of several monkeys contained perivascular inflammatory lesions of variable size, comprising CD3(+) and CD68(+) cells. Moreover, clusters of CD3(+) and CD20(+) cells were detected in the meninges. The only evident clinical sign was substantial loss of bodyweight (>15%), a symptom observed both in early autoimmune encephalitis and IM. In conclusion, this model suggests that EBV-induced B-LCL can elicit a CNS targeting inflammatory (auto)immune reaction.