[Measles subacute sclerosing panencephalitis (SSPE): A still present and still mysterious fatal disease. History, Diagnosis and Assumptions]. / La panencéphalite sclérosante subaiguë de la rougeole - Une maladie mortelle encore présente et toujours mystérieuse.

Subacute sclerosing panencephalitis, a late complication of measles, is still present during epidemics of this disease due to insufficient vaccination. After a historical review, the importance of the diagnostic criteria and the pathophysiology of SSEP are discussed. Numerous studies on the parameters of innate immunity and interferon responses tend to show a decrease in the activity of cellular immunity. Several hypotheses are formulated based on the publications of the different forms of the disease: Congenital, perinatal, forms with short incubation similar to acute inclusion encephalitis (AIE), rapidly evolving forms, forms of the immunocompromised, or even adults. Familial forms have been identified, suggesting a genetic cause. Based on the duration of the latency period, two groups have been individualized, prompting a retrospective and prospective analysis of the exomes of these patients. The knowledge of the genes involved should be useful for the understanding of the pathophysiology of SSPE and other late neurological RNA virus infections.

Title: La panencéphalite sclérosante subaiguë de la rougeole - Une maladie mortelle encore présente et toujours mystérieuse. Abstract: La panencéphalite sclérosante subaiguë (PESS), une complication tardive de la rougeole, est encore présente lors d'épidémies de cette maladie dues aux insuffisances de la vaccination. Après un rappel historique, nous aborderons la physiopathologie de la PESS et l'importance des critères diagnostiques. De nombreux travaux portant sur les paramètres de l'immunité innée et sur ceux des réponses interféron tendent à montrer une baisse de l'activité de l'immunité cellulaire au cours de cette maladie. Nous formulons ici plusieurs hypothèses s'appuyant sur des publications concernant différentes formes de la maladie : congénitales, périnatales, formes à incubation courte, semblables à l'encéphalite aiguë à inclusions (EAI), formes d'évolution rapide, formes retrouvées chez les immunodéprimés ou chez l'adulte. Des formes familiales ont également été identifiées, suggérant une origine génétique. Selon la durée de la période de latence entre rougeole et la PESS, deux groupes de patients ont été individualisés, incitant à des analyses rétrospective et prospective des exomes de ces malades. La connaissance des gènes participant à la maladie devrait être utile pour la compréhension de la physiopathologie de la PESS mais aussi d'autres infections neurologiques tardives dues à des virus à ARN.

[Pathological consequences of excess of interferon in vivo]. / Conséquences pathologiques d'un excès d'interféron in vivo - Comment ne pas sous-estimer des expériences in vivo quand elles peuvent paraître anecdotiques et non conformistes.

In this brief review, the authors present a history of the different aspects of the scientific puzzle leading from pioneer animal studies and astute clinical experimental observations to a mature appreciation of the deleterious role of excess of a type I interferon in human pathology.

Paradoxical Effect of Chloroquine Treatment in Enhancing Chikungunya Virus Infection.

Since 2005, Chikungunya virus (CHIKV) re-emerged and caused numerous outbreaks in the world, and finally, was introduced into the Americas in 2013. The lack of CHIKV-specific therapies has led to the use of non-specific drugs. Chloroquine, which is commonly used to treat febrile illnesses in the tropics, has been shown to inhibit CHIKV replication in vitro. To assess the in vivo effect of chloroquine, two complementary studies were performed: (i) a prophylactic study in a non-human primate model (NHP); and (ii) a curative study "CuraChik", which was performed during the Reunion Island outbreak in 2006 in a human cohort. Clinical, biological, and immunological data were compared between treated and placebo groups. Acute CHIKV infection was exacerbated in NHPs treated with prophylactic administration of chloroquine. These NHPs displayed a higher viremia and slower viral clearance (p < 0.003). Magnitude of viremia was correlated to the type I IFN response (Rho = 0.8, p < 0.001) and severe lymphopenia (Rho = 0.8, p < 0.0001), while treatment led to a delay in both CHIKV-specific cellular and IgM responses (p < 0.02 and p = 0.04, respectively). In humans, chloroquine treatment did not affect viremia or clinical parameters during the acute stage of the disease (D1 to D14), but affected the levels of C-reactive Protein (CRP), IFNα, IL-6, and MCP1 over time (D1 to D16). Importantly, no positive effect could be detected on prevalence of persistent arthralgia at Day 300. Although inhibitory in vitro, chloroquine as a prophylactic treatment in NHPs enhances CHIKV replication and delays cellular and humoral response. In patients, curative chloroquine treatment during the acute phase decreases the levels of key cytokines, and thus may delay adaptive immune responses, as observed in NHPs, without any suppressive effect on peripheral viral load.

Production of TNF-alpha ex vivo is predictive of an immune response to flu vaccination in a frail elderly population.

OBJECTIVE: To investigate the relationship between the response to influenza vaccination and the ability to produce proinflamatory cytokines in elderly subjects. METHODS: Whole blood samples from 25 elderly subjects collected before influenza vaccination were stimulated with the influenza vaccine in order to evaluate the secretion of five specific cytokines: TNFα, IFNα, IFNγ, IL2 and IL10. The results were correlated with the increased HAI antibody titres two weeks after vaccination. RESULTS: Only 30% of elderly individuals seroconverted after vaccination. Although 50 to 70% of the cohort did not produce TNFα, IFNα, IFNγ, IL2 or IL10, all of the individuals who seroconverted were able to produce TNFα. Furthermore production of IFNγ, with or without production of IFNα/ß, was not associated with a better response to the vaccine. CONCLUSION: Production of TNFα appears to be primordial for an efficient vaccine response, and may provide a predictive marker for the humoral response to vaccination. It may also provide the basis for evaluating agents designed to rescue TNFα-producing cells. This study emphasises a need to rescue TNF-producing cell function.

Spondyloenchondrodysplasia Due to Mutations in ACP5: A Comprehensive Survey.

PURPOSE: Spondyloenchondrodysplasia is a rare immuno-osseous dysplasia caused by biallelic mutations in ACP5. We aimed to provide a survey of the skeletal, neurological and immune manifestations of this disease in a cohort of molecularly confirmed cases. METHODS: We compiled clinical, genetic and serological data from a total of 26 patients from 18 pedigrees, all with biallelic ACP5 mutations. RESULTS: We observed a variability in skeletal, neurological and immune phenotypes, which was sometimes marked even between affected siblings. In total, 22 of 26 patients manifested autoimmune disease, most frequently autoimmune thrombocytopenia and systemic lupus erythematosus. Four patients were considered to demonstrate no clinical autoimmune disease, although two were positive for autoantibodies. In the majority of patients tested we detected upregulated expression of interferon-stimulated genes (ISGs), in keeping with the autoimmune phenotype and the likely immune-regulatory function of the deficient protein tartrate resistant acid phosphatase (TRAP). Two mutation positive patients did not demonstrate an upregulation of ISGs, including one patient with significant autoimmune disease controlled by immunosuppressive therapy. CONCLUSIONS: Our data expand the known phenotype of SPENCD. We propose that the OMIM differentiation between spondyloenchondrodysplasia and spondyloenchondrodysplasia with immune dysregulation is no longer appropriate, since the molecular evidence that we provide suggests that these phenotypes represent a continuum of the same disorder. In addition, the absence of an interferon signature following immunomodulatory treatments in a patient with significant autoimmune disease may indicate a therapeutic response important for the immune manifestations of spondyloenchondrodysplasia.

Diphtheria, tetanus, poliomyelitis, yellow fever and hepatitis B seroprevalence among HIV1-infected migrants. Results from the ANRS VIHVO vaccine sub-study.

BACKGROUND: Few data are available on the seroprotection status of HIV1-infected patients with respect to vaccine-preventable diseases. OBJECTIVE: To describe, in a population of HIV1-infected migrants on stable, effective ART therapy, the seroprevalence of diphtheria, poliomyelitis, tetanus, yellow fever antibodies and serostatus for hepatitis B, and to identify factors associated with seroprotection. Vaccine responses against diphtheria, tetanus, poliomyelitis and yellow fever were also studied. METHODS: Sub-Saharan African patients participating in the ANRS-VIHVO cohort were enrolled prior to travel to their countries of origin. Serologic analyses were performed in a central laboratory before and after the trip. Univariate and multivariate logistic regression was used to identify factors associated with initial seroprotection. RESULTS: 250 patients (99 men and 151 women) were included in the seroprevalence study. Median age was 45 years (IQR 39-52), median CD4 cell count was 440/µL (IQR 336-571), and 237 patients (95%) had undetectable HIV1 viral load. The initial seroprevalence rates were 69.0% (95%CI 63.2-74.7) for diphtheria, 70.7% (95%CI 65.0-76.3) for tetanus, and 85.9% (95%CI 81.6-90.2) for yellow fever. Only 64.4% (95%CI 58.5-70.3) of patients had protective antibody titers against all three poliomyelitis vaccine strains before travel. No serological markers of hepatitis B were found in 18.6% of patients (95%CI 13.7-23.3). Patient declaration of prior vaccination was the only factor consistently associated with initial seroprotection. CONCLUSIONS: We found a low prevalence of seroprotection against diphtheria, poliomyelitis, tetanus and hepatitis B. HIV infected migrants living in France and traveling to their native countries need to have their vaccine schedule completed.

Inherited DOCK2 Deficiency in Patients with Early-Onset Invasive Infections.

Background Combined immunodeficiencies are marked by inborn errors of T-cell immunity in which the T cells that are present are quantitatively or functionally deficient. Impaired humoral immunity is also common. Patients have severe infections, autoimmunity, or both. The specific molecular, cellular, and clinical features of many types of combined immunodeficiencies remain unknown. Methods We performed genetic and cellular immunologic studies involving five unrelated children with early-onset invasive bacterial and viral infections, lymphopenia, and defective T-cell, B-cell, and natural killer (NK)-cell responses. Two patients died early in childhood; after allogeneic hematopoietic stem-cell transplantation, the other three had normalization of T-cell function and clinical improvement. Results We identified biallelic mutations in the dedicator of cytokinesis 2 gene (DOCK2) in these five patients. RAC1 activation was impaired in the T cells. Chemokine-induced migration and actin polymerization were defective in the T cells, B cells, and NK cells. NK-cell degranulation was also affected. Interferon-α and interferon-λ production by peripheral-blood mononuclear cells was diminished after viral infection. Moreover, in DOCK2-deficient fibroblasts, viral replication was increased and virus-induced cell death was enhanced; these conditions were normalized by treatment with interferon alfa-2b or after expression of wild-type DOCK2. Conclusions Autosomal recessive DOCK2 deficiency is a new mendelian disorder with pleiotropic defects of hematopoietic and nonhematopoietic immunity. Children with clinical features of combined immunodeficiencies, especially with early-onset, invasive infections, may have this condition. (Supported by the National Institutes of Health and others.).

Plasmacytoid Dendritic Cell Infection and Sensing Capacity during Pathogenic and Nonpathogenic Simian Immunodeficiency Virus Infection.

UNLABELLED: Human immunodeficiency virus (HIV) in humans and simian immunodeficiency virus (SIV) in macaques (MAC) lead to chronic inflammation and AIDS. Natural hosts, such as African green monkeys (AGM) and sooty mangabeys (SM), are protected against SIV-induced chronic inflammation and AIDS. Here, we report that AGM plasmacytoid dendritic cells (pDC) express extremely low levels of CD4, unlike MAC and human pDC. Despite this, AGM pDC efficiently sensed SIVagm, but not heterologous HIV/SIV isolates, indicating a virus-host adaptation. Moreover, both AGM and SM pDC were found to be, in contrast to MAC pDC, predominantly negative for CCR5. Despite such limited CD4 and CCR5 expression, lymphoid tissue pDC were infected to a degree similar to that seen with CD4(+) T cells in both MAC and AGM. Altogether, our finding of efficient pDC infection by SIV in vivo identifies pDC as a potential viral reservoir in lymphoid tissues. We discovered low expression of CD4 on AGM pDC, which did not preclude efficient sensing of host-adapted viruses. Therefore, pDC infection and efficient sensing are not prerequisites for chronic inflammation. The high level of pDC infection by SIVagm suggests that if CCR5 paucity on immune cells is important for nonpathogenesis of natural hosts, it is possibly not due to its role as a coreceptor. IMPORTANCE: The ability of certain key immune cell subsets to resist infection might contribute to the asymptomatic nature of simian immunodeficiency virus (SIV) infection in its natural hosts, such as African green monkeys (AGM) and sooty mangabeys (SM). This relative resistance to infection has been correlated with reduced expression of CD4 and/or CCR5. We show that plasmacytoid dendritic cells (pDC) of natural hosts display reduced CD4 and/or CCR5 expression, unlike macaque pDC. Surprisingly, this did not protect AGM pDC, as infection levels were similar to those found in MAC pDC. Furthermore, we show that AGM pDC did not consistently produce type I interferon (IFN-I) upon heterologous SIVmac/HIV type 1 (HIV-1) encounter, while they sensed autologous SIVagm isolates. Pseudotyping SIVmac/HIV-1 overcame this deficiency, suggesting that reduced uptake of heterologous viral strains underlays this lack of sensing. The distinct IFN-I responses depending on host species and HIV/SIV isolates reveal the host/virus species specificity of pDC sensing.

Synthetic scrapie infectivity: interaction between recombinant PrP and scrapie brain-derived RNA.

The key molecular event in human cerebral proteinopathies, which include Alzheimer's, Parkinson's and Huntington's diseases, is the structural conversion of a specific host protein into a ß-sheet-rich conformer. With regards to this common mechanism, it appears difficult to explain the outstanding infectious properties attributed to PrP(Sc), the hallmark of another intriguing family of cerebral proteinopathies known as transmissible spongiform encephalopathies (TSE) or prion diseases. The infectious PrP(Sc) or "prion" is thought to be composed solely of a misfolded form of the otherwise harmless cellular prion protein (PrP(c)). To gain insight into this unique situation, we used the 263K scrapie hamster model to search for a putative PrP(Sc)-associated factor that contributes to the infectivity of PrP(Sc) amyloid. In a rigorously controlled set of experiments that included several bioassays, we showed that originally innocuous recombinant prion protein (recPrP) equivalent to PrP(c) is capable of initiating prion disease in hamsters when it is converted to a prion-like conformation (ß-sheet-rich) in the presence of RNA purified from scrapie-associated fibril (SAF) preparations. Analysis of the recPrP-RNA infectious mixture reveals the presence of 2 populations of small RNAs of approximately 27 and 55 nucleotides. These unprecedented findings are discussed in light of the distinct relationship that may exist between this RNA material and the 2 biological properties, infectivity and strain features, attributed to prion amyloid.

Human intracellular ISG15 prevents interferon-α/ß over-amplification and auto-inflammation.

Intracellular ISG15 is an interferon (IFN)-α/ß-inducible ubiquitin-like modifier which can covalently bind other proteins in a process called ISGylation; it is an effector of IFN-α/ß-dependent antiviral immunity in mice. We previously published a study describing humans with inherited ISG15 deficiency but without unusually severe viral diseases. We showed that these patients were prone to mycobacterial disease and that human ISG15 was non-redundant as an extracellular IFN-γ-inducing molecule. We show here that ISG15-deficient patients also display unanticipated cellular, immunological and clinical signs of enhanced IFN-α/ß immunity, reminiscent of the Mendelian autoinflammatory interferonopathies Aicardi-Goutières syndrome and spondyloenchondrodysplasia. We further show that an absence of intracellular ISG15 in the patients' cells prevents the accumulation of USP18, a potent negative regulator of IFN-α/ß signalling, resulting in the enhancement and amplification of IFN-α/ß responses. Human ISG15, therefore, is not only redundant for antiviral immunity, but is a key negative regulator of IFN-α/ß immunity. In humans, intracellular ISG15 is IFN-α/ß-inducible not to serve as a substrate for ISGylation-dependent antiviral immunity, but to ensure USP18-dependent regulation of IFN-α/ß and prevention of IFN-α/ß-dependent autoinflammation.

Modulation of type I interferon-associated viral sensing during acute simian immunodeficiency virus infection in African green monkeys.

UNLABELLED: Natural hosts of simian immunodeficiency virus (SIV), such as African green monkeys (AGMs), do not progress to AIDS when infected with SIV. This is associated with an absence of a chronic type I interferon (IFN-I) signature. It is unclear how the IFN-I response is downmodulated in AGMs. We longitudinally assessed the capacity of AGM blood cells to produce IFN-I in response to SIV and herpes simplex virus (HSV) infection. Phenotypes and functions of plasmacytoid dendritic cells (pDCs) and other mononuclear blood cells were assessed by flow cytometry, and expression of viral sensors was measured by reverse transcription-PCR. pDCs displayed low BDCA-2, CD40, and HLA-DR expression levels during AGM acute SIV (SIVagm) infection. BDCA-2 was required for sensing of SIV, but not of HSV, by pDCs. In acute infection, AGM peripheral blood mononuclear cells (PBMCs) produced less IFN-I upon SIV stimulation. In the chronic phase, the production was normal, confirming that the lack of chronic inflammation is not due to a sensing defect of pDCs. In contrast to stimulation by SIV, more IFN-I was produced upon HSV stimulation of PBMCs isolated during acute infection, while the frequency of AGM pDCs producing IFN-I upon in vitro stimulation with HSV was diminished. Indeed, other cells started producing IFN-I. This increased viral sensing by non-pDCs was associated with an upregulation of Toll-like receptor 3 and IFN-γ-inducible protein 16 caused by IFN-I in acute SIVagm infection. Our results suggest that, as in pathogenic SIVmac infection, SIVagm infection mobilizes bone marrow precursor pDCs. Moreover, we show that SIV infection modifies the capacity of viral sensing in cells other than pDCs, which could drive IFN-I production in specific settings. IMPORTANCE: The effects of HIV/SIV infections on the capacity of plasmacytoid dendritic cells (pDCs) to produce IFN-I in vivo are still incompletely defined. As IFN-I can restrict viral replication, contribute to inflammation, and influence immune responses, alteration of this capacity could impact the viral reservoir size. We observed that even in nonpathogenic SIV infection, the frequency of pDCs capable of efficiently sensing SIV and producing IFN-I was reduced during acute infection. We discovered that, concomitantly, cells other than pDCs had increased abilities for viral sensing. Our results suggest that pDC-produced IFN-I upregulates viral sensors in bystander cells, the latter gaining the capacity to produce IFN-I. These results indicate that in certain settings, cells other than pDCs can drive IFN-I-associated inflammation in SIV infection. This has important implications for the understanding of persistent inflammation and the establishment of viral reservoirs.

Aicardi-Goutières syndrome harbours abundant systemic and brain-reactive autoantibodies.

OBJECTIVES: Aicardi-Goutières syndrome (AGS) is an autoimmune disorder that shares similarities with systemic lupus erythematous. AGS inflammatory responses specially target the cerebral white matter. However, it remains uncertain why the brain is the most affected organ, and little is known about the presence of autoantibodies in AGS. Here, we aim to profile specific autoantibodies in AGS and to determine whether these autoantibodies target cerebral epitopes. METHODS: Using a multiplex microarray, we assessed the spectrum of serum autoantibodies in 56 genetically confirmed patients with AGS. We investigated the presence of immunoglobulins in AGS brain specimens using immunohistochemistry and studied the reactivity of sera against brain epitopes with proteomics. RESULTS: Serum from patients exhibited high levels of IgGs against nuclear antigens (gP210, Nup62, PCNA, Ro/SSA, Sm/RNP complex, SS-A/SS-B), components of the basement membrane (entactin, laminin), fibrinogen IV and gliadin. Upon testing whether antibodies in AGS could be found in the central nervous system, IgGs were identified to target in vivo endothelial cells in vivo and astrocytes in brain sections of deceased patients with AGS. Using a proteomics approach, we were able to confirm that IgGs in serum samples from AGS patients bind epitopes present in the cerebral white matter. CONCLUSIONS: Patients with AGS produce a broad spectrum of autoantibodies unique from other autoimmune diseases. Some of these autoantibodies target endothelial cells and astrocytes in the brain of the affected patients, perhaps explaining the prominence of neurological disease in the AGS phenotype.

TLR3 deficiency in herpes simplex encephalitis: high allelic heterogeneity and recurrence risk.

OBJECTIVE: To determine the proportion of children with herpes simplex encephalitis (HSE) displaying TLR3 deficiency, the extent of TLR3 allelic heterogeneity, and the specific clinical features of TLR3 deficiency. METHODS: We determined the sequence of all exons of TLR3 in 110 of the 120 patients with HSE enrolled in our study who do not carry any of the previously described HSE-predisposing mutations of TLR3 pathway genes (TLR3, UNC93B1, TRIF, TRAF3, and TBK1). All the new mutant TLR3 alleles detected were characterized experimentally in-depth to establish the causal relationship between the genotype and phenotype. RESULTS: In addition to the 3 previously reported TLR3-deficient patients from the same cohort, 6 other children or young adults with HSE carry 1 of 5 unique or extremely rare (minor allele frequency <0.001) missense TLR3 alleles. Two alleles (M374T, D592N) heterozygous in 3 patients are not deleterious in vitro. The other 3 are deleterious via different mechanisms: G743D+R811I and L360P heterozygous in 2 patients are loss-of-function due to low levels of expression and lack of cleavage, respectively, and R867Q homozygous in 1 patient is hypomorphic. The 3 patients' fibroblasts display impaired TLR3 responses and enhanced herpes simplex virus 1 susceptibility. Overall, TLR3 deficiency is therefore found in 6 (5%) of the 120 patients studied. There is high allelic heterogeneity, with 3 forms of autosomal dominant partial defect by negative dominance or haploinsufficiency, and 2 forms of autosomal recessive defect with complete or partial deficiency. Finally, 4 (66%) of the 6 TLR3-deficient patients had at least 1 late relapse of HSE, whereas relapse occurred in only 12 (10%) of the total cohort of 120 patients. CONCLUSIONS: Childhood-onset HSE is due to TLR3 deficiency in a traceable fraction of patients, in particular the ones with HSE recurrence. Mutations in TLR3 and TLR3 pathway genes should be searched and experimentally studied in children with HSE, and patients with proven TLR3 deficiency should be followed carefully.

Innate immune responses and rapid control of inflammation in African green monkeys treated or not with interferon-alpha during primary SIVagm infection.

Chronic immune activation (IA) is considered as the driving force of CD4(+) T cell depletion and AIDS. Fundamental clues in the mechanisms that regulate IA could lie in natural hosts of SIV, such as African green monkeys (AGMs). Here we investigated the role of innate immune cells and IFN-α in the control of IA in AGMs. AGMs displayed significant NK cell activation upon SIVagm infection, which was correlated with the levels of IFN-α. Moreover, we detected cytotoxic NK cells in lymph nodes during the early acute phase of SIVagm infection. Both plasmacytoid and myeloid dendritic cell (pDC and mDC) homing receptors were increased, but the maturation of mDCs, in particular of CD16+ mDCs, was more important than that of pDCs. Monitoring of 15 cytokines showed that those, which are known to be increased early in HIV-1/SIVmac pathogenic infections, such as IL-15, IFN-α, MCP-1 and CXCL10/IP-10, were significantly increased in AGMs as well. In contrast, cytokines generally induced in the later stage of acute pathogenic infection, such as IL-6, IL-18 and TNF-α, were less or not increased, suggesting an early control of IA. We then treated AGMs daily with high doses of IFN-α from day 9 to 24 post-infection. No impact was observed on the activation or maturation profiles of mDCs, pDCs and NK cells. There was also no major difference in T cell activation or interferon-stimulated gene (ISG) expression profiles and no sign of disease progression. Thus, even after administration of high levels of IFN-α during acute infection, AGMs were still able to control IA, showing that IA control is independent of IFN-α levels. This suggests that the sustained ISG expression and IA in HIV/SIVmac infections involves non-IFN-α products.

Gain-of-function mutations in IFIH1 cause a spectrum of human disease phenotypes associated with upregulated type I interferon signaling.

The type I interferon system is integral to human antiviral immunity. However, inappropriate stimulation or defective negative regulation of this system can lead to inflammatory disease. We sought to determine the molecular basis of genetically uncharacterized cases of the type I interferonopathy Aicardi-Goutières syndrome and of other undefined neurological and immunological phenotypes also demonstrating an upregulated type I interferon response. We found that heterozygous mutations in the cytosolic double-stranded RNA receptor gene IFIH1 (also called MDA5) cause a spectrum of neuroimmunological features consistently associated with an enhanced interferon state. Cellular and biochemical assays indicate that these mutations confer gain of function such that mutant IFIH1 binds RNA more avidly, leading to increased baseline and ligand-induced interferon signaling. Our results demonstrate that aberrant sensing of nucleic acids can cause immune upregulation.