Identification, validation and biological characterisation of novel glioblastoma tumour microenvironment subtypes: implications for precision immunotherapy.

BACKGROUND: New precision medicine therapies are urgently required for glioblastoma (GBM). However, to date, efforts to subtype patients based on molecular profiles have failed to direct treatment strategies. We hypothesised that interrogation of the GBM tumour microenvironment (TME) and identification of novel TME-specific subtypes could inform new precision immunotherapy treatment strategies. MATERIALS AND METHODS: A refined and validated microenvironment cell population (MCP) counter method was applied to >800 GBM patient tumours (GBM-MCP-counter). Specifically, partition around medoids (PAM) clustering of GBM-MCP-counter scores in the GLIOTRAIN discovery cohort identified three novel patient clusters, uniquely characterised by TME composition, functional orientation markers and immune checkpoint proteins. Validation was carried out in three independent GBM-RNA-seq datasets. Neoantigen, mutational and gene ontology analysis identified mutations and uniquely altered pathways across subtypes. The longitudinal Glioma Longitudinal AnalySiS (GLASS) cohort and three immunotherapy clinical trial cohorts [treatment with neoadjuvant/adjuvant anti-programmed cell death protein 1 (PD-1) or PSVRIPO] were further interrogated to assess subtype alterations between primary and recurrent tumours and to assess the utility of TME classifiers as immunotherapy biomarkers. RESULTS: TMEHigh tumours (30%) displayed elevated lymphocyte, myeloid cell immune checkpoint, programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 transcripts. TMEHigh/mesenchymal+ patients featured tertiary lymphoid structures. TMEMed (46%) tumours were enriched for endothelial cell gene expression profiles and displayed heterogeneous immune populations. TMELow (24%) tumours were manifest as an 'immune-desert' group. TME subtype transitions upon recurrence were identified in the longitudinal GLASS cohort. Assessment of GBM immunotherapy trial datasets revealed that TMEHigh patients receiving neoadjuvant anti-PD-1 had significantly increased overall survival (P = 0.04). Moreover, TMEHigh patients treated with adjuvant anti-PD-1 or oncolytic virus (PVSRIPO) showed a trend towards improved survival. CONCLUSIONS: We have established a novel TME-based classification system for application in intracranial malignancies. TME subtypes represent canonical 'termini a quo' (starting points) to support an improved precision immunotherapy treatment approach.

Pembrolizumab in soft-tissue sarcomas with tertiary lymphoid structures: a phase 2 PEMBROSARC trial cohort.

Immune checkpoint inhibitors (ICIs) show limited clinical activity in patients with advanced soft-tissue sarcomas (STSs). Retrospective analysis suggests that intratumoral tertiary lymphoid structures (TLSs) are associated with improved outcome in these patients. PEMBROSARC is a multicohort phase 2 study of pembrolizumab combined with low-dose cyclophosphamide in patients with advanced STS (NCT02406781). The primary endpoint was the 6-month non-progression rate (NPR). Secondary endpoints included objective response rate (ORR), progression-free survival (PFS), overall survival (OS) and safety. The 6-month NPR and ORRs for cohorts in this trial enrolling all comers were previously reported; here, we report the results of a cohort enrolling patients selected based on the presence of TLSs (n = 30). The 6-month NPR was 40% (95% confidence interval (CI), 22.7-59.4), so the primary endpoint was met. The ORR was 30% (95% CI, 14.7-49.4). In comparison, the 6-month NPR and ORR were 4.9% (95% CI, 0.6-16.5) and 2.4% (95% CI, 0.1-12.9), respectively, in the all-comer cohorts. The most frequent toxicities were grade 1 or 2 fatigue, nausea, dysthyroidism, diarrhea and anemia. Exploratory analyses revealed that the abundance of intratumoral plasma cells (PCs) was significantly associated with improved outcome. These results suggest that TLS presence in advanced STS is a potential predictive biomarker to improve patients' selection for pembrolizumab treatment.

Programmed cell death 1 (PD-1) targeting in patients with advanced osteosarcomas: results from the PEMBROSARC study.

PURPOSE: There are some lines of evidence suggesting a potential role of immunotherapy for treating patients with osteosarcomas. PATIENTS AND METHODS: This was an open-label, multicentre, phase 2 study of pembrolizumab in combination with metronomic cyclophosphamide in patients with advanced osteosarcomas. All patients received 50 mg b.i.d. of cyclophosphamide one week on and one week off and 200 mg of intravenous pembrolizumab (every 3 weeks). There was a dual primary end-point, encompassing both the non-progression and objective responses at 6 months per Response Evaluation Criteria in Solid Tumours (RECIST), version 1.1. An objective response rate of 20% and/or a 6-month non-progression rate of 60% were determined as reasonable objectives for treatment with meaningful effect. Correlative studies of immune biomarkers were planned from the patients' tumour samples. RESULTS: Between October 13 2015 and July 3 2017, 17 patients were included. Fifty were assessable for the efficacy end-point. Four patients experienced tumour shrinkage, resulting in a partial response (PR) in one patient (6.7%). The 6-month non-progression rate was 13.3% (95% confidence interval [CI]: 1.7-40.5). The most frequent adverse events were grade I or II nausea, anaemia, anorexia and fatigue. programmed death-ligand 1 (PD-L1) expression rate was low, observed in only 2 cases of 14 with available tumour material. The only patient who experienced PR had a PD-L1-negative tumour. CONCLUSION: Programmed cell death 1 (PD-1) inhibition has limited activity in osteosarcomas. Further studies investigating PD-1 inhibitor in combination with agents modulating the microenvironment are warranted. TRIAL REGISTRATION: This study is registered with ClinicalTrials.gov, number NCT02406781.

Anti-CD20 therapy induces a memory Th1 response through the IFN-γ/IL-12 axis and prevents protumor regulatory T-cell expansion in mice.

The long-lasting clinical response by lymphoma patients to anti-CD20 therapy has been attributed to the induction of an anti-tumor adaptive immunity. We previously demonstrated that a CD4-dependent mechanism is responsible for the long-term protection of CD20(+) tumor-bearing mice by anti-CD20 treatment. Here, we compare tumor immunity in tumor-bearing animals that did or did not receive anti-CD20 treatment. Splenic CD4(+)FoxP3(+) regulatory T cells (Tregs) expanded substantially in untreated mice that exhibited then a reduced survival, whereas Tregs depletion led to long-term survival of the animals, suggesting the establishment of a Treg-dependent immunosuppressive environment after tumor injection. Strikingly, anti-CD20 therapy reversed the initial expansion of Tregs, and was accompanied by a marked increase in the number of Th1 cells, with no detectable change in Th2 and Th17 cell numbers. Interleukin-12 serum level was also increased by the anti-CD20 treatment, and activated myeloid dendritic cells producing interleukin-12 could be detected in lymph nodes of treated animals, while interferon-γ blockade strongly reduced survival. Also, CD4(+) effector memory T cells were evidenced in surviving animals, and the transfer of CD4(+) T cells induced long-term protection. Thus, anti-CD20 therapy promotes strong anti-tumor adaptive immunity, opposes Treg expansion and inhibits tumor cells from maintaining an immunosuppressive environment.

The immune microenvironment: a major player in human cancers.

Cancer is a major public health issue and figures among the leading causes of death in the world. Cancer development is a long process, involving the mutation, amplification or deletion of genes and chromosomal rearrangements. The transformed cells change morphologically, enlarge, become invasive and finally detach from the primary tumor to metastasize in other organs through the blood and/or lymph. During this process, the tumor cells interact with their microenvironment, which is complex and composed of stromal and immune cells that penetrate the tumor site via blood vessels and lymphoid capillaries. All subsets of immune cells can be found in tumors, but their respective density, functionality and organization vary from one type of tumor to another. Whereas inflammatory cells play a protumoral role, there is a large body of evidence of effector memory T cells controlling tumor invasion and metastasis. Thus, high densities of memory Th1/CD8 cytotoxic T cells in the primary tumors correlate with good prognosis in most tumor types. Tertiary lymphoid structures, which contain mature dendritic cells (DC) in a T cell zone, proliferating B cells and follicular DC, are found in the tumor stroma and they correlate with intratumoral Th1/CD8 T cell and B cell infiltration. Eventually, tumors undergo genetic and epigenetic modifications that allow them to escape being controlled by the immune system. This comprehensive review describes the immune contexture of human primary and metastatic tumors, how it impacts on patient outcomes and how it could be used as a predictive biomarker and guide immunotherapies.

Pitfalls in anti-influenza T cell detection by Elispot using thimerosal containing pandemic H1N1 vaccine as antigen.

Monitoring T cells in combination with humoral response may be of value to predict clinical protection and cross-protective immunity after influenza vaccination. Elispot technique which measures cytokine produced after antigen-specific T cell stimulation is used routinely to detect and characterize anti-viral T cells. We found that the preservative thimerosal present in most H1N1 pandemic vaccines, induced in vitro abortive activation of T cells followed by cell death leading to false-positive results with the Elispot technique. The size of the spots, usually not measured in routine analysis, appears to be a discriminative criterion to detect this bias. Multi-dose vials of vaccine containing thimerosal remain important for vaccine delivery and our results alert about false-positive results of Elispot to monitor the clinical efficacy of these vaccines. We showed that this finding extends for other T cell monitoring techniques based on cytokine production such as ELISA. Although measuring in vitro immune response using the whole vaccine used for human immunization directly reflects in vivo global host response to the vaccine, the present study strongly supports the use of individual vaccine components for immune monitoring due to the presence of contaminants, such as thimerosal, leading to a bias in interpretation of the results.

Immune adaptive microenvironment profiles in intracerebral and intrasplenic lymphomas share common characteristics.

A large body of evidence indicates that the immune microenvironment controls tumour development. Primary central nervous system lymphomas (PCNSL) are aggressive tumours growing in the central nervous system (CNS). To evaluate the role and characteristics of this immune-privileged site in anti-tumour defences, we compared the cellular and molecular immune microenvironments of growing murine lymphoma B cells injected into the brain or the spleen. In the brain, immune cells, including dendritic cells and T lymphocytes with a large proportion of CD4(+) forkhead box P3 (FoxP3(+)) regulatory T cells, rapidly infiltrated the tumour microenvironment. These populations also increased in number in the spleen. The T cell cytokine profiles in tumour-bearing mice were similar in the two sites, with predominant T helper type 1 (Th1)/Th17 polarization after polyclonal stimulation, although some interleukin (IL)-4 could also be found. We demonstrated that these T cells have anti-tumour activity in the CNS, although less than in the spleen: nude mice that received lymphoma cells intracerebrally died significantly earlier than immunocompetent animals. These results demonstrate that the brain is able to recruit all the major actors to mount a specific anti-tumour immune response against lymphoma.

Angiogenesis and immunity: a bidirectional link potentially relevant for the monitoring of antiangiogenic therapy and the development of novel therapeutic combination with immunotherapy.

The immune system regulates angiogenesis in cancer with both pro- and antiangiogenic activities. The induction of angiogenesis is mediated by tumor-associated macrophages and myeloid-derived suppressor cells (MDSC) which produce proinflammatory cytokines, endothelial growth factors (VEGF, bFGF…), and protease (MMP9) implicated in neoangiogenesis. Some cytokines (IL-6, IL-17…) activated Stat3 which also led to the production of VEGF and bFGF. In contrast, other cytokines (IFN, IL-12, IL-21, and IL-27) display an antiangiogenic activity. Recently, it has been shown that some antiangiogenic molecules alleviates immunosuppression associated with cancer by decreasing immunosuppressive cells (MDSC, regulatory T cells), immunosuppressive cytokines (IL-10, TGFß), and inhibitory molecules on T cells (PD-1). Some of these broad effects may result from the ability of some antiangiogenic molecules, especially cytokines to inhibit the Stat3 transcription factor. The association often observed between angiogenesis and immunosuppression may be related to hypoxia which induces both neoangiogenesis via activation of HIF-1 and VEGF and favors the intratumor recruitment and differentiation of regulatory T cells and MDSC. Preliminary studies suggest that modulation of immune markers (intratumoral MDSC and IL-8, peripheral regulatory T cells…) may predict clinical response to antiangiogenic therapy. In preclinical models, a synergy has been observed between antiangiogenic molecules and immunotherapy which may be explained by an improvement of immune status in tumor-bearing mice after antiangiogenic therapy. In preclinical models, antiangiogenic molecules promoted intratumor trafficking of effector cells, enhance endogenous anti-tumor response, and synergyzed with immunotherapy protocols to cure established murine tumors. All these results warrant the development of clinical trials combining antiangiogenic drugs and immunotherapy.

A phase II study of the cancer vaccine TG4010 alone and in combination with cytokines in patients with metastatic renal clear-cell carcinoma: clinical and immunological findings.

MUC1 over-expression in renal clear-cell carcinoma (RCC) is associated with poor prognosis. This phase II study determined the efficacy and tolerability of TG4010, a cancer vaccine based on a modified vaccinia virus expressing MUC1 and interleukin-2, in combination with cytokines, as first-line therapy in metastatic RCC. Thirty-seven patients with progressive, MUC1-positive RCC received TG4010 10(8) pfu/inj weekly for 6 weeks, then every 3 weeks until progression, when TG4010 was continued in combination with interferon-α2a and interleukin-2. Assessments included clinical response (primary endpoint), safety, time to treatment failure (TTF), overall survival (OS), and immune response. No objective clinical responses occurred. Five of the 27 evaluable patients (18%) had stable disease for >6 months with TG4010 alone and six of 20 patients (30%) had stable disease for >6 months with TG4010 plus cytokines. Median TTF was 4.1, 3.6, and 9.3 months for monotherapy, combination therapy, and overall, respectively. Median OS was 19.3 months for all patients and 22.4 months combination therapy recipients. The most frequent TG4010-related adverse events were minor-to-moderate injection-site reactions, fatigue, and flu-like symptoms. Six of 28 patients showed a MUC1 CD4+ T cell proliferative response during therapy. Anti-MUC1 CD8+ T cells were detected before and after therapy in 3 and 4 patients, respectively. MUC1-specific CD8+ T cell responses were associated with longer survival. Therapy with TG4010 plus cytokines appears to be feasible and well tolerated in patients with metastatic RCC. However, these data should be interpreted with caution, as additional prospective studies are necessary to clarify the clinical efficacy of this therapy.

Immune infiltration in human tumors: a prognostic factor that should not be ignored.

The natural history of a tumor includes phases of 'in situ' growth, invasion, extravasation and metastasis. During these phases, tumor cells interact with their microenvironment and are influenced by signals coming from stromal, endothelial, inflammatory and immune cells. Indeed, tumors are often infiltrated by various numbers of lymphocytes, macrophages or mast cells. It is generally believed that the latter produce factors that maintain chronic inflammation and promote tumor growth, whereas lymphocytes may control cancer outcome, as evidenced in mouse models. In this study, we analyze data from large cohorts of human tumors, clearly establishing that infiltration of the primary tumor by memory T cells, particularly of the Th1 and cytotoxic types, is the strongest prognostic factor in terms of freedom from disease and overall survival at all stages of clinical disease. We review data suggesting that tertiary lymphoid structures adjacent to tumors and composed of mature dendritic cells (T and B cells organized as germinal centers) may be the site of an antitumor reaction. We propose an immune scoring based on the type, density and location of lymphocyte infiltrates as a novel prognostic factor for use in addition to tumor node metastasis staging to predict disease-free survival and to aid in decisions regarding adjuvant therapies in early stage human cancers.

Anti-Factor H autoantibodies in a fifth renal transplant recipient with atypical hemolytic and uremic syndrome.

Hemolytic uremic syndrome (HUS) associated with anti-Factor H (anti-FH) autoantibodies is a recently described pathophysiological entity. Monitoring of anti-FH IgG titer may be a sensitive marker of disease activity and guide treatment to eliminate circulating anti-FH antibodies. We report here a case of atypical HUS (aHUS) in which anti-FH autoantibodies were detected during the course of a fifth kidney transplant, 30 years after the first flare of aHUS. This exceptional case suggests that early, specific management based on immunosuppressive therapy and plasma exchanges monitored by anti-FH IgG titer may result in long-term graft survival.

The high frequency of complement factor H related CFHR1 gene deletion is restricted to specific subgroups of patients with atypical haemolytic uraemic syndrome.

BACKGROUND: Deletion of the complement factor H related 1 (CFHR1) gene is a consequence of non-allelic homologous recombination and has been reported to be more frequent in atypical haemolytic uraemic syndrome (aHUS) patients than in the normal population. Therefore, it is considered a susceptibility factor for the disease. aHUS is associated with hereditary or acquired abnormalities that lead to uncontrolled alternative pathway complement activation. We tested the CFHR1 deletion for association with aHUS in a population of French aHUS cases and controls. Furthermore, we examined the effect of the deletion in the context of known aHUS risk factors. METHODS AND RESULTS: 177 aHUS patients and 70 healthy donors were studied. The number of CFHR1 alleles was quantified by multiplex ligation dependant probe amplification (MLPA). The frequency of the deleted allele was significantly higher in aHUS patients than in controls (22.7% vs 8.2%, p<0.001). The highest frequency was in the subgroup of patients exhibiting anti-factor H (FH) autoantibodies (92.9%, p<0.0001 vs controls) and in the group of patients exhibiting a factor I (CFI) gene mutation (31.8%, p<0.001 vs controls). The CFHR1 deletion was not significantly more frequent in the cohort of aHUS patients when patients with anti-FH IgG or CFI mutation were excluded. CONCLUSIONS: The high frequency of CFHR1 deletion in aHUS patients is restricted to the subgroups of patients presenting with anti-FH autoantibodies or, to a lesser degree, CFI mutation. These results suggest that the CFHR1 deletion plays a secondary role in susceptibility to aHUS.

Complement mutation-associated de novo thrombotic microangiopathy following kidney transplantation.

Mutations in one or more genes encoding complement-regulatory proteins predispose to atypical hemolytic uremic syndrome (aHUS) and its recurrence following kidney transplantation. We evaluated plasma complement level and performed a screening for mutations in genes encoding complement Factors H and I (CFH, CFI) and membrane cofactor protein (MCP) in 24 kidney transplant recipients experiencing de novo thrombotic microangiopathy (TMA). Six patients presented with low C3 and/or low Factor B levels suggestive complement alternative pathway. A mutation in the CFH or CFI gene was found in 7/24 patients (29%), two of whom had a mutation in both genes. On the contrary, no mutation was identified in a control kidney transplant patients group (n = 25) without TMA. Patients with or without mutations were similar with regard to clinical features. Eight out of 24 patients lost their graft within 1 year of posttransplantation including six patients with a CFH mutation or a decrease of C3 or CFB in plasma. To conclude, kidney transplant patients with de novo TMA exhibit an unexpectedly high frequency of CFH and CFI mutations. These results suggest that genetic abnormalities may represent risk factors for de novo TMA after kidney transplantation and raise the question of the best therapeutic strategy.

[Potential immunologic consequences of lymph node dissection in colorectal cancer]. / Implications immunologiques potentielles du curage ganglionnaire: Exemple du cancer colorectal.

Lymph node dissection is an integral part of the surgical resection of colon cancers; it completes the wide regional resection of tumor and it allows prognostic evaluation through accurate staging. Studies have demonstrated an immune reaction to the tumoral site which attests to an ongoing dialog between the tumor and systemic defenses. The regional lymph nodes constitute an important first line of immune defense where initial host response is initiated or, inversely, they may participate in a local state of immunosuppression. This article reviews current knowledge on intra-tumoral and nodal immune status in colorectal cancers and attempts to evaluate the potential immunologic implications of lymph node dissection.

[Not Available]. / Implications immunologiques potentielles du curage ganglionnaire : Exemple du cancer colorectal.

F. Pagès, A. Berger, F. Zinzindohoué, A. Kirilovsky, J. Galon, W.-H. Fridman Lymph node dissection is an integral part of the surgical resection of colon cancers; it completes the wide regional resection of tumor and it allows prognostic evaluation through accurate staging. Studies have demonstrated an immune reaction to the tumoral site which attests to an ongoing dialog between the tumor and systemic defenses. The regional lymph nodes constitute an important first line of immune defense where initial host response is initiated or, inversely, they may participate in a local state of immunosuppression. This article reviews current knowledge on intra-tumoral and nodal immune status in colorectal cancers and attempts to evaluate the potential immunologic implications of lymph node dissection.

[Not Available]. / Implications immunologiques potentielles du curage ganglionnaire : Exemple du cancer colorectal.

F. Pagès, A. Berger, F. Zinzindohoué, A. Kirilovsky, J. Galon, W.-H. Fridman Lymph node dissection is an integral part of the surgical resection of colon cancers; it completes the wide regional resection of tumor and it allows prognostic evaluation through accurate staging. Studies have demonstrated an immune reaction to the tumoral site which attests to an ongoing dialog between the tumor and systemic defenses. The regional lymph nodes constitute an important first line of immune defense where initial host response is initiated or, inversely, they may participate in a local state of immunosuppression. This article reviews current knowledge on intra-tumoral and nodal immune status in colorectal cancers and attempts to evaluate the potential immunologic implications of lymph node dissection.

Soluble interleukin-2 receptor and metalloproteinase-9 expression in head and neck cancer: prognostic value and analysis of their relationships.

In a series of 84 head and neck patients, a statistically significant correlation was observed between high serum soluble interleukin (IL)-2 receptor alpha (sIL-2Ralpha) (P = 0.034) and metalloproteinase-9 (MMP-9) concentrations (P = 0.036) at diagnosis and a shorter survival of these patients. As MMP-9 has been shown to mediate cleavage of IL-2Ralpha (CD25) by preactivated T cells, we looked for a relationship between MMP-9 expression and soluble IL-2Ralpha serum concentrations in these cancer patients. We did not find any correlation between intratumoral expression of MMP-9 or serum MMP-9 concentrations and serum sIL-2Ralpha levels. These results led us to reassess the role of MMP-9 in the release of sIL-2Ralpha. Treatment of Kit225 leukaemic cells with recombinant MMP-9 slightly decreased membrane CD25 expression and was associated with an increased concentration of sIL-2Ralpha in the supernatants. However, using a selective inhibitor of MMP-9 we did not succeed in specifically inhibiting the release of sIL-2Ralpha by the Kit225 cell line or by phytohaemagglutinin (PHA)-activated peripheral blood mononuclear cells. In addition, in a preclinical mouse model, basal serum sIL-2Ralpha concentrations and sIL-2Ralpha production by activated cells were not altered in MMP-9-deficient mice compared to wild-type mice. Interestingly, a broad spectrum metalloproteinase inhibitor inhibited the release of sIL-2Ralpha by PHA-activated peripheral blood mononuclear cells, suggesting that in contrast with current views concerning the major role of MMP-9 in the cleavage of membrane IL-2Ralpha, other proteases are involved in the shedding of sIL-2Ralpha. MMP-9 and sIL-2Ralpha appear therefore as independent prognostic markers in head and neck cancers.

TRAF4 overexpression is a common characteristic of human carcinomas.

Tumor necrosis factor receptor (TNFR) associated factor 4 (TRAF4) was initially identified as a gene amplified and overexpressed in breast carcinomas. Our aim was to evaluate whether TRAF4 protein overexpression exists in other cancer types. Immunohistochemistry analysis of tumor samples from 623 patients with 20 different tumor types showed that TRAF4 was overexpressed in 268 tumors (43%), including 82 of 137 lung adenocarcinomas (60%). Interestingly, 32 primary tumors and their matching metastases exhibited mostly similar TRAF4 expression pattern. TRAF4 protein overexpression was limited to cancer cells and the subcellular localization was consistently cytoplasmic in a large majority of cases. To investigate changes in TRAF4 gene copy number, 125 cases from six different types of carcinomas were also analysed by fluorescence in situ hybridization. Out of the 28 cases (22%) showing an increased TRAF4 gene copy number, 23 (82%) were overexpressing the protein. Thus, TRAF4 gene amplification is one of the mechanisms responsible for TRAF4 protein overexpression in human cancers. Considering that TRAF4 is located at 17q11.2 in a region of amplification devoid of known oncogenes and is commonly overexpressed in cancer, our data support an oncogenic role for TRAF4.

[Neisseria meningitidis infection. Clinical criteria orienting towards a deficiency in the proteins of the complement]. / Infection par Neisseria meningitidis. Critères cliniques orientant vers un déficit en protéines du complément.

OBJECTIVE: Complement protein deficiency of the classical pathway or in proteins of the alternate pathway is rare but considerably increase the risk of infection with Neisseria meningitidis. The aim of this study was to determine the clinical criteria of the group at risk. METHODS: Retrospective study of the clinical and biological data of patients exhibiting complement protein deficiency associated with one or several N. meningitidis infections. RESULTS: Forty cases were studied, including 35 classical pathway protein deficiencies, with a predominance of C7 deficiency, 3 properdin deficiencies and 2 acquired C3 deficiencies. More than 60% of the patients exhibited recurrent N. meningitidis infections. Serogroups of rare strains were isolated in 50% of cases. Properdin deficiency was associated with a fulminating form in 2 cases out of 3. The age at onset of the first manifestations varied from 2 months to 32 years. CONCLUSION: A deficiency must be systematically searched for in all patients presenting with a N. meningitidis infection before the age of 6 months or after the age of 5 years. Identification of deficient patients permits the proposal of family screening and appropriate prophylaxis, including preventive vaccination.