Autoantibodies against specific cytokines in adults with severe mycobacterial infection

Background: Mycobacterium species infection has a major impact in human health. Mycobacterium tuberculosis (TB) causes disease in only 5-10% exposed individuals, this phenomenon indicates that the individual heterogeneity in immune system might play a critical role in human susceptibility to mycobacterial infection. Severe infections caused by less virulent nontuberculous mycobacterium (NTM) are always found acquired immunodeficiency syndrome patients and in primary immunodeficiency children with genetic defect in IFN-gamma-IL-12/23 circuit or NF-kappaB pathway. In adult, the prevalence of mycobacterial infections is increasing with ages, however, the molecular basis of the susceptibility is largely unknown. In clinical, it has been noted that many adult patients suffered from disseminated TB and NTM infection with no obvious immuosuppresion or underlie disease. IFN-gamma-IL-12/23 axis or NF-kappaB pathways might also play crucial roles in adult against mycobacteria. Acquired functional impairment or genetic variants in these pathways might diminish host immune system and cause the predispose to mycobacterial infection in adult, and they couldn’t be diagnosed by clinical routine examination. Base on this hypothesis, we had applied a functional assay to these pathways in patients with mycobacterial infection. In our preliminary functional screening data, we have found 8 patients with disseminated mycobacterial infections who have high affinity, naturally occurred autoantibodies against IFN-gamma. Patients with autoantibodies to different cytokines have been found recently and were predispose to infectious diseases. In literature, autoantibodies to IFN-gammahad found in 14 patients with disseminated NTM and TB infection world-wide. Compared with previous reports, our patients have a specific and very narrow clinical manifestation: 1: high coincident with reactivation of varicella-zoster virus (VZV) and salmonella species infections. 2: no clinical autoimmune phenotype and no other autoantibodies observed. 3: high prevalence of presence of anti-IFN-gamma autoantibodies in our mycobacterial infection patients recruited. Therefore, we plan to address the role of anti-cytokines autoantibodies in adult mycobacterial infection, and using this particular cohort to study the role of IFN-gamma in immune system and infectious diseases in natura. This project has 3 major aims: (1) to identify the defect in response to IFN-gamma, IL-12 and TNF in patients with disseminated NTM or TB infection and characterize the prevalence of anti-cytokine autoantibodies in the disseminated mycobacterial infection. (2) to apply the patients with antoantibodies against IFN-gamma to study the role of IFN-gammain adult human ex vivo, including the hematopoietic cells differentiation and the role of IFN-gammain VZV infection. (3) to identify the genes associated with susceptibility to disseminated NTM infection and anti-cytokine autoantibodies. Methods: This 4-year project consists of four studies. (1) We will enroll adult patients with disseminated NTM and/or TB infections, and the functional test will apply to verify if the patients have defect in or carried the autoantibodies against IFN-gamma, IL-12 and TNF. Patients with autoantibodies to particular cytokine will also been check if they also have autoantibodies against other cytokines. The patient clinical information and examination results (autoimmune, whole blood count) will be collected. (2) We will measure the number of Th (Helper T cells) 1, Th2, Th17, Tc17 and Treg (Regulatory T cells) population in patients’ PBMC. The Th17 related cytokines, IL-17A, IL-17F and IL-22, will be measured in the patients’ whole blood and PBMC in response to BCG and other stimuli. (3) Patients’ cytokines responses in whole blood will be measured in VZV infection model in human. The protect effect of IFN-gamma and the serum from patients will be tested in Vero or neuron cells cytotoxicity assay. (4) We will check the HLA types in patients with anti-cytokine autoantibodies. The possible associated HLA subtype will be future analysied by sequencing from three studying group: disseminated NTM patients with anti-cytokine autoantiboides, isolated NTM patients and healthy controls. Expected Results: We expect that we will find high prevalence of autoantibodies to IFN-gamma in patients with dissemainted NTM and maybe with TB. These patients present unique clinical phenotypes with susceptibility to mycobacteria, salmonella and reactivation of VZV. We expect that patients will have increased of Th17, Tc17 and Treg T cells proportion and the lack of IFN-gamma will reduce immunity against the reactivation of VZV, and these results will illustrate the role of IFN-gamma in adult. Finally, we might identify a specific HLA allele associated with production of autoantibodies to IFN-gamma which might also provide an explanation that why autoantibodies against IFN-gamma is particular found in Asia population. We expect our finding will be a proof-of-principle for studying the Anti-cytokines autoantibodies disease (ACAD) and infectious disease, and lead to new therapeutic strategy to all related ACAD diseases.

Project ID:PG10101-0024
External Project ID:NHRI-EX101-10028SC