Identification of novel innate immunodeficiencies in patients with HSV-2 Mollaret’s meningitis

Dr. Alon Schneider Hait, M.D, Ph.D fellow
Supervision: Prof. Trine H. Mogensen
Department of Infectious diseases, AUH
Department of Biomedicine, Faculty of Health
Aarhus, Denmark

Recurrent benign lymphocytic meningitis (RBLM) is a viral infectious disease of the brain and its covering membranes, caused by herpes simplex virus type 2 (HSV-2) in the majority of reported cases. The disease is characterized by recurrent episodes of headache, photophobia, fever and stiffness of the neck alongside focal and/or diffused neurological deficits. The episodes are self-limited, but the sufferer remains with neurological deficits as consequence of the disease. The pathogenesis of the disease is unknown, and so far, patients remain with insufficient information regarding their disease and its causes.

In this study, we hypothesize that an inborn genetic defect in the patient’s DNA can explain at least part of the disease pathway, by causing the host to react inappropriately to the viral invasion, or to be unable to suppress viral replication in case of reactivation. We believe that differential susceptibility to HSV-2 CNS recurrent infections is explained by host genetics, and in particular mutations found in genes encoding innate immune molecules involved in type I interferon (IFN) production. In this study, we have characterized inclusion criteria for selection of our study group, by collaboration with other medical doctors and medical centers in Europe we have gathered patient cohort suffering from RBLM and after gaining informed consent, we have collected blood from them. DNA from patients’ blood was sent to whole-exome sequencing, a process in which the entire coding region of the person’s DNA is being scanned for genetic variations from the “normal”. The genetics information is thereafter analyzed using state-of-the-art bioinformatic tools, focusing on the very rare (<0.001% in population) and with the higher pathogenicity predictability score (CADD score) to differentiate single nucleotide polymorphisms (SNPs) from true disease-causing mutations.

In parallel to the genetic studies, primary peripheral blood mononuclear cells (PBMCs) were isolated from patient’s whole blood. Functional studies were then performed by infecting the cells with HSV-2 virus and stimulation cells with DNA and RNA mimic molecules to observe their anti-viral and pro-inflammatory response, looking for functional deficiencies. We will also acquire skin fibroblasts from relevant patients and perform in vitro experiments with the cells as done previously by us and other in the field.

Mutations of relevant immune-associated genes identified in patients with viral CNS infection will be characterized further. We will first clone and express the wild-type and mutant molecule in a cell line with no endogenous expression of the relevant protein – generated through CRISPR/Cas9 technology as done previously.

In the end of the study, we will publish and disseminate all information gathered regarding our patients, and if novel genetic defects leading to susceptibility to Mollaret’ meningitis will be found, we will act to recognize MM as PID (primary immunodeficiency disease) by the scientific and medical communities.