The Astrocyte Type I Interferon Response is Essential for Protection Against Herpes Simplex Encephalitis

Innate immune activation by central nervous system (CNS) resident cells is critical for controlling HSV-1 replication.…

The c-Rel transcription factor limits early interferon and neuroinflammatory responses to prevent herpes simplex encephalitis onset in mice

Herpes simplex virus type 1 (HSV-1) is the predominant cause of herpes simplex encephalitis (HSE), a condition characterized by acute inflammation and viral replication in the brain. Host genetics contribute to HSE onset, including monogenic defects in type I interferon signaling in cases of childhood HSE. Mouse models suggest a further contribution of immune cell-mediated inflammation to HSE pathogenesis. We have previously described a truncating mutation in the c-Rel transcription factor (RelC307X) that drives lethal HSE in 60% of HSV-1-infected RelC307X mice. In this study, we combined dual host-virus RNA sequencing with flow cytometry to explore cell populations and mechanisms involved in RelC307X-driven HSE. At day 5 postinfection, prior to HSE clinical symptom onset, elevated HSV-1 transcription was detected together with augmented host interferon-stimulated and inflammatory gene expression in the brainstems of high-responding RelC307X mice, predictive of HSE development. This early induction of host gene expression preceded pathological infiltration of myeloid and T cells in RelC307X mice at HSE onset by day 7. Thus, we establish c-Rel as an early regulator of viral and host responses during mouse HSE. These data further highlight the importance of achieving a balanced immune response and avoiding excess interferon-driven inflammation to promote HSE resistance.

Toll-like Receptor 3 Deficiency in a Child with Recurrent Infections and Diabetes Mellitus

There are more than 400 different primary immune deficiencies worldwide. Amongst them, patients with humoral immunodeficiency are more common. Most of the innate immune defects, affect the phagocytic system. There are a few cases of toll-like receptor deficiency with innate immune defects, like TLR3 mutations, which usually present with Herpes simplex encephalitis. Herein, we report a two-year old boy with TLR3 deficiency, who was presented with recurrent infections and type one diabetes mellitus.

Next-generation sequencing of cerebrospinal fluid for diagnosis of atypical herpes simplex encephalitis

Objectives Herpes simplex encephalitis (HSE) is one of the most common causes of severe viral encephalitis. The characteristic manifestations of HSE include cerebrospinal fluid with mild cytopenia, dominated by lymphocytes, elevated protein, and normal blood glucose values (3.9–6.1 mmol/L). Although it is not difficult to diagnose classical HSE, diagnosing clinically atypical cases is more difficult. Methods We reviewed the results of next-generation sequencing (NGS) of CSF in a series of patients diagnosed with atypical HSE. Results Four patients lacking classical clinical manifestations of HSE, including no fever, headache, or other typical neurological deficit symptoms, 1–2 × 106 cells/L CSF leucocyte count, and no typical imaging features, were diagnosed with atypical HSE by NGS of CSF. The NGS reads corresponding to herpes simplex virus type 1 ranged from 2 to 13,174. Conclusions Mild HSE may not present with classic frontotemporal lobe syndrome and fever may not be an inevitable symptom in patients with immunosuppression. However, the possibility of HSE should be considered in patients with atypical intracranial infection, and these patients should be tested by NGS.