We report here unrelated HSE patients with autosomal recessive (AR) or autosomal dominant (AD) TRIF deficiency. The AR form of the disease is due to a homozygous nonsense mutation, resulting in a complete absence of the TRIF protein. Both the TLR3 and the TRIF-dependent TLR4 signaling pathways are abolished. The AD form of TRIF deficiency is due to a heterozygous missense mutation resulting in a dysfunctional protein. The TLR3 signaling pathway is impaired, whereas the TRIF-dependent TLR4 pathway is unaffected. Both patients however showed reduced capacity to respond to cytosolic double stranded RNA, consistent with recent reports of TRIF’s involvement in the DExD/H-box helicases pathway.

Skin fibroblast cell lines were derived from healthy controls (n=3), patient with deficiencies for TRIF (n=1), MYD88 (n=1), and TLR3 (n=1) and cultured for 4 hours in the presence of IL1B (20ng/ml) or poly I:C (25ng/ml) or left unstimulated for the same length of time.PBMCs (previously frozen) collected from a healthy control (n=1) and patients with deficiencies for TRIF (n=1), and MYD88 (n=1) were cultured together with LPS (10ng/ml) or R848 (3ug/ml) for 2hrs or left unstimulated for the same length of time.