My life as a scientist is devoted to working on the hypothesis that severe infectious diseases of children and young adults may result from single-gene inborn errors of immunity. During my PhD, I deciphered mutations in IFNGR1 underlying a narrow susceptibility to mycobacterial infections. I subsequently began working to dissect the antiviral immune response by searching for susceptibility genes responsible for severe viral infections. The high selectivity of the predisposition of patients studied for a single infectious agent has enabled us to expand the concept of new primary immune deficiency (introduced by the study of patients with mycobacterial infections) to these viral diseases. I contributed to show that single-gene mutations in the TLR3-IFN-a/b pathway were associated with herpes simplex encephalitis (HSE), the most common sporadic viral encephalitis in Western countries. After demonstrating this proof-of-principle, I decided to expand my projects on cutaneous viral infections, epidermodysplasia verruciformis, which is characterized by skin-tropic infections by beta-papillomaviruses, but also recurrent herpes infections, and fulminant viral hepatitis, a rare complication of infection with liver-tropic viruses, such as the hepatitis A and hepatitis B viruses, and a lower extent to herpes viruses. I have two major objectives: 1) to pursue the human genetic dissection of these terrible viral diseases and 2) to understand the mechanisms of antiviral immunity against these diseases.