| Summary |
Type I interferon (IFN-α/β) is the first line of defense against viral infection. Mouse models have been pivotal to our understanding of IFN-α/β in immunity, although validation of these findings in humans has not been possible. We investigated a previously healthy child with fatal susceptibility to the live-attenuated measles, mumps and rubella (MMR) vaccine. By targeted resequencing we identified a homozygous mutation in the high-affinity interferon-α/β receptor (IFNAR2), which rendered cells unresponsive to IFN-α/β and led to unrestricted replication of IFN-attenuated viruses. Reconstitution of patient cells with wild-type IFNAR2 restored IFN-α/β responsiveness and viral resistance. Despite the failure to control vaccine viruses, the patient showed no evidence of susceptibility to conventional viral pathogens in vivo and adaptive immunity appeared normal. Human IFNAR2 deficiency therefore reveals an essential role for IFN-α/β in resistance to attenuated viruses, but significant and unexpected redundancy overall in antiviral immunity. |
