IFNA1 and infection: Previous studies show that female sex is more susceptible to intrauterine HIV infection.40 Women are infected by viruses of lower replication capacity in utero than men, but have a higher interferon (IFN) expression and accelerated antiviral immune response to the virus, which is IFN-resistant.40 The possible mechanism underlying this increased female susceptibility is that the sex difference in in-utero infection is most marked in the setting of recent maternal infection.