USP18 and HIV-1 infection: Overall, we provide evidence that ISG15 and USP18 are factors that significantly contribute to HIV-1 infection in innate myeloid THP-1 cells by affecting misfolded p53 accumulation and relieving p21 of its inhibitory function, underlining that ISG15 conjugation to p53 is important for the in vivo clearance of misfolded dominant negative p53.