TRIM21 and infection: Moreover, mutants lacking the homologous gene of Hsp70 (Ssa1) showed reduced virulence in mouse infection models, indicating that the cytoplasmic Hsp70 protein produced by Ssa1 on the fungal surface may be involved in inhibiting the production of nitric oxide (NO) in macrophages, which is a key factor in the innate immunity of pulmonary epithelial cells (Zhang et al., 2006; Silveira et al., 2013).