S100A4+macrophages facilitate zika virus invasion and persistence in the seminiferous tubules via interferon-gamma mediation

Author summary Zika virus (ZIKV), a flavivirus usually transmitted by mosquito bites, was recently reported to establish long-term infection in testes and consequently to transmit sexually from male to female. To uncover the underlying mechanisms, we characterized the gene expression profile of ZIKV-infected mouse testes and selected S100A4+ macrophages as crucial factors for long-term ZIKV infection in testes. S100A4+ macrophages originate from bone marrow and are susceptible to ZIKV infection. Using ZIKV susceptible mice, we found that ZIKV infection attracted S100A4+ macrophages to accumulate in the testes and differentiate into interferon-gamma-expressing cells. In further experiments, we introduced S100A4+ macrophages-depleted mice and interferon-I/II signaling deficient mice. We demonstrated that interferon-gamma secreted by S100A4+ macrophages induced the tight junction protein Claudin-1 to translocate from the plasma membrane into nuclei, thus increasing the permeability of the blood-testis barrier, an indispensable structure surrounding the seminiferous tubules and protecting spermatogenic cells inside from viral infection and immune attack. Taken together, we proposed a mechanism for the long-term ZIKV infection, in which S100A4+ macrophages not only function as Trojan horses to bring ZIKV into the seminiferous tubules, but also serve as a solid shelter for ZIKV replication even when spermatogenic cells have been largely destroyed by ZIKV infection. Testicular invasion and persistence are features of Zika virus (ZIKV), but their mechanisms are still unknown. Here, we showed that S100A4+ macrophages, a myeloid macrophage subpopulation with susceptibility to ZIKV infection, facilitated ZIKV invasion and persistence in the seminiferous tubules. In ZIKV-infected mice, S100A4+ macrophages were specifically recruited into the interstitial space of testes and differentiated into interferon-gamma-expressing M1 macrophages. With interferon-gamma mediation, S100A4+ macrophages down-regulated Claudin-1 expression and induced its redistribution from the cytosol to nucleus, thus increasing the permeability of the blood-testis barrier which facilitated S100A4+ macrophages invasion into the seminiferous tubules. Intraluminal S100A4+ macrophages were segregated from CD8+ T cells and consequently helped ZIKV evade cellular immunity. As a result, ZIKV continued to replicate in intraluminal S100A4+ macrophages even when the spermatogenic cells disappeared. Deficien