Brain Iron Accumulation and the Formation of Calcifications After Developmental Zika Virus Infection

Intracranial calcifications (ICC) are the most common neuropathological finding in the brains of children exposed in utero to the Zika virus (ZIKV). Using a mouse model of developmental ZIKV infection, we reported widespread calcifications in the brains of susceptible mice that correlated in multiple ways with the behavioral deficits observed. Here, we examined the time course of ICC development and the role of iron deposition in this process, in 3 genetically distinct inbred strains of mice. Brain iron deposits were evident by Perls' staining at 2 weeks post infection, becoming increasingly dense and coinciding with calcium buildup and the formation of ICCs. A regional analysis of the brains of susceptible mice (C57BL/6J and 129S1/SvImJ strains) revealed the presence of iron initially in regions containing many ZIKV-immunoreactive cells, but then spreading to regions containing few infected cells, most notably the thalamus and the fasciculus retroflexus. Microglial activation was widespread initially and later delineated the sites of ICC formation. Behavioral tests conducted at 5-6 weeks of age revealed greater deficits in mice with the most extensive iron deposition and calcification of subcortical regions, such as thalamus. These findings point to iron deposition as a key factor in the development of ICCs after developmental ZIKV infection.