Human induced pluripotent stem cell-derived glial cells and neural progenitors display divergent responses to Zika and dengue infections

Zika virus and the nonmicrocephalic fetus: why we should still worry

Zika virus is a mosquito-transmitted flavivirus and was first linked to congenital microcephaly caused by a large outbreak in northeastern Brazil. Although the Zika virus epidemic is now in decline, pregnancies in large parts of the Americas remain at risk because of ongoing transmission and the potential for new outbreaks. This review presents why Zika virus is still a complex and worrisome public health problem with an expanding spectrum of birth defects and how Zika virus and related viruses evade the immune response to injure the fetus. Recent reports indicate that the spectrum of fetal brain and other anomalies associated with Zika virus exposure is broader and more complex than microcephaly alone and includes subtle fetal brain and ocular injuries; thus, the ability to prenatally diagnose fetal injury associated with Zika virus infection remains limited. New studies indicate that Zika virus imparts disproportionate effects on fetal growth with an unusual femur-sparing profile, potentially providing a new approach to identify viral injury to the fetus. Studies to determine the limitations of prenatal and postnatal testing for detection of Zika virus-associated birth defects and long-term neurocognitive deficits are needed to better guide women with a possible infectious exposure. It is also imperative that we investigate why the Zika virus is so adept at infecting the placenta and the fetal brain to better predict other viruses with similar capabilities that may give rise to new epidemics. The efficiency with which the Zika virus evades the early immune response to enable infection of the mother, placenta, and fetus is likely critical for understanding why the infection may either be fulminant or limited. Furthermore, studies suggest that several emerging and related viruses may also cause birth defects, including West Nile virus, which is endemic in many parts of the United States. With mosquito-borne diseases increasing worldwide, there remains an urgent need to better understand the pathogenesis of the Zika virus and related viruses to protect pregnancies and child health.

Viral Encephalitis and Neurologic Diseases: Focus on Astrocytes

Neurotropic RNA virus infections cause a major neurological disease burden. Due to the morbidity and mortality rates of viral encephalitides worldwide, there is a need to develop clinical treatments. Features of the central nervous system (CNS), including interconnected cell types and limited regeneration, provide unique challenges. Viral encephalitis and antiviral immunity can disrupt the CNS environment, leaving patients with poor neurological outcomes despite virologic control. The cellular mechanism(s) underlying neurological recovery are not fully understood, but involve neuroimmune interactions that, until recently, primarily focused on microglia. With increasing evidence that astrocytes also have significant roles in inflammatory responses to viruses, here we summarize recent astrocyte contributions to acute virologic control and neurological impairments during recovery from viral infection.