Zika Virus Infection in the Developing Mouse Produces Dramatically Different Neuropathology Dependent on Viral Strain.

Zika virus (ZIKV) infection during pregnancy has been causally linked to a constellation of neurodevelopmental deformities in the fetus resulting in a disease termed congenital Zika syndrome (CZS). Here we detail how ZIKV infection produces extensive neuropathology in the developing mouse brain and spinal cord of both sexes. Surprisingly, neuropathology differs depending on viral strain with a French Polynesian isolate producing primarily excitotoxicity and a Brazilian isolate being almost exclusively apoptotic but occurring over a prolonged period that is more likely to produce severe hypoplasia. We also show exposure can produce a characteristic pattern of infection that mirrors neuropathology and ultimately results in gross morphological deformities strikingly similar to CZS. This research provides a valuable mouse model mirroring the clinical course of disease that can be used to test potential therapies to improve treatment and gain a better understanding of the disabilities associated with CZS.SIGNIFICANCE STATEMENT Zika virus (ZIKV) infection during pregnancy has been causally linked to a constellation of neurodevelopmental deformities in the fetus resulting in a disease termed congenital Zika syndrome. Despite its devastating effects, very little is known about how ZIKV infection produces fetal neuropathology. Here we detail the temporal progression of ZIKV infection in the mouse brain and spinal cord resulting in massive neurodegeneration of infected regions. We also report a ZIKV strain from a region of Brazil with high levels of microcephaly (abnormally small head circumference) produces particularly devastating neuropathology.

Resuming the obsolete term "small head": when microcephaly occurs without cognitive impairment.

Microcephaly is defined as a head circumference measurement of 2 or 3 standard deviations below the mean for age and sex. However, distinguishing the value of -2 or -3 standard deviations as a cutoff is relevant in the clinical practice, since the limit of -3 standard deviations is more frequently associated with cognitive impairment. The use of ultrasound scans in pregnancy has allowed the identification of subjects with a measurement of the head circumference at the limit of the cutoff for gestational age, but who do not subsequently show cognitive delay. The same is true for newborns with a -2 to -3 standard deviations cutoff, and without anomalous clinical signs, for which a cognitive delay is not easily diagnosed. In this case, to define an infant as being affected by microcephaly (with a prognosis usually recognized as harmful) may be unnecessarily distressful for parents or caregivers. In the cases mentioned, resuming the word "small head" instead of microcephaly to define such subjects could be more appropriate and more appreciated.

Zika fever.

Zika fever is an arboviral systemic disease that has recently become a public health challenge of global concern after its spread through the Americas. This review highlights the current understanding on Zika virus epidemiology, its routes of transmission, clinical manifestations, diagnostic tests, and the current management, prevention and control strategies. It also delves the association between Zika infection and complications, such as microencephaly or Guillem-Barré syndrome.

Overexpression of VIPR2 in mice results in microencephaly with paradoxical increased white matter volume.

Large scale studies in populations of European and Han Chinese ancestry found a series of rare gain-of-function microduplications in VIPR2, encoding VPAC2, a receptor that binds vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide with high affinity, that were associated with an up to 13-fold increased risk for schizophrenia. To address how VPAC2 receptor overactivity might affect brain development, we used a well-characterized Nestin-Cre mouse strain and a knock-in approach to overexpress human VPAC2 in the central nervous system. Mice that overexpressed VPAC2 were found to exhibit a significant reduction in brain weight. Magnetic resonance imaging analysis confirmed a decrease in brain size, a specific reduction in the hippocampus grey matter volume and a paradoxical increase in whole-brain white matter volume. Sex-specific changes in behavior such as impaired prepulse inhibition and contextual fear memory were observed in VPAC2 overexpressing mice. The data indicate that the VPAC2 receptor may play a critical role in brain morphogenesis and suggest that overactive VPAC2 signaling during development plays a mechanistic role in some forms of schizophrenia.

Maternal exposure to busulfan reduces the cell number in the somatosensory cortex associated with delayed somatic and reflex maturation in neonatal rats.

Busulfan is a bifunctional alkylating agent used for myeloablative conditioning and in the treatment of chronic myeloid leukemia due to its ability to cause DNA damage. However, in rodent experiments, busulfan presented a potential teratogenic and cytotoxic effect. Studies have evaluated the effects of busulfan on fetuses after administration in pregnancy or directly on pups during the lactation period. There are no studies on the effects of busulfan administration during pregnancy on offspring development after birth. We investigated the effects of busulfan on somatic and reflex development and encephalic morphology in young rats after exposure in pregnancy. The pregnant rats were exposed to busulfan (10 mg/kg, intraperitoneal) during the early developmental stage (days 12-14 of the gestational period). After birth, we evaluated the somatic growth, maturation of physical features and reflex-ontogeny during the lactation period. We also assessed the effects of busulfan on encephalic weight and cortical morphometry at 28 days of postnatal life. As a result, busulfan-induced pathological changes included: microcephaly, evaluated by the reduction of cranial axes, delay in reflex maturation and physical features, as well as a decrease in the morphometric parameters of somatosensory and motor cortex. Thus, these results suggest that the administration of a DNA alkylating agent, such as busulfan, during the gestational period can cause damage to the central nervous system in the pups throughout their postnatal development.

Zika Virus Can Strongly Infect and Disrupt Secondary Organizers in the Ventricular Zone of the Embryonic Chicken Brain.

Zika virus (ZIKV) is associated with severe neurodevelopmental impairments in human fetuses, including microencephaly. Previous reports examining neural progenitor tropism of ZIKV in organoid and animal models did not address whether the virus infects all neural progenitors uniformly. To explore this, ZIKV was injected into the neural tube of 2-day-old chicken embryos, resulting in nonuniform periventricular infection 3 days later. Recurrent foci of intense infection were present at specific signaling centers that influence neuroepithelial patterning at a distance through secretion of morphogens. ZIKV infection reduced transcript levels for 3 morphogens, SHH, BMP7, and FGF8 expressed at the midbrain basal plate, hypothalamic floor plate, and isthmus, respectively. Levels of Patched1, a SHH-pathway downstream gene, were also reduced, and a SHH-dependent cell population in the ventral midbrain was shifted in position. Thus, the diminishment of signaling centers through ZIKV-mediated apoptosis may yield broader, non-cell-autonomous changes in brain patterning.

An autopsy case of microencephaly, bizarre putaminal lesion, and cerebellar atrophy with heart and liver diseases.

We reported a 64-year-old autopsy case, showing a unique combination of disorders in visceral organs and brain. She had developmental delay, microencephaly, and facial dysmorphism. She developed sick sinus syndrome and liver cirrhosis. There were no abnormalities in laboratory tests for congenital metabolic errors or anomaly syndromes, including activities of lysosomal enzymes, isoelectric focusing of serum transferrin or array comparative genomic hybridization. She died of cardiorespiratory failure. At autopsy she showed liver cirrhosis and mesangial proliferation. The brain weighed 710 g. Bizarre putaminal changes were found, in which the size of area of putamen in coronal sections was small, aberrant fiber running was increased, and immunoreactivity for tyrosine hydroxylase was reduced. Loss of Purkinje cells was found throughout the cerebellar cortex. She had unreported combination of developmental delay, facial dysmorphism, small brain, bizarre putaminal lesion, cerebellar atrophy, cardiac disease, liver cirrhosis and renal disease. Although the exact cause of disease still remains to be investigated, it will be a clue for the establishment of new disease entity to accumulate subjects having the similar phenotype.