05/03/2023

Zika Virus and Microcephaly

Preparedness for the Zika Virus:A Public Health EmergencyAlex Pollen, Kriegstein LabUniversity of California, San FranciscoMarch 7th 2016

Development of the Human Brain

• Cerebral cortex neurons generated during fetal development (GW8 – GW29)

Radial Glia Generate Cortical Neurons

• Radial glia neural stem cells line the ventricular zone• Generate neurons that migrate to the cortical plate

Lateralventricle

VZ

CP

Microcephaly is a Rare Neurodevelopmental Disorder

Centers for Disease Control and PreventionU.S. Department of Health & Human Services

2-12 cases per 10,000 live births in the US

3 standard deviations below average

2 standard deviations below average

• Intellectual Disability

• Developmental Delay

• Motor Skills Defects

• Vision Problems

• Hearing Loss

Symptoms Associated with Microcephaly

Centers for Disease Control and PreventionU.S. Department of Health & Human Services

Microcephaly Genes Affect Radial Glia Cell Division

Thornton and Woods, Trends in Genetics 2009, Cell Press

Can Viruses Cause Microcephaly?

Can Viruses Cause Microcephaly?Newborn infant with congenital CMV infection

Swanson Pediatr. Clin. North. Am. 2013, W.B.Saunders

• Ventricular calcifications (arrows), pachygyria and lissencephaly, thinning of cortex, and hydrocephalous

Does Zika Virus Cause Microcephaly? – What do we Know?

Associated Press/Felipe Dana

Percio Campos, EPA Associated Press/Felipe Dana

Associated Press/Felipe Dana

Study of 42 Pregnant Women With Zika Virus• Enrolled symptomatic pregnant women, tested for virus using PCR

Brasil et al NEJM 2016

• Fetal abnormalities in 12/42 vs. 0/16 in control group• Death (2), growth defects/microcephaly (5), ventricular calcifications

(7), abnormal amniotic fluid or arterial flow

Zika Virus Detected in Microcephalic Fetal Brain

Mlakar et al NEJM 2016, Massachusetts Medical Society

• Calcifications (arrows)• Smooth brain (arrowheads)

• Flavivirus particles in brain• Zika virus genome detected

Ocular Defects Associated with Congenital Zika Virus Infection

Paramacular chorioretinal atrophy

De Paula Freitas JAMA Ophthalmology 2016

Optic disc hypoplasia

What Cells Does Zika Target During Development?

• We can model aspects of human neurogenesis in vitro

VZ

CP

Zika Virus Likely Infects Neural Progenitors

Tang et al. Cell Stem Cell 2016

Immature neurons exhibited lower levels of infection

Zika Virus Likely Infects Neural Progenitorsand Induces Cell Death

Tang et al. Cell Stem Cell 2016

Infected progenitor cells release infectious viral particles

Infection Reduces the Size of Cerebral Organoid Models

Garcez et al., 2016, PeerJ Preprints

Possible Routes for ZIKV Neuroinvasiveness – Why does virus selectively target neural stem cells?

Associated Press/Felipe Dana

Percio Campos, EPA Associated Press/Felipe Dana

Associated Press/Felipe Dana

Flavivirus Entry Receptors

Perera-Lecoin et al., 2014, MDPI

Several Proteins Promote Zika Virus Entry

Hamel et al, 2015 , J. Virology; Meertens et al., 2012, Cell Host and Microbe

AXLTYRO3

HAVCR1(TIM1)

Virus

Analyzing Gene Expression in Single Cells

Virus

Cellular Resolution “Map” of Gene ExpressionHighlights Vulnerable Cell Populations

Cellular Resolution “Map” of Gene ExpressionHighlights Vulnerable Cell Populations

Hamel et al, 2015 , J. Virology

AXL is necessary and sufficient for Zika virus entry in skin cells

AXL-Expressing Cells in the Fetal Brain

Tom Nowakowski, unpublished

AXL-Expressing Cells in the Fetal Brain

Tom Nowakowski, unpublished

AXL-Expressing Cells in the Fetal Brain

Tom Nowakowski, unpublished

AXL is expressed in the retinal stem cells.

CMZ

Tom Nowakowski, unpublished

Does in vitro System Recapitulate AXL Expression?

Does in vitro System Recapitulate AXL Expression?

Liz Di Lullo, unpublished

Conclusion• Strong published evidence that Zika virus causes

microcephaly and other abnormalities

• Zika virus may target radial glia neural stem cells

• AXL is a strong candidate entry receptor in brain and eye, based on results in skin and CNS expression pattern

Outstanding Questions• What are consequences of virus in larger cohort,

including asymptomatic pregnant women?

• Why is Zika virus associated with microcephaly, when Dengue virus is not?

• Is this new strain of Zika virus different from previous strains?

• How does virus cross placenta and blood-brain barrier?

• Is AXL necessary for viral entry and infectivity in neural stem cells?

Tom Nowakowski Elizabeth Di Lullo Hanna Retallack

Joe DeRisi LabArnold Kriegstein Lab

Jeremy Reiter Lab