Understanding the zika virus
Zika virus disease is a mosquito borne disease that has currently become epidemic in the world. The zika virus (ZIKV) is a mosquito borne pathogen that is transferred to human sexually or through the bite of infected Aedes mosquitoes. Pregnant women and women who want to conceive are at higher risk to be infected by zika because the transplacental transmission of zika virus leads to serious brain damage, microcephaly (abnormally small head) and other birth defects to the fetus. Zika virus can also cause a rare autoimmune neurological disorder Guillain-Barre syndrome that affects the chest muscle cells in adult men and results in paralysis.
Zika virus is an enveloped (by lipids and E glycoproteins) single stranded RNA virus that belongs to flavivirus genus (the same genus for West Nile virus and dengue virus). The virus attaches to the host cell receptors by the E glycoprotein and then through endocytosis the viral RNA is released into the host cytoplasm [1]. Then the ZIKV targets the neural stem cells called cortical neural precursors which are responsible for the formation of cerebral cortex (responsible for brain functions) of the brain. These neural stem cells become the factories for the zika viral replication. ZIKV also interferes with gangliosides that are crucial for brain development, neurogenesis, synaptogenesis, synaptic transmission and cell proliferation [2]. Recent research in UCSD using a 3D stem cell based first trimester human brain model revealed that zika virus may cause microcephaly by hijacking human immune system [3]. Zika virus infection in pregnant women stops the neonatal brain development and results in birth of babies with abnormally small head known as microcephaly. UCSD scientists discovered that zika virus activates a cell bound protein TLR3 which is responsible for turning off the genes that are required to develop various human brain parts from the neural stem cells. Binding of TLR3 with the viral RNA results in organoid shrinkage/brain damage (microcephaly) and apoptosis in developing fetuses.
Zika viral infection symptoms include fever and rash conjunctivitis, muscle and joint pain that lasts up to 7 days [4]. Currently there is no permanent treatment for zika virus infection/microcephaly in pregnant women. Recent research by the virologists from KU Leuven in Belgium suggests that an experimental antiviral drug against hepatitis C virus can slow down the zika infection in mice [5]. Also the TLR3 inhibitor is a big future in zika therapeutics.
Brazil became the epicenter of zika outbreak where 5600 cases of confirmed or suspected cases of microcephaly is reported by World Health Organization and the virus is spreading to Latin America and Caribbean.
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