The mosquito-borne Zika virus (ZIKV) is one of the most feared viruses for pregnant women. Recent statistics justify this fear: Infants born to mothers infected with ZIKV during pregnancy face a risk of up to 42 percent of developing birth defects, including microcephaly (an abnormally small head and decreased brain volume).
What do we know about how ZIKV causes damage to the developing brain?
ZIKV is a Baltimore class IV virus. Based on this classification, what do you know about the structure of its genome?

Verified step by step guidance

1. Understand the Baltimore classification system: The Baltimore classification categorizes viruses based on their genome type and replication method. There are seven classes, each with distinct characteristics.
2. Identify the class of Zika virus: ZIKV is classified as a Baltimore class IV virus. This classification provides specific information about its genome and replication strategy.
3. Determine the genome type of class IV viruses: Baltimore class IV viruses have a single-stranded RNA genome that is positive-sense (+ssRNA). This means their RNA can directly serve as mRNA for protein synthesis.
4. Explain the replication process: The positive-sense RNA genome of class IV viruses can be directly translated by the host cell's ribosomes to produce viral proteins. This is a key feature that distinguishes them from other classes.
5. Discuss the implications for the developing brain: The ability of ZIKV to rapidly produce proteins and replicate within host cells, including neural progenitor cells, can lead to cell damage and death, contributing to developmental issues such as microcephaly.

Key Concepts

Zika Virus and Birth Defects

Zika virus (ZIKV) is known for its severe impact on pregnant women, as it can lead to birth defects such as microcephaly in infants. Microcephaly is characterized by an abnormally small head and reduced brain volume, which can result in developmental issues. The virus targets neural progenitor cells, disrupting normal brain development during pregnancy.

Baltimore Classification System

The Baltimore classification system categorizes viruses based on their genome type and replication method. ZIKV is a class IV virus, meaning it has a single-stranded RNA genome that acts directly as mRNA. This allows the virus to be immediately translated into proteins upon infection, facilitating rapid replication and spread within the host cells.

Structure of ZIKV Genome

As a Baltimore class IV virus, ZIKV possesses a positive-sense single-stranded RNA genome. This RNA can be directly translated by the host's ribosomes into viral proteins, bypassing the need for transcription. The genome encodes structural proteins essential for virus assembly and non-structural proteins that aid in replication and immune evasion.