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? Several lines of evidence suggest that after ZIKV is transmitted to a pregnant woman via the bite of an infected mosquito, the virus then directly infects cells of the placenta, gaining access to the fetal brain.
Following attachment, the virion would most likely enter the placental cell by:
a. Insertion via the mosquito's mouthparts
b. Endocytosis
c. Degrading the cell wall with lysozyme
d. Injection through a hollow, needle-like protein structure

Verified step by step guidance

1. Step 1: Understand the context of the problem. The Zika virus (ZIKV) is transmitted to humans via the bite of an infected mosquito. Once inside the human body, the virus can infect cells, including those of the placenta, potentially gaining access to the fetal brain.
2. Step 2: Review the mechanisms by which viruses typically enter host cells. Viruses often use specific methods to attach to and penetrate host cells, such as endocytosis, injection through specialized structures, or enzymatic degradation of barriers.
3. Step 3: Analyze the options provided in the question. Option (a) refers to insertion via the mosquito's mouthparts, which is not relevant to how the virus enters placental cells. Option (c) mentions degrading the cell wall with lysozyme, but human cells do not have cell walls, only cell membranes. Option (d) suggests injection through a hollow, needle-like protein structure, which is a mechanism used by some bacteria, not viruses.
4. Step 4: Focus on option (b), endocytosis. This is a common method used by viruses to enter host cells. During endocytosis, the virus binds to specific receptors on the cell membrane, triggering the cell to engulf the virus in a vesicle, allowing it to enter the cell.
5. Step 5: Conclude that the most likely mechanism for ZIKV to enter placental cells is endocytosis, based on the biological processes involved in viral infection and the structure of human cells.

Key Concepts

Zika Virus Transmission

Zika virus is primarily transmitted to humans through the bite of infected Aedes mosquitoes. Once in the bloodstream, the virus can cross the placenta, posing significant risks to fetal development. Understanding this transmission route is crucial for grasping how the virus can affect pregnant women and their unborn children.

Endocytosis

Endocytosis is a cellular process where cells engulf external substances, allowing them to enter the cell. In the context of Zika virus infection, the virus can utilize endocytosis to penetrate placental cells, facilitating its access to the fetal brain. This mechanism is vital for understanding how viruses exploit cellular pathways to infect host tissues.

Microcephaly and Birth Defects

Microcephaly is a condition characterized by an abnormally small head and associated developmental issues, often linked to infections during pregnancy, such as Zika virus. The virus can disrupt normal brain development, leading to severe neurological consequences for the infant. Recognizing the implications of Zika virus on fetal health is essential for addressing public health concerns.