Viruses are obligate intracellular parasites; they cannot replicate on their own. To multiply, a virus must first infect a host cell. This process leverages the host cell's machinery for viral reproduction. The specific steps vary depending on the type of virus, but generally involve these key stages:
Stages of Viral Replication
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Attachment: The virus binds to specific receptors on the surface of a host cell. This interaction determines which cell types a virus can infect, defining its host range. This initial step is crucial for successful infection.
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Entry: After attachment, the virus enters the host cell. Methods vary, with some viruses injecting their genetic material, while others are engulfed by the cell.
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Replication: Once inside, the virus uses the host cell's machinery to replicate its genetic material (DNA or RNA) and synthesize viral proteins. This process hijacks the cell's normal functions.
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Assembly: Newly synthesized viral components (genetic material and proteins) are assembled into new virus particles.
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Release: The new viruses are released from the infected cell. This can occur through cell lysis (the cell bursts open), releasing numerous virus particles, or by budding, where new viruses are released individually.
Examples and Insights:
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HIV: HIV, the virus that causes AIDS, targets CD4 cells of the immune system. It uses the host cell’s machinery to replicate and spread throughout the body. Interruption of antiretroviral therapy allows the virus to begin multiplying again. (Source: NIH HIV Life Cycle)
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Lytic and Lysogenic Cycles: Some viruses use different replication cycles. The lytic cycle involves immediate viral replication and cell destruction, whereas the lysogenic cycle integrates the viral genetic material into the host cell's genome, allowing for latency before eventual lytic replication. (Source: National Geographic: Viruses)
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Susceptibility and Host Range: A cell's susceptibility to viral infection is determined by the presence of specific receptors that the virus can bind to. The virus's host range defines the types of cells and species it can infect and reproduce in. (Reference text provided).
The process of viral multiplication is crucial for understanding viral infections and developing antiviral treatments. Understanding how viruses utilize host cells allows for targeted interventions to disrupt the replication process.
