Animal Viruses: 1. Attachment to the Host Cell: Study with Video Lessons, Practice Problems & Examples

Animal viruses initiate infection by attaching to host cells, a process similar to bacteriophage attachment. This crucial step involves spike proteins on the virus that bind to specific host cell receptors, facilitating entry into the cell. Non-enveloped viruses have spike proteins on their surface, while enveloped viruses feature these proteins protruding from a lipid envelope. Understanding this attachment mechanism is essential for grasping the subsequent stages of viral infection and pathogenesis.

Animal Viruses: 1. Attachment to the Host Cell

In this video, we're going to continue to talk about animal viruses and animal virus infections by talking about the very first step in an animal virus infection, which is attachment to the host cell. And so first, we need to recall from our previous lesson videos that the very first step in a bacteriophage infection was also attachment to the host cell. And so it turns out that animal virus attachment to the host cell is actually really similar to bacteriophage attachment to the host cell. And so it turns out that it relies on protein interactions. And with animal virus infection, attachment involves spike proteins. And so spike proteins on the surface of the animal virus are going to recognize and bind to very specific host cell receptors. And this binding and attachment that the spike proteins on the virus make with host cell receptors is really what allows for the virus to enter the host cell. And entry into the host cell is going to be the second step. And so if we take a look at our image down below, we can get a better understanding of this very first step of an animal virus infection, which is attachment. And again, with this very first step of attachment, this is when the animal virus is going to attach to the surface of the host cell. And so more specifically, it's the spike proteins on the virus that are going to bind to host cell receptors. And so what you'll notice is on the left-hand side of our image over here, what we're showing you is a non-enveloped virus, or a virus that does not have an outer lipid layer. And so this non-envelope virus, which you'll notice is that the spike proteins are right on the coat of this virus. And the spike proteins will interact with receptor proteins on the host cell, and when it binds, that is the attachment stage. Now on the right over here, we're showing you an enveloped animal virus. And the enveloped animal virus has an outer lipid layer, an outer lipid envelope that surrounds the protein coat. And notice that the spike proteins are going to be protruding through to the outside of this envelope, this lipid envelope. And once again, it's the spike proteins that will interact with surface receptors, the host cell receptors here, and that interaction is what allows for attachment. And attachment is necessary for entry, which is the second step of an animal virus infection. And so this here concludes our lesson on the very first step of an animal virus infection: attachment to the host cell. And we'll be able to get some practice and continue to learn more about animal virus infections as we move forward in our course. So I'll see you all in our next video.

The first step of a viral infection is virus ______________, when the spike proteins of the virus attach to the ___________ of the host cell.

• A. Entry; plasma membrane.
• B. Attachment; surface receptors.
• C. Uncoating; DNA.
• D. Assembly; receptor proteins.

An antiviral drug specifically modifies viral receptors on a eukaryotic host cell. How might this affect the viral reproductive cycle?

• A. It would stop the virus from attaching to the host cell.
• B. It would facilitate the process of entry via endocytosis.
• C. It would result in the uncoating of the viral DNA.
• D. It would increase the production of viral proteins by the host cell.

Here’s what students ask on this topic:

What is the first step in an animal virus infection?

The first step in an animal virus infection is the attachment to the host cell. This process involves spike proteins on the surface of the virus recognizing and binding to specific receptors on the host cell. This binding is crucial as it allows the virus to attach firmly to the host cell, facilitating its entry into the cell, which is the subsequent step in the infection process. Understanding this initial attachment is essential for comprehending how viruses invade host cells and initiate infection.

How do spike proteins function in the attachment of animal viruses to host cells?

Spike proteins on the surface of animal viruses play a critical role in the attachment to host cells. These proteins specifically recognize and bind to receptor proteins on the host cell's surface. This interaction is highly specific, ensuring that the virus attaches to the correct host cell type. The binding of spike proteins to host cell receptors is the first step in the viral infection process, enabling the virus to enter the host cell and begin replication.

What is the difference between enveloped and non-enveloped viruses in terms of attachment?

Enveloped and non-enveloped viruses differ in their structure and attachment mechanisms. Non-enveloped viruses have spike proteins directly on their protein coat, which interact with host cell receptors. In contrast, enveloped viruses have an outer lipid envelope surrounding their protein coat, with spike proteins protruding through this lipid layer. Despite these structural differences, both types of viruses use their spike proteins to bind to specific receptors on the host cell, facilitating attachment and subsequent entry.

Why is the attachment step crucial for viral infection?

The attachment step is crucial for viral infection because it determines the virus's ability to enter the host cell. Without successful attachment, the virus cannot penetrate the host cell membrane and initiate the infection process. The specific interaction between viral spike proteins and host cell receptors ensures that the virus attaches to the correct cell type, which is essential for the virus to replicate and propagate within the host organism. This step is a key target for antiviral strategies aiming to block infection.

How do host cell receptors influence the specificity of viral attachment?

Host cell receptors play a significant role in the specificity of viral attachment. These receptors are specific proteins or molecules on the surface of host cells that the viral spike proteins recognize and bind to. The compatibility between the viral spike proteins and the host cell receptors determines which cells a virus can infect. This specificity ensures that viruses attach only to suitable host cells, facilitating efficient entry and infection. Understanding these interactions is crucial for developing targeted antiviral therapies.