Question

The glycoprotein adhesion gp120 on HIV must interact with _______ on some immune cells as the first step in the process of infecting the cell.

Short answer

The glycoprotein adhesion gp120 on HIV must interact with the CD4 receptor on some immune cells.

Step-by-step solution

Identify the Receptor

To determine with which molecule the glycoprotein gp120 on HIV interacts, recall the known receptors on immune cells that HIV targets during the infection process.

Associate the Receptor and the Virus

Recognize that the gp120 glycoprotein on HIV specifically binds to the CD4 receptor on the surface of certain immune cells including T helper cells and macrophages.

Conclude the Interaction

Conclude that the interaction of gp120 and the immune cell receptor is a critical step for HIV to infect the cell.

Key concepts

CD4 Receptor

The CD4 receptor is akin to a special lock on the surface of certain immune cells, such as T helper cells and macrophages, which play a pivotal role in orchestrating the body's immune response. These receptors are critical for the immune cells to communicate and activate other parts of the immune system. However, in the context of HIV, the CD4 receptor also becomes a point of vulnerability.

HIV targets these receptors as a means of entry into the immune cells. The virus has evolved to exploit this gateway, which normally functions to aid in immune defense, by bonding strongly with the CD4 receptor, thereby initiating the complex process of viral infection. The interaction between the virus and CD4 receptors is, therefore, a crucial detail to understand when looking at HIV's invasion tactics.

Immune Cell Infection

Once HIV's gp120 glycoprotein secures a connection with the CD4 receptor, the scene is set for the next critical step—immune cell infection. Here, additional molecules, known as co-receptors, come into play, further solidifying the virus's grip on the cell. The virus then fuses with the cell membrane, injecting its genetic material inside.

This usurpation of the cell's machinery diverts resources towards creating new copies of the virus, while the normal functions of the immune cell are compromised or even halted. This infection is particularly insidious because the cells being targeted are responsible for defending the body against pathogens. Thus, HIV systematically weakens the immune system from the inside.

Glycoprotein gp120

The gp120 glycoprotein on HIV is the 'key' in our lock-and-key analogy—it is the viral protein that specifically seeks out and binds to the CD4 receptor of immune cells. This glycoprotein is heavily glycosylated, meaning it's covered with lots of sugar molecules. This 'sugar coat' helps HIV to evade the immune system by disguising itself, making it harder for immune system antibodies to recognize the virus and mount an attack.

Understanding the structure and function of gp120 is crucial for developing strategies to prevent HIV from binding to immune cells, which is a key target in HIV research and treatment development. It is this glycoprotein's precise interaction with CD4 receptors that triggers the conformational changes necessary for HIV to fuse with the host cell.

HIV Infection Process

The HIV infection process begins when HIV uses gp120 to bind to the CD4 receptor on an immune cell. This initial binding is just the start of a multi-step invasion strategy. Following gp120-CD4 receptor interactions, co-receptor binding occurs, leading to a fusion of the viral and cellular membranes. This fusion is the gateway through which HIV enters the cell and integrates its genetic material with the host's DNA.

Once inside, HIV takes over the cell's replication machinery to produce new viral particles. These newly formed viruses then bud out from the host cell, ready to continue the cycle of infection. Due to its complexity and precision, the HIV infection process is a focus of intense scientific study, with the aim of finding effective interrupters that can halt the virus's encroachment and protect the immune system.