Final answer:
Alterations in the structure of the CD4 protein receptor can affect the ability of HIV to enter human cells by preventing viral binding or interfering with fusion. Mutations in other co-receptors, such as CCR5, can also prevent HIV entry.
Step-by-step explanation:
Alterations in the structure of the CD4 protein receptor can affect the ability of HIV to successfully enter human cells. The CD4 protein receptor is present on the surface of T cells, which are an important part of the immune system. HIV binds to the CD4 receptor, which allows the virus to enter T cells and replicate.
If the structure of the CD4 receptor is altered, it may prevent HIV from binding to the receptor or interfere with the fusion of the viral envelope with the cell membrane, thereby reducing or preventing viral entry into T cells. This can limit the ability of HIV to successfully infect human cells and replicate.
For example, some individuals have a mutation in the CCR5 protein, a co-receptor along with CD4, which prevents HIV from entering cells and protects them from infection.