Question

1. EU2 and E3 individuals have defective CCR5 membrane receptor protein. They also have the CCR5D32 DNA mutation. Explain the relationship of the defective protein and the DNA mutation.

2. Why is it thought that the CCR5D32 might also afford some level of protection to those exposed to bubonic plague?

Answer 1

1. 2C-C chemokine receptor type 5 (CCR5) is a G-protein coupled receptor most commonly found on T cells, macrophages, dendritic cells, eosinophils and microglia. They are an integral part of the human immune system and are involved in the inflammatory responses. They act as a co-receptor for the Human Immunodeficiency virus (HIV). Thus, CCR5 receptor plays a vital role during the HIV infection.

CCR5D32 or CCR5 Δ32 is a mutated form of CCR5 receptor gene in which there is a 32 base pair deletion causing a stop codon to be inserted prematurely into the gene. This produces a non-functional CCR5 receptor protein. Thus, individuals who have the mutated form of CCR5 i.e CCR5D32 have a non-functional or defective CCR5 receptor protein.

2. It is being hypothesised that the bubonic plague outbreaks in Europe during the middle ages has increased the frequency of the CCR5D32 mutations in the population.

This is providing an advantage to the individual during HIV infection because the virus cannot enter the cells. Thus, an individual with the CCR5D32 mutation is more protected from HIV infection when compared to an individual with wildtype CCR5 gene.