Final answer:
HIV-2 has a lower affinity for CD4 which results in it being less pathogenic compared to HIV-1. It binds less efficiently to the CD4 receptor, leading to a slower disease progression and a less aggressive decline in CD4+ helper T cells.
Step-by-step explanation:
HIV-2 has a lower affinity for CD4 and is therefore less pathogenic.
The Human Immunodeficiency Virus (HIV) targets the immune system by binding to the CD4 receptor, a glycoprotein found on the surfaces of T cells. The variation known as HIV-2, which is concentrated mainly in West Africa, has a reduced ability to bind to the CD4 receptor, leading to a slower progression of the disease it causes, compared to HIV-1. This difference in binding efficiency affects the pathogenicity or the ability to cause disease, which is why HIV-2 is described as being less pathogenic. Infected individuals may thus experience a less aggressive course of the disease, potentially leading to a slower decline in CD4+ helper T cells and a more gradual impairment of immune responses.