HIV, The virus that causes AIDS,?

Question

HIV, the virus that causes aids, frequently mutates (it's genetic code is altered). Why does this fact make it difficult to develop a vaccine against the virus?(please be specific)

Answer 1

The ineffectiveness of previously developed vaccines primarily stems from two related factors. First, HIV is highly mutable. Because of the virus' ability to rapidly respond to selective pressures imposed by the immune system, the population of virus in an infected individual typically evolves so that it can evade the two major arms of the adaptive immune system; humoral (antibody-mediated) and cellular (mediated by T cells) immunity. Second, HIV isolates are themselves highly variable. HIV can be categorized into multiple clades and subtypes with a high degree of genetic divergence. Therefore, the immune responses raised by any vaccine need to be broad enough to account for this variability. Any vaccine that lacks this breadth is unlikely to be effective.