Final answer:
As therapy continues, lower concentrations of AZT are required to curtail HIV's replication through blocking the HIV integrase enzyme.
Step-by-step explanation:
As therapy continues in these patients, lower concentrations of AZT are required to curtail HIV's replication. AZT works by blocking the HIV integrase enzyme, which the virus uses to insert its viral DNA into the DNA of the host cell. By inhibiting this process, AZT prevents further replication of the virus.
The introduction of highly active antiretroviral therapy (HAART), which is a combination of drugs, has greatly improved the treatment efficacy by attacking the virus at different stages of its replicative cycle, making it difficult for the virus to quickly develop resistance. Nonetheless, drug-resistant strains and the hidden virus persist as challenges in the treatment of HIV/AIDS, necessitating ongoing drug development.