With the potent antiretroviral drugs available, why do we still fail to eradicate the virus? The drug is doing great in suppressing virus in the blood. But my understanding is, some research showed that virus hide in lymph system. Why can the drug reach the virus there? Or why do we not deliver the drug to the lymph system? If we manage to do so, would at least suppression possible?

Well -- here's the problem and why we don't know yet how to eradicate HIV from our cells.

Soon after infection, HIV itself becomes a part of the DNA of many cells in the body. Including some cells that are programmed to live a long time. Perhaps as long as we'll be alive. These cells are called long lived memory T cells. They are supposed to live a long time to help our system defend itself against infections that we saw in childhood, and allow us to not get sick even in adulthood. Including old age, whatever age that is... Unfortunately, since HIV knows how to hide inside these cells, HIV appears to be there probably as long as we are. Keep in mind that our current meds do not kill HIV itself -- they just prevent it from growing. So with HIV hiding, the meds are there to prevent it from growing again -- but the meds don't yet have a way to seek out and selectively destroy cells where HIV is hiding. Not yet. Though some are looking for something that might accomplish this...

Hope that clarifies.

CC