When a Good Treatment has an Ugly Side

If you have herpes then you are probably familiar with the drug acyclovir.  It's an anti-viral agent that is often recommended to patients with HSV2 so that recurrences of active herpes are diminished.  The drug is credited with decreasing the number of times you will have painful breakouts, lowering viral load and helping to minimize (but not prevent) transmission of disease. 

Studies now show that acyclovir can also directly slow down HIV infection by targeting the RT (Reverse Transcriptase) enzyme that features prominently in the disease.  The beneficial effect of the drug is countered by a negative impact, namely promoting the multi-drug resistant HIV variants.

Herpes and HIV are two of the most commonly sexually transmitted diseases worldwide.  We know that herpes and HIV can typically occur in the same individual.  When that happens, the presence of HIV can mean more frequent HSV lesion breakouts.  The presence of HSV can increase the liklihood that HIV will progress to full blown AIDS.

So, of course, to have acyclovir lower the HIV viral load is a very good thing.  It actually reduces HIV replication.  The problem is that it makes the HIV that is present, more likely to evolve into a mutant form of HIV, that is very resistant to the current treatments.  So you trade lower viral load for a situation that is now resistant to treatment - not a good trade off.  Experts are preliminarily convinced that the acyclovir could be indicated and beneficial in HIV patients that don't have HSV2.