Treatment as the best prevention for HIV

In this Ask the Experts feature, Infectious Disease News Editorial Board member Paul A. Volberding, MD, examines how recent trial results are affecting how HIV is treated.

There is a growing body of evidence that points to treatment as the best preventive measure against HIV. What are your thoughts on this?

It’s increasingly obvious that this is an infectious disease and that the treatment of the infection is not only good for the person but also will decrease the risk of transmission of all sorts. Basically, we should have known this for a long time, beginning with our experience with post-exposure prophylaxis and the treatment of pregnant women with azidothymidine (AZT) and minimally active drugs. That was enough in both of those cases to decrease the risk of transmission by about 75%. So it’s kind of no surprise that as we have better drugs and much more potent and much less toxic drugs, that we are finding ways to apply them to a broader prevention strategy and that they are proving to be incredibly effective.

What are the implications of the CAPRISA 004 trial results indicating that women who reported using tenofovir-based microbicide gel at least 80% of the time that they had intercourse had a 54% lower rate of HIV infection?

In the prep study, if you look at the evidence of adherence, those who were adherent to tenofovir were essentially completely protected. As for the tenofovir gel, we don’t have that kind of data, so we don’t exactly know how it works in women who are scrupulously adherent, but I wouldn’t be surprised if it were even more effective than in the published results of the study. Both give us, for the first time, the potential for a person at risk to control their own risk status, and that’s tremendously good news.

The CAPRISA study also found that there wasn’t an increase in risky behavior as a result of the higher levels of protection from infection. Either way, should that matter when the treatment’s efficacy has proved so dramatic?

As I understand it, there are always concerns when medications come at the interface of STIs. People raised concerns that penicillin would be disinhibiting of sexual behavior when it was first considered as a treatment for syphilis and gonorrhea. Yes, you change the person’s perception of risk, and there may be behavior consequences, but I approach it as a clinician, and so I don’t think those are reasons not to make these preventive strategies available to people.

How does the recent evidence in favor of treatment affect the search for an effective HIV vaccine?

The problem with not having a vaccine, as I see it, is sustainability. The cost of retrovirals has absolutely plummeted; in many cases, they’re close to zero. If it’s not close to zero, though, then many of these women won’t be able to obtain them. Monitoring them is a huge cost, as well; and for the retrovirals to be effective for as long as we want them to be, we need monitoring in these settings (viral load). But several million people need to be treated forever, and it will be compounded over decades. The cost of this epidemic, as far ahead as we can see, is going to be huge.

So, while CAPRISA is important, it doesn’t replace the need to keep looking for a vaccine. The only way I could imagine controlling this epidemic in a cost-effective way is to have a vaccine. I totally applaud the antiretroviral because that’s all we have, but you’d have to be awfully optimistic to think those programs are going to expand.

Are the specialists who work with microbicides and those who work with oral pre-exposure prophylaxis (PrEp) finding more ways of overlapping their work?

Both fields are happening at the same time, if you will, and those who got involved in microbicides tended to come at their work from a women’s health background, for understandable reasons; although there has been a call to come up with an anal microbicide, as well. The PrEp group comes to their work from an antiretroviral treatment.

Who’s using each and how they’re being used is different, but everyone in this field is working in a collaborative way, and people are talking about common prevention strategies where each of these issues is used together.

How might an ID specialist shortage affect patient care?

That’s the real issue, whether there will be a manpower crunch in terms of clinical care. We want to make sure the needs of the population are met. We hope the lack of general interest in internal medicine as a trend will reverse itself. There are pendulum swings in medicine, and it can swing back and forth. Hopefully, we’ll be on the upswing at some point. Right now, we don’t know. If it all translates into a decreasing manpower pool, then you can visualize fewer ID specialists, so they won’t be available for everybody. It’s still premature to get into horror scenarios. – by Whitney McKnight

Dr. Volberding is chief of medical service at San Francisco Veterans Affairs Medical Center; professor and vice-chair of the department of medicine and co-director of the Center for AIDS Research at the University of California San Francisco. Disclosure: Dr. Volberding is an advisor to BMS and on DSMBs for Gilead, TaiMed, and the NIH.

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