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HCV and HIV: Similarities, Differences, and Treatment of Co-infection

HCV and HIV: Similarities, Differences, and Treatment of Co-infection

The Centers for Disease Control and Prevention (CDC) estimate that 3.2 million Americans are infected with the hepatitis C virus (HCV), a number three times greater than the number of Americans infected with HIV. A smaller number of people are co-infected with HCV and HIV—an estimated 25% of all persons infected with HIV carry HCV—but these people require highly specialized care provided by a physician or group with extensive experience in the management of both types of infection. Even in the care of specialists, however, the most important question the HIV-infected person diagnosed with concomitant HCV infection and a provider face today is whether to initiate therapy within a few months from now or to wait for the availability (a few years perhaps) of what will most likely be better-tolerated and more efficacious treatment regimens. Here, I offer an overview of the factors to be considered when deciding to begin HCV therapy in an HIV-infected patient.
 
HIV and HCV share a number of similarities, at least epidemiologically. Risk factors for being infected with HCV include:
1. having received a blood transfusion or organ transplant prior to 1992, the year that better testing for HCV became available (compared to 1985 for HIV);
2. having received clotting factor concentrates (treatment for hemophilia) made prior to 1987;
3. current or former injection drug use;
4. having sustained a needle stick injury (as a healthcare worker) involving contact with HCV-contaminated blood

Unlike HIV, however, HCV appears only rarely to be transmitted through heterosexual sex.

There are a number of other important differences between HIV and HCV, many of which have made treating HCV more challenging than treating HIV, despite the much larger HCV-infected population. First, HCV can be quiescent for many decades, whereas HIV typically manifests within 7 to 12 years of infection. Thus, many individuals who are infected with HCV are unaware of their status. Early awareness of HCV infection is important, as 60 to 70 percent of those infected with HCV will develop chronic liver disease, up to 20 percent will develop cirrhosis after 2 to 3 decades, and as many as 5 percent will die of consequences of HCV infection (cirrhosis or liver cancer).1 A second difference between the 2 infections is that in approximately 15 percent of those infected with HCV, the infection will spontaneously clear; spontaneous clearance of HIV never happens. In other words, a positive antibody test for HCV does not necessarily indicate chronic HCV infection or ongoing viremia. A third difference between HIV and HCV is that many of the newer drugs that have shown improved efficacy against HCV are “genotype-specific.” There are at least 6 distinct genotypes of HCV, and more than 50 subtypes have been discovered. Genotype 1 is the most common genotype in the United States and, unfortunately, has been the one most refractory to treatment. Indeed, recommendations for treatment in persons with HCV genotype 1 prescribe combination therapy (with alpha interferon and ribavirin) for twice as long as in those found to have other genotypes.
 
Until recently, individuals co-infected with HIV and HCV genotype 1 have had only about a 20 percent chance of a sustained response, even with the longer duration of therapy. On the other hand, most of the newer drugs for the treatment of HCV (eg, boceprevir, an HCV protease inhibitor) were developed because they have impressive activity against genotype 1.  When bocepravir was added to a one year regimen of alpha interferon and ribavirin, the sustained response rate increased to 60% in HIV/HCV co-infected persons.2 Unfortunately, alpha interferon requires weekly injections and is associated with a high rate of “flu-like” symptoms, and ribavirin also has unpleasant side effects (eg, anemia).
   
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