March 9, 2012
GB virus C (GBV-C) is a virus that could help inhibit HIV replication within HIV-infected people, according to several studies presented at CROI 2012.
While it's been suggested in past studies that having GBV-C decreases HIV viral loads, increases CD4+ cell counts and increases survival among HIV-infected individuals, a handful of posters at CROI 2012 sought to confirm this association, and to look into how and why.
GBV-C is an RNA virus identified in the late 1990s. It was originally known as hepatitis G because of its genetic similarities to hepatitis C; however, since it does not cause hepatitis, the name was changed. In fact, studies have failed to link GBV-C to any clinically significant diseases. It is transmitted through sex, intravenous injection and childbirth. Blood products are not routinely screened for GBV-C.
Researchers from California, led by Farnaz Vahidnia of the Blood Systems Research Institute, reviewed data from the Viral Activation Transfusion Study (VATS), a trial that ran from 1994 to 2001 and compared the effects of leuko-reduced versus non-leuko-reduced blood transfusions in HIV-infected transfusion-naive individuals. Using blood samples from that study, the researchers tested for GBV-C before and after transfusion and analyzed how that affected HIV mortality.
Their findings show that having GBV-C "was associated with a significant reduction in mortality among GBV-C co-infected VATS subjects, after adjusting for HAART status, HIV viral load, and CD4 cell count." Moreover, they found that GBV-C acquisition specifically via transfusion was "associated with a significant reduction in mortality in HIV-positive individuals, controlling for HIV disease markers."
Another study, which co-transfected 293 CD4+ cells with specific proteins of GBV-C and HIV, found that GBV-C interferes with the Gag protein in HIV, which "diminishes HIV-1 infection by decreasing HIV-1 assembly, maturation and release which is required for virions to infect a new host cell."
A third study tested blood samples in 324 HIV-infected individuals and found GBV-C in 112 of them. However, the results were a little conflicting. The researchers found that different isolates of GBV-C vary in their ability to inhibit HIV. The researchers could not correlate GBV-C replication itself with inhibiting HIV, but they did identify two amino acids within the E2 protein of GBV-C that may explain the mechanism behind the GBV-C isolates that do inhibit HIV replication.
What does this all mean? For starters, it is intriguing to find a seemingly harmless virus that actually helps inhibit HIV. However, it is important to note that more research needs to be done to uncover exactly how GBV-C inhibits HIV. From there, perhaps new forms of HIV treatment options can be developed.
Warren Tong is the research editor for TheBody.com and TheBodyPRO.com.
Follow Warren on Twitter: @WarrenAtTheBody.
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