Hepatitis G Virus Co-Infection Slows Progression from HIV Infection to AIDS: The Potential Role of Cytokines

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The summary below is from the full report titled "Slower Progression of HIV-1 Infection in Persons with GB Virus C Co-Infection Correlates with an Intact T-Helper 1 Cytokine Profile." It is in the 1 July 2003 issue of Annals of Internal Medicine (volume 139, pages 26-30). The authors are G. Nunnari, L. Nigro, F. Palermo, M. Attanasio, A. Berger, H.W. Doerr, R.J. Pomerantz, and B. Cacopardo.

What is the problem and what is known about it so far?

Infection with HIV causes AIDS, a serious illness that interferes with the immune system. People with AIDS lose the ability to fight infection and certain types of cancer. However, many people with HIV infection remain healthy for years before developing AIDS. Hepatitis G virus (also known as GB virus C [GBV-C]) is another virus that, like HIV, is transmitted through contact with the blood of a person who has the infection. Many people who inject illegal drugs, such as heroin, into their blood have GBV-C infection. Unlike HIV, GBV-C does not cause serious illness. In fact, studies show that people who have HIV infection progress to AIDS more slowly if they also have GBV-C infection (co-infection). We do not know how GBV-C slows HIV infection. Some researchers think that GBV-C might interact with the immune system in a beneficial way.

Why did the researchers do this particular study?

To see whether substances called T-helper 1 cytokines differ in patients with HIV and GBV-C co-infection compared with patients with only HIV infection. These cytokines are substances involved in the immune system and are related to the development of AIDS.

Who was studied?

80 patients at a medical center in Italy who had HIV infection but no symptoms in 1989. All of the patients had used injection drugs.

How was the study done?

The researchers examined the study patients every 6 months for up to 8 years. Each examination included blood tests for signs of progression to AIDS (tests called CD4 cell counts and viral load levels) and for levels of T-helper 1 cytokines. The researchers also tested each patient for GBV-C infection. They then compared the development of AIDS and the cytokine levels in people with and without GBV-C co-infection.

What did the researchers find?

Of the 80 HIV-infected patients, 17 also had GBV-C infection. As in previous studies, the patients with both HIV and GBV-C infection progressed to AIDS more slowly than did patients with only HIV infection. However, this study also showed that, over 8 years, levels of the immune substances called T-helper 1 cytokines decreased in patients with only HIV infection but stayed stable in patients who also had GBV-C infection.

What were the limitations of the study?

This was a relatively small study of people from a single geographic area. In addition, it does not prove that GBV-C infection exerts its benefit in people with HIV by influencing cytokine levels.

What are the implications of the study?

This study shows that GBV-C infection is associated with a lack of change in the immune substances called T-helper 1 cytokines in people with HIV infection. These results suggest a possible reason why people with HIV infection progress to AIDS more slowly if they also have GBV-C infection.