Adding GM-CSF to Hepatitis B Vaccine Fails to Work
October 25, 2008
People living with HIV are at risk for getting the hepatitis B virus (HBV). They also have a higher risk of HBV disease and death. And although healthy adults infected with HBV have only a 1 in 10 chance of developing the disease, the rate soars to 1 in 4 for people living with HIV.
Although current HBV vaccines protect about 90% of the time, they don't offer the same level of protection for HIV-positive people. To be most effective, the vaccine should be given at higher CD4 counts to help ensure durable protection against the virus. Yet, for those living with HIV, even this does not ensure immunity and not all people with HIV have high CD4 counts at the time of vaccination.
A poster at the joint 2008 ICAAC / IDSA in Washington, DC presented phase II data on an approach to HBC vaccination, an HBV vaccine given with GM-CSF (granulocyte-macrophage colony-stimulating factor). GM-CSF is a protein produced by many immune cells that encourages the immune system to make more of a type of white blood cell to fight infections.
In order to improve the vaccine response for the 48 HIV-positive participants in this phase II study, the researchers did three things. First, they used higher doses of the vaccine. The second was to shorten the dosing schedule from 6 months down to 3, while the third was to add GM-CSF.
All volunteers were over 18 years of age, had CD4s above 200, did not already have hepatitis B or C, and never had an earlier HBV vaccination. Three shots of the vaccine + GM-CSF or vaccine + placebo were given at weeks 0, 4 and 12. A total of 37 were on HIV therapy while 25 of them were undetectable at study start; and 38 were men, 26 were White, 15 were Black and 7 were Hispanic.
Unfortunately, the results showed the group that was given the GM-CSF did not benefit from any added protection over the group with placebo. As well, CD4 counts and HIV viral loads did affect the vaccine responses.
Given that the current HBV vaccines, Recombivax HB, Engerix-B and Twinrix, do not provide the same level of protection for HIV-positive people as they do for HIV-negative, it's important to further explore ways to improve the vaccine's effectiveness in this community. Studies like this one, even with disappointing results, are critical to finding ways to further protect people living with HIV at risk for HBV infection.
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