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Recombinant GBV-C E2 protein in CD4 count rendered cells tolerant, HIV-resistant
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BOSTON — Recombinant GB virus C, formerly known as hepatitis G, is associated with increased survival among patients with HIV. Additionally, in vitro, GBV-C inhibits HIV replication.
According to Jack T. Stapleton, MD, data demonstrate that adding recombinant E2 protein to cells inhibits HIV entry at the fusion step, and in CD4-positive cells, the expression of E2 leaves them highly resistant to HIV infection. To distinguish the E2 protein domain necessary for the inhibition of HIV, the researchers expressed recombinant E2 protein deletion mutants.
"About 13 years ago, two groups - one in Germany and one in Japan - found that HIV affects people who are coinfected with this virus called GB virus C. At the time, it was called hepatitis G, but 'hepatitis G' has been dropped because the virus doesn't cause hepatitis," Stapleton explained during a press conference here. "Along with several other groups, we confirmed this in large cohorts; although some studies didn't find it, every study that shows persistent infection over time of GB virus C has shown a survival benefit. So, we've been working to understand why this works and why this virus improves survival in people with HIV, with the ultimate goal of coming up with the mechanisms by which it works and might be used for therapeutic reasons."
The researchers transfected Jurkat cell lines with plasmids containing GBV-C E2 sequences followed by an EMC IRES directing GFP expression, according to Stapleton. They prepared cells expressing E2 peptides in the entire protein, with the exception of the C-terminal transmembrane domain and a series of N- and C-terminal deletions. Control cell lines that expressed GFP only or GBV-C RNA that encodes E2 with a frameshift introduced so that no protein was expressed, Stapleton said.
All cell lines expressing a GBV-C E2 region of 17 amino acids demonstrated inhibited HIV replication. However, this was not the case in E2 expressing cell lines without this motif, according to Stapleton. Similarly, vector control and frameshift cells, as well as cells expressing the 17 E2 amino acids in a scrambled order, did not inhibit HIV. HIV isolates studied represented three Clades; none were inhibited.
Stapleton and colleagues found that inhibition of HIVenv, but not VSVG pseudotyped retroviruses, occurred during virus entry. Adding recombinant E2 to cells inhibited HIV, but adding a synthetic 17mer peptide to cells did not inhibit HIV. On the Jurkat cells, CD4 and CXCR4 were not decreased, demonstrating that the effect was not due to altered HIV co-receptor expression. - by Stacey L. Fisher
For more information:
- Stapleton JT. 450. Presented at: IDSA 49th Annual Meeting; Oct. 20-23, 2011; Boston.
Disclosure: Dr. Stapleton reports no relevant financial disclosures.
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