July 11, 2002
L. Al-Harthi and colleagues performed an immunology substudy among patients enrolled in COLA3003 (a study looking at the use of amprenavir, abacavir and 3TC for the treatment of drug-naive HIV-infected patients). Analyses of T-cell subsets, TREC status (T-cell receptor excision circles, a measure of T-cell turnover), and thymic index (CT evaluation of the size of the thymus) were performed in 13 patients participating in the immunology substudy. The study subjects had a good virologic and immunologic response to their antiretroviral regimen. HIV decline was slower in peripheral mononuclear cells than in the plasma. The rise in CD4+ T-cells consisted mostly of memory/primed cells as has been reported previously.
In some patients TRECs and thymic score indices increased post-HAART suggesting that the thymus may play a role in immune recovery. There was considerable variation among individual study subjects, and current understanding of all the factors relating to immune recovery is still incomplete. For example, one patient had almost no thymic tissue yet had a nice increase in TREC levels. HAART decreased activation levels of CD4+ and CD8+ T-cells, but the levels remained above normal after 48 weeks.
The study also looked at additional immunological parameters such as responses to recall antigens. The paper reports that the change in immunologic parameters was not as impressive in this group with a baseline CD4+ count of less than 500 cells/mm3 (mean for the group was 228). From their data they conclude that the level of immune restoration based on HAART alone is greater when treatment is started early (CD4+ count greater than 500 cells/mm3). That conclusion is pure speculation since there was no control group in this study and other studies have shown more positive results regarding immune recovery in patients with lower baseline CD4+ T-cells. Without any control group and with the small number of patients studied here, it is difficult to reach any conclusions from this study.
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