publié le 27 juillet 2005
IAS : Growth hormone improves CD4 cell count in patients with a poor response to HAART
By Chris Gadd / aidsmap.com
July 27, 2005 — Treatment with human growth hormone can stimulate the elevation of CD4+ cell counts in patients with a poor CD4+ cell count response to antiretroviral treatment, according to a study presented this week at the 3rd International AIDS Society Conference on HIV Pathogenesis and Treatment in Rio de Janeiro, Brazil.
Human growth hormone occurs naturally in the body, where it promotes normal growth and development. However, an artificially produced version of the hormone, called recombinant human growth hormone (rhGH), is used by doctors to treat slow growth in children as well as to stimulate repair after burns or other tissue injury.
Although rhGH is not licensed for use in HIV-positive patients in Europe, studies have shown its benefit in treating HIV-related wasting by stimulating weight gain and increasing lean muscle mass. However, animal studies have also suggested that growth hormone may increase the production of T cells from the thymus gland.
Accordingly, investigators from the AIDS Clinical Trials Group (ACTG) carried out a study to examine the effect of rhGH on the CD4+ cell counts of HIV-positive patients taking HAART.
"Treatment with rhGH is associated with significant increases in total and naive CD4 count compared to HAART alone," they conclude. "This is the first randomized clinical trial to demonstrate immunologic effects of rhGH combined with HAART."
Sixty patients were recruited for the study. All had been on HAART for at least a year, with viral loads below 50 copies/mL, but their CD4+ cell counts had not risen above 350 cells/mm3.
Half of the patients were randomized to take 1.5 mg rhGH daily for 48 weeks, while the remainder took HAART alone for 24 weeks, followed by a 24-week course of 3.0 mg rhGH every day.
The patients taking the lower dose showed a CD4+ cell count increase of 19 cells/mm3 over the first 24 weeks of treatment (P = .03), increasing by a further 36 cells/mm3 during the second 24-week phase (P = .001).
This pattern was also seen when the investigators measured the number of "naive" CD4+ T cells, increasing by a median of 4 cells/mm3 in the first 24-week period (P = .04) and 26 cells/mm3 in the second period (P < .001). Naive T cells are responsible for mounting an immune response against the antigens to which the body has not previously been exposed.
The patients who did not receive rhGH for the first 24 weeks of the study had stable levels of both total and naive CD4+ T cells. However, over their 24-week course of rhGH, total and naive CD4+ cell counts increased by 55 and 23 cells/mm3, respectively, reaching similar levels to the patients on the lower dose by the end of the study (P < .001).
"Treatment with [the 2 doses was] associated with similar increases in total and naive CD4 but the lower dose required longer treatment duration," the researchers conclude.
The investigators found that treatment with rhGH was associated with an increase in the size of the thymus gland in 14 of 20 patients, with similar findings reported in a separate poster presentation at the conference by the same research group. The thymus gland is situated under the breastbone and is responsible for producing new naive T cells in the body.
The patients reported few side effects during the study, leading the investigators to postulate that rhGH could eventually be used as an immune system booster.
However, several questions remain to be answered before these results can be put into practice, including whether the increased CD4+ cell counts are paralleled by an increased ability of the cells to fight infection and whether the effects of rhGH will persist after treatment is stopped. A further obstacle to its implementation as a routine therapy in HIV care is the high cost of its production.
1. Smith KY, Wang R, Bosch R, et al. Treatment with growth hormone leads to improvement in total and na ?ve CD4 lymphocyte recovery in HIV-infected subjects with incomplete immune reconstitution on HAART - preliminary results ACTG 5174. Program and abstracts of the 3rd IAS Conference on HIV Pathogenesis and Treatment ; July 24-27, 2005 ; Rio de Janeiro, Brazil. Abstract TuOa0203.
2. Napolitano LA et al. Growth hormone therapy is associated with increased thymic mass and CD4+ cell recovery in HIV-infected adults : interim results of a randomized prospective study. Program and abstracts of the 3rd IAS Conference on HIV Pathogenesis and Treatment ; July 24-27, 2005 ; Rio de Janeiro, Brazil. Abstract MoPpLB0104.