Growth hormone enhances immunity in HIV patients

Growth hormone helps boost the immune system of HIV patients, revealed by researchers. Growth hormone (GH) treatment was associated with increased thymic mass, and increased the number of immune cells HIV patients had circulating in their blood.

Dr Laura Napolitano and colleagues from the Gladstone Institute of Virology and Immunology, San Francisco General Hospital and the University of California carried out this research. It was published in the peer-reviewed medical journal: The Journal of Clinical Investigation.

The study was a randomised crossover trial in 22 HIV-infected adults who were not blinded to the treatment they were receiving in this study. All had been taking anti-retroviral treatment for at least a year and this continued throughout the study. The researchers were interested in whether growth hormone had any effect on the production of T-cells by the thymus gland. T-cells are a group of white blood cells that play an important role in the immune system. HIV targets and destroys T-cells and when the cells reach a critical low level the person is susceptible to certain characteristic infections and is then defined as having AIDS. The activity of the thymus gland can be indicated by measuring the level of a by-product of T-cell production in the blood: circulating TREC (T-cell receptor excision DNA circles).

In the study, participants were allocated to one year of treatment with growth hormone followed by one year of no treatment (control group), or to the opposite sequence. Growth hormone was delivered by daily injections for one year. The effect of the hormone on immune function was assessed by comparing the results of blood tests and scans between the treatment and control groups.

The researchers found that at the end of the first year, treatment with the growth hormone led to an increase in the scanned mass of the thymus. At six months, measures of the level of TREC (T-cell receptor excision DNA circles) in the blood suggested that the increase in mass was due to an increase in production of T-cells. However, at 12 months, the difference between the groups in levels of TREC was not significant.

The growth hormone increased the proportion of CD4+ T-cells, but the treatment had no effect on other immune functions, e.g. natural killer cells, neutrophils, B-lymphocytes. The researchers conclude that their study suggests that immune-based therapies could ultimately be used to increase production of T-cells in people with immunodeficiencies.

The study was funded in part by a grant from the National Institutes of Health in the USA.

Source: Journal of Clinical Investigation, USA

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