A new growth hormone therapy helps boost the immune system of HIV patients, reports The Guardian today. The newspaper goes on to say that the treatment “doubled the number of immune cells HIV patients had circulating in their blood, suggesting it was rebuilding their ailing immune systems”.
The newspaper report is based on a small American study that treated 22 HIV patients and monitored their progress over two years. In this particular group of people, growth hormone seems to increase the levels of circulating CD4+ T-cells, which are important for immune function. However, it isn’t possible to apply the results of this study to other people, the research needs to be extended and any benefits need to be weighed up against the damaging effects of the treatment. Only then will it be clear whether growth hormone should be added to the armoury of treatments for people with HIV.
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. The study was funded in part by a grant from the National Institutes of Health in the USA. 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 this crossover 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.
Participants visited the San Francisco General Hospital (SFGH) Clinical Research Centre (CRC) at the start of the study, at six months and 12 months for a scan of their thymus gland. Blood tests to measure the response of the immune system were performed every one to three months, with a measurement of the level of true T-cells being taken every six months.
The participants who received the control treatment underwent the same regular assessments so that a comparison could be made at the end of the study. In the second year, i.e. when the two groups swapped round, tests on the immune system were performed at three, six and 12 months after discontinuation of growth hormone treatment. There was also a repeat scan of the thymus gland at 24 months.
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.
This small crossover study provides results that will be of interest to the medical and scientific communities. There are key points to bear in mind when interpreting the results:
Growth hormone is a powerful chemical; mostly doing more good than harm.