Impact of Recombinant Human Growth Hormone on HIV Persistence

Antiretroviral therapy (ART) has dramatically reduced the death rate from AIDS and improved the quality of life of many HIV-infected individuals. However, ART does not eradicate HIV as demonstrated by the rapid return of viremia whenever treatment is interrupted. The possible long-term toxicity associated with ART, viral resistance, stigma and cost all contribute to the necessity of finding a cure. A sterilizing cure, in which the virus is completely eradicated, would require the elimination of all replication-competent viruses throughout the body. An alternative approach, probably more realistic, would be to aim for a kind of "cancer model" of cure, where an individual would enjoy long-term health in the absence of ART, or a disease "remission", which might be achieved after reducing the amount of residual HIV during ART (the "reservoir") to levels which the immune system can effectively control. This is commonly referred to as a functional cure in which the viral reservoir is naturally controlled by the host. Both forms of cure (sterilizing and functional) would require eliminating, or at least reducing, the reservoirs of HIV infection.

Different types of cells carry persistent HIV in virally suppressed individuals. Although myeloid cells may also contribute to HIV persistence, it is well established that the majority of replication competent viral genomes persist in memory CD4 T cells during ART. In contrast, naïve CD4 T cells are rarely infected in virally suppressed individuals. As a result of their low infection rate, the frequency of naïve cells negatively correlates with the size of the viral reservoir. Therefore, increasing the frequency of naïve cells may actively reduce the size of the latent HIV reservoir.

The thymic activity gradually decreases with age. The production of recent thymic emigrants (RTEs) is drastically reduced in the elderly, resulting in a decrease in the proportion of new naïve cells in the CD4 compartment, which is compensated by the proliferation of naïve cells in the periphery. Thus, the stability of the naïve cell pool is ensured by different mechanisms in young and elderly, with a major contribution of the thymus in young people. The study investigators preliminary data indicate that the size of the reservoir as measured by integrated DNA strongly correlates with the age of virally suppressed individuals, with younger individuals displaying a smaller reservoir). Although the mechanism underlying this remarkable association is unknown and likely to be multi-factorial, continued generation of naïve CD4 T cells during ART could lead over time to replenishment of infected memory cells with new uninfected memory cells.

Recombinant human growth hormone (rhGH) administered to ART-treated HIV infected individuals has been found to reverse thymic involution, increase total and naïve CD4 T cell counts and reduce the expression of activation and apoptosis markers. Reconstitution of the thymus in immunosuppressed adults through rhGH hormone treatment restores both HIV-specific cellular and antibody responses. Altogether, these observations suggest that the administration of rhGH may reduce the size of the latent HIV reservoir by 1) increasing the frequency of naïve cells 2) reducing the levels of immune activation and 3) restoring HIV specific immune responses, three parameters that are associated with the size of the latent HIV reservoir.

In clinical trials conducted to date using pharmacologic doses of GH, the most common adverse effects have been arthralgia and edema, both occurring in approximately 35% of patients; and myalgia, which was observed in about 30% of patients on GH. Other less common effects that are believed to be related to GH treatment include increased blood pressure, headaches, hyperglycemia and diabetes, enlargement of male breast tissue, carpal tunnel syndrome, and pancreatitis. Other, extremely rare, potential side effects that may be related to GH are allergic reactions to GH, idiopathic intracranial hypertension, hypothyroidism, and leukemia. There is conflicting evidence about whether GH increases the occurrence of lymphoma or other cancers in patients infected with HIV.

While participant enrolled in this trial might not benefit directly from the strategy, it is expected that the trial will provide useful information that relates directly to the status of the study participants (HIV infection HIV reservoirs, immunotherapeutic approaches etc.). In addition, study participants enrolled in the trial will receive compensation, clinical monitoring, laboratory monitoring and continued adherence counseling.

The investigators' primary hypothesis is that treatment with recombinant human growth hormone will result in a decrease in the size of the replication competent HIV reservoir in HIV-infected immune-reconstituted individuals. A reduction in the size of the HIV reservoir is unlikely to have any direct clinical benefits for the participants. However, this may contribute, in association with other therapies, to the development of novel strategies to eradicate HIV in the future.