” … [Recombinant human interleukin-7] rhIL-7 appears to be an effective T cell growth factor with “immune rejuvenating” properties, suggesting that it is effective in augmenting immune reactivity in hosts with impaired immunity due to any number of factors, including age, chemotherapy, and infectious disease, the authors note. In patients with both intact and deficient immune systems, the capacity of rhIL-7 to augment responses to weak antigens and to increase T cell cycling without expanding T regulatory cells might be clinically exploitable in the context of immunotherapy regimens for cancer and/or chronic infection, they write.”
The results of the phase 1 trial, published online June 23 in The Journal of Experimental Medicine, showed that when given to cancer patients, rhIL-7 induced a dramatic polyclonal prolonged expansion of CD4+ and CD8+ T cells, which in turn caused a significant broadening of circulating T cell receptor repertoire diversity. These effects were mediated primarily through an increase in peripheral T cell cycling and augmented cell survival.
Lymphopenia induced by cytotoxic chemotherapy, or pathologies such as HIV infection, can significantly weaken immune function; as a physiologic immuno-enhancer, IL-7 can enhance the restoration of T cells. CD4+ T cell recovery in adults who have experienced severe depletion requires the reemergence of a pool of naive T cells, which generally takes 18 to 24 months and might only occur in people younger than 40 to 45 years. Thus, the authors note, a strategy that can accelerate or promote the recovery of a widely diverse T cell repertoire in older people might be useful for a large number of clinical applications.
‘We know that IL-7 can enhance tumor vaccines in animals, so that would be a clear avenue of research,’ said lead author Claude Sportès, MD, senior staff clinician at the National Cancer Institute‘s Center for Cancer Research, Experimental Transplantation and Immunology Branch, in Bethesda, Maryland. ‘But it wouldn’t only have to be tumor vaccines. Hopefully we will have a trial underway in the not-too-distant future looking at how it can enhance anti-viral and other immunizations, particularly in the elderly.’
Treatment with IL-7 therapy exerted a marked effect on T cell immune reconstitution during preliminary trials with animal models. It also appeared to augment effector and memory responses to vaccination in mice; in preclinical models, IL-7 therapy was able to augment anti-tumor responses that might improve survival when combined with anti-tumor vaccines.
‘In older individuals, therapy with IL-7 could lead to a rejuvenation of the phenotype,’ explained Dr. Sportès in an interview. ‘This in turn can lead to better vaccine responses in general and, in oncology, better tumor vaccine responses.’
The implications for rhIL-7 are potentially vast, and there are many promising therapeutic avenues. ‘But as often happens in medicine,’ he cautioned, ‘things can be very promising at this stage and then fizzle out.’
First Human Trial
In this phase 1 dose-escalation study, the first initiated in a human population, Dr. Sportès and colleagues evaluated the effects of IL-7 therapy on human lymphocytes in 16 patients, between the ages of 20 to 71 years, with nonhematologic, nonlymphoid refractory cancer. The doses, extrapolated from previous mouse and primate studies, were 3, 10, 30, and 60 μg/kg, and were administered by subcutaneous injection every other day for 14 days, for a total of 8 doses.
They found that after a very transient decrease, the numbers of circulating lymphocytes and CD4+ and CD8+ T cells increased in a dose-dependent manner. At the highest dose levels, increases approached 300% for CD4+ and exceeded 400% for CD8+ T cells. Overall, the treatment induced widespread T cell cycling and was able to expand the T cell pool in human patients while preserving T cell function.
Treatment with rhIL-7 also seems to have advantages over rhIL-2, explained Dr. Sportès. The expanded T cells retained significant functional capacity, and the CD4+ T cell expansion was not accompanied by a disproportionate increase in T regulatory cells, a phenomenon that has been observed after rhIL-2 therapy. Previous data have shown that in vivo IL-2 administration in humans has minimal effects on CD8+ T cell numbers, whereas rhIL-7 effects on CD8+ T cell expansion are at least comparable to the effects on CD4+ T cells.
The researchers noted that rhIL-7 increases T cell receptor repertoire diversity, and that although it appears to selectively expand CD4+ recent thymic emigrants, naive cells, and central-memory populations, it did not have the same effect on effector T cells.
The details of the clinical trial will be the focus of a separate paper, said Dr. Sportès. ‘But it was well tolerated and we went to full-dose escalation.’
“Immune Rejuvenating” Properties
rhIL-7 appears to be an effective T cell growth factor with “immune rejuvenating” properties, suggesting that it is effective in augmenting immune reactivity in hosts with impaired immunity due to any number of factors, including age, chemotherapy, and infectious disease, the authors note.
In patients with both intact and deficient immune systems, the capacity of rhIL-7 to augment responses to weak antigens and to increase T cell cycling without expanding T regulatory cells might be clinically exploitable in the context of immunotherapy regimens for cancer and/or chronic infection, they write.”
[Quoted Source: IL-7 Therapy Boosts Immune Response in Cancer Patients, by Roxanne Nelson, Medscape Medical News, Medscape Today, July 4, 2008 (summarizing the findings of Administration of rhIL-7 in humans increases in vivo TCR repertoire diversity by preferential expansion of naive T cell subsets; Sportes, C. et. al., J Exp Med. 2008 Jun 23. Epub ahead of print]