An Overview of SupT1 Cell Infusion Therapy, our Novel Cell-Based Therapy Solution for HIV
HIV infection usually leads to a progressive decline in number and functionality of CD4+ T lymphocytes, resulting in AIDS development. As explained in Jonathan Fior’s papers [1–3], the HIV virus has a higher tropism for SupT1 cells than for primary CD4+ T cells. Several hypotheses have been proposed as an explanation, most notably the higher surface expression of CD4 and CXCR4 receptors in SupT1 cells. In addition, in vitro studies of HIV evolution show that persistent growth in the SupT1 cell line results in a less cytopathic virus with a reduced capacity for syncytium formation, a higher sensitivity to neutralization, improved replication in SupT1 cells and impaired infection of primary CD4+ T cells [4–6]. Accordingly, Jonathan Fior proposed the infusion of irradiated SupT1 cells as a cell-based HIV therapy to exploit the therapeutic potential of these phenomena [1–3]. The rationale behind this approach is that moving infection toward the inoculated cells should prevent infection and depletion of the patient’s own CD4+ T cells and, therefore, AIDS. In such a strategy, SupT1 cells would act as a “decoy target” for the HIV virus to prevent CD4+ T cell depletion as well as to render the virus less cytopathic. As previously mentioned, in vitro studies of HIV evolution show that prolonged replication in SupT1 cells renders the virus less cytopathic and more sensitive to neutralization. Accordingly, replication of the virus in the inoculated SupT1 cells should also have a vaccination effect; that is, the therapy should also induce the virus to become progressively less aggressive and harmful for the patient. The use of SupT1 cells as a decoy target for HIV has been investigated in vitro and in vivo, with interesting results [1,3]. In vitro data showed that, when primary CD4+ T cells are infected with HIV in the presence of SupT1 cells, the preferential infection of SupT1 cells can spare primary CD4+ T cells from infection and depletion. In vivo data in humanized mice showed that significantly lower viral replication (~10-fold) and potentially preserved CD4+ T cell frequency at Week 1 was scored in animals treated with SupT1 cell infusion. Of note, one animal exhibited a sustained decrease in HIV replication and CD4+ T cell depletion (no virus detected anymore at Weeks 3 and 4), a result that may hold the key to future HIV treatments. Given the urgent and global need for a cost effective cure for HIV, we believe that the millions of people infected by this terrible disease deserve highly innovative HIV cure research strategies, such as SupT1 cell infusion therapy.
In summary, these are some of the potential therapeutic benefits of this cell-based treatment that go beyond what can be achievable with traditional antiretroviral therapy (cART):
1)The vaccination effect. As previously mentioned, SupT1 cells have been shown to have a very powerful vaccination effect in vitro [4–6]. In this regard, in vitro studies of HIV evolution showed that upon prolonged replication in SupT1 cells, the X4 HIV-1 LAI virus evolves toward a less virulent phenotype with a reduced capacity for syncytium formation, thus losing the main cytopathic feature characterizing X4 strains, and most notably the virus adaptation to replicate in SupT1 cells results in gradually losing the ability to replicate in primary CD4+ T cells . In addition, the variation to neutralization sensitivity after viral growth in tumor T cell lines has also been examined. Interestingly, one study reported that primary isolates that were initially resistant to neutralization acquired sensitivity to neutralization after continuous growth in tumor T cell lines, and that the sensitivity to neutralization progressively increased during the days of culturing . Specifically, it was shown that after 14 days in continuous culture, 100 micrograms/mL of rsCD4 (recombinant soluble CD4) were needed to neutralize 1 TCID of primary isolate, while only 0.3 micrograms/mL of rsCD4 were needed to neutralize 1 TCID of the virus after 75 days in continuous culture. This means that there was a 300 fold increase in virus sensitivity to neutralization after prolonged replication in a tumor T cell line, which is really something remarkable. All these phenomena could therefore harbor a significant therapeutic potential that could be exploited with SupT1 cell infusion therapy to induce HIV infection to evolve into a more tractable state for therapy.
2)Potentially no organ toxicity; cART is a drug based treatment and as such is associated with organ toxicity because the drugs are metabolized by various organs. By contrast, SupT1 cell infusion is a cell-based treatment and there is no chemical substance injected into the body that needs to be metabolized, which could significantly improve the quality of the patient's life.
3)Be effective in patients in a terminal state of disease that developed drug resistant and very aggressive HIV strains. When a patient is treated with cART, the virus fights back because it strives to survive, which can result in the development of very aggressive and drug resistant HIV strains, especially in the terminal stage of the disease and in such cases cART becomes ineffective. By contrast, SupT1 cell infusion therapy provides the virus with a permissive cell-line in which it can preferentially replicate, so that a peaceful coexistence between virus and host becomes possible, which could dramatically improve the patient's health as the virus infection progressively moves toward the inoculated SupT1 cells and the virus becomes increasingly less pathogenic for its host.
4)Possible association of the treatment with novel molecular compounds such as a Vif-inhibitor to act on HIV reservoirs. The HIV-1 Vif protein is essential for viral replication in primary CD4+ T cells but not in SupT1 cells . Accordingly, pharmacologic inhibition of Vif could be combined with SupT1 cell infusion to further restrict viral replication to the inoculated SupT1 cells. Considering that APOBEC3G is expressed by different cell types, such as neuronal cells, astrocytes, and macrophages , pharmacologic inhibition of Vif may also have the benefit of acting on HIV reservoirs in the brain and other body areas. There are several molecules with promising anti-Vif activity currently being tested . Similarly, other HIV-1 accessory proteins that are not essential for replication in SupT1 cells (e.g., Vpr, Vpu, and Nef ) may also be the target of pharmacologic inhibition. It is important to point out that these drugs would not affect virus replication in the inoculated SupT1 cells, and therefore in combination with SupT1 cell infusion therapy, there should not be development of drug resistance normally associated with drug based treatments.
5)A cost effective AIDS cure solution. Our mission is to provide a cost effective cure solution for AIDS. In contrast with traditional cell-based and gene-based therapies that make use of modified autologous cells and are therefore very expensive and often unpractical for a large scale application, using a standardized T cell line such as the SupT1 cell line should significantly reduce the treatment costs associated with SupT1 cell infusion therapy, allowing access to the therapy where access to traditional HIV therapies is restricted by economic and social limitations. The social and economical impacts of a low cost HIV cure solution would be enormous.
Below some considerations with regard to potential issues:
1)Safety. We take this issue very seriously and are committed to performing very rigorous preclinical research to ensure there is enough data on safety to obtain approval from regulatory agencies for human experimentation. In this regard, injection of irradiated tumor cells as a therapy is already performed in cancer vaccination. In such cases, irradiating the cells prior to inoculation has been shown to ensure treatment safety both in animal and clinical studies . We used the same protocol used in cancer vaccination studies (i.e., 30 Gy of radiation dose for the cells), which resulted in safe in vivo inoculation in our animal study as well . Specifically, all animals successfully survived the treatment and presence of SupT1 cells was almost undetectable at late time points, which means that irradiating the cells prior to inoculation efficiently prevented SupT1 cell replication. Furthermore, we infused high doses of cells (40 million SupT1 cells were infused weekly), which in a highly immunodeficient mouse strain would rapidly lead to animal death in case of tumor development. Therefore, based on the clinical data we already have from cancer vaccination studies, and from the results of our first animal study, we believe that meeting the safety standards required for human trials is something feasible.
2)Rejection issues. Tumors can develop because tumor cells are able to evade immune recognition. For example, SupT1 cells do not express HLA-DR, which is an antigen highly associated with immune recognition . Accordingly, given the tumoral nature of SupT1 cells, they should be significantly less immunogenic than normal cells and as such should survive in the patient long enough to provide a therapeutic effect. However, it is possible that the HIV virus will eradicate the cells faster and more efficiently than the immune system itself in any case.
1. Fior J. An initial in vitro investigation into the potential therapeutic use of SupT1 cells to prevent AIDS in HIV-seropositive individuals. PLoS ONE. 2012;7:13.
2. Fior J. Is a pacific coexistence between virus and host the unexploited path that may lead to an HIV functional cure? Viruses. 2013;5:753–757.
3. Fior, J. SupT1 Cell Infusion as a Possible Cell-Based Therapy for HIV: Results from a Pilot Study in Hu-PBMC BRGS Mice. Vaccines. 2016, 4:13.
4. Das, A.T.; Land, A.; Braakman, I.; Klaver, B.; Berkhout, B. HIV-1 evolves into a nonsyncytiuminducing virus upon prolonged culture in vitro. Virology. 1999, 263:55–69.
5. Turner, S.; Tizard, R.; DeMarinis, J.; Pepinsky, R.B.; Zullo, J.; Schooley, R.; Fisher, R. Resistance of primary isolates of human immunodeficiency virus type 1 to neutralization by soluble CD4 is not due to lower affinity with the viral envelope glycoprotein gp120. Proc. Natl. Acad. Sci. USA. 1992, 89:1335–1339.
6. Moore, J.P.; Burkly, L.C.; Connor, R.I.; Cao, Y.; Tizard, R.; Ho, D.D.; Fisher, R.A. Adaptation of two primary human immunodeficiency virus type 1 isolates to growth in transformed T cell lines correlates with alterations in the responses of their envelope glycoproteins to soluble CD4. AIDS Res. Hum. Retroviruses. 1993, 9:529–539.
7. Salgia R, et al. Vaccination with irradiated autologous tumor cells engineered to secrete granulocyte-macrophage colony-stimulating factor augments antitumor immunity in some patients with metastatic non-small-cell lung carcinoma. J. Clin. Oncol. 2003, 21:624–630.
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