Inhibition of HIV replication in vitro by clinical immunosuppressants and chemotherapeutic agents
© Hawley et al.; licensee BioMed Central Ltd. 2013
Received: 23 January 2013
Accepted: 10 May 2013
Published: 14 May 2013
Recent studies have suggested that a functional cure for HIV-1 infection, purportedly resultant from allogeneic bone marrow transplantation, may be possible. Additionally, the first such patient was treated with whole-body irradiation, immunosuppressants, and the chemotherapeutic, cytarabine. However, the precise role of the coinciding medical interventions in diminishing detectable HIV reservoirs remains unstudied.
In this article, we demonstrate that the immunosuppressants, mycophenolic acid and cyclosporine, and the chemotherapeutic, cytarabine, are potent antiretroviral agents at clinically relevant dosages. These drugs strongly inhibit HIV-1 replication in a GFP indicator T cell line and peripheral blood mononuclear cells (PBMC).
Our study suggests that certain clinical immunosuppressants and chemotherapeutic agents may act combinatorially to inhibit HIV infection. Additionally, chemotherapy-mediated cytotoxicity may also affect the stability of viral reservoirs. Thus, further study is needed to examine potential therapeutic value of these interventions in patients.
Materials and methods
Supplementary Materials and Methods can be found in Additional file 1.
In 2009, a report described the first patient (the Berlin patient) to be possibly cured of HIV infection . This HIV patient also presented acute myeloid leukemia, which was treated with allogeneic stem cell transplantation from a donor lacking functional HIV CCR5 coreceptor expression . As of this publication, and four years after removal of Antiretroviral Therapy (ART), the patient exhibits undetectable plasma mRNA and viral reservoirs . This unique case led to the speculation that it is possible to functionally cure HIV through mutagenesis of CCR5 [2, 3].
More recently, two patients in Boston, as was announced at the 19th International AIDS Conference, have undergone similar bone marrow transplantation, with indications of possible diminishment of viral reservoirs . However, the allogeneic hematopoietic stem cells given to the Boston patients were derived from donors that express functional CCR5 receptors. This raises the question in regards to what actually may have caused the decay of viral reservoirs in the Berlin patient. Common procedures among these patients include whole-body irradiation, chemotherapy, and immunosuppressant treatment, and it is possible that some of these procedures may have contributed to reduction of viral reservoirs [1, 2]. Significantly, as the invasiveness of bone marrow transplantation renders it inapplicable for most HIV patients, illustration of the clinical benefits of these pharmacological interventions may lead to a novel methodology for HIV reservoir elimination.
To further confirm these results in primary blood cells, we isolated PBMCs from healthy donors and treated cells with inhibitors to determine inhibition of HIV replication. For HIV infection of PBMC, cells were pre-activated with PHA plus IL-2 for 24 hours. One million cells were treated with each of the reagents for 2 hours, and then infected with HIV-1 for 2 hours in the presence of the reagents. Infected cells were washed and resuspended in 1 ml of fresh medium with PHA plus IL-2, and the reagents added. Inhibition of HIV replication was measured by the decrease of HIV p24 release in the supernatant. As shown in Figure 4B, Cytarabine exhibited inhibition of HIV at all dosages tested. Particularly, it completely inhibited HIV at dosages above 10 μM, dosages that are clinically achievable during chemotherapeutic administration . Mycopheonolic Mofetil exhibited similar inhibition at all indicated dosages (Figure 4C), largely recapitulating previously reported data . Similarly, exquisite inhibition of HIV-1 was attained with cyclosporine at all concentrations tested, including those that were subtherapeutic . We also measured the cytotoxicities of these drugs in PMBC. Cells were identically activated and treated with these drugs, and apoptotic cells were measured by propidium iodide staining. As shown in Figure 4E, high dosages of the chemotherapeutic drug cytarabine showed cytotoxicity in PMBC, whereas the other two drugs have no detectable cytotoxicity at all the dosages tested. The inhibition of HIV replication by cytarabine likely resulted from direct killing of HIV-infected PBMC.
The diminishment of viral rebound exhibited by the Berlin patient, as is currently indicated, likely resulted from the removal of persistent viral reservoirs by some unknown combination of factors; these may include chemotherapy (cytarabine), immunosuppression (antithymocyte globulin, cyclosporine, and MMF), whole-body irradiation, allogeneic stem cell transplantation, and some degree of graft-versus-HIV immunoreactivity . In this paper, we report the potent antiretroviral activity of cytarabine in an indicator T cell line, REV-CEM. Cytarabine also diminished HIV-infected PBMC likely by direct killing of infected cells. Furthermore, we recapitulate findings of the antiretroviral activity of cyclosporine and MMF in PBMC culture. Together, our results indicate that there is a possibility that a combined use of irradiation, drug-mediated immunosuppression, ART, and chemotherapy-induced cytotoxicity may lead to viral suppression and synergistically increased the decay of viral reservoirs. The therapeutic potential of these treatments, in the absence of transplantation, on viral reservoirs deserves further clinical investigation.
We are grateful to the George Mason University Student Health Center for blood donation. This work has been funded by Public Health Service grant 1R01AI081568 from NIAID to Y. W.. T. W. and M. S. were supported in part by the generous donations of the donors and riders of the 2010 NYCDC AIDS Ride organized by M. Rosen and Day2 Inc.
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