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Limited transplantation of antigen-expressing hematopoietic stem cells induces long-lasting cytotoxic T cell responses.

Denning WL, Xu J, Guo S, Klug CA, Hel Z - PLoS ONE (2011)

Bottom Line: Continuous antigen presentation by a limited number of differentiated transgenic hematopoietic cells results in an induction and prolonged maintenance of fully functional effector T cell responses in a mouse model.Majority of HSC-induced antigen-specific CD8+ T cells display central memory phenotype, efficiently kill target cells in vivo, and protect recipients against tumor growth in a preventive setting.Furthermore, we confirm previously published observation that high level engraftment of antigen-expressing HSCs following myeloablative conditioning results in tolerance and an absence of specific cytotoxic activity in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.

ABSTRACT
Harnessing the ability of cytotoxic T lymphocytes (CTLs) to recognize and eradicate tumor or pathogen-infected cells is a critical goal of modern immune-based therapies. Although multiple immunization strategies efficiently induce high levels of antigen-specific CTLs, the initial increase is typically followed by a rapid contraction phase resulting in a sharp decline in the frequency of functional CTLs. We describe a novel approach to immunotherapy based on a transplantation of low numbers of antigen-expressing hematopoietic stem cells (HSCs) following nonmyeloablative or partially myeloablative conditioning. Continuous antigen presentation by a limited number of differentiated transgenic hematopoietic cells results in an induction and prolonged maintenance of fully functional effector T cell responses in a mouse model. Recipient animals display high levels of antigen-specific CTLs four months following transplantation in contrast to dendritic cell-immunized animals in which the response typically declines at 4-6 weeks post-immunization. Majority of HSC-induced antigen-specific CD8+ T cells display central memory phenotype, efficiently kill target cells in vivo, and protect recipients against tumor growth in a preventive setting. Furthermore, we confirm previously published observation that high level engraftment of antigen-expressing HSCs following myeloablative conditioning results in tolerance and an absence of specific cytotoxic activity in vivo. In conclusion, the data presented here supports potential application of immunization by limited transplantation of antigen-expressing HSCs for the prevention and treatment of cancer and therapeutic immunization of chronic infectious diseases such as HIV-1/AIDS.

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Antigen-specific T cells induced by HSC immunization efficiently kill target cells in vivo.(A) B6 mice were immunized with 2×104 DC-tOVA, OVA peptide-coated DCs (DC-pOVA), or HSC-tOVA. HSC-tOVA recipients were pretreated with BU or irradiated with 900 RAD. 16 weeks post immunization, mice were injected with 107 OVA-transgenic splenocytes labeled with high concentration of CFSE (3.5 µM, right peak) and 107 wild type B6 splenocytes labeled with low concentration of CFSE (0.35 µM, middle peak). Under these conditions, only the splenocytes from OVA-transgenic mice (right peak) are target of host OVA-specific CTLs. 24 hours post injection, splenocytes were harvested and the relative proportions of remaining CFSE+ populations were determined. (B) Graphical representation of the percentage of target cell killing in vivo. 4 animals per group; error bars represent standard errors.
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pone-0016897-g004: Antigen-specific T cells induced by HSC immunization efficiently kill target cells in vivo.(A) B6 mice were immunized with 2×104 DC-tOVA, OVA peptide-coated DCs (DC-pOVA), or HSC-tOVA. HSC-tOVA recipients were pretreated with BU or irradiated with 900 RAD. 16 weeks post immunization, mice were injected with 107 OVA-transgenic splenocytes labeled with high concentration of CFSE (3.5 µM, right peak) and 107 wild type B6 splenocytes labeled with low concentration of CFSE (0.35 µM, middle peak). Under these conditions, only the splenocytes from OVA-transgenic mice (right peak) are target of host OVA-specific CTLs. 24 hours post injection, splenocytes were harvested and the relative proportions of remaining CFSE+ populations were determined. (B) Graphical representation of the percentage of target cell killing in vivo. 4 animals per group; error bars represent standard errors.

Mentions: To test the functionality of antigen-specific T cells induced by administration of HSC-tOVA, the animals were immunized as indicated in the legend of Figure 4. 16 weeks post immunization, immunized animals and controls were administered with 107 CFSE-labeled splenocytes expressing OVA (Fig. 4A, high intensity peak on the right). As internal control, 107 splenocytes from normal B6 mice labeled with low concentration of CFSE were co-injected (Fig. 4A, middle peak). Under these conditions, only splenocytes from OVA-transgenic mice (right peak) will be recognized by recipient's OVA-specific CTLs. 24 hours after injection, splenocytes were harvested and the number of remaining CFSE+ cells was determined. The groups administered with 500 or 2×104 HSC-tOVA under nonmyeloablative conditions exhibited significantly greater extent of in vivo target cell killing than mice immunized with OVA-transgenic (DC-tOVA) or OVA peptide-coated DCs (Fig. 4B) (DC-pOVA) (p<0.05 for HSC-tOVA/DC-pOVA and HSC-tOVA/DC-tOVA comparisons at both 500 and 2×104 HSC vaccine doses). In contrast, mice that received high dose of radiation (900 RAD) prior to the transplantation of HSC-tOVA did not exhibit any detectable CTL activity. Thus, high-level expression of antigen not only decreases the frequency of antigen-specific CD8+ T cells but also abrogates antigen-specific cytotoxic activity.


Limited transplantation of antigen-expressing hematopoietic stem cells induces long-lasting cytotoxic T cell responses.

Denning WL, Xu J, Guo S, Klug CA, Hel Z - PLoS ONE (2011)

Antigen-specific T cells induced by HSC immunization efficiently kill target cells in vivo.(A) B6 mice were immunized with 2×104 DC-tOVA, OVA peptide-coated DCs (DC-pOVA), or HSC-tOVA. HSC-tOVA recipients were pretreated with BU or irradiated with 900 RAD. 16 weeks post immunization, mice were injected with 107 OVA-transgenic splenocytes labeled with high concentration of CFSE (3.5 µM, right peak) and 107 wild type B6 splenocytes labeled with low concentration of CFSE (0.35 µM, middle peak). Under these conditions, only the splenocytes from OVA-transgenic mice (right peak) are target of host OVA-specific CTLs. 24 hours post injection, splenocytes were harvested and the relative proportions of remaining CFSE+ populations were determined. (B) Graphical representation of the percentage of target cell killing in vivo. 4 animals per group; error bars represent standard errors.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3040734&req=5

pone-0016897-g004: Antigen-specific T cells induced by HSC immunization efficiently kill target cells in vivo.(A) B6 mice were immunized with 2×104 DC-tOVA, OVA peptide-coated DCs (DC-pOVA), or HSC-tOVA. HSC-tOVA recipients were pretreated with BU or irradiated with 900 RAD. 16 weeks post immunization, mice were injected with 107 OVA-transgenic splenocytes labeled with high concentration of CFSE (3.5 µM, right peak) and 107 wild type B6 splenocytes labeled with low concentration of CFSE (0.35 µM, middle peak). Under these conditions, only the splenocytes from OVA-transgenic mice (right peak) are target of host OVA-specific CTLs. 24 hours post injection, splenocytes were harvested and the relative proportions of remaining CFSE+ populations were determined. (B) Graphical representation of the percentage of target cell killing in vivo. 4 animals per group; error bars represent standard errors.
Mentions: To test the functionality of antigen-specific T cells induced by administration of HSC-tOVA, the animals were immunized as indicated in the legend of Figure 4. 16 weeks post immunization, immunized animals and controls were administered with 107 CFSE-labeled splenocytes expressing OVA (Fig. 4A, high intensity peak on the right). As internal control, 107 splenocytes from normal B6 mice labeled with low concentration of CFSE were co-injected (Fig. 4A, middle peak). Under these conditions, only splenocytes from OVA-transgenic mice (right peak) will be recognized by recipient's OVA-specific CTLs. 24 hours after injection, splenocytes were harvested and the number of remaining CFSE+ cells was determined. The groups administered with 500 or 2×104 HSC-tOVA under nonmyeloablative conditions exhibited significantly greater extent of in vivo target cell killing than mice immunized with OVA-transgenic (DC-tOVA) or OVA peptide-coated DCs (Fig. 4B) (DC-pOVA) (p<0.05 for HSC-tOVA/DC-pOVA and HSC-tOVA/DC-tOVA comparisons at both 500 and 2×104 HSC vaccine doses). In contrast, mice that received high dose of radiation (900 RAD) prior to the transplantation of HSC-tOVA did not exhibit any detectable CTL activity. Thus, high-level expression of antigen not only decreases the frequency of antigen-specific CD8+ T cells but also abrogates antigen-specific cytotoxic activity.

Bottom Line: Continuous antigen presentation by a limited number of differentiated transgenic hematopoietic cells results in an induction and prolonged maintenance of fully functional effector T cell responses in a mouse model.Majority of HSC-induced antigen-specific CD8+ T cells display central memory phenotype, efficiently kill target cells in vivo, and protect recipients against tumor growth in a preventive setting.Furthermore, we confirm previously published observation that high level engraftment of antigen-expressing HSCs following myeloablative conditioning results in tolerance and an absence of specific cytotoxic activity in vivo.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.

ABSTRACT
Harnessing the ability of cytotoxic T lymphocytes (CTLs) to recognize and eradicate tumor or pathogen-infected cells is a critical goal of modern immune-based therapies. Although multiple immunization strategies efficiently induce high levels of antigen-specific CTLs, the initial increase is typically followed by a rapid contraction phase resulting in a sharp decline in the frequency of functional CTLs. We describe a novel approach to immunotherapy based on a transplantation of low numbers of antigen-expressing hematopoietic stem cells (HSCs) following nonmyeloablative or partially myeloablative conditioning. Continuous antigen presentation by a limited number of differentiated transgenic hematopoietic cells results in an induction and prolonged maintenance of fully functional effector T cell responses in a mouse model. Recipient animals display high levels of antigen-specific CTLs four months following transplantation in contrast to dendritic cell-immunized animals in which the response typically declines at 4-6 weeks post-immunization. Majority of HSC-induced antigen-specific CD8+ T cells display central memory phenotype, efficiently kill target cells in vivo, and protect recipients against tumor growth in a preventive setting. Furthermore, we confirm previously published observation that high level engraftment of antigen-expressing HSCs following myeloablative conditioning results in tolerance and an absence of specific cytotoxic activity in vivo. In conclusion, the data presented here supports potential application of immunization by limited transplantation of antigen-expressing HSCs for the prevention and treatment of cancer and therapeutic immunization of chronic infectious diseases such as HIV-1/AIDS.

Show MeSH
Related in: MedlinePlus