Human immunodeficiency virus-1-derived lentiviral vectors have been increasingly used for gene delivery in both pre-clinical and clinical models. Numerous studies have shown that dendritic cells (DC) transduced with concentrated lentiviral vectors can induce primary T-cell responses to viral and tumor antigens. In this study, we attempted to generate influenza hemagglutinin-specific CD4 T cells using lentiviral vectors containing the signal sequence and human lysosome-associated membrane protein to target hemagglutinin to the major histocompatibility complex class II processing pathway. Autologous dendritic cells were generated in serum-free medium and transduced with concentrated, high-titer lentiviruses to stimulate autologous T cells. Unexpectedly, we failed to generate influenza hemagglutinin-specific CD4 T cells rather than T cells specific for fetal calf serum (FCS). By limiting dilution, we established several FCS-specific CD4 T-cell clones restricted by human leukocyte antigen-DR1 and human leukocyte antigen-DR4. Lentiviruses produced in human serum-adapted 293 cells or in serum-free medium were unable to sensitize dendritic cells for recognition by FCS-specific CD4 T-cell clones. Our results indicate that residual FCS in concentrated lentiviral pellets is, in part, responsible for its immunogenicity. These FCS-specific CD4 T cells may be useful in testing clinical grade lentiviral vectors for the presence of contaminating FCS.
Bibliographical noteFunding Information:
We are grateful to Dr Nikunj Somia for helpful discussion on lentiviral purification and Dr Nicola Philpott for English editing. LB was a recipient of a Baxter Oncology Postdoctoral Fellowship of the Amy Strelzer Manasevit Scholars Program, the National Marrow Donor Program. XZ was a recipient of an American Society of Hematology Junior Faculty Award. This work was supported by the Children’s Cancer Research Fund in Minneapolis, Viking Children’s Fund and the University of Minnesota Masonic Cancer Center (XZ). LB and HG designed, carried out the research, analyzed the data and wrote the paper; XH, ST and MW designed, carried out the research, analyzed the data and edited the paper; RSM discussed the work and wrote the paper; XZ oversaw the work and wrote the paper.