In vivo monitoring of transfected DNA, gene expression kinetics, and cellular immune responses in mice immunized with a human NIS gene-expressing plasmid.
In assessing the effectiveness of DNA vaccines, it is important to monitor: (1) the kinetics of target gene expression in vivo; and (2) the movement of cells that become transfected with the plasmid DNA used in the immunization of a subject. In this study, we used, as a visual imaging marker, expression of the transfected human sodium/iodide symporter (hNIS) gene, which enhances intracellular radio-pertechnetate (TcO4-) accumulation. After intradermal (i.d.) and systemic injection of mice with pcDNA-hNIS and radioactive Technetium-99m (Tc-99m), respectively, whole-body images were obtained by nuclear scintigraphy. The migration of mice cells transfected with the hNIS gene was monitored over a 2-week period by gamma-radioactivity counting of isolated cell populations and was demonstrated in peripheral lymphoid tissues, especially in the draining lymph nodes (dLNs). Beginning at 24 h after DNA inoculation and continuing for the 2-week monitoring period, hNIS-expressing cells were observed specifically in the T-cell-rich zones of the paracortical area of the dLNs. Over the same time period, high levels of INF-γ-secreting CD8 T-cells were found in the dLNs of the pcDNA-hNIS immunized mice. Tumor growth was also significantly retarded in the mice that received hNIS DNA immunization followed by inoculation with CT26 colorectal adenocarcinoma cells that had been transfected with the rat NIS gene (rNIS), which is 93% homologous to the hNIS gene. In conclusion, mouse cells transfected with hNIS DNA after i.d. immunization were found to traffic to the dLNs, and hNIS gene expression in these cells continued for at least 2 weeks post immunization. Furthermore, sequential presentation of NIS DNA to T-cells by migratory antigen presenting cells could induce NIS DNA-specific Th1 immune responses and thus retard the growth of NIS-expressing tumors.
Department of Pathology, Tumor Immunity Medical Research Center and Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
Hye-Youn
HY
Son
Department of Nuclear Medicine, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
Yong-Hyun
YH
Jeon
Department of Nuclear Medicine, Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea.
June-Key
JK
Chung
Department of Pathology, Tumor Immunity Medical Research Center and Cancer Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea cwkim@snu.ac.kr.
Chul-Woo
CW
Kim
D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D045744:Cell Line, Tumor; D004247:DNA / Q000235:genetics*; D005260:Female; D015870:Gene Expression / Q000235:genetics* / Q000276:immunology; D006801:Humans; D007111:Immunity, Cellular / Q000235:genetics / Q000276:immunology*; D007371:Interferon-gamma / Q000276:immunology; D007700:Kinetics; D008198:Lymph Nodes / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids / Q000235:genetics* / Q000276:immunology*; D051381:Rats; D027981:Symporters / Q000235:genetics* / Q000276:immunology*; D014162:Transfection / Q000379:methods; D014611:Vaccination / Q000379:methods; D000099209:Sodium-Iodide Symporters
D004247:DNA; D007371:Interferon-gamma; D027981:Symporters; D000099209:Sodium-Iodide Symporters
DNA vaccines; immune cell trafficking; lymph nodes; tumor immunity