Dendritic cells efficiently induce protective antiviral immunity - PubMed (original) (raw)

Dendritic cells efficiently induce protective antiviral immunity

B Ludewig et al. J Virol. 1998 May.

Abstract

Cytotoxic T lymphocytes (CTL) are essential for effective immunity to various viral infections. Because of the high speed of viral replication, control of viral infections imposes demanding functional and qualitative requirements on protective T-cell responses. Dendritic cells (DC) have been shown to efficiently acquire, transport, and present antigens to naive CTL in vitro and in vivo. In this study, we assessed the potential of DC, either pulsed with the lymphocytic choriomeningitis virus (LCMV)-specific peptide GP33-41 or constitutively expressing the respective epitope, to induce LCMV-specific antiviral immunity in vivo. Comparing different application routes, we found that only 100 to 1,000 DC had to reach the spleen to achieve protective levels of CTL activation. The DC-induced antiviral immune response developed rapidly and was long lasting. Already at day 2 after a single intravenous immunization with high doses of DC (1 x 10(5) to 5 x 10(5)), mice were fully protected against LCMV challenge infection, and direct ex vivo cytotoxicity was detectable at day 4 after DC immunization. At day 60, mice were still protected against LCMV challenge infection. Importantly, priming with DC also conferred protection against infections in which the homing of CTL into peripheral organs is essential: DC-immunized mice rapidly cleared an infection with recombinant vaccinia virus-LCMV from the ovaries and eliminated LCMV from the brain, thereby avoiding lethal choriomeningitis. A comparison of DC constitutively expressing the GP33-41 epitope with exogenously peptide-pulsed DC showed that in vivo CTL priming with peptide-loaded DC is not limited by turnover of peptide-major histocompatibility complex class I complexes. We conclude that the priming of antiviral CTL responses with DC is highly efficient, rapid, and long lasting. Therefore, the use of DC should be considered as an efficient means of immunization for antiviral vaccination strategies.

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Figures

FIG. 1

FIG. 1

Homing of bmDC to splenic T-cell areas. bmDC (3 × 106) were CFSE labeled, injected i.v., and visualized in cryostat sections with an antifluorescein antibody. (A) bmDC were found in the interfollicular areas (follicles are marked with asterisks). Magnification, ×40. (B) High magnification of boxed area in panel A showing dense follicular area (asterisk), DC with typical stellate morphology (arrow), and central artery (arrowhead). Magnification, ×350.

FIG. 2

FIG. 2

Efficient priming of antiviral CTL by H8-bmDC. C57BL/6 mice were immunized by intrasplenic injection (A), i.v. (B), or s.c. (C) with graded doses of H8-bmDC. Eight days later, induction of GP33-specific CTL was tested. Spleen cells were restimulated in vitro for 5 days with peptide-labeled, irradiated spleen cells. Specific lysis was measured on GP33-labeled EL-4 target cells (closed symbols) or EL-4 cells without peptide (open symbols). Spontaneous release was <15%. Values for control mice immunized i.v. with 105 unlabeled B6-bmDC were 10, 7, 4, and 2% with labeled EL-4 cells and 12, 9, 4, and 1% with unlabeled EL-4 cells at the indicated culture dilutions (from left to right), respectively.

FIG. 3

FIG. 3

Protection against low-dose LCMV challenge after priming with H8-bmDC. Mice were immunized intrasplenically (i.spl.), i.v. or s.c. (at the base of the tail) with the indicated number of H8-bmDC. At day 8 postimmunization, protection against LCMV strain WE was tested. Virus titers in spleens were determined 4 days after an i.v. challenge with 200 PFU of LCMV strain WE. The detection limit is represented by the broken line.

FIG. 4

FIG. 4

Kinetics of CTL induction after DC priming. Mice were primed with either 5 × 105 (A to D) or 104 (E to G) H8-bmDC i.v. At different times after immunization, ex vivo CTL activity of splenocytes was tested in a 51Cr release assay after 5 h (open symbols) or after 15 h (closed symbols) on GP33-labeled EL-4 target cells at the indicated effector/target cell (E:T) ratios. Spontaneous release after 5 h was <12%; after 15 h, it was <29%. Nonspecific lysis of unlabeled EL-4 target cells was always <5%. Values (percentages) for an LCMV-infected control mouse (day 8) were 87, 74, 61, and 35% for 5 h and 99, 98, 81, and 72% for 15 h at E:T ratios of 90, 30, 10, and 3, respectively.

FIG. 5

FIG. 5

Rapid and long-lasting induction of protective immunity by high doses of DC. Mice were immunized i.v. with different doses of H8-bmDC and challenged with 200 PFU of LCMV strain WE i.v. after 2, 8, or 60 days. Virus titers in spleens were determined 4 days after challenge infection. The broken line represents the detection limit.

FIG. 6

FIG. 6

Priming efficiencies of H8-bmDC and of peptide-labeled B6-sDC or B6-bmDC. (A) Mice were injected i.v. with 104 H8-bmDC or 104 GP33-labeled B6-sDC or B6-bmDC, and specific CTL induction was determined as described in the legend to Fig. 2. (B) Mice were immunized i.v. with different doses of H8-bmDC or GP33-labeled B6-sDC or B6-bmDC and challenged with 200 PFU of LCMV strain WE i.v. at day 8. Virus titers in spleens were determined 4 days later.

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