Cutting edge: recombinant Listeria monocytogenes expressing a single immune-dominant peptide confers protective immunity to herpes simplex virus-1 infection

Abstract

The vast majority of the world's population is infected with HSV. Although antiviral therapy can reduce the incidence of reactivation and asymptomatic viral shedding, and limit morbidity and mortality from active disease, it cannot cure infection. Therefore, the development of an effective vaccine is an important global health priority. In this study, we demonstrate that recombinant Listeria monocytogenes (Lm) expressing the H-2K(b) glycoprotein B (gB)(498-505) peptide from HSV-1 triggers a robust CD8 T cell response to this Ag resulting in protective immunity to HSV infection. Following challenge with HSV-1, immune-competent mice primed with recombinant Lm-expressing gB(498-505) Ag were protected from HSV-induced paralysis. Protection was associated with dramatic reductions in recoverable virus, and early expansion of HSV-1-specific CD8 T cells in the regional lymph nodes. Thus, recombinant Lm-expressing Ag from HSV represents a promising new class of vaccines against HSV infection.

Figure 1

Generation of Lm ΔactA pHSVgB or Lm ΔactA pCONTROL A. Construct map for creating recombinant HA-tagged fusion proteins containing HSV-1 gB_498−505 and mTB ESAT6₁₋₂₀ peptides that are expressed and secreted under the Lm hly promoter and signal sequence within the pAM401 vector (cat, chloroamphenicol acetyltransferase). B. Western blot of supernatant protein from Lm ΔactA pHSVgB (lane 1), Lm ΔactA pCONTROL (lane 2), and Lm-OVA (19) with anti-HA Ab.

Figure 2

Induction of HSV-specific CD8 T cells after infection with Lm ΔactA pHSVgB A. The percentage of HSV-gB_498−505 specific CD8 T cells in the peripheral blood determined by staining with H-2K^b dimer × loaded with gB_498−505 peptide at the indicated time points after inoculation with 10⁶ CFUs of either Lm ΔactA pHSVgB or Lm ΔactA pCONTROL, or gB peptide (100μg) in alum. B. IFN-γ production by CD8 and CD4 T splenocytes from mice day 8 after infection with 10⁶ CFUs of either Lm ΔactA pHSVgB or Lm ΔactA pCONTROL after re-stimulation with gB_498−505 peptide and LLO_189−201 peptide, respectively. Numbers in the upper right hand quadrant indicate the mean percentage (± standard error) of IFN-γ+ cells of total CD8+ or CD4+ T cells for five mice per group from two separate experiments. C. Absolute number of IFN-γ producing CD8 T cells per spleen day 8 after infection with Lm ΔactA pHSVgB or Lm ΔactA pCONTROL determined by intracellular cytokine staining. D. IFN-γ concentration in splenocyte culture supernatants from day 8 Lm ΔactA pHSVgB or Lm ΔactA pCONTROL infected mice after 72-hour stimulation with gB_498−505, LLO_189−201, or no peptide.

Figure 3

Lm ΔactA pHSVgB protects mice from lethal challenge with HSV-1. A. Paralysis-free survival after HSV-1 footpad inoculation (2.5 × 10⁶ PFUs) in mice primed 28 days previously with Lm ΔactA pHSVgB (squares) or Lm ΔactA pCONTROL (triangles). Difference in survival between these two groups, P = 0.0002. These data represent 20 mice per experimental group pooled from two independent experiments with similar results. B. Recoverable HSV-1 titers in the footpad and spinal cord on day 6 after HSV infection in naïve mice, or mice primed 28 days previously with Lm ΔactA pHSVgB, Lm ΔactA pCONTROL, or gB peptide in alum. Percentage of CD8 T cells in draining popliteal lymph nodes producing IFN-γ after stimulation with gB_498−505 peptide (black bars) or no peptide (white bars) on day 3 (C) and day 6 (D) after footpad inoculation with HSV-1 (2.5 × 10⁶ PFUs) in naïve mice, or mice primed 28 days previously with Lm ΔactA pHSVgB or Lm ΔactA pCONTROL. E. Recoverable HSV-1 titers in the footpad and spinal cord on day 6 after HSV infection in IFN-γ-deficient or MyD88-deficient mice primed 28 days previously with Lm ΔactA pHSVgB or Lm ΔactA pCONTROL.