Vbeta14(+) T cells mediate the vaccine-enhanced disease induced by immunization with respiratory syncytial virus (RSV) G glycoprotein but not with formalin-inactivated RSV

Abstract

Mice immunized with respiratory syncytial virus (RSV) G glycoprotein or with formalin-inactivated RSV (FI-RSV) exhibit severe disease following RSV challenge. This results in type 2 cytokine production and pulmonary eosinophilia, both hallmarks of vaccine-enhanced disease. RSV G-induced T-cell responses were shown to be restricted to CD4(+) T cells expressing Vbeta14 in the T-cell receptor (TCR), and the deletion of these T cells resulted in less severe disease. We therefore examined the role of Vbeta14(+) T cells in FI-RSV-induced disease. BALB/c mice were immunized with vaccinia virus expressing secreted RSV G (vvGs) or with FI-RSV. At the time of challenge with live RSV, mice were injected with antibody to the Vbeta14 component of the TCR. vvGs-immunized mice treated with anti-Vbeta14 had reduced cytokine levels in the lung. Eosinophil recruitment to the lung was also significantly reduced. In contrast, depletion of Vbeta14(+) T cells in FI-RSV-immunized mice had little impact on cytokine production or pulmonary eosinophilia. An analysis of TCR Vbeta chain usage confirmed a bias toward Vbeta14 expression on CD4(+) T cells from vvGs-immunized mice, whereas the CD4(+) T cells in FI-RSV-immunized mice expressed a diverse array of Vbeta chains. These data show that although FI-RSV and vvGs induce responses resulting in similar immunopathology, the T-cell repertoire mediating the response is different for each immunogen and suggest that the immune responses elicited by RSV G are not the basis for FI-RSV vaccine-enhanced disease.

FIG. 1.

Depletion of Vβ14⁺ T cells reduces eosinophil recruitment and cytokine production in both vvGwt- and vvGs-immunized mice. Mice were immunized with vvGwt or vvGs and challenged with RSV 6 weeks later. Anti-Vβ14 antibody or IgM isotype control was administered on days −1, 2, and 5 around RSV challenge. BAL was performed 7 days after challenge, and eosinophils were counted, and the percentage and the total number of eosinophils in the BAL compartment are shown (A and B, respectively). (C) Cytokines were measured in lung supernatants at day 4 postchallenge. The data represent the means ± standard deviations for five mice per group.

FIG. 2.

Depletion of Vβ14⁺ T cells reduces pulmonary eosinophilia in vvGs-immunized mice but not in FI-RSV-immunized mice. Mice were immunized with vvGs or FI-RSV and challenged with live RSV 6 weeks later. At days −1, 2, and 5 around RSV challenge, anti-Vβ14 antibody or IgM isotype control was administered. Seven days after challenge, BAL was performed, cells were stained, and differential cell counts were performed. The data represent the means ± standard deviations of the percentage of eosinophils (A) and the total number of eosinophils present in the BAL compartment (B). n = 5 mice per group from one of two experiments. Statistical analyses resulted in the following P values when IgM- and anti-Vβ14-treated mice from each priming group were compared. For vvGs-primed mice, P = 0.008 and 0.04 (percentage of eosinophils and total number of eosinophils, respectively). For FI-RSV-immunized mice, P = 0.176 and 0.91 (percentage of eosinophils and total number of eosinophils, respectively).

FIG. 3.

RSV titers following challenge are minimally altered by depletion of Vβ14⁺ T cells. Mice were immunized, treated with anti-Vβ14 antibody, and challenged as described in the legend of Fig. 2. At days 4 and 7 postchallenge, viral titers were measured in subsets of mice from each group as described in Materials and Methods. Data are represented as the means ± standard deviations of the log₁₀ PFU/gram of lung tissue. The limit of detection is 1.8 log₁₀ PFU/g of lung tissue. n = 5 mice per group from one of two experiments.

FIG. 4.

Vβ chain usage is restricted in vvGs-immunized mice but diverse in FI-RSV-immunized mice. Mice were immunized with vvGs or FI-RSV and challenged with live RSV. Five days after challenge, lung lymphocytes were isolated and stained for Vβ chain expression. The stained cells were analyzed by flow cytometry.

FIG. 5.

CD4⁺ T cells from vvGs-immunized mice respond primarily to a single peptide, whereas CD4⁺ T cells from FI-RSV-immunized mice respond to a diverse array of I-E^d-restricted peptides. Mice were immunized with vvGs or FI-RSV and challenged with RSV. Lung lymphocytes were isolated 5 days after challenge and stimulated with a panel of I-E^d-restricted peptides, and intracellular cytokine levels were measured after staining with fluorescently labeled anticytokine antibody. PMA/Iono, positive control cells treated with phorbol myristate acetate and ionomycin.