To determine whether

PVM-specific memory CD8+ T-cells may confer immune protection, mice were immunized with GM-CSF-expanded BM-DC loaded with synthetic P261–269 (DCp) and then challenged with PVM. As shown in Fig. 3A and B, numbers of P261–269-specific CD8+ T-cells detected in the BAL of immunized mice were substantially higher than in non-immunized controls (Fig. 3A and B). Over the duration of the infection, DCp-primed mice lost less weight (Fig. 3C), displayed significantly reduced total-cell influx in the BAL (Fig. 3D), viral loads were significantly lower than in non-immunized mice (Fig. 3E), and peribronchial and interstitial cellular infiltrates were reduced (Supplementary Fig. GW-572016 mw 2), indicating an enhanced control of disease and viral loads. Since vaccination with FI-PVM elicits an enhanced Th2 response upon PVM infection [40], we investigated the effect of DCp immunization on CD4 T-cell differentiation

during PVM challenge. Compared with FI-PVM-immunized controls, mice immunized with P261–269-loaded DC displayed elevated amounts of IFNγ mRNA and cytokine levels in the lungs following challenge, indicating that they had developed a Th1-skewed immune response (Fig. 4A and B; upper panels). In contrast, FI-PVM immunized mice developed a Th2-skewed response, as indicated by the relatively high levels of IL-4 in the lungs see more (Fig. 4A and B; lower panels) and eosinophilia in two out of four mice (Fig. 4C and D). Thus, the presence of memory CD8+ T-cells specific for a single PVM-epitope led to enhanced control of virus replication and prevented Th2 skewing of PVM-induced CD4 T-cell responses upon PVM challenge, leading to a reduction of PVM-induced disease. Since immunization with P261–269-loaded DC provided partial protection, we decided to assess the protective capacity of the total PVM-specific CD8+

T-cell response, targeting multiple epitopes. A mix of CD8+ T-cells enriched from the spleen, MLN and lungs of PVM-infected or uninfected mice were adoptively transferred into recipient mice that then were infected with PVM. At d. 7 p.i. a clear population of P261–269-tetramer+ over cells was detectable in the lungs of mice that had received CD8+ T-cells of PVM-infected donors, but not in the lungs of recipients that had received naïve CD8+ T-cells of uninfected controls (Fig. 5A and B). In addition, recipients receiving immune cells from infected mice showed significantly reduced weight-loss and viral load (Fig. 5C and D). These results show that PVM-specific CD8+ T-cells, despite being a major cause of pathology in pneumovirus infections, can provide protection against PVM infection. Despite the fact that hRSV is a major cause of disease in infants, there still are major gaps in our knowledge of the host response against this virus. There is an increasing interest in using the natural mouse pathogen PVM to mimic and study severe pneumovirus infections.