Limits...
Impact of genotype 1 and 2 of porcine reproductive and respiratory syndrome viruses on interferon-α responses by plasmacytoid dendritic cells.

Baumann A, Mateu E, Murtaugh MP, Summerfield A - Vet. Res. (2013)

Bottom Line: Since inhibition of IFN-α expression might initiate PRRSV pathogenesis, we further characterized PRRSV effects and host modifying factors on IFN-α responses of pDC.The effect did not require live virus and was mediated through the TLR7 pathway.Furthermore, both IFN-γ and IL-4 significantly enhanced the pDC production of IFN-α in response to PRRSV exposure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Virology and Immunoprophylaxis (IVI), Sensemattstrasse 293, Mittelhäusern, 3147, Switzerland. artur.summerfield@ivi.admin.ch.

ABSTRACT
Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) infections are characterized by prolonged viremia and viral shedding consistent with incomplete immunity. Type I interferons (IFN) are essential for mounting efficient antiviral innate and adaptive immune responses, but in a recent study, North American PRRSV genotype 2 isolates did not induce, or even strongly inhibited, IFN-α in plasmacytoid dendritic cells (pDC), representing "professional IFN-α-producing cells". Since inhibition of IFN-α expression might initiate PRRSV pathogenesis, we further characterized PRRSV effects and host modifying factors on IFN-α responses of pDC. Surprisingly, a variety of type 1 and type 2 PRRSV directly stimulated IFN-α secretion by pDC. The effect did not require live virus and was mediated through the TLR7 pathway. Furthermore, both IFN-γ and IL-4 significantly enhanced the pDC production of IFN-α in response to PRRSV exposure. PRRSV inhibition of IFN-α responses from enriched pDC stimulated by CpG oligodeoxynucleotides was weak or absent. VR-2332, the prototype genotype 2 PRRSV, only suppressed the responses by 34%, and the highest level of suppression (51%) was induced by a Chinese highly pathogenic PRRSV isolate. Taken together, these findings demonstrate that pDC respond to PRRSV and suggest that suppressive activities on pDC, if any, are moderate and strain-dependent. Thus, pDC may be a source of systemic IFN-α responses reported in PRRSV-infected animals, further contributing to the puzzling immunopathogenesis of PRRS.

Show MeSH

Related in: MedlinePlus

pDC are resistant to PRRSV infection and can prevent infection of MoDC. (A) Nucleocapsid expression in CD172alowCD4+ pDC and CD172ahighCD4- monocytes at 24, 48 and 72 h post infection with LV (black line histogram), 2982 (dotted line) or 3267 (dashed line) at an MOI of 2.5 TCID50/cell. Mock-treated cell fluorescence is shown as grey filled histograms. PAM infected with LV (MOI of 1 TCID50/cell) was used as positive control (upper panel). (B) IFN-α levels measured in the cultures shown in A. Bars represent means of triplicate cultures ± 1 standard deviation. A representative example from three independent experiments is shown. (C) Detection of PRRSV nucleocapsid in MoDC cultured alone or with enriched pDC at 24 and 48 h post infection with LV. One million MoDC co-cultured with one millions of enriched pDC or two millions MoDC alone were exposed to LV at an MOI of 1 TCID50/cell. Histograms were obtained from forward/side scatter gated MoDC treated with mock control (tinted line) or LV (black line). (D) Time course of IFN-α secretion in co-cultures of MoDC and pDC shown in panel C. One representative experiment out of two is shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3672080&req=5

Figure 5: pDC are resistant to PRRSV infection and can prevent infection of MoDC. (A) Nucleocapsid expression in CD172alowCD4+ pDC and CD172ahighCD4- monocytes at 24, 48 and 72 h post infection with LV (black line histogram), 2982 (dotted line) or 3267 (dashed line) at an MOI of 2.5 TCID50/cell. Mock-treated cell fluorescence is shown as grey filled histograms. PAM infected with LV (MOI of 1 TCID50/cell) was used as positive control (upper panel). (B) IFN-α levels measured in the cultures shown in A. Bars represent means of triplicate cultures ± 1 standard deviation. A representative example from three independent experiments is shown. (C) Detection of PRRSV nucleocapsid in MoDC cultured alone or with enriched pDC at 24 and 48 h post infection with LV. One million MoDC co-cultured with one millions of enriched pDC or two millions MoDC alone were exposed to LV at an MOI of 1 TCID50/cell. Histograms were obtained from forward/side scatter gated MoDC treated with mock control (tinted line) or LV (black line). (D) Time course of IFN-α secretion in co-cultures of MoDC and pDC shown in panel C. One representative experiment out of two is shown.

Mentions: PRRSV infects macrophages, MoDC, and monocyte-derived macrophages in vitro[6,8,9]. However, sorted CD172a+ cell populations of pDC were not permissive to infection. Flow cytometric three-colour analysis did not reveal the presence PRRSV nucleocapsid in gated pDC or monocytes even after prolonged incubation with PRRSV for three days (Figure 5A). These results are consistent with a previous report employing GFP tagged PRRSV[26], indicating that pDC are not permissive to PRRSV. High levels of IFN-α were detected in these cultures, confirming that productive infection is not required for pDC sensing of PRRSV (Figure 5B).


Impact of genotype 1 and 2 of porcine reproductive and respiratory syndrome viruses on interferon-α responses by plasmacytoid dendritic cells.

Baumann A, Mateu E, Murtaugh MP, Summerfield A - Vet. Res. (2013)

pDC are resistant to PRRSV infection and can prevent infection of MoDC. (A) Nucleocapsid expression in CD172alowCD4+ pDC and CD172ahighCD4- monocytes at 24, 48 and 72 h post infection with LV (black line histogram), 2982 (dotted line) or 3267 (dashed line) at an MOI of 2.5 TCID50/cell. Mock-treated cell fluorescence is shown as grey filled histograms. PAM infected with LV (MOI of 1 TCID50/cell) was used as positive control (upper panel). (B) IFN-α levels measured in the cultures shown in A. Bars represent means of triplicate cultures ± 1 standard deviation. A representative example from three independent experiments is shown. (C) Detection of PRRSV nucleocapsid in MoDC cultured alone or with enriched pDC at 24 and 48 h post infection with LV. One million MoDC co-cultured with one millions of enriched pDC or two millions MoDC alone were exposed to LV at an MOI of 1 TCID50/cell. Histograms were obtained from forward/side scatter gated MoDC treated with mock control (tinted line) or LV (black line). (D) Time course of IFN-α secretion in co-cultures of MoDC and pDC shown in panel C. One representative experiment out of two is shown.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672080&req=5

Figure 5: pDC are resistant to PRRSV infection and can prevent infection of MoDC. (A) Nucleocapsid expression in CD172alowCD4+ pDC and CD172ahighCD4- monocytes at 24, 48 and 72 h post infection with LV (black line histogram), 2982 (dotted line) or 3267 (dashed line) at an MOI of 2.5 TCID50/cell. Mock-treated cell fluorescence is shown as grey filled histograms. PAM infected with LV (MOI of 1 TCID50/cell) was used as positive control (upper panel). (B) IFN-α levels measured in the cultures shown in A. Bars represent means of triplicate cultures ± 1 standard deviation. A representative example from three independent experiments is shown. (C) Detection of PRRSV nucleocapsid in MoDC cultured alone or with enriched pDC at 24 and 48 h post infection with LV. One million MoDC co-cultured with one millions of enriched pDC or two millions MoDC alone were exposed to LV at an MOI of 1 TCID50/cell. Histograms were obtained from forward/side scatter gated MoDC treated with mock control (tinted line) or LV (black line). (D) Time course of IFN-α secretion in co-cultures of MoDC and pDC shown in panel C. One representative experiment out of two is shown.
Mentions: PRRSV infects macrophages, MoDC, and monocyte-derived macrophages in vitro[6,8,9]. However, sorted CD172a+ cell populations of pDC were not permissive to infection. Flow cytometric three-colour analysis did not reveal the presence PRRSV nucleocapsid in gated pDC or monocytes even after prolonged incubation with PRRSV for three days (Figure 5A). These results are consistent with a previous report employing GFP tagged PRRSV[26], indicating that pDC are not permissive to PRRSV. High levels of IFN-α were detected in these cultures, confirming that productive infection is not required for pDC sensing of PRRSV (Figure 5B).

Bottom Line: Since inhibition of IFN-α expression might initiate PRRSV pathogenesis, we further characterized PRRSV effects and host modifying factors on IFN-α responses of pDC.The effect did not require live virus and was mediated through the TLR7 pathway.Furthermore, both IFN-γ and IL-4 significantly enhanced the pDC production of IFN-α in response to PRRSV exposure.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Virology and Immunoprophylaxis (IVI), Sensemattstrasse 293, Mittelhäusern, 3147, Switzerland. artur.summerfield@ivi.admin.ch.

ABSTRACT
Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) infections are characterized by prolonged viremia and viral shedding consistent with incomplete immunity. Type I interferons (IFN) are essential for mounting efficient antiviral innate and adaptive immune responses, but in a recent study, North American PRRSV genotype 2 isolates did not induce, or even strongly inhibited, IFN-α in plasmacytoid dendritic cells (pDC), representing "professional IFN-α-producing cells". Since inhibition of IFN-α expression might initiate PRRSV pathogenesis, we further characterized PRRSV effects and host modifying factors on IFN-α responses of pDC. Surprisingly, a variety of type 1 and type 2 PRRSV directly stimulated IFN-α secretion by pDC. The effect did not require live virus and was mediated through the TLR7 pathway. Furthermore, both IFN-γ and IL-4 significantly enhanced the pDC production of IFN-α in response to PRRSV exposure. PRRSV inhibition of IFN-α responses from enriched pDC stimulated by CpG oligodeoxynucleotides was weak or absent. VR-2332, the prototype genotype 2 PRRSV, only suppressed the responses by 34%, and the highest level of suppression (51%) was induced by a Chinese highly pathogenic PRRSV isolate. Taken together, these findings demonstrate that pDC respond to PRRSV and suggest that suppressive activities on pDC, if any, are moderate and strain-dependent. Thus, pDC may be a source of systemic IFN-α responses reported in PRRSV-infected animals, further contributing to the puzzling immunopathogenesis of PRRS.

Show MeSH
Related in: MedlinePlus