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Aedes aegypti saliva alters leukocyte recruitment and cytokine signaling by antigen-presenting cells during West Nile virus infection.

Schneider BS, Soong L, Coffey LL, Stevenson HL, McGee CE, Higgs S - PLoS ONE (2010)

Bottom Line: Antigen-presenting cell (APC) signals have a profound effect on host antiviral responses and disease severity.Our in vitro results suggest that mosquito saliva significantly decreases the expression of interferon-beta and inducible nitric oxide synthase in macrophages (by as much as 50 and 70%, respectively), whilst transiently enhancing interleukin-10 (IL-10) expression.In vivo results indicate that the predominate effect of mosquito feeding is to significantly reduce the recruitment of T cells, leading the inoculation site of mice exposed to WNV alone to have up to 2.8 fold more t cells as mice infected in the presence of mosquito saliva.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Center for Biodefense & Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America.

ABSTRACT
West Nile virus (WNV) is transmitted during mosquito bloodfeeding. Consequently, the first vertebrate cells to contact WNV are cells in the skin, followed by those in the draining lymph node. Macrophages and dendritic cells are critical early responders in host defense against WNV infection, not just because of their role in orchestrating the immune response, but also because of their importance as sites of early peripheral viral replication. Antigen-presenting cell (APC) signals have a profound effect on host antiviral responses and disease severity. During transmission, WNV is intimately associated with mosquito saliva. Due to the ability of mosquito saliva to affect inflammation and immune responses, and the importance of understanding early events in WNV infection, we investigated whether mosquito saliva alters APC signaling during arbovirus infection, and if alterations in cell recruitment occur when WNV infection is initiated with mosquito saliva. Accordingly, experiments were performed with cultured dendritic cells and macrophages, flow cytometry was used to characterize infiltrating cell types in the skin and lymph nodes during early infection, and real-time RT-PCR was employed to evaluate virus and cytokine levels. Our in vitro results suggest that mosquito saliva significantly decreases the expression of interferon-beta and inducible nitric oxide synthase in macrophages (by as much as 50 and 70%, respectively), whilst transiently enhancing interleukin-10 (IL-10) expression. In vivo results indicate that the predominate effect of mosquito feeding is to significantly reduce the recruitment of T cells, leading the inoculation site of mice exposed to WNV alone to have up to 2.8 fold more t cells as mice infected in the presence of mosquito saliva. These shifts in cell population are associated with significantly elevated IL-10 and WNV (up to 4.0 and 10 fold, respectively) in the skin and draining lymph nodes. These results suggest that mosquito saliva dysregulates APC antiviral signaling, and reveal a possible mechanism for the observed enhancement of WNV disease mediated by mosquito saliva via a reduction of T lymphocyte and antiviral activity at the inoculation site, an elevated abundance of susceptible cell types, and a concomitant increase in immunoregulatory activity of IL-10.

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In vitro expression of cytokines in SINV-infected resident peritoneal macrophages.IFN-β, IL-10, and iNOS levels were assessed by real-time RT-PCR at 24 and 48 h post-infection (MOI  = 1). Their mRNA expression levels were normalized to those of the GAPDH gene. The means ± standard deviation are shown, and an asterisk signifies a statistically significant difference (p<0.05) as compared to the group infected with SINV alone as determined by Mann-Whitney test. IFN-γ, IL-12, and IL-1β mRNA expression, as well as SINV titers (assessed by titration on cell culture) were found not to vary among groups (data not shown). Control groups were mock infected with PBS alone. These results are representative of two independent replicates.
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pone-0011704-g002: In vitro expression of cytokines in SINV-infected resident peritoneal macrophages.IFN-β, IL-10, and iNOS levels were assessed by real-time RT-PCR at 24 and 48 h post-infection (MOI  = 1). Their mRNA expression levels were normalized to those of the GAPDH gene. The means ± standard deviation are shown, and an asterisk signifies a statistically significant difference (p<0.05) as compared to the group infected with SINV alone as determined by Mann-Whitney test. IFN-γ, IL-12, and IL-1β mRNA expression, as well as SINV titers (assessed by titration on cell culture) were found not to vary among groups (data not shown). Control groups were mock infected with PBS alone. These results are representative of two independent replicates.

Mentions: To determine if the effect of mosquito saliva on macrophages during arbovirus infection is virus-specific, the effect of exposure to mosquito saliva on macrophage function during SINV infection was also examined. Interferon expression was detected in all groups infected with SINV (Fig. 2). IFN-β mRNA levels were diminished by 40% at 24 h p.i. in groups exposed to SGE concurrent with SINV infection (p = 0.032). This trend was sustained through 48 h, but the suppression was only marginally significant (p = 0.052; Fig. 2). As with WNV infection of macrophages, the levels of IFN-γ mRNA did not vary significantly between groups at either time point (data not shown).


Aedes aegypti saliva alters leukocyte recruitment and cytokine signaling by antigen-presenting cells during West Nile virus infection.

Schneider BS, Soong L, Coffey LL, Stevenson HL, McGee CE, Higgs S - PLoS ONE (2010)

In vitro expression of cytokines in SINV-infected resident peritoneal macrophages.IFN-β, IL-10, and iNOS levels were assessed by real-time RT-PCR at 24 and 48 h post-infection (MOI  = 1). Their mRNA expression levels were normalized to those of the GAPDH gene. The means ± standard deviation are shown, and an asterisk signifies a statistically significant difference (p<0.05) as compared to the group infected with SINV alone as determined by Mann-Whitney test. IFN-γ, IL-12, and IL-1β mRNA expression, as well as SINV titers (assessed by titration on cell culture) were found not to vary among groups (data not shown). Control groups were mock infected with PBS alone. These results are representative of two independent replicates.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2908538&req=5

pone-0011704-g002: In vitro expression of cytokines in SINV-infected resident peritoneal macrophages.IFN-β, IL-10, and iNOS levels were assessed by real-time RT-PCR at 24 and 48 h post-infection (MOI  = 1). Their mRNA expression levels were normalized to those of the GAPDH gene. The means ± standard deviation are shown, and an asterisk signifies a statistically significant difference (p<0.05) as compared to the group infected with SINV alone as determined by Mann-Whitney test. IFN-γ, IL-12, and IL-1β mRNA expression, as well as SINV titers (assessed by titration on cell culture) were found not to vary among groups (data not shown). Control groups were mock infected with PBS alone. These results are representative of two independent replicates.
Mentions: To determine if the effect of mosquito saliva on macrophages during arbovirus infection is virus-specific, the effect of exposure to mosquito saliva on macrophage function during SINV infection was also examined. Interferon expression was detected in all groups infected with SINV (Fig. 2). IFN-β mRNA levels were diminished by 40% at 24 h p.i. in groups exposed to SGE concurrent with SINV infection (p = 0.032). This trend was sustained through 48 h, but the suppression was only marginally significant (p = 0.052; Fig. 2). As with WNV infection of macrophages, the levels of IFN-γ mRNA did not vary significantly between groups at either time point (data not shown).

Bottom Line: Antigen-presenting cell (APC) signals have a profound effect on host antiviral responses and disease severity.Our in vitro results suggest that mosquito saliva significantly decreases the expression of interferon-beta and inducible nitric oxide synthase in macrophages (by as much as 50 and 70%, respectively), whilst transiently enhancing interleukin-10 (IL-10) expression.In vivo results indicate that the predominate effect of mosquito feeding is to significantly reduce the recruitment of T cells, leading the inoculation site of mice exposed to WNV alone to have up to 2.8 fold more t cells as mice infected in the presence of mosquito saliva.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, Center for Biodefense & Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, United States of America.

ABSTRACT
West Nile virus (WNV) is transmitted during mosquito bloodfeeding. Consequently, the first vertebrate cells to contact WNV are cells in the skin, followed by those in the draining lymph node. Macrophages and dendritic cells are critical early responders in host defense against WNV infection, not just because of their role in orchestrating the immune response, but also because of their importance as sites of early peripheral viral replication. Antigen-presenting cell (APC) signals have a profound effect on host antiviral responses and disease severity. During transmission, WNV is intimately associated with mosquito saliva. Due to the ability of mosquito saliva to affect inflammation and immune responses, and the importance of understanding early events in WNV infection, we investigated whether mosquito saliva alters APC signaling during arbovirus infection, and if alterations in cell recruitment occur when WNV infection is initiated with mosquito saliva. Accordingly, experiments were performed with cultured dendritic cells and macrophages, flow cytometry was used to characterize infiltrating cell types in the skin and lymph nodes during early infection, and real-time RT-PCR was employed to evaluate virus and cytokine levels. Our in vitro results suggest that mosquito saliva significantly decreases the expression of interferon-beta and inducible nitric oxide synthase in macrophages (by as much as 50 and 70%, respectively), whilst transiently enhancing interleukin-10 (IL-10) expression. In vivo results indicate that the predominate effect of mosquito feeding is to significantly reduce the recruitment of T cells, leading the inoculation site of mice exposed to WNV alone to have up to 2.8 fold more t cells as mice infected in the presence of mosquito saliva. These shifts in cell population are associated with significantly elevated IL-10 and WNV (up to 4.0 and 10 fold, respectively) in the skin and draining lymph nodes. These results suggest that mosquito saliva dysregulates APC antiviral signaling, and reveal a possible mechanism for the observed enhancement of WNV disease mediated by mosquito saliva via a reduction of T lymphocyte and antiviral activity at the inoculation site, an elevated abundance of susceptible cell types, and a concomitant increase in immunoregulatory activity of IL-10.

Show MeSH
Related in: MedlinePlus