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Early immune responses in rainbow trout liver upon viral hemorrhagic septicemia virus (VHSV) infection.

Castro R, Abós B, Pignatelli J, von Gersdorff Jørgensen L, González Granja A, Buchmann K, Tafalla C - PLoS ONE (2014)

Bottom Line: Our results indicate that T lymphocytes play a key role in the initial response to VHSV in the liver, since CD3, CD8, CD4, perforin, Mx and interferon (IFN) transcription levels were up-regulated in response to VHSV.Consequently, flow cytometry analysis of CD8α+ cells in liver and spleen at day 5 post-infection revealed a decrease in the number of CD8α+ cells in the spleen and an increased population in the liver.No differences were found however in the percentages of B lymphocyte (IgM+ or IgD+) populations.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos (Madrid), Spain.

ABSTRACT
Among the essential metabolic functions of the liver, in mammals, a role as mediator of systemic and local innate immunity has also been reported. Although the presence of an important leukocyte population in mammalian liver is well documented, the characterization of leukocyte populations in the teleost liver has been only scarcely addressed. In the current work, we have confirmed the presence of IgM+, IgD+, IgT+, CD8α+, CD3+ cells, and cells expressing major histocompatibility complex (MHC-II) in rainbow trout (Oncorhynchus mykiss) liver by flow cytometry and/or immunohistochemistry analysis. Additionally, the effect of viral hemorrhagic septicemia virus (VHSV) on the liver immune response was assessed. First, we studied the effect of viral intraperitoneal injection on the transcription of a wide selection of immune genes at days 1, 2 and 5 post-infection. These included a group of leukocyte markers genes, pattern recognition receptors (PRRs), chemokines, chemokine receptor genes, and other genes involved in the early immune response and in acute phase reaction. Our results indicate that T lymphocytes play a key role in the initial response to VHSV in the liver, since CD3, CD8, CD4, perforin, Mx and interferon (IFN) transcription levels were up-regulated in response to VHSV. Consequently, flow cytometry analysis of CD8α+ cells in liver and spleen at day 5 post-infection revealed a decrease in the number of CD8α+ cells in the spleen and an increased population in the liver. No differences were found however in the percentages of B lymphocyte (IgM+ or IgD+) populations. In addition, a strong up-regulation in the transcription levels of several PRRs and chemokines was observed from the second day of infection, indicating an important role of these factors in the response of the liver to viral infections.

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Transcription levels of other genes of the immune response/acute phase reaction in liver in response to VHSV.Rainbow trout were infected with VHSV as described in the legend of Fig. 4 and the liver sampled to determine the levels of expression of different genes related with the initial response of the immune system by real-time PCR. Data are shown as the mean gene expression relative to the expression of endogenous control EF-1α ± SD. Expression levels significantly different to those observed in mock-infected fish are noted as * (p<0.05), ** (p<0.001).
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pone-0111084-g007: Transcription levels of other genes of the immune response/acute phase reaction in liver in response to VHSV.Rainbow trout were infected with VHSV as described in the legend of Fig. 4 and the liver sampled to determine the levels of expression of different genes related with the initial response of the immune system by real-time PCR. Data are shown as the mean gene expression relative to the expression of endogenous control EF-1α ± SD. Expression levels significantly different to those observed in mock-infected fish are noted as * (p<0.05), ** (p<0.001).

Mentions: We have also studied the effect of VHSV on the transcription of other key genes involved in the early immune response and in the acute phase reactions. Complement factors and proteins of the acute phase response are mainly produced by the liver and can be transcriptionally regulated in fish in response to pathogens. SAA, for example, is a major acute phase protein showing up to 1000-fold increase in human plasma during inflammation and its hepatic synthesis is induced by inflammatory cytokines, mainly IL-1, IL-6 and TNF-α [34]. In our experiments, we observed an increased transcription of SAA at day 5 post-infection in response to VHSV that might be a consequence of the up-regulated IL-6 transcription detected from the second day of infection (Fig. 7). Hepcidin, another acute phase protein, was significantly up-regulated at day 5 post-infection, whereas no differences in the expression of LEAP-2 (liver-expressed antimicrobial peptide 2), the complement component C3 or IL-1β where found at any time point between control and infected fish. On the other hand, hallmark genes of the response against viral infection such as IFN1 or Mx where strongly up-regulated in the liver from day 2 (Fig. 7). An increase in IL-10 and perforin transcription was observed at day 5 and both day 2 and 5 respectively.


Early immune responses in rainbow trout liver upon viral hemorrhagic septicemia virus (VHSV) infection.

Castro R, Abós B, Pignatelli J, von Gersdorff Jørgensen L, González Granja A, Buchmann K, Tafalla C - PLoS ONE (2014)

Transcription levels of other genes of the immune response/acute phase reaction in liver in response to VHSV.Rainbow trout were infected with VHSV as described in the legend of Fig. 4 and the liver sampled to determine the levels of expression of different genes related with the initial response of the immune system by real-time PCR. Data are shown as the mean gene expression relative to the expression of endogenous control EF-1α ± SD. Expression levels significantly different to those observed in mock-infected fish are noted as * (p<0.05), ** (p<0.001).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4206492&req=5

pone-0111084-g007: Transcription levels of other genes of the immune response/acute phase reaction in liver in response to VHSV.Rainbow trout were infected with VHSV as described in the legend of Fig. 4 and the liver sampled to determine the levels of expression of different genes related with the initial response of the immune system by real-time PCR. Data are shown as the mean gene expression relative to the expression of endogenous control EF-1α ± SD. Expression levels significantly different to those observed in mock-infected fish are noted as * (p<0.05), ** (p<0.001).
Mentions: We have also studied the effect of VHSV on the transcription of other key genes involved in the early immune response and in the acute phase reactions. Complement factors and proteins of the acute phase response are mainly produced by the liver and can be transcriptionally regulated in fish in response to pathogens. SAA, for example, is a major acute phase protein showing up to 1000-fold increase in human plasma during inflammation and its hepatic synthesis is induced by inflammatory cytokines, mainly IL-1, IL-6 and TNF-α [34]. In our experiments, we observed an increased transcription of SAA at day 5 post-infection in response to VHSV that might be a consequence of the up-regulated IL-6 transcription detected from the second day of infection (Fig. 7). Hepcidin, another acute phase protein, was significantly up-regulated at day 5 post-infection, whereas no differences in the expression of LEAP-2 (liver-expressed antimicrobial peptide 2), the complement component C3 or IL-1β where found at any time point between control and infected fish. On the other hand, hallmark genes of the response against viral infection such as IFN1 or Mx where strongly up-regulated in the liver from day 2 (Fig. 7). An increase in IL-10 and perforin transcription was observed at day 5 and both day 2 and 5 respectively.

Bottom Line: Our results indicate that T lymphocytes play a key role in the initial response to VHSV in the liver, since CD3, CD8, CD4, perforin, Mx and interferon (IFN) transcription levels were up-regulated in response to VHSV.Consequently, flow cytometry analysis of CD8α+ cells in liver and spleen at day 5 post-infection revealed a decrease in the number of CD8α+ cells in the spleen and an increased population in the liver.No differences were found however in the percentages of B lymphocyte (IgM+ or IgD+) populations.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos (Madrid), Spain.

ABSTRACT
Among the essential metabolic functions of the liver, in mammals, a role as mediator of systemic and local innate immunity has also been reported. Although the presence of an important leukocyte population in mammalian liver is well documented, the characterization of leukocyte populations in the teleost liver has been only scarcely addressed. In the current work, we have confirmed the presence of IgM+, IgD+, IgT+, CD8α+, CD3+ cells, and cells expressing major histocompatibility complex (MHC-II) in rainbow trout (Oncorhynchus mykiss) liver by flow cytometry and/or immunohistochemistry analysis. Additionally, the effect of viral hemorrhagic septicemia virus (VHSV) on the liver immune response was assessed. First, we studied the effect of viral intraperitoneal injection on the transcription of a wide selection of immune genes at days 1, 2 and 5 post-infection. These included a group of leukocyte markers genes, pattern recognition receptors (PRRs), chemokines, chemokine receptor genes, and other genes involved in the early immune response and in acute phase reaction. Our results indicate that T lymphocytes play a key role in the initial response to VHSV in the liver, since CD3, CD8, CD4, perforin, Mx and interferon (IFN) transcription levels were up-regulated in response to VHSV. Consequently, flow cytometry analysis of CD8α+ cells in liver and spleen at day 5 post-infection revealed a decrease in the number of CD8α+ cells in the spleen and an increased population in the liver. No differences were found however in the percentages of B lymphocyte (IgM+ or IgD+) populations. In addition, a strong up-regulation in the transcription levels of several PRRs and chemokines was observed from the second day of infection, indicating an important role of these factors in the response of the liver to viral infections.

Show MeSH
Related in: MedlinePlus