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Peripheral and central immune cell reservoirs in tissues from asymptomatic cats chronically infected with feline immunodeficiency virus

View Article: PubMed Central - PubMed

ABSTRACT

Feline immunodeficiency virus (FIV) infection in cats results in life-long viral persistence and progressive immunopathology. We have previously described a cohort of experimentally infected cats demonstrating a progressive decline of peripheral blood CD4+ T-cell over six years in the face of apparent peripheral viral latency. More recently we reported findings from this same cohort that revealed popliteal lymph node tissue as sites for ongoing viral replication suggesting that tissue reservoirs are important in FIV immunopathogenesis during the late asymptomatic phase of infection. Results reported herein characterize important tissue reservoirs of active viral replication during the late asymptomatic phase by examining biopsied specimens of spleen, mesenteric lymph node (MLN), and intestine from FIV-infected and uninfected control cats. Peripheral blood collected coincident with harvest of tissues demonstrated severe CD4+ T-cell depletion, undetectable plasma viral gag RNA and rarely detectable peripheral blood mononuclear cell (PBMC)-associated viral RNA (vRNA) by real-time PCR. However, vRNA was detectable in all three tissue sites from three of four FIV-infected cats despite the absence of detectable vRNA in plasma. A novel in situ hybridization assay identified B cell lymphoid follicular domains as microanatomical foci of ongoing FIV replication. Additionally, we demonstrated that CD4+ leukocyte depletion in tissues, and CD4+ and CD21+ leukocytes as important cellular reservoirs of ongoing replication. These findings revealed that tissue reservoirs support foci of ongoing viral replication, in spite of highly restricted viral replication in blood. Lentiviral eradication strategies will need address tissue viral reservoirs.

No MeSH data available.


Related in: MedlinePlus

Determination of CD4+ and CD8+ leukocyte frequency in MLN and spleen from FIV-infected and uninfected cats.A severe CD4+ depletion is observed in the paracortex and medullary cords of MLN and in periarteriolar lymphoid sheaths of the spleen of FIV-infected progressor cats relative to uninfected cats (a,b,g,h), consistent with the flow cytometry data (c,i). A notable CD8+ depletion is also evident in the paracortex of MLNs from FIV-infected progressor cats relative to uninfected cats (d,e), and supported by flow cytometric analysis (f). IHC analysis for CD8+ T cell distribution demonstrates diffuse staining of the red pulp in both infected and uninfected cats (j,k) whereas splenic CD8+ T cell frequencies are variable among cats by flow cytometry (l). For flow cytometry data, each point represents one cat, the horizontal bar represents mean, and the whiskers represents the range. The LTNP cat’s flow cytometry value is a single triangle.
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pone.0175327.g006: Determination of CD4+ and CD8+ leukocyte frequency in MLN and spleen from FIV-infected and uninfected cats.A severe CD4+ depletion is observed in the paracortex and medullary cords of MLN and in periarteriolar lymphoid sheaths of the spleen of FIV-infected progressor cats relative to uninfected cats (a,b,g,h), consistent with the flow cytometry data (c,i). A notable CD8+ depletion is also evident in the paracortex of MLNs from FIV-infected progressor cats relative to uninfected cats (d,e), and supported by flow cytometric analysis (f). IHC analysis for CD8+ T cell distribution demonstrates diffuse staining of the red pulp in both infected and uninfected cats (j,k) whereas splenic CD8+ T cell frequencies are variable among cats by flow cytometry (l). For flow cytometry data, each point represents one cat, the horizontal bar represents mean, and the whiskers represents the range. The LTNP cat’s flow cytometry value is a single triangle.

Mentions: Findings from immunohistochemical analysis of MLNs for T leukocyte subset frequency and distribution for the two FIV-progressor cats (184,186) shared similarities that included diffuse depletion of lymphocytes within germinal centers, paracortical zones, and medullary cords. Immunohistochemistry (IHC) assay for CD4+ leukocytes demonstrated greatly reduced numbers and irregular distributions of CD4+ leukocytes throughout the MLNs of both FIV-progressor cats examined relative to uninfected cats. Furthermore, these IHC results corroborated the decreased frequency of CD4+ cells in the MLN determined by flow cytometry (Fig 6a–6c). Similar findings were observed with IHC analysis of MLNs for CD8+ T cell frequency which revealed a patchy and pauci-cellularity in FIV-infected cats relative to uninfected cats. Again, IHC analysis for CD8+ T cell frequency was consistent with the flow cytometry data showing CD8+ T cell depletion in the MLN (Fig 6d–6f). Of note, a subjective increase in the number of CD8+ T cells within the mantle zone of cortical lymphoid follicles was observed for MLNs from FIV-infected cats relative to uninfected control cats (data not shown). The MLN harvested from the LTNP cat revealed paracortical zones and medullary cords that were densely populated with numerous CD4+ and CD8+ cells that were not consistent with lymphoid depletion. These IHC data were again consistent with flow cytometric analysis of T cell subset frequencies in the MLN of the LTNP cat (Fig 6c and 6f).


Peripheral and central immune cell reservoirs in tissues from asymptomatic cats chronically infected with feline immunodeficiency virus
Determination of CD4+ and CD8+ leukocyte frequency in MLN and spleen from FIV-infected and uninfected cats.A severe CD4+ depletion is observed in the paracortex and medullary cords of MLN and in periarteriolar lymphoid sheaths of the spleen of FIV-infected progressor cats relative to uninfected cats (a,b,g,h), consistent with the flow cytometry data (c,i). A notable CD8+ depletion is also evident in the paracortex of MLNs from FIV-infected progressor cats relative to uninfected cats (d,e), and supported by flow cytometric analysis (f). IHC analysis for CD8+ T cell distribution demonstrates diffuse staining of the red pulp in both infected and uninfected cats (j,k) whereas splenic CD8+ T cell frequencies are variable among cats by flow cytometry (l). For flow cytometry data, each point represents one cat, the horizontal bar represents mean, and the whiskers represents the range. The LTNP cat’s flow cytometry value is a single triangle.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383277&req=5

pone.0175327.g006: Determination of CD4+ and CD8+ leukocyte frequency in MLN and spleen from FIV-infected and uninfected cats.A severe CD4+ depletion is observed in the paracortex and medullary cords of MLN and in periarteriolar lymphoid sheaths of the spleen of FIV-infected progressor cats relative to uninfected cats (a,b,g,h), consistent with the flow cytometry data (c,i). A notable CD8+ depletion is also evident in the paracortex of MLNs from FIV-infected progressor cats relative to uninfected cats (d,e), and supported by flow cytometric analysis (f). IHC analysis for CD8+ T cell distribution demonstrates diffuse staining of the red pulp in both infected and uninfected cats (j,k) whereas splenic CD8+ T cell frequencies are variable among cats by flow cytometry (l). For flow cytometry data, each point represents one cat, the horizontal bar represents mean, and the whiskers represents the range. The LTNP cat’s flow cytometry value is a single triangle.
Mentions: Findings from immunohistochemical analysis of MLNs for T leukocyte subset frequency and distribution for the two FIV-progressor cats (184,186) shared similarities that included diffuse depletion of lymphocytes within germinal centers, paracortical zones, and medullary cords. Immunohistochemistry (IHC) assay for CD4+ leukocytes demonstrated greatly reduced numbers and irregular distributions of CD4+ leukocytes throughout the MLNs of both FIV-progressor cats examined relative to uninfected cats. Furthermore, these IHC results corroborated the decreased frequency of CD4+ cells in the MLN determined by flow cytometry (Fig 6a–6c). Similar findings were observed with IHC analysis of MLNs for CD8+ T cell frequency which revealed a patchy and pauci-cellularity in FIV-infected cats relative to uninfected cats. Again, IHC analysis for CD8+ T cell frequency was consistent with the flow cytometry data showing CD8+ T cell depletion in the MLN (Fig 6d–6f). Of note, a subjective increase in the number of CD8+ T cells within the mantle zone of cortical lymphoid follicles was observed for MLNs from FIV-infected cats relative to uninfected control cats (data not shown). The MLN harvested from the LTNP cat revealed paracortical zones and medullary cords that were densely populated with numerous CD4+ and CD8+ cells that were not consistent with lymphoid depletion. These IHC data were again consistent with flow cytometric analysis of T cell subset frequencies in the MLN of the LTNP cat (Fig 6c and 6f).

View Article: PubMed Central - PubMed

ABSTRACT

Feline immunodeficiency virus (FIV) infection in cats results in life-long viral persistence and progressive immunopathology. We have previously described a cohort of experimentally infected cats demonstrating a progressive decline of peripheral blood CD4+ T-cell over six years in the face of apparent peripheral viral latency. More recently we reported findings from this same cohort that revealed popliteal lymph node tissue as sites for ongoing viral replication suggesting that tissue reservoirs are important in FIV immunopathogenesis during the late asymptomatic phase of infection. Results reported herein characterize important tissue reservoirs of active viral replication during the late asymptomatic phase by examining biopsied specimens of spleen, mesenteric lymph node (MLN), and intestine from FIV-infected and uninfected control cats. Peripheral blood collected coincident with harvest of tissues demonstrated severe CD4+ T-cell depletion, undetectable plasma viral gag RNA and rarely detectable peripheral blood mononuclear cell (PBMC)-associated viral RNA (vRNA) by real-time PCR. However, vRNA was detectable in all three tissue sites from three of four FIV-infected cats despite the absence of detectable vRNA in plasma. A novel in situ hybridization assay identified B cell lymphoid follicular domains as microanatomical foci of ongoing FIV replication. Additionally, we demonstrated that CD4+ leukocyte depletion in tissues, and CD4+ and CD21+ leukocytes as important cellular reservoirs of ongoing replication. These findings revealed that tissue reservoirs support foci of ongoing viral replication, in spite of highly restricted viral replication in blood. Lentiviral eradication strategies will need address tissue viral reservoirs.

No MeSH data available.


Related in: MedlinePlus