Limits...
NK Cell-Mediated Regulation of Protective Memory Responses against Intracellular Ehrlichial Pathogens.

Habib S, El Andaloussi A, Hisham A, Ismail N - PLoS ONE (2016)

Bottom Line: Ehrlichiae are gram-negative obligate intracellular bacteria that cause potentially fatal human monocytic ehrlichiosis.However, the contribution of NK cells to the memory response against Ehrlichia remains elusive.Together, these data suggest that E. muris-induced memory-like NK cells, which contribute to the protective, recall response against Ehrlichia.

View Article: PubMed Central - PubMed

Affiliation: Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta University, Augusta, Georgia, United States of America.

ABSTRACT
Ehrlichiae are gram-negative obligate intracellular bacteria that cause potentially fatal human monocytic ehrlichiosis. We previously showed that natural killer (NK) cells play a critical role in host defense against Ehrlichia during primary infection. However, the contribution of NK cells to the memory response against Ehrlichia remains elusive. Primary infection of C57BL/6 mice with Ehrlichia muris provides long-term protection against a second challenge with the highly virulent Ixodes ovatus Ehrlichia (IOE), which ordinarily causes fatal disease in naïve mice. Here, we show that the depletion of NK cells in E. muris-primed mice abrogates the protective memory response against IOE. Approximately, 80% of NK cell-depleted E. muris-primed mice succumbed to lethal IOE infection on days 8-10 after IOE infection, similar to naïve mice infected with the same dose of IOE. The lack of a recall response in NK cell-depleted mice correlated with an increased bacterial burden, extensive liver injury, decreased frequency of Ehrlichia-specific IFN-γ-producing memory CD4+ and CD8+ T-cells, and a low titer of Ehrlichia-specific antibodies. Intraperitoneal infection of mice with E. muris resulted in the production of IL-15, IL-12, and IFN-γ as well as an expansion of activated NKG2D+ NK cells. The adoptive transfer of purified E. muris-primed hepatic and splenic NK cells into Rag2-/-Il2rg-/- recipient mice provided protective immunity against challenge with E. muris. Together, these data suggest that E. muris-induced memory-like NK cells, which contribute to the protective, recall response against Ehrlichia.

Show MeSH

Related in: MedlinePlus

NK cells in E. muris-primed mice acquire adaptive features and a memory phenotype.CD45+NK1.1+CD3- NK cells were purified from the spleen and liver collected on day 21 from E. muris-primed mice, and ~5–8 x 105 splenic and hepatic NK cells (1:1 ratio) were transferred into naïve Rag2−/−Il2rg−/− mice. Control mice were naïve Rag2−/−Il2rg−/− hosts receiving naïve NK cells. The numbers of memory-like NK cells, as measured by flow cytometry, in recipient Rag2−/−Il2rg−/− mice that received naïve, E. muris-primed or IOE-primed NK cells (A). Rag2−/−Il2rg−/− hosts receiving E. muris- primed NK cells survived longer than mice receiving naïve or IOE-primed NK cells following E. muris infection (B). Bacterial burden in the livers of recipient Rag2−/−Il2rg−/− mice at day 7 following E. muris infection (C). Depletion of contaminating donor CD4+T cells in recipient Rag2−/−Il2rg−/− mice did not influence mice survival following E. muris infection (D). ** indicate P < 0.01. Data are presented as the means ± SD of 3 mice/ group and are representative of two independent experiments. Data are presented as means ± SD from three mice per group. Data shown are representative of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4836677&req=5

pone.0153223.g014: NK cells in E. muris-primed mice acquire adaptive features and a memory phenotype.CD45+NK1.1+CD3- NK cells were purified from the spleen and liver collected on day 21 from E. muris-primed mice, and ~5–8 x 105 splenic and hepatic NK cells (1:1 ratio) were transferred into naïve Rag2−/−Il2rg−/− mice. Control mice were naïve Rag2−/−Il2rg−/− hosts receiving naïve NK cells. The numbers of memory-like NK cells, as measured by flow cytometry, in recipient Rag2−/−Il2rg−/− mice that received naïve, E. muris-primed or IOE-primed NK cells (A). Rag2−/−Il2rg−/− hosts receiving E. muris- primed NK cells survived longer than mice receiving naïve or IOE-primed NK cells following E. muris infection (B). Bacterial burden in the livers of recipient Rag2−/−Il2rg−/− mice at day 7 following E. muris infection (C). Depletion of contaminating donor CD4+T cells in recipient Rag2−/−Il2rg−/− mice did not influence mice survival following E. muris infection (D). ** indicate P < 0.01. Data are presented as the means ± SD of 3 mice/ group and are representative of two independent experiments. Data are presented as means ± SD from three mice per group. Data shown are representative of three independent experiments.

Mentions: We then examined whether E. muris-primed NK cells acquire features of memory cells, namely prolonged survival, in an antigen-free hosts and providing recall response. To this end, we adoptively transferred purified NK cells collected on day 21 from the spleens and livers of E. muris-primed and IOE-primed mice (~5–8 x 105 cells; 1:1 ratio) into recipient Rag2−/−Il2rg−/− mice (which lack T, B and NK cells). Control mice were naïve Rag2−/−Il2rg−/− hosts receiving naïve NK cells. NK cells from E. muris-primed mice were detected in the liver of Rag2−/−Il2rg−/− mice on day 7 after transfer, similar to the observations made in naïve NK cells Fig 14A. Donor NK cells from IOE-primed mice were detected in the liver of Rag2−/−Il2rg−/− mice on day 7 after transfer Fig 14A. However, the number of these cells was significantly lower compared to mice receiving naïve NK cells and E. muris-primed NK cells, suggesting that these primed cells may not be able to survive in lymphopenic host. Taken all together, these data suggest that NK cells from E. muris-primed mice may acquire memory-like phenotype and thus able to survive in lymphopenic hosts and in the absence of T and B cells, and in the absence of persistent E. muris infection


NK Cell-Mediated Regulation of Protective Memory Responses against Intracellular Ehrlichial Pathogens.

Habib S, El Andaloussi A, Hisham A, Ismail N - PLoS ONE (2016)

NK cells in E. muris-primed mice acquire adaptive features and a memory phenotype.CD45+NK1.1+CD3- NK cells were purified from the spleen and liver collected on day 21 from E. muris-primed mice, and ~5–8 x 105 splenic and hepatic NK cells (1:1 ratio) were transferred into naïve Rag2−/−Il2rg−/− mice. Control mice were naïve Rag2−/−Il2rg−/− hosts receiving naïve NK cells. The numbers of memory-like NK cells, as measured by flow cytometry, in recipient Rag2−/−Il2rg−/− mice that received naïve, E. muris-primed or IOE-primed NK cells (A). Rag2−/−Il2rg−/− hosts receiving E. muris- primed NK cells survived longer than mice receiving naïve or IOE-primed NK cells following E. muris infection (B). Bacterial burden in the livers of recipient Rag2−/−Il2rg−/− mice at day 7 following E. muris infection (C). Depletion of contaminating donor CD4+T cells in recipient Rag2−/−Il2rg−/− mice did not influence mice survival following E. muris infection (D). ** indicate P < 0.01. Data are presented as the means ± SD of 3 mice/ group and are representative of two independent experiments. Data are presented as means ± SD from three mice per group. Data shown are representative of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836677&req=5

pone.0153223.g014: NK cells in E. muris-primed mice acquire adaptive features and a memory phenotype.CD45+NK1.1+CD3- NK cells were purified from the spleen and liver collected on day 21 from E. muris-primed mice, and ~5–8 x 105 splenic and hepatic NK cells (1:1 ratio) were transferred into naïve Rag2−/−Il2rg−/− mice. Control mice were naïve Rag2−/−Il2rg−/− hosts receiving naïve NK cells. The numbers of memory-like NK cells, as measured by flow cytometry, in recipient Rag2−/−Il2rg−/− mice that received naïve, E. muris-primed or IOE-primed NK cells (A). Rag2−/−Il2rg−/− hosts receiving E. muris- primed NK cells survived longer than mice receiving naïve or IOE-primed NK cells following E. muris infection (B). Bacterial burden in the livers of recipient Rag2−/−Il2rg−/− mice at day 7 following E. muris infection (C). Depletion of contaminating donor CD4+T cells in recipient Rag2−/−Il2rg−/− mice did not influence mice survival following E. muris infection (D). ** indicate P < 0.01. Data are presented as the means ± SD of 3 mice/ group and are representative of two independent experiments. Data are presented as means ± SD from three mice per group. Data shown are representative of three independent experiments.
Mentions: We then examined whether E. muris-primed NK cells acquire features of memory cells, namely prolonged survival, in an antigen-free hosts and providing recall response. To this end, we adoptively transferred purified NK cells collected on day 21 from the spleens and livers of E. muris-primed and IOE-primed mice (~5–8 x 105 cells; 1:1 ratio) into recipient Rag2−/−Il2rg−/− mice (which lack T, B and NK cells). Control mice were naïve Rag2−/−Il2rg−/− hosts receiving naïve NK cells. NK cells from E. muris-primed mice were detected in the liver of Rag2−/−Il2rg−/− mice on day 7 after transfer, similar to the observations made in naïve NK cells Fig 14A. Donor NK cells from IOE-primed mice were detected in the liver of Rag2−/−Il2rg−/− mice on day 7 after transfer Fig 14A. However, the number of these cells was significantly lower compared to mice receiving naïve NK cells and E. muris-primed NK cells, suggesting that these primed cells may not be able to survive in lymphopenic host. Taken all together, these data suggest that NK cells from E. muris-primed mice may acquire memory-like phenotype and thus able to survive in lymphopenic hosts and in the absence of T and B cells, and in the absence of persistent E. muris infection

Bottom Line: Ehrlichiae are gram-negative obligate intracellular bacteria that cause potentially fatal human monocytic ehrlichiosis.However, the contribution of NK cells to the memory response against Ehrlichia remains elusive.Together, these data suggest that E. muris-induced memory-like NK cells, which contribute to the protective, recall response against Ehrlichia.

View Article: PubMed Central - PubMed

Affiliation: Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta University, Augusta, Georgia, United States of America.

ABSTRACT
Ehrlichiae are gram-negative obligate intracellular bacteria that cause potentially fatal human monocytic ehrlichiosis. We previously showed that natural killer (NK) cells play a critical role in host defense against Ehrlichia during primary infection. However, the contribution of NK cells to the memory response against Ehrlichia remains elusive. Primary infection of C57BL/6 mice with Ehrlichia muris provides long-term protection against a second challenge with the highly virulent Ixodes ovatus Ehrlichia (IOE), which ordinarily causes fatal disease in naïve mice. Here, we show that the depletion of NK cells in E. muris-primed mice abrogates the protective memory response against IOE. Approximately, 80% of NK cell-depleted E. muris-primed mice succumbed to lethal IOE infection on days 8-10 after IOE infection, similar to naïve mice infected with the same dose of IOE. The lack of a recall response in NK cell-depleted mice correlated with an increased bacterial burden, extensive liver injury, decreased frequency of Ehrlichia-specific IFN-γ-producing memory CD4+ and CD8+ T-cells, and a low titer of Ehrlichia-specific antibodies. Intraperitoneal infection of mice with E. muris resulted in the production of IL-15, IL-12, and IFN-γ as well as an expansion of activated NKG2D+ NK cells. The adoptive transfer of purified E. muris-primed hepatic and splenic NK cells into Rag2-/-Il2rg-/- recipient mice provided protective immunity against challenge with E. muris. Together, these data suggest that E. muris-induced memory-like NK cells, which contribute to the protective, recall response against Ehrlichia.

Show MeSH
Related in: MedlinePlus