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Harro Frauendorf. Adjuvants. an adjuvant is an agent that may stimulate the immune system and increase the response to a vaccine, without having any specific antigenic effect in itself much purified antigens doesn't occur in immune response during vaccination

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adjuvants
Adjuvants
  • an adjuvant is an agent that may stimulate the immune system and increase the response to a vaccine, without having any specific antigenic effect in itself
  • much purified antigens doesn't occur in immune response during vaccination
  • adjuvants accomplish this problem by mimicking PAMPs or several mechanisms that stimulate DCs
  • many agents with adjuvant activity, such as bacterial endotoxin, Freund ’ s adjuvant, bacterial CpG motifs, monophosphoryl lipid A, MF59, and -galactosylceramide boost immunity through induction of DC maturation
slide3
ALUM
  • aluminium hydroxide
  • inorganic adjuvant, that induce humoral immunity
  • most common adjuvant in human vaccines
  • no consensus regarding the mechanisms by which they potentiate the immune system
  • it has been less clear if and how aluminum-containing adjuvants can induce DC mobilization and maturation
      • in view of the crucial role of DCs in activation of adaptive immunity, we therefore set out to carefully study the effects of alum on DCs and their monocytic precursors in vivo after i.p. and i.m. injection of antigen (Ag) in alum
distribution of the primary immune response after i p injection of ova

+10µg OVA

i.p.

analyse

analyse

BALB/c +

CFSE labeled OVA specific CD4+Tcells

1 2 days after transfer 4

  • day 1-3 T cell responses restricted to draining LN
  • by day 4 also nondraining LN + spleen

no „systemic immunization“

localization caused by an artifact induced by skin puncture

Distribution of the primary immune response after i.p. injection of OVA
effect of alum adjuvant on the immune response induced by an i p or i m injection of ova
Effect of alum adjuvant on the immune response induced by an i.p. or i.m. injection of OVA
  • primary T cell response more pronounced in mice receiving OVA and alum
  • increase in CFSE content caused not only by division but also by recruitment of naive Ag-specific cells
effect of alum adjuvant on the immune response induced by an i p or i m injection of ova1
Effect of alum adjuvant on the immune response induced by an i.p. or i.m. injection of OVA
  • by day 7 the Tg T cells persisted in the draining and nondraining nodes and spleen in mice receiving OVA-alum
  • persisting cells in the mediastinal nodes had Th2 effector potential in the OVA-alum group, as they produced IL-4, -5, and -10, but little IFNγ
  • similar cytokine production in non draining LN
response of innate immune system cells to i p injection of ag in adjuvant
Response of innate immune system cells to i.p. injectionof Ag in adjuvant
  • dramatic reduction of resident F4/80 high CD11b high peritoneal macrophages
  • rapid recruitment of monocytes

(immediate precursers for DCs)

  • increase of innate immune cells

 to explain the increase they measured the levels of chemokines 2 h after injection of saline, OVA, or OVA-alum

response of innate immune system cells to i p injection of ag in adjuvant1
Response of innate immune system cells to i.p. injectionof Ag in adjuvant
  • marked increase in the levels of the monocyte chemotactic protein (MCP1;

CCL2), the neutrophil chemotaxin KC (CXCL1), and the eosinophil

chemotaxin eotaxin-1 (CCL11) in mice receiving OVA-alum

  • OVA by itself induced an intermediate level of MCP-1 compared
  • with saline- or OVA-alum-injected mice.
ag uptake and processing by recruited dcs
Ag uptake and processing by recruited DCs

Study the effects of alum on several functional aspects of DCs

OVA-DQ:

OVA conjugated with BODIPY fluorochrome that fluoresces in the green channel when taken up by cells and in the red channel when it accumulates at high densities inside endosomal Ag-processing compartments

  • DCs captured Ag but the mean fluorescence intensity representing the amount of

Ag taken up was higher when alum was added

  • took up and processed more Ag than OVA-DQ – treated mice
  • they expressed more MHC class II than the OVA-DQ neg cells, indicating that

the DCs that took up and processed Ag also functionally matured

ag uptake and processing by recruited dcs1
Ag uptake and processing by recruited DCs
  • DC maturation marker CD86 (and CD40) was induced on DCs within 6 h, and

started to return to baseline from 24 h onwards

  • effect of alum on DC maturation was most likely indirect, as exposure of purified

BM-derived DCs to alum in vitro did not lead to any direct DC activation

  • The ultimate definition of DC function is the potential to present Ag to naive T cells.
  • only DCs derived from OVA-alum-immunized mice induced T cell proliferation of

naive DO11.10 OVA-specific T cells ex vivo

slide11

Injection of alum promotes Ag uptake by recruited monocytes and induces their migration and conversion into CD11c+ DCs in the draining nodes

  • Injection of OVA-alum induced the recruitment of inflammatory monocytes to the

peritoneal cavity

  • inflammatory monocytes massively took up more Ag
  • monocytes processed and internalized Ag
  • monocytes were sorted from MLN, and they induced ex vivo proliferation of

DO11.10 T cells

slide12

Injection of alum promotes Ag uptake by recruited monocytes and induces their migration and conversion into CD11c+ DCs in the draining nodes

  • upregulation of CD86 (CD40), MHCII

and most importantly CD11c integrin,

a classical marker of DCs

  • findings were largely descriptive
  • and not excluding the possibility
  • that LN resident monocytes
  • acquired the Ag and up-regulated
  • CD11c in situ
  • Transfer of of CD45.2 monocytes in

CD45.1 recipients

  • migration to MLN strongly amplified by

the addition of alum

  • 36h after transfer 25% express MHC II

CD11c, indicative of conversion to

DCs

slide13
Functional effect of depleting resident or recruited DCs on T cell priming and humoral immune response induced by OVA or OVA-alum

Hypothesize: in the absence of alum, Ag was presented by resident nonmigratory LN APCs that acquired the Ag via the afferent lymph, whereas in the presence of alum, Ag was presented by recruited inflammatory monocytes and DCs that migrated to the nodes

 transgenic mice in which DCs can be conditionally depleted by administration

of diphtheria toxin

slide14
Functional effect of depleting resident or recruited DCs on T cell priming and humoral immune response induced by OVA or OVA-alum

DT was administered locally via the intratracheal (i.t.) route, leading to a depletion of mediastinal-resident LN, as well as lung-derived migratory DCs, whereas leaving all other DCs unaffected

T cell proliferation (measured 3 d after injection of OVA) was abolished in the MLN in mice receiving OVA, but not those receiving OVA-alum

slide15
Functional effect of depleting resident or recruited DCs on T cell priming and humoral immune response induced by OVA or OVA-alum
  • no proliferation of T cells after transfer in

DC-depleted mice

  • injection of monocytes 2 h after injection
  • of OVA-alum restored T cell divisions
  • humoral response depends on DCs
slide16
The immunopotentiating effect of alum depends on induction of uric acid and signaling through the MyD88 pathway

alum induced a strong neutrophilic influx, accompanied by the production of CXCL1 (KC) and CCL2 (MCP-1), akin to the response seen when the endogenous danger signal uric acidis injected into the peritoneal cavity

  • increased uric acid level in

OVA-alum treated mice

  • monocyte recruitment is

abolished in mice treated with

uricase

  • T-cell division abolished back

to control level

slide17
The immunopotentiating effect of alum depends on induction of uric acid and signaling through the MyD88 pathway
  • peritoneal response to uric acid is heavily dependent on the IL-1 receptor

and downstream MyD88 signaling

conclusion
Conclusion
  • Alum induce no „systemic immunization“ but in enhanced

recruitment of immune cells

  • monocytes develop in DC´s and activate T cells
  • Alum boost based on enhanced MyD88 signaling