IMMUNOSTIMULANTS

Yasmine Hosny Mohamed

Immunostimulant classification

1-Specfic immunostimulant : vaccine and antigen

2-Nonspecific immnuostimulant : act irrespective of antigenic specificity

To augment immune response of other antigens or

stimulate components of immune system without antigenic specificity.

as Adjuvants

3-Other types

Vaccine types

■ Live attenuated vaccines (MMR vaccine, rotavirus)

■ Inactivated vaccines ( influenza , polio)

■ Recombinant subunit vaccine ,Conjugate vaccine

(Hepatitis B , pneumococcal disease) (Haemophilus influenza)

■ Toxoid vaccines (diphtheria tetanus antitoxin)

■ Conjugate vaccine

■ Immunization of capsular polysaccharides (weak immunogen in children)

conjugated to protein antigen of anther pathogen (strong immunogen)

■ T-independent antigen bound to T-dependent antigen

capsular polysaccharide bound to diphtheria toxoid

■ Subunit vaccines

■ Structural parts of infectious antigen obtained from pathogen by genetic

engineering

BCG Vaccine

▪ (Live attenuated mycobacterium bovis for tuberculosis and primary and relapsed bladder carcinoma)

▪ Mode of action

▪ Granulomatous reaction induction at site of administration ,raising activity of T killer cells

■ Avoids lysosomal fusion in macrophages ,decreasing peptides required for activating T cytotoxic cells and T helper 1 immunity.

▪ Macrophages infected by factor H opsonized BCG secrete cytokine for(strong T cell memory response, T fh cell polarization in lymph node leading to B cell maturation memory response)

▪ Opsonized BCG are killed quickly, reducing time of Ag presentation

■ Prolonged Ag presentation on macrophage receptor(TLR) down regulates MHCII expression and reduces MHCI Ag cross processing decreasing Ag presenting to T cells

• Low T cell proliferation.

■ BCG induced antibodies formation as result of cytokine activation

and creating specific environment that leads to polyclonal

effector T cells (or NK cells activation) and production of AB

(memory B cells)

■ Given intravesically , contraindicated for immunosuppressed

patients live organism causing tuberculosis.

■ Nonspecific vaccine may be due to protection against conditions

not related to mycobacteria(early state of bladder cancer)

▪ Side effects: fever, shock ,hypersensitivity

Septic shock for systemic infection

Bacterial vaccines (Prevnar® Pneumonal 13 Valent vaccine)

■ Prevent pneumonal infection of 13 polysaccharide of capsular antigen of streptococcus pneumonia serotypes

Mechanism of action:

B cells produce antibodies via antigenic activation T –independent(polysaccharide) and T -dependent(protein) mechanisms

Protein-carrier-specific T cells signals for maturation of B cells (memory )to elicits booster response on reexposure in children.

■ Given not earlier than 6 weeks , leaving 2 months to pass between vaccines for children

■ Given once in adults

■ Side effects:

■ Fever, diarrhea ,rash , fatigue

Viral vaccine (Specific Immunostimulant)

Contains inactivated virus or live attenuated one + adjuvantAs typhoid vaccine and inactivated (still immunogenic) influenza vaccine.

Mechanism of action

Induction of antibody production within 2 weeks of vaccination

Vaxigrip :

Contains 3 inactivated split of influenza virus strains in propagated hens eggs +hemaglutinin (surface antigen)

Changing vaccine composition every year (different types of strains)

Avoid in egg sensitive individuals, safe for immunodeficient individuals.

Colony Stimulating Factor

Glycoproteins hematopoietic growth factors for formation of non lymphoid blood cells

2 available commercial types (biotechnology)

■ 1-Granulocyte colony stimulating factor

■ 2- Granulocyte- Macrophage colony stimulating factor

■ Belongs to cytokines ,endogenous G-CSF production is induced by exposure to bacterial cell wall proteins ,endotoxins , lineage specific CSF that is produced by monocytes, fibroblasts

■ Mechanism of action :

■ Activates proliferation and maturation of hematopoietic progenitor cells to mature neutrophils also increasing neutrophils phagocytic activity prevent infection

■ Activation of G-CSFR signal transduction causes Jak protein kinase phosphorylation and JAK pathways activated for induction of neutrophil marker protein and proliferation of granulocytes.

■ Pharmacokinetics

■ Onset : 24 hours , time to peak: 2-8 hours (subcutaneous) and 24 hr(intravenous)

■ Duration: ANC decrease 50%within 2 days after discontinuation of filgrastim

■ Systemic degradation

■ T50% :3.5 hours (high conc in bone marrow kidney liver)

■ Pharmacodynamics

Rapid increase in WBC within 2-3 days(normal patients)

Side effect: Muscloskeletal pain frequent , thrombocytopenia and bone pain

Contraindications:

■ rapid proliferating myeloid cells leading to lymphoid infiltration as G-CSF acts as growth factor for myeloid malignancies and myelodysplasias

■ Cytogenetic transformation to MDS and AML observed in patient treated with filgrastim

■ Only given following induction and consolidation chemotherapy treatment (AML)

Splenomegaly (rupture)

Sickle cell anemia cause SC crisis

Hypersensitivity.

■ Drug interactions:

Lithium may potentiate myeloproliferative effects of filgrastim.

▪ For non myeloid malignancy neutropenic episodes.

■ GM-CSF more inflammatory than G-CSF, used

■ Filgrastim should not be used from 24 hours before to 24 hours after chemotherapy

because it act as a growth factor for any tumor (of myeloid type)

■ Pegfilgrastim indications :

Acute myelosuppressive radiation

▪ Peg-filgrastim (granocyte 34miu /ml) not given between 14 days before and 24

hours after chemotherapy. GM-CSF (sargramostim)

GM-CSF

▪ Stem cell transplantation associated neutropenia

▪ Acute myeloid leukemia after allogeneic stem cell transplantation

Epoietin (Red blood cells stimulating factor)

■ Erythropoietin hormone stimulates bone marrow production of red blood

cells.

Mechanism of action:

■ Epoietin bind to EPO-R on Erythroid progenitor cells surface and

conformational change occur that brings EPO-R- associated tyrosine kinase

molecules (JAK2) to be activated via phosphorylation

■ serve as binding sites for domain containing intracellular signaling proteins

Signaling proteins phosphorylated by JAK2 dissociates from EPO-R

they translocate to nucleus to activate target genes for division

■ Metabolism

■ Cellular internalization

(degradation of ligand by reticuloendothelial scavenging pathway of

lymphatic system).

■ optimum peak levels and time for peak level found to be several folds

with weekly regimens.

■ Treating anemia associated with chronic kidney failure and

myelosuppressive chemotherapy.

■ Given intravenous or subcutaneous

■ longer half life formulation(darbepoetin®) for renal failure patients

■ SC mostly for anemic as epoietin has shorter half life and SC injection

allow slow absorption and slow decline level

■ Interferons ( α ,β , gamma)

▪ Interferons are naturally occurring cytokines with antiviral ,anticancer

and immunomodulatory actions

▪ Release triggered by viral infections , active against solid tumors and

hematologic malignancies ,also used for multiple sclerosis.

■ Mechanism of action:

1- Inhibition of viral replication in infected host cell by binding to cellular

receptors then initiating series of intracellular events (induction of certain

enzymes ,inhibition of proliferation and enhancement of immune

response)

2- Increased macrophages phagocytosis and activation of T cytotoxic

lymphocytes.

Usually used in combination with chemotherapeutic drugs or radiation

■ Type I interferons system involves single form of IFNβ, several variants of IFNα

■ when IFNI produced by malignant cells or tumor infiltrating dentritic cells (after activation of pattern recognition receptors) ,They signal via IFN α/ βreceptor 1 heterodimer receptor to transactivate IFN stimulated genes (ISGs) by transcriptional upregulation of ISGs

■ they control autocrine or paracrine circuits that affect cancer immunosurveillance

■ Many anticancer drugs effective only in presence of intact type I IFN signalling

■ Intratumoral expression levels of type I INFs or IFN stimulated genes correlate with good therapy

■ Intratumoural type I IFN signalling contributes to efficacy of allogeneic T

cell therapy ,(that mediates graft-versus leukemia effect), and of

radiation

A- Cyclophospamide

Stimulate production of IFNs by Myeloid progenitor cells in BM

B- Oncolytic viruses , anthracyclines (promote activation of TLR 3 by cancer

cell-derived RNA)induce secretion of type I IFNs by cancer cells or myeloid

cells as dentritic cells in tumor bed.

When secretion within cancer cells (neoplastic lesions ) increased

immunomodulation effect occur

C- Activity of ionizing radiation might involve production of IFNs within

tumor draining lymph nodes

■ Melanoma tumors with loss of IFNγ signalling lack response to therapy

( antibody blockade of inhibitory CTKA-4 pathway)

Anti CTKA -4 enhances T cell responses

■ Interactions :

Interferons reduce theophylline clearance

Affect CNS functions, increase neurotoxic effects of previously or concurrently

administered drugs.

Side effects:

Fever , myalgia ,itching , depression and psychotic disorders

Hematologic side effect (decrease of hematological values) during treatment

period

Cardiotoxicity and hepatotoxicity

■ Actimmune (Interferon γ 1b) for granulomatous disease and malignant

osteopetrosis , renal cell carcinoma

■ Anovex (Interferon β-1a) for multiple sclerosis

■ Reiferon (Interferon α-2a ) for chronic hepatitis C , hairy cell leukemia

and chronic myelogenous leukemia

■ Interleukins

Interleukin -2 (IL-2) aldesleukin® lymphokine

■ non specific T cell growth factor produced by activated Th lymphocytes,

■ It induces T cell proliferation and differentiation to T cytotoxic cells and Treg cells, the capacity of IL2 to promote suppressive capalibility of T reg show antagonism of its effects.

■ IL-2 induces interferon gamma, TNF , IL1 production

Indications

■ Renal cell carcinoma and malignant melanoma (are refractory to chemotherapy)

High dose IL-2 FDA approval in advanced melanoma.

Treating patients with human immunodeficiency virus

Pharmacokinetics

Intravenous infusion and distribution to extracellular spaces

70% of dose undergoes hepatic renal and pulmonary uptake.

= 85 minutes

IL-2 signaling triggers 3 pathways

■ IL-2 is comprised of 3subunits (in 3 different combinations

■ Signaling through intermediate affinity subunits ,

■ binding to these intermediate subunits ,IL-2R recruits JAK1 and JAK3

that cause downstream signaling through STAT5,phosphatidylinositol

bisphosphate 3-kinase or mitogen-activated protein kinase pathways

■ Therefore expression of FoxP3 transcription factor

■ Conventional T cells downregulate phosphatase upon antigen stimulation

■ IL-2 signaling in conventional T cells results in signaling through STAT5 ,

PI3K and MAPK pathways only STAT5 signaling is induced only in Treg

due to activation of phosphatase and inhibition of MAPK-PI3K pathway

(not in Tcells which downregulate phospahatase upon antigen

stimulation

■ Antitumor effects IL-2 promote T CD4 andCD8 T lymphocytes

through PI3K and MAPK signalling enhances bcl-2 expression and

induction of cyclines for cell cycle progression survival

■ enhances tumor reactivity and clearance , IL-2 control production of

IFNγ,increasing expression of MHCmolecules (antigen presentation)and

recognition of tumor cells and IL-2 induce expression of perforin and

granzymes (proteases) mediate cytotoxic potential of T cells to tumor

antigen

■ IL-2 induce vascular permeability through activation of endothelial

cellsvia IL-2 induced cytokines ie IL-1 TNF IFN γ also IL-2 stimulate

chemokines production ie GM-CSF , macrophage inflammatory protein

■ Therefore IL-2 main mechanism lie in activation of macrophage

monocytes and recruitment of T lymphocytes into tumor

■ Rapid decrease in circulating T cells after IL-2 infusion

■ Adverse effects

Nausea- vomiting , hypotension , anemia , pulmonary congestion and

impaired kidney, liver function

Depression

Capillary leak syndrome (hypotension ,reduced organ perfusion due to

extravasation of plasma proteins and fluid)

Contraindicated in cardiac, CNS impaired patients

Immunoglobulin intravenous therapy(non specific immunostimulant)

■ IGIV therapy immunoglobulin is purified preparation of gamma globulin derived from pooled human plasma from 3000 to 10,000 healthy donors

■ The entire variable(antigen binding ) regions of antibodies in normal serum are contained in IGIV .

IG administrated IV and SC (IV peak level immediately, IM within 2 days)

But serum IgG level drops to 50% during first week after infusion

▪ Mechanism of action

Antiinflammatory and immunomodulatory activity

Modulation of complement activation

Suppression of idiotopic antibodies

Saturation of Fc receptors on macrophages decreasing autoantibody

Mechanism of action

■ Fc immunoglobulin region ,rather than Fab region , responsible for therapeutic effect of IVIG

■ Fc regions in IVIG provide blockade of macrophage Fc receptors ,inhibiting Fc mediated phagocytosis of autoantibody –opsonized platelets

■ Fc receptors are expressed with high levels on vascular endothelial cells for sequestering IgG antibodies in endocytic vesicles before returning them intact to circulation.

■ IVIG may saturate these protective resulting in destruction of pathologic and non pathologic IgG .

■ After IVIG fusion with lysosome, unbound IgG is degraded while FcRn

bound IgG don’t enter lysosome , remain intact and returned to plasma

■ And release from FcRn as PH neutral.

■ As IgG serum concentration rise, IgG decrease because increasing

conc of IgG result in saturation of FcRn therefore more IgG molecules

enter lysosome and catabolized

■ Human IgG result in lower IgG conc than normal IgG serum conc ,

with llonger than normal .

■ SCIG result in trough fluctuation absence and higher trough levels

compared with IVIG.

▪ Indications

▪ Replacement therapy in immunodeficiency status(autoimmune diseases)

Hepatitis A prophylaxis, hypogammaglobinemia and chronic lymphocytic

leukemia and multiple myeloma with specific antibody deficiency ,Myathenia

gravis (off-label) and Guillian- Barre syndrome (licensed)

FDA approved for idiopathic thrombocytopenia purpurea (second choice for

decades).

Non specific Immunostimulants

Adjuvants

■ Alum : Alum/vaccine complex injected into body ,slowly dissolves

Releasing vaccine

Stronger immunogenic response when used in combination with specific antigen

Examples: liposomes, saponins ,microbial products

1-Effective immune response in low response populations

2-Provide use of smaller amounts of antigen (safe)

3-Alum enhances diphtheria toxoid immunization in humans

In 2008 , cytotoxicity of aluminium salts leads to uric acid release

Non specific immunostimulants

■ Plants products

■ High molecular weight polypeptides (lectins) are glycoproteins

■ Mechanism of action: bind T lymphocytes induce mitosis and some

interferon inducing potential immune stimulation.

■ High molecular weight polysaccharides aqueous extract of large number

of plants increase phagocytosis the complex

■ Anionic structure of polysaccharide enable high binding affinity to

membrane of immunocompetent cells as compared with glycan chains

■ Examples: Echinacea purpurea

Chamomilla recutita

■ Prebiotics :

■ Various group of polysaccharides (oligosaccharides)

■ Non digestible polysaccharides

■ Fermented by intestinal microflora and act as substrate for beneficial bacteria colonizing in colon (Lactobacillus, Clostridium)

■ Prebiotic polysaccharides as galactans ,fructans restore composition of colonic microflora )

Exist in leafy vegetables (lettuce ,spinach and celery )

Immunostimulant:

1- Direct interaction with PRR (pattern recognition receptor) on innate immune cells

2- Associate with MAMP(microbe associated molecular patterns) to activate immune system

■ Herbals as immunostimulants

■ Saponin , diacylglyzerol derivatives and polyphenols are potent

immunostimulants

■ Pungent capsaicin and safrol cause in vivo activation of non specific

immune system (counterirritant effect)

■ β glycans immunostimulant of cell wall of yeast increase phagocytic

and bactericidal action of macrophages of host

■ Brochovaxom ( specific oral vaccines)

■ Lyophilized bacterial lysates of Haemophilus influenza ,Diplococcus

pneumoniae ,klebseilla pneumoniae ,Staphylococcus aureus and

streptococcus pyogenes , Neisseria catarrhalis

■ For Children and adults

■ Mechanism of action

■ Macrophage stimulation ,increasing circulating T lymphocytes and

immunoglobulins secreted respiratory mucous membranes.

■ Modulation of signal transducer gp130 and gp130 binding binding

cytokines

■ Increased T and B cell activity by IL-6 production, IgM to IgG switch

■ Stimulation of innate immune system by interacting with GI mucosa and

mucosal membrane within respiratory tract

■ Activity of gut –associated lymphoid tissue enhances lymphocytic

presentation of bacterial antigens exist in vaccines and induces

production and secretion of antigen specific secretory IgA antibodies in

mucosal membranes of GI and respiratory tract.

■ Bronchovaxom Dosage regimen

Daily over 3 months period provides 6 month coverage.

Contraindicated in immunocompromised AIDS patients , hepatitis and

autoimmune

Lactoferrin :

■ Iron Binding Glycoprotein host defense against pathogenic organisms 2

molecules of it is component of neutrophil granules free lactoferrin in

human tears ,semen ,milk

■ antimicrobial activity of lactoferrin due to depletion of iron ,

■ high local concentration leave insufficient free ferric ion to support

bacterial growth

■ lactoferrin stimulate growth of beneficial bacteria (lactobacillus)

■ Pravotin® for anemia

■ Mode of action:

1-sequester lipopolysaccharides and preventing inflammatory

pathway activation, sepsis

2-bridges innate and adaptive immune responses

Iron sequestration reduce oxidative stress and cytokine production

T cell maturation and differentiation and B cell conversion into APC.

LF bind lipopolysaccharide and CD14 ,interfering with complex

formation stopping sepsis pathogenesis.

3-hemorrhagic stroke ,the increase of iron due to uptake of transferrin

and lactoferrin receptors on neurons allow transporting iron across

neuron membranes

▪ Deoxycholic acid

It is mammalian bile acid ,not formed by liver ,metabolic byproducts of

intestinal bacteria

■ Endogenous immunostimulant effect is under investigation

■ It is thought through macrophages activation of innate system

Spirulina

Dietary supplement immunomodulator : exhibits anti-inflammatory

(inhibit histamine release by mast cells)

Reducing IL-4 and increasing IFN- γ and IL-2 which are regulating IgE

mediated allergy

Enhances IgA production for mucosal immunity