VACCINOLOGY (BIO-301) Credit Hrs 3(2-1)

Dr. Aneela javed

Part 2: Principles of Vaccine Design

Immunologic Memory: T and B Cells memory

• Antigen Processing and Presentation by MHC Class I, II, and Nonclassical Molecules

• Understanding the Mucosal Immune System for Better Mucosal Vaccine Design

PART 1 : INTRODUCTION• Definition• History • Types• Combination vs single vaccine

Course Contents

Part 3: ANIMAL MODELS FOR VACCNE TESTING

• Utility of Mouse Models in Vaccine Design and Development,

• Utility of Nonhuman Primate Models for Vaccines,

VACCINE PRODUCTION

most of the highly successful vaccines have been made empirically, with little or no immunological insight

Recent advances in innate immunity have offered new insights about the mechanisms of vaccine-induced immunity and have facilitated a more rational approach to vaccine design.

the failure to develop vaccines against global pandemics such as infection with human immunodeficiency virus (HIV) despite decades of effort has underscored the need to understand the immunological mechanisms by which vaccines confer protective immunity

Part 2: Principles of Vaccine Design

Immunologic Memory: T and B Cells memory

• Antigen Processing and Presentation by MHC Class I, II, and Nonclassical Molecules

• Understanding the Mucosal Immune System for Better Mucosal Vaccine Design

1. distinct subsets of helper T cells, such as TH1, TH2 and TH17, are effective at protecting against different pathogens

2. Follicular helper T cells (TFH cells) produce interleukin 21 (IL-21) and help with the differentiation of B cells and generation of memory B cells.

3. In addition, differentiating memory CD4+ and CD8+ T cells can be subcategorized into central memory and effector memory cell subsets, each with a distinct functionality.

Pattern recognition receptors (PRRs) : proteins expressed by cells of the innate

immune system to identify pathogen-associated molecular patterns (PAMPs), which

are associated with microbial pathogens or cellular stress, as well as damage-associated

molecular patterns (DAMPs), which are associated with cell components released

during cell damage.

1. (PAMPs) and include bacterial carbohydrates (such as lipopolysaccharide or

LPS, mannose),

2. nucleic acids (such as bacterial or viral DNA or RNA), bacterial peptides

(flagellin, Xa21),

3.  peptidoglycans and lipoteichoic acids (from Gram positive bacteria), 

4. N-formylmethionine, lipoproteins and fungal glucans.

5. Endogenous stress signals are called danger-associated molecular

patterns (DAMPs) and include uric acid.

The innate immune system can sense microbes through pattern-recognition receptors (PRRs), such as

1. the Toll-like receptors (TLRs), which are expressed by various cells, including dendritic cells (DCs)

2. the C-type lectin-like receptors

3. the cytosolic Nod-like receptors

4. Cytosolic RIG-I-like receptors sense viral nucleic acids

There are many subsets of functionally distinct DCs, and it is now clear that the DC subset, as well as the nature of the PRR, have a key role in determining the magnitude and quality of adaptive immune responses.

1.  dimers, homodimers, TLR2 forms heterodimers

2. endosomal TLRs comprising TLR3, TLR7, TLR8 and TLR9 recognize nucleic

acid derived from viruses as well as endogenous nucleic acids in context of

pathogenic events.

3. Activation of these receptor leads to production of inflammatory cytokines as

well as type I interferons (interferon type I) to help fighting viral infection.

TLRs may also depend on other co-receptors for full ligand

sensitivity, such as in the case of TLR4's recognition of LPS, which

requires MD-2. CD14 and LPS-Binding Protein (LBP) are known to

facilitate the presentation of LPS to MD-2.

When activated, TLRs recruit adapter molecules within the

cytoplasm of cells in order to propagate a signal. Four adapter

molecules are known to be involved in signaling. These proteins

are known as

1.  MyD88, 

2. Tirap (also called Mal), 

3. Trif, and

4. Tram (toll-like receptor 4 adaptor protein).

TLR SIGNALING

http://en.wikipedia.org/wiki/File:Toll-like_receptor_pathways.svg

MyD88-dependent pathway

utilized by every TLR except TLR3.

Its primary effect is activation of NFκB and Mitogen-activated protein kinase

MyD88 then recruits IRAK 4, IRAK1 and IRAK2. IRAK kinases then

phosphorylate and activate the protein TRAF6, which in turn polyubiquinates

the protein TAK1, as well as itself in order to facilitate binding to IKK-β. On

binding, TAK1 phosphorylates IKK-β, which then phosphorylates IκB causing

its degradation and allowing NFκB to diffuse into the cell nucleus and activate

transcription and consequent induction of inflammatory cytokines.[23]

TRIF-dependent pathway[edit]

Both TLR3 and TLR4 utilize the TRIF-dependent pathway,

which is triggered by dsRNA and LPS, respectively. For 

TLR3, dsRNA leads to activation of the receptor, recruiting

the adaptor TRIF. TRIF activates the kinases TBK1 and 

RIPK1, which creates a branch in the signaling pathway. The

TRIF/TBK1 signaling complex phosphorylates IRF3 allowing

its translocation into the nucleus and production of 

Interferon type I. Meanwhile, activation of RIPK1 causes the

polyubiquitination and activation of TAK1 and NFκB

transcription in the same manner as the MyD88-dependent

pathway.[23]

.

TLR signaling ultimately leads to the induction of thousands of genes. TLRs

constitute one of the most pleiotropic yet tightly regulated gateways for gene

modulation

Receptor Ligand(s)[27]Ligand

location[27]Cell types[27]

TLR 1 multiple triacyl lipopeptidesBacteria

monocytes/macrophages a subset of dendritic cells B lymphocytes

TLR 2

multiple glycolipids Bacteria

monocytes/macrophages neutrophils [28]

Myeloid dendritic cells[29]

Mast cells

multiple lipopeptides Bacteria

multiple lipoproteins Bacteria

lipoteichoic acid Gram-positive bacteria

HSP70 Host cells

zymosan (Beta-glucan) Fungi

Numerous others

TLR 3double-stranded RNA, poly I:C

viruses Dendritic cells B lymphocytes

TLR 4

lipopolysaccharide Gram-negative bacteria

monocytes/macrophages neutrophils [28]

Myeloid dendritic cells[29]

Mast cells B lymphocytes [30]

Intestinal epithelium

several heat shock proteinsBacteria and host cells

fibrinogen host cells

heparan sulfate fragments host cells

hyaluronic acid fragments host cells

nickel

Various opioid drugs

TLR 5

flagellin Bacteria

monocyte/macrophages a subset of dendritic cells Intestinal epithelium

[[profilin[31]]]Toxoplasma gondii

TLR 6 multiple diacyl lipopeptides Mycoplasma

monocytes/macrophages Mast cells B lymphocytes

TLR 7

imidazoquinolinesmall synthetic compounds

monocytes/macrophagesPlasmacytoid dendritic cells[29]

B lymphocytes

loxoribine (a guanosine analogue)

bropirimine

single-stranded RNA RNA viruses

TLR 8small synthetic compounds; single-stranded RNA

monocytes/macrophages a subset of dendritic cells Mast cells

TLR 9unmethylated CpG Oligodeoxynucleotide DNA

Bacteria, DNA viruses

monocytes/macrophagesPlasmacytoid dendritic cells[29]

B lymphocytes

TLR 10 unknown

TLR 11 ProfilinToxoplasma gondii[32]

monocytes/macrophages liver cells kidney urinary bladder epithelium

TLR 12 ProfilinToxoplasma gondii[34]

Neurons[35]

plasmacytoid dendritic cells conventional dendritic cells macrophages

TLR 13 [36][37]

bacterial ribosomal RNA sequence “CGGAAAGACC”

Virus, bacteria monocytes/macrophages conventional dendritic cells

Cell type TLR

Monocyte 1,2,4,5,6,7,8,9

Macrophages

Dendritic cells

Conventional DC

Plasmacytoid DC

B cells

Neutrophils

Mast cells

Intestinal epithelium

•Cellular immunity• Maximizes the killing efficacy of the macrophages •proliferation of cytotoxic CD8+ T cells.•promotes the production of opsonizing antibodies. (IgG, IgM and IgA but not IgE antibodies)

•Humoral immune system.

•Stimulates B-cells into proliferation,

•induce B-cell antibody class switching,

•Increasesneutralizing antibody production

(IgG, IgM and IgA as well as IgE antibodies)

Th17 helper cells mediate host immunity

against extracellular bacteria and fungi.

The regulatory T cells (Tregs), formerly known as suppressor T cells, maintain tolerance to self-antigens, and abrogate autoimmune disease.

IMMUNE MEMORY

T cell-dependent activation

1. The T cell is stimulated to produce autocrines, resulting in the proliferation or

differentiation to effector or memory T cells.

2. A certain portion of the resulting effector T cells then activate specific B cells through

a phenomenon known as an Immunological synapse.

3. Activated B cells subsequently produce antibodies that assist in inhibiting pathogens

until

T cell-independent activation

1. An advantage of forgoing T cell involvement is that an expedited immune response can be mobilized,

2. germinal center formation, isotype switching and affinity maturation do not occur during this form of activation.

3. Also, because almost all memory B cells are derived from germinal centers, effective antibody-mediated memory is

4. against polysaccharide capsules of encapsulated bacteria

Live attenuated vaccines such as those against smallpox or yellow fever are the

most successful vaccines ever made and can confer lifelong memory, whereas

nonliving vaccines induce protection of much shorter duration and require

booster vaccination to maintain protective immunity. Thus, a single dose of the

smallpox vaccine maintains serum antibody titers for more than 50 years and

cellular immunity is also maintained for decades.

engagement of multiple innate pathogen recognition receptors is key to

generating T-cell responses of different magnitudes and functional profiles

[6, 12–14], suggesting that, the overall breath, functionality and

duration of acquired immune responses are dictated by early

innate signals triggered by live attenuated vaccines [6, 12–14].