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Delivery of siRNAs to Target Cells via Antibody-Protamine Fusions
1. Antibody mediated in vivo
delivery of
small interfering RNAs
via cell-surface receptors
From “nature biotechnology”
Presented by
V.Esakki Muthu Lakshmi
6. Need for protamine-antibody fusion
Protamine
Cationic peptide
Binds to C terminus of Ab
Links Ab and siRNA
To avoid
Nonspecific gene silencing
Toxicity in bystander cells
7.
8. Targeting of HIV env+ cells
COS cells
Fibroblast like cell line
Medium-RPMI1640 with 10% fetal bovine serum
Transfection with pCMV-F105-P
Collection of F105-P*
B16 cells
Melanoma cells
Transfection with expression vector for HIV env
FITC*-siRNA
FITC*-Flourescin isothio cyanate
F105-P* – protamine antibody against HIV env
9. F105-P binding assay
Addition of 200 pmol FITC-siRNA
Anti-protamine coated protein bound F105-P
overnight incubation at 4°C
Thorough washing to remove unbound FITC-siRNA
Determination of absorbance at 488nm
Construction of standard curve
11. siRNA delivery
Mixing of F105-P & gag siRNA (6:1)
Incubation of mixture in PBS at 4°C
Addition of mixture to cells(B16)
Transfection of cells with oligofectamine*(control)
Analysis of gene expression 2days after of siRNA
delivery
gag siRNA-gene silencing in HIV env expressing cells
Oligofectamine*-tranfection reagent
13. Analysis of target gene silencing
Transfection of HeLa* cells with plasmid encoding
EGFP
Tranfection of HeLa-GFP with HIV λHXB3
Treating of culture with F105-p EGFP siRNA
Analysis of HIV & GFP expression 2d after treatment
GFP expression by northern blot
HeLa*-immortal cell line
EGFP-enhanced green flourescent protein
14. RESULT
Absence of gene silencing
untransfected gag p24(-) cells
Irrelevant fas siRNA
Unmodified F105 in place of F105-P
Loading
control
15. Inhibition of HIV in infected T cells
Collection of CD4 T cells from normal donor
Stimulation with phytohemagglutinin*(4μg/ml) for 4d
Infection with HIV strain III B at a MOI of 0.1
Treating cells with F105-P -gag siRNA
Analysis of HIV replication
Phytohemagglutinin*-mitogen
16. RESULTS
Reduction in infected cells(85%-36%)
HIV gag staining-45%
ELIZA for HIV p24
Concentration of viral particle -170 ng/ml to
40 ng/ml(100 pmol of siRNA)
24. Determination of specificity
BL6/C57 mice
Subcutaneous injection of gp160-B16 cells(2× 106 )
Intravenous injection of 50μg F105-P-FITC
siRNA(day 9)
Transfection with oligofectamine
Cryosectioning of tumor from killed mice(16h)
OBSERVATION
Effect on gp160+ tumor cells
Flourescent signal in membrane & cytoplasm,not
in tumor cell nucleus
25.
26. Is there any inflammatory responses?
Possibilities
Trigger an interferon responses
Binding of siRNA to TLR*
q RT-PCR
Interferon beta
2’,5’-oligoadenylate synthetase
Stat-1
Observation
No interferon responses
TLR*-Toll like receptor
28. Single chain fragment variable
2 variable domains-VH&VL
High antigen specificity
29. Anti ErB2 ML39 scFV production
Transfection of SF9 cells with virus(ML39 scFV)
Extraction of ML39 scFV by 6M GuanHCl
Purification by Ni++ chromatography
Dialysis with PBS containing 5%glycerol,0.5M
arginine,1mM EGTA,1mM glutathione
Final dialysis with PBS containing 5%glycerol
30.
31.
32. FITC siRNA delivery by ML39 scFV-P
Targeting cells
ErB2 expressing cells
MCF7 breast cancer cells
SKBR3 cells
Observation
effect only in ErB2+ cells
Ku70 silencing in ErB2+ SKBR3 cells
Dose of ML39 scFV-P – 1000pmol
33.
34. Conclusion
Rate limiting factor
Short in vivo half-life
Filtering of siRNA
Prone to Rnase activity
Gene silencing enhancement
Modified siRNA
Cocktails of siRNA
Chemokine analog