1 research outputs found
Enhanced immunomodulatory applications of nucleic acid encapsulating liposomes
Ankara : The Department of Moleculer Biology and Genetics and the Institute of Engineering and Science of Bilkent University, 2009.Thesis (Master's) -- Bilkent University, 2009.Includes bibliographical references leaves 82-90.Recent studies have demonstrated that innate immune system has great ability to
discriminate self from non-self through the action of innate immune receptors. The most
extensively studied innate immune receptor family is the Toll-like receptors (TLRs).
Endosomal/intracellular TLR3, TLR7/8 and TLR9 recognize dsRNA, ssRNA and unmethylated
CpG DNA respectively. Upon activation following recognition of nucleic acids by endosomal
TLRs, B cells secrete IL6, dendritic cells and macrophages secrete type I IFNs, IL12 and NK
cells secrete IFNγ which yields Th1 type immune response. Modulating the immune response to
mount such an immune response by TLR ligands are harnessed in medical applications such as
anticancer, antiviral, antibacterial therapies, anti-allergen, as vaccine adjuvant and as
immunoprotective agents.
Promising clinical applications of TLR ligand nucleic acids are hampered due to their
premature in vivo digestion by endonucleases and rapid clearance via serum protein absorption
leading to limited stability and bioavailability. A powerful tool to overcome this problem can be
achieved by encapsulating TLR ligands within liposomes, which increase in vivo stability as well
as augment targeting and internalization to relevant innate immune cells.
In this study we aimed to establish the most immunostimulatory liposome type
encapsulating or coencapsulating CpG ODN and pIC. Five different liposomes possessing
different physicochemical properties were prepared and their immunostimulatory potential when
nucleic acid TLRs are loaded, were assessed. Following stimulation of splenocytes with
combinations of these liposome types we have observed that neutral, anionic and stealth
liposome encapsulating D-ODN, led to a dose dependent significantly higher IFNγ production
over free counterpart. Stealth liposome encapsulating pIC induced both IL6 and IFNγ 10 and 250
fold respectively over free pIC. Neutral and anionic liposome coencapsulating D-ODN with pIC
were very strong type 1 IFN as well as Th1 cytokine inducers both in vitro and ex vivo. Then, we
immunized B6 mice with anionic liposome coencapsulating D-ODN and OVA to establish the
immuno-adjuvant properties of liposome formulations in vivo. We assessed primary and
secondary anti-OVA IgG subclass responses of mice. Results strongly implicated that even after
primary immunization, we could obtain significantly higher anti-OVA IgG and IgG2a response
over OVA mixed D-ODN group. After booster injection, 22 fold more IgG, 26 fold more IgG1
and 13 fold more IgG2a were obtained compared to free group. Our findings demonstrated that
when simultaneous delivery of adjuvant (D-ODN) and antigen (OVA) within a proper depot
system is given to a host, very potent antigen specific immunity is achieved. This knowledge will
pave the way to design of novel effective vaccine adjuvants.Erikçi, ErdemM.S