CEBR2-05
Optimization of Oral Delivery for DNA Based Vaccines
Researchers:
Mohsen Abdel-Moniem Bayomi
Fars K. Al-Anazi
Gamal El Maghraby
Alaa Al-Din Bakery Yassin
Ibrahim A. Alsarra
Mohamed O. Gad-El-Rab
Ibrahim M. El-Bagory
Abdullah Al-Omrani
ABSTRACT:
The use of DNA-based vaccines attracted much attention recently. In addition to their ability to elicit both humoral and cellular immune responses, they are very stable, safe and cost effective in manufacturing and storage. Intramuscular administration was initially considered as the primary route for DNA vaccine delivery. Because of the limited and variable potency after injection, there is always a need to improve the immunogenicity of the vaccines and/or to explore alternative delivery systems.
Oral immunization provides a promising alternative. This route can allow for massive immunization without the need for specially trained personnel to deliver the vaccine and does not require the strict sterility of parenteral products. Orally administered DNA vaccine is taken up by the M-cells which are the entrance port to the Peyer`s patches where antigen presentation can take place. This will stimulate B- and T-cells and thus, stimulate mucosal immune response before leaving the Peyer`s patches through the thoracic duct and reaching the systemic circulation. Oral vaccination can thus provide both mucosal and systemic immunization providing double protection. However, the development of effective oral DNA vaccine is hindered by many complications such as gastrointestinal degradation and poor uptake by the Peyer`s patches.
DNA vaccine plasmid gWIZ/HBs HBs in which expression of the HBs antigen is driven by a strong CMV modified promoter will be used. An incremental innovative approach to optimize the HBs cDNA expression delivered to the target cells will also be developed. This approach consists in genetically engineering the plamid to tune the HBs cDNA sequence to the human codon-usage preference.
Collioidal delivery systems such as liposomes, niosomes, nanosuspensions and nanoemulsions will be formulated, optimized and evaluated for oral delivery of hepatitis B vaccine as a model DNA vaccine. In addition, PLG, chitosan, alginate, lecithin and other biodegradable polymers based particles will be tested for oral delivery.
The oral systems will be designed to reach the terminal ileum where they can be taken up by the Peyer`s patches. The carrier systems will be characterized for the adsorption and/or entrapment efficiency before evaluating the immunogenicity in high responder strain experimental animals.
The animals will receive the naked DNA in intramuscular administration in addition to oral and intramuscular administration of the corresponding formulation in initial and booster doses as scheduled. The humoral and cellular responses will be measured from blood and pripheral mononuclear cells. Antibodies will be also measured in serum samples to assess humoral responses and T-cell proliferation.
In addition, synthesis of cytokines will be used to assess cellular responces. The optimized formulations are also planned to be subjected to evaluation on human volunteers.By the end of these studies we could have optimized system(s) for oral delivery of DNA vaccine.
OBJECTIVES:
The objective of this proposed research is to develop and deliver DNA vaccines via a route of administration other than injection.
Oral delivery system is chosen for this proposed research aiming to improve patient compliances and increase immunogenicity. Hepatitis B vaccine was chosen in the proposed research as a model DNA vaccine. Genetic engineering of an existing Hepatitis B DNA vaccine plasmid will be one of the aims of this work to optimize the antigen expression in the target cells by tuning the HBs cDNA sequence the human codon-usage preference. Different carrier systems including liposomes, niosomes, microemulsions, micro and nano suspensions will be formulated for the delivery of DNA vaccine.
The different formulations will be characterized, optimized and compared in vitro. The most promising formulations with high stability and good physical characteristics will be subjected to in vivo study in small and higher animals.
The efficacy and safety of the different vaccine formulations will be assessed by measuring the antibody and cellular responces post-immunization.
Based on these immunological studies the successful formulation that will show high immunogenicity are planned to be evaluated in human volunteers aiming to produce market formulations for oral delivery of hepatitis B vaccine.