Advantages over passive immunity

• Sustained response
• Vaccine contains more than single determinant of target antigen
• More than single epitope in a particular antigen can be identified by active immunity.
• Vaccines activate both B and T lymphocytes

Components of therapeutic cancer vaccine

• Antigenic material derived from the tumor- Usually it is over-expressed in tumor cells and is essential for tumor cell survival.
• Carrier- Necessary to deliver tumor antigen to antigen presenting cell (Dendritic cell). Example: Liposomes, Mannose etc.
• Adjuvant- Facilitates an enhanced immune response against the tumor antigen. Ex: Alum.

Impediments in vaccine therapy

• Problems with trafficking of anti-tumor T cells to tumor site
• Impaired function of antitumor T cells due to immunosuppressive mechanisms developed by tumor in its microenvironment.

Antisense oligonucleotides:

• Expression of oncogene initiates the process of genesis of malignancy
• Suppression of this expression can result in suppression of tumor growth
• mRNA expression can be suppressed using antisense oligonucleotides.
• They are short pieces of single stranded DNA or RNA (about 17-20 base pairs) which bind to translation initiation site of mRNA (as they contain complementary sequence)
• They are being tried even in some benign diseases such as sickle cell anemia.
• Example: Antisense nucleotides targeting BCL2 decrease the expression of BCL2. Hence cell becomes susceptible to apoptosis. Ex: Oblimerson in treatment of CLL.