What are cancer vaccines?
Vaccines that treat the existing cancer or prevent the development of cancer are called cancer vaccines. Vaccines can be produced against those cancers that are caused as a result of onco-viruses such as Hepatitis B virus and Human papilloma virus (hpv).
Types of cancer vaccine
There are three types of cancer vaccines:
Cell-based vaccines:
Tumor Antigens are added to the dendritic cell derived from the patient which results in the activation of T-cells.
Peptide-based vaccines:
Peptide-based vaccines usually consist of cancer specific-epitopes and often require an adjuvant to stimulate the immune system and enhance antigenicity.
Gene-based vaccines:
They are composed of DNA/RNA encoding for the gene and its expression in antigen presenting cells results in the formation of proteins used for vaccine production.
Vaccines that are approved by FDA against cancer:
HPV Vaccine: The vaccine protects against the Human papillomavirus. If this virus stays in the body for a longer period of time then it can cause certain type of cancers such as
vaginal cancer, cervical cancer, anal cancer, genital warts etc. The vaccine is named Gardasil and it is a protein-based vaccine. It provides protection against more than 3 types of hpv viruses. It is usually administered in 3 shots.
Hepatitis B vaccine. This vaccine protects against the hepatitis B virus (HBV). This virus is known to cause liver cancer.
Challenges in developing a cancer vaccine:
As viruses are entities that mutate constantly it's difficult to design a vaccine against it furthermore most of the cancer are caused as a result of tumors or some faulty mechanism shown by the gene. Hence vaccines should be produced from the antigens obtained from these tumors. The clinical trials have shown a high failure rate, the reasons are still unknown but the chances of failure could be:
Vaccines that are against a single tumor antigen: A multi tumor resistant vaccine will be more effective than a vaccine which is against a single tumor as it minimizes the chance of tumor mutating and becoming resistant to the therapy.
A patient who has undergone cancer treatment such as chemotherapy will be immunocompromised and this vaccine will not work in such people.
The time required for tumor progression also matters as shorter the time more likely that it will go undetected by the immune system.
More research needs to be conducted in this regard so as to develop vaccines for other types of cancers.
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