90. RTS,S vaccine for malaria consists of the central repeat (R) region derived from Plasmodium
falciparum circumsporozoite protein (CSP) that is genetically fused to the T-cell epitope (T) and
surface antigen (S) regions derived from:
A. Vaccinia virus
B. Hepatitis B virus
C. Adenovirus
D. Influenza virus

Detailed Explanation:

The RTS,S malaria vaccine is the first approved vaccine for malaria and has been developed to target Plasmodium falciparum, the most lethal species of the malaria parasite. The design of the vaccine aims to prime the immune system against the parasite before it enters liver cells, where it multiplies.

Components of the RTS,S Vaccine:

1. R: Central repeat region of the Plasmodium falciparum circumsporozoite protein (CSP). This region is rich in NANP amino acid repeats, which are highly immunogenic.

2. T: T-cell epitope of CSP, which helps stimulate T-cell mediated immunity.

3. S: Hepatitis B surface antigen (HBsAg) – This is not just a carrier but plays a dual role:

   • Enhances immunogenicity by forming virus-like particles (VLPs).

   • Acts as an adjuvant to boost immune responses.

4. An excess of HBsAg (S protein) is co-expressed to promote the formation of stable and immunogenic VLPs.

The fusion of CSP with HBsAg (from Hepatitis B virus) enables the vaccine to elicit both humoral and cellular immune responses, thereby increasing its efficacy.

Correct Answer:

B. Hepatitis B virus