In a subunit vaccine, the subunit must come from the outer surface of the pathogen.
The correct answer and explanation is :
Correct Answer:
False
Explanation:
In a subunit vaccine, it is not necessary for the subunit to come specifically from the outer surface of the pathogen, although many often do for practical reasons. A subunit vaccine works by using only parts of the pathogen — the “subunits” — to stimulate an immune response. These subunits can include proteins, polysaccharides (sugars), or peptides, and they can be derived from any part of the pathogen that is recognizable and important for the immune system to target.
However, it is true that many subunit vaccines use surface proteins or antigens because these are the parts of a pathogen that are most easily recognized by the immune system. For example, the spike protein of the SARS-CoV-2 virus (the virus that causes COVID-19) is an outer surface protein that is commonly used in subunit vaccines. Surface proteins are often selected because they are accessible to antibodies circulating in the body — meaning that if the immune system has already learned to recognize these proteins, it can more effectively neutralize the pathogen before it invades cells.
But subunits used in vaccines are not restricted to surface components. If a protein or polysaccharide from inside the pathogen can provoke a strong and protective immune response, it may be used in the vaccine as well. For instance, internal proteins can sometimes be very conserved (not likely to mutate) and can provide broader protection across different strains of a pathogen.
Examples of subunit vaccines include:
- Hepatitis B vaccine — uses the hepatitis B surface antigen (a surface protein).
- Human papillomavirus (HPV) vaccine — uses the L1 protein, forming virus-like particles.
- Pertussis (whooping cough) component of DTaP vaccine — uses purified proteins from the bacteria.
In summary, while surface subunits are often preferred, they are not a strict requirement for a subunit vaccine. The key is that the selected subunit must trigger a strong and protective immune response.