Question

Which of the following neisserial virulence factors is part of the tetravalent vaccine that protects against some but not all serogroups of Neisseria meningitidis? A. Lipooligosaccharide B. Capsule C.Porin D. Pilin E. Opacity proteins

Short answer

B. Capsule

Step-by-step solution

Identify the correct virulence factor

The virulence factors mentioned in the options are all associated with Neisseria meningitides, a bacterium that can cause meningitis. However, not all of these factors are part of the tetravalent vaccine used to protect against some serogroups of this bacterium. Based on knowledge about vaccines and their components, one would know that capsule polysaccharides are often used in vaccines, because they can elicit an immune response. So the correct option is B. Capsule.

Key concepts

Virulence Factors

Virulence factors are the weaponry that bacteria like Neisseria meningitidis use to invade and cause harm in their hosts. These factors help the bacteria to evade the immune system, attach to host cells, and establish infection. For instance, the lipooligosaccharides (LOS) can trigger a huge immune response that turns harmful for the host, and opacity proteins contribute to immune system evasion by altering the surface of the bacteria.

Understanding these factors is crucial for developing effective vaccines because identifying components that can provoke a strong immune response is the key to long-lasting immunity. However, a delicate balance is necessary; the vaccine must not provoke too harsh of a reaction, which could be damaging.

In the case of the Neisseria meningitidis vaccine, researchers have honed in on particular virulence factors that can be targeted to provide immunity without causing unnecessary harm to the body.

Tetravalent Vaccine

A tetravalent vaccine is designed to protect against four different strains or serogroups of a pathogen. In the context of Neisseria meningitidis, these serogroups are A, C, Y, and W-135. This broad coverage is necessary because the bacteria exist in multiple serogroups, which are distinguished by their different capsule polysaccharides structures.

The goal of the tetravalent vaccine is to induce immunity against these four major serogroups, reducing the chances of infection and the spread of the disease. By targeting multiple serogroups, public health initiatives can more effectively control outbreaks of meningitis, as it is less likely that non-covered serogroups will dominate.

Vaccines like these are pivotal, especially in areas known as the meningitis belt in Sub-Saharan Africa, where Neisseria meningitidis infections are particularly prevalent.

Capsule Polysaccharides

Capsule polysaccharides are a major part of the protective mechanism of many bacteria, including Neisseria meningitidis. The capsule is a layer of complex sugars that surrounds the bacterial cell and helps it to escape detection and destruction by the host's immune system.

The real breakthrough in vaccine development came with the discovery that these capsule polysaccharides can be used to create a protective immune response without causing the disease itself. When used in vaccines, the immune system learns to recognize the unique signatures of these polysaccharides, creating antibodies that are primed to fight off the actual bacteria if the individual was to encounter it later on.

However, since the vaccine includes only serogroups A, C, W-135, and Y, it does not provide the protection against other serogroups like B or X which also have distinct polysaccharide capsules. For comprehensive immunity against serogroup B, a different vaccine formulation is needed.