Larson Pneumonia Vaccines

What kind of bacteria is Streptococcus pneumoniae?

Gram-positive facultative anaerobic

What is a distinguishing feature of gram positive bacteria?

Thick layer of peptidoglycans

What is the basis for pathogenicity of Streptococcus pneumoniae?

Surface complex polysaccharides (capsular polysaccharides) (CPS)

What does the bacterial capsule do in Streptococcus pneumoniae?

Aids in immune evasion

• capsule prevents binding of IgG to membrane antigens

What two ways can Streptococcus pneumoniae spread?

• Through respiratory droplets person-to-person

• Autoinoculation in a person carrying S. pneumoniae in their upper respiratory tract

What do capsular polysaccharides (CPS) do in the pathogenesis of Streptococcus pneumoniae?

Allow S. pneumoniae to avoid entrapment by:

• mucus

• opsonophagocytosis

• detection by host receptors

Streptococcus pneumoniae produces a biofilm, which can _____

Hinder drug penetration and contribute to drug resistance

How does Streptococcus pneumoniae enter the bloodstream?

Through epithelial polymeric immunoglobulin receptor (used to translocate antibodies) or, in severe cases, lung injury and severe epithelial damage

What is the primary mechanism for clearance of Streptococcus pneumoniae?

Phagocytosis

What is the goal of vaccine-elicited immunity against Streptococcus pneumoniae?

To elicit long-lasting, high affinity, protective antibodies

What two processes are important for vaccine-elicited immunity against Streptococcus pneumoniae?

• Opsonization

• Complement

  • → IgG binding to surface polysaccharides → lysis

What is the purpose of incorporating a bacterial toxin into vaccines?

• They are actually toxoids

  • Non pathogenic

  • Protein antigens derived from known pathogens

• The purpose is to induce a stronger immune memory response

B cell immune memory requires _____

Antigen-specific T cell help

What type of vaccine is the pneumococcal vaccine?

Polysaccharide/protein-polysaccharide conjugate vaccine

What is the result of a pneumococcal vaccine where the polysaccharide is not conjugated with a carrier protein?

• No production of memory B cells

• Short-lived antibody production

• No affinity maturation

• No immune response in infants <2 years old

What is the result of a pneumococcal vaccine where the polysaccharide is conjugated with a carrier protein?

• Affinity maturation

• Induction of memory B cells

• Long-lived antibody production

• Improved immune responses in infants

How does affinity maturation refine the antibody response?

• Selection of B cells that produce antibodies with higher affinity to antigen (interaction through the variable region)

• Somatic hypermutation - random mutations in the antibody variable region genes

Affinity maturation requires _____

Antigen-specific T cell help

What does neglected valency mean in the context of protein-polysaccharide conjugate vaccines?

• Carrier protein itself elicits an immune response

• Can create antibodies and immune memory against the carrier protein

What is the purpose of repeated immunization?

To enhance the duration and quality of the memory response

• Memory B cells can re-renter the germinal center to undergo additional somatic hypermutation and affinity maturation

• Clonal selection of B cells with high affinity receptors

• Expansion of B cell memory pool