Pneumococcal antigens

Pneumococcal antigens are diverse molecular components of the bacterium *Streptococcus pneumoniae* that are recognized by the host immune system. These include capsular polysaccharides, which are the basis for serotype classification and a major virulence factor, and various proteins such as Pneumococcal surface protein A (PspA), Pneumococcal surface adhesin A (PsaA), and Pneumolysin, which contribute to bacterial adherence, invasion, and immune evasion. While not direct therapeutic targets in the conventional sense of host receptors or enzymes, these antigens are crucial for the bacterium's pathogenicity, causing diseases like pneumonia, meningitis, and sepsis. They are extensively utilized in pneumococcal vaccines (polysaccharide and conjugate types) to induce protective antibody responses, thereby preventing infection. The development of new vaccines and monoclonal antibody therapies targeting these antigens aims to overcome challenges like serotype replacement and antibiotic resistance.

Other names

Streptococcus pneumoniae antigensPneumococcus antigens

For vaccines, the mechanism involves stimulating active immunity by inducing the production of antibodies against specific pneumococcal antigens. Polysaccharide vaccines primarily induce T-cell independent antibody responses, while conjugate vaccines elicit T-cell dependent responses, leading to more robust and longer-lasting immunity. These antibodies then act by opsonizing bacteria, activating complement pathways, inducing bacterial agglutination, causing capsule shedding, and neutralizing bacterial toxins. Monoclonal antibodies targeting pneumococcal antigens function through similar mechanisms, including opsonization, complement activation, and toxin neutralization, to clear the infection and reduce bacterial adherence.