ATCC offers 23 types of purified pneumococcal polysaccharides, which are components of the 23-valent pneumococcal polysaccharide vaccine against Streptococcus pneumoniae. The antigens are prepared by Merck & Co. and are repackaged by ATCC for distribution as research reagents.

The Pneumococcal Vaccine
A pneumococcal vaccine was licensed for use in the United States in 1977 consisting of purified capsular antigen from 14 types of Streptococcus pneumoniae (1, 2, 3, 4, 6, 8, 9, 12, 14, 19, 23, 25, 51, 56). The 14 types represented in the vaccine were responsible for 68% of bacteremic pneumococcal disease in the United States. Immunologically related serotypes caused an additional 17% of the pneumococcal diseases, but cross-protection occurred; thus, the immunologically related serotypes were not Included in the vaccine.

In 1983 a new pneumococcal vaccine was licensed composed of 23 serotypes including all but two (6 and 25) of the original 14 types, and eleven new types (5, 17, 20, 22, 26, 34, 43, 54, 57, 68, 70). These 23 bacterial types are responsible for 87% of bacteremic pneumococcal disease in the United States. Once again cross-protection will occur; for example, cross-protection between types 6 and 26 led to the removal of type 6 from the vaccine.

When preparing these polyvalent vaccines, the pneumococcal polysaccharides are extracted and purified separately and then combined in a final product. Each dose of the original 14-valent vaccine contained 50 µg of each polysaccharide for a total of 700 µg of antigen. In the 23-valent vaccine, the amount of each antigen has been reduced to 25 µg for a total of 575 µg of antigen. Studies indicate comparable levels of immunogenicity between the two vaccines despite the reduction in total antigen content.

Use of the Antigens in Immunologic Studies
Since each of the polysaccharide antigens used in the polyvalent vaccine is extracted and purified separately, these vaccine products are useful in research. Although more than 80 serologically distinct types of pneumococcal polysaccharide antigens are recognized, only 24 types are available as purified vaccine products. The antigens have two designations. In the United States designation, the antigens are numbered chronologically in the order of their recognition, regardless of any cross-reactivity. The Danish designation uses a number-letter combination to indicate that cross-reactivity can occur. The number refers to the serogroup, and the letters indicate related serotypes that cannot always be distinguished.

In addition to their use in assaying for type-specific antibody, these antigens are useful in the analysis of other immune responses and immunodeficiency studies. These soluble antigens have been used to detect low levels of immunoglobulin (IgM) specific to the polysaccharide in neonatal and splenectomized adult mice, demonstrating that the spleen plays a major role in the immune response. Use of the pneumococcal vaccine in immunocompromised humans provided a comparable study of the human immune response. The immune response to polysaccharides has been used to study the role of T and B cells of immunosuppression caused by malignancies. Type 3 pneumococcal polysaccharide provides an excellent model system for investigating the initiation and control of antibody responses. In the absence of an adjuvant, type 3 pneumococcal polysaccharide elicits an antibody response restricted to one immunoglobulin class.

References:

Baker, P.J., et al. Regulation of the antibody response to pneumococcal polysaccharide by thymus-derived cells. Rev. Infect. Dis. 3: 332-341, 1981.

Havas, H.F., and G. Schiffman. The effect of an IgM plasmacytoma (TEPC-183) on the primary immune response of BALB/c mice. Immunology 34: 1-8, 1978.

Robbins, J.B., et al. Consideration for formulating the second generation pneumococcal capsular polysaccharide vaccine with emphasis on the cross-reactive types within groups. J. Infect. Dis. 148: 1136-1158, 1983.

Schiffman, G. Immune responses to pneumococcal polysaccharide antigens: a comparison of the murine model and the response in humans. Rev. Infect. Dis. 3: 224-232, 1981.

Vogel, S., and B. Roberson. Phytohemagglutinin stimulation of enhanced immunoglobulin G production in mice inoculated with Type III pneumococcal polysaccharide. Infect. Immun. 3: 901-907, 1978.