Special Series: Practical Diagnosis and Management of ImmunodeficiencyAssessment and clinical interpretation of polysaccharide antibody responses
Section snippets
PNEUMOCOCCAL VACCINE RESPONSE
Immunization with a polysaccharide pneumococcal vaccine (eg, Pneumovax 23; Merck, Whitehouse Station, New Jersey; or Pnu-Immune 23; Lederle Laboratories, Madison, New Jersey) is used to evaluate response to polysaccharide antigens in children older than 2 years. Since 2000, use of a conjugate vaccine (eg, Prevnar; Wyeth Labs, Madison) has been standard of care in the United States, and thus, most children born after 2000 have been immunized with up to 4 doses of the conjugate vaccine. Those
ALTERNATIVE MEASURES OF POLYSACCHARIDE RESPONSE:
Isohemagglutinins are antibodies generated in response to polysaccharides of gut flora that cross-react with A or B blood group erythrocyte antigens.3 However, this has limited utility because most laboratories measure combined titers of IgG and IgM for isohemagglutinins. Although not routinely used in the United States, a polysaccharide vaccine for meningococcus is also available and has been used to measure the polysaccharide response. However, the interpretation of the response to this
VARIABLES THAT AFFECT MEASUREMENT AND INTERPRETATION OF PNEUMOCOCCAL ANTIBODY TITERS
Laboratory standardization rules developed for anti-pneumococcal polysaccharide antibody evaluation include absorption of patient serum samples with polysaccharide C and serotype 22F. We recommend measurement of antibody titers to 12 to 14 different serotypes, ideally including at least 7 serotypes present only in the 23-valent polysaccharide vaccine (Prevnar contains serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F) (Table 1). Panels of titers that conform to this recommendation are available
INTERPRETING RESPONSES
Unfortunately, no published data are available in healthy individuals that permit a solid definition of normal and abnormal pneumococcal antibody responses in different age groups. Normal responses are highly dependent on patient age and have not been fully defined.7 Responses vary considerably among individuals and among serotypes in the same individual. Broader differences in response may also exist with regard to patient ethnicity. We interpret responses to the polysaccharide pneumococcal
SUBSEQUENT VACCINATIONS AS PART OF EVALUATION OF RESPONSE
Patients with initial poor response to the pneumococcal polysaccharide vaccine may clinically benefit from immunization with the conjugate vaccine.4 These vaccines were developed because healthy children younger than 2 years demonstrate poor responses to polysaccharide antigens alone. However, conjugation helps direct the response toward the immunogenic protein complexed to the polysaccharide antigen, thereby stimulating protective immune responses in those individuals. Therefore, the response
CHARACTERIZATION OF ABNORMAL RESPONSES
Patients with normal immunoglobulin levels may have varying degrees of responsiveness to the polysaccharide vaccine (R.U.S., unpublished data, 1995 to present).10 Patients with the most severe form of unresponsiveness fail to respond to any serotype. Some of these patients may respond to 1 serotype only. In both cases, if additional immunization with the conjugate vaccine fails to bring a clinical benefit, IgG replacement should be considered. Such consideration should include polysaccharide
CONCLUSION
Clinical disease staging and treatment of patients referred for recurrent infections need to be considered within the context of the types of infections that affect the patient, the results of initial immunologic screening tests, and the patient's ability to produce specific antibodies. The varied approach to treatment of these complex patients is beyond the scope of this review. A brief discussion of IgG replacement and treatment strategies is found in the article by Agarwal and
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Cited by (0)
Authors have nothing to disclose.