Received on September 15, 2006
Accepted on December 28, 2006

Clinical Immunology

Laboratory Diagnosis of Specific Antibody Deficiency to Pneumococcal Capsular Polysaccharide Antigens

¹ Laboratory Medicine, Immunology, University Hospital Leuven, Belgium
² Department of Pediatrics, University Hospital Leuven, Belgium
³ Department of Internal Medicine, Allergy, University Hospital Leuven, Belgium

^* To whom correspondence should be addressed. E-mail: Xavier.bossuyt{at}uz.kuleuven.ac.be.

Background: Measurement of postimmunization antibody response to pneumococcal capsular polysaccharide (caps-PS) is the standard method to identify deficiency of antipolysaccharide antibody production. However, no standardized criteria have been defined for classification of patients into responders or nonresponders to caps-PS.

Methods: We vaccinated 37 healthy children and 39 healthy adults with Pneumovax^® and measured the anti-caps-PS antibody response to 5 serotypes. We also measured antipneumococcal antibody titers in 82 patients with increased susceptibility to airway infection. The assay was performed according to the 3rd-generation assay format.

Results: The lower 5th percentile (cutoff) concentrations for the postimmunization antibody titer in healthy individuals were 0.67 mg/L, 0.45 mg/L, 0.46 mg/L, 0.31 mg/L, and 1.04 mg/L for serotypes 3, 4, 9N, 18C, and 19F, respectively. In 96% of healthy individuals, antibody responses higher than the cutoff concentration were seen for at least 3 of the 5 serotypes. Nine of 82 patients (11%) failed to mount an adequate antibody response for at least 4 of the 5 serotypes tested, whereas only 1 control (1.3%) failed to do so.

Conclusion: The cutoffs for antibody responses to caps-PS identified in this study appear useful for identifying individuals with an inadequate response to vaccine.