Immunization in Rituximab: Timing Matters
Significant differences were observed in the responses to PPV23 between the two groups, with only 57% of patients in the rituximab group demonstrating a twofold rise in titer in response to one or more serotypes, compared with 82% of the methotrexate-only patients, the authors reported. Similarly, only 47% of the rituximab patients had detectable anti-KLH IgG, compared with 93% of the methotrexate-only group, they noted.
“Because neoantigen and polysaccharide responses are B-cell dependent, decreased responses to KLH and [PPV23] are consistent with rituximab's mechanism of action,” the authors observed. “Despite peripheral B-cell depletion, however, responses to the KLH and [PPV23] vaccine were not completely abrogated in the present study,” they wrote, referring to the 47% of rituximab patients who had a quantifiable anti-KLH response and the 57% and 43% of rituximab patients who mounted responses to at least one and two pneumococcal serotypes, respectively. The authors concluded that for maximized vaccination response, “polysaccharide and primary immunizations should be administered prior to rituximab infusions.”
Although both of these studies provide some insight into the effects of rituximab therapy on immune function, “they fall short in offering clues about the causal mechanisms,” Dr. E. William St. Claire of Duke University Medical Center in Durham, N.C., wrote in an editorial (Arthritis Rheum. 2010;62:1–5).
Disclosures: The study reported by Dr. van Assen and colleagues was supported by Roche Nederland and Solvay Pharmaceuticals. The authors reported no additional conflicts of interest. The study reported by Dr. Bingham and colleagues was supported by Genentech Inc. The authors reported having financial relationships with Genentech, Roche, and Merck & Co. One of the authors served on Merck's data and safety monitoring board, and three of the authors own stock or stock options in Genentech. Dr. St. Clair disclosed having financial relationships with Biogen Idec Inc.
