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Published on: April 22, 2010
Pre-clinical evaluation of a 15-valent pneumococcal conjugate vaccine (PCV15-CRM197) in an infant-rhesus monkey
Julie M Skinner1, Lani Indrawati, Jayme Cannon
1Department of Vaccines Research, Merck & Co., Inc., West Point, PA 19486, USA.
Insights
A new 15-valent pneumococcal conjugate vaccine (PCV-15) shows comparable immunogenicity to the 7-valent Prevnar vaccine for common serotypes. PCV-15 demonstrated significantly higher antibody responses for its 8 additional serotypes in infant rhesus monkeys.
Area of Science:
- * Immunology
- * Vaccinology
- * Microbiology
Background:
- * Invasive pneumococcal disease (IPD) incidence varies due to epidemiology and vaccination, with increasing non-vaccine serotypes observed after 7-valent pneumococcal conjugate vaccine (PCV) use.
- * Higher valency vaccines are needed to broaden serotype coverage against Streptococcus pneumoniae (PN).
Purpose of the Study:
- * To evaluate the immunogenicity of a novel 15-valent pneumococcal conjugate vaccine (PCV-15) in infant rhesus monkeys.
- * To compare PCV-15's immune response to the existing 7-valent vaccine (Prevnar®) for common and additional serotypes.
Main Methods:
- * Infant rhesus monkeys (2-3 months old) received three doses of PCV-15 or Prevnar® at 2-month intervals.
- * Serotype-specific IgG antibody levels were quantified using a multiarray electrochemiluminescence (ECL) assay.
Main Results:
- * PCV-15 elicited comparable antibody responses to Prevnar® for the 7 shared serotypes.
- * Antibody responses to PCV-15 were over 10-fold higher than baseline for the 8 additional serotypes not included in Prevnar®.
Conclusions:
- * PCV-15 demonstrates promising immunogenicity in a preclinical model, offering broader serotype coverage.
- * The vaccine is a potential candidate for addressing the rise of non-vaccine serotype IPD and improving global public health outcomes.
Abstract:
The incidence of invasive pneumococcal disease (IPD), caused by the approximately 91 serotypes of Streptococcus pneumoniae (PN), varies geographically and temporally as a result of changing epidemiology and vaccination patterns as well as due to regional measurement differences. Prevnar(®) (Pfizer), the first licensed pneumococcal conjugate vaccine (PCV), comprises polysaccharides (PS) from 7 serotypes conjugated to the mutant diphtheria toxin carrier protein, CRM197. In the United States and elsewhere, this vaccine has been highly efficacious in reducing the incidence of IPD caused by vaccine serotypes, however, the incidence of non-vaccine serotypes (e.g., 19A, 22F, and 33F) has increased, resulting in the need for vaccines with higher valencies. In response, 10- and 13-valent PCVs have recently been licensed. To further increase serotype coverage, we have developed a 15-valent PCV containing PS from serotypes 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F and 33F conjugated to CRM197 and formulated on aluminum phosphate adjuvant. Vaccine immunogenicity was evaluated in infant rhesus monkeys since they, like human infants, respond poorly to unconjugated PN PS. Infant (2-3 month old) rhesus monkeys were vaccinated three times with PCV-15 or Prevnar(®) at 2 month intervals, and serotype-specific IgG antibodies were measured using a multiarray electrochemiluminescence (ECL) assay. The results indicate that antibody responses to PCV-15 and Prevnar(®) were comparable for the 7 common serotypes and that post-vaccination responses to PCV-15 were >10-fold higher than baseline for the 8 additional serotypes.
