TABLE 2.

Geometric mean OI for rabbits immunized IM with PCV13, Gamma-PN, or Gamma-PN+Al^a

^aIndividual immune sera (n = 3–6 rabbits per vaccine group) were tested by the opsonophagocytic killing assay (OPKA) with differentiated HL-60 cells against PCV13-included (underlined) and nonincluded Spn serotypes. The Opsotiter3 program was used to calculate opsonic index (OI) values for individual serum samples, and the geometric mean OI (GMOI) for each vaccine group is presented here. Data show the GMOI pooled from two independent experimental repeats. Prebleed sera pooled from all rabbits was used as a baseline control for nonspecific killing. A value of “<4” indicates no killing activity was detected in the OPKA even with neat sera (final dilution of 1/4 when mixed with other assay components). Table cells are colored based on a gradient from the highest (dark blue) to lowest (light blue) GMOI measured for each individual serotype.

^bCross-reactivity of PCV13 against the nonincluded serotypes 6C and 23A has been reported in the literature.