FIG. 4.

Specific IgG responses in sera obtained after immunization of mice with OpaJ-containing liposomes using different adjuvants. (A) Western blots containing whole-cell lysates of OpaJ⁺ cells of N. meningitidis strain H44/76 with immunotype L3 probed with pooled sera of mice immunized with nonadjuvanted liposomes (lane 1) or liposomes adjuvanted with LpxL1 LPS coincorporated into the liposomes (lane 2), free LpxL1 LPS (lane 3), 1 μg of PagL LPS coincorporated into the liposomes (lane 4), 1 μg of free PagL LPS (lane 5), or nonimmune serum (lane 6). Lane 7 shows the reactivity of the sera of the mice immunized with proteoliposomes and 1 μg of free PagL LPS with a whole-cell lysate of Opa⁻ cells. Prior to SDS-PAGE, the bacterial suspensions were heated in sample buffer with 2% SDS at 100°C. The positions of molecular size markers are indicated at the left. (B) Quantitative total IgG titers against purified L8 LPS measured in ELISAs. Sera from mice immunized with LpxL1 LPS-adjuvanted liposomes and from the control groups were tested against purified LpxL1 L8 LPS, and those from mice immunized with PagL LPS-adjuvanted liposomes were tested against purified PagL L8 LPS. The data show the geometric mean (horizontal line), individual serum titers, and number of responder mice/group. Statistically significant differences between serum groups are marked with one asterisk (P < 0.05). Similar results were obtained when the sera tested here against purified LpxL1 L8 LPS were tested against PagL LPS and vice versa (data not shown). No reactivity was detected with L3 LPS. Note that only LPS of immunotype L8 was used for the immunizations.