Table 1.

Evaluation of the bactericidal titer and passive protection conferred by MAb Me-7 against serologically distinct meningococcal strains

Meningococcal strain (serological classification)Bactericidal titeraLevel of bacteremia (CFU ± SD/ml of blood)b 5 h after challenge in:% Reduction of bacteremia levels by MAb Me-7c
Rabbit serumHuman serumControl mice injected with MAb P2-4Mice injected with MAb Me-7
4B (B:15:P1.−:L3)30016018,890 ± 8,8724,688 ± 3,24175
27B (B:2b:P1.2,5)10,00060046,800 ± 51,4706,338 ± 7,49486
44B (B:4:P1.12)95012046,710 ± 16,930250 ± 37099
58B (B:−:P1.10:L2)54010078,840 ± 51,06010,160 ± 7,14987
164B (B:15:P1.7,1.6)9,0001,80075,500 ± 82,39012 ± 3599
180B (B:4:P1.2,5:L1/3)<104057,760 ± 32,15011,140 ± 8,89381
187B (B:14:P1.−)2,2501,80028,730 ± 18,12021 ± 4399
608B (B:2a:P1.2:L3)4,5001,50019,230 ± 12,020350 ± 55898
CHEO22 (B:15:P1.−)d 200100NDe NDND
MCH88 (A:4:P1.10)d <10<10176,400 ± 90,490164,500 ± 100,800NS 7
Z4734 (A:4:21:P1.16)2,5001,400NDNDND
Z4063 (A:4:P1.7)10,0002,000203,300 ± 98,5207,188 ± 6,45196
3C (C)2,500900NDNDND
41C (C:2b:P1.2,5)8,0003,00083,210 ± 65,57010,850 ± 8,06287
  • a The bactericidal titer of MAb Me-7 was determined to be the last dilution of antibodies which still reduced the numbers of CFU by at least 50% compared to the numbers of CFU in control wells containing an unrelated MAb and the appropriate amount of complement.

  • b The control mice were injected intraperitoneally 18 h before the meningococcal challenge with either 400 μl of ascitic fluid or 50 μg of purified MAb Me-7 or control MAb P2-4. The level of bacteremia induced by each meningococcal strain was calculated from at least two separate experiments as the arithmetic mean CFU per ml of blood ± the standard deviation. Each value represents a mean of data obtained from at least eight animals. The Mann-Whitney U test for nonparametric analysis was used to compare the numbers of CFU recorded in control mice to the values obtained for mice injected with MAb Me-7. P < 0.05 for all Me-7 values except for the one marked “NS” (not significant). The bacterial inocula were adjusted to approximately 1,000 CFU for strains 4B, 44B, 58B, and 187B; to 2,500 CFU for strains 27B, 164B, and Z4063; and to 5,000 CFU for strains 608B, 180B, 41C, and MCH88.

  • c The percentage of bacteremia was calculated relative to the control mice receiving MAb P2-4 as follows: [(mean CFU for control mice − mean CFU for Me-7-injected mice)/mean CFU for control mice] × 100.

  • d The concentration of serum used in the in vitro bactericidal assay was reduced to 10%.

  • e ND, not done.