Table 3.

The wt rAB chimeric virus has awt-like phenotype in chimpanzees and can be attenuated by inclusion of mutations derived from RSV subgroup A vaccine candidates

VirusaNo. of animalsDoseb (log10PFU per site)Mean peak virus titer (log10PFU/ml)Rhinorrhea scorebMean serum neutralizing antibody titerc (reciprocal log2)
Nasopharyngeal swabTracheal lavagePeakMeanDay 0Day 28
wt RSV B14d 4.02.98 ± 0.261.37 ± 0.673.02.5<3.312.8
wt RSV B12d 5.02.75 ± 0.252.45 ± 1.452.01.5<3.313.0
rAB45.04.28 ± 0.124.05 ± 0.173.02.5<3.312.3
rABcp248/404/103035.02.03 ± 0.19<0.7 ± 0.000.00.0<3.310.5
  • a Chimpanzees were inoculated by the intranasal and intratracheal routes with the indicated amount of virus in a 1-ml inoculum per site. Nasopharyngeal-swab samples were collected daily for 12 days, and tracheal-lavage samples were collected on days 2, 5, 6, 8, and 12.

  • b The amount of rhinorrhea was estimated daily and assigned a score (0 to 4) that indicated extent and severity: 0, none; 1, trace; 2, mild; 3, moderate; 4, severe.

  • c Serum RSV-neutralizing antibody titers were determined by a complement-enhanced 60% plaque reduction assay withwt RSV B1 and HEp-2 cell monolayer cultures incubated at 37°C (4). RSV-seronegative chimpanzee serum used as a negative control had a neutralizing antibody titer of <3.3 log2. Seropositive adult human serum used as a positive control had a neutralizing antibody titer of 11.0 log2.

  • d Historic control animals from Crowe et al. (12).