TABLE 4.

Viremia and neutralizing antibody levels in TV-2-immunized monkeys following challenge

Immunizing virus (day 0)Challenge virusa (day 42)% of monkeys with viremia after challengeMean peak virus titer (log10 PFU/ ml of serum)Immunization (day 28) and postchallenge (day 70) geometric mean serum neutralizing antibody titer (reciprocal dilution)b against:
DEN1DEN2DEN3DEN4
Day 28Day 70Day 28Day 70Day 28Day 70Day 28Day 70
TV-2DEN10<1.055352c121525101e133167
None (mock infection)DEN11002.1 ± 0.3<10324d<1016<1027<1024
TV-2DEN2752.0 ± 0.5516516304d1592e93160
None (mock infection)DEN21001.9 ± 0.4<1022<10477d<1048<1049
TV-2DEN30<1.06250192815252d142247
None (mock infection)DEN31002.4 ± 0.4<1029<1010<10244d<1028
TV-2DEN40<1.063272199c1628142286
None (mock infection)DEN41002.6 ± 0.4<1011<1029<1019<10311d
  • a Sixteen rhesus monkeys previously inoculated with TV-2 (Table 2) were divided into four groups of four monkeys, and two mock-immunized monkeys were tested per group. Monkeys were challenged on day 42, and serum was collected on days 0 to 6 postchallenge and analyzed by plaque assay in Vero cells. For neutralization assay, postchallenge serum was collected on day 70 (28 days following virus challenge).

  • b Plaque reduction (60%) neutralizing antibody titers were determined using the challenge strains in footnote d of Table 3.

  • c Seventy-five percent of rhesus monkeys had a four-fold or greater increase in antibody titer after challenge.

  • d One hundred percent of rhesus monkeys had a four-fold or greater increase in antibody titer after challenge.

  • e Fifty percent of rhesus monkeys had a four-fold or greater increase in antibody titer after challenge.