TABLE 2.

Titers of HCV-positive sera resulting in 50% inhibition of HCVpp entrya

Form of E250% Neutralization titer (difference [n-fold] from titer for wild type) of sera positive for HCV subtype:
1a (donor J)1a (donor I)1b2b3a4e5a
Wild type7.8E−05 (1.0)5.8E−05 (1.0)1.0E−03 (1.0)1.8E−04 (1.0)1.9E−02 (1.0)9.0E−03 (1.0)6.0E−05 (1.0)
T3853.0E−05 (2.6)2.7E−05 (2.2)4.7E−04 (2.1)2.6E−05 (6.9)3.2E−03 (6.0)1.0E−03 (9.0)7.3E−05 (0.8)
T3887.5E−05 (1.0)2.0E−05 (2.9)1.6E−03 (0.6)1.6E−04 (1.1)2.3E−02 (0.8)1.0E−03 (9.0)1.0E−05 (6.0)
N4175.5E−05 (1.4)1.0E−05 (5.8)3.0E−04 (3.3)1.4E−04 (1.2)2.1E−02 (0.9)1.0E−03 (9.0)1.0E−05 (6.0)
N4302.0E−04 (0.4)1.9E−04 (0.3)7.0E−03 (0.1)2.4E−04 (0.7)2.3E−02 (0.8)5.5E−03 (1.6)5.0E−05 (1.2)
N4761.1E−04 (0.7)5.7E−05 (1.0)1.0E−03 (1.0)2.6E−04 (0.7)2.3E−02 (0.8)2.5E−03 (3.6)1.3E−04 (0.5)
N5321.7E−05 (4.6)1.0E−05 (5.8)2.8E−04 (3.5)6.8E−05 (2.6)1.6E−02 (1.2)1.0E−03 (9.0)3.8E−05 (1.6)
N5401.1E−04 (0.7)5.5E−05 (1.0)1.5E−03 (0.7)2.0E−04 (0.9)2.3E−02 (0.8)1.3E−03 (6.8)4.9E−05 (1.2)
N5766.7E−05 (1.2)5.0E−05 (1.2)1.0E−03 (1.0)1.1E−04 (1.6)1.9E−02 (1.0)2.5E−03 (3.6)3.5E−05 (1.7)
N6455.5E−05 (1.4)4.8E−05 (1.2)1.0E−03 (1.0)3.3E−04 (0.5)2.3E−02 (0.8)1.0E−03 (9.0)5.5E−05 (1.1)
  • a Sera from individuals infected with the indicated HCV subtypes were tested by serial dilution for their abilities to inhibit the entry of HCVpp bearing wild-type and mutant E2 proteins of the H77 subtype 1a isolate. Mutant proteins are indicated by the relevant residue letter code followed by the position number in full-length E1-E2. To calculate the percentage of inhibition of entry, the following formula was used: (RLU with serum sample/RLU without serum sample) × 100. The 50% neutralization titers are the serum dilutions at which 50% inhibition of entry was achieved. The difference (n-fold) from the 50% neutralization titer for the wild type was calculated by using the following formula: (50% neutralization titer for wild-type E2)/(50% neutralization titer for indicated form of E2). All values are means of results from three independent experiments. The standard deviations were all within 20% of the mean 50% neutralization titer. All mean 50% neutralization titers deviating by more than 2 standard deviations from the mean 50% neutralization titer for the wild type were considered statistically significant.