Fig. 4.

Neutralizing antibodies in rabbit tear samples. Tear samples from rabbits immunized with Cervarix (N = 5) and vector control (N = 5) were tested for neutralizing (a) HPV-16 and (b) HPV-18 pseudoviruses in 293TT cell culture as described previously. Tear samples were pre-incubated with pseudovirions (1 : 50) for 1 h at 37 °C prior to infecting triplicate wells of 293TT cells seeded the previous day in 96-well plates at 3×10⁴ cells per well. At 3–4 days post-infection, spent media were analysed for secreted alkaline phosphatase (SEAP) levels by using a colorimetric assay. A significant difference was found between Cervarix-immunized rabbits and the control group (P<0.01) in neutralization against HPV-16 and -18. A significant difference was also found between the control group and the positive control group, indicating that tears contain non-specific neutralizing antibodies as the first defence against viral infection. Values are given as mean±se.