Detection of CAV-2-ROP18 immunization on the antibody response. Serum samples were collected at weeks 0, 2, 4 and 6 post-primary immunization. (A) Determination of specific anti-ROP18 IgG antibodies in the sera of Kunming mice. (B) Determination of the specific anti-ROP18 IgG subclass profile in the sera of the immunized Kunming mice. Results are expressed as means of the OD490 value and standard deviation (n = 5), and statistically significant difference (P < 0.05) are indicated by an asterisk (*).