Immunoglobulin prophylaxis against human T cell lymphotropic virus type II in rabbits

Hyperimmune globulins, I-IgG and II-IgG, prepared from healthy persons seropositive for human T cell lymphotropic virus (HTLV) types I and II, respectively, were tested for their prophylactic effect against HTLV-II infection in rabbits. Three groups (A, B, and C) of 3 female rabbits each were used. Group A rabbits were inoculated intravenously with HTLV-II-carrying rabbit lymphoid cell line RII. Group B and C rabbits were immunized, respectively, with II-IgG and I-IgG and challenged with RII cells 24 h later. All group A and C rabbits seroconverted for HTLV-II after 2 weeks, but all group B rabbits were protected from HTLV-II infection. Gene amplification by polymerase chain reaction revealed the presence of HTLV-II provirus sequences in all group A and C rabbits but in none of the group B rabbits. These findings indicate that passive immunization with II-IgG is effective in preventing HTLV-II infection and that there is no cross-neutralization between HTLV-I and -II.