Dual infection of rabbits with human T cell lymphotropic virus types I and II

Attempts were made to generate a rabbit model of dual infection with human T lymphotropic virus (HTLV) types I and II. Four groups (A, B, C, and D) of three rabbits each were used. Group A was inoculated with the RW-1 cell line coinfected with HTLV-I and HTLV-II and group B was transfused from a dually infected rabbit. Polymerase chain reaction (PCR) using primers specific for the pol region of each virus detected both HTLV-I and HTLV-II in all group A and two group B rabbits, but HTLV-II only in the remaining group B rabbit. Groups C and D already infected with HTLV-I and HTLV-II, respectively, were inoculated with an HTLV-II- or HTLV-I-producing cell line. One group C rabbit became PCR-positive for both viruses but the other five resisted superinfection with the respective viruses. During prolonged observation, three of the six dually infected rabbits converted to single (HTLV-I or HTLV-II) infection. The in vivo dual infection was confirmed by in vitro establishment of a lymphoid cell line coinfected with HTLV-I and HTLV-II. It was also possible to establish coinfected lymphoid cell lines from HTLV-I-infected rabbits by coculture with lethally irradiated HTLV-II-producing cells and vice versa. The mechanism of viral elimination in dually infected rabbits, as well as that of protective immunity against superinfection, remains to be elucidated.