Assessment of HTLV-1 infection in rabbits. (A) Antibody response against HTLV-1 from each rabbit was measured by anti–HTLV-1 ELISA assay, using both HTLV-1 Gag and envelope proteins as antigens. Each dot represents the absorbance value of a single inoculated rabbit at 0, 2, 4, 6, and 8 weeks after inoculation within each group. Inoculum as indicated at bottom includes 729.HTLV-1 (n = 5), 729.HTLV-1ΔHBZ (n = 6), 729.HTLV-1HBZΔLZ (n = 6), or 729/media (n = 2). The horizontal line represents the average of the rabbit group at each weekly time point and the dotted line represents 3 times the standard deviation of uninfected control values. (B) The HTLV-1 genome fragment containing the HBZ coding region was amplified by PCR from DNA of PBMCs from a representative of at least 1 rabbit of each group (week 8 after inoculation). The expected HBZ mutations in rabbit PBMCs were confirmed using the diagnostic restriction enzyme NheI for HTLV-1HBZΔLZ and further confirmed by nucleotide sequencing (data not shown).