Detection of deletions at the carboxy terminal region of the LMP-1 gene in PBMCs from HIV-seronegative donors (lanes 1 to 3) and HIV-infected patients (lanes 4 to 7 ). Cases 2 and 6 carried a full-length LMP-1 fragment of 283 bp. PBMCs from cases 1, 4, and 7 showed a smaller fragment consistent with a 30-bp deletion. Case 5 showed the concomitant amplification of a full-length and a deleted LMP-1 fragment, whereas case 3 carried a deletion larger than 30 bp. (N) DNA from an EBV-negative squamous cell carcinoma of the head and neck. (M) HaeIII-digested DNA of X-174-RF as a molecular-weight marker. Amplification of 100, 10, and 1 target molecule is also included to show the sensitivity of the seminested PCR protocol used.