LOCALIZATION OF HUMAN-IMMUNODEFICIENCY-VIRUS-1 RNA IN THYMIC TISSUES FROM ASYMPTOMATIC DRUG-ADDICTS

Thymic tissue was collected from 11 human immunodeficiency virus 1 (HI V-1)-seropositive drug users who died suddenly of drug intoxication or trauma. None of the 11 individuals had symptoms related to HIV-1 infe ction or were known to be seropositive for HIV-1 before death. Seconda ry B-cell follicles were present in every thymus, and Warthin-Finckeld ey giant cells were noted in three cases. These follicles were enlarge d or fragmented and appeared similar to those in lymph nodes excised f rom the same individuals. Localization of viral RNA by in situ hybridi zation demonstrated abundant virus in a follicular center cell distrib ution within hyperplastic follicles and in scattered medullary lymphoc ytes. In nine thymus glands from seronegative drug addicts and five th ymus glands from seronegative trauma victims who were not drug addicts , secondary follicles were absent and no hybridization signal was pres ent. Other than the presence of germinal centers associated with HIV-1 RNA, there were no histologic differences among the thymus glands of seropositive drug addicts, seronegative drug addicts, and seronegative controls without a history of drug abuse. We conclude that the thymus gland in early stages of infection with HIV-1 is characterized by ind uction of secondary B-cell follicular hyperplasia in medullary tissues , the germinal centers of which contain abundant viral RNA.