Whole body positron emission tomography imaging of activated lymphoid tissues during acute simian-human immunodeficiency virus 89.6PD infection in rhesus macaques

Mechanisms of acute retroviral pathogenesis have been examined during prima ry infection of rhesus macaques with simian-human immunodeficiency virus 89 .6PD (SHIV89.6PD). During acute infection. between initial exposure and est ablishment of antigen-specific immune responses that stabilize the Virus bu rden, rapid immune system changes influence the viral set-point and dictate subsequent steps in disease progression. In a previous study, we described specific patterns of lymphocyte activation during acute SHIV89.6PD infecti on. We now extend these studies to describe lymphoid tissue activation, usi ng whole body positron emission tomography (PET) and the radioactive tracer 2-[F-18]fluorodeoxyglucose (FDG). Within a few days after primary infectio n by intravenous, intrarectal, or intravaginal routes, PET-FDG imaging reve aled a distinct pattern of lymphoid tissue activation centered on axillary, cervical, and mediastinum lymph nodes. Increased tissue FDG uptake precede d fulminant virus replication at these sites, suggesting that a diffusible factor of host or viral origin was responsible for lymphoid tissue changes. These data show that activation of lymphoid tissues in the upper body is a n early response to virus infection and that diffusible mediators of activa tion might be important targets for vaccine or therapeutic intervention str ategies. (C) 2000 Academic Press.