Lymphocyte activation-associated with vaccination or infection-can be measured by PET. David Schwartz and Sujatha Iyengar from the Johns Hopkins University Bloomberg School of Hygiene and Public Health, USA, and colleagues studied 12 people with recent HIV-1 infection and 11 people with chronic HIV-1 infection. Cervical and axillary node activation was identified in people with both early and chronic infection; patients with long-term infection who had not progressed to AIDS had small numbers of persistently active nodes, most of which were surgically accessible. PET assessment correlated well with genetic assessment of viral activity done by polymerase chain reaction.
David H Schwartz comments: "With the development of intraoperative PET probes for individual node detection, the feasibility of excisional biopsy to study and remove foci of persistent infection should be investigated. Although many systemic sites from which latent virus could re-activate would be left, re-activation might not occur for months or years after removal of the active nodes, thereby allowing extended interruptions of treatment."
Authors of a research letter (p 959) report similar findings for whole-body PET images from 15 patients with HIV-1. Assessment of PET scans showed distinct lymphoid tissue activation in the head and neck during acute disease, a generalised pattern of peripheral lymph-node activation at mid-stages, and involvement of abdominal lymph node
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