title: Anatomical loci of HIV-associated immune activation and association with viraemia.
abstract: BACKGROUND
  Lymphocyte activation, associated with vaccination or infection, can be measured by positron emission tomography (PET). We investigated the ability of PET to detect and measure magnitude of lymph-node activation among asymptomatic HIV-1-infected individuals.
  
  
  METHODS
  Initially we assessed PET response in eight HIV-1-uninfected individuals who had received licensed killed influenza vaccine. In an urban teaching hospital, we recruited 12 patients recently infected with HIV-1 (<18 months since seroconversion) and 11 chronic long-term HIV-1 patients who had stable viraemia by RT-PCR (non-progressors). After injection with fluorine-18-labelled fluorodeoxyglucose, patients underwent PET. We correlated summed PET signal from nodes with viral load by linear regression on log-transformed values.
  
  
  RESULTS
  Node activation was more localised after vaccination than after HIV-1 infection. In early and chronic HIV-1 disease, node activation was greater in cervical and axillary than in inguinal and iliac chains (p<0.0001), and summed PET signal correlated with viraemia across a 4 log range (r2=0.98, p<0.0001). Non-progressors had small numbers of persistently active nodes, most of which were surgically accessible.
  
  
  CONCLUSIONS
  The anatomical restriction we noted may reflect microenvironmental niche selection, and tight correlation of PET signal with viraemia suggests target-cell activation determines steady-state viral replication.
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D019788:Fluorodeoxyglucose F18; D015658:HIV Infections / Q000000981:diagnostic imaging / Q000276:immunology* / Q000821:virology*; D006679:HIV Seropositivity / Q000276:immunology; D015497:HIV-1 / Q000276:immunology / Q000302:isolation & purification; D006801:Humans; D007252:Influenza Vaccines / Q000276:immunology; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014055:Tomography, Emission-Computed; D014766:Viremia / Q000000981:diagnostic imaging / Q000276:immunology; D014779:Virus Replication / Q000276:immunology
chemical_list: D007252:Influenza Vaccines; D019788:Fluorodeoxyglucose F18