Virus isolation and quinolinic acid in primary and chronic simian immunodeficiency virus infection

In this 2.5-year study of simian immunodeficiency virus (SIVsm) infection in rhesus monkeys, quinolinic acid (QUIN) levels and virus isolation determinations were made in serial cerebrospinal fluid (CSF) and blood samples to evaluate the relationship between these parameters over the course of infection.

Eight rhesus monkeys were inoculated in the saphenous vein with SIVsm. Four animals were maintained as uninoculated controls. CSF and blood samples were obtained every 1-4 weeks over the course of study. SIV isolation was determined in H9 cells for the CSF and in primary rhesus lymphocyte co-cultures for peripheral blood mononuclear cells (PBMC). QUIN was quantitated in CSF and serum by electron-capture negative chemical ionization gas chromatography mass spectrometry.

All SIV-inoculated animals became CSF and PBMC isolation-positive by 1-3 weeks post-inoculation. Control animals remained SIV-negative. One SIV-positive animal was humanely euthanized at 2 weeks post-inoculation. The three SIV-inoculated animals that were CSF isolation-negative after the fifth week post-inoculation maintained CSF QUIN values < 100 nM, remained CSF and PBMC isolation-negative, and clinically healthy in the chronic course of disease. In contrast, the four SIV-inoculated animals that were CSF isolation-positive 6-8 weeks post-inoculation had CSF QUIN levels as high as 153-565 nM during the second month post-inoculation and remained CSF virus isolation-negative, persistently PBMC isolation-positive, and experienced clinical symptoms of SIV in the chronic course of disease. Three of these four animals have succumbed to SIV infection.

Initial QUIN responses and viral isolation status in the first month post-inoculation were consistent among SIV-inoculated animals with CSF and serum QUIN values significantly higher than those of controls. A divergence within the SIV-inoculated group of animals became apparent within the second month of primary SIV infection and was maintained throughout the course of infection. Persistent PBMC viral isolation and marked elevations of QUIN were linked to symptomatic disease and a poor prognosis for survival. Predominantly negative PBMC viral isolation and slight, but significant, elevations of QUIN were linked to asymptomatic disease with a favorable prognosis for survival.