Elevated neopterin and beta 2-microglobulin levels in blood and cerebrospinal fluid occur early in HIV-1 infection.

Neopterin and beta 2-microglobulin (beta 2-M) concentrations in cerebrospinal fluid (CSF) and blood were measured in 56 individuals in various stages of HIV-1 infection. Elevated levels of neopterin as well as beta 2-M were found in the CSF of three patients with primary HIV-1 infection and also in subjects in the early stages of chronic HIV-1 infection, with the highest levels in HIV-1 isolation-positive people. There was a clear correlation between the concentrations of the two substances and the levels seemed to increase in parallel with progress of infection. A similar pattern was found in blood. Higher concentrations of neopterin and beta 2-M in CSF than in blood were found in patients with advanced dementia in particular. These findings indicate that the cellular immune system in the central nervous system (CNS) may be activated during the early stages of HIV-1 infection without concomitant overt neurological symptoms. The pathological processes in CNS and blood seem to develop in parallel rather than being restricted to one compartment.