Cohort profile: a longitudinal study of HIV infection in the central nervous system with focus on cerebrospinal fluid - the Gothenburg HIV CSF Study Cohort.

PURPOSE: In order to enable long-term follow-up of the natural course of HIV infection in the central nervous system, a longitudinal cohort study with repeated cerebrospinal fluid (CSF) analyses at intervals over time was initiated in 1985. When antiretrovirals against HIV were introduced in the late 1980s, short-term and long-term effects of various antiretroviral treatment (ART) regimens were added to the study. PARTICIPANTS: All adult people living with HIV (PLWH) who were diagnosed at or referred to the Department of Infectious Diseases, Sahlgrenska University Hospital, Gothenburg, Sweden were asked to participate in the Gothenburg HIV CSF Study Cohort. PLWH with neurological symptoms or other clinical symptoms of HIV, as well as those with no symptoms of HIV infection, were included. Most participants were asymptomatic, which distinguishes this cohort from most other international HIV CSF studies. In addition, HIV-negative controls were recruited. These included people on HIV pre-exposure prophylaxis who served as lifestyle-matched controls to HIV-infected men who have sex with men. Since lumbar puncture (LP) is an invasive procedure, some PLHW only consented to participate in one examination. Furthermore, at the beginning of the study, several participants were lost to follow-up having died from AIDS. Of 662 PLWH where an initial LP was done, 415 agreed to continue with follow-up. Among the 415, 56 only gave permission to be followed with LP for less than 1 year, mainly to analyse the short-term effect of ART. The remaining 359 PLWH were followed up with repeated LP for periods ranging from >1 to 30 years. This group was defined as the 'longitudinal cohort'. So far, on 7 April 2022, 2650 LP and samplings of paired CSF/blood had been performed, providing a unique biobank. FINDINGS TO DATE: A general finding during the 37-year study period was that HIV infection in the central nervous system, as mirrored by CSF findings, appears early in the infectious course of the disease and progresses slowly in the vast majority of untreated PLWH. Combination ART has been highly effective in reducing CSF viral counts, inflammation and markers of neural damage. Minor CSF signs of long-term sequels or residual inflammatory activity and CSF escape (viral CSF blips) have been observed during follow-up. The future course of these changes and their clinical impact require further studies. FUTURE PLANS: PLWH today have a life expectancy close to that of non-infected people. Therefore, our cohort provides a unique opportunity to study the long-term effects of HIV infection in the central nervous system and the impact of ART and is an ongoing study.