Viability and recovery of peripheral blood mononuclear cells cryopreservedfor up to 12 years in a multicenter study

The Multicenter ATDS Cohort Study (MACS), an ongoing prospective study of t he natural history of human immunodeficiency virus (HN), has stored biologi c specimens, including peripheral blood mononuclear cells (PBMC), from 5,62 2 participants for up to 12 years, The purpose of the present analysis was to evaluate the quality of the PBMC in the MACS repository in order to test the validity and feasibility of nested retrospective studies and to guide the planning of future repositories, PBMC were collected from MACS particip ants at four centers at 6-month intervals from 1984 to 1995, cryopreserved, and transported to a central repository for storage. A total of 596 of the se specimens were subsequently tested for viability and used to evaluate ce ll function, to conduct immunophenotype analysis, or to isolate HIV. Simple linear regression models were applied to evaluate trends in recovery and v iability over time and by center, Results indicated that from a nominal 10( 7) cells cryopreserved per vial at all four centers, the median number of v iable cells recovered was at least 5 x 10(6) (50% of the number stored) and the median viability was at least 90%. Results suggested that cryopreserve d cells can be stored for at least 12 years with no general tendency toward cell loss over time. Furthermore, there were no statistically significant changes in the percent cell viability according to the length of time froze n, regardless of HIV serostatus or the level of CD4(+) lymphocytes. Storing 10(7) PBMC per vial yields sufficient viable cells for phenotypic and/or f unctional analysis. Results from the MACS provide the basis for the plannin g of future repositories for use by investigators with similar research goa ls.