Neutralization titres of HIV-1-specific monoclonal antibodies vary according to the batch of primary human peripheral blood lymphocytes, but do not vary coordinately.

Abstract Human peripheral blood lymphocytes (PBL) were collected from five healthy adults under standard conditions and on a number of different occasions, and used in neutralization assays of human immunodeficiency virus type 1 (HIV-1) strain IIIB with three monoclonal antibodies (mAbs). Variations in neutralization titre were observed with different batches of PBLs with, for example, titres of ICR39.3b ranging from 1/10 to over 1/40000. However titres were as high, or higher, in PBLs than in C8166 cells (a human CD4 + T lymphoblastoid cell line) in 82% (28/34) of tests made. Most surprising was that neutralization by the three mAbs did not vary coordinately. In one batch of PBLs the neutralization titre of one of the mAbs might be increased while that of another mAb did not increase, or decrease. Thus PBLs could not be described as giving high or low levels of neutralization without reference to a specific mAb. This was not an assay problem as infectivity titres were relatively constant (varying by 1 to 1.4 fold with respect to C8166 cells), and neutralization titres were reproducible with the same batch of frozen PBLs over a three month period. Only one donor gave consistently low neutralization titres (defined here as 1/200; 2/2 batches tested) with all three mAbs, but all other donors gave similarly low titres with one of their batches of PBLs. The non-coordinate variation in neutralization titre indicates the advisability of using antibodies of several different specificities in any kind of preventive or therapeutic immunity.