INTERNATIONAL COLLABORATION COMPARING NEUTRALIZATION AND BINDING ASSAYS FOR MONOCLONAL-ANTIBODIES TO SIMIAN IMMUNODEFICIENCY VIRUS

Thirteen laboratories characterized a coded panel of 10 MAbs to SIV(ma c)251 envelope protein in a collaboration organized by the National In stitute of Allergy and Infectious Diseases (NIAID). The MAbs were exam ined against SIV isolates in neutralization and radioimmune precipitat ion, immunoblot, enzyme-linked immunosorbent, and radioimmune assays. Although laboratories employed diverse neutralization assays that vari ed in sensitivity there was agreement on the relative ability of the M Abs to neutralize SIV(mac)251. Additionally, even though the quantity of any single MAb required to neutralize SIV(mac)7251 varied between l aboratories, there was agreement on the rank-order strength for the ri ve neutralizing MAbs. Based on the data from this study, the MAbs were classified according to their neutralization potential as high effici ency (MAb concentration, <5 mug/ml), low efficiency (MAb concentration , 5-100 mug/ml), or nonneutralizing (MAb concentration, >100 mug/ml). The MAbs could be assigned to four serological groups based on ability to cross-neutralize and bind different SIV isolates. The distinction between groups I, II, and III were based on the limited neutralization data obtained with the sooty mangabey isolate.