P41.10
Background: Induction of both neutralizing antibodies and non-neutralizing antibodies with effector functions e.g. antibody-dependent cellular cytotoxicity (ADCC) are desired in the search for effective vaccines against HIV-1. In the search for novel immunogens capable of inducing an efficient antibody response, rabbits were immunized with selected antigens using different prime-boost strategies within the NGIN consortium.
Methods: We selected 30 different groups of rabbits immunized with antigens from HIV-1 subtype A and B, including immunization with DNA alone, protein alone and DNA prime with protein boost. Rabbit sera were screened for ADCC activity using the GranToxiLux assay with human PBMC as effector cells and CEM.NKRCCR5 coated with rgp120 as target cells. This assay measures the proteolytic activity of Granzyme B after its delivery into target cells, initiated by antibody recognition of rgp120 on the target cell membrane.
Results: The groups of rabbits with the highest serum ADCC activity were immunized with protein, monomeric gp120 or trimeric gp140, in CAF adjuvant. Interestingly, the ADCC activity did not correlate with neutralizing activity of purified IgG measured against SF162 and Bx08 with the pseudovirus-TZMbl assay, nor did it correlate with IgG gp120 ELISA binding titre.
Conclusions: The antigens and/or immunization strategies capable of inducing antibodies with good ADCC activity do not necessarily induce good neutralizing activity and vice versa. When searching for an effective vaccine candidate it is important to evaluate the antibody response using an assay measuring the desired function.
