Purification and immunological evaluation of HIV-1 envelope proteins.

Envelope proteins of the human immunodefiency virus (HIV) use the cell surface CD-4 molecule of target cells to initiate infection which eventually lead to the acquired immunodeficiency syndrome (AIDS). HIV-1 strains form three groups, namely the M, N and O, with the former group further divided into at least ten equidistant subtypes or clades (i.e. A through J) classified on the basis of sequence homologies in the envelope gene. Recombinant envelope proteins expressed in transfected Chinese hamster ovary (CHO) cells were isolated and purified here (~ 0.01 mg yield). An economical but efficient purification procedure using affinity chromatography and freeze-drying was developed. The results obtained through SDS-PAGE, western blotting, specific ELISA (using Galanthus nivalis a lectin with affinity for ENV glycoproteins) and partial sequencing confirmed the purity (~ 85 - 90 %) and identity of the proteins. Since these proteins were derived in a clade A (Uganda) and B (USA) environment we anticipated limited crossreactivity with immune responses induced in a subtype C (RSA) environment. This was assessed using ELISA (titers of 1000) and western blot analysis. The ability to induce apoptosis was used to demonstrate functionality of the purified protein (Results showed that in-vitro induction of apoptosis (65 %) using the continuous cell line PM1 was achieved).Dr. Debra Meye