Linear epitopes of HIV-1, presented as hybrids with Escherichia coli beta-galactosidase or synthetic peptides

Overexpression and purification of a recombinant chimeric HIV type 2/HIV type 1 envelope peptide and application in an accelerated immunobased HIV type 1/2 antibody detection system (AIBS): a new rapid serological screening assay

A chimeric HIV-2/HIV-1 envelope sequence containing an immunodominant region of HIV-2 gp36 and the corresponding region of HIV-1 gp41 was constructed and overexpressed in Escherichia coli. The recombinant product (rp21/18) was purified and applied in a novel antibody-screening assay. Characteristics in the design of this new principle are as follows: (1) the overall assay time is about 30 min; (2) the assay procedure includes three manipulation steps; and (3) the test shows a reliable performance with respect to sensitivity and specificity. The diluted serum sample and the protein G-horseradish peroxidase conjugate are added simultaneously into a coated (hybrid antigen HIV-1/2) and blocked microtiter plate well. The in-batch incubation of serum sample with protein G-horseradish peroxidase saves two manipulation steps that are normally necessary in the five-step procedure of a classical ELISA. AIBS was evaluated with commercially available seroconversion panels and with random negative serum samples from a blood bank. Seroconversion results demonstrated that AIBS has equivalent sensitivity to ELISAs and the third generation assays. The specificity was determined on a total blood donor population of 5012 (Red Cross Vienna, Austria). The repeat reactive rates for donor population were 0.02%. AIBS represents a general immunometric system (not only HIV antibodies). The entire assay procedure of AIBS evaluated for HIV-1/2 screening, including result reporting, can be performed automatically by several commercially available systems. Depending on these systems AIBS is potentially useful in laboratories or blood banks that have both high- and low-volume testing.

Kernel density analysis of variable and conserved regions of the envelope proteins of human immunodeficiency virus type 1 and associated epitopes

A new statistical approach to the study of conservation of amino acid and nucleotide sequences based on kernel density analysis is described that enables analysis of both conserved and highly variable HIV-1 protein sequences. The amino acid sequences of HIV-1 env proteins in 63 isolates were analysed to determine, first, whether the designations of regions identified in 1987 as conserved (C1-C6) or variable (V1-V5) were still valid. Even though the data base used was nine times larger, the designations that were based on seven isolates from five patients remain correct. Second, the new approach enabled the quantifications of the degree of conservation in reported B or T cell epitopes. Using this approach, highly conserved epitopes located in both gp41 and gp120 were identified.