False-positive sera do not react with human immunodeficiency virus (HIV) gag-encoded recombinant antigen

Area of Science:

• Immunology
• Virology
• Biochemistry

Background:

• Enzyme-linked immunosorbent assay (ELISA) is a common method for initial human immunodeficiency virus (HIV) screening.
• Western blot assays are often used to confirm ELISA-positive results.
• Understanding the specific viral proteins and epitopes involved in antibody detection is crucial for diagnostic accuracy.

Purpose of the Study:

• To investigate the reactivity of sera from healthy blood donors, confirmed positive by ELISA, using immunoblot assays.
• To determine which specific viral proteins (p17, p24, or a combination) are recognized by these antibodies.
• To assess the role of recombinant proteins and potential new epitopes in HIV seropositivity confirmation.

Main Methods:

• Sera from ten healthy blood donors, ELISA-positive for HIV, were analyzed using immunoblot assays.
• Both natural and recombinant viral proteins were used as antigens.
• Reactions were further characterized by preincubation with genetically engineered proteins and purified viral p24 to block specific epitopes.

Main Results:

• All ten sera reacted specifically with either p17 or p24 proteins.
• None of the sera reacted with a recombinant protein (RP 50) containing determinants for both p17 and p24.
• Preincubation did not block reactions, suggesting the formation of new epitopes during the Western blot procedure.

Conclusions:

• Confirmation of human immunodeficiency virus (HIV) seropositivity requires the use of recombinant gag-encoded proteins.
• The study highlights the importance of specific protein targets and potential epitope variations in diagnostic assays.
• The findings suggest that Western blot procedures may generate novel antigenic sites influencing serological results.