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Development and Characterization of an HPV Type-16 Specific Modified DNA Aptamer for the Improvement of Potency
Jeremiah J Trausch1, Mary Shank-Retzlaff1, Thorsten Verch1
1Department of Vaccine Analytical Development, MRL, Merck & Co., Inc. , West Point, Pennsylvania 19486, United States.
Measuring vaccine potency is critical for vaccine release and is often accomplished using antibody-based ELISAs. Antibodies can be associated with significant drawbacks that are often overlooked including lot-to-lot variability, problems with cell-line maintenance, limited stability, high cost, and long discovery lead times. Here, we address many of these issues through the development of an aptamer, known as a slow off-rate modified DNA aptamer (SOMAmer), which targets a vaccine antigen in the human papillomavirus (HPV) vaccine Gardasil. The aptamer, termed HPV-07, was selected to bind the Type 16 virus-like-particle (VLP) formed by the self-assembling capsid protein L1. It is capable of binding with high sensitivity (EC50 of 0.1 to 0.4 μg/mL depending on assay format) while strongly discriminating against other VLP types. The aptamer competes for binding with the neutralizing antibody H16.V5, indicating at least partial recognition of a neutralizing and clinically relevant epitope. This makes it a useful reagent for measuring both potency and stability. When used in an ELISA format, the aptamer displays both high precision (intermediate precision of 6.3%) and a large linear range spanning from 25% to 200% of a typical formulation. To further exploit the advantages of aptamers, a simplified mix and read assay was also developed. This assay format offers significant time and resource reductions compared to a traditional ELISA. These results show aptamers are suitable reagents for biological potency assays, and we expect that their implementation could improve upon current assay formats.
Measuring vaccine potency is critical for vaccine release and is often accomplished using antibody-based ELISAs. Antibodies can be associated with significant drawbacks that are often overlooked including lot-to-lot variability, problems with cell-line maintenance, limited stability, high cost, and long discovery lead times. Here, we address many of these issues through the development of an aptamer, known as a slow off-rate modified DNA aptamer (SOMAmer), which targets a vaccine antigen in the human papillomavirus (HPV) vaccine Gardasil. The aptamer, termed HPV-07, was selected to bind the Type 16 virus-like-particle (VLP) formed by the self-assembling capsid protein L1. It is capable of binding with high sensitivity (EC50 of 0.1 to 0.4 μg/mL depending on assay format) while strongly discriminating against other VLP types. The aptamer competes for binding with the neutralizing antibody H16.V5, indicating at least partial recognition of a neutralizing and clinically relevant epitope. This makes it a useful reagent for measuring both potency and stability. When used in an ELISA format, the aptamer displays both high precision (intermediate precision of 6.3%) and a large linear range spanning from 25% to 200% of a typical formulation. To further exploit the advantages of aptamers, a simplified mix and read assay was also developed. This assay format offers significant time and resource reductions compared to a traditional ELISA. These results show aptamers are suitable reagents for biological potency assays, and we expect that their implementation could improve upon current assay formats.
