Multiplex immunoassay to measure antibody response to nine HPV vaccine types

Well-characterized HPV serology assays are required to evaluate performance of biosimilar candidate vaccines, reduced dosing schedules and novel administration methods. We report characterization of an expanded assay, M9ELISA, that detects antibodies to HPV virus-like particles (VLP) of nine types using direct IgG ELISA on the Meso Scale Discovery (MSD) electrochemiluminescence platform. The method is based on the previously published M4ELISA which detects antibodies to HPV6,11,16, and 18. It has been modified to add detection of antibodies to HPV31,33,45,52 and 58, and to streamline assay and reduce background. The M9ELISA plates were prepared with purified type specific L1 + L2 VLPs coated on 10-spot/well standard MSD microplates. Results of ELISA on three serial dilutions of serum were read on MSD imager, and titers calculated using the parallel line method. Evaluations included dynamic range, assay reproducibility, and stability over time. We compared M9ELISA results to those from a pseudovirion-based neutralization assay in sera from a mixed cohort of unvaccinated and vaccinated individuals (n = ~116) and to competitive Luminex immunoassay (cLIA) results in sera from a predominantly unvaccinated cohort (n = 4426). The linear range of the assay extended over 5 logs, with inter-assay reproducibility coefficient of variation ≤25% for all types. The pre-coated plates were stable for at least 2 years. Spearman correlation of antibody titers showed excellent correlation with PBNA (r = 0.86-0.97) and moderate correlation (r = 0.52-0.68) with cLIA. Thus, the M9ELISA can serve as a useful platform for high-throughput, sensitive and simultaneous quantitation of the antibody responses to nine HPV vaccine types.

Development and evaluation of multiplexed immunoassay for detection of antibodies to HPV vaccine types

Reliable antibody based-assays are needed to evaluate the immunogenicity of current vaccines, impact of altered dosing schemes or of new vaccine formulations. An ideal assay platform would allow multiplex type-specific detection with minimal sample requirement. We used the Meso Scale Discovery (MSD) electrochemiluminescence based detection platform to develop a multiplex direct virus-like particle (VLP) ELISA to detect antibodies to HPV 6, 11, 16, and 18 with a protocol developed for detection using the SI 6000 imager (M4ELISA). MSD prepared the plates in the 7-spot/well format, using the purified VLPs (4 spots) and PBS+BSA pH7.4 (3 blank spots). Three-point titrations and the parallel line method were used to calculate antibody levels. Dynamic range, precision, and stability of pre-printed plates were determined using a panel of previously characterized sera. Cut-off values using children's sera were established using 99% RLU limits based on the 4-parameter Johnson Su best fit curve. Results of the M4ELISA were compared to competitive Luminex Immunoassay (cLIA) on n = 4454 sera from a predominantly unvaccinated cohort. Using a VLP coating concentration of 80 μg/ml with BSA provided the most robust RLU signal for all types. The dynamic range of the assay was about 1000 fold, with assay variability under 25% for each of the four vaccine types. Long-term stability of the plates extended to about 7 months from the time plates was received in the laboratory after printing. There was moderate agreement (κ = 0.38-0.54) between M4ELISA and cLIA, with antibody detection for each of the 4 types more frequent with M4ELISA. Quantitative analysis however showed a good correlation between concordant samples by both assays (ρ ≥ 0.6). The MSD platform shows promise for simultaneous quantitation of the antibody responses to four HPV vaccine types in a high-throughput manner.

A new dehydrogeranylgeraniol antioxidant from Saururus cernuus that inhibits intracellular reactive oxygen species (ROS)-catalyzed oxidation within HL-60 cells

A new triene, 12,13-dehydrogeranylgeraniol (1), was isolated from the aquatic plant Saururus cernuus and its structure determined spectroscopically. Compound 1 inhibits PMA-induced peroxide-catalyzed oxidation of 2',7'-dichlorodihydrofluorescein dye (DCFH) by reactive oxygen species (ROS) within human promyelocyctic HL-60 cells.

Competition-Mediated Antibiotic Induction in the Marine Bacterium Streptomyces tenjimariensis

Microbial competition for limiting natural resources within a community is thought to be the selective force that promotes biosynthesis of antimicrobial compounds. The marine bacterium Streptomyces tenjimariensis produces the antibiotics istamycin A and B under select laboratory culture conditions; presumably these compounds serve an ecological role under natural conditions. Here we report results of a novel marine microbial competition experiment that examined the impact of co-culture of marine bacteria on istamycin production by S. tenjimariensis. Twelve of the 53 bacterial species tested (i.e., 22.6%) induced Istamycin production; this antibiotic also inhibited growth of the competitor colonies. These results suggest that marine bacterial metabolites serve an ecological role in countering competitive species.

A new indanone from the marine cyanobacterium Lyngbya majuscula that inhibits hypoxia-induced activation of the VEGF promoter in Hep3B cells

A new indanone (1) has been isolated from the filamentous marine cyanobacterium Lyngbya majuscula, and its structure determined spectroscopically. Vascular endothelial growth factor (VEGF) is an important regulator of tumor angiogenesis. Compound 1 inhibits hypoxia-induced activation of the VEGF gene promoter in Hep3B human liver tumor cells, in vitro.