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Placenta-Specific Protein 1 (PLAC1) is essential for normal placental and embryonic development. It is widely expressed in various types of cancer cells. We produced a panel of anti-mouse plac1 monoclonal antibodies (mAbs) with different applications. Two recombinant proteins were produced containing either the extracellular domain (ED) plus tetanus toxin P2, P30, pan-DR epitope (PADRE), and KDEL3 (main plac1) or ED plus KDEL3 (control plac1). Recombinant proteins were used for immunization and screening. Positive clones were selected by ELISA and flow cytometry. Purified mAbs were tested by ELISA, WB, flow cytometry, immunohistochemistry (IHC), and immunofluorescent (IF). A combination of bioinformatics tools was used to predict the target epitope(s) of the mAbs. Eight anti-mouse plac1 mAbs (all IgG1/κ1) were generated, all reacting with high affinity in ELISA. Seven clones recognized plac1 in both reduced and non-reduced Western blots, while one only recognized the non-reduced form. Cross-inhibition ELISA revealed that all mAbs recognized overlapping epitopes with a shared motif except for 5C9. Four clones reacted with the native antigen in flow cytometry, but none were functional in IF or IHC staining. The produced multifunctional mAbs can be used to investigate different aspects of PLAC1 biology in reproduction and cancer. [Display omitted] • PLAC1 is essential for normal placental and embryonic development and is widely expressed in a vast array of cancer cells. • A panel of anti-mouse plac1 monoclonal antibodies (mAbs) was produced using two sets of plac1 extracellular domain. • MAbs recognized overlapping epitopes, which were predicted to be within the LPEPSEQPNC motif. • All clones were reactive in WB, while four clones recognized native antigen in flow cytometry. • These mAbs could be used to investigate PLAC1 biology in reproduction and cancer. [ABSTRACT FROM AUTHOR]

The coronavirus disease 2019 (COVID-19) pandemic is a serious health problem worldwide. Early virus detection is essential for disease control and management. Viral antigen detection by ELISA is a cost-effective, rapid, and accurate antigen diagnostic assay which could facilitate early viral detection. An antigen-capture sandwich ELISA was developed using novel nucleocapsid (NP)-specific mouse monoclonal antibodies (MAbs). The clinical performance of the assay was assessed using 403 positive and 150 negative respiratory samples collected during different SARS-CoV-2 variants outbreaks in Iran. The limit of detection of our ELISA assay was found to be 43.3 pg/ml for recombinant NP. The overall sensitivity and specificity of this assay were 70.72% (95% CI: 66.01–75.12) and 100% (95% CI: 97.57–100), respectively, regardless of Ct values and SARS-CoV-2 variants. There was no significant difference in our assay sensitivity for the detection of Omicron subvariants compared to Delta variant. Assay sensitivity for the BA.5 Omicron subvariant was calculated as 91.89% (95% CI: 85.17–96.23) for samples with Ct values < 25 and 82.70% (95% CI: 75.19–88.71) for samples with Ct values < 30. Our newly developed ELISA method is reasonably sensitive and highly specific for detection of SARS-CoV-2 regardless of the variants and subvariants of the virus. [Display omitted] • Antigen-based serological assays are efficient methods for SARS-CoV-2 screening. • The viral nucleoprotein is the best target due to protein abundance and stability. • We designed a sandwich ELISA using novel nucleoprotein specific MAbs. • Antigen titer correlates inversely to cycle threshold values in clinical samples. • This assay is sensitive and highly specific irrespective of the viral variants. [ABSTRACT FROM AUTHOR]