Provided herein are methods, compositions, kits, and systems for diagnosing, predicting, and treating gastric cancer for a subject based on the presence and level of antibodies against particular H. pylori proteins in a biological sample obtained from the subject. In particular, provided herein are methods for identifying a subject having increased risk of developing gastric cancer, methods for detecting gastric cancer in a subject, methods for determining an H. pylori antibody signature comprising antibodies, contained in a biological sample from a subject, that specifically bind to immobilized H. pylori antigens, and kits comprising components and instructions for performing the methods of this disclosure.

Disclosed are methods and systems for detecting SARS-CoV-2 analytes in dried samples, as for example, dried blood spots. For example, disclosed is a method for measuring an analyte of interest in a dried sample comprising: (a) obtaining a dried sample from a subject; (b) extracting the analyte of interest from the dried sample; and (c) detecting the analyte of interest extracted from the dried sample. In certain embodiments, the analyte of interest is an analyte specific to SARS-CoV-2. Also, the method may include a step of determining a cutoff index (COI) indicative of whether the subject has a detectable amount of the analyte of interest and so is defined as positive, or does not contain a detected amount of the analyte of interest and so is defined as negative, or is defined as indeterminate.

Disclosed are compositions and methods for the detection of a Flavivirus infection. In some embodiments, the method comprises detecting a recent Flavivirus infection by measuring the amount of anti-NS1 IgG3. In other embodiments, the method comprises detecting a prior Dengue virus infection in a subject previously immunized with a Dengue virus vaccine comprising one or more non-Dengue Flavivirus proteins.

Disclosed herein are methods of eliciting an immune response against a polyomavirus (for example, BKV serotype I (BKV-I), BKV serotype II (BKV-II), BKV serotype III (BKV-III) and/or BKV serotype IV (BKV-IV)) and methods of treating or inhibiting polyomavirus-associated pathology (such as polyomavirus-associated nephropathy, BKV-associated hemorrhagic cystitis, or JC virus-associated progressive multifocal leukoencephalopathy; PML). Further disclosed are immunogenic compositions of use in the disclosed methods. Also disclosed are methods of selecting an organ transplant donor and/or recipient including detecting whether the prospective donor and/or recipient has BKV serotype-specific (such as BKV serotype IV-specific) neutralizing antibodies.

Described herein are compositions that comprise one or more Babesia microti antigens, one or more Babesia microti nucleic acid molecules, or one or more anti-Babesia microti antibodies and uses thereof in methods for the prophylaxis of babesiosis, the treatment of babesiosis and the monitoring of individuals undergoing prophylactic or therapeutic administration of the compositions of the invention.

Disclosed are a recombinant RBD protein of SARS-CoV-2, and a method for preparing the same. The recombinant RBD protein has a signal polypeptide sequence, an RBD protein sequence, a transmembrane domain sequence and a tag sequence in order from N-terminus to C-terminus. The recombinant RBD protein may be expressed on cell membranes, which facilitates protein stability, enrichment and detection.

A diagnostically useful carrier includes (a) a peptide including the amino acid sequence set forth in SEQ ID NO:1 or a variant thereof, and (b) a somatic lysate of Toxocara canis larvae. Further, a kit, use, methods, and compositions that include the diagnostically useful carrier are disclosed.

The present invention relates to the diagnosis of Buruli ulcer. The inventors investigated the potential role of local natural antibodies in the recognition of mycolactone produced by M. ulcerans, and confirmed the presence of such antibodies in humans. In particular, the present invention relates to a method of diagnosing Buruli ulcer in a subject comprising detecting anti-mycolactone immunoglobulin (anti-mycolactone IgG) in a biological sample obtained from said subject.

The invention relates to methods and kits for determining a SARS-CoV-2 strain in a sample. The invention further provides methods and kits for detecting a single nucleotide polymorphism (SNP) in a target nucleic acid, wherein the target nucleic acid is a SARS-CoV-2 nucleic acid. The invention further provides methods and kits for detecting one or more antibody biomarkers in a sample.

Provided are a recombinant N protein of SARS-CoV-2 and methods for preparing the same and for purifying the same. The recombinant N protein of SARS-CoV-2 has an N protein sequence, wherein each of both ends of the N protein sequence are linked to an oligolysine fragment. An expression method for the recombinant N protein includes: a. providing a sample including the recombinant N protein; and b. performing cation exchange chromatography resin purification treatment at least once, and collecting breakthrough substance. The method may effectively improve the expression purity of the recombinant N protein.