DIARECT Newsletter November 2018



Dear Madam or Sir,

DIARECT will be exhibiting at MEDICA 2018, the world’s largest medical trade show that will take place in Düsseldorf, Germany from November 12 – 15, 2018. At this event, we will introduce new products added to our most recent product lines recombinant allergens and human chimeric antibodies.

As a valued customer we would like to invite you to stop by our booth D27 in hall 3A to find out more about our extended range of products and receive a copy of our new product catalog. To access this catalog online, please follow this link: Catalog.

In case you wish to schedule a personal appointment to meet with a member of our team or to receive more information about other topics of interest, please feel free to contact us at: 

Email   info(at)
Tel.     +49 761 47979-0 

Pleasant reading!



Recombinant Shrimp Allergen: Pen a 1

Penaeus aztecus (brown shrimp), also known as Farfantepenaeus aztecus, is closely related to the most imported species of farmed crustaceans worldwide, the giant tiger prawn (P. monodon). Despite the fact that shrimp-based food is a significant source of cholesterol, it is considered healthy for the cardiovascular system, due to the low levels of saturated fat. The high cholesterol content in shrimp improves the ratio of LDL to HDL cholesterol and lowers triglycerides. Moreover, shrimp is high in calcium, iodine, protein and omega-3s. However, hypersensitivity to crustacean food is relatively common and clinical manifestations following ingestion can be severe, including local and systemic reactions, which can lead, in the most severe cases, to life-threatening anaphylaxis.

The use of recombinant proteins in allergy diagnostics has several advantages over crude allergen extracts including more precise quantification of the immunologically active substance. Extracts that are prepared from natural sources may contain mixtures of several proteins including non-allergens, and can vary from batch to batch. Recombinant allergens are therefore the ideal basis to improve component resolved diagnostics (CRD) since large quantities with high purity and standardized quality can be produced. 

Although a large number of crustacean and mollusk species have been studied, only a few IgE-binding proteins have been identified. In the majority of these studies the identified allergen component is tropomyosin and its isoform variants in other invertebrates. The protein, considered to be the only major allergen in shrimp, is a highly conserved and soluble muscle protein characterized by an alpha-helical homodimeric, coiled-coil structure. It plays a functional role in contractile activities of cells and is therefore important in the regulation of cell morphology and motility. Immunological relationship due to IgE cross-reactivities among crustaceans and the high degree of homologous regions within this protein family suggest that tropomyosin is an important cross-sensitizing pan allergen. 

Tropomyosin of P. aztecus (34 - 38 kDa), designated Pen a 1, is representative of shrimp tropomyosin, used in the investigation of food allergies in which tropomyosin is a major determinant. From the thirteen different allergens identified in brown shrimp, it is the best characterized, been detected in sera of more than 80% of shrimp allergic subjects, and binds to 75% of the shrimp-specific IgE.

DIARECT’s recombinant Pen a 1 has close biochemical and immunological similarity to purified natural tropomyosin and is produced in the baculovirus/insect cell expression system.

Table: DIARECT’s recombinant and native purified food allergens

Atifi et al. (2015) Parasitol Res. DOI 10.1007/s00436-015-4698-2
Castillo et al. (1994) Allergol Immunopathol. 22: 83–87
Daul et al. (1991) J Allergy Clin Immunol. 87:192
Daul et al. (1993) CRC press. 291-294
Daul et al. (1994) Int Arch Allergy Immunol.105:49-55
DeWitt et al. (2004) Mol Nutr Food Res. 48: 370– 379
Jeoung et al. (1997) J Allergy Clin Immunol. 229–234
Lehrer et al. (1987) J Allergy Clin Immunol. 80: 133 –139
Reese et al. (1999) Int Arch Aller Immunol. 119: 247-258
Sadek et al. (2018) BioInvasions Rec. 7: 51–54
Shanti et al. (1993)  J Allergy Clin Immunol. 151: 5354-5363
Silva et al. (1996) Am J Clin Nutr. 64:712–717
Waring et al. (1985) J Allergy Clin Immunol. 76: 440–445
Wang et al. (2013) PLoS One. 8 (10): e78189


New Human Chimeric Monoclonal Antibodies: PL-7 humAb IgG, PL-12 humAb IgG and Sp100 humAb IgG

For mRNA translation at the ribosomes, amino acids are covalently attached (“loaded”) onto their respective tRNAs by specific aminoacyl-tRNA synthetases. Threonyl-tRNA synthetase (PL-7) is specific for the amino acid threonine and Alanyl-tRNA synthetase (PL-12) is specific for the amino acid alanine.

PL-7 and PL-12 autoantibodies are considered important serological markers in dermatomyositis, an idiopathic myopathy characterized by the presence of inflammatory infiltrates within skeletal muscle. Together with polymyositis, dermatomyositis is one of the most common subtypes of these idiopathic myopathies along with inclusion body myositis, childhood myositis, malignancy-associated myositis, and myositis in overlap with mixed connective tissue disease. To date, autoantibodies targeting eight of the 20 aminoacyl-tRNA synthetases have been identified, being found in up to 30% of sera from patients with myositis. They are highly specific for this disorder and strongly associated with complicating lung disease.

Sp100 is a nuclear protein with a deduced molecular weight of 55 kDa that is named after its speckled/multinuclear dots pattern (MND-ANA) in IIF and aberrant mobility at 100 kDa in protein gels. The cellular function of Sp100 is not well understood, but it appears to be involved in the regulation of gene transcription and the cellular response to viral infections. Primary Biliary Cirrhosis (PBC) is a chronic and progressive autoimmune liver disease, which is characterized by the destruction of bile ducts and portal inflammation leading to liver cirrhosis and consequently to hepatic failure. Autoantibodies are directed against Sp100, found in approximately 25% of PBC patients and are considered a highly specific marker in the diagnosis of this disease.

Technological breakthroughs and innovative technologies continue to shape the in vitro diagnostic field. One of these advances in assay development are chimeric monoclonal antibodies for use as positive controls or calibrators in IVD kits as an alternative to characterized disease state plasma, which are limited in availability, show variability, and have safety and ethical issues.

These chimeric monoclonal antibodies are produced in transgenic mouse strains in which the sequence for mouse IgG1 Fc region is substituted with the human sequence. After mouse immunization and hybridoma technology, antibodies are generated that retain a human constant region required for recognition by the anti-human conjugate. These monoclonal antibodies can then be produced using standard cell culture technologies.

DIARECT has been continually expanding the line of tissue-specific chimeric antibodies for the detection and diagnosis of autoimmune liver diseases, and with these new products, we have completed our portfolio of myositis antibodies.

Betteridge et al. (2011) Arthritis Research & Therapy. 13:209-215
Cogné et al. (2013) European Patent N°13305964.2
Gunawardena et al. (2015) Clinic Rev Allerg Immunol.  DOI 10.1007/s12016-015-8513-8
Invernizzi et al. (2008) World J Gastroenterol. 21:3374-3387
Mathews et al. (1984) J Exp Med. 160:420-434
Oertelt et al. (2007) Hepatology. 45 (3): 659-665
Yamasaki et al. (2006) Arthritis & Rheumatism. 54: 2004–2009
Zhang et al. (2014) Hepatology. 60: 1708–1716
Sherer et al. (2004) Semin Arthritis Rheum. 34:501-537


Combating Matrix Interferences: Maximize Signal-to-Noise Ratio Without Serum Side Effects Launch: MatrixGuard Diluent (SM02)

Due to the variability within patient samples, assay developers historically have deployed different blocking strategies in immunoassays to achieve assay performance.  One strategy has been to use specific antibodies (e.g., mouse IgG) or serum in the sample diluent to block matrix interferences and sample induced non-specific binding.  However, the sourcing, cost of material, lot-to-lot variability and instability of these additive proteins may introduce more issues for the assay developer.

Data shown here demonstrates a common matrix interference problem overcome without the use of species-specific IgG or serum.  Briefly, a biotinylated detection antibody was diluted into each of the three tested sample buffers (as defined on the graph) and then added to an antibody coated 96 well ELISA plate.  Immediately, a positive control, negative control and a known false positive serum sample were then added to the plate.  Using a streptavidin-HRP and TMB detection system, the graph shows the signal at 650 nm for each sample and buffer combination. 

MatrixGuard™ Diluent demonstrates the ability to maintain assay integrity by providing similar positive and negative control signal compared to the customer sample buffer.  The addition of mouse IgG suppressed the signal of the positive control in this assay.  The false positive signal provided by the known discordant serum sample was eliminated with MatrixGuard Diluent as the sample buffer.  MatrixGuard Diluent blocked the false positive signal to a level equivalent to the negative control.

MatrixGuard Diluent is the first choice for assay developers due to the following:

  • Unlike other diluents that either are marginally effective at blocking matrix interferences or alternatively block out true assay signal, MatrixGuard Diluent achieves the goal of maximum blockade of matrix interferences while simultaneously allowing signal to be maintained.
  • MatrixGuard Diluent was formulated to be used without assay specific protein additions.  However, should additional blocking be required, MatrixGuard Diluent allows for species-specific IgG or serum to be added as needed. 
  • MatrixGuard Diluent is formulated with a preservative that is currently listed on the ECHA Article 95 list of approved biocides.  

Surmodics facilities are ISO 13485:2016 and ISO 9001:2015 certified for design, development, production and distribution of in vitro diagnostic technologies. 

For questions or additional information please feel free to contact us at:
Tel: +49 761 47979-0
Email: info(at)



To facilitate the world-wide sales of our antigens, DIARECT has distribution agreements with select companies.

If you are located in North America, DIARECT’s products are exclusively distributed by:

Surmodics IVD, Inc.
9924 West 74th Street
Eden Prairie, MN 55344
Phone +1 952 500 7200
Toll-free +1 800 755 7793
Fax +1 952 500 7201


If you are located in China, DIARECT’s products are distributed by:

Shanghai BioSun Sci&Tech Co., Ltd.
Room K, 5F, Bldg. No.1
825 Zhaojiabang Road
Shanghai 200032
P.R. China
Phone +86 21 54253791
Fax +86 21 64280007