Description
Key facts
Detection method:Colorimetric,
Sample types:Citrate plasma, Heparin Plasma, Serum,
Assay Platform:Pre-coated microplate (12 x 8 well strips)
Product details:
SARS-CoV-2 (COVID-19) IgA ELISA Kit (ab277286) is intended for the qualitative determination of IgA class antibodies against SARS-CoV-2 in human serum or plasma (citrate, heparin) to support the diagnosis of COVID-19 disease and constitutes a supplement to direct pathogen detection. In addition, serology can be used to collect epidemiological information on the prevalence of SARS-CoV-2.
Microtiter plates are coated with specific antigens to bind corresponding antibodies of the sample. After washing the wells to remove all unbound sample material a horseradish peroxidase (HRP) labelled conjugate is added. This conjugate binds to the captured antibodies. In a second washing step unbound conjugate is removed. The immune complex formed by the bound conjugate is visualized by adding Tetramethylbenzidine (TMB) substrate which gives a blue reaction product. The intensity of this product is proportional to the amount of specific antibodies in the sample. Sulfuric acid is added to stop the reaction. This produces a yellow endpoint color. Absorbance at 450/620 nm is read using an ELISA Microtiter plate reader.
Antibody Isotypes and State of Infection:
Serology
Significance
Characteristic of the primary antibody response.
High IgM titer: → suggests a current or very recent infection.
Follows IgM production.
Characteristic of the secondary antibody response.
May persist for several years.
High IgG titer with low IgM titer: → may indicate past infection.
Produced in mucosal linings throughout the body (⇒ protective barrier).
Usually produced early in the course of the infection.
Diagnostic Specificity:
The diagnostic specificity is defined as the probability of the assay of scoring negative in the absence of the specific analyte. SARS-CoV-2 infections emerged in December 2019 in Wuhan, China. The expected prevalence values for German and US blood donor panels from before December 2019 therefore amount to 0 %. The determined positive results correspond to a specificity of 98.26 % (95 %-confidence interval: 93.86 % - 99.79 %).
Sample panel
No. patients (n)
Positive
Equivocal
Negative
Specificity
95% CI
Blood donors Germany
Blood donors US
95.92%
98.26%
93.86%-99.79%
Diagnostic Sensitivity:
The diagnostic sensitivity is defined as the probability of the assay of scoring positive in the presence of the specific analyte. 42 samples from 25 patients tested positive for SARS-CoV-2 RNA by RT-PCR were tested.
Days post symptom onset
No. samples (n)
Positive
Equivocal
Negative
Sensitivity (Eqv excluded)
44.44%
44.44%
greater than 12
Interferences:
Three clinical samples exhibiting differing reactivities were tested for interference with each substance listed in the Table below: a positive, a negative, and an equivocal sample. All samples exhibited a change of signal less than 15 % when tested with each potential interferant.
Interferent
Conc. tested
Albumin
60 mg/mL
Bilirubin conjugated
0.4 mg/mL
Bilirubin unconugated
0.4 mg/mL
Cholesterol
4 mg/mL
Hemoglobin
10 mg/mL
Triglycerides
15 mg/mL
Cross Reactivity:
105 samples with antibody activities to potentially cross reacting parameters (including antibodies to several respiratory pathogens) were tested to evaluate the cross reactivity of the assay.
Samples +ve to antibodies to
No. of samples (n)
Positive
Equivocal
Negative
Adenovirus
Parainfluenzavirus
Candida albicans
Bordetella pertussis
Influenzavirus A
Influenzavirus B
Enterovirus
Respiratory syncytial virus
Chlamydia pneumoniae
Legionella pneumoniae
Mycoplasma pneumoniae
Haemophilus influenzae
Other Coronavirus
Cross reactions with antibodies to adenovirus and influenzavirus cannot be excluded. Cross reactivity with other human coronaviruses should be considered for result interpretation.
Properties and Storage Information:
Shipped at conditions-Blue Ice, Appropriate short-term storage conditions-+4°C, Appropriate long-term storage conditions-+4°C, Storage information-+4°C
Supplementary Information:
This supplementary information is collated from multiple sources and compiled automatically.
The SARS-CoV-2 nucleocapsid protein also known as N protein plays a central role in the packaging and replication of the viral RNA genome. It functions mechanically by binding to the viral RNA to facilitate its replication and encapsidation. The nucleocapsid protein is expressed within the virus-infected cells particularly in the cytoplasm. It is a highly conserved structural protein of the virus and has a molecular weight of approximately 50 kDa. Additionally the nucleocapsid protein aids in RNA binding and is essential for the virus's structural stability.
Biological function summary
The nucleocapsid protein of SARS-CoV-2 is involved in maintaining the integrity of the viral genome. It forms a ribonucleoprotein complex with the viral RNA which is necessary for viral replication. The nucleocapsid protein is integral in the formation of the virus's structure and assists in the assembly and release of new virus particles. It interacts with other viral proteins contributing to the stability and functioning of the virus.
Pathways
The nucleocapsid protein is involved in the viral life cycle and replication pathways. The protein participates in the RNA replication and transcription complex working alongside proteins such as the RNA-dependent RNA polymerase and other non-structural proteins. These interactions within the pathways are essential for the efficient replication of the viral genome and production of new viral particles which are key steps in the virus's lifecycle.
The nucleocapsid protein is directly linked to COVID-19 the disease caused by the SARS-CoV-2 virus. It is a target for various diagnostic tests such as the COVID ELISA test and corona IgA test due to its immunogenic properties. The presence of nucleocapsid antibodies in patients is often measured through tests like the ELISA test which helps in diagnosing COVID-19. The nucleocapsid protein's involvement in COVID-19 progression connects it with other viral proteins highlighting its significance in disease mechanisms and potential therapeutic targeting.
