Coronaviruses, which were discovered in the 1960s, belong to the family of enveloped RNA viruses. They fall in the group...
...in the group of zoonotic infections that cause diseases of the respiratory and digestive tracts in humans and animals (birds, mammals). Coronaviruses cause diverse clinical pictures, from common cold to severe respiratory syndromes (MERS, SARS and COVID-19). The majority of known coronaviruses circulate among animals. Alpha- and Beta-coronaviruses can infect only mammals whereas Gamma- and Delta-coronaviruses infect both birds and mammals. Alpha- and Beta-coronaviruses occur in humans. A total of 7 types of human coronaviruses are known so far – 229E, NL63, OC43, HKU1, MERS, SARS, SARS – 2.
Transmission: The infection can be transmitted from an infected person 1–3 days before the onset of the disease. The new coronavirus is a respiratory virus. It is primarily transmitted to an individual through a close contact with an infected person, during which infectious droplets spread to the environment, especially when the infected person talks, coughs and/or sneezes. Things freshly contaminated with secretions of an infected person can also contribute to the transmission. The virus has been successfully isolated from samples taken from the lower respiratory tract (bronchoalveolar lavage). Viral RNA has been detected in nasopharyngeal and throat swabs, serum, blood, rectal swabs, saliva, urine and faeces.
The virus has been found in airway samples 1–2 days before the onset of symptoms and up to 8 days after the onset in case of a mild disease, longer in case of a more severe disease development. Susceptibility seems to be general. Existing experience suggests that the infection is as likely in children as in adults but with milder clinical manifestations. Immunity to COVID-19, if any, has not been established so far. Reported mortality ranges from 2% to 3%. Due to the several-day-long interval between the first symptoms and the onset of the antibody response (the "window period"), serological tests play only a supporting role and, as stressed by the WHO, the results of such tests should always be verified by direct detection of the virus to diagnose an acute COVID-19 disease. Determination of the level of antibodies present after the disease is also an option.
SARS-CoV-2 virus (COVID-19) contains four structural proteins: spike (S), nucleocapsid (N), envelope (E) and membrane (M) protein. The most commonly used antigens in diagnosis include:
- Nucleocapsid protein (NP) encapsulates viral genomic RNA and forms a major component of the viral structure. NP is a highly antigenic epitope and is associated with several virus-host interactions.
- The receptor-binding domain (RBD), a subunit of the Spike S1 protein, specifically binds to the angiotensin-converting enzyme 2 (ACE2) of the host cell. The binding of RBD to ACE2 is highly associated with the formation of neutralizing antibodies.
Diagnostics of infection
The diagnosis of the disease is based on the clinical picture, epidomiological history, and laboratory test...
...laboratory tests. Due to the several-day-long interval between the first symptoms and the onset of the antibody response (the “window period”), serological tests play only a supporting role and, as stressed by the WHO, the results of such tests should always be verified by direct detection of the virus to diagnose an acute COVID 19 disease. An increase in antibody levels occurs in most patients at 2nd week after the onset of symptoms. Positivity of IgA and IgM class antibodies is usually detected on days 3 - 6, IgG class antibodies subsequently on days 10 - 18 after the onset of symptoms. Serological tests are also used in prevalence studies and their negative result allows termination of a quarantine. The development of antibodies and their persistence after natural infection is a subject of further research.
Antibody testing indirectly detects the virus by measuring an immune response (antibodies) to the virus from blood sample...
Uses of antibody testing
- Screening for epidemiologic studies: of recovered patients to know the true rate of infection, information about prevalence in different population, seroprevalence assessments of immunity in populations
- Providing information about the kinetics of antibodies and their correlation with severity of the disease
- Identification of donors for convalescent plasma therapy
- Prescreening individuals prior to admission into vaccine trials and monitoring their immune responses
- Needed for postvaccine surveillance
- Identification of asymptomatic patients
- Confirmatory test to PCR test
Scientific articles about antibody testing
- Serological Assays for SARS-CoV-2 Infectious Disease: Benefits, Limitations and Perspectives
- Serology assays to manage COVID-19: Measurement of antibodies to SARS-CoV-2 will improve disease management if used correctly
- Convalescent Plasma Therapy: Solution to COVID-19?
- The Role of Antibody Testing for SARS-CoV-2: Is There One?
- Severe Acute Respiratory Syndrome Coronavirus 2–Specific Antibody Responses in Coronavirus Disease Patients
- SARS-CoV-2 viral load and antibody responses: the case for convalescent plasma therapy
- Antibody responses to SARS-CoV-2 in patients of novel coronavirus disease 2019
ELISA COVID-19 TESTLINE KITS
CE, IVD marked
Optimized and validated for detection of IgA, IgG and IgM antibodies against recombinant SARS-CoV-2 Nucleocapsid protein (NCP) or Receptor-binding domain (RBD)
NP – immunodominant, highly antigenic epitope; important in early diagnosis
RBD - S1 subunit of the spike protein, anti RBD antibodies are highly specific;IgA - indicator of the onset of the immune response
The kits are available in SmartEIA format designed for automated processing and evaluation using the Agility® analyzer
MICROBLOT-ARRAY TESTLINE KITS
Microblot-Array and its advantages
- Analysis of up to 96 patient samples per plate
- Low sample consumption – only 10 µl
- Parallel testing of multiple markers simultaneously – time and cost saving diagnostics
- Possibility of automated processing using an ELISA instrument
- Intuitive software for test evaluation
- Evaluation of individual antigens and their association with pathogen species or disease type
- Ready-to-use components
- Identical assay procedure (30–30–15 min.)
- Remote troubleshooting
Microblot-Array COVID-19 kits – antigens
Simultaneous detection of multiple COVID-19 markers (NP, RBD, Spike S2, E, ACE2, and PLPro)
The kit also contains antigens to exclude cross-reactivities with other coronaviruses (MERS-CoV, SARS-CoV etc.)
Nucleocapsid NCP is a potent immunodominant coronavirus antigen that contains diagnostically important epitopes for the diagnosis of SARS-CoV-2.This antigen offers sensitive detection of anti-SARS-CoV-2 IgG antibodies.
RBD - Receptor-binding domain of the S1 subunit of the spike (S) protein of SARS-CoV-2. Anti-RBD SARS-CoV-2 antibodies are highly subtype specific and protective.