Vaccination vs Natural infection. A diagnostic challenge in COVID-19 asymptomatic patients, when the immunity profile is not known.


Vaccine anti-COVID-19

Intense time-trial is developed to obtain the best vaccine anti-COVID-19. Two organisms, one from the UK (Oxford University) and another from China (CanSino Biologics) have achieved the most promising results so far. An adenovirus vector produces both vaccines (ChAdOx1 nCoV-19 and Adenovirus Type 5 Vector respectively) (from chimp and human), a non-replicating viral vector, which avoids all type of infection risks in humans. However, it is particularly noteworthy, that not only these two studies but most of the developing ones are using the SARS-CoV-2 spike (S) glycoprotein as the leading player of this time trial. Different formats have been used to prepare/release this protein, as a purified recombinant protein, as a non-replicating viral vector (as the two more advanced attempts described above) or as a messenger RNA (mRNA)–based vaccine.

On the other way, at an early stage, this protein was highlighted as the favourite antigen for diagnostics purposes, as this protein is essential for the entrance of the virus to the host cells and probably the first one detected by them as an immunogen. For this reason, this protein takes part in nearly all the IVD test for COVID detection in the market.

Detection of antibodies is useful for (i) persons admitted in hospitals with more than five days after the onset of symptoms; (ii) confirmation of infection when there is a suspicion of a false negative of the PCR; (iii) detection of antibodies in personnel that could return to work; (iv) epidemiology studies; (v) identify highly reactive human donors for the generation of hyperimmune serum, (vi) research work and (vii) for vaccine evaluation.

On regards the vaccination, its nature will trigger antibodies against the spike glycoprotein in the blood of the population. For diagnostics, safety, and epidemiological reasons (all the purpose mentioned above), it is of utmost importance to have the possibility to distinguish antibodies that are elicited by infection and obviously, these antibodies against the spike protein would not be suitable anymore. Thus, commercial immunoassays based in the S protein, will not distinguish a natural infection from vaccinated people.

Thus, take the lead to this problem and let’s allow the nucleocapsid (N) protein to be the performer of your IVD test. This antigen is a potent immunogen in other several coronaviruses. This protein is the most abundant virus derived-protein throughout the infection and a suitable candidate for raising antibodies for diagnostic applications.

Rekom Biotech has developed the carboxyl-terminus of the nucleocapsid protein from SARS-CoV 2 to offer our customers a highly sensitive and specific antigen to use in the development of their IVD test. It is a soluble protein, stored in a user-friendly buffer, which makes our protein versatile and easy to adapt to the different platforms of the market. Contact us through and ask for the certificate of analysis or visit our website.

Written by Ana Camacho.