After several cases of pneumonia with an unfamiliar etiology were observed at the end of 2019, the National Health Commission of China released more details about the epidemic in early 2020. The pathogen was identified as a novel coronavirus and named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as it has a phylogenetic similarity to SARS-CoV. Since then, SARS-CoV-2 has spread rapidly and the resulting coronavirus disease 2019 (COVID-19) has been declared a public health emergency of international concern (PHEIC) by the World Health Organization (WHO). SARS-CoV-2 is highly contagious, and there has not yet been any vaccine or effective treatment that has received approval. So, the best solution for controlling the pandemic will be the simultaneous application of preventive methods, sensitive diagnostic approaches, and using current available drugs, while still developing novel treatments. Coronaviruses are enveloped, non-segmented, single positive-stranded RNA viruses with round or oval particles and a diameter of 50-200 nm. Coronavirus subfamily is divided into four genera: α, β, γ and δ according to serotype and genomic characteristics.
The SARS-CoV-2 belongs to the genus β which has been confirmed to be highly infectious by
research. (https://www.who.int/emergencies/
diseases/novel-coronavirus-2019/situation-reports).
The four major structural proteins of coronavirus are the spike surface glycoprotein (S),
small envelope protein (E), matrix protein (M), and nucleocapsid protein (N). The spike
protein (S) of coronavirus is a type I transmembrane glycoprotein and mediates the entrance
to human respiratory epithelial cells by interacting with cell surface receptor
angiotensin-converting enzyme 2 (ACE2) , the S protein contains distinct functional domains
near the amino (S1) and carboxy (S2) termini, the peripheral S1 portion can independently
bind cellular receptors while the integral membrane S2 portion is required to mediate fusion
of viral and cellular membranes . The nucleocapsid protein (N) forms complexes with genomic
RNA, interacts with the viral membrane protein during virion assembly and plays a critical
role in enhancing the efficiency of virus transcription and assembly .
The diagnosis of COVID-19 is dependent mainly on clinical characteristics, CT imaging and a
few laboratory tests. Although some symptoms and laboratory parameters have indicative values
in confirmed patients, they are not unique to SARSCoV-2 infection. The most used and reliable
test for diagnosis of COVID-19 has been the RT-PCR test performed using nasopharyngeal swabs.
A variety of RNA gene targets are used by different manufacturers, with most tests targeting
1 or more of the envelope (env), nucleocapsid (N), spike (S), RNA-dependent RNA polymerase
(RdRp), and ORF1 genes .
Spread of the COVID-19 global pandemic highlights the urgent need to develop effective
treatments or vaccines against SARS-CoV-2 infection. The identification of novel antibodies
to neutralize the virus is one of the approaches to fight COVID-19 . In particular, detect an
antibody against the SARS-CoV-2 spike protein by building on knowledge about the existing
structure of SARS-CoV-2 and learnings from previous SARS antibody generations. Potent
neutralizing antibodies often target the receptor interaction site in S1, disabling receptor
interactions. The so-called spike protein of 2019-nCoV is used by the virus to dock to human
cells. By targeting the protein, to prevent the infection.
COVID-19 patients developed SARS-CoV-2-specific NAbs at the convalescent phase of infection
(SARS-CoV-2 NAbs were unable to cross-reactive with SARS-CoV virus). SARS-CoV -2 specific
NAbs reached their peak in patients from day 10-15 after the onset of the disease and
remained stable thereafter in the patients. Antibodies targeting on different domains of S
protein, including S1, RBD, and S2, may all contribute to the neutralization.
Neutralizing antibodies (NAbs) play important roles in virus clearance and have been
considered as a key immune product for protection or treatment against viral diseases.
Virus-specific NAbs, induced through either infection or vaccination, can block viral
infection . NAbs confer immunity by deactivate viruses by block access to receptors used by
the virus to enter host cells and bind to viral capsid and block uncoating of the viral
genome .
The level of NAbs has been used as a gold standard to evaluate the efficacy of vaccines
against smallpox, polio and influenza viruses . Passive antibody therapy, such as plasma
fusion, was successfully used to treat infectious viral diseases, including SARS-CoV virus,
influenza viruses, and Ebola virus. The efficacy of passive antibody therapy was associated
with the concentration of NAbs in plasma or antibodies of recovered donors. As the global
pandemic of COVID-19 proceeds, transfusion of convalescent plasma or serum from recovered
patients was also considered as a promising therapy for prophylaxis of infection or treatment
of disease. highly variable levels of NAbs in the patients of COVID-19 indicated that
convalescent plasma and serum from recovered donors should be titrated before use in passive
antibody therapy, an easy task that can be performed using the PsV neutralization assay. The
titers of NAbs were variable in different patients. Elderly patients (60-80 ys) were more
likely to induce higher titers of NAbs than younger patients. A moderate positive correlation
was also observed between age and Nab titers confirming the important role of age in the
generation of Nabs. The correlation of NAbs titers with age, lymphocyte counts, and blood CRP
levels suggested that the interplay between virus and host immune response.
Inclusion Criteria:
- close contacts of confirmed COVID-19 patients, apparently healthy
Exclusion Criteria:
- symptomatic close contacts, any close contacts with malignant tumor, stroke, cardiac,
respiratory, Gastrointestinal, and renal diseases or any organ dysfunction.
AssiutU
Assiut, Egypt