Antibody Responses in COVID-19: A Review

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread worldwide as a severe pandemic. Although its seroprevalence is highly variable among territories, it has been reported at around 10%, but higher in health workers. Evidence regarding cross-neutralizing response between SARS-CoV and SARS-CoV-2 is still controversial. However, other previous coronaviruses may interfere with SARS-CoV-2 infection, since they are phylogenetically related and share the same target receptor. Further, the seroconversion of IgM and IgG occurs at around 12 days post onset of symptoms and most patients have neutralizing titers on days 14-20, with great titer variability. Neutralizing antibodies correlate positively with age, male sex, and severity of the disease. Moreover, the use of convalescent plasma has shown controversial results in terms of safety and efficacy, and due to the variable immune response among individuals, measuring antibody titers before transfusion is mostly required. Similarly, cellular immunity seems to be crucial in the resolution of the infection, as SARS-CoV-2-specific CD4+ and CD8+ T cells circulate to some extent in recovered patients. Of note, the duration of the antibody response has not been well established yet.

Seroprevalence of SARS-CoV-2 Antibodies in Symptomatic Individuals Is Higher than in Persons Who Are at Increased Risk Exposure: The Results of the Single-Center, Prospective, Cross-Sectional Study

“…The seroconversion of specific SARS-CoV-2 IgG/IgM antibodies can start as early as 4 days [11], with the median time of 7-8 days [12], after the onset of illness, and both IgG and IgM titers plateau within 6 days after seroconversion [13]. Most patients have neutralizing titers on days 14-20 with great titer variability [14]. The duration of the positivity rate exceeding 80% is about seven weeks for IgM and about 3-6 months for IgG [15].…”

Convalescent Plasma the Old Warhorse First to be Inducted in Pandemics is not the Zippy Chippy of Derby

“…The antigen bound antibody can activate, complement and trigger the complement-dependant cytotoxicity. The immune modulation is articulated through signal pathways involving anti-inflammatory cytokines, anti-idiotype antibodies, compliment blocking antibodies and autoantibodies apart from influence on factors involved in homeostasis of haemostasis activating the naval and air defence [ 6 – 9 ].…”

“…The second phase of amplification signals rampant upscaling of inflammatory mediators. In the consummation phase the vicious cytokine release syndrome and the hemophagocytic lymphohistiocytosis and systemic inflammation leads to multi-organ dysfunction syndrome [ 6 – 9 ].…”

“…This mechanism is aided by T-cells through IL-4, IL-21 and the CD40 surface activation. The B cells with maximum affinity for the antigen will continue to divide and differentiate into antibody producing cells, memory cells and plasmacytes that home into the bone marrow factory for long term propagative modelling [ 6 – 9 ].…”

“…Majority of COVID-19 patients will develop antibodies with in the first week, however adequate titres of may take 2 weeks. The Spike-specific (S) and Nucleocapsid-specific (N) antibodies and Receptor Binding Domain (RBD) specific antibodies titres, temporal switch etc., vary with disease severity, and antibodies wax and wane over different timelines [ 6 – 9 ].…”