Humoral immune responses and neutralizing antibodies against SARS-CoV-2; implications in pathogenesis and protective immunity

Abstract

The magnitude and the quality of humoral responses against SARS-CoV-2 have been associated with clinical outcome. Although the elicitation of humoral responses against different viral proteins is rapid and occurs in most infected individuals, its magnitude is highly variable among them and positively correlates with COVID-19 disease severity. This rapid response is characterized by the almost concomitant appearance of virus-specific IgG, IgA and IgM antibodies that contain neutralizing antibodies directed against different epitopes of the Spike glycoprotein. Of particularly interest, the antibodies against domain of the Spike that interacts with the cellular receptor ACE2, known as the receptor binding domain (RBD), are present in most infected individuals and are block viral entry and infectivity. Such neutralizing antibodies protect different animal species when administered before virus exposure; therefore, its elicitation is the main target of current vaccine approaches and their clinical use as recombinant monoclonal antibodies (mAbs) is being explored. Yet, little information exists on the duration of humoral responses during natural infection. This is a key issue that will impact the management of the pandemic and determine the utility of seroconversion studies and the level of herd immunity. Certainly, several cases of reinfection have been reported, suggesting that immunity could be transient, as reported for other coronaviruses. In summary, although the kinetics of the generation of antibodies against SASR-CoV-2 and their protective activity have been clearly defined, their role in COVID-19 pathogenesis and the length of these responses are still open questions.

Impact of both socioeconomic level and occupation on antibody prevalence to SARS‐CoV‐2 in an Egyptian cohort: The first episode

“…In fact, the presence of immunoglobulins in human sera is very debatable in terms of their involvement in providing protection to exposed human subjects to viral infection and their capacity to neutralize the infectious virus 11 . Both the presence and duration of the existence of both IgM and IgG become more important 12–14 especially in light of the availability of several vaccines from human use to provide protection against novel corona infection.…”

In Search of the SARS-CoV-2 Protection Correlate: Head-to-Head Comparison of Two Quantitative S1 Assays in Pre-characterized Oligo-/Asymptomatic Patients

“…In addition, antibody testing can be used to detect humoral immune responses after the infection. Immunoassays detecting anti-SARS-CoV-2 antibodies can be especially valuable to confirm the extent of population exposure and to quantify vaccine responses [ 4 , 5 ].…”

In search for the SARS-CoV-2 protection correlate: A head-to-head comparison of two quantitative S1 assays in a group of pre-characterized oligo-/asymptomatic patients

“…Seroconversion typically starts 5–7 days after SARS-CoV-2 infection [4]. All antibody types (IgA, IgG and IgM) can be detected within the same time frame around week 2–4, and the IgG response persists the longest [4, 6].…”

“…Seroconversion typically starts 5–7 days after SARS-CoV-2 infection [4]. All antibody types (IgA, IgG and IgM) can be detected within the same time frame around week 2–4, and the IgG response persists the longest [4, 6]. The most important targets of humoral response are the nucleocapsid protein (N), involved in viral RNA replication and viral assembly, and parts of the trimeric spike complex, in particular the receptor-binding domain (RBD) of S1 which interacts with the angiotensin-converting enzyme 2 (ACE2) receptor on human cells [7, 8].…”