Study detects low SARS-CoV-2 antibody responses in asymptomatic and mild COVID-19 cases

Coronavirus 2019 pandemic (COVID-19) is spreading worldwide. Caused by the acute respiratory infection of coronavirus syndrome 2 (SARS-CoV-2), the disease exhibits several clinical outcomes (from asymptomatic to acute).

Most cases are asymptomatic or have very few symptoms, where there are no symptoms or only a few cases that are easy to treat. These patients recover with the management of the homes.

To date, little is known about the prevalence of specific symptoms in the general population and how these symptoms predict the magnitude of antibody response to SARS-CoV-2 infection.

In a new study, published on the medRxiv * preprint server, researchers at Northwestern University in the US noted high levels of asymptomatic and mild diseases in a large community-based cohort and low levels of immunoglobulin G anti-SARS-CoV-2 (IgG) antibody in the t -population of previously open people. .

Disease and symptoms of SARS-CoV-2

A feature of SARS-CoV-2 is that it has a high proportion of mild or asymptomatic diseases. Asymptomatic diseases are those that have no symptom after being infected with SARS-CoV-2, and mild cases are those with symptoms that are easily treated at home.

For people previously infected with SARS-CoV-2, a serological test can be performed to detect the presence of antibodies. Further, the magnitude of antibody response is related to the effectiveness of neutralization activity in virus challenge trials.

Assessments for antibodies against SARS-CoV-2 can be used to detect previous infection, even if there were no symptoms or clinical diagnosis. These tests may provide insight into future re-infection.

To date, little is known about the extent of pandemic coronavirus infection worldwide. There are few data on the prevalence of COVID-19 symptoms in the general population and how the symptoms of the disease were related to the magnitude of antibody response.

Patterns of symptoms in COVID-19 patients

In the study, the researchers analyzed signal patterns and their relationship to antibody response magnitude using a highly sensitive and quantitative assay for IgG antibodies against SARS-CoV-2 (RBD) receptor binding domain, the structure that binds to the angiotensin-converting enzyme receptor cell 2 (ACE2).

A community-based approach helps to estimate the frequency of specific symptoms and how they affect the development of immunity in the majority of infectious people who recover unnecessarily. on hospital.

The study included 3,365 adults participating in a community-based seroprevalence study in Chicago, USA. Dried blood spot samples were collected at home between June 24 and November 1, 2020.

The study used data from Screening for Coronavirus Antibodies in Neighbors (SCAN), where residents were recruited from 10 zip codes. These partners were recruited through various platforms – social media, emails, newspaper ads, leaflets, and local media coverage. After the participants completed the study form, a stick for a stick dried blood spot (DBS) sample was collected for them.

Participants were asked to report whether they experienced symptoms of COVID-19 after March 1, 2020, including fever or cold, cough, difficulty breathing, sore throat, headache, body aches or muscle pain, runny nose, muscle weakness, diarrhea, nausea, vomiting, loss of smell or taste, and red or itchy eyes. Symptoms have also been noted, including diabetes mellitus, hip intolerance, obesity, cardiovascular disease, smoking, and chronic obstructive pulmonary disease (COPD).

The results of the study showed that 17.8 percent of the sample was seropositive for SARS-CoV-2, meaning that these individuals had previously been infected with the virus. Also, some symptoms, including loss of smell or taste, shortness of breath, fever, muscle pain, muscle weakness, cough, diarrhea, and headache were associated with IgG responses against stronger RBD. among seropositive people.

Approximately 39.2 percent of the infections were asymptomatic and 66.7 percent had two or fewer symptoms.

Overall, the study suggests a low level of immunity in the general population of previously exposed people. In most of these cases there were no or very few symptoms and they were managed at home.

Given the potential difficulties of low levels of antibodies among those with pre-existing moderate disease for the management of the pandemic, further study should be conducted to examine the observed link between symbolic disease, depth of disease, and antibody titers in recovered individuals.

* Important message

medRxiv publish preliminary scientific reports that are not peer-reviewed and, therefore, should not be seen as final, guiding health-related clinical / behavioral practice, or be treated as information established.