Persistence and decay of human antibody responses to the receptor binding domain of SARS-CoV-2 spike protein in COVID-19 patients

Lack of antibodies to SARS-CoV-2 in a large cohort of previously infected persons

Background

Reports suggest that some persons previously infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lack detectable IgG antibodies. We aimed to determine the proportion IgG seronegative and predictors for seronegativity among persons previously infected with SARS-CoV-2.

Methods

We analyzed serologic data collected from health care workers and first responders in New York City and the Detroit metropolitan area with history of a positive SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) test result and who were tested for IgG antibodies to SARS-CoV-2 spike protein at least 2 weeks after symptom onset.

Results

Of 2,547 persons with previous confirmed SARS-CoV-2 infection, 160 (6.3%) were seronegative. Of 2,112 previously symptomatic persons, the proportion seronegative slightly increased from 14 to 90 days post symptom onset (p=0.06). The proportion seronegative ranged from 0% among 79 persons previously hospitalized to 11.0% among 308 persons with asymptomatic infections. In a multivariable model, persons taking immunosuppressive medications were more likely to be seronegative (31.9%, 95% confidence interval [CI] 10.7%-64.7%), while participants of non-Hispanic Black race/ethnicity (versus non-Hispanic White) (2.7%, 95% CI 1.5%-4.8%), with severe obesity (versus under/normal weight) (3.9%, 95% CI 1.7%-8.6%), or with more symptoms were less likely to be seronegative.

Conclusions

In our population with previous RT-PCR confirmed infection, approximately one in 16 persons lacked IgG antibodies. Absence of antibodies varied independently by illness severity, race/ethnicity, obesity, and immunosuppressive drug therapy. The proportion seronegative remained relatively stable among persons tested up to 90 days post symptom onset.

COVID-19 reinfection: prolonged shedding or true reinfection?

The SARS-CoV-2 pandemic is underway and millions of people have been infected. A large number of patients with COVID-19 have recovered and been discharged. While a number of recovered patients test positive again or even have a recurrence of clinical symptoms. Some researchers believe that a positive retest is related to the long-term persistence of the virus in the body, although there is some evidence in favor of reinfection. In this study, we focus more on the possible reasons for positive retesting, antibody responses, and review of possible reinfection case reports.

Durable SARS-CoV-2 B cell immunity after mild or severe disease

Multiple studies have shown loss of SARS-CoV-2 specific antibodies over time after infection, raising concern that humoral immunity against the virus is not durable. If immunity wanes quickly, millions of people may be at risk for reinfection after recovery from COVID-19. However, memory B cells (MBC) could provide durable humoral immunity even if serum neutralizing antibody titers decline. We performed multi-dimensional flow cytometric analysis of S protein receptor binding domain (S-RBD)-specific MBC in cohorts of ambulatory COVID-19 patients with mild disease, and hospitalized patients with moderate to severe disease, at a median of 54 (39-104) days after onset of symptoms. We detected S-RBD-specific class-switched MBC in 13 out of 14 participants, including 4 of the 5 participants with lowest plasma levels of anti-S-RBD IgG and neutralizing antibodies. Resting MBC (rMBC) made up the largest proportion of S-RBD-specific class-switched MBC in both cohorts. FCRL5, a marker of functional memory when expressed on rMBC, was dramatically upregulated on S-RBD-specific rMBC. These data indicate that most SARS-CoV-2-infected individuals develop S-RBD-specific, class-switched MBC that phenotypically resemble germinal center-derived B cells induced by effective vaccination against other pathogens, providing evidence for durable B cell-mediated immunity against SARS-CoV-2 after recovery from mild or severe COVID-19 disease.

The immunology of SARS-CoV-2 infections and vaccines

SARS-CoV-2, the virus that causes COVID-19, emerged in late 2019, and was declared a global pandemic on March 11th 2020. With over 50 million cases and 1.2 million deaths around the world, to date, this pandemic represents the gravest global health crisis of our times. Thus, the race to develop a COVID-19 vaccine is an urgent global imperative. At the time of writing, there are over 165 vaccine candidates being developed, with 33 in various stages of clinical testing. In this review, we discuss emerging insights about the human immune response to SARS-CoV-2, and their implications for vaccine design. We then review emerging knowledge of the immunogenicity of the numerous vaccine candidates that are currently being tested in the clinic and discuss the range of immune defense mechanisms that can be harnessed to develop novel vaccines that confer durable protection against SARS-CoV-2. Finally, we conclude with a discussion of the potential role of a systems vaccinology approach in accelerating the clinical testing of vaccines, to meet the urgent needs posed by the pandemic.