The Anti-SARS-CoV-2 Antibody Response in a Centenarian Woman: A Case of Long-Term Memory?

Abstract

SARS-CoV-2 is the virus responsible for the COVID-19 pandemic, causing respiratory syndrome and other manifestations. The clinical consequences of the SARS-CoV-2 infection are highly heterogeneous, ranging from asymptomatic and mild to severe and fatal conditions, with the highest mortality rate reached among elderly people. Such heterogeneity appears strongly influenced by the host immune response, which in turn is profoundly affected by aging. In fact, the occurrence of a low-grade inflammation and a decline in specific immune defense is generally reported in older people. Although the low ability of B cells to provide primary and secondary specific responses with a consequent increase in susceptibility to and severity of virus infections is generally described in elderly people, we would like to present here the particular case of a 100-year-old woman, who recovered well from COVID-19 and developed a long-term memory against SARS-CoV-2. Following the infection, the patient's blood was tested with both a classical ELISA and a specific Cell-ELISA addressed to measure the anti-spike S1 specific IgG released in plasma or produced in vitro by memory B cells, respectively. While showing negative on classical serological testing, the patient's blood was positive in Cell-ELISA up to 1 year after the infection. Our observation highlights a potential mechanism of B cell-dependent, long-term protection in response to SARS-CoV-2 infection, suggesting that in a case of successful aging, the absence of specific antibodies in serum does not necessarily mean the absence of immune memory.

Keywords: B cell memory; COVID-19; SARS-CoV-2; cell-ELISA; in vitro IgG.

Figure 1

Anterior chest X-ray of the centenarian patient showed a thickening of the peribronchial and bronchilovascular interstitium, probably due to interstitial disease.

Figure 2

Measurement of anti-SARS-CoV-2 spike S1 specific IgG antibodies both in the plasma by ELISA (A) and in PBMC culture, by Cell-ELISA (B) of Negative Control Subjects (NCS) and Positive Control Subjects (PCS) and of the centenarian patient at the two time points (T1 and T2). The dotted area in A and the shaded area in B panel indicate the cut-off OD₄₅₀ value discriminating between negative and positive control values, calculated as the mean OD₄₅₀ value ± 2 SD of negative control subjects, in each condition.