The antibody response to SARS-CoV-2 increases over 5 months in patients with anosmia/dysgeusia
The factors involved in the persistence of antibodies to SARS-CoV-2 are unknown. We evaluated the antibody response to SARS-CoV-2 in personnel from 10 healthcare facilities and its association with individuals’ characteristics and COVID-19 symptoms in an observational study. We enrolled 4735 subjects (corresponding to 80% of all personnel) over a period of 5 months when the spreading of the virus was drastically reduced. For each participant, we determined the rate of antibody increase or decrease over time in relation to 93 features analyzed in univariate and multivariate analyses through a machine learning approach. In individuals positive for IgG (≥ 12 AU/mL) at the beginning of the study, we found an increase [p= 0.0002] in antibody response in symptomatic subjects, particularly with anosmia/dysgeusia (OR 2.75, 95% CI 1.753 – 4.301), in a multivariate logistic regression analysis. This may be linked to the persistence of SARS-CoV-2 in the olfactory bulb.
It is becoming clear that the antibody response to SARS-CoV-2 can last at least 6 months in symptomatic patients 1, but it seems to decline in asymptomatics 2. Similarly, a reduction of antibody response in asymptomatic individuals was shown in a study with a fewer number of individuals (n = 37) 3. The antibody response in COVID-19 patients is associated with the establishment of a memory B cell response which is higher at 6 months 1, however, it is not clear whether there are features that correlate with this sustained B cell response. We previously showed that an anti-SARS-CoV-2 serological analysis allowed us to follow the diffusion of the virus within healthcare facilities in areas differently hit by the virus 4. At 5 months of distance, we analyzed the duration of this antibody response and evaluated whether there were features correlating with maintenance, reduction or increase of the antibody response.
We assessed the correlation of the rate of antibody increase or decrease with the different analyzed features. In Tables 1 and 2 are reported the rates for individual classes of features with relative statistical analysis. As shown, in the 5 months of observation, females sustained the antibody response better than males (p = 0.01); similarly non-medical healthcare professionals (specifically, healthcare partner operators) had higher antibody rates (p = 0.0009). The levels of antibodies increased in hospitals located in the Bergamo area (Castelli and Gavazzeni p < 0.0001) (Table 1) which was more hit by COVID-19 (37 – 43% of individuals with IgG ≥ 12)7. More important, the IgG rate in individuals which were positive for IgG (IgG ≥ 12 AU/mL; n = 613) at the beginning of the study was increased (p<0.000001) over time, and this increase was either minor in asymptomatics (n = 91, p = 0.00003) and paucisymptomatics (n = 203) or strong in symptomatics (n = 319, p = 0.0006) (Table 2). On the contrary, those that had an intermediate IgG titer (3.8 < IgG < 12 AU/mL considered as negative) displayed all a significant reduction in IgG rate (p < 0.000001) (Table 1). This may be due to a noise in test analysis as these subjects are considered as negative for SARS-CoV-2 IgG according to manufacturer. Many symptoms, including fever, cough, muscle pain, asthenia, tachycardia and anosmia/dysgeusia, correlated with an increase of antibodies in the 5-month observation period (Table 2).
Associated to Zn deficiency?
I have seen crazy low Zn blood levels in COVID-19 patients, especially those with anosmia. I would not be surprised if there is a causal relationship between the two.