INTRODUCTION
During the first wave of the COVID-19 pandemic, olfactory dysfunction
(OD) was one of the most common (50-85%) and long-lasting symptoms of
COVID-19 patients1,2. Between 5-10% of patients,
presented a persistent OD beyond a year after onset3.
Long-term OD appears to be related to the destruction of the
neuroepithelium but the mechanisms underlying this destruction remain
poorly understood4,5. Persistence of SARS-CoV-2
replication in the neuroepithelium, potentially promoted by defective
mucosal immunity, may be involved6. We previously
reported lower nasal and salivary IgG levels in patients with persistent
anosmia as compared to patients with more transient
symptoms7. On the other hand, studies indicated that
OD is associated with increasing levels of serum antibodies in the first
month following onset of symptoms, suggesting persistent antigen
stimulation8. Together, these data suggest a complex
interaction between viral replication and antibody response when viral
replication in the nasal cavity may be promoted by low antibody
responses and may in turn stimulate antibody production over prolonged
periods of time9. More insights are needed on the
relationship between viral replication and mucosal antibody response to
decipher their potentially complex interactions in patients with
COVID-19 OD10.
A potentially important determinant of adaptive immune responses to
SARS-CoV-2 is pre-existing immunity to endemic coronaviruses, including
HKU1, OC43, 229E and NL63, to which patients have been commonly exposed.
Studies suggest that pre-existing immunity to endemic coronaviruses may
reduce the severity of COVID-1911. Whether an impact
on SARS-CoV-2 replication in the nasal cavity can also be observed is
currently unknown. This prospective study was conducted to investigate
the potential relationship between nasal SARS-CoV-2 viral load and
antibody levels in patients with OD.