Long-Term Dysfunction of Taste Papillae in SARS-CoV-2

A recent groundbreaking study titled “Long-Term Dysfunction of Taste Papillae in SARS-CoV-2,” published in NEJM Evidence on July 20, 2023, has provided profound insights into the persistent issues of taste dysfunction experienced by COVID-19 survivors. This study, led by Qin Yao, Maire E. Doyle, Qing-Rong Liu, Ashley Appleton, Jennifer F. O’Connell, Nan-ping Weng, and Josephine M. Egan, delves into the correlation between ongoing taste disturbances and the presence of the SARS-CoV-2 virus in primary taste tissue.

Study Overview:

  1. Objective:
    • To determine the link between prolonged taste disturbances during the post-acute sequelae of COVID-19 and persistent viral presence in primary taste tissue.
  2. Methodology:
    • The study conducted biopsies of fungiform papillae from 16 patients who reported taste disturbances lasting over 6 weeks post-SARS-CoV-2 infection. Subsequent biopsies were performed on 10 of these patients who continued to have taste complaints for at least 6 months post-infection. The team compared these samples to negative controls (fungiform papillae samples taken before March 2020).
    • Diagnostic methods included hematoxylin and eosin staining, immunofluorescence, and fluorescence in situ hybridization to assess fungiform papillae morphology, persistent viral infection, and immune response.
  3. Key Findings:
    • Evidence of Persistent SARS-CoV-2: All patients exhibited indications of SARS-CoV-2 infection and immune response in their fungiform papillae, along with misshapen or absent taste buds and loss of intergemmal neurite fibers.
    • Random Virus Elimination: In 10 patients, the virus was eliminated from their fungiform papillae in a seemingly random manner, but four still reported incomplete recovery of preinfection taste perception.
    • Temporal Association: The study showed a temporal association between the functional taste papillae morphology and the presence of SARS-CoV-2 and its associated immunological changes.

Detailed Insights:

  1. Participant Characteristics:
    • The study involved participants aged 20 to 70 who reported normal taste before COVID-19 but experienced ongoing taste disturbances post-infection.
  2. Evidence of SARS-CoV-2 Persistence in Taste Papillae:
    • SARS-CoV-2 was found in the epithelial layer (basal and suprabasal cell layers) and lamina propria of fungiform papillae in patients with taste deficits from 6 to 63 weeks post-infection.
    • The presence of virus correlated with disrupted taste bud architecture and loss of intergemmal neurite fibers.
  3. Ongoing Immune Response in Presence of Virus:
    • Alongside the virus, there was an increased presence of cytotoxic CD8 T cells and the inflammatory cytokine IL-1b in the fungiform papillae of the patients, indicating an ongoing immune response.
  4. Evidence of Recovery and SARS-CoV-2 Elimination Over Time:
    • Some patients showed recovery of normal fungiform papilla cytoarchitecture and taste function even after experiencing taste dysfunction for more than 11 months post-infection.

Conclusion and Significance:

The study provides compelling evidence linking persistent SARS-CoV-2 presence in taste papillae to prolonged taste dysfunction in post-acute sequelae of COVID-19 patients. It highlights the virus’s ability to reside in the basal and suprabasal cell layers of human fungiform papillae for an extended period post-infection and points towards an ongoing immune response affecting taste perception.

This research is a significant leap in understanding the long-term effects of COVID-19 on the human sensory system, particularly taste dysfunction. The findings not only pave the way for further research into the mechanisms behind prolonged COVID-19 symptoms but also offer hope for developing targeted treatments to alleviate these persistent conditions.

Read More: https://evidence.nejm.org/doi/full/10.1056/EVIDoa2300046

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