JAMA Netw Open Published online 25 May, 2021 | https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2780134
Digest author(s): Stylianos Loukides, e-Learning Director / 13 June, 2021
Bitter taste receptors in the tongue have been associated with natural immunity to pathogens in both the nose and nasal sinuses. Genetic variations in the genes encoding bitter taste receptors have been associated with different vulnerability, symptomatology, and outcomes in upper respiratory infections. The researchers evaluated the correlation between the different phenotypes of the bitter taste receptor and the outcome of patients with SARS COV-2 infection.
A prospective study was carried out in which participants underwent a taste test to determine each person’s phenotype in terms of the bitter taste receptor. In this way they were divided into people with a particularly enhanced sense of bitter taste (super-tasters), people with a normal sense of bitter taste (tasters) and people with a reduced or zero sense of bitter taste (non-tasters). When they joined the study, all participants were subjected to a PCR test for SARS-CoV-2 and were negative. Participants were monitored until SARS-CoV-2 infection with PCR was confirmed. A group of participants was randomly selected for genotype analysis to correlate phenotype.
A total of 1935 people with an average age of 45.5 years, of whom 1101 were women (56.9%) were super-tasters, 917 (47.4%) were tasters and 510 (26.4%) were non-tasters. A total of 266 cases of COVID-19 laboratory confirmed with PCR were recorded. Of these, 55 (21%) needed hospitalization. The duration of symptoms among patients with a positive PCR test for SARS-CoV-2 was from 0 to 48 days. Non-tasters were significantly more likely (by 10 times) to have a positive PCR test for SARS-CoV-2 compared to tasters and super-tasters, as well as a greater possibility for hospitalization. Furthermore, they had symptoms for a longer period (average duration of symptoms 23.7 days compared to 13.5 days for taster/super-taster. 47 out of 55 patients (85.5%) with COVID-19 who needed inpatient hospitalization were non-tasters. Conversely, only 15 out of 266 patients (5.6%) with a positive PCR test for SARS-CoV-2 were super-tasters. T2R38 receptor allelic variants were associated with participants innate immune response toward SARS-CoV-2.
In conclusion, this study is stressing an important issue. The phenotype of individuals regarding bitter taste receptors is associated with natural immunity against SARS-CoV-2 infection. People with a reduced or zero sense of bitter taste (non-tasters) were more likely to be infected with SARS-CoV-2 than others, who appear to have enhanced intrinsic immune protection against pathogens including SARS-CoV-2.
Three important points: The sense of taste could predispose for SARS COV-2 infection and could predict the severity of the disease. The loss of taste during the infection is not an epiphenomenon, but a clinical sign which needs further assessment and close observation.