Differences in saliva ACE2 activity among infected and non-infected adult and pediatric population exposed to SARS-CoV-2.

BACKGROUND: Variations in the ACE2 activity in saliva could explain the striking differences of susceptibility to infection and risk of severe disease. METHODS: We analyze the activity of ACE2 in saliva in different population groups across a wide age range and disease status during April to June 2020, before SARS-CoV-2 vaccine implementation, and we establish differences between infected people and participants considered resistant (highly exposed healthcare workers and children who cohabited with parents with COVID-19 without isolation and remain IgG negative). RESULTS: We included 74 adults, of which 47 (64%) were susceptible and 27 (36%) were resistant, and 79 children, of which 41 (52%) were susceptible and 38 (48%) were resistant. Resistant adults have significantly lower ACE2 activity in saliva than susceptible adults and non-significant higher values than susceptible and resistant children. ACE2 activity is similar in the susceptible and resistant pediatric population (p = 0.527). In contrast, we observe an increase in activity as the disease's severity increases among the adult population (mild disease vs. severe disease, 39 vs. 105 FU, p = 0.039; severe disease vs. resistant, 105 vs. 31 FU, p < 0.001). CONCLUSIONS: using an enzymatic test, we show that ACE2 activity in saliva correlates with the susceptibility to SARS-Cov-2 infection and disease severity. Children and adults with low-susceptibility to SARS-Cov-2 infection showed the lowest ACE2 activity. These findings could inform future strategies to identify at-risk individuals.

Analytical validation of an automated assay for the measurement of adenosine deaminase (ADA) and its isoenzymes in saliva and a pilot evaluation of their changes in patients with SARS-CoV-2 infection.

OBJECTIVES: The aim of the present study was to validate a commercially available automated assay for the measurement of total adenosine deaminase (tADA) and its isoenzymes (ADA1 and ADA2) in saliva in a fast and accurate way, and evaluate the possible changes of these analytes in individuals with SARS-CoV-2 infection. METHODS: The validation, in addition to the evaluation of precision and accuracy, included the analysis of the effects of the main procedures that are currently being used for SARS-CoV-2 inactivation in saliva and a pilot study to evaluate the possible changes in salivary tADA and isoenzymes in individuals infected with SARS-CoV-2. RESULTS: The automated assay proved to be accurate and precise, with intra- and inter-assay coefficients of variation below 8.2%, linearity under dilution linear regression with R2 close to 1, and recovery percentage between 80 and 120% in all cases. This assay was affected when the sample is treated with heat or SDS for virus inactivation but tolerated Triton X-100 and NP-40. Individuals with SARS-CoV-2 infection (n=71) and who recovered from infection (n=11) had higher mean values of activity of tADA and its isoenzymes than healthy individuals (n=35). CONCLUSIONS: tADA and its isoenzymes ADA1 and ADA2 can be measured accurately and precisely in saliva samples in a rapid, economical, and reproducible way and can be analyzed after chemical inactivation with Triton X-100 and NP-40. Besides, the changes observed in tADA and isoenzymes in individuals with COVID-19 open the possibility of their potential use as non-invasive biomarkers in this disease.

RNase in the saliva can affect the detection of severe acute respiratory syndrome coronavirus 2 by real-time one-step polymerase chain reaction using saliva samples.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a single-stranded RNA virus that causes coronavirus disease 2019, which spread worldwide immediately after the first patient infected with this virus was discovered in Wuhan, China, in December 2019. Currently, polymerase chain reaction (PCR) specimens for the detection of SARS-CoV-2 include saliva, nasopharyngeal swabs, and lower respiratory tract-derived materials such as sputum. Initially, nasopharyngeal swab specimens were applied mainly to the PCR detection of SARS-CoV-2. There was a risk of infection to healthcare workers due to coughing or sneezing by the subjects at the time of sample collection. In contrast, saliva specimens have a low risk of droplet infection and are easy to collect, and their application to PCR testing has been promoted. In this study, we have determined the detection limit of SARS-CoV-2 in saliva samples and examined the effects of storage temperature and storage time of saliva samples on the PCR detection results. As a result, 5 × 103 copies of SARS-CoV-2 could be detected in 1 mL phosphate-buffered saline, whereas 5 × 104 copies of SARS-CoV-2 were needed in 1 mL saliva to detect the virus by real-time one-step PCR. Interestingly, SARS-CoV-2 (5 × 103 copies/mL) could be detected in saliva supplemented with an RNase inhibitor. Concerning the saliva samples supplemented with an RNase inhibitor, the optimal temperature for sample storage was -20 °C, and PCR detection was maintained within 48 h without problems under these conditions. These finding suggest that RNase in the saliva can affect the detection of SARS-CoV-2 by PCR using saliva samples.

Survey of Saliva Components and Virus Sensors for Prevention of COVID-19 and Infectious Diseases.

The United States Centers for Disease Control and Prevention considers saliva contact the lead transmission means of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes the coronavirus disease 2019 (COVID-19). Saliva droplets or aerosols expelled by heavy breathing, talking, sneezing, and coughing may carry this virus. People in close distance may be exposed directly or indirectly to these droplets, especially those droplets that fall on surrounding surfaces and people may end up contracting COVID-19 after touching the mucosa tissue on their faces. It is of great interest to quickly and effectively detect the presence of SARS-CoV-2 in an environment, but the existing methods only work in laboratory settings, to the best of our knowledge. However, it may be possible to detect the presence of saliva in the environment and proceed with prevention measures. However, detecting saliva itself has not been documented in the literature. On the other hand, many sensors that detect different organic components in saliva to monitor a person's health and diagnose different diseases that range from diabetes to dental health have been proposed and they may be used to detect the presence of saliva. This paper surveys sensors that detect organic and inorganic components of human saliva. Humidity sensors are also considered in the detection of saliva because a large portion of saliva is water. Moreover, sensors that detect infectious viruses are also included as they may also be embedded into saliva sensors for a confirmation of the virus' presence. A classification of sensors by their working principle and the substance they detect is presented. This comparison lists their specifications, sample size, and sensitivity. Indications of which sensors are portable and suitable for field application are presented. This paper also discusses future research and challenges that must be resolved to realize practical saliva sensors. Such sensors may help minimize the spread of not only COVID-19 but also other infectious diseases.