Saliva as a non-invasive diagnostic tool: COVID-19 and T2DM as case-study

Description

Saliva has nowadays a vast research background of how it can mirror the body's health status. Specific salivary biomarkers have been already suggested for multiple diseases and is particularly useful for detecting infectious diseases. We focused on the importance of having a non-invasive, painless and self-collected fluid to study different aspects of two known pandemic diseases: COVID-19 and Type 2 Diabetes Mellitus.
COVID-19 is the most impacting global pandemic of all time requiring frequent testing of populations. The necessity to identify cost-effective strategies for the detection of SARS-CoV-2 outbreak became a priority. Nasopharyngeal samples were considered the sampling golden standard but require a healthcare professional to collect the sample causing discomfort and pain to the patient. As saliva has proved successful in SARS-CoV-2 detection, a pooling strategy could be a good approach to decrease the number of individual tests and hazardous material waste which is also beneficial for the environment. We have tested this strategy on two hundred and seventy-nine saliva samples with pools of 10 and 20 randomized samples through RT-PCR. Cycle Threshold of the genes detected was 29.7. Consecutive reactions analysis of positive samples showed an equivalent cycle threshold average (p < 0.05). Our individual positive sample comparison analysis showed a higher median viral load (32.6) in saliva samples versus nasopharyngeal samples (28.9), with no significant differences detected (p > 0.05). We concluded that saliva-pool samples allowed effective SARS-CoV-2 screening on 10-sample and 20-sample pools. Our strategy was successfully applied in population-wide testing of more than 2000 individuals, showing that it is possible to use pooled saliva as diagnostic fluid for SARS-CoV-2 infection.
The SARS-CoV-2 detection is well established with reliable methodologies including saliva as a detection fluid. In the opposite direction are the molecular alterations induced by this infectious virus which remain elusive. We developed a hybrid proteomics and in silico interactomics strategy to establish a COVID-19 salivary protein profile. The most distinctive proteins between healthy and COVID-19 samples were defined with the Partial Least-Squares Discriminant Analysis and the enrichment analysis was performed with FunRich software. In parallel, Protein-Protein virus-host interactome was identified with OralInt algorithm. Five dysregulated biological processes were identified in the COVID-19 proteome profile: Apoptosis, Energy Pathways, Immune Response, Protein Metabolism, and Transport. We identified 10 proteins (KLK 11, IMPA2, ANXA7, PLP2, IGLV2-11, IGHV3-43D, IGKV2-24, TMEM165, VSIG10, and PHB2) that had never been associated with SARS-CoV-2 infection, representing new evidence for the molecular profile behind COVID-19. Interactomics analysis showed viral influence on the host immune response, mainly through interaction with the degranulation of neutrophils. From our results, we can conclude that the virus also alters the host’s energy metabolism and interferes with apoptosis mechanisms.
Type 2 Diabetes Mellitus is a chronic metabolic disease and is a major health risk due to its characteristic long-term complications. It is estimated that about 537 million people live with diabetes worldwide and will continue to increase. Diagnosis and glucose monitoring in diabetes are well established. However, monitoring the many of diabetes complications remains a challenge, compromising patients' prognosis and quality of life. We established a hybrid strategy that identified salivary markers of T2DM and its complications. From the functional analysis we highlight metabolic processes, response to stimulus, immune system processes and signalling as disrupted biological processes by the known relation with T2DM. The enrichment analysis identified 11 deregulated biological processes emphasizing 20 proteins directly related to complications in diabetes. Diabetic retinopathy, metabolic syndrome, insulin resistance, molecular impact of glucose and insulin homeostasis dysregulation, atherosclerosis, diabetic foot ulcer, protein catabolism and salivary gland function are diabetic complication capable of being monitored using saliva. We conclude that saliva has the potential to identify several molecules altered in diabetic patients compared to non-diabetic patients and that may be biomarkers not only of diabetes but also of the different complications of this disease.
In conclusion, with this research we have confirmed the potential of saliva as a fluid of interest in both diagnosing and discovering new insights into diseases. Saliva was crucial in demonstrating the flexibility and capacity of its use demonstrated by the development of a reliable detection of SARS-CoV-2, the identification and discussion of molecular aspects of viral infection in and with the host, and the discovery of new markers in the diagnosis and monitoring of Type 2 Diabetes Mellitus.

Period	1 Jul 2018 → 27 Jun 2023
Degree of Recognition	PhD