Human induced pluripotent stem cell-derived salivary gland organoids model SARS-CoV-2 infection and replication.

Salivary glands act as virus reservoirs in various infectious diseases and have been reported to be targeted by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the mechanisms underlying infection and replication in salivary glands are still enigmatic due to the lack of proper in vitro models. Here, we show that human induced salivary glands (hiSGs) generated from human induced pluripotent stem cells can be infected with SARS-CoV-2. The hiSGs exhibit properties similar to those of embryonic salivary glands and are a valuable tool for the functional analysis of genes during development. Orthotopically transplanted hiSGs can be engrafted at a recipient site in mice and show a mature phenotype. In addition, we confirm SARS-CoV-2 infection and replication in hiSGs. SARS-CoV-2 derived from saliva in asymptomatic individuals may participate in the spread of the virus. hiSGs may be a promising model for investigating the role of salivary glands as a virus reservoir.

Effects of Extraoral Suction on Droplets and Aerosols for Infection Control Practices.

Dental professionals are at increased risk of being infected with airborne pathogens such as SARS-CoV-2 because they are often exposed to droplets/aerosols production during dental treatment. To scientifically clear the effects of extraoral and oral suctions on the droplets and aerosols produced by dental treatments using an ultrasonic scaler was analyzed. The adenosine triphosphate and bacteria in droplets and aerosols produced during simulated scaling were quantitatively observed by reactions with luciferin/luciferase and incubation in culture plates to grow bacteria, respectively. The protection against spreading droplets and aerosols by oral and extraoral suctions was recognized, and the areas were limited to the left and posterior sides of the dental chair head when a right-handed dentist and dental hygienist performed scaling. Extraoral suction is a very useful tool for reducing the infection risk of COVID-19 in dental care, but the effective area is limited depending on physical characteristics of dentist and dental hygienist.

The Impact of Oral Health on Respiratory Viral Infection.

Influenza virus and severe acute respiratory syndrome coronavirus (SARS-CoV-2) have caused respiratory diseases worldwide. Coronavirus disease 2019 (COVID-19) is now a global health concern requiring emergent measures. These viruses enter the human body through the oral cavity and infect respiratory cells. Since the oral cavity has a complex microbiota, influence of oral bacteria on respiratory virus infection is considered. Saliva has immune molecules which work as the front line in the biophylactic mechanism and has considerable influence on the incidence and progression of respiratory viral infection. Salivary scavenger molecules, such as gp340 and sialic acid, have been reported to exert anti-influenza virus activity. Salivary secretory immunoglobulin A (SIgA) has potential to acquire immunity against these viruses. Biological features of the oral cavity are thought to affect viral infection in respiratory organs in various ways. In this review, we reviewed the literature addressing the impact of oral conditions on respiratory infectious diseases caused by viruses.