Vector competence of Swedish Culex pipiens mosquitoes for Japanese encephalitis virus.

BACKGROUND: Japanese encephalitis virus (JEV) is an emerging mosquito-borne Orthoflavivirus that poses a significant public health risk in many temperate and tropical regions in Asia. Since the climate in some endemic countries is similar to temperate climates observed in Europe, understanding the role of specific mosquito species in the transmission of JEV is essential for predicting and effectively controlling the potential for the introduction and establishment of JEV in Europe. METHODS: This study aimed to investigate the vector competence of colonized Culex pipiens biotype molestus mosquitoes for JEV. The mosquitoes were initially collected from the field in southern Sweden. The mosquitoes were offered a blood meal containing the Nakayama strain of JEV (genotype III), and infection rates, dissemination rates, and transmission rates were evaluated at 14, 21, and 28 days post-feeding. RESULTS: The study revealed that colonized Swedish Cx. pipiens are susceptible to JEV infection, with a stable infection rate of around 10% at all timepoints. However, the virus was only detected in the legs of one mosquito at 21 days post-feeding, and no mosquito saliva contained JEV. CONCLUSIONS: Overall, this research shows that Swedish Cx. pipiens can become infected with JEV, and emphasizes the importance of further understanding of the thresholds and barriers for JEV dissemination in mosquitoes.

Mayaro virus, a potential threat for Europe: vector competence of autochthonous vector species.

BACKGROUND: Mayaro virus (MAYV) is an emerging alphavirus, primarily transmitted by the mosquito Haemagogus janthinomys in Central and South America. However, recent studies have shown that Aedes aegypti, Aedes albopictus and various Anopheles mosquitoes can also transmit the virus under laboratory conditions. MAYV causes sporadic outbreaks across the South American region, particularly in areas near forests. Recently, cases have been reported in European and North American travelers returning from endemic areas, raising concerns about potential introductions into new regions. This study aims to assess the vector competence of three potential vectors for MAYV present in Europe. METHODS: Aedes albopictus from Italy, Anopheles atroparvus from Spain and Culex pipiens biotype molestus from Belgium were exposed to MAYV and maintained under controlled environmental conditions. Saliva was collected through a salivation assay at 7 and 14 days post-infection (dpi), followed by vector dissection. Viral titers were determined using focus forming assays, and infection rates, dissemination rates, and transmission efficiency were calculated. RESULTS: Results indicate that Ae. albopictus and An. atroparvus from Italy and Spain, respectively, are competent vectors for MAYV, with transmission possible starting from 7 dpi under laboratory conditions. In contrast, Cx. pipiens bioform molestus was unable to support MAYV infection, indicating its inability to contribute to the transmission cycle. CONCLUSIONS: In the event of accidental MAYV introduction in European territories, autochthonous outbreaks could potentially be sustained by two European species: Ae. albopictus and An. atroparvus. Entomological surveillance should also consider certain Anopheles species when monitoring MAYV transmission.

Effects of Strain Differences, Humidity Changes, and Saliva Contamination on the Inactivation of SARS-CoV-2 by Ion Irradiation.

One of the methods to inactivate viruses is to denature viral proteins using released ions. However, there have been no reports detailing the effects of changes in humidity or contamination with body fluids on the inactivation of viruses. This study investigated the effects of humidity changes and saliva contamination on the efficacy of SARS-CoV-2 inactivation with ions using multiple viral strains. Virus solutions with different infectious titers were dropped onto a circular nitrocellulose membrane and irradiated with ions from 10 cm above the membrane. After the irradiation of ions for 60, 90, and 120 min, changes in viral infectious titers were measured. The effect of ions on virus inactivation under different humidity conditions was also examined using virus solutions containing 90% mixtures of saliva collected from 10 people. A decrease in viral infectivity was observed over time for all strains, but ion irradiation further accelerated the decrease in viral infectivity. Ion irradiation can inactivate all viral strains, but at 80% humidity, the effect did not appear until 90 min after irradiation. The presence of saliva protected the virus from drying and maintained infectiousness for a longer period compared with no saliva. In particular, the Omicron strain retained its infectivity titer longer than the other strains. Ion irradiation demonstrated a consistent reduction in the number of infectious viruses when compared to the control across varying levels of humidity and irradiation periods. This underscores the notable effectiveness of irradiation, even when the reduction effect is as modest as 50%, thereby emphasizing its crucial role in mitigating the rapid dissemination of SARS-CoV-2.

Oral mouthwashes for asymptomatic to mildly symptomatic adults with COVID-19 and salivary viral load: a randomized, placebo-controlled, open-label clinical trial.

BACKGROUND: Recent randomized clinical trials suggest that the effect of using cetylpyridinium chloride (CPC) mouthwashes on the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load in COVID-19 patients has been inconsistent. Additionally, no clinical study has investigated the effectiveness of on-demand aqueous chlorine dioxide mouthwash against COVID-19. METHODS: We performed a randomized, placebo-controlled, open-label clinical trial to assess for any effects of using mouthwash on the salivary SARS-CoV-2 viral load among asymptomatic to mildly symptomatic adult COVID-19-positive patients. Patients were randomized to receive either 20 mL of 0.05% CPC, 10 mL of 0.01% on-demand aqueous chlorine dioxide, or 20 mL of placebo mouthwash (purified water) in a 1:1:1 ratio. The primary endpoint was the cycle threshold (Ct) values employed for SARS-CoV-2 salivary viral load estimation. We used linear mixed-effects models to assess for any effect of the mouthwashes on SARS-CoV-2 salivary viral load. RESULTS: Of a total of 96 eligible participants enrolled from November 7, 2022, to January 19, 2023, 90 were accepted for the primary analysis. The use of 0.05% CPC mouthwash was not shown to be superior to placebo in change from baseline salivary Ct value at 30 min (difference vs. placebo, 0.640; 95% confidence interval [CI], -1.425 to 2.706; P = 0.543); 2 h (difference vs. placebo, 1.158; 95% CI, -0.797 to 3.112; P = 0.246); 4 h (difference vs. placebo, 1.283; 95% CI, -0.719 to 3.285; P = 0.209); 10 h (difference vs. placebo, 0.304; 95% CI, -1.777 to 2.385; P = 0.775); or 24 h (difference vs. placebo, 0.782; 95% CI, -1.195 to 2.759; P = 0.438). The use of 0.01% on-demand aqueous chlorine dioxide mouthwash was also not shown to be superior to placebo in change from baseline salivary Ct value at 30 min (difference vs. placebo, 0.905; 95% CI, -1.079 to 2.888; P = 0.371); 2 h (difference vs. placebo, 0.709; 95% CI, -1.275 to 2.693; P = 0.483); 4 h (difference vs. placebo, 0.220; 95% CI, -1.787 to 2.226; P = 0.830); 10 h (difference vs. placebo, 0.198; 95% CI, -1.901 to 2.296; P = 0.854); or 24 h (difference vs. placebo, 0.784; 95% CI, -1.236 to 2.804; P = 0.447). CONCLUSIONS: In asymptomatic to mildly symptomatic adults with COVID-19, compared to placebo, the use of 0.05% CPC and 0.01% on-demand aqueous chlorine dioxide mouthwash did not lead to a significant reduction in SARS-CoV-2 salivary viral load. Future studies of the efficacy of CPC and on-demand aqueous chlorine dioxide mouthwash on the viral viability of SARS-CoV-2 should be conducted using different specimen types and in multiple populations and settings.

A shedding analysis after AAV8 CNS injection revealed fragmented viral DNA without evidence of functional AAV particles in mice.

Adeno-associated viruses (AAV) are commonly used in the scientific field due to their diverse application range. However, AAV shedding, the release of virions from the host organism, can impact the safety of AAV-based approaches. An increasing number of authorities require the characterization of vector shedding in clinical trials. Recently, shedding of transduced laboratory animals has also gained attention regarding the necessary disposal measures of their waste products. However, no explicit international regulations for AAV-shedding waste exist. Generating insights into shedding dynamics becomes increasingly relevant to help authorities develop adequate regulations. To date, knowledge of AAV vector shedding in mice is very limited. Moreover, confirmation of functional shed AAV particles in mice is missing. Therefore, we examined feces, urine, and saliva of mice after CNS injection with AAV2/8. It revealed the presence of viral DNA fragments via qPCR for up to 4 days after injection. To examine AAV functionality we performed nested PCR and could not detect full-length viral genomes in any but two collected feces samples. Furthermore, a functional infection assay did not reveal evidence of intact AAV particles. Our findings are supposed to contribute murine shedding data as a foundation to help establish still lacking adequate biosafety regulations in the context of AAV shedding.

Replication-independent change in the frequencies of distinct genome segments of a multipartite virus during its transit within aphid vectors.

Multipartite viruses exhibit a fragmented genome composed of several nucleic acid segments individually packaged in distinct viral particles. The genome of all species of the genus Nanovirus holds eight segments, which accumulate at a very specific and reproducible relative frequency in the host plant tissues. In a given host species, the steady state pattern of the segments' relative frequencies is designated the genome formula and is thought to have an adaptive function through the modulation of gene expression. Nanoviruses are aphid-transmitted circulative non-propagative viruses, meaning that the virus particles are internalized into the midgut cells, transferred to the hemolymph, and then to the saliva, with no replication during this transit. Unexpectedly, a previous study on the faba bean necrotic stunt virus revealed that the genome formula changes after ingestion by aphids. We investigate here the possible mechanism inducing this change by first comparing the relative segment frequencies in different compartments of the aphid. We show that changes occur both in the midgut lumen and in the secreted saliva but not in the gut, salivary gland, or hemolymph. We further establish that the viral particles differentially resist physicochemical variations, in particular pH, ionic strength, and/or type of salt, depending on the encapsidated segment. We thus propose that the replication-independent genome formula changes within aphids are not adaptive, contrary to changes occurring in plants, and most likely reflect a fortuitous differential degradation of virus particles containing distinct segments when passing into extra-cellular media such as gastric fluid or saliva. IMPORTANCE: The genome of multipartite viruses is composed of several segments individually packaged into distinct viral particles. Each segment accumulates at a specific frequency that depends on the host plant species and regulates gene expression. Intriguingly, the relative frequencies of the genome segments also change when the octopartite faba bean necrotic stunt virus (FBNSV) is ingested by aphid vectors, despite the present view that this virus travels through the aphid gut and salivary glands without replicating. By monitoring the genomic composition of FBNSV populations during the transit in aphids, we demonstrate here that the changes take place extracellularly in the gut lumen and in the saliva. We further show that physicochemical factors induce differential degradation of viral particles depending on the encapsidated segment. We propose that the replication-independent changes within the insect vector are not adaptive and result from the differential stability of virus particles containing distinct segments according to environmental parameters.

Evaluation of vector susceptibility in Aedes aegypti and Culex pipiens pallens to Tibet orbivirus.

Mosquito-borne viruses cause various infectious diseases in humans and animals. Tibet orbivirus (TIBOV), a newly identified arbovirus, efficiently replicates in different types of vertebrate and mosquito cells, with its neutralizing antibodies detected in cattle and goats. However, despite being isolated from Culicoides midges, Anopheles, and Culex mosquitoes, there has been a notable absence of systematic studies on its vector competence. Thus, in this study, Aedes aegypti and Culex pipiens pallens were reared in the laboratory to measure vector susceptibility through blood-feeding infection. Furthermore, RNA sequencing was used to examine the overall alterations in the Ae. aegypti transcriptome following TIBOV infection. The results revealed that Ae. aegypti exhibited a high susceptibility to TIBOV compared to Cx. p. pallens. Effective replication of the virus in Ae. aegypti midguts occurred when the blood-feeding titer of TIBOV exceeded 105 plaque-forming units mL-1. Nevertheless, only a few TIBOV RNA-positive samples were detected in the saliva of Ae. aegypti and Cx. p. pallens, suggesting that these mosquito species may not be the primary vectors for TIBOV. Moreover, at 2 dpi of TIBOV, numerous antimicrobial peptides downstream of the Toll and Imd signaling pathways were significantly downregulated in Ae. aegypti, indicating that TIBOV suppressed mosquitos' defense to survive in the vector at an early stage. Subsequently, the stress-activated protein kinase JNK, a crucial component of the MAPK signaling pathway, exhibited significant upregulation. Certain genes were also enriched in the MAPK signaling pathway in TIBOV-infected Ae. aegypti at 7 dpi.IMPORTANCETibet orbivirus (TIBOV) is an understudied arbovirus of the genus Orbivirus. Our study is the first-ever attempt to assess the vector susceptibility of this virus in two important mosquito vectors, Aedes aegypti and Culex pipiens pallens. Additionally, we present transcriptome data detailing the interaction between TIBOV and the immune system of Ae. aegypti, which expands the knowledge about orbivirus infection and its interaction with mosquitoes.

Rapid detection of SARS-CoV-2 spike protein using a magnetic-assisted electrochemical biosensor based on functionalized CoFe2O4 magnetic nanomaterials.

The outbreak of novel coronavirus pneumonia (COVID-19) in 2019 has garnered widespread attention. The virus exhibits high contagiousness, and in certain cases, it can lead to recurrent infections. Therefore, it is imperative to develop portable, sensitive, and accurate sensors to promptly detect infected individuals, control the virus's transmission, and determine suitable treatment strategies. In this study, we proposed a magnetically-assisted method employing CFO@CS-Au MNP as the substrate material, which was functionalized with human angiotensin-converting enzyme (ACE2) for efficient capture of SARS-CoV-2 spike protein in solution. Subsequently, the captured protein was sensitively detected through differential pulse voltammetry (DPV) electrical analysis. The linear detection range of the labeled GCE/MNP/GA/ACE2/BSA electrochemical sensor is from 1 pg/mL to 10 µg/mL, with a minimum detection limit of 0.15 pg/mL. Furthermore, the fabricated GCE/MNP/GA/ACE2/BSA sensor achieved satisfactory recoveries of SARS-CoV-2 spike protein in saliva and nasal swab samples within 10 min. These results indicate that this magnetically-assisted biosensor has established a solid foundation for the swift on-site detection of COVID-19.

Salivary autoantibodies to type I IFNs: Mirror plasma levels, predispose to severe COVID-19, and enhance feasibility for clinical screening.

BACKGROUND: Autoantibodies have been demonstrated to dampen the interferon (IFN) response in viral infections. Elevated levels of these preexisting autoantibodies (aAbs) decrease basal interferon levels, increasing susceptibility to severe infections. OBJECTIVES: This study aimed to evaluate the prevalence of type I IFN aAbs in both plasma and saliva from COVID-19 patients, analyze their neutralizing activity, and examine their associations with clinical outcomes, including the need for mechanical ventilation and in-hospital mortality. METHODS: Prospective analyses of patients admitted to intensive care units in three UAE hospitals from June 2020 to March 2021 were performed to measure aAbs using enzyme-linked immunosorbent assay (ELISA), assess aAbs activity via neutralization assays, and correlate aAbs with clinical outcomes. RESULTS: Type I IFN aAbs (α2 and/or ω) were measured in plasma samples from 213 ICU patients, and positive results were obtained for 20 % (n = 42) of the patients, with half exhibiting neutralizing activity. Saliva samples from a subgroup of 24 patients reflected plasma levels. In multivariate regression analyses, presence of type I IFN aAbs was associated with a higher need for mechanical ventilation (OR 2.58; 95 % CI 1.07-6.22) and greater in-hospital mortality (OR 2.40; 95 % CI 1.13 - 5.07; P = 0.022). Similarly, positive neutralizing aAbs (naAbs) were associated with a greater need for mechanical ventilation (OR 4.96; 95 % CI 1.12-22.07; P = 0.035) and greater odds of in-hospital mortality (OR 2.87; 95 % CI 1.05-7.89; P = 0.041). CONCLUSIONS: Type I IFN autoantibodies can be detected in noninvasive saliva samples, alongside conventional plasma samples, from COVID-19 patients and are associated with worse outcomes, such as greater mechanical ventilation needs and in-hospital mortality.

Noninvasive detection of Zika virus in mosquito excreta sampled from wild mosquito populations in French Guiana.

Arboviruses can be difficult to detect in the field due to relatively low prevalence in mosquito populations. The discovery that infected mosquitoes can release viruses in both their saliva and excreta gave rise to low-cost methods for the detection of arboviruses during entomological surveillance. We implemented both saliva and excreta-based entomological surveillance during the emergence of Zika virus (ZIKV) in French Guiana in 2016 by trapping mosquitoes around households of symptomatic cases with confirmed ZIKV infection. ZIKV was detected in mosquito excreta and not in mosquito saliva in 1 trap collection out of 85 (1.2%). One female Ae. aegypti L. (Diptera: Culicidae) was found with a ZIKV systemic infection in the corresponding trap. The lag time between symptom onset in a ZIKV-infected individual living near the trap site and ZIKV detection in this mosquito was 1 wk. These results highlight the potential of detection in excreta from trapped mosquitoes as a sensitive and cost-effective method to non invasively detect arbovirus circulation.

A high throughput immuno-affinity mass spectrometry method for detection and quantitation of SARS-CoV-2 nucleoprotein in human saliva and its comparison with RT-PCR, RT-LAMP, and lateral flow rapid antigen test.

OBJECTIVES: Many reverse transcription polymerase chain reaction (RT-PCR) methods exist that can detect SARS-CoV-2 RNA in different matrices. RT-PCR is highly sensitive, although viral RNA may be detected long after active infection has taken place. SARS-CoV-2 proteins have shorter detection windows hence their detection might be more meaningful. Given salivary droplets represent a main source of transmission, we explored the detection of viral RNA and protein using four different detection platforms including SISCAPA peptide immunoaffinity liquid chromatography-mass spectrometry (SISCAPA-LC-MS) using polyclonal capture antibodies. METHODS: The SISCAPA-LC MS method was compared to RT-PCR, RT-loop-mediated isothermal amplification (RT-LAMP), and a lateral flow rapid antigen test (RAT) for the detection of virus material in the drool saliva of 102 patients hospitalised after infection with SARS-CoV-2. Cycle thresholds (Ct) of RT-PCR (E gene) were compared to RT-LAMP time-to-positive (TTP) (NE and Orf1a genes), RAT optical densitometry measurements (test line/control line ratio) and to SISCAPA-LC-MS for measurements of viral protein. RESULTS: SISCAPA-LC-MS showed low sensitivity (37.7 %) but high specificity (89.8 %). RAT showed lower sensitivity (24.5 %) and high specificity (100 %). RT-LAMP had high sensitivity (83.0 %) and specificity (100.0 %). At high initial viral RNA loads (<20 Ct), results obtained using SISCAPA-LC-MS correlated with RT-PCR (R2 0.57, p-value 0.002). CONCLUSIONS: Detection of SARS-CoV-2 nucleoprotein in saliva was less frequent than the detection of viral RNA. The SISCAPA-LC-MS method allowed processing of multiple samples in <150 min and was scalable, enabling high throughput.

Within-host evolutionary dynamics and tissue compartmentalization during acute SARS-CoV-2 infection.

The global evolution of SARS-CoV-2 depends in part upon the evolutionary dynamics within individual hosts with varying immune histories. To characterize the within-host evolution of acute SARS-CoV-2 infection, we sequenced saliva and nasal samples collected daily from vaccinated and unvaccinated individuals early during infection. We show that longitudinal sampling facilitates high-confidence genetic variant detection and reveals evolutionary dynamics missed by less-frequent sampling strategies. Within-host dynamics in both unvaccinated and vaccinated individuals appeared largely stochastic; however, in rare cases, minor genetic variants emerged to frequencies sufficient for forward transmission. Finally, we detected significant genetic compartmentalization of viral variants between saliva and nasal swab sample sites in many individuals. Altogether, these data provide a high-resolution profile of within-host SARS-CoV-2 evolutionary dynamics.IMPORTANCEWe detail the within-host evolutionary dynamics of SARS-CoV-2 during acute infection in 31 individuals using daily longitudinal sampling. We characterized patterns of mutational accumulation for unvaccinated and vaccinated individuals, and observed that temporal variant dynamics in both groups were largely stochastic. Comparison of paired nasal and saliva samples also revealed significant genetic compartmentalization between tissue environments in multiple individuals. Our results demonstrate how selection, genetic drift, and spatial compartmentalization all play important roles in shaping the within-host evolution of SARS-CoV-2 populations during acute infection.

Detection and characterization of novel luchacoviruses, genus Alphacoronavirus, in saliva and feces of meso-carnivores in the northeastern United States.

IMPORTANCE: Several coronaviruses (CoVs) have been detected in domesticated, farmed, and wild meso-carnivores, causing a wide range of diseases and infecting diverse species, highlighting their important but understudied role in the epidemiology of these viruses. Assessing the viral diversity hosted in wildlife species is essential to understand their significance in the cross-species transmission of CoVs. Our focus here was on CoV discovery in meso-carnivores in the Northeast United States as a potential "hotspot" area with high density of humans and urban wildlife. This study identifies novel alphacoronaviruses circulating in multiple free-ranging wild and domestic species in this area and explores their potential epidemiological importance based on regions of the Spike gene, which are relevant for virus-host interactions.

SARS-CoV-2 seroprevalence and determinants for salivary seropositivity among pupils and school staff: a prospective cohort study.

Representative school data on SARS-CoV-2 past-infection are scarce, and differences between pupils and staff remain ambiguous. We performed a nation-wide prospective seroprevalence study among pupils and staff over time and in relation to determinants of infection using Poisson regression and generalised estimating equations. A cluster random sample was selected with allocation by region and sociodemographic (SES) background. Surveys and saliva samples were collected in December 2020, March, and June 2021, and also in October and December 2021 for primary pupils. We recruited 885 primary and 569 secondary pupils and 799 staff in 84 schools. Cumulative seroprevalence (95% CI) among primary pupils increased from 11.0% (7.6; 15.9) at baseline to 60.4% (53.4; 68.3) in December 2021. Group estimates were similar at baseline; however, in June they were significantly higher among primary staff (38.9% (32.5; 46.4)) compared to pupils and secondary staff (24.2% (20.3; 28.8)). Infections were asymptomatic in 48-56% of pupils and 28% of staff. Seropositivity was associated with individual SES in pupils, and with school level, school SES and language network in staff in June. Associations with behavioural characteristics were inconsistent. Seroconversion rates increased two- to four-fold after self-reported high-risk contacts, especially with adults. Seroprevalence studies using non-invasive sampling can inform public health management.

Oral human papillomavirus (HPV) infection and HPV vaccination in an Australian cohort.

Human papillomavirus (HPV)-related oropharyngeal cancer (OPC) is increasing in incidence, yet very little is known about oral HPV infection in the general population. In this Australian-based study we assess oral HPV prevalence according to HPV vaccination status. Participants of the Oral Diversity Study were Australian residents, aged 18 to 70 years, who filled out a questionnaire about lifestyle and sexual behaviour, and donated a saliva sample in 2020 to 2021. We obtained permission to access HPV vaccination status through record linkage with the Australian Immunisation Register. Saliva samples were DNA extracted, DNA quality checked and analysed for HPV. We recruited 1023 participants to the Oral Diversity Study. Nine hundred twenty-one returned a saliva sample for analysis, 911 passed the DNA quality check and were included in the study. The oral HPV prevalence was 7.2%, and was strongly associated with sexual behaviours. We identified 27 different HPV types; 53% of participants carried high-risk HPV types, with no difference between the vaccinated and the unvaccinated groups (53% both, P = .979). Two hundred thirty participants (26%) were HPV vaccinated. The oral prevalence of the nine HPV types included in the nonavalent HPV vaccine was significantly lower in the vaccinated participants compared to the unvaccinated (0.9% vs 3.4%; P = .022). These findings suggest that a sizeable minority of Australian residents harbour oral HPV infections, and many of these are high-risk subtypes. We found some evidence that HPV vaccination resulted in lower prevalence of oral HPV infections of vaccine-specific types. Larger surveys are required to confirm these findings.

Microscopic observations of SARS-CoV-2 like particles in different oral samples.

The emerging coronavirus pneumonia epidemic caused by the SARS-CoV-2 infection has spread rapidly around the world. The main routes of transmission of SARS-CoV-2 are currently recognised as aerosol/droplet inhalation. However, the involvement of the oral cavity in coronavirus disease 2019 (COVID-19) is poorly known. The current data indicates the presence of viral RNA in oral samples, suggesting the implication of saliva in SARS-CoV-2 transmission, however, no direct observation of SARS-CoV-2 particles in different oral samples has been reported. In this study, we investigated whether particles of SARS-CoV-2 were present in oral samples collected from three symptomatic COVID-19 patients. Using scanning electron microscopy (SEM), the correlative strategy of light microscopy and electron microscopy and immunofluorescence staining, we showed the presence of SARS-like particles in RT-qPCR SARS-CoV-2-positive saliva, dental plaque and gingival crevicular fluid (GCF) samples. In the saliva samples, we demonstrated the presence of epithelial oral cells with morphogenetic features of SARS-CoV-2 infected cells. Inside those cells, vacuoles filled with nascent particles were observed, suggesting the potential infection and replication of SARS-CoV-2 in oral tissues. Our results corroborate previous studies and confirm that the oral cavity may be a potential niche for SARS-CoV-2 infection and a potential source of transmission.

Omicron Variant Generates a Higher and More Sustained Viral Load in Nasopharynx and Saliva Than the Delta Variant of SARS-CoV-2.

The Omicron variant of SARS-CoV-2 spreads more easily than earlier variants, possibly as a result of a higher viral load in the upper respiratory tract and oral cavity. Hence, we investigated whether the Omicron variant generates a higher viral load than that of the Delta variant in saliva and nasopharynx. Both specimens were collected from 52 Omicron and 17 Delta cases at two time points one week apart and analyzed by qRT-PCR. Viral load was measured as 10 log RNA genome copies per 1000 human cells according to the WHO reference standard. We found that Omicron cases carried a higher viral load and had more sustained viral shedding compared to the Delta cases, especially in the nasopharynx.

Saliva for molecular detection of SARS-CoV-2 in pre-school and school-age children.

SARS-CoV-2 diagnosis is a cornerstone for the management of coronavirus disease 2019 (COVID-19). Numerous studies have assessed saliva performance over nasopharyngeal sampling (NPS), but data in young children are still rare. We explored saliva performance for SARS-CoV-2 detection by RT-PCR according to the time interval from initial symptoms or patient serological status. We collected 509 NPS and saliva paired samples at initial diagnosis from 166 children under 12 years of age (including 57 children under 6), 106 between 12 and 17, and 237 adults. In children under 12, overall detection rate for SARS-CoV-2 was comparable in saliva and NPS, with an overall agreement of 89.8%. Saliva sensitivity was significantly lower than that of NPS (77.1% compared to 95.8%) in pre-school and school-age children but regained 96% when considering seronegative children only. This pattern was also observed to a lesser degree in adolescents but not in adults. Sensitivity of saliva was independent of symptoms, in contrary to NPS, whose sensitivity decreased significantly in asymptomatic subjects. Performance of saliva is excellent in children under 12 at early stages of infection. This reinforces saliva as a collection method for early and unbiased SARS-CoV-2 detection and a less invasive alternative for young children.

Saliva as alternative to naso-oropharyngeal swab for SARS-CoV-2 detection by RT-qPCR: a multicenter cross-sectional diagnostic validation study.

Saliva has been demonstrated as feasible alternative to naso-oropharyngeal swab (NOS) for SARS-CoV-2 detection through reverse transcription quantitative/real-time polymerase chain reaction (RT-qPCR). This study compared the diagnostic agreement of conventional NOS, saliva with RNA extraction (SE) and saliva without RNA extraction (SalivaDirect) processing for RT-qPCR in identifying SARS-CoV-2. All techniques were also compared, as separate index tests, to a composite reference standard (CRS) where positive and negative results were defined as SARS-CoV-2 detection in either one or no sample, respectively. Of 517 paired samples, SARS-CoV-2 was detected in 150 (29.01%) NOS and 151 (29.21%) saliva specimens. The saliva-based tests were noted to have a sensitivity, specificity and accuracy (95% confidence interval) of 92.67% (87.26%, 96.28%), 97.55% (95.40%, 98.87%) and 96.13% (94.09%, 97.62%), respectively, for SE RT-qPCR and 91.33% (85.64%, 95.30%), 98.91% (97.23%, 99.70%) and 96.71% (94.79%, 98.07%), respectively, for SalivaDirect RT-qPCR compared to NOS RT-qPCR. Compared to CRS, all platforms demonstrated statistically similar diagnostic performance. These findings suggest that both conventional and streamlined saliva RT-qPCR are at least non-inferior to conventional NOS RT-qPCR in detecting SARS-CoV-2.