[Viroids : infectious non coding RNAs]. / Les viroïdes : des ARN infectieux non codants.

Viroids are the smallest non-coding infectious RNAs (between 246 and 401 nucleotides) known to be highly structured and replicate autonomously in the host plants. Although they do not encode any peptides, viroids induce visible symptoms in susceptible host plants. This article provides an overview of their physical and biological properties, the diseases they cause and their significance for the plants. The mechanisms underlying the expression of symptoms in host plants, their detection and various strategies employed for diseases prevention are also developed.

[The mechanism and techniques of vaccination]. / Le mécanisme et les techniques de la vaccination.

From the discovery of the first vaccines to the development of the latest ones, such as the one against Covid-19, research has improved the service rendered against infectious diseases by diversifying vaccination techniques to evolve responses to aggression by microorganisms.

Immobilization of recombinant lysostaphin on nanoparticle through biotin-streptavidin conjugation technology as a geometrical progressed confrontation against Staphylococcus aureus infection.

Antibiotic resistance and the colonization of resistant bacteria such as Staphylococcus aureus on surfaces, often in the form of biofilms, prolong hospitalization periods and increase mortality, thus is a significant concern for healthcare providers. To prevent biofilm formation, the inadequate concentration of using nanoparticles as antibacterial coating agents is one of the major obstacles. This study aimed to design a hypervalency TiO2 nanocomposite as a reserved base to carry a high amount of active antibacterial agents such as lysostaphin via a biotin-streptavidin-biotin bridge. The utilization of the streptavidin-biotin system could increase the abundance of lysostaphin. Lysostaphin was expressed in Escherichia coli and purified. Both recombinant lysostaphin and titanium oxide nanocomposite were conjugated with biotin and linked to a streptavidin bridge. The kinetics and activity of the enzyme were examined after each step utilizing N-acetylhexaglycine as a substrate. Physical characteristics of nanoparticles containing lysostaphin were determined using AFM, SEM, FTIR, and zeta potential. The results showed changes in size, charge, and morphology of the nanoparticles following the lysostaphin attachment. Also, the stability and kinetics of the active biological enzymes on nanoparticles were reexamined following 8 months of storage. Exploiting this approach, various biotinylated antibacterial agents could be prepared and rapidly immobilized on a nanoparticle as an active net against related infectious agents.

Open defecation and squat toilets, an overlooked risk of fecal transmission of COVID-19 and other pathogens in developing communities.

The novel coronavirus disease COVID-19 has infected over 46 million people in 219 countries and territories. Following evidence of viral loadings and infectivity of feces of infected individuals, public health authorities have suggested to take precautions on the transmission of COVID-19 via fecal-associated routes. Recent discussions on fecal transmission of COVID-19 have mainly focused on municipal sewage. Yet, a widely neglected aspect in containing the virus is that a major part of the population in developing regions do not have access to private, clean sanitary facilities. Therefore, we hypothesize that open defecation and the prevalent use of squat toilets are additional risk factors in those communities. Here, we review fecal transmission of COVID-19, the practices of open defecation, and the resultant routes of transmission of fecal pathogens. Also, we highlight the open design of common squat toilets and the potential exposure to fecal droplets and residues. We observed that at least 20 countries reporting more than 10,000 confirmed infections have 5-26% of their population practicing open defecation. We illustrate the potential routes of transmission of COVID-19 and other fecal pathogens via human feces in communities practicing open defecation. Here, poor hand hygiene, contaminated shoes and objects, mechanical vectors, and outdoor human activities can all contribute to fecal transmission. Other risk factors include squat pans with lidless designs and open flushing mechanisms, in-cubicle open waste bins, and the lack of water-sealing U-traps in squat toilets.

A biologically inspired immunization strategy for network epidemiology.

Well-known immunization strategies, based on degree centrality, betweenness centrality, or closeness centrality, either neglect the structural significance of a node or require global information about the network. We propose a biologically inspired immunization strategy that circumvents both of these problems by considering the number of links of a focal node and the way the neighbors are connected among themselves. The strategy thus measures the dependence of the neighbors on the focal node, identifying the ability of this node to spread the disease. Nodes with the highest ability in the network are the first to be immunized. To test the performance of our method, we conduct numerical simulations on several computer-generated and empirical networks, using the susceptible-infected-recovered (SIR) model. The results show that the proposed strategy largely outperforms the existing well-known strategies.

Rapid Antigen Tests during the COVID-19 Era in Korea and Their Implementation as a Detection Tool for Other Infectious Diseases.

Rapid antigen tests (RATs) are diagnostic tools developed to specifically detect a certain protein of infectious agents (viruses, bacteria, or parasites). RATs are easily accessible due to their rapidity and simplicity. During the COVID-19 pandemic, RATs have been widely used in detecting the presence of the specific SARS-CoV-2 antigen in respiratory samples from suspected individuals. Here, the authors review the application of RATs as detection tools for COVID-19, particularly in Korea, as well as for several other infectious diseases. To address these issues, we present general knowledge on the design of RATs that adopt the lateral flow immunoassay for the detection of the analyte (antigen). The authors then discuss the clinical utilization of the authorized RATs amidst the battle against the COVID-19 pandemic in Korea and their role in comparison with other detection methods. We also discuss the implementation of RATs for other, non-COVID-19 infectious diseases, the challenges that may arise during the application, the limitations of RATs as clinical detection tools, as well as the possible problem solving for those challenges to maximize the performance of RATs and avoiding any misinterpretation of the test result.

Viroids: Non-Coding Circular RNAs Able to Autonomously Replicate and Infect Higher Plants.

Viroids are a unique type of infectious agent, exclusively composed of a relatively small (246-430 nt), highly base-paired, circular, non-coding RNA. Despite the small size and non-coding nature, the more-than-thirty currently known viroid species infectious of higher plants are able to autonomously replicate and move systemically through the host, thereby inducing disease in some plants. After recalling viroid discovery back in the late 60s and early 70s of last century and discussing current hypotheses about their evolutionary origin, this article reviews our current knowledge about these peculiar infectious agents. We describe the highly base-paired viroid molecules that fold in rod-like or branched structures and viroid taxonomic classification in two families, Pospiviroidae and Avsunviroidae, likely gathering nuclear and chloroplastic viroids, respectively. We review current knowledge about viroid replication through RNA-to-RNA rolling-circle mechanisms in which host factors, notably RNA transporters, RNA polymerases, RNases, and RNA ligases, are involved. Systemic movement through the infected plant, plant-to-plant transmission and host range are also discussed. Finally, we focus on the mechanisms of viroid pathogenesis, in which RNA silencing has acquired remarkable importance, and also for the initiation of potential biotechnological applications of viroid molecules.

Basic and Applied Sciences: Technology and Immunobiological Products.

The experience in organizing the creation of innovative immunobiological drugs and vaccines is discussed-from laboratory developments to industrial technologies and the registration of finished forms of effective and safe drugs that are in demand in the domestic and foreign markets. The principles of their action rely on the latest global achievements in the field of immunobiology and vaccinology.

Therapeutic Applications of Fucoidans and their Potential to Act Against COVID-19.

In this review article, we present the updated evidence of therapeutic applications of fucoidan (a seaweed polysaccharide) and its novel potential to treat infectious diseases such as coronavirus disease (COVID-19). Because of their many biological activities, seaweeds have been identified as a rich and useful source of bioactive chemicals. Sulfated polysaccharides from the sea are considered a source of physiologically active chemicals that might be used in medication development. Antitumor, antiviral, antioxidant, antibacterial, anticoagulant, and immune-inflammatory properties have all been described for these compounds. By interfering at various phases of viral infection, marine sulfated polysaccharide has a virucidal effect. As a result, it opens the door to the development of antiviral treatments. Virus entry into host cells is an initial process, avoiding this type of entry makes any precautionary measure effective. The inhibitory action of certain marine sulfated polysaccharides against coronavirus was tested, and fucoidan, iota-carrageenan, and sea cucumber sulfated polysaccharides all showed a substantial antiviral impact. Fucoidan is one of the useful sulfated polysaccharides that has been widely studied and explored in various research. There are different sources of fucoidans, which have been used in the treatment of viral infection. Additionally, we highlight the mechanism of action of fuocidan against COVID-19. Hence, we could suggest that COVID-19 might be prevented and treated using these sulfated polysaccharides. This review thus highlights ample evidence to support the hypothesis that a large number of drugs have been developed from powerful compounds isolated from marine seaweeds.

Validation and Application of a Benchtop Cell Sorter in a Biosafety Level 3 Containment Setting.

Introduction: Fluorescent-activated cell sorting (FACS) is often the most appropriate technique to obtain pure populations of a cell type of interest for downstream analysis. However, aerosol droplets can be generated during the sort, which poses a biosafety risk when working with samples containing risk group 3 pathogens such as Francisella tularensis, Mycobacterium tuberculosis, Yersinia pestis, and severe acute respiratory syndrome coronavirus 2. For many researchers, placing the equipment required for FACS at biosafety level 3 (BSL-3) is often not possible due to expense, space, or expertise available. Methods: We performed aerosol testing as part of the biosafety evaluation of the MACSQuant Tyto, a completely closed, cartridge-based cell sorter. We also established quality control procedures to routinely evaluate instrument performance. Results: The MACSQuant Tyto does not produce aerosols as part of the sort procedure. Discussion: These data serve as guidance for other facilities with containment laboratories wishing to use the MACSQuant Tyto for cell sorting. Potential users should consult with their Institutional Biosafety Committees to perform in-house risk assessments of this equipment. Conclusion: The MACSQuant Tyto can safely be used on the benchtop to sort samples at BSL-3.

An Association of Pathogens and Biofilms with Alzheimer's Disease.

As one of the leading causes of dementia, Alzheimer's disease (AD) is a condition in which individuals experience progressive cognitive decline. Although it is known that beta-amyloid (Aß) deposits and neurofibrillary tangles (NFT) of tau fibrils are hallmark characteristics of AD, the exact causes of these pathologies are still mostly unknown. Evidence that infectious diseases may cause AD pathology has been accumulating for decades. The association between microbial pathogens and AD is widely studied, and there are noticeable correlations between some bacterial species and AD pathologies, especially spirochetes and some of the oral microbes. Borrelia burgdorferi has been seen to correlate with Aß plaques and NFTs in infected cells. Because of the evidence of spirochetes in AD patients, Treponema pallidum and other oral treponemes are speculated to be a potential cause of AD. T. pallidum has been seen to form aggregates in the brain when the disease disseminates to the brain that closely resemble the Aß plaques of AD patients. This review examines the evidence as to whether pathogens could be the cause of AD and its pathology. It offers novel speculations that treponemes may be able to induce or correlate with Alzheimer's disease.

The Impact of Bedbug (Cimex spp.) Bites on Self-Rated Health and Average Hours of Sleep per Day: A Cross-Sectional Study among Hong Kong Bedbug Victims.

Bedbugs (Cimex spp.) are a nuisance public-health pest that is on the rise globally, particularly in crowded cities such as Hong Kong. To investigate the health impacts of bedbug infestations among bedbug victims, online surveys were distributed in Hong Kong between June 2019 to July 2020. Data on sociodemographics, self-rated health, average hours of sleep per day, and details of bedbug infestation were collected. Bivariate and multivariable analysis were performed using logistic regression. The survey identified 422 bedbug victims; among them, 223 (52.9%) experienced ≥five bites in the past month; most bites occurred on the arms (n = 202, 47.8%) and legs (n = 215, 51%), and the most common reaction to bites were itchiness (n = 322, 76.3%), redness, and swelling of the skin (n = 246, 58.1%), and difficulties sleeping or restlessness (n = 125, 29.6%). Bites usually occurred during sleep (n = 230, 54.5%). For impact on daily life in the past month, most bedbug victims reported moderate to severe impact on mental and emotional health (n = 223, 52.8%) and sleeping quality (n = 239, 56.6%). Lower self-rated health (aOR < 1) was independently associated with impact on physical appearance (p = 0.008), spending money on medication or doctor consultation (p = 0.04), number of bites in the past month (p = 0.023), and irregular time of bites (p = 0.003). Lower average hours of sleep per day (aOR < 1) was independently associated with impact on mental and emotional health (p = 0.016). This study brings attention to the neglected issue of bedbug infestation by considering bedbugs as an infectious agent instead of a vector and providing empirical evidence describing its health impacts.

COVID-19 and Beyond: Safety and Design Considerations for the Development of a Mobile Biocontainment Laboratory.

Introduction: An infectious disease outbreak like the current COVID-19 pandemic can lead to particularly high infection rates in areas where diagnostic laboratory support is limited. The deployment of mobile laboratories can help to detect pathogens, monitor the presence in a population, and inform public health authorities to take measures aimed at reducing pathogen spread. Materials and Methods: Available layouts and operational descriptions of mobile laboratories were analyzed for their suitability for the envisioned purpose and to assure high standards of biosafety and biosecurity. Recent media coverage on creative solutions for the diagnostics of SARS-CoV-2 (drive-through test centers, self-swab, inverse gloveboxes to protect health care workers) from various countries were considered. Results: A minimalistic and optimized design to construct a multifunctional laboratory on the chassis of a regular-sized box truck is proposed and can serve as a blueprint to rapidly develop additional diagnostic capacities. Discussion: For acute health threats including the current COVID-19 outbreak, rapid diagnosis of infection is key to recommend measures aimed at preventing the spread of the pathogen. Laboratory layouts that are similar to the one proposed here are used in stationary setups, and mobile laboratories have been built on varying platforms (trailers, shipping containers, etc).

Etiology and prognosis of encephalitis in French Guianese children: a retrospective record-based study.

Acute encephalitis is an important cause of mortality and morbidity in children. We retrospectively identified children (≤15 years of age) admitted with suspected encephalitis at the Intensive Care Unit of the Pediatric Department of Cayenne Hospital between January 2007 and December 2018. A total of 30 children with acute encephalitis were identified. The incidence rate varied from 0 to 10.40 cases/100000 children under 15 years. Proven encephalitis was diagnosed in 73% of patients. Nine cases of acute disseminated encephalomyelitis were diagnosed. The causes of infection (44%) were Haemophilus influenzae, followed by Cryptococcus spp and Varicella Zoster Virus. Four children (13%) died: one case of Streptococcus pneumoniae, one of Haemophilus influenzae, one of Mycobacterium tuberculosis and one with no identified cause. Seventeen percent of children had moderate to severe neurological sequelae. The only factor associated with poor outcome was young age at the time of hospitalization (p = 0.03). Conclusion: This study highlights both vaccine-preventable pathogens and acute disseminated encephalomyelitis as the leading causes of childhood encephalitis in French Guiana.

Determination of the Infectious Agent of Translucent Post-Larva Disease (TPD) in Penaeus vannamei.

A new emerging disease called "translucent post-larvae disease" (TPD) or "glass post-larvae disease" (GPD) of Penaeus vannamei, characterized by pale or colorless hepatopancreas and digestive tract, has become an urgent threat to the shrimp farming industry. Following this clue that treatment of an antibacterial agent could alleviate the disease, systematic investigation of the potential infectious agent of TPD was conducted using bacterial identification and artificial challenge tests to fulfill Koch's postulates. A dominant bacterial isolate, Vp-JS20200428004-2, from the moribund individuals was isolated and identified as Vibrio parahaemolyticus based on multi-locus sequence analysis. However, Vp-JS20200428004-2 differed from the V. parahaemolyticus that caused typical acute hepatopancreatic necrosis disease. Immersion challenge tests revealed that Vp-JS20200428004-2 could cause 100% mortality within 40 h at a dose of 1.83 × 106 CFU/mL, and experimental infected shrimp showed similar clinical signs of TPD. The Vp-JS20200428004-2 could be re-isolated and identified from the experimental infected individuals. Moreover, histopathological analysis of diseased samples indicated that Vp-JS20200428004-2 caused severe necrosis and sloughing of epithelial cells of the hepatopancreas and midgut in shrimp individuals both naturally and experimentally infected. Our present results indicated that Vp-JS20200428004-2 is a highly virulent infectious agent associated with the TPD and deserves further attention.

[A virologist visits the Papuan anthropophagists]. / Un virologue chez les anthropophages papous.

In the 1950's, the American Carleton Gajdusek (1923-2008) was able to find the cause for kuru, a systematically fatal neurological disease, observed mainly on the Western Highlands of New Guinea. While living for a long period with the local indigenous population and studying their customs, he evidenced the infectious origin of this pathology and its transmission mechanism, cannibalism. He also demonstrated the transmissible nature of the agent of Creutzfeldt-Jakob. His works opened an important prospective field of research in neuroscience. A Nobel prize rewarded this outstanding scientific and human adventure.

An Evaluation of Monitoring Surveys of the Quarantine Bacterium Xylella Fastidiosa Performed in Containment and Buffer Areas of Apulia, Southern Italy.

Introduction: Xylella fastidiosa is a quarantine phytopathogen for the European Plant Protection Organization and currently infects olive trees in the Apulia region (southern Italy). Upon the Implementing Decision of the European Union 2016/764 of May 12, 2016, extensive monitoring surveys were performed on approximately 190 000 ha to ascertain the possible occurrence of X. fastidiosa. Objectives: The primary objectives of the analysis were to start to collect epidemiological data on X. fastidiosa occurrence in areas far from the initial outbreaks and discuss the results of the pathogen detection. Methods: A total of 220 279 olive trees were inspected. Basic information on farm and trees management was obtained. A total of 13 706 olive trees were analyzed through serological and molecular techniques to verify the possible occurrence of the bacterium. Results: The cultivars "Nociara," "Cima di Melfi," and "Cellina di Nardò" showed the highest occurrence of decline symptoms. Tree age appears to be related to the incidence of decline symptoms. Olive trees growing in well-managed soils showed fewer symptoms than trees cultivated in farms where such agronomic techniques are not regularly performed. X. fastidiosa was detected in 2078 samples taken from symptomatic trees and 1653 samples obtained from asymptomatic trees. In 3300 samples taken from symptomatic trees, the bacterium was not detected. Conclusions: Implementation and utilization of reliable in situ detection techniques could increase the number of sampled trees in each plot, thus allowing a more extensive and robust assessment of X. fastidiosa-infected plants in areas where the pathogen inoculums are still low.

Indirect Effects Explain the Role of Parasites in Ecosystems.

Parasites are increasingly recognized as integral members of ecological communities, but their ecological effects remain less clear. Here, I propose that, to uncover the unique role of parasites, we must understand their indirect effects, which differ in important ways from those caused by predators. Similar to predators, parasites can cause density-mediated indirect effects (DMIEs) through their consumptive effects, and trait-mediated indirect effects (TMIEs) through their nonconsumptive effects; however, because they can consume a host without killing it, parasites can also trigger TMIEs through their consumptive effects. I consider the relative importance of each parasite-induced indirect interaction type and demonstrate their population-, community-, and ecosystem-level consequences. This paper contributes to recent efforts to unite predator-prey and parasite-host theory under a general consumer-resource framework.

Inactivation of Viable Surrogates for the Select Agents Virulent Newcastle Disease Virus and Highly Pathogenic Avian Influenza Virus Using Either Commercial Lysis Buffer or Heat.

Introduction: Federal Select Agent Program regulations require laboratories to document a validated procedure for inactivating select agents prior to movement outside registered space. Avian influenza viruses and virulent Newcastle disease virus (vNDV) are cultured in chicken amnio-allantoic fluid (AAF), but the efficacy of commercial lysis buffers to inactivate viruses in protein-rich media has not been documented. Objectives: We assesses the efficacy of MagMAX™ lysis buffer for inactivating highly pathogenic avian influenza virus (HPAIV) and vNDV in chicken AAF and confirm the inactivation of avian influenza in serum using heat. Methods: Low pathogenic avian influenza virus (LPAIV) and avian paramyxovirus subtype-1 (APMV-1) were incubated with lysis buffer and tested for viability. Known viable LPAIV and APMV-1 RNA was extracted from AAF using MagMAX™-96 AI/ND Viral RNA Isolation kit, and the eluate was tested for remaining infectious agent. Finally, inactivation of LPAIV in serum was examined over 3 combinations of temperature and incubation time. Results: MagMAX™ lysis buffer inactivated both LPAIV and APMV-1 in AAF when incubated for 30 minutes at room temperature. The full extraction process eliminated viable virus from the final RNA eluate. LPAIV in serum heated to 70°C for 30 minutes was rendered noninfectious. Conclusion: The ability of a diagnostic laboratory to move samples from one space to another is critical to maintaining biosecurity as well as efficient laboratory workflow. Our study demonstrates a method to ensure the inactivation of viable avian influenza and avian paramyxoviruses in AAF, RNA eluate, and viable avian influenza virus in sera.

Vacinas passado e futuro ­ Reflexões para discussão / The past and future of vaccines ­ Reflections for discussion

Neste artigo de opinião, apresento uma breve história do desenvolvimento de vacinas, comentando sobre as formas clássicas de produção de vacinas utilizando o próprio agente infeccioso. Em seguida, abordo as vacinas virais, discutindo seus benefícios e dificuldades e a questão dos sorotipos virais, bem como as vacinas bacterianas e seu relativo sucesso. Apresento nossos estudos sobre doença cardíaca reumática e o desenvolvimento de uma vacina contra infecções estreptocócicas. Também discuto plataformas vacinais, especialmente os sucessos alcançados com vacinas de vetores virais não replicantes e, acima de tudo, o grande êxito das vacinas de RNA mensageiro (mRNA). As vacinas de mRNA tornaram-se possíveis somente após os avanços obtidos com a substituição de nucleotídeos que reduziam a ação da imunidade inata. Serão todas as vacinas desenvolvidas a partir de mRNA no futuro? Em seguida, abordo a questão das vias de administração de vacinas, seja por via subcutânea, intradérmica, intramuscular ou nasal. Exponho dados do meu laboratório sobre o desenvolvimento de uma vacina de instilação nasal que induziu uma resposta de proteção da mucosa, prevenindo a infecção e, consequentemente, a transmissão do SARS-CoV-2. Posteriormente, discuto quais vacinas futuras poderiam ser desenvolvidas para além das doenças infecciosas agudas. Por fim, discuto as vantagens do desenvolvimento de vacinas seguras, eficazes e de uso múltiplo, bem como a forma de torná-las acessíveis à população mundial, promovendo a equidade em saúde.

In this opinion article, I provide a brief history of vaccine development, commenting on the classic ways of producing vaccines using the infectious agent itself. I address viral vaccines, discussing their benefits and challenges and the issue of viral serotypes, as well as bacterial vaccines and their relative success. I present our studies on rheumatic heart disease and the development of a vaccine against streptococcal infection. I also discuss vaccine platforms, highlighting the success achieved with non-replicating viral vector-based vaccines and, especially, with messenger RNA (mRNA) vaccines. mRNA vaccines only became possible after the advances provided by the replacement of nucleotides that reduced the action of the innate immune system. Will all vaccines be made from mRNA in the future? Then, I address the issue of vaccine administration routes, whether subcutaneously, intradermally, intramuscularly, or intranasal. I present data from my laboratory on the development of an intranasal vaccine that induced a protective mucosal response, preventing infection and, consequently, the transmission of SARSCoV- 2. I discuss which future vaccines could be developed beyond acute infectious diseases. Finally, I discuss the advantages of developing safe, effective, multiple-use vaccines and how to make them accessible worldwide by promoting health equity.