The pathogenesis of measles

Exploring landscape of measles vaccination coverage: A step towards measles elimination goal in India

INTRODUCTION

Measles remains a critical public health concern causing significant morbidity and mortality globally. Despite the success of measles vaccination programs, challenges persist, particularly in India. This study investigates dose-wise measles vaccination coverage and explores gaps in immunization focusing on zero-dose, one-dose, and two-dose coverage among children aged 24-35 months.

DATA SOURCES AND METHODOLOGY

The National Family Health Survey 2019-21 (NFHS-5) served as the data source and the study analyzed information from 43,864 children aged 24-35 months. Sociodemographic variables such as birth order, wealth quintile, gender, social group, religion, residence, mother education, delivery-related factors, and media exposure were considered. Statistical analysis involved weighted estimates, chi-square tests, and multivariate multinomial logistic regression.

RESULTS

The study revealed that challenges persist in achieving optimal measles vaccination coverage. Analysis by sociodemographic factors highlighted disparities in coverage, with variations in zero dose prevalence across states and districts. The percentage of zero-dose children was significantly higher, with 11.5% of children in India remaining to receive any measles vaccination. Factors influencing vaccine coverage include birth order, age, wealth quintile, social group, religion, residence, maternal education, place of delivery, media exposure, and mode of delivery. The findings from the spatial analysis show the clustering of zero-dose children is high in the northeastern states of India.

DISCUSSION

Measles zero-dose children pose a significant obstacle to achieving elimination goals. Spatial analysis identifies clusters of unvaccinated populations guiding targeted interventions. The study aligns with global initiatives such as the Immunization Agenda 2030 emphasizing equitable vaccine access and discusses how India can tailor its strategies to achieve the goal. Lessons from polio eradication efforts inform strategies for measles elimination, stressing the importance of high-quality data and surveillance. The study underscores the urgency of addressing last-mile measles vaccination gaps in India. Spatially targeted interventions informed by sociodemographic factors can enhance immunization coverage. Achieving measles elimination requires sustained efforts and leveraging lessons from successful vaccination campaigns. The study findings have the potential to contribute to informed decision-making, supporting India's roadmap for the measles and rubella elimination goal.

Vaccination in post-tuberculosis lung disease management: A review of the evidence

INTRODUCTION AND OBJECTIVES

Post-tuberculosis lung disease (PTLD), as other chronic respiratory disorders, may have infectious complications; some of them can be prevented with vaccinations. So far, no document has discussed the potential role of vaccination in PTLD. Therefore, the objective of this review was to describe vaccination recommendations to prevent infections potentially capable of complicating PTLD.

MATERIALS AND METHODS

A non-systematic review of the literature was conducted. The following keywords were used: tuberculosis, vaccination, vaccines and PTLD. PubMed/MEDLINE and Embase were used as the search engine, focusing on English-language literature only.

RESULTS

We identified 9 vaccines potentially useful in PTLD. Influenza, pneumococcal and anti-COVID-19 vaccinations should be recommended. Patients with PTLD can also benefit from vaccination against shingles. Vaccination against pertussis is mainly relevant during childhood. Diphtheria, tetanus and measles vaccination are recommended for general population and should be considered in patients with PTLD not previously vaccinated. Tdap (Tetanus, diphtheria, and pertussis) booster should be repeated in every adult every ten years. Vaccination against BCG retains its importance during early childhood in countries where TB is endemic.

CONCLUSIONS

Vaccination deserves to be considered among the strategies to prevent and/or mitigate PTLD complications. Further evidence is necessary to better understand which vaccines have the greatest impact and cost-benefit.

A protective measles virus-derived vaccine inducing long-lasting immune responses against influenza A virus H7N9

A novel Influenza A virus (subtype H7N9) emerged in spring 2013 and caused considerable mortality in zoonotically infected patients. To be prepared for potential pandemics, broadly effective and safe vaccines are crucial. Recombinant measles virus (MeV) encoding antigens of foreign pathogens constitutes a promising vector platform to generate novel vaccines. To characterize the efficacy of H7N9 antigens in a prototypic vaccine platform technology, we generated MeVs encoding either neuraminidase (N9) or hemagglutinin (H7). Moraten vaccine strain-derived vaccine candidates were rescued; they replicated with efficiency comparable to that of the measles vaccine, robustly expressed H7 and N9, and were genetically stable over 10 passages. Immunization of MeV-susceptible mice triggered the production of antibodies against H7 and N9, including hemagglutination-inhibiting and neutralizing antibodies induced by MV_vac2-H7(P) and neuraminidase-inhibiting antibodies by MV_vac2-N9(P). Vaccinated mice also developed long-lasting H7- and N9-specific T cells. Both MV_vac2-H7(P) and MV_vac2-N9(P)-vaccinated mice were protected from lethal H7N9 challenge.

Host–Pathogen Interactions Influencing Zoonotic Spillover Potential and Transmission in Humans

Emerging infectious diseases of zoonotic origin are an ever-increasing public health risk and economic burden. The factors that determine if and when an animal virus is able to spill over into the human population with sufficient success to achieve ongoing transmission in humans are complex and dynamic. We are currently unable to fully predict which pathogens may appear in humans, where and with what impact. In this review, we highlight current knowledge of the key host–pathogen interactions known to influence zoonotic spillover potential and transmission in humans, with a particular focus on two important human viruses of zoonotic origin, the Nipah virus and the Ebola virus. Namely, key factors determining spillover potential include cellular and tissue tropism, as well as the virulence and pathogenic characteristics of the pathogen and the capacity of the pathogen to adapt and evolve within a novel host environment. We also detail our emerging understanding of the importance of steric hindrance of host cell factors by viral proteins using a “flytrap”-type mechanism of protein amyloidogenesis that could be crucial in developing future antiviral therapies against emerging pathogens. Finally, we discuss strategies to prepare for and to reduce the frequency of zoonotic spillover occurrences in order to minimize the risk of new outbreaks.

Pathogenesis of wild-type- and vaccine-based recombinant peste des petits ruminants virus (PPRV) expressing EGFP in experimentally infected domestic goats

Peste des petits ruminants virus (PPRV) is a highly contagious morbillivirus related to measles and canine distemper virus, mostly affecting small ruminants. The corresponding PPR disease has a high clinical impact in goats and is characterized by fever, oral and nasal erosions, diarrhoea and pneumonia. In addition, massive infection of lymphoid tissues causes lymphopaenia and immune suppression. This results in increased susceptibility to secondary bacterial infections, explaining the observed high mortality in some outbreaks. We studied the pathogenesis of PPR by experimental inoculation of Dutch domestic goats with a recombinant virulent PPRV strain modified to express EGFP and compared it to an EGFP-expressing vaccine strain of PPRV. After intratracheal inoculation with virulent PPRV, animals developed fever, viraemia and leucopaenia, and shed virus from the respiratory and gastro-intestinal tracts. Macroscopic evaluation of fluorescence at the peak of infection 7 days post-inoculation (dpi) showed prominent PPRV infection of the respiratory tract, lymphoid tissues, gastro-intestinal tract, mucosae and skin. Flow cytometry of PBMCs collected over time demonstrated a cell-associated viraemia mediated by infected lymphocytes. At 14 dpi, pathognomonic zebra stripes were detected in the mucosa of the large intestine. In contrast, vaccine strain-inoculated goats remained largely macroscopically fluorescence negative and did not present clinical signs. A low-level viraemia was detected by flow cytometry, but at necropsy no histological lesions were observed. Animals from both groups seroconverted as early as 7 dpi and sera efficiently neutralized virulent PPRV in vitro. Combined, this work presents a study of the pathogenesis of wild type- and vaccine-based PPRV in its natural host. This study shows the strength of recombinant EGFP-expressing viruses in fluorescence-guided pathogenesis studies.

The Reemergence of Measles

OBJECTIVES

Present-day pathologists may be unfamiliar with the histopathologic features of measles, which is a reemerging disease. Awareness of these features may enable early diagnosis of measles in unsuspected cases, including those with an atypical presentation. Using archived tissue samples from historic patients, a unique source of histopathologic information about measles and other reemerging infectious diseases, we performed a comprehensive analysis of the histopathologic features of measles seen in commonly infected tissues during prodrome, active, and late phases of the disease.

METHODS

Subspecialty pathologists analyzed H&E-stained slides of specimens from 89 patients accessioned from 1919 to 1998 and correlated the histopathologic findings with clinical data.

RESULTS

Measles caused acute and chronic histopathologic changes, especially in the respiratory, lymphoid (including appendix and tonsils), and central nervous systems. Bacterial infections in lung and other organs contributed significantly to adverse outcomes, especially in immunocompromised patients.

CONCLUSIONS

Certain histopathologic features, especially Warthin-Finkeldey cells and multinucleated giant cells without inclusions, allow pathologists to diagnose or suggest the diagnosis of measles in unsuspected cases.

Contextualizing Wastewater-Based surveillance in the COVID-19 vaccination era

SARS-CoV-2 wastewater-based surveillance (WBS) offers a tool for cost-effective oversight of a population's infections. In the past two years, WBS has proven to be crucial for managing the pandemic across different geographical regions. However, the changing context of the pandemic due to high levels of COVID-19 vaccination warrants a closer examination of its implication towards SARS-CoV-2 WBS. Two main questions were raised: 1) Does vaccination cause shedding of viral signatures without infection? 2) Does vaccination affect the relationship between wastewater and clinical data? To answer, we review historical reports of shedding from viral vaccines in use prior to the COVID-19 pandemic including for polio, rotavirus, influenza and measles infection and provide a perspective on the implications of different COVID-19 vaccination strategies with regard to the potential shedding of viral signatures into the sewershed. Additionally, we reviewed studies that looked into the relationship between wastewater and clinical data and how vaccination campaigns could have affected the relationship. Finally, analyzing wastewater and clinical data from the Netherlands, we observed changes in the relationship concomitant with increasing vaccination coverage and switches in dominant variants of concern. First, that no vaccine-derived shedding is expected from the current commercial pipeline of COVID-19 vaccines that may confound interpretation of WBS data. Secondly, that breakthrough infections from vaccinated individuals contribute significantly to wastewater signals and must be interpreted in light of the changing dynamics of shedding from new variants of concern.

Measles outbreak in Zimbabwe: An urgent rising concern

Introduction

Measles, one of the most common infections in the world, accounts for more than over 100.000 deaths every year. Measles outbreaks are still ravaging the African continent, and the 2010 Measles outbreak in Zimbabwe is one to be noted, where more than 7754 infections and 517 deaths were reported, ultimately leading to the UN initiation of the vaccination program. COVID-19 could have been delaying the vaccination process in Africa. This article aims to shed the light on the current Measles outbreak in Zimbabwe and how global health organizations are taking measures to fight off this outbreak.

Methodology

Data was collected from online databases PubMed, Science Direct, and the Lancet, as well as news and conferences and press releases on the current measles outbreak. All articles and news related to the measles outbreak in Zimbabwe were taken into consideration.

Results

A measles outbreak was reported earlier in August of 2022, with more than 2000 confirmed cases out of which 157 were reported dead. Since the outbreak this year, cases of measles in Zimbabwe have been rapidly growing. The government in Zimbabwe started a massive vaccination campaign for children in and near the areas where the outbreak is present. Traditional and faith leaders are involved in the campaigns to encourage the public to volunteer to be vaccinated.

Conclusion

Efforts to control the measles outbreak in Zimbabwe are being mitigated by the government as well as the WHO and other global health organizations. With many people refusing the vaccination, this outbreak might not see an end, and more cases, as well as deaths, will increase by the end of the year.

Measles Epidemiology and Viral Nucleoprotein Gene Evolution in Shandong Province, China

Measles, caused by measles virus (MeV), has not been eradicated in many regions and countries, threatening human health. Thus, it is beneficial for measles elimination to understand measles epidemiology and molecular evolution of key viral genes, such as nucleoprotein (N) gene. Based on public data, measles epidemiological information and MeV N gene sequences reported in Shandong Province, China were comprehensively collected and systematically analyzed. The results showed a positive correlation between population density and measles incidence (r = + 0.31), while negative correlations were found between measles incidence and healthcare condition (r = - 0.21) as well as average routine vaccination rate (r = - 0.11). Additionally, the predominant lineage of MeV in Shandong was formed by genotype H1 strains, and the time of the most recent common ancestor of the N gene of MeV genotype H1 in Shandong traced back to 1987 (95% highest posterior density, 1984-1990) with relatively rapid evolution (mean rate, 1.267×10^-3 substitutions/site/year). The genetic diversity of MeV N gene increased with the substantial emergence of major divergent clades of genotype H1 before 2005 and then remained relatively stable. In summary, these findings provided a significant insight into the measles elimination. This article is protected by copyright. All rights reserved.

Overcoming the Barrier of the Respiratory Epithelium during Canine Distemper Virus Infection

Canine distemper virus (CDV) is a highly contagious pathogen and is known to enter the host via the respiratory tract and disseminate to various organs. Current hypotheses speculate that CDV uses the homologous cellular receptors of measles virus (MeV), SLAM and nectin-4, to initiate the infection process. For validation, here, we established the well-differentiated air-liquid interface (ALI) culture model from primary canine tracheal airway epithelial cells. By applying the green fluorescent protein (GFP)-expressing CDV vaccine strain and recombinant wild-type viruses, we show that cell-free virus infects the airway epithelium mainly via the paracellular route and only after prior disruption of tight junctions by pretreatment with EGTA; this infection was related to nectin-4 but not to SLAM. Remarkably, when CDV-preinfected DH82 cells were cocultured on the basolateral side of canine ALI cultures grown on filter supports with a 1.0-μm pore size, cell-associated CDV could be transmitted via cell-to-cell contact from immunocytes to airway epithelial cultures. Finally, we observed that canine ALI cultures formed syncytia and started to release cell-free infectious viral particles from the apical surface following treatment with an inhibitor of the JAK/STAT signaling pathway (ruxolitinib). Our findings show that CDV can overcome the epithelial barrier through different strategies, including infection via immunocyte-mediated transmission and direct infection via the paracellular route when tight junctions are disrupted. Our established model can be adapted to other animals for studying the transmission routes and the pathogenicity of other morbilliviruses. IMPORTANCE Canine distemper virus (CDV) is not only an important pathogen of carnivores, but it also serves as a model virus for analyzing measles virus pathogenesis. To get a better picture of the different stages of infection, we used air-liquid interface cultures to analyze the infection of well-differentiated airway epithelial cells by CDV. Applying a coculture approach with DH82 cells, we demonstrated that cell-mediated infection from the basolateral side of well-differentiated epithelial cells is more efficient than infection via cell-free virus. In fact, free virus was unable to infect intact polarized cells. When tight junctions were interrupted by treatment with EGTA, cells became susceptible to infection, with nectin-4 serving as a receptor. Another interesting feature of CDV infection is that infection of well-differentiated airway epithelial cells does not result in virus egress. Cell-free virions are released from the cells only in the presence of an inhibitor of the JAK/STAT signaling pathway. Our results provide new insights into how CDV can overcome the barrier of the airway epithelium and reveal similarities and some dissimilarities compared to measles virus.

The Roles of Amphibian (Xenopus laevis) Macrophages during Chronic Frog Virus 3 Infections

Infections by Frog Virus 3 (FV3) and other ranavirus genus members are significantly contributing to global amphibian decline. The Xenopus laevis frog is an ideal research platform upon which to study the roles of distinct frog leukocyte populations during FV3 infections. Frog macrophages (MΦs) are integrally involved during FV3 infection, as they facilitate viral dissemination and persistence but also participate in immune defense against this pathogen. In turn, MΦ differentiation and functionality depend on the colony-stimulating factor-1 receptor (CSF-1R), which is ligated by CSF-1 and iterleukin-34 (IL-34) cytokines. Our past work indicated that X. laevis CSF-1 and IL-34 give rise to morphologically and functionally distinct frog MΦ subsets, and that these CSF-1- and IL-34-MΦs respectively confer susceptibility and antiviral resistance to FV3. Because FV3 targets the frog kidneys and establishes chronic infections therein, presently we examined the roles of the frog CSF-1- and IL-34-MΦs in seeding and maintaining these chronic kidney infections. Our findings indicate that the frog CSF-1-MΦs result in more prominent kidney FV3 infections, which develop into greater reservoirs of lingering FV3 marked by infiltrating leukocytes, fibrosis, and overall immunosuppressive states. Moreover, the antiviral effects of IL-34-MΦs are short-lived and are lost as FV3 infections progress.

Inhibition of Measles Viral Fusion Is Enhanced by Targeting Multiple Domains of the Fusion Protein

Measles virus (MeV) infection remains a significant public health threat despite ongoing global efforts to increase vaccine coverage. As eradication of MeV stalls, and vulnerable populations expand, effective antivirals against MeV are in high demand. Here, we describe the development of an antiviral peptide that targets the MeV fusion (F) protein. This antiviral peptide construct is composed of a carbobenzoxy-d-Phe-l-Phe-Gly (fusion inhibitor peptide; FIP) conjugated to a lipidated MeV F C-terminal heptad repeat (HRC) domain derivative. Initial in vitro testing showed high antiviral potency and specific targeting of MeV F-associated cell plasma membranes, with minimal cytotoxicity. The FIP and HRC-derived peptide conjugates showed synergistic antiviral activities when administered individually. However, their chemical conjugation resulted in markedly increased antiviral potency. In vitro mechanistic experiments revealed that the FIP-HRC lipid conjugate exerted its antiviral activity predominantly through stabilization of the prefusion F, while HRC-derived peptides alone act predominantly on the F protein after its activation. Coupled with in vivo experiments showing effective prevention of MeV infection in cotton rats, FIP-HRC lipid conjugates show promise as potential MeV antivirals via specific targeting and stabilization of the prefusion MeV F structure.

Measles virus exits human airway epithelia within dislodged metabolically active infectious centers

Measles virus (MeV) is the most contagious human virus. Unlike most respiratory viruses, MeV does not directly infect epithelial cells upon entry in a new host. MeV traverses the epithelium within immune cells that carry it to lymphatic organs where amplification occurs. Infected immune cells then synchronously deliver large amounts of virus to the airways. However, our understanding of MeV replication in airway epithelia is limited. To model it, we use well-differentiated primary cultures of human airway epithelial cells (HAE) from lung donors. In HAE, MeV spreads directly cell-to-cell forming infectious centers that grow for ~3–5 days, are stable for a few days, and then disappear. Transepithelial electrical resistance remains intact during the entire course of HAE infection, thus we hypothesized that MeV infectious centers may dislodge while epithelial function is preserved. After documenting by confocal microscopy that infectious centers progressively detach from HAE, we recovered apical washes and separated cell-associated from cell-free virus by centrifugation. Virus titers were about 10 times higher in the cell-associated fraction than in the supernatant. In dislodged infectious centers, ciliary beating persisted, and apoptotic markers were not readily detected, suggesting that they retain functional metabolism. Cell-associated MeV infected primary human monocyte-derived macrophages, which models the first stage of infection in a new host. Single-cell RNA sequencing identified wound healing, cell growth, and cell differentiation as biological processes relevant for infectious center dislodging. 5-ethynyl-2’-deoxyuridine (EdU) staining located proliferating cells underneath infectious centers. Thus, cells located below infectious centers divide and differentiate to repair the dislodged infected epithelial patch. As an extension of these studies, we postulate that expulsion of infectious centers through coughing and sneezing could contribute to MeV’s strikingly high reproductive number by allowing the virus to survive longer in the environment and by delivering a high infectious dose to the next host.

Measles virus (MeV) is a respiratory pathogen that infects millions worldwide each year. Although sometimes mischaracterized as an innocuous childhood disease, measles remains a leading cause of death for children under five. MeV is the most contagious human virus and requires vaccination rates above 90% to maintain herd immunity. Global decreases in vaccination rates over the past ten years contributed to recent, widespread MeV outbreaks. We uncover here a novel mechanism by which MeV exits the human airways that may explain why it is much more contagious than other viruses. We document that infected cells containing cell-associated virus detach en masse from the airway epithelial sheet. These dislodged infectious centers are metabolically active and can transmit infection to primary human monocyte-derived macrophages via cell-cell contact as efficiently as cell-free virus particles. Thus, cell-associated MeV could spread host-to-host and is a potentially vital strategy for efficient respiratory virus transmission.

Sars-Cov-2 virus and vaccination; biological and statistical framework

Introduction

The Development of the SARS-CoV-2 virus vaccine and its update on an ongoing pandemic is the first subject of the world health agenda.

Areas covered

First, we will scrutinize the biological features of the measles virus (MV), variola virus (smallpox virus), influenza virus, and their vaccines to compare them with the SARS-CoV-2 virus and vaccine. Next, we will discuss the statistical details of measuring the effectiveness of an improved vaccine.

Expert opinion

Amidst the pandemic, we ought to acknowledge our prior experiences with respiratory viruses and vaccines. In the planning stage of observational Phase-III vaccine effectiveness studies, the sample size, sampling method, statistical model, and selection of variables are crucial in obtaining high-quality and valid results.

Dual RNA-Seq Enables Full-Genome Assembly of Measles Virus and Characterization of Host-Pathogen Interactions

Measles virus (MeV) has a negative-sense 15 kb long RNA genome, which is generally conserved. Recent advances in high-throughput sequencing (HTS) and Dual RNA-seq allow the analysis of viral RNA genomes and the discovery of viral infection biomarkers, via the simultaneous characterization of the host transcriptome. However, these host–pathogen interactions remain largely unexplored in MeV infections. We performed untargeted Dual RNA-seq in 6 pharyngeal and 6 peripheral blood mononuclear cell (PBMCs) specimens from patients with MeV infection, as confirmed via routine real-time PCR testing. Following optimised DNase treatment of total nucleic acids, we used the pharyngeal samples to build poly-A-enriched NGS libraries. We reconstructed the viral genomes using the pharyngeal datasets and we further conducted differential expression, gene-ontology and pathways enrichment analysis to compare both the pharyngeal and the peripheral blood transcriptomes of the MeV-infected patients vs. control groups of healthy individuals. We obtained 6 MeV genotype-B3 full-genome sequences. We minutely analyzed the transcriptome of the MeV-infected pharyngeal epithelium, detecting all known viral infection biomarkers, but also revealing a functional cluster of local antiviral and inflammatory immune responses, which differ substantially from those observed in the PBMCs transcriptome. The application of Dual RNA-seq technologies in MeV-infected patients can potentially provide valuable information on the virus genome structure and the cellular innate immune responses and drive the discovery of new targets for antiviral therapy.

TLR5-Mediated Reactivation of Quiescent Ranavirus FV3 in Xenopus Peritoneal Macrophages

Ranaviruses such as frog virus 3 (FV3) are large double-stranded DNA (dsDNA) viruses causing emerging infectious diseases leading to extensive morbidity and mortality of amphibians and other ectothermic vertebrates worldwide. Among the hosts of FV3, some are highly susceptible, whereas others are resistant and asymptomatic carriers that can take part in disseminating the infectious virus. To date, the mechanisms involved in the processes of FV3 viral persistence associated with subclinical infection transitioning to lethal outbreaks remain unknown. Investigation in Xenopus laevis has revealed that in asymptomatic FV3 carrier animals, inflammation induced by heat-killed (HK) Escherichia coli stimulation can provoke the relapse of active infection. Since Toll-like receptors (TLRs) are critical for recognizing microbial molecular patterns, we investigated their possible involvement in inflammation-induced FV3 reactivation. Among the 10 different TLRs screened for changes in expression levels following FV3 infection and HK E. coli stimulation, only TLR5 and TLR22, both of which recognize bacterial products, showed differential expression, and only the TLR5 ligand flagellin was able to induce FV3 reactivation similarly to HK E. coli Furthermore, only the TLR5 ligand flagellin induced FV3 reactivation in peritoneal macrophages both in vitro and in vivo These data indicate that the TLR5 signaling pathway can trigger FV3 reactivation and suggest a role of secondary bacterial infections or microbiome alterations (stress or pollution) in initiating sudden deadly disease outbreaks in amphibian populations with detectable persistent asymptomatic ranavirus.IMPORTANCE This study in the amphibian Xenopus laevis provides new evidence of the critical role of macrophages in the persistence of ranaviruses in a quiescent state as well as in the reactivation of these pathogens into a virulent infection. Among the multiple microbial sensors expressed by macrophages, our data underscore the preponderant involvement of TLR5 stimulation in triggering the reactivation of quiescent FV3 in resident peritoneal macrophages, unveiling a mechanistic connection between the reactivation of persisting ranavirus infection and bacterial coinfection. This suggests a role for secondary bacterial infections or microbiome alterations (stress or pollution) in initiating sudden deadly disease outbreaks in amphibian populations with detectable persistent asymptomatic ranavirus.

Relationship between influenza and dengue outbreaks, and subsequent bacterial sepsis in French Guiana: A time series analysis

Background: Influenza has been shown to increase the risk for severe bacterial infection, in the tropics the seasonality of influenza epidemics is less marked, and this may not be the case. Dengue is often followed by prolonged asthenia and some physicians hypothesized increased susceptibility to infections based on anecdotal observations.

Design and Methods: Time series of influenza and dengue surveillance were confronted bacterial sepsis admissions to test the hypotheses. Monthly surveillance data on influenza and dengue and aggregated sepsis data in Cayenne hospital were matched between 24/10/2007 and 27/09/2016. An ARIMA (1,0,1) model was used.

Results The series of the number of monthly cases of sepsis was positively associated with the monthly number of cases of influenza at time t (β=0.001, p=0.0359). Forecasts were imperfectly correlated with sepsis since influenza is not the only risk factor for sepsis. None of the ARIMA models showed a significant link between the dengue series and the sepsis series.

Conclusions: There was thus no link between dengue epidemics and sepsis, but it was estimated that for every 1,000 cases of flu there was one additional case of sepsis. In this tropical setting, influenza was highly seasonal, and improved vaccination coverage could have benefits on sepsis.

Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles

Measles is a disease caused by the highly infectious measles virus (MeV) that results in both viremia and lymphopenia. Lymphocyte counts recover shortly after the disappearance of measles-associated rash, but immunosuppression can persist for months to years after infection, resulting in increased incidence of secondary infections. Animal models and in vitro studies have proposed various immunological factors underlying this prolonged immune impairment, but the precise mechanisms operating in humans are unknown. Using B cell receptor (BCR) sequencing of human peripheral blood lymphocytes before and after MeV infection, we identified two immunological consequences from measles underlying immunosuppression: (i) incomplete reconstitution of the naïve B cell pool leading to immunological immaturity and (ii) compromised immune memory to previously encountered pathogens due to depletion of previously expanded B memory clones. Using a surrogate model of measles in ferrets, we investigated the clinical consequences of morbillivirus infection and demonstrated a depletion of vaccine-acquired immunity to influenza virus, leading to a compromised immune recall response and increased disease severity after secondary influenza virus challenge. Our results show that MeV infection causes changes in naïve and memory B lymphocyte diversity that persist after the resolution of clinical disease and thus contribute to compromised immunity to previous infections or vaccinations. This work highlights the importance of MeV vaccination not only for the control of measles but also for the maintenance of herd immunity to other pathogens, which can be compromised after MeV infection.

Immunopathogenesis of COVID-19 and early immunomodulators

The novel coronavirus disease 2019 (COVID-19) is spreading globally. Although its etiologic agent is discovered as severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), there are many unsolved issues in COVID-19 and other infectious diseases. The causes of different clinical phenotypes and incubation periods among individuals, species specificity, and cytokine storm with lymphopenia as well as the mechanism of damage to organ cells are unknown. It has been suggested that in viral pneumonia, virus itself is not a direct cause of acute lung injury; rather, aberrant immune reactions of the host to the insults from viral infection are responsible. According to its epidemiological and clinical characteristics, SARS-CoV-2 may be a virus with low virulence in nature that has adapted to the human species. Current immunological concepts have limited ability to explain such unsolved issues, and a presumed immunopathogenesis of COVID-19 is presented under the proteinhomeostasis-system hypothesis. Every disease, including COVID-19, has etiological substances controlled by the host immune system according to size and biochemical properties. Patients with severe pneumonia caused by SARS-CoV-2 show more severe hypercytokinemia with corresponding lymphocytopenia than patients with mild pneumonia; thus, early immunomodulator treatment, including corticosteroids, has been considered. However, current guidelines recommend their use only for patients with advanced pneumonia or acute respiratory distress syndrome. Since the immunopathogenesis of pneumonia may be the same for all patients regardless of age or severity and the critical immune-mediated lung injury may begin in the early stage of the disease, early immunomodulator treatment, including corticosteroids and intravenous immunoglobulin, can help reduce morbidity and possibly mortality rates of older patients with underlying conditions.

A microneedle patch for measles and rubella vaccination: a game changer for achieving elimination

While morbidity and mortality associated with measles and rubella (MR) have dramatically decreased, there are still >100000 estimated deaths due to measles and an estimated 100000 infants born with congenital rubella syndrome annually. Given highly effective MR vaccines, the primary barrier to global elimination of these diseases is low vaccination coverage, especially among the most underserved populations in resource-limited settings. In contrast to conventional MR vaccination by hypodermic injection, microneedle patches are being developed to enable MR vaccination by minimally trained personnel. Simplified supply chain, reduced need for cold chain storage, elimination of vaccine reconstitution, no sharps waste, reduced vaccine wastage, and reduced total system cost of vaccination are advantages of this approach. Preclinical work to develop a MR vaccine patch has proceeded through successful immunization studies in rodents and non-human primates. On-going programs seek to make MR vaccine patches available to support MR elimination efforts around the world.

Measles Encephalitis: Towards New Therapeutics

Measles remains a major cause of morbidity and mortality worldwide among vaccine preventable diseases. Recent decline in vaccination coverage resulted in re-emergence of measles outbreaks. Measles virus (MeV) infection causes an acute systemic disease, associated in certain cases with central nervous system (CNS) infection leading to lethal neurological disease. Early following MeV infection some patients develop acute post-infectious measles encephalitis (APME), which is not associated with direct infection of the brain. MeV can also infect the CNS and cause sub-acute sclerosing panencephalitis (SSPE) in immunocompetent people or measles inclusion-body encephalitis (MIBE) in immunocompromised patients. To date, cellular and molecular mechanisms governing CNS invasion are still poorly understood. Moreover, the known MeV entry receptors are not expressed in the CNS and how MeV enters and spreads in the brain is not fully understood. Different antiviral treatments have been tested and validated in vitro, ex vivo and in vivo, mainly in small animal models. Most treatments have high efficacy at preventing infection but their effectiveness after CNS manifestations remains to be evaluated. This review describes MeV neural infection and current most advanced therapeutic approaches potentially applicable to treat MeV CNS infection.

Examining the Complex Relationship Between Tuberculosis and Other Infectious Diseases in Children

Millions of children are exposed to tuberculosis (TB) each year, many of which become infected with Mycobacterium tuberculosis. Most children can immunologically contain or eradicate the organism without pathology developing. However, in a minority, the organism overcomes the immunological constraints, proliferates and causes TB disease. Each year a million children develop TB disease, with a quarter dying. While it is known that young children and those with immunodeficiencies are at increased risk of progression from TB infection to TB disease, our understanding of risk factors for this transition is limited. The most immunologically disruptive process that can happen during childhood is infection with another pathogen and yet the impact of co-infections on TB risk is poorly investigated. Many diseases have overlapping geographical distributions to TB and affect similar patient populations. It is therefore likely that infection with viruses, bacteria, fungi and protozoa may impact on the risk of developing TB disease following exposure and infection, although disentangling correlation and causation is challenging. As vaccinations also disrupt immunological pathways, these may also impact on TB risk. In this article we describe the pediatric immune response to M. tuberculosis and then review the existing evidence of the impact of co-infection with other pathogens, as well as vaccination, on the host response to M. tuberculosis. We focus on the impact of other organisms on the risk of TB disease in children, in particularly evaluating if co-infections drive host immune responses in an age-dependent way. We finally propose priorities for future research in this field. An improved understanding of the impact of co-infections on TB could assist in TB control strategies, vaccine development (for TB vaccines or vaccines for other organisms), TB treatment approaches and TB diagnostics.

Modified Dose Efficacy Trial of a Canine Distemper-Measles Vaccine for Use in Rhesus Macaques (Macaca mulatta)

Measles virus causes a highly infectious disease in NHP. Clinical signs range from asymptomatic to fatal, although measles virus is most well-known for its characteristic generalized maculopapular rash. Along with appropriate quarantine practices, restricted human access, and appropriate personal protective equipment, vaccines are used to combat the risk of infection. The canine distemper-measles vaccine (CDMV), administered at the manufacturer's standard dose (1.0 mL IM), has been shown to be effective against clinical measles disease in rhesus macaques (Macaca mulatta). The goal of the current study was to test whether doses smaller than the manufacturer's recommended dose stimulated adequate antibody production to protect against infection. We hypothesized that either 0.25 or 0.5 mL IM of CDMV would stimulate antibody production comparable to the manufacturer's recommended dose. We found that the 0.25-mL dose was less effective at inducing antibodies than either the standard (1.0 mL) or 0.5-mL dose, which both yielded similar titers. The primary implication of this study informs balancing resource allocation and providing efficacious immunity. By using half the manufacturer-recommended dose, the 50% cost reduction may provide sufficient monetary incentive to implement, maintain, or modify measles vaccination programs at NHP facilities.

Comprehensive Bioinformatics Analysis of the Immune Mechanism of Dendritic Cells Against Measles Virus

Background

The purpose of this study was to explore the immune mechanism of dendritic cells (DCs) against measles virus (MV), and to identify potential biomarkers to improve measles prevention and treatment.

Material/Methods

The gene expression profile of GSE980, which comprised 10 DC samples from human blood infected with MV (RNA was isolated at 3, 6, 12, and 24 h post-infection) and 4 normal DC control samples, was obtained from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) between the MV-infected DC samples and the control samples were screened using Genevestigator software. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analyses were performed using GenCLip 2.0 and STRING 10.5 software. The protein–protein interaction (PPI) network was established using Cytoscape 3.4.0.

Results

The gene expression profiles of MV-infected DCs were obviously changed. Twenty-six common DEGs (0.9%, MV-infected DCs vs. normal DCs) were identified at 4 different time points, including 14 down-regulated and 12 up-regulated genes (P=0.001). GO analysis showed that DEGs were significantly enriched in defense response to virus, type I interferon signaling pathway, et al. ISG15 and CXCL10 were the key genes in the PPI network of the DEGs, and may interact directly with the type I interferon signaling and defense response to virus signaling.

Conclusions

The DEGs increased gradually with the duration of MV infection. The type I interferon signaling pathway and the defense response to viral processes can be activated against MV by ISG15 and CXCL10 in DCs. These may provide novel targets for the treatment of MV.

T Lymphocytes as Measurable Targets of Protection and Vaccination Against Viral Disorders

Continuous epidemiological surveillance of existing and emerging viruses and their associated disorders is gaining importance in light of their abilities to cause unpredictable outbreaks as a result of increased travel and vaccination choices by steadily growing and aging populations. Close surveillance of outbreaks and herd immunity are also at the forefront, even in industrialized countries, where previously eradicated viruses are now at risk of re-emergence due to instances of strain recombination, contractions in viral vector geographies, and from their potential use as agents of bioterrorism. There is a great need for the rational design of current and future vaccines targeting viruses, with a strong focus on vaccine targeting of adaptive immune effector memory T cells as the gold standard of immunity conferring long-lived protection against a wide variety of pathogens and malignancies. Here, we review viruses that have historically caused large outbreaks and severe lethal disorders, including respiratory, gastric, skin, hepatic, neurologic, and hemorrhagic fevers. To observe trends in vaccinology against these viral disorders, we describe viral genetic, replication, transmission, and tropism, host-immune evasion strategies, and the epidemiology and health risks of their associated syndromes. We focus on immunity generated against both natural infection and vaccination, where a steady shift in conferred vaccination immunogenicity is observed from quantifying activated and proliferating, long-lived effector memory T cell subsets, as the prominent biomarkers of long-term immunity against viruses and their associated disorders causing high morbidity and mortality rates.

Reverse Genetics for Peste des Petits Ruminants Virus: Current Status and Lessons to Learn from Other Non-segmented Negative-Sense RNA Viruses

Peste des petits ruminants (PPR) is a highly contagious transboundary animal disease with a severe socio-economic impact on the livestock industry, particularly in poor countries where it is endemic. Full understanding of PPR virus (PPRV) pathobiology and molecular biology is critical for effective control and eradication of the disease. To achieve these goals, establishment of stable reverse genetics systems for PPRV would play a key role. Unfortunately, this powerful technology remains less accessible and poorly documented for PPRV. In this review, we discussed the current status of PPRV reverse genetics as well as the recent innovations and advances in the reverse genetics of other non-segmented negative-sense RNA viruses that could be applicable to PPRV. These strategies may contribute to the improvement of existing techniques and/or the development of new reverse genetics systems for PPRV.

Measles vaccination in an increasingly immunized and developed world

Increased measles immunization has led to a significant decline in measles incidence and mortality. During 2016 it is estimated that fewer than 100,000 died from measles for the first time in recorded history. In highly immunized countries measles epidemiology has changed. Threats to national elimination goals and public health include aging cohorts of naïve people that exist from imperfect vaccination rates during the early years of immunization programs. This may be complemented by some loss of immunity in vaccinated populations. While childhood immunization must remain a focus for control efforts, due to higher mortality in the very young, these naïve adolescents and adults also accumulate as they age and add to the pool of susceptible people, perhaps beyond the view of those that are focused on childhood immunization. Here, features of measles epidemiology and control in highly immunized populations are reviewed, providing global data where necessary, to highlight why countries with high immunization coverage are still threatened by measles outbreaks and how changing dynamics may alter disease control.

Multidisciplinary studies on a sick-leader syndrome-associated mass stranding of sperm whales (Physeter macrocephalus) along the Adriatic coast of Italy

Mass strandings of sperm whales (Physeter macrocephalus) are rare in the Mediterranean Sea. Nevertheless, in 2014 a pod of 7 specimens stranded alive along the Italian coast of the Central Adriatic Sea: 3 individuals died on the beach after a few hours due to internal damages induced by prolonged recumbency; the remaining 4 whales were refloated after great efforts. All the dead animals were genetically related females; one was pregnant. All the animals were infected by dolphin morbillivirus (DMV) and the pregnant whale was also affected by a severe nephropathy due to a large kidney stone. Other analyses ruled out other possible relevant factors related to weather conditions or human activities. The results of multidisciplinary post-mortem analyses revealed that the 7 sperm whales entered the Adriatic Sea encountering adverse weather conditions and then kept heading northward following the pregnant but sick leader of the pod, thereby reaching the stranding site. DMV infection most likely played a crucial role in impairing the health condition and orientation abilities of the whales. They did not steer back towards deeper waters, but eventually stranded along the Central Adriatic Sea coastline, a real trap for sperm whales.

Pulmonary measles disease: old and new imaging tools

BACKGROUND

Measles virus can cause lower respiratory tract infection, so that chest radiography is necessary to investigate lung involvement in patients with respiratory distress.

PURPOSE

To assess measles pneumonia imaging during the measles outbreak occurred in 2016-2017 in Italy.

MATERIAL AND METHODS

We retrospectively observed adult patients with a serological diagnosis of measles, who underwent chest-X rays for suspected pneumonia. If a normal radiography resulted, the patient underwent unenhanced CT. A CT post processing software package was used for an additional quantitative lung and airway involvement analysis .

RESULTS

Among 290 patients affected by measles, 150 underwent chest-X ray. Traditional imaging allowed the pneumonia diagnosis in 114 patients (76%). The most frequent abnormality at chest X-rays was bronchial wall thickening, observed in 88.5% of the cases; radiological findings are faint in the 25% of the cases (29/114 patients). In nine subjects with a normal chest X-ray, unenhanced CT with a quantitative analysis was performed, and depicted features consistent with constrictive bronchiolitis.

CONCLUSION

Measles may produce bronchiolitis and pneumonia. In the cases in which involvement of pulmonary parenchyma is not sufficient to result in radiological abnormalities, CT used with a dedicated postprocessing software package, provides an accurate lungs and airways analysis, also determining the percentage of lung involvement.

Dolphin Morbillivirus Associated with a Mass Stranding of Sperm Whales, Italy

In September 2014, seven sperm whales were stranded along Italy’s Adriatic coastline. Postmortem investigations on 3 female adult whales and 1 male fetus carried by the largest female revealed molecular and immunohistochemical evidence of dolphin morbillivirus infection. A possible role of the virus in the stranding event was considered.

Measles

Measles is a highly contagious disease that results from infection with measles virus and is still responsible for more than 100 000 deaths every year, down from more than 2 million deaths annually before the introduction and widespread use of measles vaccine. Measles virus is transmitted by the respiratory route and illness begins with fever, cough, coryza, and conjunctivitis followed by a characteristic rash. Complications of measles affect most organ systems, with pneumonia accounting for most measles-associated morbidity and mortality. The management of patients with measles includes provision of vitamin A. Measles is best prevented through vaccination, and the major reductions in measles incidence and mortality have renewed interest in regional elimination and global eradication. However, urgent efforts are needed to increase stagnating global coverage with two doses of measles vaccine through advocacy, education, and the strengthening of routine immunisation systems. Use of combined measles-rubella vaccines provides an opportunity to eliminate rubella and congenital rubella syndrome. Ongoing research efforts, including the development of point-of-care diagnostics and microneedle patches, will facilitate progress towards measles elimination and eradication.

Biophysical Properties and Antiviral Activities of Measles Fusion Protein Derived Peptide Conjugated with 25-Hydroxycholesterol

Measles virus (MV) infection is re-emerging, despite the availability of an effective vaccine. The mechanism of MV entry into a target cell relies on coordinated action between the MV hemagglutinin (H) receptor binding protein and the fusion envelope glycoprotein (F) which mediates fusion between the viral and cell membranes. Peptides derived from the C-terminal heptad repeat (HRC) of F can interfere with this process, blocking MV infection. As previously described, biophysical properties of HRC-derived peptides modulate their antiviral potency. In this work, we characterized a MV peptide fusion inhibitor conjugated to 25-hydroxycholesterol (25HC), a cholesterol derivative with intrinsic antiviral activity, and evaluated its interaction with membrane model systems and human blood cells. The peptide (MV.

Effectiveness of Early Measles, Mumps, and Rubella Vaccination Among 6-14-Month-Old Infants During an Epidemic in the Netherlands: An Observational Cohort Study

Background

Routinely, the first measles, mumps, and rubella (MMR) vaccine dose is given at 14 months of age in the Netherlands. However, during a measles epidemic in 2013-2014, MMR vaccination was also offered to 6-14-month-olds in municipalities with <90% MMR vaccination coverage. We studied the effectiveness of the early MMR vaccination schedule.

Methods

Parents of all infants targeted for early MMR vaccination were asked to participate. When parent(s) suspected measles, their infant's saliva was tested for measles-specific antibodies. The vaccine effectiveness (VE) against laboratory-confirmed and self-reported measles was estimated using Cox regression, with VE calculated as 1 minus the hazard ratio.

Results

Three vaccinated and 10 unvaccinated laboratory-confirmed cases occurred over observation times of 106631 and 23769 days, respectively. The unadjusted VE against laboratory-confirmed measles was 94% (95% confidence interval [CI], 79%-98%). After adjustment for religion and sibling's vaccination status, the VE decreased to 71% (-72%-95%). For self-reported measles, the unadjusted and adjusted VE was 67% (40%-82%) and 43% (-12%-71%), respectively.

Conclusions

Infants vaccinated between 6 and 14 months of age had a lower risk of measles than unvaccinated infants. However, part of the effect was caused by herd immunity, since vaccinated infants were more likely to be surrounded by other vaccinated individuals.

Delineating morbillivirus entry, dissemination and airborne transmission by studying in vivo competition of multicolor canine distemper viruses in ferrets

Identification of cellular receptors and characterization of viral tropism in animal models have vastly improved our understanding of morbillivirus pathogenesis. However, specific aspects of viral entry, dissemination and transmission remain difficult to recapitulate in animal models. Here, we used three virologically identical but phenotypically distinct recombinant (r) canine distemper viruses (CDV) expressing different fluorescent reporter proteins for in vivo competition and airborne transmission studies in ferrets (Mustela putorius furo). Six donor ferrets simultaneously received three rCDVs expressing green, red or blue fluorescent proteins via conjunctival (ocular, Oc), intra-nasal (IN) or intra-tracheal (IT) inoculation. Two days post-inoculation sentinel ferrets were placed in physically separated adjacent cages to assess airborne transmission. All donor ferrets developed lymphopenia, fever and lethargy, showed progressively increasing systemic viral loads and were euthanized 14 to 16 days post-inoculation. Systemic replication of virus inoculated via the Oc, IN and IT routes was detected in 2/6, 5/6 and 6/6 ferrets, respectively. In five donor ferrets the IT delivered virus dominated, although replication of two or three different viruses was detected in 5/6 animals. Single lymphocytes expressing multiple fluorescent proteins were abundant in peripheral blood and lymphoid tissues, demonstrating the occurrence of double and triple virus infections. Transmission occurred efficiently and all recipient ferrets showed evidence of infection between 18 and 22 days post-inoculation of the donor ferrets. In all cases, airborne transmission resulted in replication of a single-colored virus, which was the dominant virus in the donor ferret. This study demonstrates that morbilliviruses can use multiple entry routes in parallel, and co-infection of cells during viral dissemination in the host is common. Airborne transmission was efficient, although transmission of viruses expressing a single color suggested a bottleneck event. The identity of the transmitted virus was not determined by the site of inoculation but by the viral dominance during dissemination.

Canine distemper virus (CDV) infection of ferrets is a tractable animal model for measles. Ferrets are highly susceptible to CDV, and inoculation with a low dose leads to lethal disease. We performed in vivo competition experiments to study virus entry, dissemination and transmission. Ferrets were simultaneously inoculated with CDV via the conjunctival, intra-nasal and intra-tracheal routes. The viruses were identical except for the fluorescent reporter protein encoded by the viral genome. By detecting cells expressing the different fluorescent reporter proteins at various sites in the host, we determined that CDV can enter the host in parallel at multiple sites. Virus spread in the ferret occurred via infected lymphocytes, which often turned out to be double- or triple-infected. Sentinel ferrets, placed in physically separated adjacent cages, became infected by airborne transmission. Transmission of the dominant single color despite replication of multicolor viruses in the upper respiratory tract suggested a bottleneck event.

In Vivo Efficacy of Measles Virus Fusion Protein-Derived Peptides Is Modulated by the Properties of Self-Assembly and Membrane Residence

Measles virus (MV) infection is undergoing resurgence and remains one of the leading causes of death among young children worldwide despite the availability of an effective measles vaccine. MV infects its target cells by coordinated action of the MV hemagglutinin (H) and fusion (F) envelope glycoproteins; upon receptor engagement by H, the prefusion F undergoes a structural transition, extending and inserting into the target cell membrane and then refolding into a postfusion structure that fuses the viral and cell membranes. By interfering with this structural transition of F, peptides derived from the heptad repeat (HR) regions of F can inhibit MV infection at the entry stage. In previous work, we have generated potent MV fusion inhibitors by dimerizing the F-derived peptides and conjugating them to cholesterol. We have shown that prophylactic intranasal administration of our lead fusion inhibitor efficiently protects from MV infection in vivo We show here that peptides tagged with lipophilic moieties self-assemble into nanoparticles until they reach the target cells, where they are integrated into cell membranes. The self-assembly feature enhances biodistribution and the half-life of the peptides, while integration into the target cell membrane increases fusion inhibitor potency. These factors together modulate in vivo efficacy. The results suggest a new framework for developing effective fusion inhibitory peptides.

IMPORTANCE

Measles virus (MV) infection causes an acute illness that may be associated with infection of the central nervous system (CNS) and severe neurological disease. No specific treatment is available. We have shown that fusion-inhibitory peptides delivered intranasally provide effective prophylaxis against MV infection. We show here that specific biophysical properties regulate the in vivo efficacy of MV F-derived peptides.

Synthetically derived bat influenza A-like viruses reveal a cell type- but not species-specific tropism

Two novel influenza A-like viral genome sequences have recently been identified in Central and South American fruit bats and provisionally designated "HL17NL10" and "HL18NL11." All efforts to isolate infectious virus from bats or to generate these viruses by reverse genetics have failed to date. Recombinant vesicular stomatitis virus (VSV) encoding the hemagglutinin-like envelope glycoproteins HL17 or HL18 in place of the VSV glycoprotein were generated to identify cell lines that are susceptible to bat influenza A-like virus entry. More than 30 cell lines derived from various species were screened but only a few cell lines were found to be susceptible, including Madin-Darby canine kidney type II (MDCK II) cells. The identification of cell lines susceptible to VSV chimeras allowed us to recover recombinant HL17NL10 and HL18NL11 viruses from synthetic DNA. Both influenza A-like viruses established a productive infection in MDCK II cells; however, HL18NL11 replicated more efficiently than HL17NL10 in this cell line. Unlike conventional influenza A viruses, bat influenza A-like viruses started the infection preferentially at the basolateral membrane of polarized MDCK II cells; however, similar to conventional influenza A viruses, bat influenza A-like viruses were released primarily from the apical site. The ability of HL18NL11 or HL17NL10 viruses to infect canine and human cells might reflect a zoonotic potential of these recently identified bat viruses.

Measles Virus Host Invasion and Pathogenesis

Measles virus is a highly contagious negative strand RNA virus that is transmitted via the respiratory route and causes systemic disease in previously unexposed humans and non-human primates. Measles is characterised by fever and skin rash and usually associated with cough, coryza and conjunctivitis. A hallmark of measles is the transient immune suppression, leading to increased susceptibility to opportunistic infections. At the same time, the disease is paradoxically associated with induction of a robust virus-specific immune response, resulting in lifelong immunity to measles. Identification of CD150 and nectin-4 as cellular receptors for measles virus has led to new perspectives on tropism and pathogenesis. In vivo studies in non-human primates have shown that the virus initially infects CD150⁺ lymphocytes and dendritic cells, both in circulation and in lymphoid tissues, followed by virus transmission to nectin-4 expressing epithelial cells. The abilities of the virus to cause systemic infection, to transmit to numerous new hosts via droplets or aerosols and to suppress the host immune response for several months or even years after infection make measles a remarkable disease. This review briefly highlights current topics in studies of measles virus host invasion and pathogenesis.

Measles

Measles is an infectious disease in humans caused by the measles virus (MeV). Before the introduction of an effective measles vaccine, virtually everyone experienced measles during childhood. Symptoms of measles include fever and maculopapular skin rash accompanied by cough, coryza and/or conjunctivitis. MeV causes immunosuppression, and severe sequelae of measles include pneumonia, gastroenteritis, blindness, measles inclusion body encephalitis and subacute sclerosing panencephalitis. Case confirmation depends on clinical presentation and results of laboratory tests, including the detection of anti-MeV IgM antibodies and/or viral RNA. All current measles vaccines contain a live attenuated strain of MeV, and great progress has been made to increase global vaccination coverage to drive down the incidence of measles. However, endemic transmission continues in many parts of the world. Measles remains a considerable cause of childhood mortality worldwide, with estimates that >100,000 fatal cases occur each year. Case fatality ratio estimates vary from <0.01% in industrialized countries to >5% in developing countries. All six WHO regions have set goals to eliminate endemic transmission of MeV by achieving and maintaining high levels of vaccination coverage accompanied by a sensitive surveillance system. Because of the availability of a highly effective and relatively inexpensive vaccine, the monotypic nature of the virus and the lack of an animal reservoir, measles is considered a candidate for eradication.

Measles Virus Fusion Protein: Structure, Function and Inhibition

Measles virus (MeV), a highly contagious member of the Paramyxoviridae family, causes measles in humans. The Paramyxoviridae family of negative single-stranded enveloped viruses includes several important human and animal pathogens, with MeV causing approximately 120,000 deaths annually. MeV and canine distemper virus (CDV)-mediated diseases can be prevented by vaccination. However, sub-optimal vaccine delivery continues to foster MeV outbreaks. Post-exposure prophylaxis with antivirals has been proposed as a novel strategy to complement vaccination programs by filling herd immunity gaps. Recent research has shown that membrane fusion induced by the morbillivirus glycoproteins is the first critical step for viral entry and infection, and determines cell pathology and disease outcome. Our molecular understanding of morbillivirus-associated membrane fusion has greatly progressed towards the feasibility to control this process by treating the fusion glycoprotein with inhibitory molecules. Current approaches to develop anti-membrane fusion drugs and our knowledge on drug resistance mechanisms strongly suggest that combined therapies will be a prerequisite. Thus, discovery of additional anti-fusion and/or anti-attachment protein small-molecule compounds may eventually translate into realistic therapeutic options.

The Association between Invasive Group A Streptococcal Diseases and Viral Respiratory Tract Infections

Viral infections of the upper respiratory tract are associated with a variety of invasive diseases caused by Streptococcus pyogenes, the group A streptococcus, including pneumonia, necrotizing fasciitis, toxic shock syndrome, and bacteremia. While these polymicrobial infections, or superinfections, are complex, progress has been made in understanding the molecular basis of disease. Areas of investigation have included the characterization of virus-induced changes in innate immunity, differences in bacterial adherence and internalization following viral infection, and the efficacy of vaccines in mitigating the morbidity and mortality of superinfections. Here, we briefly summarize viral-S. pyogenes superinfections with an emphasis on those affiliated with influenza viruses.

Genetic Instability of RNA Viruses

Despite having very limited coding capacity, RNA viruses are able to withstand challenge of antiviral drugs, cause epidemics in previously exposed human populations, and, in some cases, infect multiple host species. They are able to achieve this by virtue of their ability to multiply very rapidly, coupled with their extraordinary degree of genetic heterogeneity. RNA viruses exist not as single genotypes, but as a swarm of related variants, and this genomic diversity is an essential feature of their biology. RNA viruses have a variety of mechanisms that act in combination to determine their genetic heterogeneity. These include polymerase fidelity, error-mitigation mechanisms, genomic recombination, and different modes of genome replication. RNA viruses can vary in their ability to tolerate mutations, or “genetic robustness,” and several factors contribute to this. Finally, there is evidence that some RNA viruses exist close to a threshold where polymerase error rate has evolved to maximize the possible sequence space available, while avoiding the accumulation of a lethal load of deleterious mutations. We speculate that different viruses have evolved different error rates to complement the different “life-styles” they possess.

Biosafety considerations for attenuated measles virus vectors used in virotherapy and vaccination

Attenuated measles virus (MV) is one of the most effective and safe vaccines available, making it attractive candidate vector to prevent infectious diseases. Attenuated MV have acquired the ability to use the complement regulator CD46 as a major receptor to mediate virus entry and intercellular fusion. Therefore, attenuated MV strains preferentially infect and destroy a wide variety of cancer cells making them also attractive oncolytic vectors. The use of recombinant MV vector has to comply with various regulatory requirements, particularly relating to the assessment of potential risks for human health and the environment. The present article highlights the main characteristics of MV and recombinant MV vectors used for vaccination and virotherapy and discusses these features from a biosafety point of view.

Detection of Measles Virus RNA in Air and Surface Specimens in a Hospital Setting

Measles virus (MeV) is known to be highly contagious, with an infectious period lasting from 4 days before to 4 days after rash onset. An unvaccinated, young, female patient with measles confirmed by direct epidemiologic link was hospitalized on day 5 after rash onset. Environmental samples were collected over the 4-day period of hospitalization in a single room. MeV RNA was detectable in air specimens, on surface specimens, and on respirators on days 5-8 after rash onset. This is the first report of environmental surveillance for MeV, and the results suggest that MeV-infected fomites may be present in healthcare settings.

Replication-Competent Influenza Virus and Respiratory Syncytial Virus Luciferase Reporter Strains Engineered for Co-Infections Identify Antiviral Compounds in Combination Screens

Myxoviruses such as influenza A virus (IAV) and respiratory syncytial virus (RSV) are major human pathogens, mandating the development of novel therapeutics. To establish a high-throughput screening protocol for the simultaneous identification of pathogen- and host-targeted hit candidates against either pathogen or both, we have attempted co-infection of cells with IAV and RSV. However, viral replication kinetics were incompatible, RSV signal window was low, and an IAV-driven minireplicon reporter assay used in initial screens narrowed the host cell range and restricted the assay to single-cycle infections. To overcome these limitations, we developed an RSV strain carrying firefly luciferase fused to an innovative universal small-molecule assisted shut-off domain, which boosted assay signal window, and a hyperactive fusion protein that synchronized IAV and RSV reporter expression kinetics and suppressed the identification of RSV entry inhibitors sensitive to a recently reported RSV pan-resistance mechanism. Combined with a replication-competent recombinant IAV strain harboring nanoluciferase, the assay performed well on a human respiratory cell line and supports multicycle infections. Miniaturized to 384-well format, the protocol was validated through screening of a set of the National Institutes of Health Clinical Collection (NCC) in quadruplicate. These test screens demonstrated favorable assay parameters and reproducibility. Application to a LOPAC library of bioactive compounds in a proof-of-concept campaign detected licensed antimyxovirus therapeutics, ribavirin and the neuraminidase inhibitor zanamivir, and identified two unexpected RSV-specific hit candidates, Fenretinide and the opioid receptor antagonist BNTX-7. Hits were evaluated in direct and orthogonal dose-response counterscreens using a standard recRSV reporter strain expressing Renilla luciferase.

SLAM- and nectin-4-independent noncytolytic spread of canine distemper virus in astrocytes

Measles and canine distemper viruses (MeV and CDV, respectively) first replicate in lymphatic and epithelial tissues by using SLAM and nectin-4 as entry receptors, respectively. The viruses may also invade the brain to establish persistent infections, triggering fatal complications, such as subacute sclerosis pan-encephalitis (SSPE) in MeV infection or chronic, multiple sclerosis-like, multifocal demyelinating lesions in the case of CDV infection. In both diseases, persistence is mediated by viral nucleocapsids that do not require packaging into particles for infectivity but are directly transmitted from cell to cell (neurons in SSPE or astrocytes in distemper encephalitis), presumably by relying on restricted microfusion events. Indeed, although morphological evidence of fusion remained undetectable, viral fusion machineries and, thus, a putative cellular receptor, were shown to contribute to persistent infections. Here, we first showed that nectin-4-dependent cell-cell fusion in Vero cells, triggered by a demyelinating CDV strain, remained extremely limited, thereby supporting a potential role of nectin-4 in mediating persistent infections in astrocytes. However, nectin-4 could not be detected in either primary cultured astrocytes or the white matter of tissue sections. In addition, a bioengineered "nectin-4-blind" recombinant CDV retained full cell-to-cell transmission efficacy in primary astrocytes. Combined with our previous report demonstrating the absence of SLAM expression in astrocytes, these findings are suggestive for the existence of a hitherto unrecognized third CDV receptor expressed by glial cells that contributes to the induction of noncytolytic cell-to-cell viral transmission in astrocytes.

IMPORTANCE

While persistent measles virus (MeV) infection induces SSPE in humans, persistent canine distemper virus (CDV) infection causes chronic progressive or relapsing demyelination in carnivores. Common to both central nervous system (CNS) infections is that persistence is based on noncytolytic cell-to-cell spread, which, in the case of CDV, was demonstrated to rely on functional membrane fusion machinery complexes. This inferred a mechanism where nucleocapsids are transmitted through macroscopically invisible microfusion events between infected and target cells. Here, we provide evidence that CDV induces such microfusions in a SLAM- and nectin-4-independent manner, thereby strongly suggesting the existence of a third receptor expressed in glial cells (referred to as GliaR). We propose that GliaR governs intercellular transfer of nucleocapsids and hence contributes to viral persistence in the brain and ensuing demyelinating lesions.

Discovery of imidazopyridine derivatives as highly potent respiratory syncytial virus fusion inhibitors

A series of imidazolepyridine derivatives were designed and synthesized according to the established docking studies. The imidazopyridine derivatives were found to have good potency and physical-chemical properties. Several highly potent compounds such as 8ji, 8jl, and 8jm were identified with single nanomolar activities. The most potent compound 8jm showed an IC50 of 3 nM, lower microsome clearance and no CYP inhibition. The profile of 8jm appeared to be superior to BMS433771, and supported further optimization.