Human Virus Disease Research Articles

Identification and genetic characterization of five novel bat coronaviruses from Yunnan, China

BackgroundCoronaviruses (CoVs) represent a serious threat to human health and have become a major transmissible, endemic, and causative pathogen in humans; they represent a major health concern, given their ability to cause infectious diseases. Bats are natural hosts for diverse viruses. Many transmission events of CoVs and identification of multiple novel CoVs in bats has increased attention towards their capacity to serve as hosts for zoonotic viruses.ResultsIn this study, 61 bats from Yunnan Province were analyzed, identifying seven CoVs, including three α- and two β-CoVs with full-genome sequences. Among the five identified alpha-CoVs, four belong to the Decacovirus subgenus and one to the Minunacovirus subgenus. Two beta-CoVs were also identified, both belonging to the Sarbecovirus subgenus.The genetic structures revealed similarities to known strains such as HKU10 and SARS-CoV-2, along with novel findings such as the Minunacovirus subgenus CoV YJ3c/f and unique ORF patterns. Our results demonstrated that strain JCC9 has a unique recombination pattern and shows a higher binding affinity to civet and pangolin ACE2 receptors, then the HpJC8xc strain transmits and recombines between hosts (bats), indicating a potential risk of crossing the interspecies barrier and infecting other animals.ConclusionsThe CoVs detected in the bats studied in this research exhibit high diversity. Genomic analysis revealed that CoVs in bats undergo frequent recombination events. Furthermore, recombination patterns and evolutionary analyses suggest that alpha-CoVs are more prone to cross-species transmission across different bat families/genera, whereas beta-CoVs demonstrate host specificity and tend to co-evolve with their bat hosts.Our finding suggest that bats, as hosts of CoVs, be constantly monitored to prevent outbreaks of new infections caused by viruses passing across interspecies barriers, and consequently, viral diseases in humans or livestock.

Ebola Virus Matrix Protein VP40 Single Mutations G198R and G201R Significantly Enhance Plasma Membrane Localization.

Viral proteins frequently undergo single or multiple amino acid mutations during replication, which can significantly alter their functionality. The Ebola virus matrix protein VP40 is multifunctional but primarily responsible for creating the viral envelope by binding to the inner leaflet of the host cell plasma membrane (PM). Changes to the VP40 surface cationic charge via mutations can influence PM interactions, resulting in altered viral assembly and budding. A recent mutagenesis study evaluated the effects of several mutations and found that mutations G198R and G201R enhanced VP40 assembly at the PM and virus-like particle budding. These two mutations lie in the loop region of the C-terminal domain (CTD), which directly interacts with the PM. To understand the role of these mutations in PM localization at the molecular level, we performed both all-atom and coarse-grained molecular dynamics simulations using a dimer-dimer configuration of VP40, which contains the CTD-CTD interface. Our studies indicate that the location of mutations on the outer surface of the CTD regions can lead to changes in membrane binding orientation and degree of membrane penetration. Direct PI(4,5)P2 interactions with the mutated residues seem to further stabilize and pull VP40 into the PM, thereby enhancing interactions with numerous amino acids that were otherwise infrequently or completely inaccessible. These multiscale computational studies provide new insights at the atomic and molecular level as to how VP40-PM interactions are altered through single amino acid mutations. Given the high case fatality rates associated with Ebola virus disease in humans, it is essential to explore the mechanisms of viral assembly in the presence of mutations to mitigate the severity of the disease and understand the potential of future outbreaks.

Development of targeted whole genome sequencing approaches for Crimean-Congo haemorrhagic fever virus (CCHFV)

Crimean-Congo haemorrhagic fever (CCHF) is the most prevalent human tick-borne viral disease, with a reported case fatality rate of 30 % or higher. The virus contains a tri-segmented, negative-sense RNA genome consisting of the small (S), medium (M) and large (L) segments encoding respectively the nucleoprotein (NP), the glycoproteins precursor (GPC) and the viral RNA-dependent RNA polymerase (RDRP). CCHFV is one of the most genetically diverse arboviruses, with seven distinct lineages named after the region they were first reported in and based on S segment phylogenetic analysis.Due to the high genetic divergence of the virus, a single targeted tiling PCR strategy to enrich for viral nucleic acids prior to sequencing is difficult to develop, and previously we have developed and validated a tiling PCR enrichment method for the Europe 1 genetic lineage.We have developed a targeted, probe hybridisation capture method and validated its performance on clinical as well as cell-cultured material of CCHFV from different genetic lineages, including Europe 1, Europe 2, Africa 2 and Africa 3. The method produced over 95 % reference coverages with at least 10x sequencing depth. While we were only able to recover a single complete genome sequence from the tested Europe 1 clinical samples with the capture hybridisation protocol, the data provides evidence of its applicability to different CCHFV genetic lineages.CCHFV is an important tick-borne human pathogen with wide geographical distribution. Environmental as well as anthropogenic factors are causing increased CCHFV transmission. Development of strategies to recover CCHFV sequences from genetically diverse lineages of the virus is of paramount importance to monitor the presence of the virus in new areas, and in public health responses for CCHFV molecular surveillance to rapidly detect, diagnose and characterise currently circulating strains.

MicroRNAs and human viral diseases: A focus on the role of microRNA-29

The viral replication can impress through cellular miRNAs. Indeed, either the antiviral responses or the viral infection changes through cellular miRNAs resulting in affecting many regulatory signaling pathways. One of the microRNA families that is effective in human cancers, diseases, and viral infections is the miR-29 family. Members of miR-29 family are effective in different viral infections as their roles have appeared in regulation of immunity pathways either in innate immunity including interferon and inflammatory pathways or in adaptive immunity including activation of T-cells and antibodies production. Although miR-29a affects viral replication by suppressing antiviral responses, it can inhibit the expression of viral mRNAs via binding to their 3′UTR. In the present work, we discuss the evidence related to miR-29a and viral infection through host immunity regulation. We also review roles of other miR-29 family members by focusing on their role as biomarkers for diagnosing and targets for viral diseases management.

Zebrafish as a Model for Investigating Antiviral Innate Immunity.

Zebrafish is a widely used model organism in genetics, developmental biology, pathology, and immunology research. Due to their fast reproduction, large numbers, transparent early embryos, and high genetic conservation with the human genome, zebrafish have been used as a model for studying human and fish viral diseases. In particular, the ability to easily perform forward and reverse genetics and lacking a functional adaptive immune response during the early period of development establish the zebrafish as a favored option to assess the functional implication of specific genes in the antiviral innate immune response and the pathogenesis of viral diseases. In this chapter, we detail protocols for the antiviral innate immunity analysis using the zebrafish model, including the generation of gene-overexpression zebrafish, generation of gene-knockout zebrafish by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology, methods of viral infection in zebrafish larvae, analyzing the expression of antiviral genes in zebrafish larvae using qRT-PCR, Western blotting and transcriptome sequencing, and in vivo antiviral assays. These experimental protocols provide effective references for studying the antiviral immune response in the zebrafish model.

Enzyme immunoassay system for serological diagnosis of hemorrhagic fever with renal syndrome based on inactivated purified Puumala virus (Hantaviridae: Orthohantavirus)

Hemorrhagic fever with renal syndrome (HFRS) is the most common zoonotic human viral disease in the Russian Federation. More than 98% of the HFRS cases are caused by Puumala orthohantavirus (PUU). Effective serological tests are required for laboratory diagnosis of HFRS. Construction of an enzyme immunoassay (ELISA) test system for detection of specific antibodies using standard antigen in the form of highly purified inactivated PUU virus as immunosorbent. Preparation of PUU virus antigen, designing the ELISA for detection of specific antibodies, developing parameters of the ELISA system, parallel titration of HFRS patients sera by fluorescent antibody technique (FAT) and the new ELISA. For the first time, ELISA based on purified inactivated PUU virus as standard antigen directly absorbed onto immunoplate was developed. Parallel titration of 50 samples from HFRS patients blood sera using FAT and the developed ELISA showed high sensitivity and specificity of this ELISA, with 100% concordance of testing results and significant level of correlation between the titers of specific antibodies in the two assays. The ELISA based on purified inactivated PUU virus as an immunosorbent can be effectively used for HFRS serological diagnosis and for mass seroepidemiological studies.

Biotechnological approaches in the production of plant secondary metabolites for treating human viral diseases: Prospects and challenges

Over the last couple of decades, three highly pathogenic and deadly human coronaviruses have posed dreadful impacts on human life, namely SARS-CoV, MERS-CoV and SARS-CoV-2. In addition, many other viral diseases also affect various aspects of human well-being such as lifestyles and socio-economic conditions. Therefore, research on developing antiviral drugs should be progressively carried out to rapidly prevent or reduce the severity of infection for the current and future emerging infection with pandemic potential. Conventional antiviral drugs have been associated with high cost, toxicity and resistance issues. The use of medicinal plants and their secondary metabolites (SMs) with potential anti-inflammatory properties garners attention as a safer alternative for treating viral diseases. This review discussed various plant SMs with therapeutic potential for treating viral diseases. Due to various factors including low concentrations of the phytocompounds produced, relying on natural systems for producing medically important SMs is not sustainable. Thus, several biotechnology strategies such as metabolic engineering and genetic modification, in vitro production as well as gene editing to enhance the phytochemical compounds are also highlighted. Future perspectives on the potential of plant-based antiviral drugs as well as other strategies to treat viral diseases in humans are also elaborated. Altogether, this review gives a comprehensive view of the pharmaceutical importance of plant SMs as an alternative approach against viral diseases.

Travel surveillance uncovers dengue virus dynamics and introductions in the Caribbean

Dengue is the most prevalent mosquito-borne viral disease in humans, and cases are continuing to rise globally. In particular, islands in the Caribbean have experienced more frequent outbreaks, and all four dengue virus (DENV) serotypes have been reported in the region, leading to hyperendemicity and increased rates of severe disease. However, there is significant variability regarding virus surveillance and reporting between islands, making it difficult to obtain an accurate understanding of the epidemiological patterns in the Caribbean. To investigate this, we used travel surveillance and genomic epidemiology to reconstruct outbreak dynamics, DENV serotype turnover, and patterns of spread within the region from 2009-2022. We uncovered two recent DENV-3 introductions from Asia, one of which resulted in a large outbreak in Cuba, which was previously under-reported. We also show that while outbreaks can be synchronized between islands, they are often caused by different serotypes. Our study highlights the importance of surveillance of infected travelers to provide a snapshot of local introductions and transmission in areas with limited local surveillance and suggests that the recent DENV-3 introductions may pose a major public health threat in the region.

Geographic Disparities in Domestic Pig Population Exposure to Ebola Viruses, Guinea, 2017-2019.

Although pigs are naturally susceptible to Reston virus and experimentally to Ebola virus (EBOV), their role in Orthoebolavirus ecology remains unknown. We tested 888 serum samples collected from pigs in Guinea during 2017-2019 (between the 2013-16 epidemic and its resurgence in 2021) by indirect ELISA against the EBOV nucleoprotein. We identified 2 hotspots of possible pig exposure by IgG titer levels: the northern coast had 48.7% of positive serum samples (37/76), and Forest Guinea, bordering Sierra Leone and Liberia, where the virus emerged and reemerged, had 50% of positive serum samples (98/196). The multitarget Luminex approach confirms ELISA results against Ebola nucleoprotein and highlights cross-reactivities to glycoprotein of EBOV, Reston virus, and Bundibugyo virus. Those results are consistent with previous observations of the circulation of Orthoebolavirus species in pig farming regions in Sierra Leone and Ghana, suggesting potential risk for Ebola virus disease in humans, especially in Forest Guinea.

In silico antiviral properties of Spirulina platensis phycobiliprotein and phycobilin as natural inhibitor for SARS-CoV-2

The global pandemic COVID-19 in 2019 has led to a continued search for promising potential molecules to combat human viral diseases. An in silico strategy was attempted to narrow down the discovery of potentially active compounds for drug candidates. It has been reported that several bioactive molecules in cyanobacteria have displayed antiviral activities. This study aimed to investigate the potential of phycobiliprotein and phycobilin from Spirulina platensis, a nutrient-dense cyanobacterium, as anti-SARS-CoV-2 using in silico assessment. The docking of the drug candidate was performed by targeting three important SARS-CoV-2 protein receptors; main protease (Mpro), receptor binding domain (RBD), and RNA-dependent RNA polymerase (RdRp). The results revealed that phycoerythrobilin showed the high binding affinity against all target proteins, specially towards RBD and RdRp proteins that exceeded the chloroquine as well as remdesivir as control inhibitors. Inferiorly, phycocyanobilin showed also similar triple inhibitory effect against the three main proteins though lower affinity at SARS-CoV-2 Mpro when compared to inhibitor nelfinavir. Pharmacokinetics analysis was conducted for both compounds using SwissADME and pkCSM to provide the properties of bioactive candidates when designed as a drug. The molecular physicochemical evaluation showed that both phycocyanobilin and phycoerythrobilin have fulfilled the Lipinski's rule of five, suggesting that both molecules have drug-like properties and could act like a drug. Based on the simulation results, it can be concluded that phycobiliprotein and phycobilin from Spirulina platensis have the potential to be developed as source for the development of novel natural antiviral agent.

Therapeutic Potential of Carica papaya Linn.: A Comprehensive Review of Its Pharmacological Properties and Health Benefits, with Emphasis on Dengue Fever Healing

For thousands of years, people have used various plant products, foods, spices, and herbs to treat and prevent illnesses. Sri Lankans have been using traditional and folk medicine to satisfy their basic health needs from the earliest days. Carica papaya Linn. (Caricaceae) is a commercially grown exotic plant in Sri Lanka. The entire plant, including the fruits both ripened and green, leaves, roots, peel, seed, and pulp, was used as medicine in traditional medicinal systems. Plant parts of Carica papaya Linn. were frequently used by ancient Sri Lankans to treat diabetes mellitus, hypertension, cancer, dengue fever, skin infections, renal disorders, and infections caused by bacteria, fungi, parasites, and viruses. Dengue fever is the most prevalent and significant arthropod-borne viral disease in humans, and it is extensively spread throughout Sri Lanka. Carica papaya Linn. extracts have been used to treat dengue patients to recover from its complications, which include thrombocytopenia, hemolysis, and leukopenia. Studies reveal that the papaya leaf extract can neutralize plasma with the dengue virus, reduce platelet aggregation, and increase the production of the enzyme ALOX12, which promotes platelet production. Moreover, the extract also upregulates the platelet-activating factor receptor (PTAFR) gene and inhibits serine proteases NS2B and NS3 involved in dengue virus replication. In this review, we have discussed extensively the ethnomedicinal and pharmacological properties of Carica papaya while highlighting its remarkable potency in healing dengue.

Emerging zoonotic viral diseases and preventive strategies with Islamic perspectives of halal foods

There are several emerging zoonotic viral diseases associated with wildlife or non-wildlife food that arise with the passage of time. Different pathogenic strains with advanced mutational changes results in severe pathogenicity in respective hosts either animals or humans. The viability in human host employs the certainty of transmission from animals. Most of the viral diseases in humans caused by direct close contact between animals or indirectly through intermediate hosts. Many of the coronaviral diseases spread by bats specie and its reservoirs. Moreover, the consumption of other wildlife animals common in certain regions of world escalate the potential risk for gaining various zoonotic viral ailments. On the other hand, the Islamic norms for food consumption remarkably reduces the risk of these diseases by devouring the Halal (lawful) or Tayyab foods. The xenobiotic transformations in animals also illustrates the prohibition of haram (unlawful) food consumption. Humans with compromised immune system in elderly or suffering from chronic diseases can easily adopt these viral diseases and thus may prone to lethality. One of the emerging zoonotic viral diseases involve COVID-19 caused by novel β-coronavirus (nCov) transmission has been suspected in Wuhan wildlife market that also have origin of bat reservoirs as natural host based on virus genome sequencing results and evolutionary analysis. Measures to prevent or reduce transmission should be especially implemented in populations at greater risk.

Tick-borne encephalitis infections without CNS involvement: An observational study in Latvia, 2007-2022.

Tick-borne encephalitis (TBE) is a human viral infectious disease involving the central nervous system (CNS). It is caused by the tick-borne encephalitis virus (TBEV). At present, there is very limited information regarding the clinical importance and health burden of TBE infections without signs of CNS inflammation. Moreover, such cases are omitted from official TBE surveillances and there are no reports of population-based studies. A nationwide population-based study was conducted in Latvia by intensively searching for symptomatic TBEV infections recorded in outpatient and hospital settings between 2007 and 2022. In total, 4,124 symptomatic TBEV infections were identified, of which 823 (20.0%) had no CNS involvement. Despite the lack of neurological symptoms, non-CNS TBE patients still experienced severe health conditions that required management in a hospital setting for a median duration of 7 days. Furthermore, lumbar puncture information was available for 708 of these patients, with 100 (14.1%) undergoing the procedure, suggesting a high suspicion of CNS involvement. Clearly, non-CNS TBE has the potential to negatively impact the health of patients. The actual burden of non-CNS TBEV cases may be higher than we think as these cases are omitted from official TBE surveillances and are challenging to recognize.

Knowledge, Attitude, and Perception regarding Dengue Prevention and Control in Puducherry – A Community-based Cross-sectional Study

Abstract Context: Dengue is one of the most dreadful viral diseases of humans, with over half of the world’s population living in the areas of risk. Aims: The aim of this study was to determine the level of knowledge, awareness, and practice of preventive measures regarding dengue fever among people living in Puducherry. Settings and Design: A community-based cross-sectional study was carried out among the individuals residing in Puducherry in the field practice areas of our tertiary care hospital. Subjects and Methods: The study was conducted for a period of 3 months from August to October 2023. The study population included residents of Puducherry in the field practice area of our tertiary care hospital based on the inclusion and exclusion criteria. A simple random sampling method was used with an estimated sample size of 285. Statistical Analysis Used: Continuous variables were presented in the form of frequency and proportion. Chi-square test was used for determining the association. Results: Out of 285 participants, 252 had good knowledge, and 33 had poor knowledge. 94.4% had good attitude and 5.6% had poor attitude. 62.1% (177) had good perception and 108 (37.9) had poor perception. The study showed a significant association between age and knowledge (P = 0.003) regarding dengue awareness. Socioeconomic status of the participants had a significant association with the attitude (P < 0.001). Conclusions: Appropriate use of information education and communication by involving mass media and social network and inclusion of environmental sanitation to the primary school curriculum can go a long way in creating awareness and decreasing the dengue burden in the community.

Environmental problems of insecticides application in agriculture to combat blood-sucking dipterous insects

This article discusses scientific studies that indicate the negative factors that arise when using insecticides to combat blood-sucking diptera insects. Diptera insects are carriers of viral diseases of humans and animals, such as anthrax, tularemia, diphtheria, anaplasmosis and others. They also contribute to the transmission of invasive diseases, which further increases their harmfulness. To reduce the economic damage caused by insects, various preventive and extermination measures are used, where the main method is the use of insecticides. However, more and more studies point to the negative impact of chemical insecticides on the environment and non-target organisms, including humans. This may indicate that the scale of the use of insecticidal drugs is far ahead of the study of the consequences associated with their use. Therefore, the current situation requires a reassessment of this approach to pest control. To collect information, a search was made for scientific papers in Russian and foreign sources on the negative consequences of the use of insecticides and alternative approaches to pest control. Research in this area is necessary to develop effective and environmentally friendly pest control strategies and minimize losses in animal husbandry. To overcome the environmental problems associated with the use of insecticides in animal husbandry, an integrated approach is considered, which includes a variety of tactics based on alternative methods of disinsection and combining mechanical, cultural, biological and chemical methods of pest control while minimizing the use of insecticides.

Mapping the potential distribution of the principal vector of Crimean-Congo haemorrhagic fever virus Hyalomma marginatum in the Old World.

Crimean-Congo haemorrhagic fever (CCHF) is the most widely distributed tick-borne viral disease in humans and is caused by the Crimean-Congo haemorrhagic fever virus (CCHFV). The virus has a broader distribution, expanding from western China and South Asia to the Middle East, southeast Europe, and Africa. The historical known distribution of the CCHFV vector Hyalomma marginatum in Europe includes most of the Mediterranean and the Balkan countries, Ukraine, and southern Russia. Further expansion of its potential distribution may have occurred in and out of the Mediterranean region. This study updated the distributional map of the principal vector of CCHFV, H. marginatum, in the Old World using an ecological niche modeling approach based on occurrence records from the Global Biodiversity Information Facility (GBIF) and a set of covariates. The model predicted higher suitability of H. marginatum occurrences in diverse regions of Africa and Asia. Furthermore, the model estimated the environmental suitability of H. marginatum across Europe. On a continental scale, the model anticipated a widespread potential distribution encompassing the southern, western, central, and eastern parts of Europe, reaching as far north as the southern regions of Scandinavian countries. The distribution of H. marginatum also covered countries across Central Europe where the species is not autochthonous. All models were statistically robust and performed better than random expectations (p < 0.001). Based on the model results, climatic conditions could hamper the successful overwintering of H. marginatum and their survival as adults in many regions of the Old World. Regular updates of the models are still required to continually assess the areas at risk using up-to-date occurrence and climatic data in present-day and future conditions.

The intriguing phenomenon of cross-kingdom infections of plant and insect viruses to fungi: Can other animal viruses also cross-infect fungi?

Fungi are highly widespread and commonly colonize multicellular organisms that live in natural environments. Notably, studies on viruses infecting plant-associated fungi have revealed the interesting phenomenon of the cross-kingdom transmission of viruses and viroids from plants to fungi. This implies that fungi, in addition to absorbing water, nutrients, and other molecules from the host, can acquire intracellular parasites that reside in the host. These findings further suggest that fungi can serve as suitable alternative hosts for certain plant viruses and viroids. Given the frequent coinfection of fungi and viruses in humans/animals, the question of whether fungi can also acquire animal viruses and serve as their hosts is very intriguing. In fact, the transmission of viruses from insects to fungi has been observed. Furthermore, the common release of animal viruses into the extracellular space (viral shedding) could potentially facilitate their acquisition by fungi. Investigations of the cross-infection of animal viruses in fungi may provide new insights into the epidemiology of viral diseases in humans and animals.

Recovery of complete genome sequences of Crimean-Congo haemorrhagic fever virus (CCHFV) directly from clinical samples: A comparative study between targeted enrichment and metagenomic approaches

Crimean-Congo haemorrhagic fever (CCHF) is the most prevalent human tick-borne viral disease, endemic to the Balkans, Africa, Middle East and Asia. There are currently no licensed vaccines or effective antivirals against CCHF. CCHF virus (CCHFV) has a negative sense segmented tripartite RNA genome consisting of the small (S), medium (M) and large (L) segments. Depending on the segment utilised for genetic affiliation, there are up to 7 circulating lineages of CCHFV. The current lack of geographical representation of CCHFV sequences in various repositories highlights a requirement for increased CCHFV sequencing capabilities in endemic regions. We have optimised and established a multiplex PCR tiling methodology for the targeted enrichment of complete genomes of Europe 1 CCHFV lineage directly from clinical samples and compared its performance to a non-targeted enrichment approach on both short-read and long-read sequencing platforms. We have found a statistically significant increase in mapped viral sequencing reads produced with our targeted enrichment approach. This has allowed us to recover near complete S segment sequences and above 90% of the M and L segment sequences for samples with Ct values as high as 31.3. This study demonstrates the superiority of a targeted enrichment approach for recovery of CCHFV genomic sequences from samples with low virus titre. CCHFV is an important vector-borne human pathogen with wide geographical distribution. The validated methodology reported here adds value to front-line public health laboratories employing genomic sequencing for CCHFV Europe 1 lineage surveillance, particularly in the Balkan and Middle Eastern territories currently monitoring the spread of the pathogen. Tracking the genomic evolution of the virus across regions improves risk assessment and directly informs the development of diagnostics, therapeutics, and vaccines.

Aedes aegypti Argonaute 2 controls arbovirus infection and host mortality

Ae. aegypti mosquitoes transmit some of the most important human viral diseases that are responsible for a significant public health burden worldwide. The small interfering RNA (siRNA) pathway is considered the major antiviral defense system in insects. Here we show that siRNA pathway disruption by CRISPR/Cas9-based Ago2 knockout impaired the mosquitoes’ ability to degrade arbovirus RNA leading to hyper-infection accompanied by cell lysis and tissue damage. Ago2 disruption impaired DNA repair mechanisms and the autophagy pathway by altering histone abundance. This compromised DNA repair and removal of damaged cellular organelles and dysfunctional aggregates promoted mosquito death. We also report that hyper-infection of Ago2 knockout mosquitoes stimulated a broad-spectrum antiviral immunity, including apoptosis, which may counteract infection. Taken together, our studies reveal novel roles for Ago2 in protecting mosquitoes from arbovirus infection and associated death.

Persistence of immunological memory as a potential correlate of long-term, vaccine-induced protection against Ebola virus disease in humans.

In the absence of clinical efficacy data, vaccine protective effect can be extrapolated from animals to humans, using an immunological biomarker in humans that correlates with protection in animals, in a statistical approach called immunobridging. Such an immunobridging approach was previously used to infer the likely protective effect of the heterologous two-dose Ad26.ZEBOV, MVA-BN-Filo Ebola vaccine regimen. However, this immunobridging model does not provide information on how the persistence of the vaccine-induced immune response relates to durability of protection in humans. In both humans and non-human primates, vaccine-induced circulating antibody levels appear to be very stable after an initial phase of contraction and are maintained for at least 3.8 years in humans (and at least 1.3 years in non-human primates). Immunological memory was also maintained over this period, as shown by the kinetics and magnitude of the anamnestic response following re-exposure to the Ebola virus glycoprotein antigen via booster vaccination with Ad26.ZEBOV in humans. In non-human primates, immunological memory was also formed as shown by an anamnestic response after high-dose, intramuscular injection with Ebola virus, but was not sufficient for protection against Ebola virus disease at later timepoints due to a decline in circulating antibodies and the fast kinetics of disease in the non-human primates model. Booster vaccination within three days of subsequent Ebola virus challenge in non-human primates resulted in protection from Ebola virus disease, i.e. before the anamnestic response was fully developed. Humans infected with Ebola virus may benefit from the anamnestic response to prevent disease progression, as the incubation time is longer and progression of Ebola virus disease is slower as compared to non-human primates. Therefore, the persistence of vaccine-induced immune memory could be considered as a potential correlate of long-term protection against Ebola virus disease in humans, without the need for a booster.