Viruses of the Bunya- and Togaviridae families: potential as bioterrorism agents and means of control

Comprehensive Assessment of Inactivation Methods for Madariaga Virus

The Eastern Equine Encephalitis Virus (EEEV) is an emerging public health threat, with the number of reported cases in the US increasing in recent years. EEEV is a BSL3 pathogen, and the North American strain is a US Federal Select Agent (SA). These restrictions make experiments with EEEV difficult to perform, as high-tech equipment is often unavailable in BSL3 spaces and due to concerns about generating aerosols during manipulations. Therefore, a range of inactivation methods suitable for different downstream analysis methods are essential for advancing research on EEEV. We used heat, chemical, and ultraviolet (UV)-based methods for the inactivation of infected cells and supernatants infected with the non-select agent Madariaga virus (MADV). Although the MADV and EEEV strains are genetically distinct, differing by 8-11% at the amino acid level, they are expected to be similarly susceptible to various inactivation methods. We determined the following to be effective methods of inactivation: heat, TRIzol LS, 4% PFA, 10% formalin, and UV radiation for infected supernatants; TRIzol, 2.5% SDS with BME, 0.2% NP40, 4% PFA, and 10% formalin for infected cells. Our results have the potential to expand the types and complexity of experiments and analyses performed by EEEV researchers.

Integrated control strategies for dengue, Zika, and Chikungunya virus infections

Arboviruses are a major threat to public health in tropical regions, encompassing over 534 distinct species, with 134 capable of causing diseases in humans. These viruses are transmitted through arthropod vectors that cause symptoms such as fever, headache, joint pains, and rash, in addition to more serious cases that can lead to death. Among the arboviruses, dengue virus stands out as the most prevalent, annually affecting approximately 16.2 million individuals solely in the Americas. Furthermore, the re-emergence of the Zika virus and the recurrent outbreaks of chikungunya in Africa, Asia, Europe, and the Americas, with one million cases reported annually, underscore the urgency of addressing this public health challenge. In this manuscript we discuss the epidemiology, viral structure, pathogenicity and integrated control strategies to combat arboviruses, and the most used tools, such as vaccines, monoclonal antibodies, treatment, etc., in addition to presenting future perspectives for the control of arboviruses. Currently, specific medications for treating arbovirus infections are lacking, and symptom management remains the primary approach. However, promising advancements have been made in certain treatments, such as Chloroquine, Niclosamide, and Isatin derivatives, which have demonstrated notable antiviral properties against these arboviruses in vitro and in vivo experiments. Additionally, various strategies within vector control approaches have shown significant promise in reducing arbovirus transmission rates. These encompass public education initiatives, targeted insecticide applications, and innovative approaches like manipulating mosquito bacterial symbionts, such as Wolbachia. In conclusion, combatting the global threat of arbovirus diseases needs a comprehensive approach integrating antiviral research, vaccination, and vector control. The continued efforts of research communities, alongside collaborative partnerships with public health authorities, are imperative to effectively address and mitigate the impact of these arboviral infections on public health worldwide.

Vaccine elicitation and structural basis for antibody protection against alphaviruses

Alphaviruses are RNA viruses that represent emerging public health threats. To identify protective antibodies, we immunized macaques with a mixture of western, eastern, and Venezuelan equine encephalitis virus-like particles (VLPs), a regimen that protects against aerosol challenge with all three viruses. Single- and triple-virus-specific antibodies were isolated, and we identified 21 unique binding groups. Cryo-EM structures revealed that broad VLP binding inversely correlated with sequence and conformational variability. One triple-specific antibody, SKT05, bound proximal to the fusion peptide and neutralized all three Env-pseudotyped encephalitic alphaviruses by using different symmetry elements for recognition across VLPs. Neutralization in other assays (e.g., chimeric Sindbis virus) yielded variable results. SKT05 bound backbone atoms of sequence-diverse residues, enabling broad recognition despite sequence variability; accordingly, SKT05 protected mice against Venezuelan equine encephalitis virus, chikungunya virus, and Ross River virus challenges. Thus, a single vaccine-elicited antibody can protect in vivo against a broad range of alphaviruses.

A molecular understanding of alphavirus entry and antibody protection

Alphaviruses are arthropod-transmitted RNA viruses that cause epidemics of human infection and disease on a global scale. These viruses are classified as either arthritogenic or encephalitic based on their genetic relatedness and the clinical syndromes they cause. Although there are currently no approved therapeutics or vaccines against alphaviruses, passive transfer of monoclonal antibodies confers protection in animal models. This Review highlights recent advances in our understanding of the host factors required for alphavirus entry, the mechanisms of action by which protective antibodies inhibit different steps in the alphavirus infection cycle and candidate alphavirus vaccines currently under clinical evaluation that focus on humoral immunity. A comprehensive understanding of alphavirus entry and antibody-mediated protection may inform the development of new classes of countermeasures for these emerging viruses.

Structural constraints link differences in neutralization potency of human anti-Eastern equine encephalitis virus monoclonal antibodies

Selection and development of monoclonal antibody (mAb) therapeutics against pathogenic viruses depends on certain functional characteristics. Neutralization potency, or the half-maximal inhibitory concentration (IC50) values, is an important characteristic of candidate therapeutic antibodies. Structural insights into the bases of neutralization potency differences between antiviral neutralizing mAbs are lacking. In this report, we present cryo-electron microscopy (EM) reconstructions of three anti-Eastern equine encephalitis virus (EEEV) neutralizing human mAbs targeting overlapping epitopes on the E2 protein, with greater than 20-fold differences in their respective IC50 values. From our structural and biophysical analyses, we identify several constraints that contribute to the observed differences in the neutralization potencies. Cryo-EM reconstructions of EEEV in complex with these Fab fragments reveal structural constraints that dictate intravirion or intervirion cross-linking of glycoprotein spikes by their IgG counterparts as a mechanism of neutralization. Additionally, we describe critical features for the recognition of EEEV by these mAbs including the epitope-paratope interaction surface, occupancy, and kinetic differences in on-rate for binding to the E2 protein. Each constraint contributes to the extent of EEEV inhibition for blockade of virus entry, fusion, and/or egress. These findings provide structural and biophysical insights into the differences in mechanism and neutralization potencies of these antibodies, which help inform rational design principles for candidate vaccines and therapeutic antibodies for all icosahedral viruses.

Advances in the Development of Small Molecule Antivirals against Equine Encephalitic Viruses

Venezuelan, western, and eastern equine encephalitic alphaviruses (VEEV, WEEV, and EEEV, respectively) are arboviruses that are highly pathogenic to equines and cause significant harm to infected humans. Currently, human alphavirus infection and the resulting diseases caused by them are unmitigated due to the absence of approved vaccines or therapeutics for general use. These circumstances, combined with the unpredictability of outbreaks-as exemplified by a 2019 EEE surge in the United States that claimed 19 patient lives-emphasize the risks posed by these viruses, especially for aerosolized VEEV and EEEV which are potential biothreats. Herein, small molecule inhibitors of VEEV, WEEV, and EEEV are reviewed that have been identified or advanced in the last five years since a comprehensive review was last performed. We organize structures according to host- versus virus-targeted mechanisms, highlight cellular and animal data that are milestones in the development pipeline, and provide a perspective on key considerations for the progression of compounds at early and later stages of advancement.

A Historical Review of Military Medical Strategies for Fighting Infectious Diseases: From Battlefields to Global Health

The environmental conditions generated by war and characterized by poverty, undernutrition, stress, difficult access to safe water and food as well as lack of environmental and personal hygiene favor the spread of many infectious diseases. Epidemic typhus, plague, malaria, cholera, typhoid fever, hepatitis, tetanus, and smallpox have nearly constantly accompanied wars, frequently deeply conditioning the outcome of battles/wars more than weapons and military strategy. At the end of the nineteenth century, with the birth of bacteriology, military medical researchers in Germany, the United Kingdom, and France were active in discovering the etiological agents of some diseases and in developing preventive vaccines. Emil von Behring, Ronald Ross and Charles Laveran, who were or served as military physicians, won the first, the second, and the seventh Nobel Prize for Physiology or Medicine for discovering passive anti-diphtheria/tetanus immunotherapy and for identifying mosquito Anopheline as a malaria vector and plasmodium as its etiological agent, respectively. Meanwhile, Major Walter Reed in the United States of America discovered the mosquito vector of yellow fever, thus paving the way for its prevention by vector control. In this work, the military relevance of some vaccine-preventable and non-vaccine-preventable infectious diseases, as well as of biological weapons, and the military contributions to their control will be described. Currently, the civil-military medical collaboration is getting closer and becoming interdependent, from research and development for the prevention of infectious diseases to disasters and emergencies management, as recently demonstrated in Ebola and Zika outbreaks and the COVID-19 pandemic, even with the high biocontainment aeromedical evacuation, in a sort of global health diplomacy.

Neutralizing antibodies protect mice against Venezuelan equine encephalitis virus aerosol challenge

Venezuelan equine encephalitis virus (VEEV) remains a risk for epidemic emergence or use as an aerosolized bioweapon. To develop possible countermeasures, we isolated VEEV-specific neutralizing monoclonal antibodies (mAbs) from mice and a human immunized with attenuated VEEV strains. Functional assays and epitope mapping established that potently inhibitory anti-VEEV mAbs bind distinct antigenic sites in the A or B domains of the E2 glycoprotein and block multiple steps in the viral replication cycle including attachment, fusion, and egress. A 3.2-Å cryo-electron microscopy reconstruction of VEEV virus-like particles bound by a human Fab suggests that antibody engagement of the B domain may result in cross-linking of neighboring spikes to prevent conformational requirements for viral fusion. Prophylaxis or postexposure therapy with these mAbs protected mice against lethal aerosol challenge with VEEV. Our study defines functional and structural mechanisms of mAb protection and suggests that multiple antigenic determinants on VEEV can be targeted for vaccine or antibody-based therapeutic development.

Cross-Strain Neutralizing and Protective Monoclonal Antibodies against EEEV or WEEV

The three encephalitic alphaviruses, namely, the Venezuelan, eastern, and western equine encephalitis viruses (VEEV, EEEV, and WEEV), are classified by the Centers for Disease Control and Prevention (CDC) as biothreat agents. Currently, no licensed medical countermeasures (MCMs) against these viruses are available for humans. Neutralizing antibodies (NAbs) are fast-acting and highly effective MCMs for use in both pre- and post-exposure settings against biothreat agents. While significant work has been done to identify anti-VEEV NAbs, less has been done to identify NAbs against EEEV and WEEV. In order to develop anti-EEEV or -WEEV NAbs, mice were immunized using complementary strategies with a variety of different EEEV or WEEV immunogens to maximize the generation of NAbs to each of these viruses. Of the hybridomas generated, three anti-EEEV and seven anti-WEEV monoclonal antibodies were identified with in vitro neutralization activity. The most potent neutralizers (two anti-EEEV NAbs and three anti-WEEV NAbs) were further evaluated for neutralization activity against additional strains of EEEV, a single strain of Madariaga virus (formerly South American EEEV), or WEEV. Of these, G1-2-H4 and G1-4-C3 neutralized all three EEEV strains and the Madariaga virus strain, whereas G8-2-H9 and 12 WA neutralized six out of eight WEEV strains. To determine the protective efficacy of these NAbs, the five most potent neutralizers were evaluated in respective mouse aerosol challenge models. All five NAbs demonstrated various levels of protection when administered at doses of 2.5 mg/kg or 10 mg/kg 24 h before the respective virus exposure via the aerosol route. Of these, anti-EEEV NAb G1-4-C3 and anti-WEEV NAb 8C2 provided 100% protection at both doses and all surviving mice were free of clinical signs throughout the study. Additionally, no virus was detected in the brain 14 days post virus exposure. Taken together, efficacious NAbs were developed that demonstrate the potential for the development of cross-strain antibody-based MCMs against EEEV and WEEV infections.

Exposing cryptic epitopes on the Venezuelan equine encephalitis virus E1 glycoprotein prior to treatment with alphavirus cross-reactive monoclonal antibody allows blockage of replication early in infection

Eastern equine encephalitis virus (EEEV), western equine encephalitis virus (WEEV) and Venezuelan equine encephalitis virus (VEEV) can cause fatal encephalitis in humans and equids. Some MAbs to the E1 glycoprotein are known to be cross-reactive, weakly neutralizing in vitro but can protect from disease in animal models. We investigated the mechanism of neutralization of VEEV infection by the broadly cross-reactive E1-specific MAb 1A4B-6. 1A4B-6 protected 3-week-old Swiss Webster mice prophylactically from lethal VEEV challenge. Likewise, 1A4B-6 inhibited virus growth in vitro at a pre-attachment step after virions were incubated at 37 °C and inhibited virus-mediated cell fusion. Amino acid residue N100 in the fusion loop of E1 protein was identified as critical for binding. The potential to elicit broadly cross-reactive MAbs with limited virus neutralizing activity in vitro but that can inhibit virus entry and protect animals from infection merits further exploration for vaccine and therapeutic developmental research.

Therapeutic alphavirus cross-reactive E1 human antibodies inhibit viral egress

Alphaviruses cause severe arthritogenic or encephalitic disease. The E1 structural glycoprotein is highly conserved in these viruses and mediates viral fusion with host cells. However, the role of antibody responses to the E1 protein in immunity is poorly understood. We isolated E1-specific human monoclonal antibodies (mAbs) with diverse patterns of recognition for alphaviruses (ranging from Eastern equine encephalitis virus [EEEV]-specific to alphavirus cross-reactive) from survivors of natural EEEV infection. Antibody binding patterns and epitope mapping experiments identified differences in E1 reactivity based on exposure of epitopes on the glycoprotein through pH-dependent mechanisms or presentation on the cell surface prior to virus egress. Therapeutic efficacy in vivo of these mAbs corresponded with potency of virus egress inhibition in vitro and did not require Fc-mediated effector functions for treatment against subcutaneous EEEV challenge. These studies reveal the molecular basis for broad and protective antibody responses to alphavirus E1 proteins.

Large-Scale International Validation of an Indirect ELISA Based on Recombinant Nucleocapsid Protein of Rift Valley Fever Virus for the Detection of IgG Antibody in Domestic Ruminants

Diagnostic performance of an indirect enzyme-linked immunosorbent assay (I-ELISA) based on a recombinant nucleocapsid protein (rNP) of the Rift Valley fever virus (RVFV) was validated for the detection of the IgG antibody in sheep (n = 3367), goat (n = 2632), and cattle (n = 3819) sera. Validation data sets were dichotomized according to the results of a virus neutralization test in sera obtained from RVF-endemic (Burkina Faso, Democratic Republic of Congo, Mozambique, Senegal, Uganda, and Yemen) and RVF-free countries (France, Poland, and the USA). Cut-off values were defined using the two-graph receiver operating characteristic analysis. Estimates of the diagnostic specificity of the RVFV rNP I-ELISA in animals from RVF-endemic countries ranged from 98.6% (cattle) to 99.5% (sheep) while in those originating from RVF-free countries, they ranged from 97.7% (sheep) to 98.1% (goats). Estimates of the diagnostic sensitivity in ruminants from RVF-endemic countries ranged from 90.7% (cattle) to 100% (goats). The results of this large-scale international validation study demonstrate the high diagnostic accuracy of the RVFV rNP I-ELISA. Standard incubation and inactivation procedures evaluated did not have an adverse effect on the detectable levels of the anti-RVFV IgG in ruminant sera and thus, together with recombinant antigen-based I-ELISA, provide a simple, safe, and robust diagnostic platform that can be automated and carried out outside expensive bio-containment facilities. These advantages are particularly important for less-resourced countries where there is a need to accelerate and improve RVF surveillance and research on epidemiology as well as to advance disease control measures.

The Structural Biology of Eastern Equine Encephalitis Virus, an Emerging Viral Threat

Alphaviruses are arboviruses that cause arthritis and encephalitis in humans. Eastern Equine Encephalitis Virus (EEEV) is a mosquito-transmitted alphavirus that is implicated in severe encephalitis in humans with high mortality. However, limited insights are available into the fundamental biology of EEEV and residue-level details of its interactions with host proteins. In recent years, outbreaks of EEEV have been reported mainly in the United States, raising concerns about public safety. This review article summarizes recent advances in the structural biology of EEEV based mainly on single-particle cryogenic electron microscopy (cryoEM) structures. Together with functional analyses of EEEV and related alphaviruses, these structural investigations provide clues to how EEEV interacts with host proteins, which may open avenues for the development of therapeutics.

Epidemiological Aspects of Crimean-Congo Hemorrhagic Fever in Western Europe: What about the Future?

Crimean-Congo hemorrhagic fever virus (CCHFV) is an arthropod-borne virus (arbovirus), mainly transmitted by ticks, belonging to the genus Orthonairovirus (family Nairoviridae, order Bunyavirales). CCHFV causes a potentially severe, or even fatal, human disease, and it is widely distributed in Africa, Asia, eastern Europe and, more recently, in South-western Europe. Until a few years ago, no cases of Crimean-Congo hemorrhagic fever (CCHF) had been reported in western Europe, with the exception of several travel-associated cases. In 2010, the CCHFV was reported for the first time in South-western Europe when viral RNA was obtained from Hyalomma lusitanicum ticks collected from deer in Cáceres (Spain). Migratory birds from Africa harboring CCHFV-infected ticks and flying to Spain appear to have contributed to the establishment of the virus (genotype III, Africa-3) in this country. In addition, the recent findings in a patient and in ticks from deer and wild boar of viral sequences similar to those from eastern Europe (genotype V, Europe-1), raise the possibility of the introduction of CCHFV into Spain through the animal trade, although the arrival by bird routes cannot be ruled out (Africa-4 has been also recently detected). The seropositive rates of animals detected in regions of South-western Spain suggest an established cycle of tick-host-tick in certain areas, and the segment reassortment detected in the sequenced virus from one patient evidences a high ability to adaptation of the virus. Different ixodid tick genera can be vectors and reservoirs of the virus, although Hyalomma spp. are particularly relevant for its maintenance. This tick genus is common in Mediterranean region but it is currently spreading to new areas, partly due to the climate change and movement of livestock or wild animals. Although to a lesser extent, travels with our pets (and their ticks) may be also a factor to be considered. As a consequence, the virus is expanding from the Balkan region to Central Europe and, more recently, to Western Europe where different genotypes are circulating. Thus, seven human cases confirmed by molecular methods have been reported in Spain from 2016 to August 2020, three of them with a fatal outcome. A One Health approach is essential for the surveillance of fauna and vector populations to assess the risk for humans and animals. We discuss the risk of CCHFV causing epidemic outbreaks in Western Europe.

Development of Rift valley fever encephalitis in rats is mediated by early infection of olfactory epithelium and neuroinvasion across the cribriform plate

The zoonotic emerging Rift Valley fever virus (RVFV) causes sporadic disease in livestock and humans throughout Africa and the Saudi Arabian peninsula. Infection of people with RVFV can occur through mosquito bite or mucosal exposure during butchering or milking of infected livestock. Disease typically presents as a self-limiting fever; however, in rare cases, hepatitis, encephalitis and ocular disease may occur. Recent studies have illuminated the neuropathogenic mechanisms of RVFV in a rat aerosol infection model. Neurological disease in rats is characterized by breakdown of the blood-brain barrier late in infection, infiltration of leukocytes to the central nervous system (CNS) and massive viral replication in the brain. However, the route of RVFV entry into the CNS after inhalational exposure remains unknown. Here, we visualized the entire nasal olfactory route from snout to brain after RVFV infection using RNA in situ hybridization and immunofluorescence microscopy. We found widespread RVFV-infected cells within the olfactory epithelium, across the cribriform plate, and in the glomerular region of the olfactory bulb within 2 days of infection. These results indicate that the olfactory tract is a major route of infection of the brain after inhalational exposure. A better understanding of potential neuroinvasion pathways can support the design of more effective therapeutic regiments for the treatment of neurological disease caused by RVFV.

Serological and molecular study of Crimean-Congo Hemorrhagic Fever Virus in cattle from selected districts in Uganda

BACKGROUND

Crimean-Congo Hemorrhagic Fever (CCHF) is a severe tick-borne viral hemorrhagic disease caused by Crimean-Congo Hemorrhagic Fever Virus (CCHFV) that poses serious public health challenges in many parts of Africa, Europe and Asia.

METHODS

We examined 500 cattle sera samples from five districts for CCHFV antibodies using in-house and commercially available (IDVet) ELISA, Immunofluorescent assay (IFA) and Real-time polymerase chain reaction (RT-PCR).

RESULTS

500 cattle (73.8 % females) were analyzed; CCHFV seropositivity was 12.6 % (n = 63) and 75.0 % (n = 375) with the in-house and IDVet ELISAs, respectively. Seropositivity was associated with geographical location, increasing age, being female, and having a higher tick burden. Twenty four out of the 37 (64.8 %) were seropositive for CCHFV using IFA and all were negative for virus on RT-PCR. The IFA results were more comparable to IDVet (κ_coefficient = 0.88, p = <0.01) than to in-house (κ_coefficient = 0.32, p = 0.02).

CONCLUSIONS

Our study confirmed the presence and high prevalence of anti-CCHF antibodies in cattle based on three methods from all the five study districts, confirming presence and exposure of CCHFV. Given the zoonotic potential for CCHFV, we recommend a multidisciplinary public health surveillance and epidemiology of CCHFV in both animals and humans throughout the country.

Human Antibodies Protect against Aerosolized Eastern Equine Encephalitis Virus Infection

Eastern equine encephalitis virus (EEEV) is one of the most virulent viruses endemic to North America. No licensed vaccines or antiviral therapeutics are available to combat this infection, which has recently shown an increase in human cases. Here, we characterize human monoclonal antibodies (mAbs) isolated from a survivor of natural EEEV infection with potent (<20 pM) inhibitory activity of EEEV. Cryo-electron microscopy reconstructions of two highly neutralizing mAbs, EEEV-33 and EEEV-143, were solved in complex with chimeric Sindbis/EEEV virions to 7.2 Å and 8.3 Å, respectively. The mAbs recognize two distinct antigenic sites that are critical for inhibiting viral entry into cells. EEEV-33 and EEEV-143 protect against disease following stringent lethal aerosol challenge of mice with highly pathogenic EEEV. These studies provide insight into the molecular basis for the neutralizing human antibody response against EEEV and can facilitate development of vaccines and candidate antibody therapeutics.

The emerging tick-borne Crimean-Congo haemorrhagic fever virus: A narrative review

Crimean-Congo Haemorrhagic Fever (CCHF) is an increasingly relevant viral zoonosis caused by the negative-sense single-stranded (ss) RNA Crimean-Congo Haemorrhagic Fever Orthonairovirus (CCHFV) (Nairoviridae family, Bunyavirales order). The viral genome is divided into three segments (L-M-S) of distinct size and functions. The infection is generally mediated by a tick vector, in particular belonging to the Hyalomma genus, and the transmission follows a tick-vertebrate-tick ecologic cycle, with asymptomatic infected animals functioning as reservoirs and amplifiers for CCHFV. Human hosts could be infected primarily through infected ticks or by contact with infected hosts or their body fluids and tissues, also in a nosocomial way and in occupational contexts. Infected symptomatic patients generally manifest a nonspecific illness, which progresses across four stages, with possibly lethal outcomes. Disease outbreaks show a widespread geographic diffusion and a highly variable mortality rate, dramatically peaking in untreated patients. The lack of an adequate animal model and the elevated virus biological risk (only manageable under biosafety level 4 conditions) represent strongly limiting factors for a better characterization of the disease and for the development of specific therapies and vaccines. The present review discusses updated information on CCHFV-related disease, including details about the virus (taxonomy, structure, life cycle, transmission modalities) and considering CCHF pathogenesis, epidemiology and current strategies (diagnostic, therapeutic and preventive).

Biowarfare, bioterrorism and biocrime: A historical overview on microbial harmful applications

Microbial Forensics is a field that continues to grow in interest and application among the forensic community. This review, divided into two sections, covers several topics associated with this new field. The first section presents a historic overview concerning the use of microorganisms (or its product, i.e. toxins) as harmful biological agents in the context of biological warfare (biowarfare), bioterrorism, and biocrime. Each case is illustrated with the examination of case reports that span from prehistory to the present day. The second part of the manuscript is devoted to the role of MF and highlights the necessity to prepare for the pressing threat of the harmful use of biological agents as weapons. Preventative actions, developments within the field to ensure a timely and effective response and are discussed herein.

5,6-Dichloro-2-phenyl-benzotriazoles: New Potent Inhibitors of Orthohantavirus

Orthohantaviruses, previously known as hantaviruses (family Hantaviridae, order Bunyavirales), are emerging zoonoses hosted by different rodent and insectivore species. Orthohantaviruses are transmitted by aerosolized excreta (urine, saliva and feces) of their reservoir hosts. When transmitted to humans, they cause hemorrhagic fever with renal syndrome (HFRS) in Asia and Europe and hantavirus (cardio) pulmonary syndrome (HPS) in the Americas. Clinical studies have shown that early treatments of HFRS patients with ribavirin (RBV) improve prognosis. Nevertheless, there is the need for urgent development of specific antiviral drugs. In the search for new RNA virus inhibitors, we recently identified a series of variously substituted 5,6-dichloro-1(2)-phenyl-1(2)H-benzo[d][1,2,3]triazole derivatives active against the human respiratory syncytial virus (HRSV). Interestingly, several 2-phenyl-benzotriazoles resulted in fairly potent inhibitors of the Hantaan virus in a chemiluminescence focus reduction assay (C-FRA) showing an EC₅₀ = 4–5 µM, ten-fold more active than ribavirin. Currently, there are no FDA approved drugs for the treatment of orthohantavirus infections. Antiviral activities and cytotoxicity profiles suggest that 5,6-dichloro-1(2)-phenyl-1(2)H-benzo[d][1,2,3]triazoles could be promising candidates for further investigation as a potential treatment of hantaviral diseases.

Emerging Tick-Borne Diseases

Increases in tick-borne disease prevalence and transmission are important public health issues. Efforts to control these emerging diseases are frustrated by the struggle to control tick populations and to detect and treat infections caused by the pathogens that they transmit. This review covers tick-borne infectious diseases of nonrickettsial bacterial, parasitic, and viral origins. While tick surveillance and tracking inform our understanding of the importance of the spread and ecology of ticks and help identify areas of risk for disease transmission, the vectors are not the focus of this document. Here, we emphasize the most significant pathogens that infect humans as well as the epidemiology, clinical features, diagnosis, and treatment of diseases that they cause. Although detection via molecular or immunological methods has improved, tick-borne diseases continue to remain underdiagnosed, making the scope of the problem difficult to assess. Our current understanding of the incidence of tick-borne diseases is discussed in this review. An awareness of the diseases that can be transmitted by ticks in specific locations is key to detection and selection of appropriate treatment. As tick-transmitted pathogens are discovered and emerge in new geographic regions, our ability to detect, describe, and understand the growing public health threat must also grow to meet the challenge.

Electrocardiography Abnormalities in Macaques after Infection with Encephalitic Alphaviruses

Eastern (EEEV) and Venezuelan (VEEV) equine encephalitis viruses (EEVs) are related, (+) ssRNA arboviruses that can cause severe, sometimes fatal, encephalitis in humans. EEVs are highly infectious when aerosolized, raising concerns for potential use as biological weapons. No licensed medical countermeasures exist; given the severity/rarity of natural EEV infections, efficacy studies require animal models. Cynomolgus macaques exposed to EEV aerosols develop fever, encephalitis, and other clinical signs similar to humans. Fever is nonspecific for encephalitis in macaques. Electrocardiography (ECG) metrics may predict onset, severity, or outcome of EEV-attributable disease. Macaques were implanted with thermometry/ECG radiotransmitters and exposed to aerosolized EEV. Data was collected continuously, and repeated-measures ANOVA and frequency-spectrum analyses identified differences between courses of illness and between pre-exposure and post-exposure states. EEEV-infected macaques manifested widened QRS-intervals in severely ill subjects post-exposure. Moreover, QT-intervals and RR-intervals decreased during the febrile period. VEEV-infected macaques suffered decreased QT-intervals and RR-intervals with fever onset. Frequency-spectrum analyses revealed differences in the fundamental frequencies of multiple metrics in the post-exposure and febrile periods compared to baseline and confirmed circadian dysfunction. Heart rate variability (HRV) analyses revealed diminished variability post-exposure. These analyses support using ECG data alongside fever and clinical laboratory findings for evaluating medical countermeasure efficacy.

Venezuelan Equine Encephalitis Virus Capsid Implicated in Infection-Induced Cell Cycle Delay in vitro

Venezuelan equine encephalitis virus (VEEV) is a positive sense, single-stranded RNA virus and member of the New World alphaviruses. It causes a biphasic febrile illness that can be accompanied by central nervous system involvement and moderate morbidity in humans and severe mortality in equines. The virus has a history of weaponization, lacks FDA-approved therapeutics and vaccines in humans, and is considered a select agent. Like other RNA viruses, VEEV replicates in the cytoplasm of infected cells and eventually induces apoptosis. The capsid protein, which contains a nuclear localization and a nuclear export sequence, induces a shutdown of host transcription and nucleocytoplasmic trafficking. Here we show that infection with VEEV causes a dysregulation of cell cycling and a delay in the G₀/G₁ phase in Vero cells and U87MG astrocytes. Cells infected with VEEV encoding a capsid NLS mutant or treated with the capsid-importin α interaction inhibitor G281-1485 were partially rescued from this cell cycle dysregulation. Pathway analysis of previously published RNA-sequencing data from VEEV infected U87MG astrocytes identified alterations of canonical pathways involving cell cycle, checkpoint regulation, and proliferation. Multiple cyclins including cyclin D1, cyclin A2 and cyclin E2 and other regulators of the cell cycle were downregulated in infected cells in a capsid NLS dependent manner. Loss of Rb phosphorylation, which is a substrate for cyclin/cdk complexes was also observed. These data demonstrate the importance of capsid nuclear localization and/or importin α binding for inducing cell cycle arrest and transcriptional downregulation of key cell cycle regulators.

Selection of Single-Domain Antibodies towards Western Equine Encephalitis Virus

In this work, we describe the selection and characterization of single-domain antibodies (sdAb) towards the E2/E3E2 envelope protein of the Western equine encephalitis virus (WEEV). Our purpose was to identify novel recognition elements which could be used for the detection, diagnosis, and perhaps treatment of western equine encephalitis (WEE). To achieve this goal, we prepared an immune phage display library derived from the peripheral blood lymphocytes of a llama that had been immunized with an equine vaccine that includes killed WEEV (West Nile Innovator + VEWT). This library was panned against recombinant envelope (E2/E3E2) protein from WEEV, and seven representative sdAb from the five identified sequence families were characterized. The specificity, affinity, and melting point of each sdAb was determined, and their ability to detect the recombinant protein in a MagPlex sandwich immunoassay was confirmed. Thus, these new binders represent novel recognition elements for the E2/E3E2 proteins of WEEV that are available to the research community for further investigation into their applicability for use in the diagnosis or treatment of WEE.

Lipid-Coated Mesoporous Silica Nanoparticles for the Delivery of the ML336 Antiviral to Inhibit Encephalitic Alphavirus Infection

Venezuelan equine encephalitis virus (VEEV) poses a major public health risk due to its amenability for use as a bioterrorism agent and its severe health consequences in humans. ML336 is a recently developed chemical inhibitor of VEEV, shown to effectively reduce VEEV infection in vitro and in vivo. However, its limited solubility and stability could hinder its clinical translation. To overcome these limitations, lipid-coated mesoporous silica nanoparticles (LC-MSNs) were employed. The large surface area of the MSN core promotes hydrophobic drug loading while the liposome coating retains the drug and enables enhanced circulation time and biocompatibility, providing an ideal ML336 delivery platform. LC-MSNs loaded 20 ± 3.4 μg ML336/mg LC-MSN and released 6.6 ± 1.3 μg/mg ML336 over 24 hours. ML336-loaded LC-MSNs significantly inhibited VEEV in vitro in a dose-dependent manner as compared to unloaded LC-MSNs controls. Moreover, cell-based studies suggested that additional release of ML336 occurs after endocytosis. In vivo safety studies were conducted in mice, and LC-MSNs were not toxic when dosed at 0.11 g LC-MSNs/kg/day for four days. ML336-loaded LC-MSNs showed significant reduction of brain viral titer in VEEV infected mice compared to PBS controls. Overall, these results highlight the utility of LC-MSNs as drug delivery vehicles to treat VEEV.

Repurposed FDA-Approved drug sorafenib reduces replication of Venezuelan equine encephalitis virus and other alphaviruses

The New World alphaviruses -Venezuelan, eastern, and western equine encephalitis viruses (VEEV, EEEV, and WEEV respectively) - cause a febrile disease that is often lethal in equines and children and leads to long-term neurological sequelae in survivors. Endemic to the Americas, epizootic outbreaks of the three viruses occur sporadically in the continental United States. All three viruses aerosolize readily, replicate to high titers in cell culture, and have low infectious doses. Additionally, there are no FDA-approved vaccines or therapeutics for human use. To address the therapeutic gap, a high throughput assay utilizing a luciferase reporter virus, TC83-luc, was performed to screen a library of commercially available, FDA-approved drugs for antiviral activity. From a group of twenty compounds found to significantly decrease luminescence, the carcinoma therapeutic sorafenib inhibited replication of VEEV-TC83 and TrD in vitro. Additionally, sorafenib inhibited replication of EEEV and two Old World alphaviruses, Sindbis virus and chikungunya virus, at 8 and 16 h post-infection. Sorafenib caused no toxicity in Vero cells, and coupled with a low EC₅₀ value, yielded a selectivity index of >19. Mechanism of actions studies suggest that sorafenib inhibited viral translation through dephosphorylation of several key proteins, including eIF4E and p70S6K, leading to a reduction in viral protein production and overall viral replication.

The small non-coding RNA response to virus infection in the Leishmania vector Lutzomyia longipalpis

Sandflies are well known vectors for Leishmania but also transmit a number of arthropod-borne viruses (arboviruses). Few studies have addressed the interaction between sandflies and arboviruses. RNA interference (RNAi) mechanisms utilize small non-coding RNAs to regulate different aspects of host-pathogen interactions. The small interfering RNA (siRNA) pathway is a broad antiviral mechanism in insects. In addition, at least in mosquitoes, another RNAi mechanism mediated by PIWI interacting RNAs (piRNAs) is activated by viral infection. Finally, endogenous microRNAs (miRNA) may also regulate host immune responses. Here, we analyzed the small non-coding RNA response to Vesicular stomatitis virus (VSV) infection in the sandfly Lutzoymia longipalpis. We detected abundant production of virus-derived siRNAs after VSV infection in adult sandflies. However, there was no production of virus-derived piRNAs and only mild changes in the expression of vector miRNAs in response to infection. We also observed abundant production of virus-derived siRNAs against two other viruses in Lutzomyia Lulo cells. Together, our results suggest that the siRNA but not the piRNA pathway mediates an antiviral response in sandflies. In agreement with this hypothesis, pre-treatment of cells with dsRNA against VSV was able to inhibit viral replication while knock-down of the central siRNA component, Argonaute-2, led to increased virus levels. Our work begins to elucidate the role of RNAi mechanisms in the interaction between L. longipalpis and viruses and should also open the way for studies with other sandfly-borne pathogens.

Sandflies are important insect vectors that transmit many species of Leishmania, bacteria and viruses. We know very little about how this insect vector responds to viral infection. RNA interference (RNAi) utilizes small non-coding RNAs to regulate different aspects of animal physiology, including immune responses. Small interfering RNAs (siRNAs) mediate a major antiviral response in insects. Virus-derived PIWI-interacting RNAs (piRNAs) can also be generated during infection, at least in some insects. Finally, endogenous microRNAs (miRNA) can regulate the host response to infection. Here we show that virus infection triggers activation of the siRNA pathway but not production of piRNAs in the sandfly Lutzomyia longipalpis. Furthermore, activation or inhibition of the siRNA pathway had a direct effect on viral replication. We also show that virus infection caused mild changes to the expression of endogenous miRNAs. Our work describes for the first time a model to study virus infection in sandflies and highlights the importance of the siRNA pathway for the control of virus infection in L. longipalpis. The framework described here can be used to explore other aspects of the vector-pathogen interactions.

A review on current status of antiviral siRNA

Viral diseases like influenza, AIDS, hepatitis, and Ebola cause severe epidemics worldwide. Along with their resistant strains, new pathogenic viruses continue to be discovered so creating an ongoing need for new antiviral treatments. RNA interference is a cellular gene‐silencing phenomenon in which sequence‐specific degradation of target mRNA is achieved by means of complementary short interfering RNA (siRNA) molecules. Short interfering RNA technology affords a potential tractable strategy to combat viral pathogenesis because siRNAs are specific, easy to design, and can be directed against multiple strains of a virus by targeting their conserved gene regions. In this review, we briefly summarize the current status of siRNA therapy for representative examples from different virus families. In addition, other aspects like their design, delivery, medical significance, bioinformatics resources, and limitations are also discussed.

Establishment of an antiviral assay system and identification of severe fever with thrombocytopenia syndrome virus inhibitors

Aims

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infectious disease. SFTS is epidemic in Asia, and its fatality rate is around 30% in Japan. The causative virus severe fever with thrombocytopenia syndrome virus (SFTSV) is a phlebovirus of the family Phenuiviridae (the order Bunyavirales). Although effective treatments are required, there are no antiviral agents currently approved for clinical use. Ribavirin and favipiravir were examined for their anti-SFTSV activity and found to be selective inhibitors of SFTSV replication in vitro. However, their activity was not sufficient. Therefore, it is mandatory to identify novel compounds active against SFTSV. To this end, we have established a safe and rapid assay system for screening selective inhibitors of SFTSV.

Methods

The virus was isolated from SFTS patients treated in Kagoshima University Hospital. Vero cells were infected with SFTSV and incubated in the presence of various concentrations of test compounds. After three days, the cells were examined for their intracellular viral RNA levels by real-time reverse transcription-PCR without extracting viral RNA. The cytotoxicity of test compounds was determined by a tetrazolium dye method.

Results

Among the test compounds, the antimalarial agent amodiaquine was identified as a selective inhibitor of SFTSV replication. Its 50% effective concentration (EC₅₀) and cytotoxic concentration (CC₅₀) were 19.1 ± 5.1 and >100 µM, respectively. The EC₅₀ value of amodiaquine was comparable to those of ribavirin and favipiravir.

Conclusion

Amodiaquine is considered to be a promising lead of novel anti-SFTSV agents, and evaluating the anti-SFTSV activity of its derivatives is in progress.

Development of vaccines against Crimean-Congo haemorrhagic fever virus

Crimean-Congo haemorrhagic fever virus (CCHFV) is a deadly human pathogen of the utmost seriousness being highly lethal causing devastating disease symptoms that result in intense and prolonged suffering to those infected. During the past 40years, this virus has repeatedly caused sporadic outbreaks responsible for relatively low numbers of human casualties, but with an alarming fatality rate of up to 80% in clinically infected patients. CCHFV is transmitted to humans by Hyalomma ticks and contact with the blood of viremic livestock, additionally cases of human-to-human transmission are not uncommon in nosocomial settings. The incidence of CCHF closely matches the geographical range of permissive ticks, which are widespread throughout Africa, Asia, the Middle East and Europe. As such, CCHFV is the most widespread tick-borne virus on earth. It is a concern that recent data shows the geographic distribution of Hyalomma ticks is expanding. Migratory birds are also disseminating Hyalomma ticks into more northerly parts of Europe thus potentially exposing naïve human populations to CCHFV. The virus has been imported into the UK on two occasions in the last five years with the first fatal case being confirmed in 2012. A licensed vaccine to CCHF is not available. In this review, we discuss the background and complications surrounding this limitation and examine the current status and recent advances in the development of vaccines against CCHFV.

Susceptibility and Lethality of Western Equine Encephalitis Virus in Balb/c Mice When Infected by the Aerosol Route

Western equine encephalitis virus (WEEV) naturally cycles between mosquitos and birds or rodents, with a case fatality rate of up to 15% in humans during epizootic outbreaks. There are no medical countermeasures to treat WEEV infection, and accidental aerosol exposure increases the case fatality rate up to 40%. Understanding the pathogenesis of infection is required to develop and assess medical countermeasures. This study describes the clinical and pathological findings of mice infected with WEEV by the aerosol route, and use as a model for WEEV infection in humans. Balb/c mice were infected by the aerosol route with a dose range of high-virulence WEEV strain Fleming to establish the median lethal dose (MLD). The disease course was acute, culminating in severe clinical signs, neuroinvasion, and dose-dependent mortality. Further groups of mice were exposed by the aerosol route, periodically sacrificed, and tissues excised for histopathological examination and virology. Viral titres peaked four days post-challenge in the brain and lungs, corresponding with severe bilateral lesions in rostroventral regions of the encephalon, especially in the olfactory bulb and piriform cortex. Recapitulation of the most serious clinical presentations of human WEEV disease in mice may prove a useful tool in the evaluation of medical countermeasures.

Generation of a Single-Cycle Replicable Rift Valley Fever Vaccine

Rift Valley fever virus (RVFV) (genus Phlebovirus, family Bunyaviridae) is an arbovirus that causes severe disease in humans and livestock in sub-Saharan African countries. The virus carries a tripartite, single-stranded, and negative-sense RNA genome, designated as L, M, and S RNAs. RVFV spread can be prevented by the effective vaccination of animals and humans. Although the MP-12 strain of RVFV is a live attenuated vaccine candidate, MP-12 showed neuroinvasiveness and neurovirulence in young mice and immunodeficiency mice. Hence, there is a concern for the use of MP-12 to certain individuals, especially those that are immunocompromised. To improve MP-12 safety, we have generated a single-cycle, replicable MP-12 (scMP-12), which carries L RNA, S RNA encoding green fluorescent protein in place of a viral nonstructural protein NSs, and an M RNA encoding a mutant envelope protein lacking an endoplasmic reticulum retrieval signal and defective for membrane fusion function. The scMP-12 undergoes efficient amplification in the Vero-G cell line, which is a Vero cell line stably expressing viral envelope proteins, while it undergoes single-cycle replication in naïve cells and completely lacks neurovirulence in suckling mice after intracranial inoculation. A single-dose vaccination of mice with scMP-12 confers protective immunity. Thus, scMP-12 represents a new, promising RVF vaccine candidate. Here we describe protocols for scMP-12 generation by using a reverse genetics system, establishment of Vero-G cells, and titration of scMP-12 in Vero-G cells.

A Crimean-Congo hemorrhagic fever (CCHF) viral vaccine expressing nucleoprotein is immunogenic but fails to confer protection against lethal disease

Crimean-Congo Hemorrhagic Fever (CCHF) is a severe tick-borne disease, endemic in many countries in Africa, the Middle East, Eastern Europe and Asia. Between 15–70% of reported cases are fatal with no approved vaccine available. In the present study, the attenuated poxvirus vector, Modified Vaccinia virus Ankara, was used to develop a recombinant candidate vaccine expressing the CCHF virus nucleoprotein. Cellular and humoral immunogenicity was confirmed in 2 mouse strains, including type I interferon receptor knockout mice, which are susceptible to CCHF disease. Despite the immune responses generated post-immunisation, the vaccine failed to protect animals from lethal disease in a challenge model.

Type-1 angiotensin receptor signaling in central nervous system myeloid cells is pathogenic during fatal alphavirus encephalitis in mice

BACKGROUND

Alphaviruses can cause fatal encephalitis in humans. Natural infections occur via the bite of infected mosquitos, but aerosol transmissibility makes some of these viruses potential bioterrorism agents. Central nervous system (CNS) host responses contribute to alphavirus pathogenesis in experimental models and are logical therapeutic targets. We investigated whether reactive oxygen species (ROS) generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) activity within the CNS contributes to fatal alphavirus encephalitis in mice.

METHODS

Infected animals were treated systemically with the angiotensin receptor-blocking drug, telmisartan, given its ability to cross the blood-brain barrier, selectively block type-1 angiotensin receptors (AT1R), and inhibit Nox-derived ROS production in vascular smooth muscle and other extraneural tissues. Clinical, virological, biochemical, and histopathological outcomes were followed over time.

RESULTS

The importance of the angiotensin II (Ang II)/AT1R axis in disease pathogenesis was confirmed by demonstrating increased Ang II levels in the CNS following infection, enhanced disease survival when CNS Ang II production was suppressed, increased AT1R expression on microglia and tissue-infiltrating myeloid cells, and enhanced disease survival in AT1R-deficient mice compared to wild-type (WT) controls. Systemic administration of telmisartan protected WT mice from lethal encephalitis caused by two different alphaviruses in a dose-dependent manner without altering virus replication or exerting any anti-inflammatory effects in the CNS. Infection triggered up-regulation of multiple Nox subunits in the CNS, while drug treatment inhibited local Nox activity, ROS production, and oxidative neuronal damage. Telmisartan proved ineffective in Nox-deficient mice, demonstrating that this enzyme is its main target in this experimental setting.

CONCLUSIONS

Nox-derived ROS, likely arising from CNS myeloid cells triggered by AT1R signaling, are pathogenic during fatal alphavirus encephalitis in mice. Systemically administered telmisartan at non-hypotensive doses targets Nox activity in the CNS to exert a neuroprotective effect. Disruption of this pathway may have broader implications for the treatment of related infections as well as for other CNS diseases driven by oxidative injury.

The role of HTS in drug discovery at the University of Michigan

High throughput screening (HTS) is an integral part of a highly collaborative approach to drug discovery at the University of Michigan. The HTS lab is one of four core centers that provide services to identify, produce, screen and follow-up on biomedical targets for faculty. Key features of this system are: protein cloning and purification, protein crystallography, small molecule and siRNA HTS, medicinal chemistry and pharmacokinetics. Therapeutic areas that have been targeted include anti-bacterial, metabolic, neurodegenerative, cardiovascular, anti-cancer and anti-viral. The centers work in a coordinated, interactive environment to affordably provide academic investigators with the technology, informatics and expertise necessary for successful drug discovery. This review provides an overview of these centers at the University of Michigan, along with case examples of successful collaborations with faculty.

The genetic basis for susceptibility to Rift Valley fever disease in MBT/Pas mice

The large variation in individual response to infection with Rift Valley fever virus (RVFV) suggests that host genetic determinants play a role in determining virus-induced disease outcomes. These genetic factors are still unknown. The systemic inoculation of mice with RVFV reproduces major pathological features of severe human disease, notably the hepatitis and encephalitis. A genome scan performed on 546 (BALB/c × MBT) F2 progeny identified three quantitative trait loci (QTLs), denoted Rvfs-1 to Rvfs-3, that were associated with disease susceptibility in MBT/Pas mice. Non-parametric interval-mapping revealed one significant and two suggestive linkages with survival time on chromosomes 2 (Rvfs-1), 5 (Rvfs-3) and 11 (Rvfs-2) with respective logarithm of odds (LOD) scores of 4.58, 2.95 and 2.99. The two-part model, combining survival time and survival/death, identified one significant linkage to Rvfs-2 and one suggestive linkage to Rvfs-1 with respective LOD scores of 5.12 and 4.55. Under a multiple model, with additive effects and sex as a covariate, the three QTLs explained 8.3% of the phenotypic variance. Sex had the strongest influence on susceptibility. The contribution of Rvfs-1, Rvfs-2 and Rvfs-3 to survival time of RVFV-infected mice was further confirmed in congenic mice.

Probable Crimean-Congo hemorrhagic fever virus transmission occurred after aerosol-generating medical procedures in Russia: nosocomial cluster

We report here a fatal case of laboratory confirmed Crimean-Congo hemorrhagic fever (CCHF), which caused nosocomial infection in eight health care workers (HCWs), who had provided medical care for the patient. All the HCWs survived. The report demonstrates that airborne transmission of CCHF is a real risk, at least when the CCHF patient is in a ventilator. During performance of any aerosol-generating medical procedures for any CCHF patient airborne precautions should always be added to standard precautions, in particular, airway protective N95 mask or equivalent standard, eye protection, single airborne precaution room, or a well-ventilated setting.

Development of (E)-2-((1,4-dimethylpiperazin-2-ylidene)amino)-5-nitro-N-phenylbenzamide, ML336: Novel 2-amidinophenylbenzamides as potent inhibitors of venezuelan equine encephalitis virus

Venezuelan equine encephalitis virus (VEEV) is an emerging pathogenic alphavirus that can cause significant disease in humans. Given the absence of therapeutic options available and the significance of VEEV as a weaponized agent, an optimization effort was initiated around a quinazolinone screening hit 1 with promising cellular antiviral activity (EC₅₀ = 0.8 μM), limited cytotoxic liability (CC₅₀ > 50 μM), and modest in vitro efficacy in reducing viral progeny (63-fold at 5 μM). Scaffold optimization revealed a novel rearrangement affording amidines, specifically compound 45, which was found to potently inhibit several VEEV strains in the low nanomolar range without cytotoxicity (EC₅₀ = 0.02–0.04 μM, CC₅₀ > 50 μM) while limiting in vitro viral replication (EC₉₀ = 0.17 μM). Brain exposure was observed in mice with 45. Significant protection was observed in VEEV-infected mice at 5 mg kg^–1 day^–1 and viral replication appeared to be inhibited through interference of viral nonstructural proteins.

Inhibition of Rift Valley fever virus replication and perturbation of nucleocapsid-RNA interactions by suramin

Rift Valley fever virus (RVFV) is an emerging infectious pathogen that causes severe disease in humans and livestock and has the potential for global spread. There are currently no proven safe and effective treatment options for RVFV infection. Inhibition of RNA binding to RVFV nucleocapsid protein (N) represents an attractive antiviral therapeutic strategy because several essential steps in the RVFV replication cycle involve N binding to viral RNA. In this study, we demonstrate the therapeutic potential of the drug suramin by showing that it functions well as an inhibitor of RVFV replication at multiple stages in human cell culture. Suramin has been used previously to treat trypanosomiasis in Africa. We characterize the dynamic and cooperative nature of N-RNA binding interactions and the dissociation of high-molecular-mass ribonucleoprotein complexes using suramin, which we previously identified as an N-RNA binding inhibitor in a high-throughput screen. Finally, we elucidate the molecular mechanism used by suramin in vitro to disrupt both specific and nonspecific binding events important for ribonucleoprotein formation.

Human-like antibodies neutralizing Western equine encephalitis virus

This study describes the development of the first neutralizing antibodies against Western equine encephalitis virus (WEEV), a member of the genus Alphavirus. WEEV is transmitted by mosquitoes and can spread to the human central nervous system, causing symptoms ranging from mild febrile reactions to life-threatening encephalitis. WEEV has been classified as a biological warfare agent by the US Centers for Disease Control and Prevention. No anti-WEEV drugs are currently commercially available. Neutralizing antibodies are useful for the pre- and post-exposure treatment of WEEV infections. In this study, two immune antibody gene libraries were constructed from two macaques immunized with inactivated WEEV. Four antibodies were selected from these libraries and recloned as scFv-Fc, with a human Fc part. These antibodies bound WEEV specifically in ELISA with little or no cross-reaction with other alphaviruses. They were further analyzed by immunohistochemistry. All binders were suitable for the intracellular detection of WEEV particles. Neutralizing activity was determined in vitro. Three of the four antibodies were found to be neutralizing; about 1 ng/mL of the best antibody (ToR69–3A2) neutralized 50% of 5x10⁴ TCID₅₀/mL. Due to its human-like nature with a germinality index of 89% (VH) and 91% (VL), the ToR69–3A2 antibody is a promising candidate for future passive vaccine development.

The risk of Rift Valley fever virus introduction and establishment in the United States and European Union

Rift Valley fever virus (RVFV) is an arthropod-borne disease resulting in severe morbidity and mortality in both human and ruminant populations. First identified in Kenya in 1930, the geographical range of RVFV has been largely constrained to the African continent, yet has recently spread to new regions, and is identified as a priority disease with potential for geographic emergence. We present a systematic literature review assessing the potential for RVFV introduction and establishment in the United States (US) and European Union (EU). Viable pathways for the introduction of RVFV include: transport of virus-carrying vectors, importation of viremic hosts and intentional entry of RVFV as a biological weapon. It is generally assumed that the risk of RVFV introduction into the US or EU is low. We argue that the risk of sporadic introduction is likely high, though currently an insufficient proportion of such introductions coincide with optimal environmental conditions. Future global trends may increase the likelihood of risk factors for RVFV spread.

Optimization of novel indole-2-carboxamide inhibitors of neurotropic alphavirus replication

Neurotropic alphaviruses, which include western equine encephalitis virus (WEEV) and Fort Morgan virus, are mosquito-borne pathogens that infect the central nervous system causing acute and potentially fatal encephalitis. We previously reported a novel series of indole-2-carboxamides as alphavirus replication inhibitors, one of which conferred protection against neuroadapted Sindbis virus infection in mice. We describe here further development of this series, resulting in 10-fold improvement in potency in a WEEV replicon assay and up to 40-fold increases in half-lives in mouse liver microsomes. Using a rhodamine123 uptake assay in MDR1-MDCKII cells, we were able to identify structural modifications that markedly reduce recognition by P-glycoprotein, the key efflux transporter at the blood-brain barrier. In a preliminary mouse PK study, we were able to demonstrate that two new analogues could achieve higher and/or longer plasma drug exposures than our previous lead and that one compound achieved measurable drug levels in the brain.

Biowarfare and bioterrorism

Bioterrorism is not only a reality of the times in which we live but bioweapons have been used for centuries. Critical care physicians play a major role in the recognition of and response to a bioterrorism attack. Critical care clinicians must be familiar with the diagnosis and management of the most likely bioterrorism agents, and also be adequately prepared to manage a mass casualty situation. This article reviews the epidemiology, diagnosis, and treatment of the most likely agents of biowarfare and bioterrorism.