Third International Conference on Crimean-Congo Hemorrhagic Fever in Thessaloniki, Greece, September 19-21, 2023

The Third International Conference on Crimean-Congo Hemorrhagic Fever (CCHF) was held in Thessaloniki, Greece, September 19-21, 2023, bringing together a diverse group of international partners, including public health professionals, clinicians, ecologists, epidemiologists, immunologists, and virologists. The conference was attended by 118 participants representing 24 countries and the World Health Organization (WHO). Meeting sessions covered the epidemiology of CCHF in humans; Crimean-Congo hemorrhagic fever virus (CCHFV) in ticks; wild and domestic animal hosts; molecular virology; pathogenesis and animal models; immune response related to therapeutics; and CCHF prevention in humans. The concluding session focused on recent WHO recommendations regarding disease prevention, control strategies, and innovations against CCHFV outbreaks. This meeting report summarizes lectures by the invited speakers and highlights advances in the field.

Seroprevalence and Risk Factors Associated with Phleboviruses and Crimean-Congo Hemorrhagic Fever Virus among Blood Donors in Central Tunisia

The aim of this study was to determine the prevalence of six viruses, from two families of the order Bunyavirales, in the general population of central Tunisia. Sera collected from 377 asymptomatic blood donors were serologically assayed for Rift Valley fever virus (RVFV), Crimean-Congo hemorrhagic fever virus (CCHFV), and four sandfly-borne phleboviruses: Toscana virus (TOSV), sandfly fever Naples virus (SFNV), sandfly fever Sicilian virus (SFSV), and sandfly fever Cyprus virus (SFCV). Of the 377 subjects enrolled in this study, 17.3% were IgG positive for at least one of the viruses tested. The most frequently detected antibodies were against TOSV (13.3%), followed by SFCV (2.9%), RVFV (1.9%), SFSV (1.3%), and SFNV (1.1%). Only one sample was IgG positive for CCHFV. Dual reactivity was observed in nine cases: SFSV + SFCV in three cases (0.8%) and TOSV + SFNV, TOSV + SFCV, and TOSV + RVFV in two cases (0.5%) each. 15.9% of donors were IgG positive against sandfly-borne phleboviruses. Among the 65 donors IgG positive for phleboviruses, 50.8% were from rural areas compared to 12.3% from urban areas (p < 0.001); 92.3% had animals in their living quarters (p = 0.009); and 70.8% lived in the vicinity of stagnant water (p = 0.062). Seroprevalence was significantly higher among donors living with chronic diseases (p = 0.039). Furthermore, the seroprevalence of phleboviruses was higher in Kairouan, the central governorate, than in the two coastal governorates: Monastir and Sousse, with 33.4%, 24.2%, and 14.9%, respectively. The presence of antibodies in the general population needs further investigation to better assess the extent of these viruses. Only TOSV was known to have an extensive circulation in Tunisia and in North Africa. Continued surveillance and interventions are necessary to detect the emergence of all arboviruses and to prevent further transmission.

Pathogenesis of Rift Valley Fever Virus in a BALB/c Mouse Model Is Affected by Virus Culture Conditions and Sex of the Animals

Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen causing disease in livestock and humans. Whilst initially restricted to the African continent, recent spread to the Arabian Peninsula has highlighted the likelihood of entry into new regions. Due to the absence of a regulatory-approved human vaccine, work is ongoing to develop and assess countermeasures. As such, small animal models play a pivotal role in providing information on disease pathogenesis and elucidating which intervention strategies confer protection. To develop and establish the BALB/c mouse model, we challenged mice with RVFV grown from two separate cell lines: one derived from mosquitoes (C6/36) and the other mammalian derived (Vero E6). Following infection, we assessed the clinical course of disease progression at days 1 and 3 post-challenge and evaluated viral tropism and immune analytes. The results demonstrated that RVFV infection was affected by the cell line used to propagate the challenge virus, with those grown in insect cells resulting in a more rapid disease progression. The lowest dose that caused uniform severe disease remained the same across both virus preparations. In addition, to demonstrate reproducibility, the lowest dose was used for a subsequent infection study using male and female animals. The results further demonstrated that male mice succumbed to infection more rapidly than their female counterparts. Our results establish an RVFV mouse model and key parameters that affect the course of disease progression in BALB/c mice.

Refinement of an ovine-based immunoglobulin therapy against SARS-CoV-2, with comparison of whole IgG versus F(ab')2 fragments

The development of new therapies against SARS-CoV-2 is required to extend the toolkit of intervention strategies to combat the global pandemic. In this study, hyperimmune plasma from sheep immunised with whole spike SARS-CoV-2 recombinant protein has been used to generate candidate products. In addition to purified IgG, we have refined candidate therapies by removing non-specific IgG via affinity binding along with fragmentation to eliminate the Fc region to create F(ab')2 fragments. These preparations were evaluated for in vitro activity and demonstrated to be strongly neutralising against a range of SARS-CoV-2 strains, including Omicron B2.2. In addition, their protection against disease manifestations and viral loads were assessed using a hamster SARS-CoV-2 infection model. Results demonstrated protective effects of both IgG and F(ab')2, with the latter requiring sequential dosing to maintain in vivo activity due to rapid clearance from the circulation.

Establishment of a Nipah Virus Disease Model in Hamsters, including a Comparison of Intranasal and Intraperitoneal Routes of Challenge

Nipah virus (NiV) is an emerging pathogen that can cause severe respiratory illness and encephalitis in humans. The main reservoir is fruit bats, distributed across a large geographical area that includes Australia, Southeast Asia, and Africa. Incursion into humans is widely reported through exposure of infected pigs, ingestion of contaminated food, or through contact with an infected person. With no approved treatments or vaccines, NiV poses a threat to human public health and has epidemic potential. To aid with the assessment of emerging interventions being developed, an expansion of preclinical testing capability is required. Given variations in the model parameters observed in different sites during establishment, optimisation of challenge routes and doses is required. Upon evaluating the hamster model, an intranasal route of challenge was compared with intraperitoneal delivery, demonstrating a more rapid dissemination to wider tissues in the latter. A dose effect was observed between those causing respiratory illness and those resulting in neurological disease. The data demonstrate the successful establishment of the hamster model of NiV disease for subsequent use in the evaluation of vaccines and antivirals.

Adenoviral vectored vaccination protects against Crimean-Congo Haemorrhagic Fever disease in a lethal challenge model

BACKGROUND

The tick-borne bunyavirus, Crimean-Congo Haemorrhagic Fever virus (CCHFV), can cause severe febrile illness in humans and has a wide geographic range that continues to expand due to tick migration. Currently, there are no licensed vaccines against CCHFV for widespread usage.

METHODS

In this study, we describe the preclinical assessment of a chimpanzee adenoviral vectored vaccine (ChAdOx2 CCHF) which encodes the glycoprotein precursor (GPC) from CCHFV.

FINDINGS

We demonstrate here that vaccination with ChAdOx2 CCHF induces both a humoral and cellular immune response in mice and 100% protection in a lethal CCHF challenge model. Delivery of the adenoviral vaccine in a heterologous vaccine regimen with a Modified Vaccinia Ankara vaccine (MVA CCHF) induces the highest levels of CCHFV-specific cell-mediated and antibody responses in mice. Histopathological examination and viral load analysis of the tissues of ChAdOx2 CCHF immunised mice reveals an absence of both microscopic changes and viral antigen associated with CCHF infection, further demonstrating protection against disease.

INTERPRETATION

There is the continued need for an effective vaccine against CCHFV to protect humans from lethal haemorrhagic disease. Our findings support further development of the ChAd platform expressing the CCHFV GPC to seek an effective vaccine against CCHFV.

FUNDING

This research was supported by funding from the Biotechnology and Biological Sciences Research Council (UKRI-BBSRC) [BB/R019991/1 and BB/T008784/1].

Exploring the Potential of Iminosugars as Antivirals for Crimean-Congo Haemorrhagic Fever Virus, Using the Surrogate Hazara Virus: Liquid-Chromatography-Based Mapping of Viral N-Glycosylation and In Vitro Antiviral Assays

Crimean-Congo haemorrhagic fever virus (CCHFV) is a pathogen of increasing public health concern, being a widely distributed arbovirus and the causative agent of the potentially fatal Crimean-Congo haemorrhagic fever. Hazara virus (HAZV) is a genetically and serologically related virus that has been proposed as a surrogate for antiviral and vaccine testing for CCHFV. Glycosylation analysis of HAZV has been limited; first, we confirmed for the first time the occupation of two N-glycosylation sites in the HAZV glycoprotein. Despite this, there was no apparent antiviral efficacy of a panel of iminosugars against HAZV, as determined by quantification of the total secretion and infectious virus titres produced following infection of SW13 and Vero cells. This lack of efficacy was not due to an inability of deoxynojirimycin (DNJ)-derivative iminosugars to access and inhibit endoplasmic reticulum α-glucosidases, as demonstrated by free oligosaccharide analysis in uninfected and infected SW13 and uninfected Vero cells. Even so, iminosugars may yet have potential as antivirals for CCHFV since the positions and importance of N-linked glycans may differ between the viruses, a hypothesis requiring further evaluation.

Activity of a Carbohydrate-Binding Module Therapy, Neumifil, against SARS-CoV-2 Disease in a Hamster Model of Infection

The rapid global spread of severe acute respiratory coronavirus 2 (SARS-CoV-2) has resulted in an urgent effort to find efficacious therapeutics. Broad-spectrum therapies which could be used for other respiratory pathogens confer advantages, as do those based on targeting host cells that are not prone to the development of resistance by the pathogen. We tested an intranasally delivered carbohydrate-binding module (CBM) therapy, termed Neumifil, which is based on a CBM that has previously been shown to offer protection against the influenza virus through the binding of sialic acid receptors. Using the recognised hamster model of SARS-CoV-2 infection, we demonstrate that Neumifil significantly reduces clinical disease severity and pathological changes in the nasal cavity. Furthermore, we demonstrate Neumifil binding to the human angiotensin-converting enzyme 2 (ACE2) receptor and spike protein of SARS-CoV-2. This is the first report describing the testing of this type of broad-spectrum antiviral therapy in vivo and provides evidence for the advancement of Neumifil in further preclinical and clinical studies.

Multi-omics insights into host-viral response and pathogenesis in Crimean-Congo hemorrhagic fever viruses for novel therapeutic target

The pathogenesis and host-viral interactions of the Crimean–Congo hemorrhagic fever orthonairovirus (CCHFV) are convoluted and not well evaluated. Application of the multi-omics system biology approaches, including biological network analysis in elucidating the complex host-viral response, interrogates the viral pathogenesis. The present study aimed to fingerprint the system-level alterations during acute CCHFV-infection and the cellular immune responses during productive CCHFV-replication in vitro. We used system-wide network-based system biology analysis of peripheral blood mononuclear cells (PBMCs) from a longitudinal cohort of CCHF patients during the acute phase of infection and after one year of recovery (convalescent phase) followed by untargeted quantitative proteomics analysis of the most permissive CCHFV-infected Huh7 and SW13 cells. In the RNAseq analysis of the PBMCs, comparing the acute and convalescent-phase, we observed system-level host’s metabolic reprogramming towards central carbon and energy metabolism (CCEM) with distinct upregulation of oxidative phosphorylation (OXPHOS) during CCHFV-infection. Upon application of network-based system biology methods, negative coordination of the biological signaling systems like FOXO/Notch axis and Akt/mTOR/HIF-1 signaling with metabolic pathways during CCHFV-infection were observed. The temporal quantitative proteomics in Huh7 showed a dynamic change in the CCEM over time and concordant with the cross-sectional proteomics in SW13 cells. By blocking the two key CCEM pathways, glycolysis and glutaminolysis, viral replication was inhibited in vitro. Activation of key interferon stimulating genes during infection suggested the role of type I and II interferon-mediated antiviral mechanisms both at the system level and during progressive replication.

Crimean-Congo hemorrhagic fever (CCHF) is an emerging disease that is increasingly spreading to new populations. The condition is now endemic in almost 30 countries in sub-Saharan Africa, South-Eastern Europe, the Middle East and Central Asia. CCHF is caused by a tick-borne virus and can cause uncontrolled bleeding. It has a mortality rate of up to 40%, and there are currently no vaccines or effective treatments available.

All viruses depend entirely on their hosts for reproduction, and they achieve this through hijacking the molecular machinery of the cells they infect. However, little is known about how the CCHF virus does this and how the cells respond. To understand more about the relationship between the cell’s metabolism and viral replication, Neogi, Elaldi et al. studied immune cells taken from patients during an infection and one year later.

The gene activity of the cells showed that the virus prefers to hijack processes known as central carbon and energy metabolism. These are the main regulator of the cellular energy supply and the production of essential chemicals. By using cancer drugs to block these key pathways, Neogi, Elaldi et al. could reduce the viral reproduction in laboratory cells.

These findings provide a clearer understanding of how the CCHF virus replicates inside human cells. By interfering with these processes, researchers could develop new antiviral strategies to treat the disease. One of the cancer drugs tested in cells, 2-DG, has been approved for emergency use against COVID-19 in some countries. Neogi, Elaldi et al. are now studying this further in animals with the hope of reaching clinical trials in the future.

Screening of wild deer populations for exposure to SARS-CoV-2 in the United Kingdom, 2020-2021

Following findings in Northern America of SARS‐CoV‐2 infections in white‐tailed deer, there is concern of similar infections in European deer and their potential as reservoirs of SARS‐CoV‐2 including opportunities for the emergence of new variants. UK deer sera were collected in 2020–2021 from 6 species and a hybrid with 1748 tested using anti‐spike and anti‐nucleocapsid serology assays. No samples were positive on both assays nor by surrogate neutralization testing. There is no evidence that spill‐over infections of SARS‐CoV‐2 occurred from the human population to UK deer or that SARS‐CoV‐2 has been circulating in UK deer (over the study period). Although it cannot be ruled out, study results indicate that spill‐over infections followed by circulation of SARS‐CoV‐2 to the most common European deer species is small.

Plant-made dengue virus-like particles produced by co-expression of structural and non-structural proteins induce a humoral immune response in mice

Dengue virus (DENV) is an emerging threat causing an estimated 390 million infections per year. Dengvaxia, the only licensed vaccine, may not be adequately safe in young and seronegative patients; hence, development of a safer, more effective vaccine is of great public health interest. Virus-like particles (VLPs) are a safe and very efficient vaccine strategy, and DENV VLPs have been produced in various expression systems. Here, we describe the production of DENV VLPs in Nicotiana benthamiana using transient expression. The co-expression of DENV structural proteins (SP) and a truncated version of the non-structural proteins (NSPs), lacking NS5 that contains the RNA-dependent RNA polymerase, led to the assembly of DENV VLPs in plants. These VLPs were comparable in appearance and size to VLPs produced in mammalian cells. Contrary to data from other expression systems, expression of the protein complex prM-E was not successful, and strategies used in other expression systems to improve the VLP yield did not result in increased yields in plants but, rather, increased purification difficulties. Immunogenicity assays in BALB/c mice revealed that plant-made DENV1-SP + NSP VLPs led to a higher antibody response in mice compared with DENV-E domain III displayed inside bluetongue virus core-like particles and a DENV-E domain III subunit. These results are consistent with the idea that VLPs could be the optimal approach to creating candidate vaccines against enveloped viruses.

Prophylactic intranasal administration of a TLR2/6 agonist reduces upper respiratory tract viral shedding in a SARS-CoV-2 challenge ferret model

BACKGROUND

The novel human coronavirus SARS-CoV-2 is a major ongoing global threat with huge economic burden. Like all respiratory viruses, SARS-CoV-2 initiates infection in the upper respiratory tract (URT). Infected individuals are often asymptomatic, yet highly infectious and readily transmit virus. A therapy that restricts initial replication in the URT has the potential to prevent progression of severe lower respiratory tract disease as well as limiting person-to-person transmission.

METHODS

SARS-CoV-2 Victoria/01/2020 was passaged in Vero/hSLAM cells and virus titre determined by plaque assay. Challenge virus was delivered by intranasal instillation to female ferrets at 5.0 × 106 pfu/ml. Treatment groups received intranasal INNA-051, developed by Ena Respiratory. SARS-CoV-2 RNA was detected using the 2019-nCoV CDC RUO Kit and QuantStudio™ 7 Flex Real-Time PCR System. Histopathological analysis was performed using cut tissues stained with haematoxylin and eosin (H&E).

FINDINGS

We show that prophylactic intra-nasal administration of the TLR2/6 agonist INNA-051 in a SARS-CoV-2 ferret infection model effectively reduces levels of viral RNA in the nose and throat. After 5 days post-exposure to SARS-CoV-2, INNA-051 significantly reduced virus in throat swabs (p=<0.0001) by up to a 24 fold (96% reduction) and in nasal wash (p=0.0107) up to a 15 fold (93% reduction) in comparison to untreated animals.

INTERPRETATION

The results of our study support clinical development of a therapy based on prophylactic TLR2/6 innate immune activation in the URT, to reduce SARS-CoV-2 transmission and provide protection against COVID-19.

FUNDING

This work was funded by Ena Respiratory, Melbourne, Australia.

A probable case of tick-borne encephalitis (TBE) acquired in England, July 2019

The United Kingdom (UK) has thus far been considered to be free from tick-borne encephalitis (TBE), yet in July 2019, a German infant developed serologically diagnosed TBE following a tick bite in southern England. This first report of a probable human case together with recent findings of TBE virus in ticks in foci in England suggest that TBE may be acquired in parts of England and should be considered in patients with aetiologically-unexplained neurological manifestations.

Therapeutic Monoclonal Antibodies for Ebola Virus Infection Derived from Vaccinated Humans

We describe therapeutic monoclonal antibodies isolated from human volunteers vaccinated with recombinant adenovirus expressing Ebola virus glycoprotein (EBOV GP) and boosted with modified vaccinia virus Ankara. Among 82 antibodies isolated from peripheral blood B cells, almost half neutralized GP pseudotyped influenza virus. The antibody response was diverse in gene usage and epitope recognition. Although close to germline in sequence, neutralizing antibodies with binding affinities in the nano- to pico-molar range, similar to "affinity matured" antibodies from convalescent donors, were found. They recognized the mucin-like domain, glycan cap, receptor binding region, and the base of the glycoprotein. A cross-reactive cocktail of four antibodies, targeting the latter three non-overlapping epitopes, given on day 3 of EBOV infection, completely protected guinea pigs. This study highlights the value of experimental vaccine trials as a rich source of therapeutic human monoclonal antibodies.

A Multi-Filovirus Vaccine Candidate: Co-Expression of Ebola, Sudan, and Marburg Antigens in a Single Vector

In the infectious diseases field, protective immunity against individual virus species or strains does not always confer cross-reactive immunity to closely related viruses, leaving individuals susceptible to disease after exposure to related virus species. This is a significant hurdle in the field of vaccine development, in which broadly protective vaccines represent an unmet need. This is particularly evident for filoviruses, as there are multiple family members that can cause lethal haemorrhagic fever, including Zaire ebolavirus, Sudan ebolavirus, and Marburg virus. In an attempt to address this need, both pre-clinical and clinical studies previously used mixed or co-administered monovalent vaccines to prevent filovirus mediated disease. However, these multi-vaccine and multi-dose vaccination regimens do not represent a practical immunisation scheme when considering the target endemic areas. We describe here the development of a single multi-pathogen filovirus vaccine candidate based on a replication-deficient simian adenoviral vector. Our vaccine candidate encodes three different filovirus glycoproteins in one vector and induces strong cellular and humoral immunity to all three viral glycoproteins after a single vaccination. Crucially, it was found to be protective in a stringent Zaire ebolavirus challenge in guinea pigs in a one-shot vaccination regimen. This trivalent filovirus vaccine offers a tenable vaccine product that could be rapidly translated to the clinic to prevent filovirus-mediated viral haemorrhagic fever.

Emerging viruses and current strategies for vaccine intervention

During the past decade several notable viruses have suddenly emerged from obscurity or anonymity to become serious global health threats, provoking concern regarding their sustained epidemic transmission in immunologically naive human populations. With each new threat comes the call for rapid vaccine development. Indeed, vaccines are considered a critical component of disease prevention for emerging viral infections because, in many cases, other medical options are limited or non‐existent, or that infections result in such a rapid clinical deterioration that the effectiveness of therapeutics is limited. While classic approaches to vaccine development are still amenable to emerging viruses, the application of molecular techniques in virology has profoundly influenced our understanding of virus biology, and vaccination methods based on replicating, attenuated and non‐replicating virus vector approaches have become useful vaccine platforms. Together with a growing understanding of viral disease emergence, a range of vaccine strategies and international commitment to underpin development, vaccine intervention for new and emerging viruses may become a possibility.

Detection of Crimean-Congo Haemorrhagic Fever cases in a severe undifferentiated febrile illness outbreak in the Federal Republic of Sudan: A retrospective epidemiological and diagnostic cohort study

Background

Undifferentiated febrile illness (UFI) is one of the most common reasons for people seeking healthcare in low-income countries. While illness and death due to specific infections such as malaria are often well-quantified, others are frequently uncounted and their impact underappreciated. A number of high consequence infectious diseases, including Ebola virus, are endemic or epidemic in the Federal Republic of Sudan which has experienced at least 12 UFI outbreaks, frequently associated with haemorrhage and high case fatality rates (CFR), since 2012. One of these occurred in Darfur in 2015/2016 with 594 cases and 108 deaths (CFR 18.2%). The aetiology of these outbreaks remains unknown.

Methodology/Principal findings

We report a retrospective cohort study of the 2015/2016 Darfur outbreak, using a subset of 65 of 263 outbreak samples received by the National Public Health Laboratory which met selection criteria of sufficient sample volume and epidemiological data. Clinical features included fever (95.8%), bleeding (95.7%), headache (51.6%) and arthralgia (42.2%). No epidemiological patterns indicative of person-to-person transmission or health-worker cases were reported. Samples were tested at the Public Health England Rare and Imported Pathogens Laboratory using a bespoke panel of likely pathogens including haemorrhagic fever viruses, arboviruses and Rickettsia, Leptospira and Borrelia spp. Seven (11%) were positive for Crimean-Congo haemorrhagic fever virus (CCHFV) by real-time reverse transcription PCR. The remaining samples tested negative on all assays.

Conclusions/Significance

CCHFV is an important cause of fever and haemorrhage in Darfur, but not the sole major source of UFI outbreaks in Sudan. Prospective studies are needed to explore other aetiologies, including novel pathogens. The presence of CCHFV has critical infection, prevention and control as well as clinical implications for future response. Our study reinforces the need to boost surveillance, lab and investigative capacity to underpin effective response, and for local and international health security.

The Federal Republic of Sudan has had at least 12 outbreaks of febrile illness of unknown cause associated with symptoms of haemorrhage and high case fatality rates since 2012. Outbreaks without clear diagnosis are concerning, particularly in countries such as Sudan where a range of high consequence diseases, including viral haemorrhagic fevers, are endemic or epidemic, and local laboratory capacity is limited. We transferred historical samples stored in the National Public Health Authority from one of these outbreaks that occurred in Darfur 2015–2016 to the Public Health England Laboratory at Porton, UK, and tested them against a wide range of infectious diseases to try to identify the cause, and to help the Sudanese Federal Ministry of Health to develop and target their limited laboratory capacity. We found that Crimean-Congo Haemorrhagic Fever was an important cause but not the only source of cases in this outbreak. This has implications for prevention and control as well as for treating cases. Our study also highlighted the need for future studies to explore other possible causes, including new pathogens, and reinforced the need to boost surveillance, lab and investigative capacity for more timely and complete outbreak response.

Absence of Crimean-Congo haemorrhagic fever virus in the tick Hyalomma aegyptium parasitizing the spur-thighed tortoise (Testudo graeca) in Tunisia

Free-ranging spur-thighed tortoises Testudo graeca, captured in different habitat types of Northern Tunisia from March to April 2017, were examined for tick infestation: 134/147 (91%) were infested. The overall infestation intensity and abundance was 8.5 and 7.8, respectively. From these tortoises, 1174 ticks were collected, of which 10% (n = 120) taken from 18 randomly-selected tortoises were identified at the species level; the remaining ticks were examined for the presence of Crimean-Congo haemorrhagic fever virus (CCHFv) by real time RT-PCR. Only adult Hyalomma aegyptium were found, suggesting a high degree of host specificity to tortoises. No CCHFv was detected in ticks. Considering the absence of CCHFv in Hyalomma aegyptium infesting its main host, the spur-thighed tortoise, this tick species is unlikely to play a major role in the epidemiology of CCHF. Therefore, more studies are needed to investigate the circulation of this arbovirus between livestock and other tick species from North Africa.

A Human Bi-specific Antibody against Zika Virus with High Therapeutic Potential

Zika virus (ZIKV), a mosquito-borne flavivirus, causes devastating congenital birth defects. We isolated a human monoclonal antibody (mAb), ZKA190, that potently cross-neutralizes multi-lineage ZIKV strains. ZKA190 is highly effective in vivo in preventing morbidity and mortality of ZIKV-infected mice. NMR and cryo-electron microscopy show its binding to an exposed epitope on DIII of the E protein. ZKA190 Fab binds all 180 E protein copies, altering the virus quaternary arrangement and surface curvature. However, ZIKV escape mutants emerged in vitro and in vivo in the presence of ZKA190, as well as of other neutralizing mAbs. To counter this problem, we developed a bispecific antibody (FIT-1) comprising ZKA190 and a second mAb specific for DII of E protein. In addition to retaining high in vitro and in vivo potencies, FIT-1 robustly prevented viral escape, warranting its development as a ZIKV immunotherapy.

Specificity, cross-reactivity, and function of antibodies elicited by Zika virus infection

Zika virus (ZIKV), a mosquito-borne flavivirus with homology to Dengue virus (DENV), has become a public health emergency. By characterizing memory lymphocytes from ZIKV-infected patients, we dissected ZIKV-specific and DENV-cross-reactive immune responses. Antibodies to nonstructural protein 1 (NS1) were largely ZIKV-specific and were used to develop a serological diagnostic tool. In contrast, antibodies against E protein domain I/II (EDI/II) were cross-reactive and, although poorly neutralizing, potently enhanced ZIKV and DENV infection in vitro and lethally enhanced DENV disease in mice. Memory T cells against NS1 or E proteins were poorly cross-reactive, even in donors preexposed to DENV. The most potent neutralizing antibodies were ZIKV-specific and targeted EDIII or quaternary epitopes on infectious virus. An EDIII-specific antibody protected mice from lethal ZIKV infection, illustrating the potential for antibody-based therapy.

Sero-epidemiological survey of Crimean-Congo hemorrhagic fever virus in Tunisia

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease associated with a high case fatality rate and transmitted mainly by Hyalomma marginatum. The geographical distribution of H. marginatum covers most of the Western Mediterranean basin. We aimed to investigate whether CCHF virus (CCHFv) is circulating in Tunisia. Samples from unexplained acute febrile patients (n = 181) and a high risk group of humans, mainly slaughter workers (n = 38), were collected in the summer of 2014 and analyzed for exposure to CCHFv using serological tests and real-time RT-PCR. Ticks were collected from Northern and Southern Tunisia during May–June 2014 and examined for the presence of CCHFv by real-time RT-PCR. Of the 181 febrile patients, 5 showed only high titers of IgM suggesting a recent exposure to CCHFv. Among 38 slaughter workers, 2 had IgG anti-CCHFv responses yielding a seroprevalence of 5.2%. No CCHFv was detected in ticks and sera. Our results provide evidence of human exposure to CCHFv in Tunisia.

Serologic evidence of exposure to Rift Valley fever virus detected in Tunisia

Rift Valley fever virus (RVFv) is capable of causing dramatic outbreaks amongst economically important animal species and is capable of causing severe symptoms and mortality in humans. RVFv is known to circulate widely throughout East Africa; serologic evidence of exposure has also been found in some northern African countries, including Mauritania. This study aimed to ascertain whether RVFv is circulating in regions beyond its known geographic range. Samples from febrile patients (n = 181) and nonfebrile healthy agricultural and slaughterhouse workers (n = 38) were collected during the summer of 2014 and surveyed for exposure to RVFv by both serologic tests and PCR. Of the 219 samples tested, 7.8% of nonfebrile participants showed immunoglobulin G reactivity to RVFv nucleoprotein and 8.3% of febrile patients showed immunoglobulin M reactivity, with the latter samples indicating recent exposure to the virus. Our results suggest an active circulation of RVFv and evidence of human exposure in the population of Tunisia.

Review of Crimean Congo hemorrhagic fever infection in Kosova in 2008 and 2009: prolonged viremias and virus detected in urine by PCR

Crimean-Congo hemorrhagic fever (CCHF) is a virus transmitted predominantly by ticks. However, contact with infected body fluids or tissues can result in animal-to-human or human-to-human transmission. Numbers of CCHF cases appear to be increasing, especially in Europe. We reviewed cases admitted to a tertiary referral unit in Kosova with suspected CCHF in 2008 and 2009, and looked at a smaller number of specimens which were sent to the Health Protection Agency, Porton Down, U.K., in further detail. The clinical features of cases admitted with suspected CCHF infection were assessed in more detail, and these are the focus of this article. Between 2008 and 2009, the numbers of patients admitted for suspected CCHF infection increased. Of the samples received in Porton Down, CCHF virus was detected in urine samples, and these patients were found to have prolonged viremia. The detection of CCHF in urine, as well as the prolonged viremias seen, are important for clinicians to know, as they may have public health implications with regard to the risk of infection, as well as provide insights into the biology and pathophysiology of infection. Further studies are required regarding the pathogenesis of this virus.

Establishment of an aerosol challenge model of tuberculosis in rhesus macaques and an evaluation of endpoints for vaccine testing

The establishment of an aerosol challenge model in nonhuman primates (NHPs) for the testing of vaccines against Mycobacterium tuberculosis would assist the global effort to optimize novel vaccination strategies. The endpoints used in preclinical challenge studies to identify measures of disease burden need to be accurate and sensitive enough to distinguish subtle differences and benefits afforded by different tuberculosis (TB) vaccine regimens when group sizes are inevitably small. This study sought to assess clinical and nonclinical endpoints as potentially sensitive measures of disease burden in a challenge study with rhesus macaques by using a new protocol of aerosol administration of M. tuberculosis. Immunological and clinical readouts were assessed for utility in vaccine evaluation studies. This is the first example of TB vaccine evaluation with rhesus macaques where long-term survival was one of the primary endpoints. However, we found that in NHP vaccine efficacy studies with maximum group sizes of six animals, survival did not provide a valuable endpoint. Two approaches used in human clinical trials for the evaluation of the gamma interferon (IFN-gamma) response to vaccination (enzyme-linked immunospot [ELISpot] assay and enzyme-linked immunosorbent assay [ELISA]) were included in this study. The IFN-gamma profiles induced following vaccination were found not to correlate with protection, nor did the level of purified protein derivative (PPD)-specific proliferation. The only readout to reliably distinguish vaccinated and unvaccinated NHPs was the determination of lung lesion burden using magnetic resonance (MR) imaging combined with stereology at the end of the study. Therefore, the currently proposed key markers were not shown to correlate with protection, and only imaging offered a potentially reliable correlate.

Cryopreservation of primary animal cell cultures

Cells isolated directly from tissues (primary cultures) have many applications in research and applications in the fields of toxicology, pharmacology, and virology. Where such preparations remain the only scientific option to achieve necessary results it is still possible to refine and reduce the use of animal and human sources of the tissue by cryopreservation of the primary cells for later use, this reduces the need for fresh tissues and enables improvements in standardization through the ability to provide the same cell preparation at different times and to different laboratories. The methods described provide options for adherent cultures as monolayers, harvested cell suspensions, and also lymphocytes isolated from peripheral blood.

Macaques infected long-term with attenuated simian immunodeficiency virus (SIVmac) remain resistant to wild-type challenge, despite declining cytotoxic T lymphocyte responses to an immunodominant epitope

To further investigate mechanisms of protective immunity that are induced by live, attenuated simian immunodeficiency virus (SIV), three macaques were infected with SIVmacGX2, a nef-disrupted molecular clone. In two of these animals, which expressed the MamuA*01 major histocompatibility complex class I allele, loss of functional activity against an SIV-Gag-encoded immunodominant cytotoxic T lymphocyte (CTL) epitope was observed following prolonged infection. Nonetheless, all three animals were resistant to challenge with an uncloned pool of wild-type SIVmac, whereas four naïve controls became infected. Tetramer staining revealed the rapid generation of CD8+ T-cell responses against gag- and tat-encoded immunodominant epitopes in MamuA*01+ challenge controls. The dynamics of these T-cell responses to the wild-type virus were similar to those observed following primary infection of the vaccine group with attenuated virus. In contrast, neither tetramer staining nor gamma interferon ELISpot assay revealed an immediate, systemic, anamnestic response in the wild-type-challenged, attenuated SIV-infected animals. Functional CTL capacity had not been lost in this group, as lytic activity was still evident 17 weeks after challenge. Both attenuated and wild-type viruses induced a disseminated CD8+ T-cell response, which was of a higher magnitude in lymphoid tissues than in the periphery. These results suggest that, at least as measured in the periphery, protection against wild-type infection that is induced by live, attenuated SIV is not dependent on a rechallenge-driven expansion of immunodominant epitope-specific CD8+ T cells and, therefore, pre-existing activity may be sufficient to prevent superinfection.

Mucosal immunization with PLGA-microencapsulated DNA primes a SIV-specific CTL response revealed by boosting with cognate recombinant modified vaccinia virus Ankara

Systemically administered DNA encoding a recombinant human immunodeficiency virus (HIV) derived immunogen effectively primes a cytotoxic T lymphocyte (CTL) response in macaques. In this further pilot study we have evaluated mucosal delivery of DNA as an alternative priming strategy. Plasmid DNA, pTH.HW, encoding a multi-CTL epitope gene, was incorporated into poly(D,L-lactic-co-glycolic acid) microparticles of less than 10 microm in diameter. Five intrarectal immunizations failed to stimulate a circulating vaccine-specific CTL response in 2 Mamu-A*01(+) rhesus macaques. However, 1 week after intradermal immunization with a cognate modified vaccinia virus Ankara vaccine MVA.HW, CTL responses were detected in both animals that persisted until analysis postmortem, 12 weeks after the final boost. In contrast, a weaker and less durable response was seen in an animal vaccinated with the MVA construct alone. Analysis of lymphoid tissues revealed a disseminated CTL response in peripheral and regional lymph nodes but not the spleen of both mucosally primed animals.