African Swine Fever Virus (ASFV) is the causative agent of devastating disease affecting domestic and wild pigs globally. A previous study of the intranasal inoculation of domestic pigs (DP) and wild boar (WB) with the ASFV genotype II strain “Armenia 2007” demonstrated distinct disease outcomes. This study aims to compare the leukocyte, cytokine and biochemical profiles in experimentally infected DP and WB. Blood and serum samples were collected before infection (day 0), from animals euthanized in groups of six (comprising 3 DP and 3 WB) on days 1, 2, 3 and 5 post infection (pi) and from animals that reached a humane endpoint. Both DP and WB developed severe lymphopenia, occurring earlier in WB. Inflammatory response occurred earlier in WB, as evident from day 3 pi by the increased levels of TNF, followed by IL-6 and, to a lesser extent, IL-1β. IL-8 concentrations only increased in some WB, but not in DP. No modulation of Th1-associated cytokines (IFN-γ, IL-12 and IL-18) was detected in DP, whereas WB had a moderate increase in IL-12 and IFN-γ levels from day 5 pi, which peaked at humane endpoint. C-reactive protein levels increased in concomitant with the release of pro-inflammatory cytokines, as early as day 5 pi in WB, reaching its maximum in both DP and WB at the humane endpoint. A delayed but significant increase in the levels of anti-inflammatory mediators IL-1Ra and IL-10 was observed in both groups, but earlier in some WB from day 5 pi. Biochemical analysis revealed potential perturbations of the liver function in both subspecies, characterized by changes in serum AST and triglycerides levels, in addition to renal alterations in DP evidenced by changes in creatinine and urea levels. These findings underscore earlier immune activation in WB, potentially contributing to the different subspecies-specific disease outcomes following ASFV inoculation.

African Swine Fever Virus (ASFV) represents a looming threat to animal health, food safety and to the livestock industry. Virulent strains of ASFV cause a severe and often fatal illness, while attenuated strains are usually associated with mild symptoms. Naturally-occurring attenuated strains are typically deleted of more than 20 genes located at the viral genome’s extremities. Whether other key differences between virulent and attenuated ASFV strains may contribute to the virulence phenotype remains however largely unexplored. In this work, we sought to determine how the dynamics of viral gene expression may shape the host’s innate immune response to ASFV infection and contribute to ASFV virulence. We conducted a medium-throughput transcriptomic study to characterize the viral transcriptome of a panel of virulent and attenuated strains (171 viral genes), as well as the host response of ASFV-infected macrophages (92 host genes). Confocal imaging allowed further characterization of cellular response to infection, by assessing the dynamics of IFN and NF-κB pathway activation in ASFV-infected cells. Our results indicate that the two types of viral pathotypes exhibit global differences in the dynamics of genome replication and viral transcription. Virulent ASFV strains displayed a burst of viral transcription early on, while attenuated strains tended to replicate to higher levels at late time points. The host response was much more pronounced in cells infected with attenuated strains compared to virulent ones, with higher expression levels of interferon-stimulated genes, some innate immunity sensors, and the inducible chaperone HSP70.2. Unexpectedly, genotype I and genotype II virulent strains exhibited some notable differences in their kinetics of viral genome replication and in the host response they provoked, with higher levels of pro-inflammatory cytokines being induced by genotype II strains. Confocal imaging analysis of ASFV-infected primary macrophages revealed that attenuated strains, but not virulent ones, caused the translocation of both p65 and STAT2 to the nucleus. Strikingly, we identified a group of 26 viral genes that were either expressed at higher levels or at an earlier stage of infection by virulent strains. Several of these genes, such as R298L , H233R , DP71L and MGF505-7R encode for proteins that inhibited the type I Interferon response in a reporter cell line system. This work sheds new light on the mechanistical drivers of ASFV virulence and will in the long run help to better understand the protection offered by ASFV Live-Attenuated Vaccine candidates. Author summary African Swine Fever (ASF), a severe infectious disease affecting domestic pigs and wild boars, presents a global threat to the livestock industry. It is caused by African Swine Fever Virus (ASFV), a large DNA virus encoding between 150 and 200 genes. While virulent ASFV strains cause a fatal illness in infected animals, attenuated strains induce only minor symptoms and some can confer subsequent protection against a pathogenic infection. While Live-Attenuated Vaccines for ASFV are under development and represent a promising tool in the fight against ASF, the mechanisms of ASFV virulence (and conversely, attenuation) are not fully understood. In particular, it is unclear whether key differences may exist between attenuated and virulent ASFV strains, beyond the extensive genomic deletions harbored by the former. In this work, we explored for the first time how the dynamics of viral gene expression may influence the innate immune response to different ASFV strains. We found that attenuated ASFV strains trigger a stronger host response compared to virulent ASFV strains, with higher expression levels of innate immune genes and a stronger activation of key signaling hubs. Finally, we identified a group of 26 ASFV genes that may drive this phenomenon and represent novel virulence factors. ### Competing Interest Statement The authors have declared no competing interest.

African Swine Fever (ASF) is a highly economically devastating viral disease for swine. Soft ticks of the genus Ornithodoros are involved in its epidemiology, as vectors and natural reservoirs of African Swine Fever Virus (ASFV). The vector competence of Ornithodoros ticks for ASFV has been mainly studied by mimicking natural tick-to-pig transmission pathways through experimental infections in the laboratory. By reviewing the original research studies dating back to the 1960s on the vector competence of Ornithodoros for ASFV, we estimated the vector competence of 10 tick species in association with 38 viral strains resulting in 51 tick-virus associations. This assessment emphasized the extensive range of protocol designs employed and their impact on the success of tick infection with ASFV. Our results call for standardised procedures in vector competence experiments to facilitate further investigation and reduce potential experimental bias. In particular, we recommend the use of late nymphs or adult ticks from a laboratory colony to achieve efficient infection rates. In addition, viral inoculation should be carried out by blood meal rather than by injection, and preference should be given to high titre blood. Finally, detection of viral DNA should be performed 2 months after inoculation to distinguish between successful replication and residual virus in the tick.

African swine fever virus (ASFV) causes a lethal disease in pigs and represents a significant threat to the global pork industry due to the lack of effective vaccines or treatments. Despite intensive research, many ASFV proteins remain uncharacterized. This study aimed to elucidate the functions of two ASFV proteins, pMGF360-21R and pA151R, through comprehensive analysis of their interactions with host proteins. Using affinity purification-mass spectrometry and yeast two-hybrid screening approaches, we identified the host protein barrier-to-autointegration factor 1 (BANF1) as a key interactor of both viral proteins. Biochemical and colocalization assays confirmed these interactions and demonstrated that MGF360-21R and A151R expression leads to cytoplasmic relocation of BANF1. Functionally, BANF1 silencing significantly reduced ASFV replication, indicating its proviral role. Given BANF1's established function in regulating the cGAS/STING-dependent type I interferon (IFN-I) response, we postulated that A151R and MGF360-21R could inhibit this pathway. Using different strategies, we showed that both A151R and MGF360-21R did indeed inhibit IFN-I induction. Generation of ASFV deficient of A151R or MGF360-21R showed that both mutant viruses enhanced the host IFN response in primary porcine macrophages compared to wild-type virus. However, their capacity to inhibit this pathway could occur through mechanisms independent of BANF1. Proteomic analysis of BANF1 interactors during ASFV infection highlighted potentially roles in chromatin remodeling, nuclear transport, and innate immune response pathways. Altogether, our data provide new insights into ASFV-host interactions, identifying BANF1 as an important new host factor required for replication and uncovering novel functions for A151R and MGF360-21R.

African swine fever virus represents a significant reemerging threat to livestock populations, as its incidence and geographic distribution have surged over the past decade in Europe, Asia, and Caribbean, resulting in substantial socio-economic burdens and adverse effects on animal health and welfare. In a previous report, we described the protective properties of our newly thermo-attenuated strain (ASFV-989) in pigs against an experimental infection of its parental Georgia 2007/1 virulent strain. In this new study, our objective was to characterize the molecular mechanisms underlying the attenuation of ASFV-989. We first compared the activation of type I interferon pathway in response to ASFV-989 and Georgia 2007/1 infections, employing both in vivo and in vitro models. Expression of IFN-α was significantly increased in porcine alveolar macrophages infected with ASFV-989 while pigs infected with Georgia 2007/1 showed higher IFN-α than those infected by ASFV-989. We also used a medium-throughput transcriptomic approach to study the expression of viral genes by both strains, and identified several patterns of gene expression. Subsequently, we investigated whether proteins encoded by the eight genes deleted in ASFV-989 contribute to the modulation of the type I interferon signaling pathway. Using different strategies, we showed that MGF505-4R interfered with the induction of IFN-α/β pathway, likely through interaction with TRAF3. Altogether, our data reveal key differences between ASFV-989 and Georgia 2007/1 in their ability to control IFN-α/β signaling and provide molecular mechanisms underlying the role of MGF505-4R as a virulence factor.

Since the reintroduction of African swine fever virus (ASFV) in Europe in 2007 and its subsequent spread to Asia, wild boar has played a crucial role in maintaining and disseminating the virus. There are significant gaps in the knowledge regarding infection dynamics and disease pathogenesis in domestic pigs and wild boar, particularly at the early infection stage. We aimed to compare domestic pigs and wild boar infected intranasally to mimic natural infection with one of the original highly virulent genotype II ASFV isolates (Armenia 2007). The study involved euthanising three domestic pigs and three wild boar on days 1, 2, 3, and 5 post-infection, while four domestic pigs and four wild boar were monitored until they reached a humane endpoint. The parameters assessed included clinical signs, macroscopic lesions, viremia levels, tissue viral load, and virus shedding in nasal and rectal swabs from day 1 post-infection. Compared with domestic pigs, wild boar were more susceptible to ASFV, with a shorter incubation period and earlier onset of clinical signs. While wild boar reached a humane endpoint earlier than domestic pigs did, the macroscopic lesions were comparatively less severe. In addition, wild boar had earlier viremia, and the virus was also detected earlier in tissues. The medial retropharyngeal lymph nodes were identified as key portals for ASFV infection in both subspecies. No viral genome was detected in nasal or rectal swabs until shortly before reaching the humane endpoint in both domestic pigs and wild boar, suggesting limited virus shedding in acute infections.

Classical swine fever (CSF) is a highly contagious swine-specific disease which may have a huge economic impact for porcine production. CSF is caused by a virus belonging to the Pestivirus genus, which has expanded for the past 5 years with the discovery of new species whose genetic proximity to the CSF virus could further complicate laboratory diagnosis. The various forms of the disease, and in particular the increased frequency of attenuated forms, linked to an evolution of CSF virus strains towards a reduction in their virulence, delay clinical diagnosis. Thus, a long period may elapse before an outbreak is detected, allowing the virus to circulate longer, with the risk of spreading to distant geographical areas. Efforts must be maintained in terms of surveillance and diagnostic tools development in order to detect CSF virus infection early and thus limit the spread of the disease and facilitate control measures.

Molecular biology methods are highly sensitive to detect the genome of pathogens and to study their biology. Polymerase chain reaction (PCR) and reverse transcription followed by a polymerase chain reaction (RT-PCR) permit the detection of the presence and the replication of African swine fever virus in soft ticks. Here, we described our techniques to detect and quantify DNA and RNA of African swine fever virus in soft ticks including a housekeeping gene of soft ticks as internal control.

African swine fever (ASF) is a highly pathogenic disease causing haemorrhagic fever in domestic and wild swine. It is responsible for numerous epizootics, particularly in Europe and Asia, causing major economic losses for the pig industry. African Swine Fever virus (ASFV) is the etiological agent responsible for this disease. It is a very large double-stranded DNA virus, encoding for over 150 proteins. Various studies have shown that there is a close relationship between the ability of some viral proteins to inhibit the type I interferon (IFNI) response and the attenuation and virulence processes of ASFV. This review describes the mechanisms of inhibition of the IFN-I response by ASFV proteins, which provide a molecular explanation of how ASFV escapes the innate immune response.

African swine fever (ASF) is a highly pathogenic disease causing haemorrhagic fever in domestic and wild swine. It is responsible for numerous epizootics, particularly in Europe and Asia, causing major economic losses for the pig industry. African Swine Fever virus (ASFV) is the etiological agent responsible for this disease. It is a very large double-stranded DNA virus, encoding for over 150 proteins. Various studies have shown that there is a close relationship between the ability of some viral proteins to inhibit the type I interferon (IFNI) response and the attenuation and virulence processes of ASFV. This review describes the mechanisms of inhibition of the IFN-I response by ASFV proteins, which provide a molecular explanation of how ASFV escapes the innate immune response.La peste porcine africaine (PPA) est une maladie hautement pathogène causant une fièvre hémorragique chez les suidés domestiques et sauvages. Elle est responsable de nombreuses épizooties notamment en Europe et en Asie, causant de grandes pertes économiques pour la filière porcine. Le virus de la peste porcine africaine (ASFV) est l'agent étiologique responsable de cette maladie. C'est un virus avec un génome à ADN double brin de grande taille, codant pour plus de 150 protéines. Différents travaux ont montré qu'il existe une étroite relation entre la capacité de certaines protéines virales à inhiber la réponse interféron de type I (IFN-I) et les processus d'atténuation et de virulence pour l'ASFV. Cette revue décrit les mécanismes d'inhibition de la réponse IFN-I par les protéines d'ASFV permettant d'expliquer sur le plan moléculaire l'échappement à la réponse immunitaire innée.

Aujeszky’s disease virus (ADV), also known as pseudorabies virus, causes an important neurological infection with a major economic and health impact on animal husbandry. Here, we serologically screened muscle fluid from wild boar (Sus scrofa) for the presence of anti-ADV antibodies. Animals were caught during two hunting seasons (2019–2020 and 2021–2022) from three areas in southeastern France known to be endemic with wild boar populations. A total of 30.33% of the 399 tested animals scored positive for anti-glycoprotein B antibodies directed against ADV using a commercial competitive ELISA test. A significant effect (p-value < 0.0001) of the geographical location and animal age on ADV seroprevalence was observed. The results of this study confirmed the importance of wild boar in the epidemiology of ADV in southeastern France.

Classic swine fever (CSF) is one of the most devastating diseases for pig production. Currently, on the basis of phylogenetic analysis, classic swine fever virus (CSFV) can be divided into three groups with three or four subgroups but only one serogroup is recognized. Two types of CSFV vaccines are commercially available: the MLV and the newer marker vaccines that allow differentiation of field virus-infected versus vaccinated animals (DIVA principle). From an evolutionary point of view, CSFV is relatively stable for a RNA virus and only one serogroup has so far been recognized. Convalescent or vaccinated pigs present a long and stable immunity against all the variants of CSFV, based on neutralizing antibodies against NS3, E2, and Erns viral proteins. Postvaccination monitoring based on serosurveillance for undisclosed infection and the analysis of outbreak data should be seen as an essential component for all vaccination programs.

Several infectious diseases may manifest similar clinical signs to African swine fever (ASF). Differential diagnosis can only be confirmed by laboratory testing. The combination of at least two different methods of laboratory testing to confirm an ASF suspicion is recommended, e.g. detection of viral genome and detection of antibodies in suspected animals. Fully validated methods for detection of the ASF virus (ASFV) genome by PCR are available and some of them are commercialised. They are easy to use in diagnostic laboratories, and suitable for both active and passive surveillance. However, the virus isolation (VI) required for further characterisation of a viral strain requires specific skills and a highly-equipped laboratory. Both methods (PCR, VI) can be applied to assess the contamination of the environment or pork products, pig feed, etc. Fully validated methods for the detection of antibodies to ASFV by ELISA are also commercially available and easy to run. However, for serological test confirmation, the most recommended method (IPT) needs the same equipment as for VI and is mainly run only in national reference laboratories. Pen-side tests have been developed for rapid virus or antibody detection at the herd level. They would be sufficient for viral screening among susceptible animals, although their performances are currently under evaluation.

La peste porcine africaine (PPA) est une maladie, non zoonotique, qui affecte les suidés. Elle provoque une fièvre hémorragique souvent létale chez les porcs domestiques et les sangliers européens alors qu’elle est asymptomatique chez les suidés africains adultes. Cette infection est due à un virus à ADN, double brin et enveloppé, seul membre de la famille des Asfarviridae, qui peut aussi infecter des tiques molles du genre Ornithodoros, vecteur non obligatoire. La PPA, endémique en Afrique, a été réintroduite sur le continent européen en 2007, via la Géorgie, et a depuis diffusé largement jusqu’à atteindre l’union européenne en 2014, la Chine en 2018 avant de s’étendre à l’Asie du Sud-Est et aux îles du Pacifique. La haute résistance du virus dans l’environnement a favorisé sa large dispersion géographique en lien avec les activités humaines. Actuellement, en l’absence de vaccin ou de traitement disponible, seule l’application de mesures drastiques de biosécurité peut prévenir l’introduction en élevage.

African Swine Fever (ASF) is an emerging infectious disease ofdomestic and wild swine. A contagious disease among swine, but not transmissible to humans, it causes an often fatal haemorrhagic syndrome in domestic pigs and wild boars. The outbreak currently affecting Europe and Asia began in Georgia in 2007. The highly virulent strain involved, belonging to genotype II, is extremely resistant in meat and the environment. All strains isolated in Europe and Asia are derived from the same introduction, although the virus has evolved into less virulent forms in some very localized wild boar populations. From Georgia, the virus spread throughout the Caucasus and the Russian Federation, then to Ukraine and Belarus in 2013. In January2014, ASF reached the borders of the European Union and spread to the three Baltic States and Poland widely in wild boar populations, while sporadic outbreaks in domestic pigs were effectively controlled. Recent countries affected in Europe are the Czech Republic, Hungary, Moldova, Romania, Bulgaria and most recently Belgium (13 Sep 2018), Serbia, Slovakia, and Greece in 2020. In China, the virus introduced on 3Aug20 18, probably from Russia, gave rise to a malor epidemic, mainly in the domestic reservoir, that is now completely out of control and has spread to Mongolia and several countries in South-EastAsia, and recently to India. Human activities play a central role as a propagation factor, thus promoting progression bylumps, sometimes over long distances. No vaccine nor treatment are currently available, the only remaining control method is sanitary prophylaxis and prevention of introduction into free territories such as France.

In Europe, African swine fever virus (ASFV) is one of the most threatening infectious transboundary diseases of domestic pigs and wild boar. In September 2018, ASF was detected in wild boar in the South of Belgium. France, as a bordering country, is extremely concerned about the ASF situation in Belgium, and an active preparedness is ongoing in the country. One of the questions raised by this situation relates to disturbing activities that may affect wild boar movements and their possible impact on the spread of ASFV. Despite evidence of disturbance related to hunting practices, there is a paucity of information on the impact of forestry and human leisure activities. To assess this impact on wild boar movements, a systematic review was first conducted but very few useful data were obtained. For this reason, an expert elicitation was carried out by the French Agency for Food, Environmental and Occupational Health & Safety in order to deal with this knowledge gap. A total of 30 experts originating from France and adjacent neighbouring countries (Spain, Belgium and Switzerland) were elicited about the relative importance of six factors of spatial disturbance of wild boar (noise, smell, invasion of space, modification of the environment, duration and frequency of the activity). Then, for each factor of disturbance, they were asked about the impact of 16 different commercial forestry and human leisure activities. A global weighted score was estimated in order to capture the variability of a wide range of territorial conditions and the uncertainty of expert elicitation. This estimate permitted ranking all 16 activities and aggregating them in three groups according to their potential for disturbance of wild boar, using a regression tree analysis. The results of this expert elicitation provide a methodological approach that may be useful for French and other European decision makers and stakeholders involved in the crisis management of ASF.

African swine fever is a highly lethal hemorrhagic fever of Suidae, threatening pig production globally. Suidae can be infected by different ways like ingestion of contaminated feed, direct contact with infected animals or fomites, and biting by infected soft tick bites. As already described, European soft ticks (Ornithodoros erraticus and Ornithodoros verrucosus) were not able to transmit African swine fever virus by biting pigs although these ticks maintained the infectious virus during several months; therefore, the possibility for pigs to become infected through the ingestion of infected ticks was questioned but not already explored. To determine if such oral ingestion is an alternative pathway of transmission, O. erraticus ticks were infected by blood-feeding on a viremic pig infected with the European African swine fever virus strain Georgia2007/1, then frozen at zero and two months post-engorgement, then after, were embedded in the food to pigs. Pig infection was successful, with superior efficiency with ticks frozen just after the infectious blood meal. These results confirmed the potential role of O. erraticus ticks as an ASFV reservoir and demonstrated the efficiency of non-conventional pathways of transmission.

African swine fever (ASF) is one of the most important diseases in Suidae due to its significant health and socioeconomic consequences and represents a major threat to the European pig industry, especially in the absence of any available treatment or vaccine. In fact, with its high mortality rate and the subsequent trade restrictions imposed on affected countries, ASF can dramatically disrupt the pig industry in afflicted countries. In September 2018, ASF was unexpectedly identified in wild boars from southern Belgium in the province of Luxembourg, not far from the Franco-Belgian border. The French authorities rapidly commissioned an expert opinion on the risk of ASF introduction and dissemination into metropolitan France. In Europe, the main transmission routes of the virus comprise direct contact between infected and susceptible animals and indirect transmission through contaminated material or feed. However, the seasonality of the disease in some pig farms in Baltic countries, including outbreaks in farms with high biosecurity levels, have led to questions on the possible involvement of arthropods in the transmission of the virus. This review explores the current body of knowledge on the most common arthropod families present in metropolitan France. We examine their potential role in spreading ASF—by active biological or mechanical transmission or by passive transport or ingestion—in relation to their bio-ecological properties. It also highlights the existence of significant gaps in our knowledge on vector ecology in domestic and wild boar environments and in vector competence for ASFV transmission. Filling these gaps is essential to further understanding ASF transmission in order to thus implement appropriate management measures.

Background Several species of soft ticks in genus Ornithodoros are known vectors and reservoirs of African swine fever virus (ASFV). However, the underlying mechanisms of vector competence for ASFV across Ornithodoros species remain to be fully understood. To that end, this study compared ASFV replication and dissemination as well as virus vertical transmission to descendants between Ornithodoros moubata , O . erraticus , and O . verrucosus in relation to what is known about the ability of these soft tick species to transmit ASFV to pigs. To mimic the natural situation, a more realistic model was used where soft ticks were exposed to ASFV by allowing them to engorge on viremic pigs. Methods Ornithodoros moubata ticks were infected with the ASFV strains Liv13/33 (genotype I) or Georgia2007/1 (genotype II), O. erraticus with OurT88/1 (genotype I) or Georgia2007/1 (genotype II), and O. verrucosus with Ukr12/Zapo (genotype II), resulting in five different tick–virus pairs. Quantitative PCR (qPCR) assays targeting the VP72 ASFV gene was carried out over several months on crushed ticks to study viral replication kinetics. Viral titration assays were also carried out on crushed ticks 2 months post infection to confirm virus survival in soft ticks. Ticks were dissected. and DNA was individually extracted from the following organs to study ASFV dissemination: intestine, salivary glands, and reproductive organs. DNA extracts from each organ were tested by qPCR. Lastly, larval or first nymph-stage progeny emerging from hatching eggs were tested by qPCR to assess ASFV vertical transmission. Results Comparative analyses revealed higher rates of ASFV replication and dissemination in O. moubata infected with Liv13/33, while the opposite was observed for O. erraticus infected with Georgia2007/1 and for O. verrucosus with Ukr12/Zapo. Intermediate profiles were found for O. moubata infected with Georgia2007/1 and for O. erraticus with OurT88/1. Vertical transmission occurred efficiently in O. moubata infected with Liv13/33, and at very low rates in O. erraticus infected with OurT88/1. Conclusions This study provides molecular data indicating that viral replication and dissemination in Ornithodoros ticks are major mechanisms underlying ASFV horizontal and vertical transmission. However, our results indicate that other determinants beyond viral replication also influence ASFV vector competence. Further research is required to fully understand this process in soft ticks. Graphical Abstract