African swine fever virus infection regulates pyroptosis by cleaving gasdermin A via active caspase-3 and caspase-4.

African swine fever, caused by the African swine fever virus (ASFV), is a viral hemorrhagic disease that affects domestic pigs and wild boars. ASFV infection causes extensive tissue damage, and the associated mechanism is poorly understood. Pyroptosis is characterized by the activation of inflammatory caspases and pore formation in the cellular plasma membrane, resulting in the release of inflammatory cytokines and cell damage. How ASFV infection regulates pyroptosis remains unclear. Here, using siRNA assay and overexpression methods, we report that ASFV infection regulated pyroptosis by cleaving the pyroptosis execution protein gasdermin A (GSDMA). ASFV infection activated caspase-3 and caspase-4, which specifically cleaved GSDMA at D75-P76 and D241-V242 to produce GSDMA into five fragments, including GSDMA-N1-75, GSDMA-N1-241, and GSDMA-N76-241 fragments at the N-terminal end of GSDMA. Only GSDMA-N1-241, which was produced in the late stage of ASFV infection, triggered pyroptosis and inhibited ASFV replication. The fragments, GSDMA-N1-75 and GSDMA-N76-241, lose the ability to induce pyroptosis. Overall ASFV infection differentially regulates pyroptosis by GSDMA in the indicated phase, which may be conducive to its own replication. Our findings reveal a novel molecular mechanism for the regulation of pyroptosis.

Deletion of the H240R Gene of African Swine Fever Virus Decreases Infectious Progeny Virus Production Due to Aberrant Virion Morphogenesis and Enhances Inflammatory Cytokine Expression in Porcine Macrophages.

African swine fever virus (ASFV) is a complex nucleocytoplasmic large DNA virus that causes African swine fever, a lethal hemorrhagic disease that currently threatens the pig industry. Recent studies have identified the viral structural proteins of infectious ASFV particles. However, the functional roles of several ASFV structural proteins remain largely unknown. Here, we characterized the function of the ASFV structural protein H240R (pH240R) in virus morphogenesis. pH240R was identified as a capsid protein by using immunoelectron microscopy and interacted with the major capsid protein p72 by pulldown assays. Using a recombinant ASFV, ASFV-ΔH240R, with the H240R gene deleted from the wild-type ASFV (ASFV-WT) genome, we revealed that the infectious progeny virus titers were reduced by approximately 2.0 logs compared with those of ASFV-WT. Furthermore, we demonstrated that the growth defect was due to the generation of noninfectious particles with a higher particle-to-infectious titer ratio in ASFV-ΔH240R-infected primary porcine alveolar macrophages (PAMs) than in those infected with ASFV-WT. Importantly, we found that pH240R did not affect virus-cell binding, endocytosis, or egress but did affect ASFV assembly; noninfectious virions containing large aberrant tubular and bilobulate structures comprised nearly 98% of all virions observed in ASFV-ΔH240R-infected PAMs by electron microscopy. Notably, we demonstrated that ASFV-ΔH240R infection induced high-level expression of inflammatory cytokines in PAMs. Collectively, we show for the first time that pH240R is essential for ASFV icosahedral capsid formation and infectious particle production. Also, these results highlight the importance of pH240R in ASFV morphogenesis and provide a novel target for the development of ASF vaccines and antivirals. IMPORTANCE African swine fever is a lethal hemorrhagic disease of global concern that is caused by African swine fever virus (ASFV). Despite extensive research, there exist relevant gaps in knowledge of the fundamental biology of the viral life cycle. In this study, we identified pH240R as a capsid protein that interacts with the major capsid protein p72. Furthermore, we showed that pH240R was required for the efficient production of infectious progeny virions as indicated by the H240R-deleted ASFV mutant (ASFV-ΔH240R). More specifically, pH240R directs the morphogenesis of ASFV toward the icosahedral capsid in the process of assembly. In addition, ASFV-ΔH240R infection induced high-level expression of inflammatory cytokines in primary porcine alveolar macrophages. Our results elucidate the role of pH240R in the process of ASFV assembly, which may instruct future research on effective vaccines or antiviral strategies.

Clinicopathological and ultrastructural study of African swine fever outbreak in North-East India.

The present investigation focuses on examining the clinical, histopathological, and ultrastructural changes that occurred in pig, during an outbreak of African swine fever (ASF) in 2022 in Assam, India. The disease initially manifested as a per-acute case with high mortality but without any evident clinical signs. Subsequently, some animals exhibited an acute form of the disease characterized by high fever (104-106 °F), anorexia, vomiting, respiratory distress, and bleeding from the anal and nasal orifices. During acute African swine fever virus (ASFV) infections, elevated levels of pro-inflammatory IL-1α, IL-1ß, IL-6, TNF, CCL2, CCL5, and CXCL10 were detected in the palatine tonsil, lymph nodes, spleen, and kidney using qPCR assay. These molecular changes were associated with haemorrhages, edemas, and lymphoid depletion. Postmortem examinations revealed prominent features such as splenomegaly with haemorrhages, haemorrhagic lymphadenitis, severe petechial haemorrhage in the kidney, pneumonia in the lungs, and necrotic palatine tonsil. Histopathological analysis demonstrated lymphocyte depletion in lymphoid organs, multi-organ haemorrhages, and interstitial pneumonia in the lungs. Scanning electron microscopy (SEM) further confirmed lymphocyte depletion in lymphoid organs through lymphocyte apoptosis and kidney damage with distorted tubules due to red blood cell destruction. Transmission electron microscopy reaffirmed lymphocyte apoptosis by observing chromatin condensation and nucleus margination in lymphocytes of lymphoid organs. These findings provide comprehensive insights into the clinical, histopathological, and ultrastructural aspects of ASF outbreak in pigs. Understanding the pathological changes associated with ASF can contribute to improved diagnosis, prevention, and control measures for this highly contagious and economically devastating viral disease.

African swine fever virus protein MGF-505-7R promotes virulence and pathogenesis by inhibiting JAK1- and JAK2-mediated signaling.

African swine fever virus (ASFV) is a large DNA virus that is highly contagious and pathogenic in domestic pigs with a mortality rate up to 100%. However, how ASFV suppresses JAK-STAT1 signaling to evade the immune response remains unclear. In this study, we found that the ASFV-encoded protein MGF-505-7R inhibited proinflammatory IFN-γ-mediated JAK-STAT1 signaling. Mechanistically, MGF-505-7R was found to interact with JAK1 and JAK2 and mediate their degradation. Further study indicated that MGF-505-7R promoted degradation of JAK1 and JAK2 by upregulating the E3 ubiquitin ligase RNF125 expression and inhibiting expression of Hes5, respectively. Consistently, MGF-505-7R-deficient ASFV induced high levels of IRF1 expression and displayed compromised replication both in primary porcine alveolar macrophages and pigs compared with wild-type ASFV. Furthermore, MGF-505-7R deficiency attenuated the virulence of the ASFV and pathogenesis of ASF in pigs. These findings suggest that the JAK-STAT1 axis mediates the innate immune response to the ASFV and that MGF-505-7R plays a critical role in the virulence of the ASFV and pathogenesis of ASF by antagonizing this axis. Thus, we conclude that deletion of MGF-505-7R may serve as a strategy to develop attenuated vaccines against the ASFV.

African Swine Fever Virus Bearing an I226R Gene Deletion Elicits Robust Immunity in Pigs to African Swine Fever.

African swine fever (ASF) is a severe hemorrhagic infectious disease in pigs caused by African swine fever virus (ASFV), leading to devastating economic losses in epidemic regions. Its control currently depends on thorough culling and clearance of the diseased and surrounding suspected pigs. An ASF vaccine has been extensively explored for years worldwide, especially in hog-intensive areas where it is highly desired, but it is still unavailable for numerous reasons. Here, we report another ASF vaccine candidate, named SY18ΔI226R, bearing a deletion of the I226R gene with a replacement of an enhanced green fluorescent protein (eGFP) expression cassette at the right end of the viral genome. This deletion results in the complete loss of virulence of SY18 as the gene-deleted strain does not cause any clinical symptoms in all pigs inoculated with a dosage of either 104.0 or 107.0 50% tissue culture infective doses (TCID50). Apparent viremia with a gradual decline was monitored, while virus shedding was detected only occasionally in oral or anal swabs. ASFV-specific antibody appeared at 9 days postinoculation. After intramuscular challenge with its parental strain ASFV SY18 at 21 days postinoculation, all the challenged pigs survived, without obvious febrile or abnormal clinical signs. No viral DNA could be detected upon the dissection of any tissue when viremia disappeared. These results indicated that SY18ΔI226R is safe in swine and elicits robust immunity to virulent ASFV infection. IMPORTANCE Outbreaks of African swine fever have resulted in devastating losses to the swine industry worldwide, but there is currently no commercial vaccine available. Although several vaccine candidates have been reported, none has been approved for use for several reasons, especially ones concerning biosafety. Here, we identified a new undescribed functional gene, I226R. When deleted from the ASFV genome, the virus completely loses its virulence in swine. Importantly, pigs infected with this gene-deleted virus were resistant to infection by intramuscular challenge with 102.5 or 104.0 TCID50 of its virulent parental virus. Furthermore, the nucleic acid of the gene-deleted virus and its virulent parental virus was rarely detected from oral or anal swabs. Viruses could not be detected in any tissues after necropsy when viremia became negative, indicating that robust immunity was achieved. Therefore, SY18ΔI226R is a novel, ideal, and efficacious vaccine candidate for genotype II ASF.

African swine fever virus MGF360-11L negatively regulates cGAS-STING-mediated inhibition of type I interferon production.

The type I interferon (IFN-I) signaling pathway is an important part of the innate immune response and plays a vital role in controlling and eliminating pathogens. African swine fever virus (ASFV) encodes various proteins to evade the host's natural immunity. However, the molecular mechanism by which the ASFV-encoded proteins inhibit interferon production remains poorly understood. In the present study, ASFV MGF360-11L inhibited cGAS, STING, TBK1, IKKε, IRF7 and IRF3-5D mediated activation of the IFN-ß and ISRE promoters, accompanied by decreases in IFN-ß, ISG15 and ISG56 mRNA expression. ASFV MGF360-11L interacted with TBK1 and IRF7, degrading TBK1 and IRF7 through the cysteine, ubiquitin-proteasome and autophagy pathways. Moreover, ASFV MGF360-11L also inhibited the phosphorylation of TBK1 and IRF3 stimulated by cGAS-STING overexpression. Truncation mutation analysis revealed that aa 167-353 of ASFV MGF360-11L could inhibit cGAS-STING-mediated activation of the IFN-ß and ISRE promoters. Finally, the results indicated that ASFV MGF360-11L plays a significant role in inhibiting IL-1ß, IL-6 and IFN-ß production in PAM cells (PAMs) infected with ASFV. In short, these results demonstrated that ASFV MGF360-11L was involved in regulating IFN-I expression by negatively regulating the cGAS signaling pathway. In summary, this study preliminarily clarified the molecular mechanism by which the ASFV MGF360-11L protein antagonizes IFN-I-mediated antiviral activity, which will help to provide new strategies for the treatment and prevention of ASF.

Absence of Long-Term Protection in Domestic Pigs Immunized with Attenuated African Swine Fever Virus Isolate OURT88/3 or BeninΔMGF Correlates with Increased Levels of Regulatory T Cells and Interleukin-10.

Following short immunization protocols, naturally attenuated African swine fever virus (ASFV) isolate OURT88/3 and deletion mutant BeninΔMGF have previously been shown to induce high percentages of protection in domestic pigs against challenge with virulent virus. The results obtained in the present study show that a single intramuscular immunization of domestic pigs with OURT88/3 or BeninΔMGF followed by a challenge with the virulent Benin 97/1 isolate at day 130 postimmunization did not trigger the mechanisms necessary to generate immunological memory able to induce long-term protection against disease. All pigs developed acute forms of acute swine fever (ASF). Gamma interferon-producing cells peaked at day 24 postimmunization, declining thereafter. Surprisingly, the levels of regulatory T cells (Tregs) and interleukin-10 (IL-10) were elevated at the end of the experiment, suggesting that regulatory components of the immune system may inhibit effective protection.IMPORTANCE The duration of immunity for any vaccine candidate is crucial. In the case of African swine fever virus vaccine candidates, this issue has received little attention. Attenuated viruses have proven protective following short immunization protocols in which pigs were challenged a few weeks after the first immunization. Here, the duration of immunity and the immune responses induced over a duration of 130 days were studied during prechallenge and after challenge of pigs immunized with the naturally attenuated isolate OURT88/3 and an attenuated gene-deleted isolate, BeninΔMGF. After a single intramuscular immunization of domestic pigs with the OURT88/3 isolate or BeninΔMGF virus, animals were not protected against challenge with the virulent Benin 97/1 ASFV genotype I isolate at day 130 postimmunization. The levels of regulatory T cells and IL-10 were elevated at the end of the experiment, suggesting that regulatory components of the immune system may inhibit effective protection.

Unraveling the Armor of a Killer: Evasion of Host Defenses by African Swine Fever Virus.

African swine fever is an acute hemorrhagic disease of pigs. Extensive recent spread in the Russian Federation and Eastern Europe has increased the risk to global pig production. The virus is a large DNA virus and is the only member of the Asfarviridae family. In pigs, the virus replicates predominantly in macrophages. We review how the virus overcomes the barriers to replication in the macrophage and the virus mechanism to inhibit key host defense pathways.

African swine fever virus infection in Classical swine fever subclinically infected wild boars.

BACKGROUND: Recently moderate-virulence classical swine fever virus (CSFV) strains have been proven capable of generating postnatal persistent infection (PI), defined by the maintenance of viremia and the inability to generate CSFV-specific immune responses in animals. These animals also showed a type I interferon blockade in the absence of clinical signs. In this study, we assessed the infection generated in 7-week-old CSFV PI wild boars after infection with the African swine fever virus (ASFV). The wild boars were divided in two groups and were infected with ASFV. Group A comprised boars who were CSFV PI in a subclinical form and Group B comprised pestivirus-free wild boars. Some relevant parameters related to CSFV replication and the immune response of CSFV PI animals were studied. Additionally, serum soluble factors such as IFN-α, TNF-α, IL-6, IL-10, IFN-γ and sCD163 were analysed before and after ASFV infection to assess their role in disease progression. RESULTS: After ASFV infection, only the CSFV PI wild boars showed progressive acute haemorrhagic disease; however, the survival rates following ASFV infection was similar in both experimental groups. Notwithstanding, the CSFV RNA load of CSFV PI animals remained unaltered over the study; likewise, the ASFV DNA load detected after infection was similar between groups. Interestingly, systemic type I FN-α and IL-10 levels in sera were almost undetectable in CSFV PI animals, yet detectable in Group B, while detectable levels of IFN-γ were found in both groups. Finally, the flow cytometry analysis showed an increase in myelomonocytic cells (CD172a+) and a decrease in CD4+ T cells in the PBMCs from CSFV PI animals after ASFV infection. CONCLUSIONS: Our results showed that the immune response plays a role in the progression of disease in CSFV subclinically infected wild boars after ASFV infection, and the immune response comprised the systemic type I interferon blockade. ASFV does not produce any interference with CSFV replication, or vice versa. ASFV infection could be a trigger factor for the disease progression in CSFV PI animals, as their survival after ASFV was similar to that of the pestivirus-free ASFV-infected group. This fact suggests a high resistance in CSFV PI animals even against a virus like ASFV; this may mean that there are relevant implications for CSF control in endemic countries. The diagnosis of ASFV and CSFV co-infection in endemic countries cannot be ruled out and need to be studied in greater depth.

Variations in clinical presentation and anatomical distribution of gross lesions of African swine fever in domestic pigs in the southern highlands of Tanzania: a field experience.

African swine fever is a contagious viral disease responsible for up to 100% mortality among domestic pigs. A longitudinal study was carried out to determine the clinical presentation and anatomical distribution of gross lesions in affected pigs in Mbeya region, Tanzania during the 2010 to 2014 outbreaks. Data were collected during clinical and postmortem examination by field veterinarians and using a structured questionnaire. A total of 118 respondents (100%) showed awareness about African swine fever. During previous outbreaks, the mortality rate was almost 100%, while in 2014 it was estimated to be less than 50%.The clinical picture of the 2010-2012 outbreaks was characterized by high fever, depression, inappetance, mucosal congestion, hemorrhages, erythematous lesions in different body parts, and abortion. Several internal organs including the kidneys, spleen, and liver were congested and edematous. During the 2014 outbreak, a number of pigs (49.7%) were asymptomatic when brought to slaughter slabs but were found to have African swine fever gross lesions at postmortem examination as compared to 12.3% in 2010-2012. Bluish discoloration, which is normally distributed on the non-hairy parts of the body, was not apparent in some pigs except at postmortem examination. Some pigs (36.1%) presented nasal and/or oral bloody discharges which were uncommon (9.1%) during previous outbreaks. Moreover, other gross features included enlarged dark red renal lymph nodes and spleen. Clinical signs such as anorexia, diarrhea, and pyrexia were mainly observed when affected pigs reached moribund stage. The majority of pregnant sows died without presenting abortions. In some litters, suckling piglets (3-6 weeks) survived from the disease. These findings indicated that in 2014, African swine fever outbreak in Mbeya region was characterized by a different clinical picture.

A study of lymphoid organs and serum proinflammatory cytokines in pigs infected with African swine fever virus genotype II.

African swine fever virus (ASFV), the causative agent of one of the most important viral diseases of domestic pigs for which no vaccine is available, causes immune system disorders in infected animals. In this study, the serum levels of proinflammatory cytokines, as well as the histological and cellular constitution of lymphoid organs of pigs infected with ASFV genotype II were investigated. The results showed a high degree of lymphocyte depletion in the lymphoid organs, particularly in the spleen and lymph nodes, where ASFV infection led to a twofold decrease in the number of lymphocytes on the final day of infection. Additionally, ASFV-infected pigs had atypical forms of lymphocytes found in all lymphoid organs. In contrast to lymphocytes, the number of immature immune cells, particularly myelocytes, increased dramatically and reached a maximum on day 7 postinfection. The serum levels of TNF-α, IL-1ß, IL-6, and IL-8 were evaluated. Proinflammatory cytokines showed increased levels after ASFV infection, with peak values at 7 days postinfection, and this highlights their role in the pathogenesis of ASFV. In conclusion, this study showed that ASFV genotype II, like other highly virulent strains, causes severe pathological changes in the immune system of pigs.

Species-specific variation in RELA underlies differences in NF-κB activity: a potential role in African swine fever pathogenesis.

African swine fever virus (ASFV) is a highly infectious disease of domestic pigs, with virulent isolates causing a rapidly fatal hemorrhagic fever. In contrast, the porcine species endogenous to Africa tolerate infection. The ability of the virus to persist in one host while killing another genetically related host implies that disease severity may be, in part, modulated by host genetic variation. To complement transcription profiling approaches to identify the underlying genetic variation in the host response to ASFV, we have taken a candidate gene approach based on known signaling pathways that interact with the virus-encoded immunomodulatory protein A238L. We report the sequencing of these genes from different pig species and the identification and initial in vitro characterization of polymorphic variation in RELA (p65; v-rel reticuloendotheliosis viral oncogene homolog A), the major component of the NF-κB transcription factor. Warthog RELA and domestic pig RELA differ at three amino acids. Transient cell transfection assays indicate that this variation is reflected in reduced NF-κB activity in vitro for warthog RELA but not for domestic pig RELA. Induction assays indicate that warthog RELA and domestic pig RELA are elevated essentially to the same extent. Finally, mutational studies indicate that the S531P site conveys the majority of the functional variation between warthog RELA and domestic pig RELA. We propose that the variation in RELA identified between the warthog and domestic pig has the potential to underlie the difference between tolerance and rapid death upon ASFV infection.

Pathology of porcine peripheral white blood cells during infection with African swine fever virus.

BACKGROUND: African swine fever virus (ASFV) is the causative agent of African swine fever (ASF) that is the significant disease of domestic pigs. Several studies showed that ASFV can influence on porcine blood cells in vitro. Thus, we asked ourselves whether ASFV infection results in changes in porcine blood cells in vivo. A series of experiments were performed in order to investigate the effects of ASFV infection on porcine peripheral white blood cells. Nine pigs were inoculated by intramuscular injection with 104 50% hemadsorbing doses of virus (genotype II) distributed in Armenia and Georgia. The total number of fifteen cell types was calculated during experimental infection. RESULTS: Although band-to-segmented neutrophils ratio became much higher (3.5) in infected pigs than in control group (0.3), marked neutropenia and lymphopenia were detected from 2 to 3 days post-infection. In addition to band neutrophils, the high number of other immature white blood cells, such as metamyelocytes, was observed during the course of infection. From the beginning of infection, atypical lymphocytes, with altered nuclear shape, arose and became 15% of total cells in the final phase of infection. Image scanning cytometry revealed hyperdiploid DNA content in atypical lymphocytes only from 5 days post-infection, indicating that DNA synthesis in pathological lymphocytes occurred in the later stages of infection. CONCLUSION: From this study, it can be concluded that ASFV infection leads to serious changes in composition of white blood cells. Particularly, acute ASFV infection in vivo is accompanied with the emergence of immature cells and atypical lymphocytes in the host blood. The mechanisms underlying atypical cell formation remain to be elucidated.

Functional Analysis and Proteomics Profiling of Extracellular Vesicles From Swine Plasma Infected by African Swine Fever Virus.

African swine fever (ASF) has brought excellent barriers to swine production in China and the world. Studies have shown that extracellular vesicles mediate the RNA and protein spread of pathogenic microorganisms and RNA and proteins. After infection by pathogenic microorganisms causes significant differences in the proteins contained within extracellular vesicles. Based on the above studies, the extracellular vesicles were extracted from ASF virus (ASFV)-infected swine plasma. And qPCR, western blot, and confocal experiment were carried out. The research shows that extracted extracellular vesicles significantly promote the replication of ASFV in susceptible and non-susceptible cells Proteomics analysis of the extracellular vesicle proteins revealed that ASFV infection could cause significant differences in the protein profile. This study demonstrates that extracellular vesicles play a critical role in ASFV replication and transmission and cause significant differences in the protein profile encapsulated in extracellular vesicles.

Characterization of African swine fever virus Caucasus isolate in European wild boars.

Since 2007, African swine fever has spread from the Caucasus region. To learn more about the dynamics of the disease in wild boars (Sus scrofa), we conducted experiments by using European wild boars. We found high virulence of Caucasus isolates limited potential for establishment of endemicity.

[Pathology of lymphoid tissue cells infected by African swine fever virus in vitro].

The authors studied the pathology of bone marrow (BM) lymphoid cell from pigs infected by African swine fever virus (ASFV) in vitro. Monocytes were shown to be primarily afflicted in unstimulated BM culture. These cells disappeared completely 72 hours after infection. Just 24 hours following ASFV infection, there were atypical lymphocytes amounting to 12% of the general lymphoid population at hour 72 after inoculation.The area and perimeter of minor, middle, and large lymphocytes tended to reduce during both BM cell cultivation and inoculation. Lymphoblasts and monocytes were generally triploid in both the control and test groups, but among them there were diploid, triploid, and tetraploid cells. Cytophotometric assay revealed that the amount of nuclear DNA significantly increased in BM lymphoblasts and monocytes in the early stages of ASFV infection (within 24 hours). This effect was also rather pronounced in the lymphoblasts in the later stages (at hour 72).

African Swine Fever Virus pE199L Induces Mitochondrial-Dependent Apoptosis.

African swine fever (ASF) is a severe hemorrhagic disease in swine characterized by massive lymphocyte depletion and cell death, with apoptosis and necrosis in infected lymphoid tissues. However, the molecular mechanism regarding ASFV-induced cell death remains largely unknown. In this study, 94 ASFV-encoded proteins were screened to determine the viral proteins involved in cell death in vitro, and pE199L showed the most significant effect. Ectopic expression of pE199L in porcine cells (CRL-2843) and human cells (HEK293T and HeLa cells) induced cell death remarkably, showing obvious shrinking, blistering, apoptotic bodies, and nuclear DNA fragments. Meanwhile, cell death was markedly alleviated when the expression of pE199L was knocked down during ASFV infection. Additionally, the expression of pE199L caused a loss of mitochondrial membrane potential, release of cytochrome C, and caspase-9 and -3/7 activation, indicating that the mitochondrial apoptotic pathway was involved in pE199L-induced apoptosis. Further investigations showed that pE199L interacted with several anti-apoptotic BCL-2 subfamily members (such as BCL-XL, MCL-1, BCL-W, and BCL-2A1) and competed with BAK for BCL-XL, which promoted BAK and BAX activation. Taken together, ASFV pE199L induces the mitochondrial-dependent apoptosis, which may provide clues for a comprehensive understanding of ASFV pathogenesis.

Development and In Vivo Evaluation of a MGF110-1L Deletion Mutant in African Swine Fever Strain Georgia.

African swine fever (ASF) is currently causing an epizootic, affecting pigs throughout Eurasia, and causing significant economic losses in the swine industry. ASF is caused by African swine fever virus (ASFV) that consists of a large dsDNA genome that encodes for more than 160 genes; few of these genes have been studied in detail. ASFV contains four multi-gene family (MGF) groups of genes that have been implicated in regulating the immune response and host specificity; however, the individual roles of most of these genes have not been well studied. Here, we describe the evaluation of the previously uncharacterized ASFV MGF110-1L open reading frame (ORF) using a deletion mutant of the ASFV currently circulating throughout Eurasia. The recombinant ASFV lacking the MGF110-1L gene (ASFV-G-ΔMGF110-1L) demonstrated in vitro that the MGF110-1L gene is non-essential, since ASFV-G-ΔMGF110-1L had similar replication kinetics in primary swine macrophage cell cultures when compared to parental highly virulent field isolate Georgia2007 (ASFV-G). Experimental infection of domestic pigs with ASFV-G-ΔMGF110-1L produced a clinical disease similar to that caused by the parental ASFV-G, confirming that deletion of the MGF110-1L gene from the ASFV genome does not affect viral virulence.

The Role of Male Reproductive Organs in the Transmission of African Swine Fever-Implications for Transmission.

African swine fever (ASF) has evolved from an exotic animal disease to a threat to global pig production. An important avenue for the wide-spread transmission of animal diseases is their dissemination through boar semen used for artificial insemination. In this context, we investigated the role of male reproductive organs in the transmission of ASF. Mature domestic boars and adolescent wild boars, inoculated with different ASF virus strains, were investigated by means of virological and pathological methods. Additionally, electron microscopy was employed to investigate in vitro inoculated sperm. The viral genome, antigens and the infectious virus could be found in all gonadal tissues and accessory sex glands. The viral antigen and viral mRNAs were mainly found in mononuclear cells of the respective tissues. However, some other cell types, including Leydig, endothelial and stromal cells, were also found positive. Using RNAScope, p72 mRNA could be found in scattered halo cells of the epididymal duct epithelium, which could point to the disruption of the barrier. No direct infection of spermatozoa was observed by immunohistochemistry, or electron microscopy. Taken together, our results strengthen the assumption that ASFV can be transmitted via boar semen. Future studies are needed to explore the excretion dynamics and transmission efficiency.

Emergence of African swine fever virus, northwestern Iran.

In 2008, African swine fever was introduced into Georgia, after which it spread to neighboring Armenia, Azerbaijan, and the Russian Federation. That same year, PCR and sequence analysis identified African swine fever virus in samples from 3 dead female wild boars in northwestern Iran. Wild boars may serve as a reservoir.