Geospatial analysis for strategic wildlife disease surveillance: African swine fever in South Korea (2019-2021).

Since the confirmation of African swine fever (ASF) in South Korea in 2019, its spread, predominantly in wild boars, has been a significant concern. A key factor in this situation is the lack of identification of risk factors by surveillance bias. The unique orography, characterized by high mountains, complicates search efforts, leading to overlooked or delayed case detection and posing risks to the swine industry. Additionally, shared rivers with neighboring country present a continual threat of virus entry. This study employs geospatial analysis and statistical methods to 1) identify areas at high risk of ASF occurrence but possibly under-surveilled, and 2) indicate strategic surveillance points for monitoring the risk of ASF virus entry through water bodies and basin influences. Pearson's rho test indicated that elevation (rho = -0.908, p-value < 0.001) and distance from roads (rho = -0.979, p-value < 0.001) may have a significant impact on limiting surveillance activities. A map of potential under-surveilled areas was created considering these results and was validated by a chi-square goodness-of-fit test (X-square = 208.03, df = 1, p-value < 0.001). The strong negative correlation (rho = -0.997, p-value <0.001) between ASF-positive wild boars and distance from water sources emphasizes that areas surrounding rivers are one of the priority areas for monitoring. The subsequent hydrological analyses provided important points for monitoring the risk of virus entry via water from the neighboring country. This research aims to facilitate early detection and prevent further spread of ASF.

Identification of two novel B cell epitopes on E184L protein of African swine fever virus using monoclonal antibodies.

African swine fever virus (ASFV) is a large double-stranded DNA virus with a complex structural architecture and encodes more than 150 proteins, where many are with unknown functions. E184L has been reported as one of the immunogenic ASFV proteins that may contribute to ASFV pathogenesis and immune evasion. However, the antigenic epitopes of E184L are not yet characterized. In this study, recombinant E184L protein was expressed in prokaryotic expression system and four monoclonal antibodies (mAbs), designated as 1A10, 2D2, 3H6, and 4C10 were generated. All four mAbs reacted specifically with ASFV infected cells. To identify the epitopes of the mAbs, a series of overlapped peptides of E184L were designed and expressed as maltose binding fusion proteins. Accordingly, the expressed fusion proteins were probed with each E184L mAb separately by using Western blot. Following a fine mapping, the minimal linear epitope recognized by mAb 1A10 was identified as 119IQRQGFL125, and mAbs 2D2, 3H6, and 4C10 recognized a region located between 153DPTEFF158. Alignment of amino acids of E184L revealed that the two linear epitopes are highly conserved among different ASFV isolates. Furthermore, the potential application of the two epitopes in ASFV diagnosis was assessed through epitope-based ELISA using 24 ASFV positive and 18 negative pig serum and the method were able to distinguish positive and negative samples, indicating the two epitopes are dominant antigenic sites. To our knowledge, this is the first study to characterize the B cell epitopes of the antigenic E184L protein of ASFV, offering valuable tools for future research, as well as laying a foundation for serological diagnosis and epitope-based marker vaccine development.

The evolutionary and genetic patterns of African swine fever virus.

African swine fever (ASF) is a serious animal disease, and has spread to Africa, Europe and Asia, causing massive economic losses. African swine fever virus (ASFV) is transmitted from a reservoir host (warthog) to domestic pigs via a sylvatic cycle (transmission between warthogs and soft ticks) and a domestic cycle (transmission between domestic pigs) and survives by expressing a variety of genes related to virus-host interactions. We evaluated differences in codon usage patterns among ASFV genotypes and clades and explored the common and specific evolutionary and genetic characteristics of ASFV sequences. We analysed the evolutionary relationships, nucleotide compositions, codon usage patterns, selection pressures (mutational pressure and natural selection) and viral adaptation to host codon usage based on the coding sequences (CDS) of key functional genes of ASFV. AT bias was detected in the six genes analysed, irrespective of clade. The AT bias of genes (A224L, A179L, EP153R) encoding proteins involved in interaction with host cells after infection was high; among them, the AT bias of EP153R was the greatest at 78.3%. A large number of overrepresented codons were identified in EP153R, whereas there were no overrepresented codons with a relative synonymous codon usage (RSCU) value of ≥3 in B646L. In most genes, the pattern of selection pressure was similar for each clade, but in EP153R, diverse patterns of selection pressure were captured within the same clade and genotype. As a result of evaluating host adaptation based on the codon adaptation index (CAI), for B646L, E183L, CP204L and A179L, the codon usage patterns in all sequences were more similar to tick than domestic pig or wild boar. However, EP153R showed the lowest average CAI value of 0.52 when selecting tick as a reference set. The genes analysed in this study showed different magnitudes of selection pressure at the clade and genotype levels, which is likely to be related to the function of the encoded proteins and may determine key evolutionary traits of viruses, such as the level of genetic variation and host range. The diversity of codon adaptations at the genetic level in ASFV may account for differences in translational selection in ASFV hosts and provides insight into viral host adaptation and co-evolution.

A proposed update of African swine fever virus (genotype II) subgenotyping based on the central variable region (CVR) of Russian isolates.

African swine fever virus (ASFV) isolates are grouped and tracked through analysis of their central variable region (CVR) sequences. In this study, sequences of 70 ASFV isolates collected from different regions of Russia between 2018 and 2022 were analyzed. The analysis based on the CVR sequences indicated that the isolates belonged to three distinct groups. Group 1 shared 100% sequence identity to the isolate Georgia 2007/1. Group 5 had a C > A single-nucleotide polymorphism (SNP) at position 601, while group 13 is new and unique to the Far East of Russia, with five isolates from the Amur, Khabarovsk, and Primorsky regions. These findings demonstrate a new approach to phylogenomics and cladistics of ASFV isolates within genotype II on the basis of the CVR.

Transcriptome profiles of organ tissues from pigs experimentally infected with African swine fever virus in early phase of infection.

African swine fever, caused by African swine fever virus (ASFV), is a highly contagious and fatal disease that poses a significant threat to the global pig industry. The limited information on ASFV pathogenesis and ASFV-host interactions has recently prompted numerous transcriptomic studies. However, most of these studies have focused on elucidating the transcriptome profiles of ASFV-infected porcine alveolar macrophages in vitro. Here, we analyzed dynamic transcriptional patterns in vivo in nine organ tissues (spleen, submandibular lymph node, mesenteric lymph node, inguinal lymph node, tonsils, lungs, liver, kidneys, and heart) obtained from pigs in the early stages of ASFV infection (1 and 3 d after viremia). We observed rapid spread of ASFV to the spleen after viremia, followed by broad transmission to the liver and lungs and subsequently, the submandibular and inguinal lymph nodes. Profound variations in gene expression patterns were observed across all organs and at all time-points, providing an understanding of the distinct defence strategies employed by each organ against ASFV infection. All ASFV-infected organs exhibited a collaborative response, activating immune-associated genes such as S100A8, thereby triggering a pro-inflammatory cytokine storm and interferon activation. Functional analysis suggested that ASFV exploits the PI3K-Akt signalling pathway to evade the host immune system. Overall, our findings provide leads into the mechanisms underlying pathogenesis and host immune responses in different organs during the early stages of infection, which can guide further explorations, aid the development of efficacious antiviral strategies against ASFV, and identify valuable candidate gene targets for vaccine development.

Development of novel monoclonal antibodies for blocking NF-κB activation induced by CD2v protein in African swine fever virus.

Background: CD2v, a critical outer envelope glycoprotein of the African swine fever virus (ASFV), plays a central role in the hemadsorption phenomenon during ASFV infection and is recognized as an essential immunoprotective protein. Monoclonal antibodies (mAbs) targeting CD2v have demonstrated promise in both diagnosing and combating African swine fever (ASF). The objective of this study was to develop specific monoclonal antibodies against CD2v. Methods: In this investigation, Recombinant CD2v was expressed in eukaryotic cells, and murine mAbs were generated through meticulous screening and hybridoma cloning. Various techniques, including indirect enzyme-linked immunosorbent assay (ELISA), western blotting, immunofluorescence assay (IFA), and bio-layer interferometry (BLI), were employed to characterize the mAbs. Epitope mapping was conducted using truncation mutants and epitope peptide mapping. Results: An optimal antibody pair for a highly sensitive sandwich ELISA was identified, and the antigenic structures recognized by the mAbs were elucidated. Two linear epitopes highly conserved in ASFV genotype II strains, particularly in Chinese endemic strains, were identified, along with a unique glycosylated epitope. Three mAbs, 2B25, 3G25, and 8G1, effectively blocked CD2v-induced NF-κB activation. Conclusions: This study provides valuable insights into the antigenic structure of ASFV CD2v. The mAbs obtained in this study hold great potential for use in the development of ASF diagnostic strategies, and the identified epitopes may contribute to vaccine development against ASFV.

In vitro phenotypic characterisation of two genotype I African swine fever viruses with genomic deletion isolated from Sardinian wild boars.

African swine fever virus (ASFV) causes a devastating disease affecting domestic and wild pigs. ASF was first introduced in Sardinia in 1978 and until 2019 only genotype I isolates were identified. A remarkable genetic stability of Sardinian ASFV isolates was described, nevertheless in 2019 two wild boar isolates with a sustained genomic deletion (4342 base pairs) were identified (7303WB/19, 7212WB/19). In this study, we therefore performed in vitro experiments with monocyte-derived macrophages (moMФ) to unravel the phenotypic characteristics of these deleted viruses. Both 7303WB/19 and 7212WB/19 presented a lower growth kinetic in moMФ compared to virulent Sardinian 26544/OG10, using either a high (1) or a low (0.01) multiplicity of infection (MOI). In addition, flow cytometric analysis showed that both 7303WB/19 and 7212WB/19 presented lower intracellular levels of both early and late ASFV proteins. We subsequently investigated whether deleted virus variants were previously circulating in wild boars in Sardinia. In the four years preceding the last genotype I isolation (February 2015-January 2019), other eight wild boar isolates were collected, all belonging to p72 genotype I, B602L subgroup X, but none of them presented a sustained genomic deletion. Overall, we observed the deleted virus isolates in Sardinia only in 2019, at the end of a strong eradication campaign, and our data suggest that it might possess an attenuated phenotype in vivo. A better understanding of ASFV evolution in endemic territories might contribute to development of effective control measures against ASF.

High mortality in free-ranging wild boars associated with African swine fever virus in India.

The present study focuses on the pathological and molecular characterization of African swine fever virus (ASFV) associated with an outbreak in wild boars in two national parks in southern India in 2022-2023. Significant mortality was observed among free-ranging wild boars at Bandipur National Park, Karnataka, and Mudumalai National Park, Tamil Nadu. Extensive combing operations were undertaken in both national parks, spanning an area of around 100 km2, originating from the reported epicenter, to estimate the mortality rate. Recovered carcasses were pathologically examined, and ASFV isolates was genetically characterized. Our findings suggested spillover infection of ASFV from nearby domestic pigs, and the virus was equally pathogenic in wild boars and domestic pigs. ASFV intrusion was reported in the Northeastern region of the country, which borders China and Myanmar, whereas the current outbreak is very distantly located, in southern India. Molecular data will help in tracing the spread of the virus in the country.

Characterization of an African swine fever virus outbreak in India and comparative analysis of immune genes in infected and surviving crossbreed vs. indigenous Doom pigs.

Since 2020, African swine fever (ASF) has affected all pig breeds in Northeast India except Doom pigs, a unique indigenous breed from Assam and the closest relatives of Indian wild pigs. ASF outbreaks result in significant economic losses for pig farmers in the region. Based on sequencing and phylogenetic analysis of the B646L (p72) gene, it has been determined that ASFV genotype II is responsible for outbreaks in this region. Recent studies have shown that MYD88, LDHB, and IFIT1, which are important genes of the immune system, are involved in the pathogenesis of ASFV. The differential expression patterns of these genes in surviving ASFV-infected and healthy Doom breed pigs were compared to healthy controls at different stages of infection. The ability of Doom pigs to withstand common pig diseases, along with their genetic resemblance to wild pigs, make them ideal candidates for studying tolerance to ASFV infection. In the present study, we investigated the natural resistance to ASF in Doom pigs from an endemic area in Northeast India. The results of this study provide important molecular insights into the regulation of ASFV tolerance genes.

Porcine Circovirus Type 3 (PCV3) in Poland: Prevalence in Wild Boar Population in Connection with African Swine Fever (ASF).

Human health is dependent on food safety and, therefore, on the health of farm animals. One of the most significant threats in regard to swine diseases is African swine fever (ASF). Infections caused by porcine circoviruses (PCVs) represent another important swine disease. Due to the ubiquitous nature of PCV2, it is not surprising that this virus has been detected in ASFV-affected pigs. However, recent data indicate that coinfection of PCV3 and ASFV also occurs. It is still unclear whether PCV infection plays a role in ASFV infection, and that subject requires further analysis. The aim of this study was to assess whether PCV3 and PCV4 are present in the wild boar population in Poland (real-time PCR). The analysis was performed on wild boar samples collected for routine ASF surveillance in Poland, between 2018 and 2021. By extension, the obtained data were compared in regard to ASFV presence in these samples, thus investigating the odds of ASFV infection on the grounds of the PCV carrier state in free-ranging Suidae in Poland. In addition, sequencing of PCV3 and phylogenetic analysis were performed, based on a full genome and a capsid gene. In the current study, we demonstrated the high prevalence of PCV3 in the wild boar population in Poland; meanwhile, PCV4 was not detected. The odds of ASFV infection on the grounds of the PCV3 carrier state in free-ranging Suidae in Poland was more than twice as high. Ten full genome sequences of PCV3 were obtained, all of them belonging to clade 3a. The similarity between them was in the range of 98.78-99.80%.

Identification of an Immunodominant B-Cell Epitope in African Swine Fever Virus p30 Protein and Evidence of p30 Antibody-Mediated Antibody Dependent Cellular Cytotoxicity.

African Swine Fever Virus (ASFV) is a large dsDNA virus that encodes at least 150 proteins. The complexity of ASFV and lack of knowledge of effector immune functions and protective antigens have hindered the development of safe and effective ASF vaccines. In this study, we constructed four Orf virus recombinant vectors expressing individual ASFV genes B602L, -CP204L, E184L, and -I73R (ORFVΔ121-ASFV-B602L, -CP204L, -E184L, and -I73R). All recombinant viruses expressed the heterologous ASFV proteins in vitro. We then evaluated the immunogenicity of the recombinants by immunizing four-week-old piglets. In two independent animal studies, we observed high antibody titers against ASFV p30, encoded by CP204L gene. Using Pepscan ELISA, we identified a linear B-cell epitope of 12 amino acids in length (Peptide 15) located in an exposed loop region of p30 as an immunodominant ASFV epitope. Additionally, antibodies elicited against ASFV p30 presented antibody-dependent cellular cytotoxicity (ADCC) activity. These results underscore the role of p30 on antibody responses elicited against ASFV and highlight an important functional epitope that contributes to p30-specific antibody responses.

Rapid Detection and Quick Characterization of African Swine Fever Virus Using the VolTRAX Automated Library Preparation Platform.

African swine fever virus (ASFV) is the causative agent of a severe and highly contagious viral disease affecting domestic and wild swine. The current ASFV pandemic strain has a high mortality rate, severely impacting pig production and, for countries suffering outbreaks, preventing the export of their pig products for international trade. Early detection and diagnosis of ASFV is necessary to control new outbreaks before the disease spreads rapidly. One of the rate-limiting steps to identify ASFV by next-generation sequencing platforms is library preparation. Here, we investigated the capability of the Oxford Nanopore Technologies' VolTRAX platform for automated DNA library preparation with downstream sequencing on Nanopore sequencing platforms as a proof-of-concept study to rapidly identify the strain of ASFV. Within minutes, DNA libraries prepared using VolTRAX generated near-full genome sequences of ASFV. Thus, our data highlight the use of the VolTRAX as a platform for automated library preparation, coupled with sequencing on the MinION Mk1C for field sequencing or GridION within a laboratory setting. These results suggest a proof-of-concept study that VolTRAX is an effective tool for library preparation that can be used for the rapid and real-time detection of ASFV.

Development of a quantum dots based immunochromatographic strip for rapid and on-site detection of African swine fever virus.

African swine fever (ASF) is a lethal disease caused by ASF virus (ASFV), severely impacting the global swine industry. Though nuclear acid-based detection methods are reliable, they are laboratory-dependent. In this study, we developed a device-independent, user friendly and cost-effective quantum dots based immunochromatographic strip (QDs-ICS) with high specificity and sensitivity for the rapid and on-site detection of ASFV antigen. For the preparation of the QDs-ICS, we generated a monoclonal antibody (mAb) mAb-8G8 and polyclonal antibody (pAb) against ASFV-p72 protein. The pAb was labelled with QDs to be used as the detection probe and the mAb-8G8 was coated on the nitrocellulose membrane as the test line. Our results proved that the strip displayed no cross-reactivity with other swine viruses and detection limit of the QDs-ICS was down to 1 ng/mL for the ASFV-p72 protein with great reproducibility. The strip also exhibited high stability with a storage period up to 12 months under room temperature. Twenty blind samples and one hundred clinical samples were examined by the QDs-ICS, conventional PCR and real-time PCR method, respectively. Results showed that the agreement rate between the QDs-ICS and PCR method was 100%, and the agreement rate between the strip and real-time PCR was 94%. The novel QDs-ICS developed here would be an effective tool for on-site detection of ASFV.

African swine fever virus proteins against host antiviral innate immunity and their implications for vaccine development.

African swine fever virus (ASFV) poses a significant threat to global swine populations, necessitating a profound understanding of viral strategies against host antiviral innate immunity. This review synthesizes current knowledge regarding ASFV proteins and their intricate interactions with host defenses. Noteworthy findings encompass the modulation of interferon signaling, manipulation of inflammatory pathways, and the impact on cellular apoptosis. The implications of these findings provide a foundation for advancing vaccine strategies against ASFV. In conclusion, this review consolidates current knowledge, emphasizing the adaptability of ASFV in subverting host immunity. Identified research gaps underscore the need for continued exploration, presenting opportunities for developing targeted vaccines. This synthesis provides a roadmap for future investigations, aiming to enhance our preparedness against the devastating impact of ASFV on global swine populations.

Saccharomyces cerevisiae oral immunization in mice using multi-antigen of the African swine fever virus elicits a robust immune response.

African swine fever virus (ASFV) is one of the most complex viruses. ASFV is a serious threat to the global swine industry because no commercial vaccines against this virus are currently available except in Vietnam. Moreover, ASFV is highly stable in the environment and can survive in water, feed, and aerosols for a long time. ASFV is transmitted through the digestive and respiratory tract. Mucosal immunity is the first line of defense against ASFV. Saccharomyces cerevisiae (SC), which has been certified by the U.S. Food and Drug Administration and has a generally recognized as safe status in the food industry, was used for oral immunization in this study. ASFV antigens were effectively expressed in recombinant SC strains with high DNA copy numbers and stable growth though surface display technology and chromosome engineering (δ-integration). The recombinant SC strains containing eight ASFV antigens-KP177R, E183L, E199L, CP204L, E248R, EP402R, B602L, and B646L- induced strong humoral and mucosal immune responses in mice. There was no antigenic competition, and these antigens induced Th1 and Th2 cellular immune responses. Therefore, the oral immunization strategy using recombinant SC strains containing multiple ASFV antigens demonstrate potential for future testing in swine, including challenge studies to evaluate its efficacy as a vaccine against ASFV.

Infection of domestic pigs with a genotype II potent strain of ASFV causes cytokine storm and lymphocyte mass reduction.

The whole-genome sequence of an African swine fever virus (ASFV) strain (HuB/HH/2019) isolated from Hubei, China, was highly similar to that of the Georgia 2007/1 strain ASFV. After infection with strong strains, domestic pigs show typical symptoms of infection, including fever, depression, reddening of the skin, hemorrhagic swelling of various tissues, and dysfunction. The earliest detoxification occurred in pharyngeal swabs at 4 days post-infection. The viral load in the blood was extremely high, and ASFV was detected in multiple tissues, with the highest viral loads in the spleen and lungs. An imbalance between pro- and anti-inflammatory factors in the serum leads to an excessive inflammatory response in the body. Immune factor expression is suppressed without effectively eliciting an immune defense. Antibodies against p30 were not detected in acutely dead domestic pigs. Sequencing of the peripheral blood mononuclear cell transcriptome revealed elevated transcription of genes associated with immunity, defense, and stress. The massive reduction in lymphocyte counts in the blood collapses the body's immune system. An excessive inflammatory response with a massive reduction in the lymphocyte count may be an important cause of mortality in domestic pigs. These two reasons have inspired researchers to reduce excessive inflammatory responses and stimulate effective immune responses for future vaccine development.

Novel estimation of African swine fever transmission parameters within smallholder villages in Lao P.D.R.

African Swine Fever (ASF) disease transmission parameters are crucial for making response and control decisions when faced with an outbreak, yet they are poorly quantified for smallholder and village contexts within Southeast Asia. Whilst disease-specific factors - such as latent and infectious periods - should remain reasonably consistent, host, environmental and management factors are likely to affect the rate of disease spread. These differences are investigated using Approximate Bayesian Computation with Sequential Monte-Carlo methods to provide disease parameter estimates in four naïve pig populations in villages of Lao People's Democratic Republic. The villages represent smallholder pig farmers of the Northern province of Oudomxay and the Southern province of Savannakhet, and the model utilised field mortality data to validate the transmission parameter estimates over the course of multiple model generations. The basic reproductive number between-pigs was estimated to range from 3.08 to 7.80, whilst the latent and infectious periods were consistent with those published in the literature for similar genotypes in the region (4.72 to 6.19 days and 2.63 to 5.50 days, respectively). These findings demonstrate that smallholder village pigs interact similarly to commercial pigs, however the spread of disease may occur slightly slower than in commercial study groups. Furthermore, the findings demonstrated that despite diversity across the study groups, the disease behaved in a consistent manner. This data can be used in disease control programs or for future modelling of ASF in smallholder contexts.

Epitope mapping and establishment of a blocking ELISA for mAb targeting the p72 protein of African swine fever virus.

The African swine fever virus (ASFV) has the ability to infect pigs and cause a highly contagious acute fever that can result in a mortality rate as high as 100%. Due to the viral epidemic, the pig industry worldwide has suffered significant financial setbacks. The absence of a proven vaccine for ASFV necessitates the development of a sensitive and reliable serological diagnostic method, enabling laboratories to effectively and expeditiously detect ASFV infection. In this study, four strains of monoclonal antibodies (mAbs) against p72, namely, 5A1, 4C4, 8A9, and 5E10, were generated through recombinant expression of p72, the main capsid protein of ASFV, and immunized mice with it. Epitope localization was performed by truncated overlapping polypeptides. The results indicate that 5A1 and 4C4 recognized the amino acid 20-39 aa, 8A9 and 5E10 are recognized at 263-282 aa, which is consistent with the reported 265-280 aa epitopes. Conserved analysis revealed 20-39 aa is a high conservation of the epitopes in the ASFV genotypes. Moreover, a blocking ELISA assay for detection ASFV antibody based on 4C4 monoclonal antibody was developed and assessed. The receiver-operating characteristic (ROC) was performed to identify the best threshold value using 87 negative and 67 positive samples. The established test exhibited an area under the curve (AUC) of 0.9997, with a 95% confidence interval ranging from 99.87 to 100%. Furthermore, the test achieved a diagnostic sensitivity of 100% (with a 95% confidence interval of 95.72 to 100%) and a specificity of 98.51% (with a 95% confidence interval of 92.02 to 99.92%) when the threshold was set at 41.97%. The inter- and intra-batch coefficient of variation were below 10%, demonstrating the exceptional repeatability of the method. This method can detect the positive standard serum at a dilution as high as 1:512. Subsequently, an exceptional blocking ELISA assay was established with high diagnostic sensitivity and specificity, providing a novel tool for detecting ASFV antibodies. KEY POINTS: • Four strains of ASFV monoclonal antibodies against p72 were prepared and their epitopes were identified. • Blocking ELISA method was established based on monoclonal antibody 4C4 with an identified conservative epitope. • The established blocking ELISA method has a good effect on the detection of ASFV antibody.

Advancing vaccine development: Evaluation of a mannose-modified lipid nanoparticle-based candidate for African swine fever p30 mRNA vaccine eliciting robust immune response in mice.

The African swine fever virus (ASFV) continues to pose significant economic and pandemic risks. Consequently, discovering new, efficient vaccines is crucial. Messenger RNA (mRNA) vaccines have emerged as promising candidates, providing minimal risk of insertional mutagenesis, high safety profiles, effectiveness, rapid scalability in production, and cost-effectiveness. In this study, we have developed an ASF p30 mRNA vaccine candidate (mRNA/Man-LNP) employing mannose-modified lipid nanoparticles (LNPs). The mRNA/Man-LNP exhibited effective antigen presentation and facilitated dendritic cells (DCs) maturation. Notably, it elicited strong IgG titers and activated CD4+ and CD8+ T-cells in immunized mice, all while adhering to stringent biosafety standards. This investigation demonstrates that mRNA/Man-LNP can trigger both humoral and cellular immune responses, suggesting its potential as a potent and promising vaccine candidate for controlling African swine fever (ASF).

Modelling African swine fever introduction in diverse Australian feral pig populations.

African swine fever (ASF) is a viral disease that affects domestic and feral pigs. While not currently present in Australia, ASF outbreaks have been reported nearby in Indonesia, Timor-Leste, and Papua New Guinea. Feral pigs are found in all Australian states and territories and are distributed in a variety of habitats. To investigate the impacts of an ASF introduction event in Australia, we used a stochastic network-based metapopulation feral pig model to simulate ASF outbreaks in different regions of Australia. Outbreak intensity and persistence in feral pig populations was governed by local pig recruitment rates, population size, carcass decay period, and, if applicable, metapopulation topology. In Northern Australia, the carcass decay period was too short for prolonged persistence, while endemic transmission could possibly occur in cooler southern areas. Populations in Macquarie Marshes in New South Wales and in Namadgi National Park in the Australian Capital Territory had the highest rates of persistence. The regions had different modes of transmission that led to long-term persistence. Endemic Macquarie Marshes simulations were characterised by rapid transmission caused by high population density that required a fragmented metapopulation to act as a bottleneck to slow transmission. Endemic simulations in Namadgi, with low density and relatively slow transmission, relied on large, well-connected populations coupled with long carcass decay times. Despite the potential for endemic transmission, both settings required potentially unlikely population sizes and dynamics for prolonged disease survival.