Evaluation of immunogenicity of gene-deleted and subunit vaccines constructed against the emerging pseudorabies virus variants.

BACKGROUND: Pseudorabies (PR) (also called Aujeszky's disease, AD) is a serious infectious disease affecting pigs and other animals worldwide. The emergence of variant strains of pseudorabies virus (PRV) since 2011 has led to PR outbreaks in China and a vaccine that antigenically more closely matches these PRV variants could represent an added value to control these infections. METHODS: The objective of this study was to develop new live attenuated and subunit vaccines against PRV variant strains. Genomic alterations of vaccine strains were based on the highly virulent SD-2017 mutant strain and gene-deleted strains SD-2017ΔgE/gI and SD-2017ΔgE/gI/TK, which constructed using homologous recombination technology. PRV gB-DCpep (Dendritic cells targeting peptide) and PorB (the outer membrane pore proteins of N. meningitidis) proteins containing gp67 protein secretion signal peptide were expressed using the baculovirus system for the preparation of subunit vaccines. We used experimental animal rabbits to test immunogenicity to evaluate the effect of the newly constructed PR vaccines. RESULTS: Compared with the PRV-gB subunit vaccine and SD-2017ΔgE/gI inactivated vaccines, rabbits (n = 10) that were intramuscularly vaccinated with SD-2017ΔgE/gI/TK live attenuated vaccine and PRV-gB + PorB subunit vaccine showed significantly higher anti-PRV-specific antibodies as well as neutralizing antibodies and IFN-γ levels in serum. In addition, the SD-2017ΔgE/gI/TK live attenuated vaccine and PRV-gB + PorB subunit vaccine protected (90-100%) rabbits against homologous infection by the PRV variant strain. No obvious pathological damage was observed in these vaccinated rabbits. CONCLUSIONS: The SD-2017ΔgE/gI/TK live attenuated vaccine provided 100% protection against PRV variant challenge. Interestingly, the subunit vaccines with gB protein linked to DCpep and PorB protein as adjuvant may also be a promising and effective PRV variant vaccine candidate.

Genetic analysis of porcine circovirus type 2 from dead minks.

Circovirus infection is a growing problem in the field of veterinary and public health. It is associated with enteric diseases in both mammalian and avian hosts. In this study, we detected and isolated porcine circovirus strains in the tissue samples of minks that died from diarrhoea in Shandong Province, China. We sequenced the whole genome of two porcine strains of Circovirus, designated as MiSD-1 and MiSD-2， which had a 97.34% similarity on nucleotide sequence and were closely related to porcine circovirus type 2 (PCV2), but distantly related to mink circoviral species. Phylogenetically MiSD-1 and MiSD-2 are a part of the PCV2b genotype cluster, which is a highly prevalent genotype worldwide. The closer relationship of MiSD-1 and MiSD-2 to PCV2 from pigs than to other mink circoviral species may be evidence of cross-species transmission and considerable zoonotic potential.

Detection of Multi-drug Resistant Acinetobacter Lwoffii Isolated from Soil of Mink Farm.

There were 4 Acinetobacter lwoffii obtained from soil samples. The antimicrobial susceptibility of the strains to 16 antimicrobial agents was investigated using K-B method. Three isolates showed the multi-drug resistance. The presence of resistance genes and integrons was determined using PCR. The aadA1, aac(3')-IIc, aph(3')-VII, aac(6')-Ib, sul2, cat2, floR, and tet(K) genes were detected, respectively. Three class 1 integrons were obtained. The arr-3-aacA4 and blaPSE-1 gene cassette, which cause resistance to aminoglycoside and beta-lactamase antibiotics. Our results reported the detection of multi-drug resistant and carried resistant genes Acinetobacter lwoffii from soil. The findings suggested that we should pay close attention to the prevalence of multi-drug resistant bacterial species of environment.

Effect of Nonstructural Protein 2 Hypervariable Regions in the Replication of Porcine Reproductive and Respiratory Syndrome Virus in Marc-145 Cells.

BACKGROUND: Highly pathogenic (HP) porcine reproductive and respiratory syndrome virus (PRRSV) causes prolonged high fever, red discoloration of the body, blue ears and a high mortality. Previously, we found that the PRRSV vaccine strain TJM contained a deletion of 120 amino acids (aa 628-747) in nonstructural protein 2 (Nsp2). We aimed to explore the replication features of PRRSV after adding the transiently expressed product of these 120 aa in vitro. METHODS: We constructed seven eukaryotic expression plasmids containing different parts of the 120-aa sequence, transfected them into Marc-145 cells and then inoculated the cells with 103 TCID50 TJM per well. We detected virus replication at mRNA and protein level by real-time RT-PCR and Western blotting, respectively, and determined the virus titer. RESULTS: The transiently expressed 120 aa and one of its truncated polypeptides inhibited PRRSV TJM propagation on Marc-145 cells. The complete 120-aa sequence induced a remarkable decrease in PRRSV replication, causing a reduction in structural protein levels between 36 and 48 h after infection. Additionally, aa 628-727 partly reduced the replication of PRRSV on Marc-145 cells. CONCLUSIONS: The 120 aa from Nsp2, especially aa 628-727, play a negative role in PRRSV TJM proliferation.

Novel amdoparvovirus infecting farmed raccoon dogs and arctic foxes.

A new amdoparvovirus, named raccoon dog and fox amdoparvovirus (RFAV), was identified in farmed sick raccoon dogs and arctic foxes. Phylogenetic analyses showed that RFAV belongs to a new species within the genus Amdoparvovirus of the family Parvoviridae. An RFAV strain was isolated in Crandell feline kidney cell culture.

Acquisition of different transcriptional shear mRNA and biological function of porcine interleukin 18 binding protein in PRRSV infection.

Interleukin-18 binding protein (IL-18BP), a natural regulator molecule of the pro-inflammatory cytokine interleukin-18 (IL-18), plays an important role in regulating the expression of the cellular immunity factor interferon-γ (IFN-γ). In a previous RNA-seq analysis of porcine alveolar macrophages (PAM) infected with the TIM and TJ strains of porcine reproductive and respiratory syndrome virus (PRRSV), we unexpectedly found that the mRNA expression of porcine interleukin 18-binding protein (pIL-18BP) in PAM cells infected with the TJM strain was significantly higher than that infected with the TJ strain. Studies have shown that human interleukin-18 binding protein (hIL-18bp) plays an important role in regulating cellular immunity in the course of the disease. However, there is a research gap on pIL-18BP. At the same time, PRRSV infection in pigs triggers weak cellular immune response problems. To explore the expression and the role of pIL-18BP in the cellular immune response induced by PRRSV, we strived to acquire the pIL-18BP gene from PAM or peripheral blood mononuclear cell (PBMC) with RT-PCR and sequencing. Furthermore, pIL-18BP and pIL-18 were both expressed prokaryotically and eukaryotically. The colocalization and interaction based on recombinant pIL-18BP and pIL-18 on cells were confirmed in vitro. Finally, the expression of pIL-18BP, pIL-18, and pIFN-γ was explored in pigs with different PRRSV infection states to interpret the biological function of pIL-18BP in vivo. The results showed there were five shear mutants of pIL-18BP. The mutant with the longest coding region was selected for subsequent functional validation. First, it was demonstrated that TJM-induced pIL-18BP mRNA expression was higher than that of TJ. A direct interaction between pIL-18BP and pIL-18 was confirmed through fluorescence colocalization, bimolecular fluorescent complimentary (BIFC), and co-immunoprecipitation (CO-IP). pIL-18BP also can regulate pIFN-γ mRNA expression. Finally, the expression of pIL-18BP, pIL-18, and pIFN-γ was explored in different PRRSV infection states. Surprisingly, both mRNA and protein expression of pIL-18 were suppressed. These findings fill the gap in understanding the roles played by pIL-18BP in PRRSV infection and provide a foundation for further research.IMPORTANCEPRRSV-infected pigs elicit a weak cellular immune response and the mechanisms of cellular immune regulation induced by PRRSV have not yet been fully elucidated. In this study, we investigated the role of pIL-18BP in PRRSV-induced immune response referring to the regulation of human IL-18BP to human interferon-gamma (hIFN-γ). This is expected to be used as a method to enhance the cellular immune response induced by the PRRSV vaccine. Here, we mined five transcripts of the pIL-18BP gene and demonstrated that it interacts with pIL-18 and regulates pIFN-γ mRNA expression. Surprisingly, we also found that both mRNA and protein expression of pIL-18 were suppressed under different PRRSV strains of infection status. These results have led to a renewed understanding of the roles of pIL-18BP and pIL-18 in cellular immunity induced by PRRSV infection, which has important implications for the prevention and control of PRRS.

Evolution Characterization and Pathogenicity of an NADC34-like PRRSV Isolated from Inner Mongolia, China.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a pathogen that causes severe abortions in sows and high piglet mortality, resulting in huge economic losses to the pig industry worldwide. The emerging and novel PRRSV isolates are clinically and biologically important, as there are likely recombination and pathogenic differences among PRRSV genomes. Furthermore, the NADC34-like strain has become a major epidemic strain in some parts of China, but the characterization and pathogenicity of the latest strain in Inner Mongolia have not been reported in detail. In this study, an NADC34-like strain (CHNMGKL1-2304) from Tongliao City, Inner Mongolia was successfully isolated and characterized, and confirmed the pathogenicity in pigs. The phylogenetic tree showed that this strain belonged to sublineage 1.5 and had high homology with the strain JS2021NADC34. There is no recombination between CHNMGKL1-2304 and any other domestic strains. Animal experiments show that the CHNMGKL1-2304 strain is moderately virulent to piglets, which show persistent fever, weight loss and high morbidity but no mortality. The presence of PRRSV nucleic acids was detected in both blood, tissues, nasal and fecal swabs. In addition, obvious pathological changes and positive signals were observed in lung, lymph node, liver and spleen tissues when subjected to hematoxylin-eosin (HE) staining and immunohistochemistry (IHC). This report can provide a basis for epidemiological investigations and subsequent studies of PRRSV.

Phylogenetic analysis of the bovine parainfluenza virus type 3 from cattle herds revealing the existence of a genotype A strain in China.

In 2009, a bovine parainfluenza virus (BPIV3), named as NM09, was isolated using MDBK cell culture from the nasal swabs of normal cattle in China. The NM09 isolate was characterized by RT-PCR and nucleotide sequence analysis. Its complete genome was 15,456 nucleotides in length. Similar to other sequenced PIV strains, the NM09 virus consisted of six non-overlapping genes, which were predicted to encode nine proteins with conserved and complementary 3' leader and 5' trailer regions, conserved gene starts, gene stops, and trinucleotide intergenic sequences. Nucleotide phylogenetic analysis of matrix and hemagglutinin-neuraminidase gene demonstrated that this NM09 isolate belonged to BPIV3 genotype A instead of the previously reported BPIV3 genotype C in China. It is implicated that the different genotypes A and C might coexist infection for a long time in China.

Concurrent Gene Insertion, Deletion, and Inversion during the Construction of a Novel Attenuated BoHV-1 Using CRISPR/Cas9 Genome Editing.

Bovine herpesvirus type I (BoHV-1) is an important pathogen that causes respiratory disease in bovines. The disease is prevalent worldwide, causing huge economic losses to the cattle industry. Gene-deficient vaccines with immunological markers to distinguish them from wild-type infections have become a mainstream in vaccine research and development. In order to knock out the gE gene BoHV-1, we employed the CRISPR/Cas9 system. Interesting phenomena were observed at the single guide RNA (sgRNA) splicing site, including gene insertion, gene deletion, and the inversion of 5' and 3' ends of the sgRNA splicing site. In addition to the deletion of the gE gene, the US9 gene, and the non-coding regions of gE and US9, it was found that the US4 sequence, US6 sequence, and part of the US7 sequence were inserted into the EGFP sgRNA splicing site and the 3' end of the EGFP sequence was deleted. Similar to the BoHV-1 parent, the BoHV-1 mutants induced high neutralizing antibodies titer levels in mice. In summary, we developed a series of recombinant gE-deletion BoHV-1 samples using the CRISPR/Cas9 gene editing system. The mutant viruses with EGFP+ or EGFP- will lay the foundation for research on BoHV-1 and vaccine development in the future.

Recombinant Bovine Herpesvirus Type I Expressing the Bovine Viral Diarrhea Virus E2 Protein Could Effectively Prevent Infection by Two Viruses.

Bovine respiratory disease complex (BRDC) is a comprehensive disease in cattle caused by various viral and bacterial infections. Among them, bovine herpesvirus type I (BoHV-1) and bovine viral diarrhea virus (BVDV) play important roles and have caused huge financial losses for the cattle industry worldwide. At present, vaccines against BRDC include trivalent attenuated BoHV-1, BVDV-1, and BVDV-2 live vaccines, BoHV-1 live attenuated vaccines, and BoHV-1/BVDV bivalent live attenuated vaccines, which have limitations in terms of their safety and efficacy. To solve these problems, we optimized the codon of the BVDV-1 E2 gene, added the signal peptide sequence of the BoHV-1 gD gene, expressed double BVDV-1 E2 glycoproteins in tandem at the BoHV-1 gE gene site, and constructed a BoHV-1 genetics-engineered vectored vaccine with gE gene deletion, named BoHV-1 gE/E2-Linker-E2+ and BoHV-1 ΔgE. This study compared the protective effects in BoHV-1, BoHV-1 ΔgE, BoHV-1 gE/E2-Linker-E2+, and BVDV-1 inactivated antigen immunized guinea pigs and calves. The results showed that BoHV-1 gE/E2-Linker-E2+ could successfully induce guinea pigs and calves to produce specific neutralizing antibodies against BVDV-1. In addition, after BoHV-1 and BVDV-1 challenges, BoHV-1 gE/E2-Linker-E2+ can produce a specific neutralizing antibody response against BoHV-1 and BVDV-1 infections. Calves immunized with this type of virus can be distinguished as either vaccinated animals (gE-) or naturally infected animals (gE+). In summary, our data suggest that BoHV-1 gE/E2-Linker-E2+ and BoHV-1 ΔgE have great potential to prevent BVDV-1 or BoHV-1 infection.

Subunit vaccine based on glycoprotein B protects pattern animal guinea pigs from tissue damage caused by infectious bovine rhinotracheitis virus.

Infectious bovine rhinotracheitis (IBR) is caused by Bovine herpesvirus type 1 (BoHV-1), which seriously threatens the global cattle industry. Only vaccination to improve immunity is the most direct and effective means to prevent IBR. Attempts are being made to use subunit vaccines, deleted or recombinant viral vaccines to reduce or eradicate IBR. For investigating the immunological characteristics of glycoprotein B subunit vaccine in pattern animal guinea pigs, the partial glycoprotein B (gB) of BoHV-1 with dominant antigenic characteristic was selected. A recombinant prokaryotic expression vector pET-32a-gB with the truncated gB gene was constructed, expressed, identified and the purified proteins were used to immunize guinea pigs. The immune effect of the subunit vaccine was assessed by monitoring clinical symptoms, viral load, antibody secretion, and histopathological changes. The results indicated that guinea pigs immunized with the gB subunit vaccine produced high levels of anti-gB antibodies and virus-neutralizing antibodies. The gB subunit vaccine significantly reduced viral shedding and lung tissue damage after IBRV challenge. The animals inoculated the gB subunit vaccine also had less virus reactivation. Its protective effect on viral shedding and tissue damage was similar to that of inactivated BoHV-1 vaccine. This work is a proof-of-concept study of subunit vaccine-induced protection against BoHV-1. And it is expected to be a candidate vaccine for the prevention of IBR.

Recent advances in the study of NADC34-like porcine reproductive and respiratory syndrome virus in China.

Since porcine reproductive and respiratory syndrome virus (PRRSV) was first described in China in 1996, several genetically distinct strains of PRRSV have emerged with varying pathogenicity and severity, thereby making the prevention and control of PRRS more difficult in China and worldwide. Between 2017 and 2021, the detection rate of NADC34-like strain in China increased. To date, NADC34-like strains have spread to 10 Chinese provinces and have thus developed different degrees of pathogenicity and mortality. In this review, we summarize the history of NADC34-like strains in China and clarify the prevalence, genomic characteristics, restriction fragment length polymorphisms, recombination, pathogenicity, and vaccine status of this strain in China. In so doing, this study aims to provide a basis for the further development of prevention and control measures targeting the NADC34-like strain.

Pathogenesis and phylogenetic analyses of canine distemper virus strain ZJ7 isolate from domestic dogs in China.

A new isolate of canine distemper virus (CDV), named ZJ7, was isolated from lung tissues of a dog suspected with CDV infection using MDCK cells. The ZJ7 isolate induced cytopathogenic effects of syncytia in MDCK cell after six passages. In order to evaluate pathogenesis of ZJ7 strain, three CDV sero-negative dogs were intranasally inoculated with its virus suspension. All infected dogs developed clinical signs of severe bloody diarrhea, conjunctivitis, ocular discharge, nasal discharge and coughing, fever and weight loss at 21 dpi, whereas the mock group infected with DMEM were normal. The results demonstrated that CDV-ZJ7 strain isolated by MDCK cell was virulent, and the nucleotide and amino acid sequences of strain ZJ7 had no change after isolation by MDCK cell when compared with the original virus from the fresh tissues. Molecular and phylogenetic analyses for the nucleocapsid (N), phosphoprotein (P) and receptor binding haemagglutinin (H) gene of the ZJ7 isolate clearly showed it is joins to the Asia 1 group cluster of CDV strains, the predominant genotype in China.

Transcriptome sequencing analysis of porcine alveolar macrophages infected with PRRSV strains to elucidate virus pathogenicity and immune evasion strategies.

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) causes a serious disease to the swine industry worldwide. To understand the mechanisms of HP-PRRSV infection, RNA-seq-based transcriptome analyses were performed on porcine alveolar macrophages (PAMs) infected with a HP-PRRSV strain (TJ), a less virulent strain of a classical lineage (CH-1a), and a vaccine strain TJM-F92. Gene ontology, Kyoto Encyclopedia of Genes and Genomes analyses indicate that TJM-F92 led to significant up-regulation of gene expression for proteins associated with membrane-bound organelles. The differentially expressed genes of HP-PRRSV TJ-infected PAM cells were up-regulated in the special G-protein coupled receptor. The six cytokines were tested by real time Reverse Transcription-Polymerase Chain Reaction (RT-PCR). The relative expression levels showed the same trend of expression difference. Significant up-regulation of TMEM173 plays an important role in the cytosolic DNA-sensing pathway and the RIG-I-like receptor signaling pathway in TJM-F92 infected PAM cells. These data provide new insight into PRRSV pathogenicity and immune evasion strategies.

Development of monoclonal antibody for differentiating porcine reproductive and respiratory syndrome virus and identification of a novel non-structural protein 2 epitope peptide.

Porcine reproductive and respiratory syndrome virus (PRRSV) nucleocapsid protein (NP) is the immunodominant region of PRRSV viral proteins. Non-structural protein 2 (Nsp2) and its hypervariable region play an essential role in the differential diagnosis of PRRSV. Western blot and immunofluorescence assay (IFA) analyses found that 2 out of 18 monoclonal antibodies (MAbs) recognized the NP and that 5 of 11 MAbs recognized Nsp2-120aa. IFA data demonstrated that 2 MAbs raised against the NP have a positive reaction to PRRSV; either HP-PRRSV, classic PRRSV or the vaccine strain at 1:100 dilution. Two MAbs raise against Nsp2-120aa also react positively with the classic PRRSV nor HP-PRRSV, but not with the PRRSV vaccine strain TJM-F92. Epitope mapping using truncated proteins identified a novel Nsp2-120aa epitope. In addition, we show that MAb BR/PNsp2-2A20 recognizes a 20 amino acid peptide (707) GRFEFLPKMILETPPPHPCG (727) of Nsp2. Based on our findings, we propose that MAb BR/PNsp2-2A20, raised against Nsp2-120aa of PRRSV, as a candidate specific diagnostic MAb for differentiation of the PRRSV virulent strains infected pig from vaccine strain TJM-F92 inoculated ones. The MAbs developed here have potential for use in diagnostic and research tools, including immunofluorescence assay, enzyme-linked immunosorbent assay and Western blotting.

Reverse Transcription Cross-Priming Amplification-Nucleic Acid Test Strip for Rapid Detection of Porcine Epidemic Diarrhea Virus.

Porcine epidemic diarrhea virus (PEDV) is a highly transmissible coronavirus that causes a severe enteric disease particularly in neonatal piglets. In this study, a rapid method for detecting PEDV was developed based on cross-priming amplification and nucleic acid test strip(CPA-NATS). Five primers specific for the N gene sequence of PEDV were used for the cross-priming amplification. Detection of amplification products based on labeled probe primers was conducted with strip binding antibody of labeled markers. The CPA method was evaluated and compared with a PCR method. The reverse transcription CPA system was further optimized for detecting PEDV RNA in clinical specimens. Results showed that the method was highly specific for the detection of PEDV, and had the same sensitivity as PCR, with detection limit of 10(-6) diluted plasmid containing the target gene of PEDV. It was also successfully applied to detecting PEDV in clinical specimens. The reverse transcription CPA-NATS detection system established in this study offers a specific, sensitive, rapid, and simple detection tool for screening PEDV, which can contribute to strategies in the effective control of PEDV in swine.

Safety of inoculation of bovine parainfluenza virus 3 as potential vaccine vector in pigs.

Bovine parainfluenza virus 3 (BPIV3) is one of the most important respiratory pathogens in cattle. One BPIV3, named NM09, was isolated from cattle suffering from severe respiratory diseases in 2009. BPIV3 is a potential recombinant vaccine vector. To investigate whether NM09 can infect pigs and determine BPIV3 defense in these animals, BPIV3 antibody-free pigs were inoculated intramuscularly with the BPIV3 NM09 strain in a continuous passage. Clinical signs were observed each day after inoculation. Viral nucleic acid was detected in nasal and anal secretions. Results showed that virus-inoculated pigs displayed few observable clinical signs related to respiratory diseases. The antibody was identified, but the virus could not be detected in the second continuous passage in pigs. Thus, BPIV3 is a potential vaccine vector for genetic engineering.

Development and evaluation of two truncated recombinant NP antigen-based indirect ELISAs for detection of bovine parainfluenza virus type 3 antibodies in cattle.

Bovine parainfluenza virus type 3 (BPIV3) is one of the most important viral respiratory pathogens in both young and adult cattle. Nucleocapsid protein (NP) is the most abundant viral protein and the main regulator of virus replication and transcription. In this study, amino acid sequence data of BPIV3 NP was used to identify potential linear epitopic regions, which were subsequently used to design truncated recombinant NP antigens. The amino-terminal region (aa 9-157, NP-N) and the carboxy-terminal region (aa 391-500, NP-C) were selected, and these two truncated recombinant BPIV3 NP proteins were expressed in Escherichia coli based on the results of prediction studies. Furthermore, Enzyme-Linked Immunosorbent Assays (ELISAs) were established using the truncated recombinant BPIV3-N proteins as antigens, and 154 clinical samples were used to evaluate the newly established ELISA systems in comparison with a virus neutralisation test (VNT) as a reference. The results showed that a high coincidence rate was observed for the data that were obtained by the two methods. The sensitivity of NP-N ELISA and NP-C ELISA were 98.4% and 94.6%, respectively, and the specificity of both ELISAs was 100% with reference to the VNTs. Our data indicated that both ends of NP have high immunogenicity during BPIV3 infection and that they were good targets for serodiagnosis. The ELISAs based on the two truncated proteins were especially suitable for use in large-scale epidemiological investigations.

Novel Nsp2 deletion based on molecular epidemiology and evolution of porcine reproductive and respiratory syndrome virus in Shandong Province from 2013 to 2014.

Porcine reproductive and respiratory syndrome (PRRS) is an economically important swine disease affecting swine worldwide. In this study, a total of 385 samples were collected from Shandong pig farms during 2013 and 2014, when pigs were not inoculated with any vaccine. Results indicated that, out of 385 samples, 47 (12.21%) were PRRSV-RNA-positive. The gene sequence analysis of 12 ORF5, 12 ORF7, and 8 Nsp2 of these samples was used to determine the molecular epidemiology of PRRSV in different parts of China's Shandong Province. The phylogenetic tree based on these 3 genes indicated that the Chinese PRRSV strains could be divided into five subgroups and two large groups. The 8 study strains were clustered into subgroup IV, another 4 strains into subgroup I. The first 8 strains shared considerable homology with VR-2332 in ORF5 (96-97.5%), the other 4 strains shared considerable homology with JXA1 (94-98%). Phylogenetic tree of GP5 showed that the eight isolates formed a tightly novel clustered branch, subgroup V, which resembled but differed from isolate VR-2332. When examined using Nsp2 alone, the first 8 strains showed considerable homology with a U.S. vaccine strain, Ingelvac MLV (89.6-98.4%). One novel pattern of deletion was observed in Nsp2. The genetic diversity of genotype 2 PRRSV tended to vary in the field. The emergence of novel variants will probably be the next significant branch of PRRSV study.

[Eenie, Meenie, Miney, Moe, who is responsible for the antibody-dependent enhancement of Aleutian mink disease parvovirus infection?].

Aleutian mink disease parvovirus (AMDV) causes a persistent infection associated with immune complex disease, hypergammaglobulinemia, and high levels of antiviral antibodies. Despite the presence of an antibody, the virus is not cleared in vivo. Pre-existing antibodies may enhance viral infections, by Fc-receptor-mediated antibody-dependent enhancement (ADE), but the mechanism that underlies ADE has not been fully defined. Three models have been proposed, including: (1) interactions between antibody and FcR, complement C3 fragment and CR, or between C1q and C1qR, which promotes viral attachment to cells; (2) suppression of IFN-gamma-mediated host-cell antiviral gene expression by the upregulation of negative regulators of pathogen pattern recognition; and (3) the promotion of early IL-10 secretion. In addition, the role of cytokine IL-6 in ADE mediated disease development is discussed, to facilitate a better understanding of the pathogenesis of AMDV infection, as well as give insights into rational vaccine design approaches.