Microcin Y utilizes its stable structure and biological activity to regulate the metabolism of intestinal probiotics and effectively clear gut Salmonella.

MccY is a novel, structurally stable microcin with antibacterial activity against Enterobacteriaceae. However, the bioavailability of orally administrated MccY is unknown. This study evaluated the effects of MccY as a antimicrobial on pre-digestion in vitro and its intake, digestion and gut metabolism in vivo. The result of pre-digestion results that MccY maintained its biological activity and was resistant to decomposition. The study established a safe threshold of 4.46-9.92 mg/kg for the MccY dosage-body weight relationship in BALB/c mice. Mice fed with MccY demonstrated improved body weight and intestinal barrier function, accompanied with increased IgM immunogenicity and decreased levels of TNF-α, IL-6, and IL-10 in the intestine. MccY significantly facilitates the growth and activity of probiotics including Lactobacillus, Prevotella, and Bacteroides, and leading to the production of SCFAs and MCFAs during bacterial interactions. Furthermore, MccY effectively protects against the inflammatory response caused by Salmonella Typhimurium infection and effectively clears the Salmonella bacteria from the gut. In conclusion, MccY is seen as a promising new therapeutic target drug for enhancing the intestinal microbe-barrier axis and preventing enteritis.

Effect of oral administration of microcin Y on growth performance, intestinal barrier function and gut microbiota of chicks challenged with Salmonella Pullorum.

The lasso peptide microcin Y (MccY) effectively inhibits various serotypes of Salmonella in vitro, but the antibacterial effect against S. Pullorum in poultry is still unclear. This study was the first to evaluate the safety and anti-S. Pullorum infection of MccY in specific pathogen-free (SPF) chicks. The safety test showed that the body weight, IgA and IgM levels of serum, and cecal microbiota structure of 3 groups of chicks orally administrated with different doses of MccY (5 mg/kg, 10 mg/kg, 20 mg/kg) for 14 days were not significantly different from those of the control group. Then, the chicks were randomized into 3 groups for the experiment of anti-S. Pullorum infection: (I) negative control group (NC), (II) S. Pullorum-challenged group (SP, 5 × 108 CFU/bird), (III) MccY-treated group (MccY, 20 mg/kg). The results indicated that compared to the SP group, treatment of MccY increased body weight and average daily gain (P < 0.05), reduced S. Pullorum burden in feces, liver, and cecum (P < 0.05), enhanced the thymus, and decreased the spleen and liver index (P < 0.05). Additionally, MccY increased the jejunal villus height, lowered the jejunal and ileal crypt depth (P < 0.05), and upregulated the expression of IL-4, IL-10, ZO-1 in the jejunum and ileum, as well as CLDN-1 in the jejunum (P < 0.05) compared to the SP group. Furthermore, MccY increased probiotic flora (Barnesiella, etc.), while decreasing (P < 0.05) the relative abundance of pathogenic flora (Escherichia and Salmonella, etc.) compared to the SP group.

Lasso peptide MccY alleviates non-typhoidal salmonellae-induced mouse gut inflammation via regulation of intestinal barrier function and gut microbiota.

IMPORTANCE: Diseases caused by Enterobacteriaceae multidrug-resistant strains have become increasingly difficult to manage. It is necessary to verify the new antibacterial drug MccY effect on non-typhoid Salmonella infection in mice since it is regarded as a promising microcin. The results demonstrated that MccY has a potential therapeutic application value in the protection against Salmonella-induced intestinal damage and alleviating related intestinal dysbiosis and metabolic disorders. MccY could be a promising candidate as an antimicrobial or anti-inflammatory agent for treating infectious diseases.

Resistance Mechanism and Physiological Effects of Microcin Y in Salmonella enterica subsp. enterica Serovar Typhimurium.

Salmonella bacteria pose a significant threat to animal husbandry and human health due to their virulence and multidrug resistance. The lasso peptide MccY is a recently discovered antimicrobial peptide that acts against various serotypes of Salmonella. In this study, we further explore the resistance mechanism and activity of MccY. Mutants of Ton system genes, including tonB, exbB, and exbD, in Salmonella enterica subsp. enterica serovar Typhimurium were constructed, and the MICs to MccY exhibited significant increases in these deletion mutants compared to the MIC of the parent strain. Subsequently, MccY resistance was quantitatively analyzed, and these mutants also showed greatly reduced rates of killing, even with a high concentration of MccY. In addition, a minimal medium with low iron environment enhanced the sensitivity of these mutants to MccY. Measurements of a series of physiological indicators, including iron utilization, biofilm formation, and motility, demonstrated that MccY may decrease the virulence of S. Typhimurium. Transcriptomic analysis showed that iron utilization, biofilm formation, flagellar assembly, and virulence-related genes were downregulated to varying degrees when S. Typhimurium was treated with MccY. In conclusion, deletion of Ton system genes resulted in resistance to MccY and the susceptibility of these mutants to MccY was increased and differed under a low-iron condition. This lasso peptide can alter multiple physiological properties of S. Typhimurium. Our study will contribute to improve the knowledge and understanding of the mechanism of MccY resistance in Salmonella strains. IMPORTANCE The resistance of Salmonella to traditional antibiotics remains a serious challenge. Novel anti-Salmonella drugs are urgently needed to address the looming crisis. The newly identified antimicrobial peptide MccY shows broad prospects for development and application because of its obvious antagonistic effect on various serotypes of Salmonella. However, our previous study showed that the peptide could confer resistance to Salmonella by disrupting the receptor gene fhuA. In this study, we further explored the potential resistance mechanism of MccY and demonstrated the importance of the Salmonella Ton complex for MccY transport. Disruption in Ton system genes resulted in S. Typhimurium resistance to this peptide, and MccY could alter multiple bacterial physiological properties. In summary, this study further explored the resistance mechanism and antibacterial effect of MccY in S. Typhimurium and provided a scientific basis for its development and application.

Chicken telomerase reverse transcriptase promotes the tumorigenicity of avian leukosis virus subgroup J by regulating the Wnt/ß-catenin signaling pathway.

This research aimed to analyze the regulatory effect of chicken telomerase reverse transcriptase (chTERT) on the Wnt/ß-catenin signaling pathway and its effect on the tumorigenicity of avian leukosis virus subgroup J (ALV-J) through in vivo experiments. The chTERT eukaryotic expression plasmid and its recombinant lentivirus particles were constructed for in vivo transfection of chTERT to analyze the effect of chTERT continuously overexpressed in chickens on the tumorigenicity of ALV-J. During 156 days of the artificial ALV-J tumor-inducing process, 7 solid tumors developed in 3 chickens in the chTERT-overexpression group (n = 26*2) and no tumors developed in the control group (n = 26*2). Another 18 tumors induced by ALV-J were confirmed and collected from breeding poultry farms. And we confirmed that chTERT was significantly highly expressed in ALV-J tumors. The ELISA data suggested that the protein levels of ß-catenin and c-Myc in the chicken plasma of the chTERT-overexpressing group with ALV-J infected were consistently and significantly higher than those of the control group. Compared with that of the tumor-adjacent tissues, the activity of the Wnt/ß-catenin signaling pathway and expression of the c-Myc was significantly increased in ALV-J tumors. And the percentage of apoptosis in ALV-J tumors significantly lower than that in tumor-adjacent tissues. Immunohistochemistry, Western blot and RT-qPCR suggested that the replication level of ALV-J in tumors was significantly higher than that in tumor-adjacent tissues. This study suggests that chTERT plays a critical role in the tumorigenicity of ALV-J by enhancing the Wnt/ß-catenin signaling pathway, which will contribute to further elucidating the tumor-inducing mechanism of ALV-J.

The key amino acid sites 199-205, 269, 319, 321 and 324 of ALV-K env contribute to the weaker replication capacity of ALV-K than ALV-A.

BACKGROUND: Avian leukosis virus (ALV) is an infectious retrovirus, that mainly causes various forms of tumours, immunosuppression, a decreased egg production rate and slow weight gain in poultry. ALV consists of 11 subgroups, A-K, among which ALV-K is an emerging subgroup that has become prevalent in the past 10 years. Most ALV-K isolates showed weak replication ability and pathogenicity. In this study, the weak replication ability of ALV-K was explored from the perspective of the interaction between ALV-K gp85 and the Tva receptor. METHODS: Fourteen soluble recombinant ALV-A/K gp85 chimeric proteins were constructed by substituting the sequence difference regions (hr1, hr2 and vr3) of the ALV-A gp85 protein with the skeleton ALV-K gp85 protein for co-IP and competitive blocking tests. RESULTS: The binding capacity of ALV-K gp85 to Tva was significantly weaker than that of ALV-A gp85 (P < 0.05) and the key amino acid sites 199-205, 269, 319, 321 and 324 of ALV-K env contributed to the weaker replication capacity of ALV-K than ALV-A. CONCLUSIONS: This is the first study to reveal the molecular factors of the weak replication ability of ALV-K from the perspective of the interaction of ALV-K gp85 to Tva, providing a basis for further elucidation of the infection mechanism of ALV-K.

The expression level of chicken telomerase reverse transcriptase in tumors induced by ALV-J is positively correlated with methylation and mutation of its promoter region.

Avian leukosis virus subgroup J (ALV-J) can cause neoplastic diseases in poultry and is still widely prevalent in China. Chicken telomerase reverse transcriptase (chTERT) is the core component of telomerase, which is closely related to the occurrence and development of tumors. Our previous studies showed that chTERT is overexpressed in ALV-J tumors, but the mechanism is still not completely clear. Therefore, this study aims to analyze the possible molecular mechanism of chTERT overexpression in ALV-J tumors from the perspective of DNA methylation and promoter mutation. Methylation sequencing of the chTERT amplicon showed that ALV-J replication promoted the methylation level of the chTERT promoter. And the methylation level of the chTERT promoter in ALV-J tumors was significantly higher than that in tumor-adjacent and normal tissues. Compared with the tumor-adjacent and normal tissues, the chTERT promoter in each ALV-J tumors tested had a mutation of -183 bp C > T, and 36.0% (9/25) of the tumors also had mutations of -184 bp T > C, -73 bp::GGCCC and -56 bp A > T in the chTERT promoter, which formed the binding sites for the transcription factors NFAT5, TFAP2A and ZEB1, respectively. The results of RT-qPCR and Western blotting showed that the occurrence of these mutations significantly increased the expression level of chTERT. In conclusion, this study demonstrated that the high expression of chTERT in ALV-J tumors is positively correlated with the level of hypermethylation and mutation in its promoter, which provides a new perspective for further research on the molecular mechanism of chTERT in ALV-J tumorigenesis.

Residues 140-142, 199-200, 222-223, and 262 in the Surface Glycoprotein of Subgroup A Avian Leukosis Virus Are the Key Sites Determining Tva Receptor Binding Affinity and Infectivity.

Subgroup A avian leukosis virus (ALV-A) invades cells through gp85-encoded surface glycoprotein (SU) via specifically recognizing the cellular receptor Tva. To identify the key residues of ALV-A SU that determine the Tva binding affinity and infectivity in DF-1 cells, a strategy of substituting corresponding residues of SU between ALV-A RSA and ALV-E ev-1 (using Tvb as the receptor) was adopted. A series of chimeric soluble gp85 proteins were expressed for co-immunoprecipitation (co-IP) analysis and blocking analysis of viral entry, and various recombinant viruses based on replication-competent avian retrovirus vectors containing Bryan polymerase (RCASBP) were constructed for transfection into DF-1 cells and measurement of the percentage of GFP-positive cells. The results revealed that the substitution of residues V138, W140, Y141, L142, S145, and L154 of host range region 1 (hr1), residues V199, G200, Q202, R222, and R223 of host range region 2 (hr2), and residue G262 of variable region 3 (vr3) reduced the viral infectivity and Tva binding affinity, which was similar to the effects of the -139S, -151N, -155PWVNPF, -201NFD, Δ214-215, and -266S mutations. Our study indicated that hr1 and hr2 contain the principal receptor interaction determinants, with new identified-vr3 also playing a key role in the receptor binding affinity of ALV-A.

Chicken telomerase reverse transcriptase mediates LMH cell pyroptosis by regulating the nuclear factor-kappa B signaling pathway.

The activation of human telomerase reverse transcriptase is regulated by the nuclear factor kappa B (NF-κB) signaling pathway to various degrees to promote the occurrence and development of tumors. However, the regulatory roles of chicken telomerase reverse transcriptase (chTERT) and the NF-κB signaling pathway in chickens are still elusive, particularly in respect to the regulation of cell pyroptosis. In this study, we found that chTERT upregulated the expression of p65 and p50, downregulated the expression of IκBα, promoted the phosphorylation of p65, p50, and IκBα, and significantly increased the transcript levels of the inflammatory cytokines IFNγ, TNFα, and IL-6 in LMH cells. The activity of NF-κB was significantly decreased after siRNA-mediated chTERT silencing. The expression of chTERT and telomerase activity were also significantly decreased when the NF-κB signaling pathway was blocked by p65 siRNA, MG132 or BAY 11-7082. In cells treated with LPS, the activity of NF-κB signaling pathway and the expression of chTERT were significantly upregulated. All of the results suggested that chTERT and the NF-κB pathway could regulate each other, reciprocally. Moreover, the expression of Caspase-1, NLRP3, GSDMA, IL-18, and IL-1ß and caused membrane perforation, suggesting the development of pyroptosis by chTERT in LMH cells. And the expression of caspase-11 did not significantly increased in chTERT overexpression group. Genetic silence of NF-κB p65 or chTERT gene by siRNA suppressed the expression of these proinflammatory cytokines, indicating that chTERT mediates pyroptosis by regulating the NF-κB signaling pathway in LMH cells.

Mutual regulation between chicken telomerase reverse transcriptase and the Wnt/ß-catenin signalling pathway inhibits apoptosis and promotes the replication of ALV-J in LMH cells.

This study aimed to explore the mutual regulation between chicken telomerase reverse transcriptase (chTERT) and the Wnt/ß-catenin signalling pathway and its effects on cell growth and avian leukosis virus subgroup J (ALV-J) replication in LMH cells. First, LMH cells stably overexpressing the chTERT gene (LMH-chTERT cells) and corresponding control cells (LMH-NC cells) were successfully constructed with a lentiviral vector expression system. The results showed that chTERT upregulated the expression of ß-catenin, Cyclin D1, TCF4 and c-Myc. chTERT expression level and telomerase activity were increased when cells were treated with LiCl. When the cells were treated with ICG001 or IWP-2, the activity of the Wnt/ß-catenin signalling pathway was significantly inhibited, and chTERT expression and telomerase activity were also inhibited. However, when the ß-catenin gene was knocked down by small interfering RNA (siRNA), the changes in chTERT expression and telomerase activity were consistent with those in cells treated with ICG001 or IWP-2. These results indicated that chTERT and the Wnt/ß-catenin signalling pathway can be mutually regulated. Subsequently, we found that chTERT not only shortened the cell cycle to promote proliferation but also inhibited apoptosis by downregulating the expression of Caspase 3, Caspase 9 and BAX; upregulating BCL-2 and BCL-X expression; and promoting autophagy. Moreover, chTERT significantly enhanced the migration ability of LMH cells, upregulated the protein and mRNA expression of ALV-J and increased the virus titre. ALV-J replication promoted chTERT expression and telomerase activity.

Discovery and Bioactivity of the Novel Lasso Peptide Microcin Y.

Lasso peptides, a class of ribosomally synthesized and post-translationally modified peptides (RiPPs) secreted by bacteria, have antimicrobial activity. Here, a novel lasso peptide, microcin Y (MccY), was discovered and characterized. The gene cluster for MccY synthesis was cloned for expression in Escherichia coli. This peptide was purified by HPLC and characterized by Q-TOF. MIC assays showed that some Bacillus, Staphylococcus, Pseudomonas, Shigella, and Salmonella strains were sensitive to MccY. Interestingly, Salmonellatyphimurium and Salmonella infantis were efficiently inhibited by MccY, while they were not affected by MccJ25, a lasso peptide that has antibacterial effects on many Salmonella strains. Furthermore, MccY-resistant strains of S. typhimurium were screened, and mutations were found in FhuA and SbmA, indicating the importance of these transporters for MccY absorption. This novel peptide can greatly broaden the antimicrobial spectrum of MccJ25 in Salmonella and is expected to be used in food preservation and animal feed additive areas.

Rapid detection of avian leukosis virus subgroup J by cross-priming amplification.

Avian leukosis virus subgroup J (ALV-J) causes oncogenic disease in chickens in China, resulting in great harm to poultry production, and remains widespread in China. Herein, we employed a cross-priming amplification (CPA) approach and a nucleic acid detection device to establish a visual rapid detection method for ALV-J. The sensitivity of CPA, polymerase chain reaction (PCR) and real-time PCR (RT-PCR) was compared, and the three methods were used to detect ALV-J in the cell cultures which inoculated with clinical plasma. The result showed when the amplification reaction was carried out at 60 °C for just 60 min, the sensitivity of CPA was 10 times higher than conventional PCR, with high specificity, which was comparable with RT-PCR, based on detection of 123 cell cultures which inoculated with clinical plasma, the coincidence rate with real-time PCR was 97.3% (71/73). CPA detection of ALV-J does not require an expensive PCR instrument; a simple water bath or incubator is sufficient for complete DNA amplification, and the closed nucleic acid detection device avoids aerosol pollution, making judgment of results more intuitive and objective. The CPA assay would be a promising simple, rapid and sensitive method for identification of ALV-J.

Molecular characteristics of subgroup J avian leukosis virus isolated from yellow breeder chickens in Guangdong, China, during 2016-2019.

Since 2005, subgroup J avian leukosis virus (ALV-J) infection has been present in yellow chickens in Guangdong, China, causing severe economic losses to the local poultry industry. ALV-J is a rapidly evolving retrovirus. To investigate the molecular characteristics of ALV-J isolates from yellow breeder chickens in Guangdong, 17 virus strains were isolated from 6549 anticoagulants from clinically healthy birds between 2016 and 2019, and completely sequenced and phylogenetically analyzed. Phylogenetic analysis of the gp85 gene showed that all isolated viruses were divided into three different branches. Notably, 41.2% (7/17) of the isolates shared a novel G2598A nucleotide mutation in the pol gene and caused the stop codon to be advanced by 8 positions. Nearly 200 nucleotides were deleted from the redundant TM (rTM) region in all strains, but all retained an intact direct repeat (DR1). 82.4% (14/17) of isolates contained a complete E element. Additionally, 29.4% (5/17) of isolates detected an 11 bp deletion in U3 region, and the AIB REP1 transcription factor is missing. The study indicated that ALV-J infection had still been prevalent in the yellow breeder chicken farms in Guangdong, and the genetic background of the strains is diverse. This study provides the latest data on the molecular characteristics of ALV-J, which will help to reveal the evolution trend of ALV-J and develop relevant prevention and control measures.

Single Amino Acids G196 and R198 in hr1 of Subgroup K Avian Leukosis Virus Glycoprotein Are Critical for Tva Receptor Binding.

Avian leukosis viruses (ALVs), a type of retrovirus responsible for various tumor diseases in chickens, are divided into 11 subgroups: ALV-A to ALV-K. After the envelope glycoproteins of ALV interact with the cellular receptor to initiate viral invasion, alterations in a few amino acids of the viral glycoproteins or cell receptors may trigger changes in their conformation and binding affinity. To identify the functional determinants of the ALV-K envelope protein that binds to Tva (a recently identified cellular receptor of ALV-K), using the strategy of continuous, segment-by-segment substitution of the gp85-encoded surface glycoprotein (SU) of ALV-K GDFX0602 with ALV-E ev-1 (using Tvb as the receptor), a series of chimeric soluble gp85 proteins were expressed for co-immunoprecipitation (co-IP) analysis and a series of recombinant viruses with replication-competent avian retrovirus vectors containing Bryan polymerase (RCASBP) as their skeleton were created for transfecting to DF-1 cells and titer determination. The co-IP analysis, fluorescence-activated cell sorting, and virus titer measurements revealed that the substitution of residues 194-198, 206-216 of hr1, residues 251-256 between hr1 and hr2, and residues 269-280 of hr2 were identified to reduce the binding of gp85 to Tva. The substitution of residues 194-221 in hr1 nullified the infectiveness of these viruses, similar to the effect of single amino acid mutations in K251E and L252I located between hr1 and hr2; continuous amino acid mutations in hr2 could not produce the same effect despite reducing their infectiveness. Finally, single amino acid mutations G196A and R198H nearly abolished the binding of gp85 to Tva and nullified the infectiveness of these viruses to DF-1. This study paves the way for exploring the molecular mechanisms of the binding of Tva to ALV-K SU.

A cell line resistant to avian leukosis virus subgroup B infection.

The expression of env proteins that bind to viral cell receptors on avian leukosis virus (ALV)-susceptible cells can block ALV infection. In this study, we constructed a cell line (DF-1/B) by expressing the ALV-B env protein in DF-1 cells. PCR, immune fluorescence assay, Western blot, and immune electron microscopy results showed that the env gene can be stably expressed in DF-1cells and the env protein could be detected on the DF-1 cell membrane. An antiviral experiment concluded that the DF-1/B cell line could be resistant to 1 × 104 TCID50 ALV-B virus infection, but had no inhibitory effect on other subgroup ALV. This means that the DF-1/B cell line is specifically resistant to ALV-B and can be used as a tool for ALV-B diagnosis.

Development and application of a SYBR green real-time PCR for detection of the emerging avian leukosis virus subgroup K.

Avian leukosis virus subgroup K (ALV-K) is an emerging ALV tumor virus of chickens. We developed a SYBR green-based real-time polymerase chain reaction (PCR) assay for the rapid and economical detection of ALV-K in chicken flocks. The assay was specific for ALV-K and did not cross-react with other ALV subgroup or avian influenza virus, Newcastle disease virus, or Marek's Disease virus. The method was 100 times more sensitive than conventional PCR and 10 times more sensitive than the enzyme-linked immunosorbent assay (ELISA) for the P27 antigen. The assay was also more sensitive than conventional PCR in tests of 86 clinical plasma samples. DF-1 tissue culture cells infected with 1 TCID50 ALV-K particle were identified as negative using ELISA but tested positive with the real-time PCR method. The viral loads in organs and tissues in infected chickens were highest in kidney, lungs, and glandular stomach, and these results matched ELISA findings.

Phylogenetic Analysis and Pathogenicity Assessment of the Emerging Recombinant Subgroup K of Avian Leukosis Virus in South China.

In recent years, cases of avian leukosis virus (ALV) infection have become more frequent in China. We isolated 6 ALV strains from yellow feather broiler breeders in south China from 2014 to 2016. Their full genomes were sequenced, compared, and analyzed with other reference strains of ALV. The complete genomic nucleotide sequences of GD150509, GD160403, GD160607, GDFX0601, and GDFX0602 were 7482 bp in length, whereas GDFX0603 was 7480 bp. They shared 99.7% to 99.8% identity with each other. Homology analysis showed that the gag, pol, long terminal repeats (LTRs), and the transmembrane region (gp37) of the env genes of the 6 viruses were well conserved to endogenous counterpart sequences (>97.8%). However, the gp85 genes displayed high variability with any known chicken ALV strains. Growth kinetics of DF-1 cells infected with the isolated ALV showed viral titers that were lower than those infected with the GD13 (ALV-A), CD08 (ALV-B), and CHN06 (ALV-J) on day 7 post-infection. The infected Specific-pathogen-free (SPF) chickens could produce continuous viremia, atrophy of immune organs, growth retardation and no tumors were observed. These subgroup ALVs are unique and may be common in south China. The results suggested that updating the control and eradication program of exogenous ALV for yellow feather broiler breeders in south China needs to be considered because of the emergence of the new subgroup viruses.

Ubiquitination of non-lysine residues in the retroviral integrase.

Retroviral integrase catalyzes the integration of retroviral genome into host chromosomal DNA, which is a prerequisite of effective viral replication and infection. The human immunodeficiency virus type 1 (HIV-1) integrase has previously been reported to be regulated by the ubiquitination, but the molecular characterization of integrase ubiquitination is still unclear. In this study, we analyzed the ubiquitination of avian leukosis virus (ALV) integrase in detail. The ubiquitination assay showed that, like HIV-1, ALV integrase could also be modified by ubiquitination when expressed in 293 T and DF-1 cells. Domain mapping analysis revealed that the ubiquitination of ALV integrase might mainly occurred in the catalytic core and the N-terminal zinc-binding domains. Both lysine and non-lysine residues within integrase of ALV and HIV-1 were responsible for the ubiquitin conjugation, and the N-terminal HHCC zinc-binding motif might play an important role in mediating integrase ubiquitination. Interestingly, mass spectrometry analysis identified the Thr10 and Cys37 residues in the HHCC zinc-binding motif as the ubiquitination sites, indicating that ubiquitin may be conjugated to ALV integrase through direct interaction with the non-lysine residues. These findings revealed the detailed features of retroviral integrase ubiquitination and found a novel mechanism of ubiquitination mediated by the non-lysine residues within the N-terminal zinc-binding domain of integrase.

ALV-J strain SCAU-HN06 induces innate immune responses in chicken primary monocyte-derived macrophages.

Avian leucosis virus subgroup J (ALV-J) can cause lifelong infection and can escape from the host immune defenses in chickens. Since macrophages act as the important defense line against invading pathogens in host innate immunity, we investigated the function and innate immune responses of chicken primary monocyte-derived macrophages (MDM) after ALV-J infection in this study. Our results indicated that ALV-J was stably maintained in MDM cells but that the viral growth rate was significantly lower than that in DF-1 cells. We also found that ALV-J infection significantly increased nitric oxide (NO) production, but had no effect on MDM phagocytic capacity. Interestingly, infection with ALV-J rapidly promoted the expression levels of Myxovirus resistance 1 (Mx) (3 h, 6 h), ISG12 (6 h), and interleukin-1ß (IL-1ß) (3 h, 12 h) at an early infection stage, whereas it sharply decreased the expression of Mx (24 h, 36 h), ISG12 (36 h), and made little change on IL-1ß (24 h, 36 h) production at a late infection stage in MDM cells. Moreover, the protein levels of interferon-ß (IFN-ß) and interleukin-6 (IL-6) had sharply increased in infected MDM cells from 3 to 36 h post infection (hpi) of ALV-J. And, the protein level of interleukin-10 (IL-10) was dramatically decreased at 36 hpi in MDM cells infected with ALV-J. These results demonstrate that ALV-J can induce host innate immune responses and we hypothesize that macrophages play an important role in host innate immune attack and ALV-J immune escape.