Avian Leucosis Virus-Host Interaction: The Involvement of Host Factors in Viral Replication

Establishment and application of a gold nanoparticle-based immunochromatographic test strip for the detection of avian leukosis virus P27 antigen in egg white samples

Avian leukemia is an infectious tumorous disease of chickens caused by subgroup A of the avian leukemia virus (ALV-A), which mainly causes long-term viremia, slow growth, immune suppression, decreased production performance, multi-tissue tumors, and even death. The infection rate of this disease is very high in chicken herds in China, causing huge economic losses to the poultry industry every year. We successfully expressed the specific antigen protein of ALV (P27) through recombinant protein technology and screened a pair of highly sensitive monoclonal antibodies (mAbs) through mouse immunity, cell fusion, and antibody pairing. Based on this pair of antibodies, we established a dual antibody sandwich ELISA and gold nanoparticle immunochromatographic strip (AuNP-ICS) detection method. In addition, the parameters of the dual antibody sandwich ELISA and AuNP-ICS were optimized under different reaction conditions, which resulted in the minimum detection limits of 0.2 ng mL-1 and 1.53 ng ml-1, respectively. Commonly available ELISA and AuNP-ICS products on the market were compared, and we found that our established immune rapid chromatography had higher sensitivity. This established AuNP-ICS had no cross-reactivity with Influenza A (H1N1), Influenza A (H9N2), respiratory syncytial virus (RSV), varicella-zoster virus (VZV), Listeria monocytogenes listeriolysin (LLO), and Staphylococcal enterotoxin SED or SEC. Finally, the established AuNP-ICS was used to analyze 35 egg samples, and the results showed 5 positive samples and 30 negative samples. The AuNP-ICS rapid detection method established by our group had good specificity, high sensitivity, and convenience, and could be applied to the clinical sample detection of ALV-A.

Rapid and sensitive visual detection of avian leukosis virus by reverse transcription loop-mediated isothermal amplification combined with a lateral flow immunochromatographic strip assay

Considering that avian leukosis virus (ALV) infection has inflicted massive economic losses on the poultry breeding industry in most countries, its early diagnosis remains an important measure for timely treatment and control of the disease, for which a rapid and sensitive point-of-care test is required. We established a user-friendly, economical, and rapid visualization method for ALV amplification products based on reverse transcription loop-mediated isothermal amplification (RT-LAMP) combined with an immunochromatographic strip in a lateral flow device (LFD). Using the ALVp27 gene as the target, five RT-LAMP primers and one fluorescein-isothiocyanate-labeled probe were designed. After 60 min of RT-LAMP amplification at 64 °C, the products could be visualized directly using the LFD. The detection limit of this assay for ALV detection was 102 RNA copies/μL, and the sensitivity was 100 times that of reverse transcription polymerase chain reaction (RT-PCR), showing high specificity and sensitivity. To verify the clinical practicality of this assay for detecting ALV, the gold standard RT-PCR method was used for comparison, and consistent results were obtained with both assays. Thus, the assay described here can be used for rapid detection of ALV in resource-limited environments.

The coinfection of ALVs causes severe pathogenicity in Three-Yellow chickens

The coinfection of ALVs (ALV-J plus ALV-A or/and ALV-B) has played an important role in the incidence of tumors recently found in China in local breeds of yellow chickens. The study aims to obtain a better knowledge of the function and relevance of ALV coinfection in the clinical disease of avian leukosis, as well as its unique effect on the pathogenicity in Three-yellow chickens. One-day-old Three-yellow chicks (one day old) were infected with ALV-A, ALV-B, and ALV-J mono-infections, as well as ALV-A + J, ALV-B + J, and ALV-A + B + J coinfections, via intraperitoneal injection, and the chicks were then grown in isolators until they were 15 weeks old. The parameters, including the suppression of body weight gain, immune organ weight, viremia, histopathological changes and tumor incidence, were observed and compared with those of the uninfected control birds. The results demonstrated that coinfection with ALVs could induce more serious suppression of body weight gain (P < 0.05), damage to immune organs (P < 0.05) and higher tumor incidences than monoinfection, with triple infection producing the highest pathogenicity. The emergence of visible tumors and viremia occurred faster in the coinfected birds than in the monoinfected birds. These findings demonstrated that ALV coinfection resulted in considerably severe pathogenic and immunosuppressive consequences.

Critical role for ribonucleoside-diphosphate reductase subunit M2 in ALV-J-induced activation of Wnt/β-catenin signaling via interaction with P27

Avian leukemia virus subgroup J (ALV-J) causes various diseases associated with tumor formation and decreased fertility and induced immunosuppressive disease, resulting in significant economic losses in the poultry industry globally. Virus usually exploits the host cellular machinery for their replication. Although there are increasing evidences for the cellular proteins involving viral replication, the interaction between ALV-J and host proteins leading to the pivotal steps of viral life cycle are still unclear. Here, we reported that ribonucleoside-diphosphate reductase subunit M2 (RRM2) plays a critical role during ALV-J infection by interacting with capsid protein P27 and activating Wnt/β-catenin signaling. We found that the expression of RRM2 is effectively increased during ALV-J infection, and that RRM2 facilitates ALV-J replication by interacting with viral capsid protein P27. Furthermore, ALV-J P27 activated Wnt/β-catenin signaling by promoting β-catenin entry into the nucleus, and RRM2 activated Wnt/β-catenin signaling by enhancing its phosphorylation at Ser18 during ALV-J infection. These data suggest that the upregulation of RRM2 expression by ALV-J infection favors viral replication in host cells via activating Wnt/β-catenin signaling. IMPORTANCE Our results revealed a novel mechanism by which RRM2 facilitates ALV-J growth. That is, the upregulation of RRM2 expression by ALV-J infection favors viral replication by interacting with capsid protein P27 and activating Wnt/β-catenin pathway in host cells. Furthermore, the phosphorylation of serine at position 18 of RRM2 was verified to be the important factor regulating the activation of Wnt/β-catenin signaling. This study provides insights for further studies of the molecular mechanism of ALV-J infection.

Avian Leukosis: Will We Be Able to Get Rid of It?

Avian leukosis viruses (ALVs) have been virtually eradicated from commercial poultry. However, some niches remain as pockets from which this group of viruses may reemerge and induce economic losses. Such is the case of fancy, hobby, backyard chickens and indigenous or native breeds, which are not as strictly inspected as commercial poultry and which have been found to harbor ALVs. In addition, the genome of both poultry and of several gamebird species contain endogenous retroviral sequences. Circumstances that support keeping up surveillance include the detection of several ALV natural recombinants between exogenous and endogenous ALV-related sequences which, combined with the well-known ability of retroviruses to mutate, facilitate the emergence of escape mutants. The subgroup most prevalent nowadays, ALV-J, has emerged as a multi-recombinant which uses a different receptor from the previously known subgroups, greatly increasing its cell tropism and pathogenicity and making it more transmissible. In this review we describe the ALVs, their different subgroups and which receptor they use to infect the cell, their routes of transmission and their presence in different bird collectivities, and the immune response against them. We analyze the different systems to control them, from vaccination to the progress made editing the bird genome to generate mutated ALV receptors or selecting certain haplotypes.

Identification of the Interaction between Minichromosome Maintenance Proteins and the Core Protein of Hepatitis B Virus

Chronic HBV infection is a major cause of cirrhosis and hepatocellular carcinoma. Finding host factors involved in the viral life cycle and elucidating their mechanisms is essential for developing innovative strategies for treating HBV. The HBV core protein has pleiotropic roles in HBV replication; thus, finding the interactions between the core protein and host factors is important in clarifying the mechanism of viral infection and proliferation. Recent studies have revealed that core proteins are involved in cccDNA formation, transcriptional regulation, and RNA metabolism, in addition to their primary functions of capsid formation and pgRNA packaging. Here, we report the interaction of the core protein with MCMs, which have an essential role in host DNA replication. The knockdown of MCM2 led to increased viral replication during infection, suggesting that MCM2 serves as a restriction factor for HBV proliferation. This study opens the possibility of elucidating the relationship between core proteins and host factors and their function in viral proliferation.