Dynamic distribution and tissue tropism of infectious laryngotracheitis virus in experimentally infected chickens.

Infectious laryngotracheitis (ILT), caused by infectious laryngotracheitis virus (ILTV), is an Office International des Epizooties (OIE) notifiable disease. However, we have not clearly understood the dynamic distribution, tissue tropism, pathogenesis, and replication of ILTV in chickens. In this report, we investigated the dynamic distribution and tissue tropism of the virus in internal organs of experimentally infected chickens using quantitative real-time polymerase chain reaction (qPCR) and a histopathological test. The study showed that ILTV could be clearly detected in eight internal organs (throat, trachea, lung, cecum, kidney, pancreas, thymus and esophagus) of infected chickens, whereas the virus was difficult to detect in heart, spleen, proventriculus, liver, brain and bursa. Meanwhile, the thymidine kinase (TK) gene levels in eight internal organs increased from 3 days to 5 days postinfection, and then decreased from 6 days to 8 days postinfection. The log copy number of ILTV progressively increased over 3 days, which corresponds to the clinical score and the result of the histopathological test. The results provide a foundation for further clarification of the pathogenic mechanism of ILTV in internal organs and indicate that throat, lung, trachea, cecum, kidney, pancreas and esophagus may be preferred sites of acute infection, suggesting that the tissue tropism and distribution of ILTV is very broad.

Molecular characterization and phylogenetic analysis of infectious bursal disease viruses isolated from chicken in South China in 2011.

Infectious bursal disease virus (IBDV) is a double-stranded RNA virus that causes immunosuppressive disease in young chickens. Thousands of cases of IBDV infection are reported each year in South China, and these infections can result in considerable economic losses to the poultry industry. To monitor variations of the virus during the outbreaks, 30 IBDVs were identified from vaccinated chicken flocks from nine provinces in South China in 2011. VP2 fragments from different virus strains were sequenced and analyzed by comparison with the published sequences of IBDV strains from China and around the world. Phylogenetic analysis of hypervariable regions of the VP2 (vVP2) gene showed that 29 of the isolates were very virulent (vv) IBDVs, and were closely related to vvIBDV strains from Europe and Asia. Alignment analysis of the deduced amino acid (aa) sequences of vVP2 showed the 29 vv isolates had high uniformity, indicated low variability and slow evolution of the virus. The non-vvIBDV isolate JX2-11 was associated with higher than expected mortality, and had high deduced aa sequence similarity (99.2 %) with the attenuated vaccine strain B87 (BJ). The present study has demonstrated the continued circulation of IBDV strains in South China, and emphasizes the importance of reinforcing IBDV surveillance.

[Research progress and prospect of universal influenza vaccine].

The constant outbreaks of influenza in a global scale have aroused great concern all over the world. Vaccine has been the most effective and economic means against influenza. However, the broad tropism and high mutation of influenza viruses have limited the effectiveness of influenza vaccines. Current influenza virus vaccines provide effective protection against virus strains that are identical or highly similar to the vaccine strain. Once a highly mutated or new strain of influenza virus appears, the current vaccine would lose its effectiveness. Therefore, the development of a universal vaccine against highly mutated or new influenza virus subtypes has become a hot spot in the field of influenza vaccine research. The major methods of developing the universal influenza vaccine are to select a conserved protein of influenza virus as an antigen. At least three universal influenza vaccines have been tested in clinical trials. Moreover, changing the routes of vaccine immunization and immunization schemes could also improve the effect of heterosubtypic immunity. This review summarized the research progresses of universal influenza vaccines and provided our prospective on universal influenza vaccine research.

Rapid diagnosis of duck plagues virus infection by loop-mediated isothermal amplification.

Duck virus enteritis is a serious disease among farmed and free-living ducks (Anatidae) and a constant threat to the commercial duck industry in China. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed to rapidly detect and diagnose duck plague virus (DPV) in both farmed and wild waterfowl, and compared with polymerase chain reaction (PCR) method and real-time PCR method in accuracy, sensitivity and specificity. A set of four specific primers was successfully designed to recognize six distinct genomic sequences of UL6 protein from DPV, including one forward inner primer, one back inner primer and two outer primers. The optimum reaction temperature and time were verified to be 61.5 degrees C and 60 min, respectively. Comparative experiments showed that LAMP assay was a simple, rapid, accurate, sensitive and specific method for detecting DPV, and was superior to PCR assay in sensitivity and specificity for DNA amplification. In addition, challenge tests indicated the newly developed LAMP method was more sensitive for the diagnosis of DPV infection than virus isolation and PCR. LAMP assay would be a good alternative method for on-farm disease diagnosis.

Rapid detection of porcine reproductive and respiratory syndrome virus by reverse transcription loop-mediated isothermal amplification assay.

A rapid detection assay based on reverse transcription loop-mediated isothermal amplification (RT-LAMP) has been developed for detecting porcine reproductive and respiratory syndrome virus (PRRSV). The RT-LAMP assay utilized a set of six primers to amplify the open reading frame 6 (ORF6) of the PRRSV. The amplified products were analyzed by agarose gel electrophoresis or visualized by colorimetric method. The results demonstrated that the RT-LAMP assay detected all 22 different PRRSV isolates, had no cross-reaction with four other swine viruses (i.e., PCV2, SIV, CSFV, and PEDV), and obtained a 91.3% sensitivity in 23 positive clinical samples in reference to the permissive cells-based virus isolation procedure. Therefore, the RT-LAMP assay provides a specific and sensitive means for detecting PRRSV in a simple, fast, and cost-effective manner. Furthermore, the RT-LAMP assay can be performed in less well-equipped laboratories as well as fields.