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At least 451 records · Page 25Linked to original sources
PubMed2024

One-pot Golden Gate Assembly of an avian infectious bronchitis virus reverse genetics system.

Avian infectious bronchitis is an acute respiratory disease of poultry of particular concern for global food security. Investigation of infectious bronchitis virus (IBV), the causative agent of avian infectious bronchitis, via reverse genetics enables deeper understanding of virus biology and a rapid response to emerging variants. Classic methods of reverse genetics for IBV can be time consuming, rely on recombination for the introduction of mutations, and, depending on the system, can be subject to genome instability and unreliable success rates. In this study, we have applied data-optimized Golden Gate Assembly design to create a rapidly executable, flexible, and faithful reverse genetics system for IBV. The IBV genome was divided into 12 fragments at high-fidelity fusion site breakpoints. All fragments were synthetically produced and propagated in E. coli plasmids, amenable to standard molecular biology techniques for DNA manipulation. The assembly can be carried out in a single reaction, with the products used directly in subsequent viral rescue steps. We demonstrate the use of this system for generation of point mutants and gene replacements. This Golden Gate Assembly-based reverse genetics system will enable rapid response to emerging variants of IBV, particularly important to vaccine development for controlling spread within poultry populations.

Infectious bronchitis virus↗
PubMed1982

Delayed neurotoxicity resulting from administration of leptophos to the comb of domestic fowl.

We investigated the occurrence of delayed neurotoxicity in domestic fowl following percutaneous application of leptophos. Five groups of 5 adult hens received daily percutaneous doses of 1.0 ml/hen of leptophos emulsion (leptophos; 340 mg/hen/day) for 2, 5, 10, 15 or 20 days. There was no abnormal gait in the 2-day group. Two out of 5 hens in the 5-day group showed mild ataxia from about 2 weeks after the final administration, but did not develop severe neuropathy. On the contrary, 4 out of 5 birds in the 10-day group and all hens in the 15- and 20-day groups were affected by various stages of neurotoxicity. Some of them died from neurotoxicity. Ten of young male chickens were given the same dermal dose for 5 or 10 days. Although no abnormal chicken was observed in the 5-day group, all chickens in the 10-day group showed severe paralysis and two of them died. We studied the incidence rates of delayed neurotoxicity resulting from respective applications of the emulsion and the acetone solution of leptophos. No significant difference was observed between them. These results suggest that the daily dermal application of the relatively high dose of leptophos, even if for the short term, can cause the same delayed neurotoxic effects as by the oral administration in hens or chickens.

Animals↗
PubMedDate not supplied

Effects of an S6 strain of Mycoplasma gallisepticum challenge before beginning of lay on various egg characteristics in commercial layers.

Mycoplasma gallisepticum (MG) is a reproductive/respiratory disease in poultry implicated in suboptimum egg production and decreased hatchability. Commercial layer hens raised in a controlled environment were inoculated with the S6 strain of MG at 10 wk of age. Egg production and selected egg and egg quality parameters were quantitated over the entire lay cycle for inoculated and control birds. The S6 inoculation had no effect on bird weight, egg production, associated egg quality parameters, or histopathologic lesion scores. This study shows that in the absence of environmental stressors a prelay S6 MG inoculation does not produce detrimental effects on layer hen performance.

Animals↗
PubMedDate not supplied

Comparison of a putative second serotype of chicken infectious anemia virus with a prototypical isolate I. Pathogenesis.

CIAV-7 is a virus with similar pathogenic and physicochemical characteristics to, but antigenically distinct from, chicken infectious anemia virus (CIAV). The pathogenesis of CIAV-7 was evaluated in a comparative study with a representative isolate of CIAV, the Del-Ros strain. The pathogenesis of CIAV-7 was similar to Del-Ros on the basis of the clinical disease induced and gross and microscopic lesions, although CIAV-7 produced fewer and less severe lesions overall. A second comparative pathogenesis study was performed with Del-Ros and CIAV-7, both alone and in combination with infectious bursal disease virus (IBDV). In this study, the pathogenesis of CIAV-7 was similar to Del-Ros in clinical, gross, and microscopic lesions in the bone marrow. However, thymic lesions were less severe in CIAV-7-inoculated birds. The interaction between Del-Ros and IBDV was synergistic, whereas there was no observed potentiation of CIAV-7-induced disease by IBDV. Progeny from breeder flocks from several geographic locations in the eastern United States were challenged with CIAV-7 or Del-Ros to assess protection by maternal antibodies. Some progeny from all flocks had protection against CIAV-7 challenge, providing evidence for the presence of CIAV-7 in the field. Additionally, the number of birds protected against CIAV-7 or Del-Ros challenge varied within flocks, demonstrating that the agents are serologically distinct.

Animals↗
PubMed2005

A Marek's disease virus vIL-8 deletion mutant has attenuated virulence and confers protection against challenge with a very virulent plus strain.

Marek's disease virus (MDV) is an alpha-herpesvirus that causes rapid development of T-cell lymphomas in chickens. MDV-encoded vIL-8 is homologous to the cellular IL-8 gene, and its function in MDV pathogenesis has yet to be determined. Using overlapping cosmid clone-based technology, we have generated an MDV vIL-8 deletion mutant virus, rMd5/delta vIL-8. In vivo experiments with this mutant virus demonstrated that deletion of vIL-8 results in attenuation of the virus and induction of significantly less gross tumor, both in viscera and nerves, when compared to the parental virus. Reintroduction of the vIL-8 gene in the genome of the mutant virus restored the virulence of the virus to the wild-type levels, indicating that vIL-8 plays a role in MDV-induced pathogenesis. In this study, we show that there is a significant difference in the reduction of B cells and activation of T cells in the spleen cells of chickens inoculated with parental rMd5 and vIL-8 deletion mutant virus. These results indicate that vIL-8 is involved in the early phase of pathogenesis, presumably by attracting target cells to the initial site of infection. In addition, protection studies with the vIL-8 mutant virus showed that this mildly virulent virus protects susceptible maternal antibody-positive viruses at a higher level than the commonly used serotype 1 CVI988 vaccine. These results confirm the potential of partially attenuated viruses as vaccines against very virulent plus strains and the usefulness of recombinant DNA technology to generate the next generation of MDV vaccines.

Animals↗
PubMed2006

Relationship between Marek's disease and the time course of viral genome proliferation in feather tips.

A total of 114 male chickens from three sire families of a commercial cross of White Leghorn chickens were infected with RB-1B Marek's disease (MD) virus at 21 days of age by exposing them to chickens previously inoculated with MD virus. The presence of virus in feather tips, feather pulp, and MD viral antibodies indicated all chickens became infected. The first virus-positive chickens were observed at 12 days postexposure (dpe). The frequency reached a maximum at 27 dpe and then decreased. At 80 dpe, when the experiment was terminated, no viral DNA was detected in the feather pulp of the surviving chickens (82%). Death from MD was first observed at 38 dpe and reached 18% by the end of the experiment, with spleen lesions being the major MD lesion. The viral genome titers in spleen extracts of chickens with MD lesions was negatively correlated with the time of death, and, similar to feather pulp, none of the surviving chickens was virus positive at the end of the experiment. Quantization of the viral genome titers in feather tip extracts at 27 and 38 dpe revealed a positive correlation with the presence of MD lesions, but only in the declining phase (38 dpe) and not at the peak (27 dpe) of the viral titer. Sire effects were significant, indicating the presence of genetic factors that affect viral proliferation. Again, significance was only observed at 38 dpe and not at 27 dpe. The results indicate that, in this commercial line, 1) all chickens were susceptible to infection via contact exposure, 2) all surviving chickens recovered from the viral infection, and 3) it is not sufficient to measure viral titers at a single time point when using viral titers as an endpoint for MD susceptibility.

Animals↗
PubMed2006

Experimental infection with avian leukosis virus isolated from Marek's disease vaccines.

Recently, avian leukosis virus (ALV) was isolated from four lots of Marek's disease vaccine produced by two laboratories. The ALVs isolated were characterized by examination of their interactions with cells of two phenotypes (C/E and C/A,E), subgroup-specific polymerase chain reaction (PCR), virus neutralization, envelope gene sequencing, and phylogenetic analysis. All four ALVs are exogenous, belong to subgroup A, and appear to be virtually identical to each other based on PCR and envelope gene nucleotide sequences. We describe herein the characterization of the contaminant viruses in vivo by means of experimental infection in chickens. The contaminant viruses established transient viremia in specified pathogen-free (SPF) Leghorn chickens and elicited a robust and lasting antibody response detectable by enzyme-linked immunosorbent assay. None of the contaminant ALVs induced tumors up to 31 wk of age, and mortality was insignificant. Despite a strong antibody response against the contaminant ALVs, vertical (congenital) transmission to the progeny of experimentally infected SPF chickens took place, albeit at a very low rate (< or = 1.6%). Experimental infection in meat-type chicken embryos resulted in viremia at hatch, suggesting that some meat-type chickens are susceptible to infection and support virus replication.

Animals↗
PubMed1998

Verification of immunosuppression in chicks caused by Cryptosporidium baileyi infection using Brucella abortus strain 1119-3.

Humoral immune response of young chicks to Brucella abortus strain 1119-3 inoculation was monitored to verify the degree of immunosuppression caused by infection with Cryptosporidium baileyi. Young chicks (2-day-old) were orally inoculated each with 2 x 10(6) oocysts of C. baileyi, and then injected intramuscularly with 0.3 ml B. abortus strain 1119-3 containing 1 x 10(9) living organisms on day 14 postinoculation (PI). Serum samples were tested by plate agglutination test on day 17 PI onwards at an interval of 3-6 days over a period of 36 days. Infected chicks with the coccidium showed significantly lower antibody titers than those of uninfected controls (P < 0.05). These findings document that C. baileyi infection in early life stage may predispose chicks easily to other potential poultry diseases.

Animals↗