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Pathogenesis of Newcastle disease in commercial and specific pathogen-free turkeys experimentally infected with isolates of different virulence.

The pathogenesis of five different Newcastle disease virus (NDV) isolates representing all pathotypes was examined in commercial and specific pathogen-free (SPF) turkeys. Experimentally-infected birds were monitored clinically and euthanatized, with subsequent tissue collection, for examination by histopathology, by immunohistochemistry for the presence of NDV nucleoprotein, and by in situ hybridization for the presence of replicating virus. Clinically, the lentogenic pathotype did not cause overt clinical signs in either commercial or SPF turkeys. Mesogenic viruses caused depression in some birds. Turkeys infected with velogenic neurotropic and velogenic viscerotropic isolates showed severe depression, and neurologic signs. Histologic appearances for all strains had many similarities to lesions observed in chickens inoculated with the various isolates; that is, lesions were present predominantly in lymphoid, intestinal, and central nervous tissues. However, in general, disease among turkeys was less severe than in chickens, and turkeys could be considered a subclinical carrier for some of the isolates.

Animals↗

Molecular characterization of Newcastle disease viruses isolated from recent outbreaks in Taiwan.

A reverse transcription-polymerase chain reaction (RT-PCR) was described which amplified a portion of the F and HN genes of Newcastle disease virus (NDV) isolated from recent outbreaks in Taiwan. The F protein plays an important role in determining the virulence of NDV strains. Sequencing of a region specifying the F protein cleavage site was therefore undertaken and this verified the correlation between deduced amino sequences and pathogenicity. Analysis of the deduced amino acid sequences of the F protein cleavage site showed that all recent Taiwanese isolates in 1999 were velogenic viruses. All the virulent viruses have the amino acid sequence 112RRQKR116 for the C-terminus of the F2 protein and phenylanine (F) at the N-terminus of the F1 protein, residue 117. A phylogenetic tree based on the nucleotide sequences of the F gene revealed that recent Taiwanese NDV isolates responsible for recent outbreaks were classified into two distant genotypes (VI and VII). Genotype VI virus is the first finding in Taiwan and has a highly genetic similarity to European isolates, suggesting that they might have originated from a common ancestor.

Amino Acid Sequence↗

Cell-free coupling of Newcastle disease virus RNA transcription, translation and Co-translational processing.

A cell-free coupled system for transcription, translation and glycoprotein processing of the Newcastle disease virus genome is described. The system consists of a rabbit reticulocyte lysate preincubated with micrococcal nuclease and of detergent-disrupted purified Newcastle disease virions. [35S]methionine incorporation was linear for 2 h. Polypeptides NP and M, the presumably unglycosylated analogues of glycoproteins HN and possibly F, were identified as translation products. When in vitro synthesis was carried out in the presence of dog pancreas microsomes the HN analogue (pre-HN) was converted to an 80K (approx.) protein which comigrated on polyacrylamide gels with HN synthesized in vivo and which, except for a small fragment, was protected from proteolytic degradation. In immunoprecipitation studies, antiserum against HN purified from virions reacted with both the processed and the unprocessed form of HN synthesized in vitro.

Animals↗

The effect of protein malnutrition on the susceptibility of the chicken nose to Newcastle disease virus.

The effect of protein malnutrition on the susceptibility of the chicken nose to Newcastle disease virus (NDV) was studied. Chicks that were rendered acutely protein-deficient for 1 or 3 weeks from the time of hatching yielded approximately 10 times more NDV from their throats than did normally fed animals 7 days after inoculation with the virus. Serum antibody responses in the protein-deficient animals 14 days after inoculation of NDV was statistically lower than in the normally fed animals. These results were supported by the mucociliary transport time in the turbinate and sinus, as well as by the histological changes in the turbinate. This difference may thus be due to the fact that normally fed maturing chicks develop an increased resistance to virus which is depressed in protein-deficient animals.

Animals↗

[Development of an enzyme immunoassay for the detection of antibodies from hens and mice against Newcastle disease virus].

The development of an enzyme-immuno-assay (EIA) for detection of avian and mouse antibodies against the Newcastle-Disease Virus is shown. The antigen preparation was the centre of the experiments. The basic assay programme and selected test steps were optimized. The established assay is part of the EIA-control system for a SPF (specific-pathogen-free)-flock and also the essential screening method for the production of anti-NDV-monoclonal antibodies.

Animals↗

A serological survey for avian infectious bronchitis virus and Newcastle disease virus antibodies in backyard (free-range) village chickens in Mexico.

The commercial flocks in Yucatan, Mexico are free of Newcastle disease virus (NDV) in its velogenic viscerotropic form, but little is known about the disease status of backyard poultry. A seroprevalence survey in 30 villages using haemagglutination inhibition (HI) tests for infectious bronchitis virus (IBV) and NDV antibodies was carried out from December 1997 to June 1998. The seroprevalences were 56.5% (95% CI 50-63%) for IBV and 2.2% (95% CI 0.5-3.8%) for NDV. All the villages had chickens that were positive for antibodies to IBV and nine of the villages had chickens that were positive for antibodies to NDV. This suggests that IBV may be responsible for a large proportion of the respiratory disease observed in backyard chickens in Yucatan. The implications of these findings are discussed, including the highly susceptible status of the backyard chickens in Yucatan to NDV and the possibility of this virus being one cause of the syndrome known as mortandad by the local people.

Animals↗

Identification of the P proteins and other disulfide-linked and phosphorylated proteins of Newcastle disease virus.

A unique abundant protein, designated P by analogy to the putative polymerase proteins of other paramyxoviruses, was identified in purified Newcastle disease virus. Under nonreducing conditions the P proteins could be separated from other viral proteins on sodium dodecyl sulfate-polyacrylamide gels. The P proteins were isolated from detergent-solubilized virions as 53,000- to 55,000-dalton monomers and disulfide-linked trimers. Distinct forms of P having four different isoelectric points and two different electrophoretic mobilities were resolved by two-dimensional electrophoresis. Two forms of P were phosphorylated, as were the nucleocapsid protein and non-glycosylated membrane protein. In addition to disulfide-linked forms of P, dimers of the hemagglutinin-neuraminidase glycoprotein and two disulfide-linked versions of the fusion glycoprotein were identified. Several electrophoretic variants of the nucleocapsid protein that were probably created by intrachain disulfide bonding were also isolated from virions under nonreducing conditions. The locations of the newly identified proteins were determined by detergent-salt fractionation of virions and by surface-selective radioiodination of the viral envelope. The P proteins were associated with nucleocapsids and were not detected at the surface of virions. Both forms of the fusion glycoproteins were on the exterior of the viral envelope. Herein the properties of the P proteins are compared with similar proteins of rhabdoviruses and other paramyxoviruses, and a role for multiple forms of proteins in the genetic economy of newcastle disease virus is discussed.

Disulfides↗

Observations on the use of Komarov strain of Newcastle disease vaccine in the Sudan.

Broilers at 18 days old were vaccinated with a single dose of the K strain of Newcastle disease vaccine administered by different routes. The serological results obtained by haemagglutination inhibition at weekly intervals post-vaccination showed that birds vaccinated intranasally (i/n) or intramuscularly (i/m) had antibody titres higher than those vaccinated by the oral method. Furthermore, when challenged 3 weeks after vaccination, those broilers vaccinated i/n or i/m had 75% and 70% resistance respectively, while those vaccinated by the oral or spray methods failed to withstand the challenge.

Administration, Intranasal↗

[Effect of coccidiostats on the quality of the immune response following the vaccination of chickens against Newcastle disease].

An experiment was carried out to test the effect of two coccidiostatica, amprol and monensin, on the level of the Newcastle disease anti-hemagglutinins. The study made use of broiler chickens of a four-line hybrid (Plymouth Rock x Cornish) treated with a Hitchner B vaccine. The drugs were admixed with the feed--amprol at the rate of 0.5 g/kg, and monensin at 1 g/kg throughout the entire experimental period. The level of antibodies was recorded by means of the IH level. Highest titers of anti-hemagglutinins were discovered in the group treated with monensin. The birds of this group had higher liveweight as against the remaining birds.

Amprolium↗

Resistance of chickens to challenge with the virulent Herts 33 strain of Newcastle disease virus induced by prior infection with serologically distinct avian paramyxoviruses.

Results indicate that some degree of protection from challenge by Newcastle disease virus (NDV)/Herts 33 was conferred on chickens by prior infection with PMV/turkey/Wisconsin/68, PMV/turkey/Ontario/6661/68, PMV/Netherlands/449/75 and PMV/parakeet/England/39/78 viruses, all of which are serologically related but distinguishable from NDV. Except for one bird which survived challenge three weeks after infection with Robin/Hiddensee/19/75, no protection was seen in chickens infected with other unrelated avian paramyxoviruses. In contrast to infection with NDV-B1, birds protected by infection with avian paramyxoviruses showed large increases in NDV haemagglutination inhibition (HI) titres after challenge. In these birds considerable increases in the homologous HI titres were also seen after challenge.

Animals↗

Fusion of Newcastle disease virus with liposomes: role of the lipid composition of liposomes.

We demonstrate here that fusion occurs between the membrane of the Newcastle disease virus (NDV) and liposomes. Fluorescence dequenching studies (using Rhodamine-bearing viral envelopes) revealed the mixing of the lipids constituting the viral and liposomal membrane. The digestion of internal viral proteins by trypsin-containing liposomes indicated the mixing of the internal aqueous compartments. This last assay is independent of exchange of lipids between liposomal and viral membrane in the absence of fusion. Investigation of the effects of liposomal composition indicated that the presence of phosphatidylethanolamine and gangliosides are essential to optimize fusion. The fact that the Newcastle disease virus membrane can fuse with liposome also confirms that fusion must be determined by the viral proteins and could be mostly independent of the nature or presence of the host proteins.

Cholesterol↗

The production of colibacillosis in turkeys following sequential exposure to Newcastle disease virus or Bordetella avium, avirulent hemorrhagic enteritis virus, and Escherichia coli.

Female large white turkeys were intranasally inoculated with either Newcastle disease virus (ND) or Bordetella avium (BA) at 4 weeks of age. This was followed by oral inoculation with an avirulent (vaccine) strain of hemorrhagic enteritis virus (HE) at 5 weeks and intravenous inoculation with Escherichia coli (EC) at 6 weeks. Control birds received ND, BA, or HE followed by EC; EC alone; or nothing at all. Turkeys receiving one agent prior to EC challenge did not experience a significant increase in mortality or pericarditis. Those exposed to ND or BA followed by HE and EC experienced a significant elevation in mortality and pericarditis. A highly significant positive correlation between the number of infectious agents encountered during primary exposure and the incidence of colibacillosis after EC challenge was demonstrated.

Administration, Intranasal↗

Cellular and humoral response of in ovo-bursectomized chickens to experimental challenge with velogenic Newcastle disease virus.

Humorally deficient, in ovo-bursectomized (Bx) and sham-Bx chickens were vaccinated twice, 1 month apart, with Newcastle disease virus (NDV) Roakin strain and challenged with a velogenic viscerotropic NDV strain via the oronasal route. Hemagglutination-inhibition and seroneutralization tests showed that Bx chickens had reduced antibody-mediated immunity to virus infection. In contrast, they had significantly higher cell-mediated immunity (CMI) before challenge, as estimated simultaneously by determination of blastogenic capacity of peripheral blood lymphocytes induced by phytohemagglutinin and by specific antigen stimulation. After virus challenge, there was transitory inhibition of CMI based on marked reductions in levels of stimulation indices, and this impairment in CMI was supported by persistence of virus in Bx chickens for longer periods. Bx chickens resisted challenge, even though antibody titers were well below those considered predictive of resistance to challenge, suggesting that CMI provides a degree of resistance to velogenic NDV.

Animals↗

A phylogenetic study of South African Newcastle disease virus strains isolated between 1990 and 2002 suggests epidemiological origins in the Far East.

Genetic comparisons were made of the fusion protein sequences of 155 Newcastle disease virus isolates collected in South Africa between 1990 and 2002. Their evolutionary relationships and origins are described. All of the lentogenic field isolates were shown to be derived from commercial vaccines. No true South African lentogenic wild type strain was identified. Furthermore, it was shown that almost all mesogenic isolates had avirulent F(0) cleavage site sequences. Three major epizootics occurred in South Africa during the period of this study. The first outbreak (1990/1991) was caused by viruses endemic to South Africa since the 1960's (genotype VIII) but were occasionally also isolated in 2000. Genotype VIIb viruses, implicated in the severe outbreaks during 1993/1994, persisted until 1999. Genotype VIId viruses, responsible for the most recent outbreak in 1999/2000, had their origins in the Far East like those of the two previous outbreaks.

Amino Acid Sequence↗

Protection against hemorrhagic enteritis and Newcastle disease in turkeys by embryo vaccination with monovalent and bivalent vaccines.

The feasibility of embryo vaccination against Hemorrhagic enteritis (HE) and Newcastle disease (ND) in specific-pathogen-free turkey embryos was studied. Turkey eggs were injected with marble spleen disease virus (MSDV) at embryonation day (ED) 24, and tissues of poults hatching from virus-injected eggs were examined for MSDV. The virus was detected in spleen, intestine, liver, and bursa between 4 to 10 days postinoculation (PI). The peak titer of MSDV was present in the spleen at 6 days PI. Poults hatching from eggs injected with MSDV produced antibodies to the virus and resisted a challenge with virulent hemorrhagic enteritis virus (HEV) at 4 weeks of age. The B1 strain of NDV (NDV-B1) injected in turkey eggs at ED 24 killed the embryos. NDV-B1 modified by treatment with ethylmethane sulfonate (NDV-B1-EMS) was not lethal for turkey embryos. Poults hatching from eggs injected at ED 24 with NDV-B1-EMS developed antibodies to NDV and were protected from challenge exposure with virulent NDV at 4 weeks of age. Poults from eggs inoculated at 24 ED with a bivalent vaccine containing MSDV and NDV-B1-EMS developed antibodies to both viruses and were resistant to challenge with both virulent viruses. The study showed that SPF turkeys may be immunized by in ovo injection of live viral vaccines.

Animals↗

Local immunity against Newcastle disease virus in the newly hatched chicken's respiratory tract.

Inoculation of 200 mean egg infectious doses (EID(50)) of lentogenic Newcastle disease virus strain B1 (NDV-B1) into the air sac of 4-day-old specific-pathogen-free chicks provided significant protection against challenge of the air sac with 100 chicken mean lethal doses (LD(50)) of velogenic NDV-H but no protection against reinfection when the challenge was by the eye. Conversely, inoculation of the eye with 200 EID(50) of NDV-B1 provided significant protection against challenge of the eye but not of the air sac with 100 chicken LD(50) of NDV-H. Birds that received both antiserum and intraocular immunization were subsequently protected against both eye and air-sac challenge. On the other hand, birds that received antiserum and air-sac immunization were protected only against air-sac challenge but not against ocular challenge. Low levels of passively administered antibody did not prevent infection of the eye or air sac but greatly reduced the mortality rate after inoculation of either the vaccine or the challenge viruses. Passively administered antibody also suppressed hemagglutination-inhibiting and virus-neutralizing antibody formation stimulated by air-sac infection but not antibody formation stimulated by ocular infection. These data are consistent with the hypothesis that local immunity is responsible for prevention of infection, since birds were immune to reinfection at one site and simultaneously susceptible at the other site of infection.

Air Sacs↗

Antigenic relationships among Newcastle disease virus mutants obtained from laboratory strains and from recent California isolates.

The antigenic relationship between pairs of plaque mutants of Newcastle disease virus (NDV) derived from laboratory strains and from isolates from the 1971-72 California epizootic were examined by kinetic neutralization test. Comparing four sets of mutants from laboratory strains by both kinetic neutralization and hemagglutination inhibition tests, a similarity was found in the antigenic relationship expressed as an r value with both tests. However, kinetic neutralization was the more precise as well as sensitive assay. Antigenic diversity was greatest between pairs of mutants from different strains, but distinctions could also be made between mutants from the same strains such as Herts-L and Herts-S with an r value of 36%. Examination of mutants from the California epizootic isolated from separate locations and at different times showed antigenic divergence which was greatest between two red-plaque mutants with an r value of 39%. Antigenic distinctions were found between a red- and clear-plaque mutant obtained from isolates taken from brain and tracheal swabs of one infected chicken. In addition to antigenic divergence found between pairs of some mutants, two of the clear-plaque mutants reacted more avidly with antibody than did the corresponding red-plaque partner. Thus, both differences in antigenicity and avidity can be found among these NDV mutants. The antigenic variation found among these mutants is similar to that found within a serotype. This would imply that at the present NDV is a single serological type.

Animals↗