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Primary and secondary antibody responses to intramuscularly administered proteins of Escherichia coli (F11), Newcastle disease virus (NCD), infectious bronchitis virus (IB), and infectious bursar disease virus (IBD), respectively, were measured at weekly intervals in two chicken lines. The latter had been divergency selected for high and low antibody responses to sheep red blood cells (SRBC), and in a random-bred control line. An oil-based adjuvant was required to induce primary and secondary antibody responses to NCD, IB, and IBD. With respect to F11, elevated antibody responses were found in birds sensitized and boosted to F11 with and without adjuvant. The humoral response to F11 and to all viral antigens was significantly higher in the high (H) line than in the low (L) line, whereas the control (C) line showed intermediate titers. At 5 and 17 weeks of age, L line birds were significantly heavier than birds of the H and the C lines. A negative phenotypic correlation within lines between body weight at 17 weeks of age and antibody titers at 1 week after sensitization was found, but no further correlations between humoral responses and body weight or growth could be established. The present results suggest that selection for enhanced humoral responsiveness to SRBC resulted in enhanced responsiveness to components of several vaccines. Mechanisms underlying the relationship between divergent selection for immune responsiveness and body weight are discussed

We examined replication of Newcastle disease virus (NDV) by using minigenomes consisting of the 3' leader and 5' trailer regions of NDV flanking a reporter gene encoding secreted placental alkaline phosphatase (SEAP). Negative-sense minigenome RNA was generated from transfected plasmid DNA by means of in vivo transcription. Subsequent replication of minigenome RNA was determined either after infection with NDV helpervirus or after contransfection with helperplasmids that expressed the essential viral replication proteins NP, P, and L. In both systems, efficient replication of minigenome RNA was observed only if the genome size was a multiple of six nucleotides. Hence, in these systems, replication of NDV minigenome RNA's is strictly dependent on the rule-of-six. When the supernatant from helpervirus-infected, transfected cells was used to infect fresh monolayers, efficient transfer of SEAP activity by virus-like particles was observed only if the size of the minigenome RNA obeyed the rule-of-six. However, after several serial passages, we also observed efficient transfer of SEAP activity by virus-like particles derived from minigenome RNA's that did not obey the rule-of-six. Evidence was obtained which indicated that successful replication of these minigenomes was not due to a change in genome size.

Ornithobacterium rhinotracheale was found to cause growth retardation in both turkeys and chickens after experimental intra-air sac administration and to cause growth retardation together with airsacculitis and pneumonia after aerosol administration. Both turkey and chicken isolates of O. rhinotracheale were able to induce the same kind of respiratory inflammations and weight-gain losses in chickens as well as turkeys. Turkey rhinotracheitis virus was found to have a triggering effect on the O. rhinotracheale infection in turkeys, and Newcastle disease virus and to a lesser extent infectious bronchitis virus showed triggering effects on the O. rhinotracheale infection in chickens. Ornithobacterium rhinotracheale could be reisolated from affected organs of experimentally infected birds.

Synthetic polymers were examined for their potency to enhance mucosal immune responses to inactivated antigens. Aqueous solutions of polyacrylic acid with a MW of 450 kDa (p[AA]) or an butyl–ester thereof with 16% esterification (Butyl16–p[AA]) plus antigen were administered twice intranasally in mice with a 2 week interval. The frequency of IgA-antibody secreting cells (ASCs) in lung cell suspensions was determined 1 week after the second immunisation. Both polymers significantly enhanced the IgA response against inactivated Newcastle disease virus (iNDV), inactivated influenza virus strain MRC-11 (iMRC-11), haemagglutinin/neuraminidase subunits of influenza virus strain A/Texas (HA/NA) and bovine serum albumin (BSA). Butyl16–p(AA) was significantly more effective than non-derivatised p(AA), cholera toxin B subunit (CTB) or liposomes. The factor of increase in IgA-ASCs varied from <10- to >100-fold and depended on the type of antigen, the dose of antigen and the adjuvant. Extremely high responses of about 10,000 IgA-ASCs per million lung cells were detected after immunisation with 5 μg HA/NA plus 50 μg Butyl16–p(AA). Intranasal immunisation with Butyl16–p(AA) resulted in high IgA responses, not only in the lungs, but also in the spleen and in high IgG responses in these organs. We concluded that alkyl–esters of polyacrylate are an interesting, novel category of mucosal adjuvants.

A paramyxovirus with a thermostability of 60 min (typical of velogenic viruses) and a mean death time of > 90 h (typical of lentogenic viruses) was isolated from layers near Mooi River, South Africa. Our results, based on comparative nucleotide sequence data indicated that the virus is pigeon paramyxovirus 1 (PPMV-1), a variant of Newcastle disease virus. The F0 cleavage site contains a 112RRKKRF117 motif, and the virus had 98% sequence identity with PPMV-1 strains from the Far East. PPMV-1 was last reported in South Africa during the 1980s, with this being the first report of PPMV-1 isolated from chickens in South Africa.

The onset of protective immunity from lethal Newcastle disease virus (NDV) challenge of chicks was determined after vaccination with a recombinant herpes virus of turkeys (HVT) expressing the fusion and hemagglutinin-neuraminidase proteins of NDV. One-day-old specific-pathogen-free chicks devoid of maternal antibodies to NDV were vaccinated with 130 to 3300 plaque forming units of HVT (depending on the trial) and then challenged at 4, 7, 10, and 14 days postvaccination (DPV) with a neurotropic velogenic strain of NDV (GB Texas). The recombinant vaccine afforded 0%, 35-75%, 85%, and 94-100% protection when the vaccinated birds were challenged at 4, 7, 10, and 14 DPV, respectively. In all trials, challenge caused 100% mortality in unvaccinated control chicks. Newcastle disease virus was reisolated from the lung, liver, spleen, and brain of birds dying in all trials regardless of vaccine dosage or time of challenge, except when challenge occurred at 14 DPV

Excessive unexplained mortality was observed in flocks of double-crested cormorants located at Snake Island in Green Bay, Michigan, in June 1992. Clinical signs included weakness, lethargy, diarrhea, respiratory distress, paralysis of the wings and legs, torticollis, and incoordination. The most significant and consistent gross lesions included edema of the eyelids and periocular tissues, pulmonary edema and congestion, marked splenomegaly, hepatic necrosis, and scattered hemorrhages in visceral organs. Histologically, the principal alterations were severe lymphocytic meningoencephalitis and myelitis, as well as splenic lymphoid necrosis with hemorrhage. A type 1 paramyxovirus was isolated from the affected birds and characterized as a velogenic neurotropic strain of Newcastle disease virus. Since the infection occurred in free -living migratory birds, there exists the potential for spread of the virus over a large area, thus posing a hazard to domestic poultry

A triple one-step RT-PCR was developed to screen and differentiate virulent from avirulent Newcastle disease virus (NDV) isolates. Three sets of oligonucleotides were designed, each specific for amplifying NDV fusion protein gene-specific RNA from virulent, avirulent or all isolates respectively. The sensitivity of one-step RT-PCR was determined using viral RNA extracted from serially diluted NDV-infected allantoic fluid and found to be 10ˉ⁵ HA units. Application of one-step RT-PCR to various NDV samples, including wild-type virulent isolates and avirulent vaccine strains, demonstrated the potential for rapid identification (3-4 h) of NDV isolates as well as the differentiation of virulent from avirulent strains.

Ornithobacterium rhinotracheale was first isolated from broilers in South Africa in 1991. The importance of O. rhinotracheale infections has been established, with growth suppression, respiratory symptoms, and arthritis commonly seen as complications. Dual infection with Newcastle disease and O. rhinotracheale in 28-day-old broilers led to more severe respiratory lesions and higher mortality rates than in birds with only Newcastle disease. It was concluded that the pathogenicity of Newcastle disease virus was enhanced when occurring in combination with O. rhinotracheale. Also of interest was the first isolation of O. rhinotracheale from the liver

Three isolates of Newcastle disease virus (NDV) from cormorants and turkeys were classified as velogenic neurotropic NDV (VNNDV) by standard pathotyping procedures in specific-pathogen-free white leghorn and white rock chickens. White leghorns inoculated by eye drop, cloaca, intravenous, or intracerebral routes had a higher frequency of nervous signs and mortality than was observed in similarly inoculated white rocks. Two backpassages in white rocks increased the intravenous pathogenicity index of all three isolates, but none had a value after backpassage that was as high as the classical VNNDV strain Texas GB. The breed of chicken used in standard procedures did influence the numerical values of pathotyping determinations, but the differences between breeds were not large enough to change the pathotype assigned to these isolates