Oral immunization against experimental salmonellosis I. Development of temperature-sensitive mutant vaccines

Mutant strains of Salmonella enteritidis were selected for their inability to proliferate at 37 C; when exposed to this temperature, these organisms formed tangled masses of long filaments in liquid media, presumably as a result of their inability to form cross septa. The mutants were also incapable of synthesizing flagella protein. A study of the biological charateristics of the mutants indicated that in most respects they resembled the parent strain of S. enteritidis; however, they were avirulent for mice, presumably because of the restriction of growth imposed by the body temperature of the animal. Preliminary studies have suggested that these mutants are highly effective in inducing protection against severe challenge infections of S. enteritidis; of especial interest is the fact that, when given orally, the mutants conferred a substantial degree of protection against oral infection with the virulent strain.

Oral Immunization in Experimental Salmonellosis II. Characteristics of the Immune Response to Temperature-Sensitive Mutants Given by Oral and Parenteral Routes

A temperature-sensitive mutant of Salmonella enteritidis, selected because of its inability to proliferate normally at 37 C, has been used as a living vaccine in mice. When given parenterally or orally, it confers a high degree of resistance against otherwise lethal S. enteritidis infections given intraperitoneally or by mouth. In contrast to most other effective living Salmonella vaccines, the temperature-sensitive mutant survives for only short periods in mouse tissues. Although the vaccine provides protection against S. typhimurium infection, possibly because of antigenic relationships between the immunizing and challenge organisms, it is ineffective against the intracellular infection caused by Listeria monocytogenes. A study of the kinetics of S. enteritidis infection in the liver and spleen of normal and immunized mice has suggested that immunity is dependent upon development of a secondary immunological response which arises approximately 7 days after introduction of the challenge infection. Although humoral antibody production forms part of this secondary response, it is not necessarily responsible for control of the infection.

Oral Immunization in Experimental Salmonellosis III. Behavior of Virulent and Temperature-Sensitive Mutant Strains in the Intestinal Tissues of Rats

Infection of rats via a Peyer's patch has been used as a means of studying the behavior of Salmonella enteritidis in intestinal tissues. The course of infection in the Peyer's patch and draining mesenteric lymph node is characterized by multiplication of the organism over a period of 4 days followed by a gradual decline in numbers; the organism also passes to the liver and spleen and may be isolated from these organs as well as the intestinal tissues for at least 4 weeks. Temperature-sensitive mutants derived from the virulent strain are unable to multiply and do not pass to the liver and spleen; they remain viable for periods of less than 2 weeks. A quantitative technique based on the number of viable organisms remaining in the injected Peyer's patch 48 hr after infection has been used to assess the immune state of rats. The results have clearly demonstrated that Salmonella immunity can only be induced by living vaccines and that although viable organisms remain in the reticuloendothelial tissues, organisms given in a challenge infection are immediately subject to enhanced bactericidal activity within the intestinal tissues. Under the conditions used here, humoral antibody does not seem to offer any protective effect against Salmonella infection in the intestinal lymphoid tissues.

Diagnosis of infectious laryngotracheitis using a monoclonal antibody ELISA

An ELISA has been developed which uses a selected monoclonal antibody specific for ILT virus. The ELISA proved to be as accurate as, yet faster than, virus isolation, more accurate than the fluorescent antibody test and more accurate and rapid than the relatively simple agar gel precipitin test. The ELISA clearly differentiated between chickens from commercial flocks infected with ILT virus and non-infected chickens, or chickens infected with other respiratory pathogens.

Molecular characterization of highly virulent fowl adenoviruses associated with outbreaks of inclusion body hepatitis

Restriction enzyme analysis of DNA was used to characterize fowl adenoviruses (FAVs) consistently associated with outbreaks of acute inclusion body hepatitis. When low doses of these FAVs were administered via a natural route to chickens they caused IBH. A strong genomic relationship was demonstrated between these virulent FAVs. In contrast, the genomes of serologically related, but non-virulent or mildly virulent FAVs were found to differ substantially from those of the virulent FAVs.

The major histocompatibility complex and genetic control of antibody response to sheep red blood cells in chickens

The genetic association of the B-F/B-L region of the chicken major histocompatibility complex (MHC) with the antibody response to sheep red blood cells (SRBC) was investigated using three inbred lines of White Leghorn chickens. Two out of the three inbred lines of chickens. J1 and N1, were found to be a low responder to SRBC. Planned matings between the three inbred lines of chickens showed that the genetic regulation of the magnitude of the antibody response to SRBC was associated with the MHC. The low antibody response to SRBC was inherited as a recessive trait linked to the B15 MHC phenotype of the M1 inbred line.

The appearance of viral antigen and antibody in the trachea of naive and vaccinated chickens infected with infectious laryngotracheitis virus

In chickens vaccinated with SA-2 infectious laryngotracheitis (ILT) virus, viral antigen could no longer be detected in tracheal washings from day 7 post infection (pi). Total specific antibody was detected in tracheal washings from day 5 pi, IgA antibody appeared at day 6 pi, but neutralising antibody could not be detected until day 14. In the serum of vaccinated chickens, total antibody appeared on day 5 pi and neutralising antibody on day 7. However, no IgA antibody could be detected in serum. There was a substantial increase in the numbers of IgA- and IgG-synthesising cells in the trachea by day 3 pi, with a marked increase in the numbers of IgA-positive cells at day 7 pi. Following challenge with virulent CSW-1 ILT virus, no virus could be detected in the trachea of vaccinated chickens. There was also no evidence of an anamnestic antibody response in the trachea or in serum up to day 10 post challenge, and there was no significant change in the numbers of IgA- or IgG-synthesising cells in the tracheas of vaccinated chickens up to day 7 post challenge.

Raloxifene and estrogen inhibit neointimal thickening after balloon injury in the carotid artery of male and ovariectomized female rats

The effects of raloxifene and 17alpha-ethinyl estradiol (EE2) on intimal thickening in response to balloon injury were tested in male and ovariectomized female rats. In male rats, oral raloxifene and EE2, administered either by gavage or in the diet, inhibited arterial intimal thickening in response to balloon injury to a maximum of approximately 60 and 50%, respectively. The effect of oral raloxifene to decrease cholesterol was observed at doses (> or = 3 mg/kg/day) higher than those required to inhibit intimal thickening (> or = 0.03 mg/kg/day). Coadministration of the estrogen receptor antagonist, ICI 182,780 (5 mg/kg/day, s.c.), blocked the inhibition of balloon injury by raloxifene and EE2. Direct adventitial delivery of raloxifene (0.03 mg/kg/day) and EE2 (0.001 mg/kg/day) to the vascular wall inhibited intimal thickening by 63 and 53%, respectively. In ovariectomized female rats, oral raloxifene (0.01-3.0 mg/kg/day) and EE2 (0.08 mg/kg/day) inhibited intimal thickening to a maximum of 32 and 60%, respectively. Together, these data suggest that raloxifene and EE2, inhibit balloon arterial injury in the rat through direct effects on the vascular wall that involve the estrogen receptor and are at least partially independent of serum cholesterol.

LY320135, a novel cannabinoid CB1 receptor antagonist, unmasks coupling of the CB1 receptor to stimulation of cAMP accumulation

LY320135 is a selective antagonist for the brain CB1 receptor, having greater than 70-fold higher affinity for the CB1 than the peripheral CB2 receptor. The Ki values for LY320135 at the CB1 and CB2 receptors, transfected and stably expressed in cell lines, were 224 nM and > 10 microM, respectively. Similar Ki values were measured in binding studies performed on cerebellum and spleen membrane preparations endogenously expressing the CB1 (203 nM) and CB2 (> 10 microM) receptors, respectively. LY320135 functionally reversed anandamide-mediated adenylate cyclase inhibition in Chinese hamster ovary (CHO) cells stably expressing the CB1 receptor. Pertussis toxin treatment of CHO cells expressing the CB1 receptor attenuated the anandamide-mediated inhibition of adenylate cyclase and unmasked a stimulatory effect of anandamide on adenylate cyclase. The stimulatory component was blocked with LY320135. This compound also blocked WIN 55212-2-mediated inhibition of N-type calcium channels and activation of inwardly rectifying potassium channels in N18 and AtT-20-CB2 cells, respectively. LY320135 is a promising lead compound for the further development of novel, potent and selective cannabinoid antagonists of novel structure.

Immunopathogenesis and physical maps of fowl adenovirus serotype 9

Restriction endonuclease maps of the genome of fowl adenovirus (FAV) serotype 9 have been constructed for the restriction endonucleases NdeI, NotI and XbaI. The total size of the FAV-9 genome was estimated to be 44.5 kb pairs, consistent with previous reports that FAV genomes are approximately 10 kb larger than human adenovirus (HAV). The pathogenicity of this virus in day-old chickens was intermediate between the pathogenicity of the non-pathogenic and the highly pathogenic FAVs.

Cloning and sequencing of the chicken anaemia virus (CAV) ORF-3 gene, and the development of an ELISA for the detection of serum antibody to CAV

Chicken anaemia virus (CAV) is a small, unclassified virus involved in anaemia and suspected of causing immunosuppression in young chickens. We have developed an ELISA for the detection of serum antibody to CAV based on cloned antigen. The gene for ORF-3 (the putative capsid protein) was cloned, sequenced and expressed in a bacterial expression system, pGEX. An ORF-3 fusion protein was used to produce an indirect ELISA.

Molecular characterisation of peanut agglutinin-binding glycoproteins from Eimeria tenella

A group of glycoproteins, which strongly bind peanut agglutinin (PNA) was found in Eimeria tenella. Two major antigenic glycoproteins, Et110gp and Et35gp, were identified in sporulated oocysts and sporozoites. Molecular characterisation of carbohydrate moieties (lectin binding, enzymic hydrolysis and monosaccharide composition) revealed that both glycoproteins are rich in galactose and N-acetylgalactosamine, and appear to be sialylated. Both glycoproteins were susceptible to treatment with neuraminidase followed by O-glycosidase, suggesting that the oligosaccharide chains are attached to the protein by an O-glycosidic linkage to serine and/or threonine. Purified Et35gp contained a large number of serine (14) and threonine (33) residues, and was rich in glycine. This protein aggregated after repetitive lyophilisation and migrated on SDS-PAGE gels as an 85,000 protein. Sera against purified Et35gp raised in chickens and rabbits, and anti-E. tenella immune chicken serum recognised both antigens on blots and on the surface of sporozoites. Chickens immunised with purified Et35gp were not protected against coccidial infection.

Serological relationships within the group E fowl adenoviruses

Antisera were raised in chickens to six group E fowl adenoviruses (FAV) which have been divided into a highly virulent (hypervirulent) and a mildly virulent subgroup using restriction endonuclease analysis. Virus neutralisations showed that these two distinct restriction endonuclease groups were distinguishable serologically, and indicated a possible vaccine candidate for use against the hypervirulent FAV. The suitability of this candidate was established in challenge experiments where vaccination with this virus protected against challenge from another hypervirulent virus as well as one of the mildly virulent FAV.

Infectious laryngotracheitis virus growth, DNA replication, and protein synthesis

The polypeptides associated with infection of primary chicken kidney (CK) cells with infectious laryngotracheitis virus (ILTV) were examined by metabolic labelling with [35S]methionine and SDS-PAGE. Polypeptide synthesis was followed over the first 24 h post-infection (p.i.) as this was shown to be the period of viable virus production. A total of 16 ILTV encoded or induced polypeptides were identified using metabolic labelling. The use of inhibitors of protein and DNA synthesis in conjunction with metabolic labelling and viral DNA replication studies enabled a cascade pattern of gene expression, similar to that of herpes simplex virus type 1 (HSV-1), to be established for ILTV. Representatives of alpha, beta, gamma 1 and gamma 2 classes of genes were identified. In contrast to infection with HSV types 1 and 2, which leads to a rapid inhibition of total host cell polypeptide synthesis, ILTV infection of CK cells did not result in a complete inhibition of cellular protein synthesis, with only a small number of host cell polypeptides absent from infected cells.

Enhanced H2O2 release from immune chicken leucocytes following infection with Eimeria tenella

Cell-mediated immunity is thought to be important in the resistance of chickens to infection by coccidia, and it has been demonstrated that sporozoites of Eimeria tenella are very sensitive to superoxide ions. Therefore an investigation into the cellular responses in naive specific pathogen-free and hyperimmune birds was carried out with particular attention to their ability to produce reactive derivatives of oxygen. Leucocytes were isolated from the blood, spleen and caecal mucosa of chickens infected with E. tenella and assessed for their ability to release H2O2. Leucocytes obtained from the blood and spleen of hyperimmune birds 1 day after challenge showed an elevated ability to produce reactive oxygen intermediates. In contrast, the ability of leucocytes from naive chickens to produce these molecules was transiently depressed after challenge. Prior to challenge, mucosal leucocytes from immune chickens were also able to release heightened levels of H2O2 when compared with cells from naive chickens.

Physicochemical and immunological characterization of recombinant host-protective antigen (VP2) of infectious bursal disease virus

Small fusions to the N-terminal end of the host-protective antigen (VP2) of infectious bursal disease virus lead to stable expression of VP2 in Escherichia coli and yeast, and reduce the levels of inclusion body formation in E. coli in comparison to VP2 constructs with larger N-terminal fusions. VP2 produced with small N-terminal fusions, like native viral VP2, can be fractionated into a high molecular weight 'multimeric' form and a monomeric form. A virus-neutralizing monoclonal antibody that only recognizes undenatured VP2 preferentially reacts with multimeric forms of recombinant VP2. Both native and recombinant monomeric forms of VP2 are non-immunogenic. The multimeric forms of viral and yeast-derived VP2 are highly immunogenic, while those produced in E. coli are not.

Gallid herpesvirus 1 (infectious laryngotracheitis virus): cloning and physical maps of the SA-2 strain

Clones representing 90% of the genome of Gallid herpesvirus 1 (infectious laryngotracheitis virus; ILTV) were obtained and used in hybridization experiments to construct EcoRI, KpnI amd SmaI physical maps. The genome was 155 kilobase pairs (kbp) and comprised of a long unique sequence (120 kbp) and a short unique sequence (17 kbp) bounded by repeat sequences each of 9 kbp. An unrelated second pair of repeat sequences was located at 0.67 and 0.88 map untis. A terminal repeat of the unique long region (UL) was also detected, but no isomerization of UL was detected.

Nucleotide sequence of the gene encoding infectious laryngotracheitis virus glycoprotein B

The nucleotide sequence of the infectious laryngotracheitis virus (ILTV) gene encoding the 205K complex glycoprotein (gp205) was determined. The gene is contained within a 3-kb EcoRI restriction fragment mapping at approximately map coordinates 0.23 to 0.25 in the UL region of the ILTV genome and is transcribed from right to left. Nucleotide sequence analysis of the DNA fragment identified a single, long open reading frame capable of encoding 873 amino acids. The predicted precursor polypeptide derived from this open reading frame would have a calculated Mr of 98,895 Da and contains nine potential glycosylation sites. Hydropathic analysis indicates the presence of an amino terminal hydrophobic sequence and hydrophobic carboxyl terminal domain which may function as a signal peptide and a membrane anchor sequence, respectively. Comparison of the predicted ILTV gp205 protein sequence with those of other herpesviruses revealed a significant sequence similarity with gB-like glycoproteins. Extensive homology was observed throughout the molecule except for the amino and carboxyl termini. The high homology in predicted primary and secondary structures is consistent with the essential role of the gB family of proteins for viral infectivity and pathogenesis.

Humoral responses and salmonellosis protection in chickens given a vitamin-dependent Salmonella typhimurium mutant

Humoral responses in chickens inoculated with an aromatic vitamin dependent (Aro-) Salmonella typhimurium mutant (STM) were studied to ascertain the efficacy of the organism as a vaccine for salmonellosis and possibly as a delivery system for antigens from enteric pathogens of chickens. Serum antibody responses in chickens that were given oral or subcutaneous inoculations of the bacterium followed the classic order of antibody production, with IgM being detected first, followed by IgG and IgA. Antibody responses in the gut of orally inoculated chickens were restricted to IgG and IgA. Weight gain measured in chickens given high doses of STM (up to 5 x 10(9)) orally, revealed that the bacterium did not adversely affect the chickens; in fact, inoculated chickens had significantly higher body weights than controls at the same age. Salmonellosis protection of chickens by oral vaccination with STM was examined in a vaccination/challenge experiment. The experiment revealed that oral vaccination reduced excretion of a virulent S. typhimurium used as the challenge organism.

Virus-neutralizing and passively protective monoclonal antibodies to infectious bursal disease virus of chickens

Murine monoclonal antibodies (MAbs) were produced to assist in the identification and characterization of the virus-neutralizing epitopes of infectious bursal disease virus (IBDV). Only MAbs that reacted in Western blotting with viral protein 2 (VP2) or immunoprecipitated VP2 neutralized the infectivity of the virus in cell culture and passively protected young chickens from infection. Three of the neutralizing MAbs did not react with denatured viral proteins. Additivity enzyme-linked immunosorbent assays indicated that the six virus-neutralizing MAbs recognized two spatially independent epitopes. The ability of two of the virus-neutralizing MAbs to neutralize a variant of IBDV that had escaped neutralization by all the other MAbs confirmed the existence of two distinct neutralizing epitopes. The results support the hypothesis that there are at least two non-overlapping epitopes recognized by the virus-neutralizing MAbs reported in this study, although these may still be within one conformational site on VP2 of IBDV.

Detection of infectious laryngotracheitis virus in chickens using a non-radioactive DNA probe

A DNA hybridization assay using a non-radioactive probe has been developed for the detection of infectious laryngotracheitis virus (ILTV) DNA. A 1.4-kilobase pair BamHI fragment of ILTV genomic DNA was cloned and then labeled by one of two methods; nick translation using 32P-dATP or non-radioactive labeling using a commercially available DNA labeling and detection kit. The non-radioactive DNA labeling method proved to be as sensitive as the radioactive method. Using the non-radioactive probe, ILTV DNA was readily detected in tracheal samples from acutely infected chickens and also from convalescent chickens at a time when viral antigen could no longer be detected by the enzyme-linked immunosorbent assay or the virus could no longer be reisolated. This technique provides a safe and effective means of identifying field outbreaks of ILTV and also may detect latent ILTV infections relatively quickly and inexpensively.

Passive protection against infectious bursal disease virus by viral VP2 expressed in yeast

Infectious bursal disease virus (IBDV), a pathogen of major economic importance to the world's poultry industries, causes a severe immunodepressive disease in young chickens. Maternal antibodies are able to protect the progeny passively from IBDV infection. The gene encoding the IBDV host-protective antigen (VP2) has been cloned and expressed in yeast resulting in the production of an antigen that very closely resembles native VP2. When injected into specific pathogen free chickens a single dose of microgram quantities of the yeast derived antigen induces high titres of virus neutralizing antibodies that are capable of passively protecting young chickens from infection with IBDV.

Detection of DNA from infectious laryngotracheitis virus by colourimetric analyses of polymerase chain reactions

A combination of the polymerase chain reaction and a novel ELISA-type DNA colourimetric assay (developed from studies with a retrovirus from man) was used in a preliminary study to detect DNA from avian infectious laryngotracheitis virus. The method is sensitive, specific and easy to perform. Since it can be readily adapted for the detection of DNA from other sources it could be useful for the identification of a variety of pathogens from other species of veterinary importance.

The role of mucosal antibody in immunity to infectious laryngotracheitis virus in chickens

The role of mucosal antibody in recovery from a primary infection and resistance to reinfection with infectious laryngotracheitis (ILT) herpesvirus was studied in bursectomized chickens, which were unable to synthesize specific antibodies. Viral antigen in the infected trachea was assessed by indirect immunofluorescence on tissue sections and by ELISA. The ability of bursectomized chickens to resolve primary infections as effectively as intact chickens and of vaccinated-bursectomized chickens to prevent the replication of challenge virus without the participation of mucosal antibody, is evidence for the importance of local cell-mediated rather than humoral immune mechanisms in the outcome of infection with ILT virus.

Humoral and cell-mediated immune responses to the glycoproteins of infectious laryngotracheitis herpesvirus

The viral glycoproteins of infectious laryngotracheitis virus, an alphaherpesvirus, were the dominant antigens recognised by immune chickens. Glycoproteins with molecular weights of 205, 160, 115, 90, 67, 60, and 52k reacted strongly in Western blotting studies with a majority of chicken antisera. Viral glycoproteins immunoprecipitated using monoclonal antibodies were also able to elicit a delayed-type hypersensitivity reaction in chickens previously vaccinated with a live vaccine. The 60 k glycoprotein alone and the antigenically related family of higher molecular weight glycoproteins (205, 160, 115, 90, and 85 k) both elicited significant increased in the thickness of the wattles of immune cockerels. Because the glycoproteins induce both antibody and cell-mediated immune responses they may prove to be important protective immunogens in a subunit vaccine.

Antigens of infectious laryngotracheitis herpesvirus defined by monoclonal antibodies

Monoclonal antibodies to glycoprotein and protein antigens of infectious laryngotracheitis virus (ILTV) were divided into five groups on the basis of their reactivity in immunofluorescence and Western blotting. Group I antibodies recognised a single band of 60 K and Group II antibodies recognised bands of 205, 160, 115, 90 and 85 k in Western blotting. In immunofluorescence both these groups of antibodies reacted with antigens located in the cytoplasm of fixed virus-infected cells and they also reacted with unfixed cells, suggesting that these antigens are on the surface of virus-infected cells. While Group I monoclonal antibodies did not react with extracts of tunicamycin-treated cells, some Group II antibodies recognised bands of decreased molecular weight compared to those present in untreated cells. The reactivity of the Group II antibodies with extracts of tunicamycin-treated cells suggested that they recognised at least three different epitopes which was confirmed by ELISA additivity assays. Monoclonal antibodies of Group III, Group IV and Group V recognised several low molecular weight proteins from 45 to 24 k. Immunofluorescence studies showed that these were nuclear and cytoplasmic antigens that were not present on the surface of virus-infected cells.

A conformational immunogen on VP-2 of infectious bursal disease virus that induces virus-neutralizing antibodies that passively protect chickens

VP-2b, a major structural protein of infectious bursal disease virus (IBDV), and its precursor protein VP-2a were separated in a soluble form from the supernatant of ultracentrifuged viruses by using a monoclonal antibody specific for VP-3, the other major structural protein, to remove soluble VP-3 and remaining virus particles. The native VP-2a/2b inhibited the majority of virus-neutralizing (VN) activity in chicken anti-IBDV sera and chickens immunized with VP-2a/2b produced VN antibodies that passively protected susceptible chickens from infection. However, the separated VP2a/2b was not as immunogenic as intact virus particles. VP-2a/2b would appear to contain a conformational epitope which is destroyed by SDS and boiling and which may prove to be of critical importance in a subunit vaccine against type 1 IBDV.

Immunogenic glycoproteins of infectious laryngotracheitis herpesvirus

The viral glycoproteins produced in cells infected with either vaccine strain or virulent isolates of infectious laryngotracheitis virus, an avian herpesvirus, were identified by in vitro labeling using [14C]glucosamine and [14C]mannose. Chicken antisera to the vaccine strain and to a virulent isolate, and rabbit antisera to the vaccine strain, immunoprecipitated four major viral glycoproteins of 205, 115, 90, and 60K mol wt. Additional glycoprotein bands were recognized by immune chicken and rabbit sera in Western blotting using a glycoprotein fraction purified from extracts of virus-infected cells. Monoclonal antibodies to the immunogenic glycoproteins were produced and characterized by immunoprecipitation and Western blotting. One group of monoclonal antibodies reacted only with the 60K glycoprotein, by both techniques, while a second group reacted with the 205, 115, and 90K glycoproteins in immunoprecipitation and with additional bands of 85 and 160K in Western blotting.

Assessment by ELISA of passively acquired protection against infectious bursal disease virus in chickens

The level of maternal antibody to infectious bursal disease (IBD) virus in the circulation of one-day-old layer strain chickens was found to be on average, 45% of the antibody titre in their respective dam, while the minimum ELISA titre which protected against a challenge of 1000 CID50 of virus was 400. Maternal antibody was found to disappear from the circulation of these crossbred chickens with a half-life of 6.7 days. From these data it is possible to estimate the ELISA titre necessary in vaccinated hens to provide the desired duration of passive protection; protection being assessed by an ELISA which measures IBD viral antigen in the bursa of Fabricius following challenge.

Predicted sequence of the host-protective immunogen of infectious bursal disease virus

The genome of Australian strain 002-73 of infectious bursal disease virus (IBDV) has been cloned as cDNA fragments into an expression library based on pUR plasmid vectors. Recombinant colonies were selected with a monoclonal antibody specific for the 32-kDa host-protective immunogen of IBDV and fully characterized by nucleotide sequence analysis. The amino acid sequence of several tryptic peptides derived from the native 32-kDa structural protein has confirmed the coding region assignment and nucleotide sequence data. We believe this to be the first published sequence of a birnavirus-encoded protein and these data may provide the basis for an effective subunit vaccine against IBDV.

In vitro infection studies with infectious laryngotracheitis virus

Infectious laryngotracheitis (ILT) virus strains were studied for their ability to infect chicken macrophages, lymphocytes, and kidney cells in vitro. Although macrophages were as susceptible as chicken kidney cells to infection, replication of most virus strains in macrophages was markedly restricted. Only a few isolates induced progressive infections in macrophages, and even with these the donor of the macrophages influenced replication. Thus, it appears that both cell genotype and virus genotype may help determine the extent of restriction of virus replication. Macrophages were more susceptible to an attenuated vaccine strain of ILT virus than to virulent virus strains. Spleen lymphocytes, peripheral blood lymphocytes, thymocytes, bursal lymphocytes, buffy coat leukocytes, and activated T-cells were nearly or totally refractory to infection by ILT virus.

Expression in Escherichia coli of cDNA fragments encoding the gene for the host-protective antigen of infectious bursal disease virus

The larger segment of the IBDV genome codes for a 32-kDa host-protective antigen. Inserts from a cDNA library in pBR 322, containing overlapping cDNA fragments of varying sizes and covering the entire large segment of the IBDV genome, were subcloned into a mixture of expression vectors pUR 290, 291, and 292. Clones expressing the host-protective antigen, or parts of it, were identified by an immunoblot assay and the fusion proteins were further characterized by Western blot analysis using a monoclonal antibody specific for the 32-kDa polypeptide. Hybridization of inserts from expressing clones to the original cDNA library led to the identification of the region of the IBDV genome that codes for the 32-kDa host-protective antigen. Clone D1 which encodes approximately 50% and clone D6 which encodes the entire 32-kDa protein were selected for further studies. The fusion proteins from clones D1 and D6 were affinity purified and tested for their immunogenicity in chickens. Both fusion proteins induced the synthesis of antibodies in both primed and unprimed chickens that reacted specifically with denatured 32-kDa viral protein, but less well with intact virus. It was concluded that the response to the fusion proteins was to linear rather than conformational epitopes on the 32-kDa viral protein.

Gallid-1 herpesvirus infection in the chicken. 3. Reinvestigation of the pathogenesis of infectious laryngotracheitis in acute and early post-acute respiratory disease

Specific-pathogen-free chickens were infected via the trachea when 4 weeks old with 2000 plaque-forming units (PFU) of the virulent Australian infectious laryngotracheitis (ILT) virus strain CSW-1. Titers of ILT virus in the trachea were greatest (10(7.0) PFU/ml in washings, 10(6.0) PFU/g of tissue) 2-4 days postinfection (PI). Infectivity then declined rapidly, to become undetectable by 7 days PI, although highly localized areas of ILT antigen in the tracheal epithelium were occasionally observed by fluorescent antibody staining at 7 and 8 days PI. Tracheal organ cultures established 7 and 8 days PI provided no evidence of latent ILT virus infection at this immediate post-acute stage of pathogenesis. ILT virus was not isolated from peripheral blood leukocytes or lymphoid organs (spleen, bursa, thymus). ILT virus was found in the trigeminal ganglia and/or brain in 14 of 36 chickens (40%) examined between 4 and 7 days after intratracheal inoculation, but it was not in these tissues in five chickens examined at 8 days PI. Virus was also detected at 6 days PI in the trigeminal ganglia in one of five chickens infected by the conjunctival route. These data indicate that the early pathogenesis of ILT (CSW-1) infection frequently involves the tissues of the nervous system. In acute ILT in 4-week-old chickens, interferon-alpha/beta activity was not detectable in serum or tracheal exudates within 14 days PI, but tracheal washings contained significant virus-neutralizing activity by 7 and 8 days PI. In 3-day-old chickens infected via the trachea with 200 PFU of ILT CSW-1, the clearance of ILT virus from the trachea was similar to that observed in 4-week-old chickens, but ILT virus spread systemically to the livers of 20% by 5-7 days PI.

Antibody to the 32K structural protein of infectious bursal disease virus neutralizes viral infectivity in vitro and confers protection on young chickens

Chicken sera containing IgG antibodies specific for the 32 000 (32K) mol. wt. structural polypeptide of infectious bursal disease (IBD) virus, as assessed by Western blotting, neutralized the in vitro infectivity of tissue culture-adapted IBD virus. When injected into young chickens, the serum passively protected them from challenge with pathogenic IBD virus. Chickens immunized with the 32K structural polypeptide of IBD virus, prepared by electroelution from SDS-PAGE gels, produced antibody detectable by ELISA and the virus neutralization assay, while chickens immunized with the 37K or 41.5K viral polypeptides synthesized antibody detectable by ELISA, but only very low levels of virus-neutralizing antibody. The immunoglobulin fraction of sera obtained from chickens immunized with the 32K polypeptide, but not the 41.5K polypeptide, passively protected chickens from infection with IBD virus. It is concluded that the 32K polypeptide is a major protective immunogen of IBD virus.

Characterization by Western blotting of the immunogens of infectious bursal disease virus

The Australian isolate of infectious bursal disease (IBD) virus (002/73) was purified from infected bursae by rate-zonal and density-equilibrium centrifugation and characterized by polyacrylamide gel electrophoresis. Two major polypeptides having approximate mol. wt. of 32 000 (32K) and 37K and three other polypeptides of approximate mol. wt. 29K, 41.5K and 91.5K were present in all preparations of virus having a buoyant density of 1.33 g/ml. Western blotting of the polypeptides of IBD virus showed that the initial antibody response of chickens infected with live virus or injected with an inactivated oil-emulsion vaccine was directed primarily towards the 32K polypeptide. Only sera obtained late in the response to live virus or following hyperimmunization contained antibodies recognizing the 29K, 37K and 41.5K polypeptides. An antibody response to the 91.5K polypeptide was not detected routinely by this technique. It was concluded that the 32K polypeptide is a major immunogen of IBD virus.

The characterization and molecular cloning of the double-stranded RNA genome of an Australian strain of infectious bursal disease virus

The genome of infectious bursal disease virus (IBDV) strain 002-73 was found to consist of two segments of double-stranded (ds) RNA which were 3400 bp (MW 2.06 X 10(6)) and 2900 bp (MW 1.76 X 10(6)) long, respectively. The ds IBDV RNA could be translated, in vitro, only after extensive denaturation. The small RNA segment was found to code for a single polypeptide of MW 90K, while the large RNA segment coded for three major polypeptides of MW 52K, 32K, and 28K, and two minor polypeptides of MW 41K and 16K. The large RNA segment could encode proteins of MW 125K while the MW of the translated products was 169K suggesting that a precursor-product relationship exists between some of the translation products. A method is described for the synthesis of ds cDNA from large ds RNA molecules. Analyses of recombinant colonies showed that inserts covering the entire IBDV genome had been cloned.

Quantitation by ELISA of pili and sheep antibodies to the pili of Bacteroides nodosus

ELISA systems have been developed to quantitate the isotypic antibody response of sheep naturally infected with B. nodosus isolate 198 or injected with pili from isolate 198 in oil emulsion vaccines. The predominant humoral antibody detected following vaccination was IgG1, with substantially lower amounts of IgG2 and IgM. The antibody response was relatively specific for the pilus antigen from isolate 198. Although weak cross reactivities were detected with antiserums to some other isolates, ELISA IgG antibody titres in excess of 200 offer a tentative identification of the isolates of B. nodosus involved in natural outbreaks of footrot. A related ELISA was also developed to quantitate the amount of pili in cell suspensions and crude preparations of pili used in vaccines.

Development and evaluation of an ELISA for the detection of antibody to infectious laryngotracheitis virus in chickens

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibody to infectious laryngotracheitis (ILT) virus in chickens was developed and compared with the serum-neutralization assay. The ELISA routinely yielded 16-to-32-fold higher titers than the serum-neutralization test. To overcome the requirement for large amounts of purified viral antigen, the microtiter trays were initially coated with an antibody prepared against purified ILT virus. A relatively crude viral preparation could then be used to coat the trays. Sera from specific-pathogen-free chickens less than 12 weeks of age did not show nonspecific binding, although 2.7% of all sera from chickens between 13 and 64 weeks of age had nonspecific activity. The majority of nonspecific reactors came from one highly inbred flock of specific-pathogen-free chickens. A number of modifications of ELISA procedures reported to reduce the nonspecific binding of chicken sera were investigated. Treatment of the serum or the plate and changes in the composition of the diluent did not increase the relative sensitivity of the anti-ILT assay.