Palmitoyl derivatives of interferon alpha: potential for cutaneous delivery

Palmitoyl derivatives of interferon alpha2b (p-IFNalpha) were prepared by covalent attachment of the fatty acid to lysine residues in the protein through a reaction with N-hydroxysuccinimide palmitate ester. The p-IFNalpha was characterized by capillary electrophoresis (CE), mass spectrometry (MS), SDS-PAGE, and antiviral assay. Flow-through diffusion cells and human breast skins were used to measure cutaneous and percutaneous absorption. Formation of p-IFNalpha derivatives was demonstrated by CE to be dependent on reaction time and reagent: protein ratio. Electrospray MS of the crude p-IFNalpha mixture indicated three populations of IFNalpha derivatives with 10, 11, and 12 palmitoyl substitutions. The addition of palmitoyl residues to IFNalpha under the conditions described reduced the antiviral specific activity by 50%. However, the cutaneous absorption of p-IFNalpha was about 5-6 times greater than the parent protein. The amount of p-IFNalpha and IFN alpha in whole skin after 24 h of treatment was 2.106 +/- 1.216 microg/cm2 and 0.407 +/- 0.108 microg/cm2, respectively. Approximately two times higher flux was detected for p-IFNalpha compared to the nonfatty acylated IFNalpha. The total amount of drug diffused in 24 h was also approximately two times higher for the p-IFNalpha. The results indicate a potential for using fatty acylated derivatives of IFN alpha for dermal and transdermal delivery.

The abp locus of Streptococcus uberis encodes a protein homologous to polar amino acid and opine binding proteins of gram-negative bacteria

A gene locus abp was identified immediately upstream of the CAMP factor gene cfu in Streptococcus uberis. An open reading frame capable of coding for a 277-residue protein was identified. On the basis of sequence characteristics, the abp gene product is potentially a polar amino acid and opine binding component of an ATP-binding cassette type (ABC-type) transport system similar to those of Gram-negative bacteria. This membrane protein is likely lipid modified at its amino terminus and was present in five S. uberis strains and one Streptococcus parauberis strain examined.

Characterization of bovine adenovirus type 3 early region 2B

We have determined the nucleotide sequence of a 6999 base pair region of bovine adenovirus-3 covering map units 9.0 to 29.17, which contained the adenovirus homologs of IVa2 protein and the DNA replication proteins, precursor of terminal protein and DNA polymerase proteins. Analysis of the sequence for cis-acting elements suggests that transcripts of DNA polymerase and precursor of terminal protein are 3' co-terminal. In addition, this region also contains major late promoter sequence. The sequence to the left of IVa2 contains the ORF of pIX with a potential TATA box immediately upstream and two polyadenylation consensus signals immediately downstream of the ORF.

Inhibition of rotavirus infection in vitro and in vivo by a synthetic peptide from VP4

A synthetic peptide corresponding to bovine rotavirus C486 (BRV) VP4 amino acid sequence 232-255 (VP4-peptide) was studied with the objective of defining the origin of the protective immune response reported previously by Ijaz et al. (J. Virol. 1991, 65, 3106-3113). Pretreatment of MA-104 cells with the VP4-peptide before infection with rotavirus prevented both the attachment of 35S-labelled virus and plaque formation in vitro. In vivo studies using a murine rotavirus model demonstrated that intragastric administration of VP4-peptide protected subjects from challenge with virulent rotavirus. These results clearly indicate the importance of this epitope in virus-cell interactions and their potential as a rotavirus vaccine candidate.

Intradermal immunization with a bovine herpesvirus-1 DNA vaccine induces protective immunity in cattle

Although intramuscular (i.m.) injection of DNA encoding glycoprotein D (gD) of bovine herpesvirus-1 (BHV-1) induces immune responses in cattle, this route of delivery is inefficient. Here we assessed three parameters that may enhance the efficacy of a gD DNA vaccine in cattle. First, the immune response generated by i.m. injected plasmid expressing a secreted form of gD (tgD) was determined and found to be very similar in magnitude to the response induced by gD-expressing plasmid. Secondly, gD- and tgD-expressing plasmids were administered by intradermal (i.d.) immunization, which resulted in a superior immune response to the secreted form, but no improvement in the response to the membrane-associated form. However, the form of gD used for immunization did not influence the immunoglobulin subtype, the ratio of antigen-specific IgG1 to IgG2 being approximately 4:1. Finally, the effect of promoter strength was assessed by replacing the Rous sarcoma virus (RSV) promoter, which was used in the original experiments, with the human cytomegalovirus immediate early promoter and first intron A (HCMV/IA). Although upon transfection in vitro the HCMV/IA promoter appeared to be stronger than the RSV promoter, there was only a 2-fold higher antibody response in vivo upon i.d. injection of cattle. Protection against virus challenge was obtained in the calves immunized i.d. with tgD-encoding plasmid, as shown by a significant reduction in weight loss, virus excretion, temperature response and clinical disease. No significant protection was observed in the animals vaccinated i.d. with the gD-expressing plasmid, which correlates with the lower level of immunity pre-challenge.

Nucleotide sequence, genome organization, and transcription map of bovine adenovirus type 3

The complete DNA sequence of bovine adenovirus type 3 is reported here. The size of the genome is 34,446 bp in length with a G+C content of 54%. All the genes of the early and late regions are present in the expected locations of the genome. However, the late-region genes are organized into seven families, instead of five as they are in human adenovirus type 2. The deduced amino acid sequences of open reading frames (ORFs) in the late regions and early region 2 (E2) and for IVa2 show higher degrees of homology, whereas the predicted amino acid sequences of ORFs in the E1, E3, and E4 regions and the pIX, fiber, and 33,000-molecular-weight nonstructural proteins show little or no homology with the corresponding proteins of other adenoviruses. In addition, the penton base protein lacks the integrin binding motif, RGD, but has an LDV motif instead of an MDV motif. Interestingly, as in other animal adenoviruses, the virus-associated RNA genes appear to be absent from their usual location. Sequence analysis of cDNA clones representing the early- and late-region genes identified splice acceptor and splice donor sites, polyadenylation signals and polyadenylation sites, and tripartite leader sequences.

A neutralizing monoclonal antibody to bovine rotavirus VP8 neutralizes rotavirus infection without inhibiting virus attachment to MA-104 cells

VP8*, the N-terminal cleavage product of rotavirus VP4, contains the virus neutralizing epitopes in the hemagglutination domain. To map the neutralizing epitope, we developed monoclonal antibodies specific for VP4 of bovine rotavirus C486 (BRV). A neutralizing escape mutant was generated by one of these monoclonal antibodies (2E8) and a point mutation (Glu-->Asp) was found at aa 116 of VP8*. To investigate the effect of this mutation on the cellular binding and hemagglutination activities, the VP8* genes of the escape mutant and wild type (WT) virus were expressed in E. coli and their functional activities were compared. Both the escape mutant and WT virus VP8* showed hemagglutination and MA-104 cell binding activities. However, hemagglutination activity of the WT virus VP8* was inhibited by 2E8, but that of the escape mutant VP8* was not. These data indicate that the neutralizing epitope is located in the HA domain but is not critical for rotavirus attachment to MA-104 cells. To understand virus neutralization, radiolabelled BRV was incubated with 2E8 and the distribution of radioactivity in a CsCI density gradient was analysed as was the morphology of the virions in peak fractions. Interaction of 2E8 with rotavirus led to virus morphological changes with a concomitant shift in buoyant density. These data suggest that aa 116 influences the binding of 2E8 which in turn may alter virus integrity.

Characterization of the interaction between VP8 of bovine rotavirus C486 and cellular components on MA-104 cells and erythrocytes

Rotavirus VP8*, the N-terminal trypsin cleavage product of VP4, has been shown to bind to MA-104 cells and human O type erythrocytes. To examine whether bacterially expressed VP8* binds to cellular components of MA-104 cells, the VP8* (aa 1-247) was expressed in E. coli and radiolabelled with 35S-methionine. The radiolabelled rVP8* was immunoprecipitated with antiserum to bovine rotavirus C486 (BRV). The rVP8* was found to bind to MA-104 cells and its binding was competed by BRV. To study the interaction between VP8* and receptors of erythrocytes, hemagglutination (HA) and hemagglutination inhibition (HI) assays were carried out using solubilized rVP8*. rVP8* showed HA which could be inhibited by antiserum to BRV. This interaction was also inhibited by gangliosides, demonstrating a sialic acid dependent interaction. To study the contribution of the C-terminal region of VP8* to HA, a number of approaches were used. First, a peptide spanning aa 230-247 was synthesized and antisera was raised against the peptide to see whether it could inhibit HA of rVP8*. Second, a truncated form of VP8* (tVP8*: aa 1-229) was expressed to examine its hemagglutinating activity. Third, the dimerization of rVP8* and tVP8* was compared by Western-blotting following electrophoresis using native SDS-PAGE. The results indicated that antibody to aa 230-247 inhibits hemagglutination by preventing dimerization of VP8* which in turn allows the molecule to cause HA. To characterize the interaction between the HA domain and sialic acid receptors, erythrocytes were treated with sialidases of different specificities. Arthrobacter ureafaciens, Clostridium perfringens and alpha 2-8 linkage-specific neuraminidase destroyed the ability of sialic acid of erythrocytes to interact with rVP8*, indicating that bovine rotavirus C486 binding requires an alpha 2-8 linkage but acetylation of the sialic acid is not necessary.

Effect of IL-4 and IL-12 liposomal formulations on the induction of immune response to bovine herpesvirus type-1 glycoprotein D

Activation of different T-helper (Th) responses following immunisation has profound and specific influences on the development of the immune response and on the ability of a vaccine to confer protection. Since cytokines are capable of influencing the stimulation of distinct T-cell responses, their encapsulation in vaccines should modulate antigen-specific immune responses. Unfortunately, the use of cytokines in vivo is hampered by their rapid clearance and inactivation. One possible solution to this problem is the use of liposomes to entrap both cytokines and antigen. This approach will not only protect the cytokine but will also deliver the two components simultaneously to the same site. The authors examined, therefore, the immune responses elicited by systemic immunisation of mice with liposome formulations containing a truncated form of bovine herpesvirus type-1 glycoprotein D (tgD) together with IL-4 or IL-12. Subcutaneous immunisation with liposomes containing tgD and IL-12 significantly enhanced the induction of antigen-specific cellular and humoral immune responses. These responses were characterised by an increase in IFN-gamma secreting cells and the induction of tgD-specific IgG2a antibodies. In contrast, encapsulation of IL-4 into tgD-liposomes did not enhance the humoral immune response to gD but significantly influenced the development of antigen-specific IL-4 secreting cells. Our results indicated that encapsulation of IL-12 into the liposomes was necessary for the systemic adjuvant effect and demonstrated the feasibility of using liposome technology and cytokines to manipulate the development of different antigen-specific Th subsets in vivo.

Mucosal immunization with recombinant adenoviruses: induction of immunity and protection of cotton rats against respiratory bovine herpesvirus type 1 infection

To facilitate the evaluation of vaccines against bovine herpesvirus type 1 (BHV-1), a cotton rat model of intranasal (i.n.) BHV-1 infection was established. Cotton rat lung cells were similar to bovine cells in their ability to support BHV-1 replication in vitro. Furthermore, i.n. inoculation of cotton rats with BHV-1 resulted in pulmonary lesions comparable to BHV-1 infection in cattle. Using this model, the potential of i.n. and gastrointestinal (g.i.) immunization was examined with recombinant human adenoviruses expressing glycoprotein D (gD) of BHV-1 to induce protective immunity against BHV-1. The replication-competent virus (gD-dE3) was more efficient than the replication-defective virus (gD-dE1E3) in inducing gD-specific antibody in the serum and in the respiratory tract. Furthermore, i.n. immunization with gD-dE3 stimulated antigen-specific antibody-secreting cells in the lung 12 weeks following immunization. Protection against BHV-1 challenge correlated with gD-specific antibody levels such that i.n. immunization with gD-dE3 conferred complete protection, while g.i. immunization conferred only partial protection of the lungs of most animals against BHV-1 challenge. In comparison, immunization with gD-dE1E3 by either route resulted in only a partial reduction of BHV-1 titre in the respiratory tract. The results obtained demonstrate that mucosal immunization with replication-competent recombinant adenovirus expressing gD of BHV-1 can induce immunity and protection against BHV-1 challenge.

DNA immunization with a bovine rotavirus VP4 gene induces a Th1-like immune response in mice

Immunization with naked plasmid DNA effectively induces both humoral and cell-mediated immunity to vaccine antigens and can confer protection against numerous infectious diseases. To explore the potential use of DNA immunization to induce rotavirus-specific immune responses, we used plasmid DNA encoding the VP4 gene of bovine rotavirus (BRV). Intrasmuscular injection of the plasmid encoding the VP4 gene into C57BI/6 mice induced cell-mediated immunity as measured by cytokine production. Although DNA immunization did not induce a detectable BRV-specific antibody response, DNA-immunized animals were primed for antibody production and a cellular immune response. Following viral inoculation, the immunized animals displayed an enhanced number of BRV-specific antibody-secreting cells and cytotoxic activity. The immune response induced by DNA immunization alone or followed by viral inoculation was biased toward IFN-gamma production (Th1-like). CD4+ lymphocytes were the major source of IFN-gamma production in the spleen following DNA immunization. In contrast, a balanced cytokine production was observed in the spleens of animals receiving whole virus. These experiments showed that DNA immunization with a gene encoding the VP4 protein of BRV stimulated a Th1-like immune response in mice, and this bias in the immune response persisted following exposures to whole virus.

Study of immunogenicity and virulence of bovine herpesvirus 1 mutants deficient in the UL49 homolog, UL49.5 homolog and dUTPase genes in cattle

We previously reported that the bovine herpesvirus 1 (BHV 1) gene homologous to herpes simplex virus gene UL49 is dispensable; nevertheless, a mutant with the UL49 homolog (UL49 h) gene deletion exhibited significantly impaired growth in cell culture. To further evaluate the role of the UL49 h in virus infectivity in the natural host of BHV 1, the pathogenesis of the UL49 h negative mutant was studied in cattle. An additional mutant with a combined defect in UL49 h, UL49.5 h and dUTPase genes was also studied in parallel. We found that both mutants were avirulent in cattle inasmuch as intranasal (i.n.) administration of either mutants induced no apparent clinical disease, nor did animals receiving the mutants shed virus. Following i.n. inoculation with the mutants animals developed low levels of serum neutralizing (SN) antibodies, and were partially protected against wild-type BHV 1 challenge. Intramuscular immunizations with either mutant induced good SN titers, and moreover, they induced nearly complete protection against respiratory challenge with wild-type virus. The results from this study establish that BHV 1 UL49 h is an important virulence factor, and also suggest that deletion of the nonessential viral genes UL49 h, UL49.5 h and dUTPase may be useful in developing recombinant BHV 1 vaccines or BHV 1-based vaccine vectors.

Polynucleotide vaccines in animals: enhancing and modulating responses

We immunized cattle, the natural host for bovine herpesvirus 1 (BHV-1), with a polynucleotide vaccine encoding BHV-1 glycoprotein D. These cattle trials clearly indicate that large species can be immunized with polynucleotide vaccines. Recently, using a murine model, we demonstrated that: the cellular compartment to which the expressed antigen is delivered determines the type of immune response (type 1 or type 2), and that the magnitude and direction of the immune response can be modulated by coadministration of plasmid encoded cytokines and antigen. Finally, we demonstrated that immunization of mice with a polynucleotide vaccine encoding BHV-1 gD could circumvent preexisting passively transferred, gD specific, polyclonal antisera and lead to the development of an active immune response.

Functional analysis of the transmembrane anchor region of bovine herpesvirus 1 glycoprotein gB

In herpesviruses, homologues of glycoprotein B (gB) are essential membrane proteins which are involved in fusion. However, there is no clear evidence regarding the location of the fusogenic domain on gB. By using bovine herpesvirus 1 (BHV-1) as a model, we studied the relationship between the structure and the fusogenic activity of gB. This was achieved by expressing genes of different gB derivatives containing specific truncations at the end of segments 2 or 3 of the transmembrane region in Madin-Darby bovine kidney cells under the control of the bovine heat-shock protein hsp70A gene promoter. All expressed gB products were structurally similar to authentic gB. One truncated form of gB, gBt, which contains residues 1-763, was efficiently secreted. However, gBtM (residues 1-807), which includes the first two segments at the carboxyl terminus, showed unstable retention on the cell surface, whereas gBtMA (residues 1 829), which contains all three membrane-spanning segments, was mostly intracellularly retained with some unstable surface anchorage. Another truncated gB, gBtDAF, which has gB residues 1-763 (gBt) and a human decay-accelerating factor (DAF) carboxyl tail, was also expressed. The DAF fragment provided a signal for the addition of a glycosyl phosphatidylinositol-based membrane anchor, which could target the gBt chimeric protein on the cell membrane. Immunofluorescence staining and pulse-chase kinetic studies support the theory that gBtM, gBtMA, and gBtDAF are retained on nuclear and cellular membranes via different segments of the transmembrane region or the DAF fragment, respectively. For the cells expressing gBt or gBtM, no cell fusion was observed, whereas cells expressing gBtMA clearly showed fusion. However, in gBtDAF cells, the overexpression and cellular accumulation of recombinant gB products did not cause fusion either, which supports our contention that the fusion phenomenon in gBtMA cells is caused by the fusogenic activity of the expressed gBtMA. With the help of sequence analysis, our results indicate that segment 2 of the transmembrane anchor region might be a fusogenic domain, whereas the real anchor is segment 3.

Maternal immunization of pregnant cattle with recombinant VP8* protein of bovine rotavirus elicits neutralizing antibodies to multiple serotypes. Colostral neutralizing antibody by rotavirus VP8*

Neonatal calf diarrhoea caused by bovine rotavirus is one of the most common diseases in cattle. VP8 portion of the rotavirus VP4 protein is known to contain neutralizing epitopes and hemagglutination activity. We expressed the VP8* portion of bovine rotavirus strain C486 (G6P1 serotype) in E. coli, and examined potential of the recombinant VP8* protein for induction of neutralizing antibody responses in host animals. One hundred twenty pregnant beef cows were selected and immunized eight weeks prior to parturition with the recombinant VP8* protein. Colostral and milk samples were collected 12 hours and 10 days post-calving, respectively, and the virus neutralizing titers elicited by the recombinant subunit antigen were determined by plaque reduction assay. Colostral antibody titres of the vaccinated group were significantly higher than those of the unvaccinated control group, and these titers were equivalent to the titers elicited by a commercial vaccine. While titers of the control group rapidly decreased to 220 after 10 days of calving, neutralizing titers in the milk of the vaccinees remained 510. Rabbit and bovine antibodies induced by the recombinant VP8* protein were also able to neutralize bovine rotavirus P5 serotype (B641) at significant level and P11 serotype (B223) moderately. Our results suggest that the E. coli-produced recombinant VP8* protein can be an useful subunit vaccine candidate to prevent rotavirus infection in new-born calves.

Protective immunity in cattle following vaccination with conventional and marker bovine herpesvirus-1 (BHV1) vaccines

The efficacy of two experimental subunit gD vaccines and two commercial whole virus vaccines was determined in a bovine herpesvirus-1 (BHV1) challenge trial. Full-length gD and a truncated, secreted form of gD (tgD) were produced using a vaccinia virus expression system and purified by affinity chromatography. Comparison of these forms of gD did not reveal significant structural or antigenic differences. Calves immunized with gD or tgD in avridine developed significantly (P < 0.05) higher neutralizing antibody titers in the serum and nasal mucosa than animals vaccinated with killed virus (KV) or modified live virus (MLV). Following challenge with BHV1, all vaccinated calves had significantly (P < 0.05) lower rectal temperatures and clinical scores than those in the placebo group. In contrast to the KV-, MLV- and placebo-vaccinated calves, the gD and tgD-immunized animals experienced minimal weight loss and virus shedding post-challenge. Glycoprotein B-specific antibodies were detected in KV- and MLV-vaccinated calves, but not in gD- or tgD-immunized animals. These data suggest that full-length or truncated gD, when formulated in an appropriate adjuvant, is more effective than two KV and MLV vaccines and may be used as a marker vaccine for concurrent vaccination and eradication programs of BHV1.

Effects of BHV-1 on PMN adhesion to bovine lung endothelial cells

Bovine herpes virus-1 (BHV-1) infection appears to decrease the rate of polymorphonuclear leukocyte (PMN) influx into the lung in response to the secondary invader, Pasteurella haemolytica. It was postulated that BHV-1 may affect the rate of cellular infiltration by altering the function of the endothelium, thereby preventing PMN movement across the blood-tissue barrier. Therefore, we decided to investigate the effect of BHV-1 on the ability of PMN to adhere to lung endothelial cells (LEC). LEC were isolated from fetal bovine fetal tissue and were shown to function in PMN adhesion assays. Furthermore, enhanced PMN adhesion was observed after exposure of LEC to recombinant bovine TNF-alpha (rBoTNF-alpha) for 4, 8, 12, and 24 h. LEC infected with BHV-1 were shown to be less responsive to rBoTNF-alpha. However, infection of LEC with BHV-1 at an multiplicity of infection (MOI) of 1.0 or 10 did not affect basal levels of PMN adhesion to these cells. Decreased PMN binding to BHV-1-infected LEC, simultaneously treated with rBoTNF-alpha, was observed at 10-12 h post-infection. The data suggest that BHV-1 may prevent cytokine-induced PMN infiltration of the lung through the modification of EC responses to cytokines.

Immunology of bovine herpesvirus 1 infection

Immune responses to bovine herpesvirus 1 (BHV-1) have been studied following exposure of animals to virulent virus, conventional live or killed vaccines, genetically engineered live virus vaccines, subunit vaccines and, more recently, following immunization with plasmids encoding putative protective antigens. In all cases reported to date, exposure to BHV-1 or its glycoproteins induced specific responses to the virus which are capable of neutralizing virus and killing virus infected cells. These studies clearly indicate that the responses to BHV-1 are broad based, including both Th1 and Th2. In addition to inducing neutralizing antibodies, which can prevent virus attachment and penetration, these antibodies can also participate in antibody complement lysis of infected cells or in antibody dependent cell cytotoxicity. The virus also induces a myriad of specific cellular responses including the induction of cytokines, which either directly or indirectly inhibit virus replication by activation of effector cells. These activities have been associated with lymphocytes, NK-like cells, macrophages and polymorphonuclear neutrophils. These effector cells can kill virus infected cells either directly or by interacting with antibody to induce cell death by antibody dependent cell cytotoxicity. Killing of virus infected cells occurs after the expression of viral antigens on the cell surface of infected cells. Since the relationship between the time of cell killing and completion of virus assembly will influence whether the infectious cycle is aborted or results in productive viral replication any enhancement in viral killing will dramatically reduce the virus load. Based on these studies, many people conclude that antibody is critical in preventing infection and spread to susceptible contacts. In contrast, cell mediated immunity is involved in recovery from infection. However, none of these events occur in isolation in a body and a defect in one will dramatically influence the other. Furthermore, the relative importance of each effector mechanism will clearly depend on whether the animal is exposed to the virus for the first time (primary infection) or it is a secondary exposure following vaccination or infection with the field virus. Following a primary infection, where there is no antibody to interfere with the initial virus-cell interaction at the receptor level, the virus initiates an infection. These initial interactions are mediated primarily by the viral glycoproteins. Following the initial infection, viral protein synthesis induces a series of events which stimulate the nonspecific immune responses of the host. Therefore, the nonspecific immune responses (mediated primarily by viral products which induce early cytokines) are amongst the first line of defense in helping clear the infection both directly as well as indirectly by stimulating the specific immune response. The macrophage is instrumental in focusing the specific immune response by producing various cytokines and subsequently responding to cytokines produced by T-cells to kill to virus infected cells. This activity is detectable within 2 days after infection in lung parenchymal cells and 5-7 days in peripheral blood leukocytes. Interactions between various effector functions in limiting virus replication are described.

Effect of recombinant bovine interleukin-1 beta in normal calves and in calves infected with bovine herpesvirus type 1

Bovine herpesvirus-1 (BHV-1) is an important pathogen of respiratory infections in cattle. Its continuing importance lies in its ability to predispose infected hosts to bacterial infections. In this present study, we determined whether the immunoregulatory effects induced by interleukin-1 (IL-1) could stimulate appropriate host defense mechanisms to influence the course of BHV-1 infection in cattle. We first evaluated the effect of different doses (10-1000 ng/kg) of IL-1 in normal cattle. A single administration of IL-1 was able to induce a dose-dependent increase in polymorphonuclear (PMN) cells as well as monocytes in peripheral blood. The number of CD3+ lymphocytes and gamma/delta T cells in peripheral circulation decreased transiently in a dose-dependent manner. In the disease model, the effect of IL-1 administration (300 ng/kg) 24 h before, at the time of, and 24 h after the BHV-1 challenge was assessed. As a single therapeutic modality, IL-1 did not significantly reduce the establishment or progression of BHV-1-induced disease. Nevertheless, our results demonstrated that the significant modulation of diverse immune parameters did not exacerbate disease. Thus, the use of IL-1 as an adjunct therapy or as a vaccine adjuvant in cattle can be safely considered in situations where BHV-1 infection is likely to occur.

Novel viral vaccines for livestock

Recent advances in our understanding of virulence factors of viruses and the proteins or glycoproteins involved in inducing neutralizing antibodies or cell mediated immunity are forming the foundation for the development of a new generation of viral vaccines. Using bovine herpesvirus as an example, we have identified glycoproteins gB, gC, and gD as important targets for inducing neutralizing antibody responses, with gD being able to induce the highest neutralizing and cellular responses. For subunit vaccine development, the glycoproteins were produced in both prokaryotic and eukaryotic expression systems. Glycoproteins produced in eukaryotic systems were very effective in stimulating a broad range of immune responses in cattle. These glycoproteins were then formulated into effective vaccines that prevented both virus shedding and clinical disease. Herpesviruses also served as an excellent model for the identification and deletion of specific genes which lead to attenuation. In herpesviruses, two major classes of genes can be deleted. Class I includes glycoprotein genes that are nonessential for virus replication in vitro, and Class II includes genes involved in nucleic acid metabolism. these gene deleted regions can then be replaced with genes coding for protective antigens of other pathogens to develop multivalent vaccines in a single vector. Similar approaches are being used for other viruses including vaccinia virus and adenovirus. Finally, we introduced plasmids coding for protective antigens, gB, gC, and gD, into animals and developed immunity to these antigens. This approach has the potential to revolutionize vaccination regimes of the future.

Production and characterization of bovine herpesvirus 1 glycoprotein B ectodomain derivatives in an hsp70A gene promoter-based expression system

Different derivatives of bovine herpesvirus 1 (BHV-1) glycoprotein B (gB) ectodomain were expressed in a novel heat-shock expression system. The putative ectodomain, gBt, and the N-terminal subunit, gBb, were of the expected molecular weight and were secreted. Their production were heat-inducible and the purified proteins were able to elicit antibody responses in mice of a comparable level as induced by authentic gB. The truncated C-terminal subunit, gBct, was retained in the endoplasmic reticulum. Our studies suggest that the gBb subunit may play a major role in constituting the overall configuration of gB and is required for the intracellular transport of gB.

Induction of systemic and mucosal immune responses in cotton rats immunized with human adenovirus type 5 recombinants expressing the full and truncated forms of bovine herpesvirus type 1 glycoprotein gD

We generated both replication-incompetent (HAd5-gD-E1 and HAd5-tgD-E1) and replication-competent (HAd5-gD-E3 and HAd5-tgD-E3) human adenovirus type 5 (HAd5) recombinants expressing the full (gD) or truncated form (tgD) of the glycoprotein gD gene of bovine herpevirus type 1 (BHV-1). Recombinant gD and tgD expressed by HAd5-gD-E1 and HAd5-gD-E3 and by HAd5-tgD-E1 and HAd5-tgD-E3, respectively, were recognized by gD-specific monoclonal antibodies (MAbs) directed against linear and conformational epitopes, suggesting that antigenicity of recombinant gD and tgD was similar to that of the native gD expressed in BHV-1 infected cells. In HAd5-gD-E1- or HAd5-gD-E3-inoculated cotton rats there was a strong gD- and HAd5-specific IgG and IgA antibody response. The immune response was significantly lower in animals similarly immunized with HAd5-tgD-E1 or HAd5-tgD-E3, indicating that live adenovirus vaccine vectors may be better suited to the full-length form of glycoprotein gD than its truncated form. After a BHV-1 challenge, no infectious BHV-1 virions were isolated from the trachea of cotton rats previously immunized with HAd5-gD-E1 or HAd5-gD-E3. These results suggest that adenovirus E1 insertion (replication-incompetent) and E3 insertion (replication-competent) vectors have excellent potential for use in developing live recombinant virus vaccines and provide evidence that the cotton rat model can be used in BHV-1 vaccination-challenge trials.

The cytoplasmic domain of bovine herpesvirus 1 glycoprotein B is important for maintaining conformation and the high-affinity binding site of gB

Bovine herpesvirus 1 (BHV-1) glycoprotein B (gB) has been shown to interact with two types of receptor on Madin Darby bovine kidney cells. The first receptor is heparan sulfate proteoglycan, whereas the second high-affinity receptor remains unknown. In order to study the structural requirement for gB's high-affinity binding activity, different forms of the gB ectodomain were expressed and compared with authentic gB. By using chemical cross-linking and sucrose gradient centrifugation, we found that BHV-1 gB was able to form dimers. A region between the cleavage site and the transmembrane anchor region, residues 506 to 763, was found to be required for gB oligomerization. Although the purified gBt and gBtM, two truncated forms of gB, formed oligomers, they did not block the high-affinity cellular receptor, suggesting that oligomerization was not the reason for the loss of the high-affinity binding site on gB. However, an N-terminal juxtamembrane region-located epitope recognized by a monoclonal antibody, designated epitope I, was lost from gBt and gBtM, indicating that both truncated gBs are conformationally changed. Therefore, the structure around this particular region may be required for the existence of the gB high-affinity binding site.

Expression of bovine interleukin-1 beta in a bovine herpesvirus-1 vector: in vitro analysis

In order to evaluate whether bovine herpesvirus-1 (BHV-1) could be used as a live viral vector for the expression of cytokines, we constructed a recombinant BHV-1 expressing bovine interleukin-1 beta (boIL-1 beta). The boIL-1 beta coding sequence, corresponding to the cleaved mature product, was fused with the BHV-1 glycoprotein C (gC) signal peptide sequence; the resultant gC-boIL-1 beta fusion gene was recombined into the gC locus of the BHV-1 genome. Southern blot analysis confirmed the proper genomic configuration of the recombinant virus. Results from transcript analysis showed that boIL-1 beta was expressed in infected cells with kinetics similar to that of gC. Indirect immunofluorescence and immunoprecipitation assays showed that the recombinant protein was produced in both cell-associated and secreted forms. Western blot analysis detected a 19.3-kDa protein. Further analysis, using an IL-1 beta bioassay demonstrated that both the cellular and secreted forms of recombinant boIL-1 beta possessed biological activity. The expression of the boIL-1 beta protein did not affect the in vitro growth efficiency of the virus, which exhibited similar growth kinetics to that of a simple gC deletion mutant. The results from this study demonstrate that BHV-1 can be used to express a functional cytokine, thereby establishing the basis to further study recombinant BHV-1 expressing cytokines as an alternative means to attenuate the virus and also as a potential in situ cytokine delivery system to modulate immune responses against BHV-1 and other cattle pathogens.

Comparisons of the F and HN gene sequences of different strains of bovine parainfluenza virus type 3: relationship to phenotype and pathogenicity

The genes for the F and HN glycoprotein of a pathogenic field isolate of bovine parainfluenza virus type 3 (BPIV3) were isolated, converted to cDNA, and sequenced using dideoxynucleotides. The resulting nucleotide sequences were converted to protein sequence and were compared to previously sequenced glycoprotein genes with amino acid differences in the glycoproteins of isolates expressing different phenotypes. The HN glycoprotein, involved in the attachment and release of the virus, and the F glycoprotein, involved in penetration and spread of the virus, have been shown to affect pathogenicity of the virus and are the immunodominant proteins of the virus. Both the F and HN proteins have been shown to be required for syncytium formation. Our results suggest that BPIV3 viruses that exhibit greater syncytium-inducing activity in vitro have greater pathogenicity in vivo. By determining which epitopes are involved in syncytium formation and comparing the sequences and enzymatic activities of different strains of virus, it may be possible to design subunit vaccines that protect against disease.

Glycoprotein H (gII/gp108) and glycoprotein L form a functional complex which plays a role in penetration, but not in attachment, of bovine herpesvirus 1

The glycoproteins of bovine herpesvirus 1 (BHV-1) play important roles in the interactions between virions and target cells. A 108 kDa glycoprotein, designated gII or gp 108, has been identified by two different panels of monoclonal antibodies. The gII- and gp 108-specific monoclonal antibodies were shown to react with the same protein, which was identified by N-terminal sequencing as the homologue of herpes simplex virus type 1 (HSV-1) gH. When BHV-1 gH was purified by immunoadsorbent chromatography, gL was co-purified. The gH-gL complex induced the production of antibodies that neutralized virus infectivity and inhibited virus penetration. Affinity-purified gH-gL did prevent penetration, but not attachment of BHV-1, which suggests that the gH-gL complex is essential for penetration of BHV-1 into susceptible cells.

Serum haptoglobin as an indicator of the acute phase response in bovine respiratory disease

The early stages of the host response to infectious agents include a number of physiologic changes, collectively known as the acute phase response. The acute phase response is comprised of reactions localized at the site of infection, as well as the initiation of systemic responses, which include a rapid increase in the serum concentration of some proteins, known as acute phase proteins (APP). Using polyacrylamide gel electrophoresis, we detected two APP of approximately 22 and 37 kDa molecular weight in sera obtained from cattle with bovine respiratory disease (BRD). Based on their presence in the sera of sick, but not normal animals, the molecular weights, N-terminal amino acid sequence analysis, and the ability to bind hemoglobin, we identified these proteins as the alpha and beta subunits of haptoglobin. The haptoglobin molecule and the alpha subunit were isolated from serum, purified, and used to produce monoclonal and polyclonal antibodies. With these reagents, an enzyme linked immunosorbent assay was developed to measure the concentration of haptoglobin in bovine serum. Using an experimental model of BRD induced by a sequential challenge of calves with bovine herpesvirus type-1 and Pasteurella haemolytica, we observed a temporal relationship between the increase in haptoglobin concentration in serum and the onset of bacterial infection. The haptoglobin concentration ranged from undetectable in the serum of most calves prior to challenge, to greater than 1 mg ml(-1) in over one-third of the calves at the height of disease. Furthermore, the concentration of haptoglobin was associated significantly with other measures of the severity of disease. Together, these results indicate that quantification of acute phase proteins in animals with BRD could be a valuable diagnostic and prognostic aid.

Cloning, sequencing and expression of the CAMP factor gene of Streptococcus uberis

The gene coding for the CAMP factor from a strain of Streptococcus uberis (ATCC 9927) was cloned in Escherichia coli. Chromosomal DNA from Streptococcus uberis was used to construct a gene library in plasmid pTZ18R and six CAMP-reaction positive clones were obtained from a total of 10,000 transformants. One clone, pJLD21, was subcloned and the CAMP factor gene was located in a 3.2 kb BamHI fragment. The nucleotide sequence of Streptococcus uberis CAMP factor gene was determined and the deduced amino acid sequence is highly homologous to the corresponding Streptococcus agalactiae protein. Immunoblot analysis revealed that the recombinant strain pJLD21 expressed a protein with a molecular weight of 28 000. Antibodies raised against purified Streptococcus uberis CAMP factor cross-reacted with Streptococcus agalactiae protein B.

Identification and characterization of a bovine herpesvirus-1 (BHV-1) glycoprotein gL which is required for proper antigenicity, processing, and transport of BHV-1 glycoprotein gH

DNA sequence analysis of the bovine herpesvirus-1 (BHV-1) genome revealed the presence of an open reading frame named UL1 which exhibited limited homology to glycoprotein gL of herpes simplex virus-1 (S. K. Khattar, S. van Drunen Littel-van den Hurk, L. A. Babiuk, and S. K. Tikoo, Virology 213, 28-37). To identify the BHV-1 UL1 protein, rabbit antisera were prepared against two synthetic peptides that were predicted by computer analysis to encompass antigenic epitopes. Sera against both peptides immunoprecipitated a 16- to 17-kDa protein from in vitro translated in vitro transcribed mRNA, BHV-1-infected MDBK cells, and purified virions. Enzymatic deglycosylation and lectin binding assays confirmed that the BHV-1 UL1 protein contains only O-linked oligosaccharides and was named glycoprotein gL. Sera against UL22 protein immunoprecipitated a protein of 108 kDa from BHV-1-infected MDBK cells and purified virions, which was modified only by N-linked oligosaccharides and was named glycoprotein gH. Glycoprotein gL expressed by recombinant vaccinia virus was properly processed and secreted into the medium. In contrast glycoprotein gH expressed by recombinant vaccinia virus was found to be retained in the rough endoplasmic reticulum. However, gH coexpressed with gL by recombinant vaccinia viruses was properly processed and transported to the cell surface, suggesting that complex formation between gH and gL is necessary for the proper processing and transport of gH but not gL. In addition gH--gL complex formation is also required for induction of neutralizing antibody response and anchoring of gL to the plasma membrane.

Molecular cloning and expression of bovine interleukin-8

Interleukin-8 (IL-8) is a neutrophil and T-lymphocyte chemotactic and activating factor. This cytokine is produced by many cell types including macrophages in response to a variety of microbial and non-microbial agents. In the present study, we determined the nucleotide sequence for bovine IL-8 cDNA. The amino acid sequence encoded by this cDNA shares 76 and 87% homology with the human and swine IL-8 proteins, respectively. Bovine IL-8 cDNA was expressed in Escherichia coli as a beta-galactosidase fusion protein. Western blotting demonstrates that this fusion protein, but not beta-galactosidase cross-reacts with monospecific anti-human IL-8 antiserum. We also studied the induction of IL-8 mRNA synthesis in bovine alveolar macrophages (BAM) stimulated with heat-killed Pasteurella haemolytica. IL-8 mRNA was induced in BAM as early as 1 h and was detectable at high levels 12 h post-stimulation with P. haemolytica. A dose titration of P. haemolytica and E. coli endotoxins showed that a relatively low level of P. haemolytica endotoxin induced high levels of bovine IL-8 mRNA. The significance of these findings in the pathogenesis of bovine pneumonia caused by P. haemolytica is discussed.

Glycoprotein Bb, the N-terminal subunit of bovine herpesvirus 1 gB, can bind to heparan sulfate on the surfaces of Madin-Darby bovine kidney cells

The present study confirms our previous findings made by using heparin affinity chromatography that bovine herpesvirus 1 gB can bind to heparin-like structures. In order to locate the functional domain for heparin binding, we expressed the extracellular portion of gB (gBt) and the large subunit of gB (gBb) in Madin Darby bovine kidney (MDBK) cells under the control of the bovine heat shock protein 70A gene promoter. The recombinant gBt and gBb were both efficiently secreted from the transfected cells. They were shown to have structural and antigenic properties similar to those of authentic gB. Like authentic gB, both gBt and gBb were able to bind heparin-Sepharose as well as heparan sulfates on MDBK cells. Thus, we suggest that at least one heparin-binding domain is localized in gBb, the N-terminal portion of gB, which agrees with the presence of clusters of prolines and basic residues, thought to be essential for heparin binding.

Bovine herpesvirus 1 UL49.5 homolog gene encodes a novel viral envelope protein that forms a disulfide-linked complex with a second virion structural protein

We previously reported that the genome of bovine herpesvirus 1 (BHV-1) contains an open reading frame (ORF) homologous to the herpes simplex virus UL49.5 ORF, and as with the herpes simplex virus UL49.5 ORF, the deduced amino acid sequence of the BHV-1 UL49.5 homolog (UL49.5h) contains features characteristic of an integral membrane protein, implying that it may constitute a functional gene encoding a novel viral envelope protein. This communication reports on the identification of the BHV-1 UL49.5h gene product. By employing an antibody against a synthetic BHV-1 UL49.5h peptide and an UL49.5h gene deletion mutant, the primary product of BHV-UL49.5h gene was identified as a polypeptide with a size of approximately 9 kDa; in both infected cells and isolated virions, the UL49.5h products were found to exist in three forms; monomer, disulfide-linked homodimer, and disulfide-linked heterodimer containing a second viral protein with a size of about 39 kDa. O-Glycosidase digestion and [3H]glucosamine labelling experiments showed that the UL49.5h protein is not glycosylated. Although the deduced amino acid sequence contains putative sites for myristylation and phosphorylation, we were unable to detect either modification. Surface labelling and trypsin digestion protection experiments showed that the BHV-1 UL49.5h protein was present on the surface of infected cells and on the surface of mature virions. Nonionic detergent partition of isolated virions revealed that the UL49.5h protein is more tightly associated with the virion tegument-nucleocapsid structure than envelope protein gD. The results from this study demonstrate that the BHV-1 UL49.5h gene encodes a nonglycosylated virion envelope protein which may associate with virion internal structures by forming a complex with the 39-kDa virion structural protein.

Sequence and expression of a bovine herpesvirus-1 gene homologous to the glycoprotein K-encoding gene of herpes simplex virus-1

In the bovine herpes virus-1 (BHV-1) genome, a gene equivalent to the glycoprotein k (gK)-encoding gene of other herpesviruses was identified and sequenced. The primary translation product is predicted to comprise 338 amino acids (aa) and to exhibit a molecular mass of 37.5 kDa. It possesses characteristics typical for membrane glycoproteins including a potential cleavable signal sequence, three transmembrane domains and two potential N-linked glycosylation sites. Comparison to the gK proteins of the other herpesviruses revealed aa sequence homologies of 46, 44, 53, 43, and 46% with the gK counterparts of herpes simplex viruses-1 and 2 (HSV-1 and 2), equine herpesvirus-1 (EHV-1), Marek's disease virus (MDV) and varicella zoster virus (VZV), respectively. A 30-kDa primary translation product was identified following in vitro translation of in vitro transcribed mRNA. When canine microsomal membranes were added to the translation reaction, a 38-kDa glycosylated protein was detected. Treatment with endoglycosidase F or H (endo or H) removed the glycosyl groups and reduced the apparent molecular mass of the 38-kDa glycoprotein.

Immunogenicity of bovine herpesvirus 1 glycoprotein D in mice: effect of antigen form on the induction of cellular and humoral immune responses

For the development of veterinary subunit vaccines, modifications to the antigen may be needed to make the production of these vaccines cost effective. To investigate the effect of antigen modifications on immune response, we used glycoprotein D, one of the major glycoproteins of bovine herpesvirus-1 (BHV-1), as a model antigen. We developed a mouse model to assess the immune response elicited by immunization with either a recombinant truncated (tgD) or the authentic full-length (gD) form of BHV-1 gD in VSA3, a novel water-in-oil adjuvant. Both forms of BHV-1 gD antigen induced good levels of cell-mediated immunity, as evaluated by antigen-specific proliferative response and cytokine (IFN-gamma and IL-4) production. Following primary immunization, the humoral immune response induced by gD was superior to that elicited by vaccination with tgD. However, after a secondary immunization, a strong and similar antibody response to BHV-1 gD was induced by both forms of the antigen. The difference in immunogenicity between gD and tgD after primary immunization was not due to the loss of immunogenic epitopes in the truncated antigen or the ability to associate with the adjuvant VSA3. Our results indicate that both gD and tgD are capable of efficiently inducing a cell-mediated immune response, and although recombinant tgD is less efficient in inducing a primary humoral immune response when compared to the full-length gD, tgD effectively primed for a secondary antibody response.

Pathology and immunogenicity in the cotton rat (Sigmodon hispidus) model after infection with a bovine adenovirus type 3 recombinant virus expressing the firefly luciferase gene

The histopathology of adenovirus pneumonia in cotton rats (Sigmodon hispidus) due to bovine adenovirus type 3-luciferase recombinant virus (BAd3-Luc), which has a 0.7 kb deletion from the early region 3 (E3) replaced with the firefly luciferase gene, was compared with that produced by the parental wild-type (wt) bovine adenovirus type 3 (BAd3). After intranasal inoculation of cotton rats with 3 x 10(7) p.f.u. of BAd3-Luc, the infectious virus titres in the lungs at various times post-infection were similar to those of animals infected with the parental virus. Quantitative analysis of histopathological changes and immunohistochemical staining showed that the character and severity of the lesions were indistinguishable in the two infections. Luciferase activity was detected in the lungs of BAd3-Luc-inoculated animals until 4 days post-infection (p.i.). Antibodies to both BAd3 and luciferase were detected in sera collected from BAd3-Luc-infected animals until at least 6 weeks p.i. These results show that Bad3-Luc produces pulmonary lesions in cotton rats similar to those of wt BAd3 and suggest that BAd3-based vectors may be suitable for the development of live recombinant virus vaccines.

Antiviral screening of British Columbian medicinal plants

One hundred methanolic plant extracts were screened for antiviral activity against seven viruses. Twelve extracts were found to have antiviral activity at the non-cytotoxic concentrations tested. The extracts of Rosa nutkana and Amelanchier alnifolia, both members of the Rosaceae, were very active against an enteric coronavirus. A root extract of another member of the Rosaceae, Potentilla arguta, completely inhibited respiratory syncytial virus. A Sambucus racemosa branch tip extract was also very active against respiratory syncytial virus while the inner bark extract of Oplopanax horridus partially inhibited this virus. An extract of Ipomopsis aggregata demonstrated very good activity against parainfluenza virus type 3. A Lomatium dissectum root extract completely inhibited the cytopathic effects of rotavirus. In addition to these, extracts prepared from the following plants exhibited antiviral activity against herpesvirus type 1: Cardamine angulata, Conocephalum conicum, Lysichiton americanum, Polypodium glycyrrhiza and Verbascum thapsus.

Pathogenesis and immunogenicity of bovine adenovirus type 3 in cotton rats (Sigmodon hispidus)

Intranasal inoculation of cotton rats (Sigmodon hispidus) with 10(8) PFU of bovine adenovirus type 3 (BAd3) resulted in limited virus replication in the lung and trachea. Histopathological changes in the lungs were characterized by necrosis and hyperplasia of bronchiolar epithelium, eosinophilic intranuclear inclusions, pneumocyte type II hyperplasia in the alveoli, and mild peribronchiolar and perivascular lymphocytic infiltration. Immunohistochemically, viral antigens were observed more frequently in bronchiolar epithelial cells than in alveolar cells in cotton rat lung sections stained using a rabbit anti-BAd3 serum. Bronchiolar epithelial changes, intranuclear inclusion bodies, type II pneumocyte proliferation, peribronchiolar infiltration, and immunohistological staining were maximum at Day 3 or Day 4 postinoculation, whereas perivascular infiltration was first observed at Day 8 postinoculation. In addition to the histological study of the pathogenesis of BAd3 infection, we monitored the BAd3-specific immune response in cotton rats. Anti-BAd3 IgG and virus neutralizing antibodies were detected in sera, whereas anti-BAd3 IgA antibodies were found in the sera, lung, and nasal washes. Our results suggest that the cotton rat can serve as a useful small-animal model for investigating the pathogenesis of BAd3 infection, as well as immune responses to BAd3 recombinant virus vaccines.

Identification and transcriptional analysis of a 3'-coterminal gene cluster containing UL1, UL2, UL3, and UL3.5 open reading frames of bovine herpesvirus-1

We have identified and sequenced 3113 nucleotides located at the right end of the HindIII L fragment of the bovine herpesvirus-1 genome from map units 0.712 to 0.734. Analysis of the sequence identified four open reading frames (ORFs) which are designated UL1, UL2, UL3, and UL3.5 based on their homology with proteins of herpes simplex virus-1 (HSV-1), pseudorabies virus (PRV), equine herpesvirus-1, and varicella-zoster virus. The UL1 ORF of 158 amino acids exhibits limited homology with UL1 (glycoprotein gL) of HSV-1 (27%) and PRV (21%). The UL2 ORF of 204 amino acids shows significant homology to UL2 (uracil-DNA glycosylase) of HSV-1 (68%) and PRV (75%). The UL3 ORF of 204 amino acids shows significant homology to UL3 (nuclear phosphoprotein) of HSV-1 (62%) and PRV (53%). The UL3.5 ORF of 126 amino acids shows limited homology to the UL3.5 ORF of PRV (31%). The homolog of this gene is absent in HSV-1. Nucleotide sequence analyses also revealed potential TATA boxes located upstream of each ORF. However, only one polyadenylation signal was detected downstream of the UL3.5 ORF. Northern (RNA) blot analyses revealed four transcripts of 2.4, 1.9, 1.3, and 0.7 kb, which are transcribed in the same direction and are 3'-coterminal transcripts. These mRNAs appear to yield proteins encoded by UL1 (2.4 kb), UL2 (1.9 kb), UL3 (1.3 kb), and UL3.5 (0.7 kb) ORFs.

Regulation of bovine acute phase responses by recombinant interleukin-1 beta

The acute phase response is a collection of physiologic changes initiated early in the inflammatory process. This response is comprised of both localized changes at the site of infection or injury and the initiation of systemic responses, such as the increase in production of acute phase proteins. Cytokines such as interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF) play key roles in the regulation of acute phase response in the species studied to date. To better characterize the acute phase response of cattle, recombinant bovine (rBo). IL-1 beta was administered to cattle. A single administration of rBoIL-1 beta was able to induce a dose dependent increase in body temperature, circulating leukocytes, and serum haptoglobin and fibrinogen concentrations, as well as a decrease in plasma zinc concentration. Five daily administrations of rBoIL-1 beta resulted in heightened and prolonged elevations of haptoglobin and fibrinogen. In addition, alpha 1-acid glycoprotein levels were increased, a response not seen after a single administration of rBoIL-1 beta. These results indicate that IL-1 is an important regulator of the acute phase response in cattle.

Immunological response to recombinant VP8* subunit protein of bovine roravirus in pregnant cattle

Bovine rotavirus VP8*, N-terminal trypsin cleavage product of VP4, was produced in Escherichia coli. To examine if this antigen could induce neutralizing antibody responses, different species of animals were immunized with the recombinant VP8* protein. The VP8* antigen was found to stimulate a neutralizing immune response in rabbits. When VP8*-immunized mice were exposed to bovine rotavirus strain C486, significantly higher antibody responses were observed than if they were only exposed to C486. To stimulate a current vaccination protocol in the field with livestock, mice were exposed to live C486 virus first and then to VP8*. These mice had the elevated immune responses indicating that VP8* could boost immunity in primed mice. The immune response to VP8* was also tested in pregnant cows. The efficacy of VP8* in stimulating milk antibody was compared with a commercial inactivated vaccine. Differences in colostral antibody titres between VP8*-vaccinated and unvaccinated cows were statistically significant (P < 0.05) and equivalent to the commercial vaccine (P = 0.0569). The milk antibody titres on day 10 were comparable between VP8*- and commercial vaccine-vaccinated animals and were significantly higher (P < 0.05) than in unvaccinated controls. Furthermore, rabbit and bovine antibodies induced by VP8* were able to neutralize different P types of bovine rotaviruses to varying degrees, suggesting that serotype-specific and cross-reactive epitope(s) are present on the VP8* protein of rotavirus. Taken together, E. coli-expressed VP8* may be useful as a subunit vaccine candidate for bovine rotavirus.

Induction of mucosal immunity in cotton rats to haemagglutinin-esterase glycoprotein of bovine coronavirus by recombinant adenovirus

An effective vaccine against enteric bovine coronavirus (BCV) must be able to induce mucosal immunity. We recently described the construction of recombinant human adenovirus type 5 (hAd5) carrying the BCV haemagglutinin-esterase (HE) gene in the early transcription region 3 of the adenovirus genome. In this study, we examined the induction of systemic and mucosal immune responses to the hAd5 vector carrying the BCV HE gene (AdBcHE) following intranasal or enteric immunization of cotton rats. Regardless of the route of administration, mucosal immunization with AdBcHE induced significant levels of anti-HE IgG antibodies in serum. In addition, following intranasal immunization with AdBcHE, significant levels of anti-HE IgA antibodies were found in lung washes of immunized cotton rats. Furthermore, the specific anti-HE antibodies in sera and mucosal secretions efficiently neutralized BCV infectivity in vitro. T-cell proliferation and cell-mediated cytotoxic responses against the BCV HE were elicited in the spleen of intranasally immunized animals. The results demonstrate that mucosal immunization with AdBcHE is capable of inducing both systemic and mucosal immunity to the BCV HE. These immune responses may be important in protecting animals from BCV infection.

Characterization of cell-binding properties of bovine herpesvirus 1 glycoproteins B, C, and D: identification of a dual cell-binding function of gB

Previous studies have suggested that the attachment of bovine herpesvirus 1 (BHV-1) to permissive cells is mediated by its major glycoproteins B (gB), C (gC), and D (gD). In order to gain further insight into the mechanism of the BHV-1 attachment process, we purified authentic gB, gC, and gD from BHV-1-infected cells and membrane anchor-truncated, soluble gB, gC, and gD from stably transfected cell lines by affinity chromatography and examined their cell-binding properties on Madin-Darby bovine kidney cells. All of the glycoproteins tested exhibited saturable binding to Madin-Darby bovine kidney cells. All of the glycoproteins tested exhibited saturable binding to Madin-Darby bovine kidney cells. Addition of exogenous heparin or treatment of cells with heparinase to remove cellular heparan sulfate (HS) prevented both gC and gB from binding to cells but had no effect on gD binding. An assessment of competition between gB, gC, and gD for cell binding revealed that gC was able to inhibit gB binding, whereas other combinations showed no effect. Cell-bound gC could be dissociated by heparin or heparinase treatment. The response of bound gB to heparin and heparinase treatments differed for the authentic and soluble forms; while soluble gB was susceptible to the treatment, a significant portion of cell-bound authentic gB was resistant to the treatment. Binding affinity analysis showed that soluble gB and both forms of gC and gD each had single binding kinetics with comparable dissociation constants (Kds), ranging from 1.5 x 10(-7) to 5.1 x 10(-7) M, whereas authentic gB exhibited dual binding kinetics with Kd1 = 5.2 x 10(-7) M and Kd2 = 4.1 x 10(-9) M. These results demonstrate that BHV-1 gC binds only to cellular HS, gD binds to a non-HS component, and gB initially binds to HS and then binds with high affinity to a non-HS receptor. Furthermore, we found that while authentic gB was able to inhibit viral plaque formation, soluble gB, which retains the HS-binding property but lacks the high-affinity binding property, was defective in this respect. These results suggest that the interaction between gB and its high-affinity receptor may play a critical role in the virus entry process.

Recombinant type 5 adenoviruses expressing bovine parainfluenza virus type 3 glycoproteins protect Sigmodon hispidus cotton rats from bovine parainfluenza virus type 3 infection

Cotton rats were used to study the replication and pathogenesis of bovine parainfluenza virus type 3 (bPIV3) and to test the efficacy of the F and HN glycoproteins in modulating infection. In vitro cultures of cotton rat lung cells supported the growth of bPIV3 as shown by virus recovery, immunofluorescence, immunoprecipitation, and syncytium induction. Intranasal (i.n.) inoculation of cotton rats with 10(7) PFU resulted in peak recovery of virus after 2 days (8 x 10(4) PFU/g of lung tissue) and significant bronchiolitis with lymphocyte infiltration 5 to 7 days postinfection. Immunohistochemical staining of lungs and trachea demonstrated that virus antigen-positive cells increased in frequency over the course of infection to a maximum on day 5. Serum antibody responses were evaluated by enzyme-linked immunosorbent assays (ELISA), hemagglutination inhibition (HAI), and serum neutralization (SN). Following a single i.n. inoculation, serum antibody levels were 1/40,960, 1/32, and 1/80, as detected by ELISA, HAI, and SN, respectively. When an intramuscular inoculation of 10(7) PFU was administered 10 days prior to the i.n. inoculation, a secondary response which resulted in an ELISA titer of 1/163,000, an HAI titer of 1/640, and an SN titer of 1/512 was induced. IN inoculation of recombinant adenoviruses type 5 containing the bPIV3 F or HN protein or a combination of the two viruses protected cotton rats from bPIV3 challenge. Protection was evaluated serologically by ELISA, HAI, and SN titers, histopathology, immunohistochemistry, and virus recovery.

Characterization of a synthetic peptide mimicking trypsin-cleavage site of rotavirus VP4

A synthetic peptide corresponding to the trypsin cleavage site on the 84 k protein of bovine rotavirus was synthesized (VP4-peptide). This synthetic peptide could be cleaved by trypsin and therefore possessed the enzyme binding site present on the authentic protein. Further proof that this peptide mimicks the authentic trypsin cleavage site was the specific reaction of anti-peptide serum with the 84 k protein. The reaction of anti-peptide serum with infectious virus neutralized infectivity thereby supporting the biological importance of this site. Another interesting characteristic of this peptide was its ability to bind to the nucleocapsid protein resulting in a laddering effect on the nucleocapsid monomer (45 k), dimer (90 k) and trimer (135 k) [Gorzilia et al., J. Gen. Virol. 66, 1889-1900 (1985); Sabara et al., J. Virol. 53, 58-66 (1985); Sabara et al., J. Gen. Virol. 67, 201-212 (1986)]. Definitive proof of binding was provided by the fact that the increments in the ladder corresponded to the molecular weight of the synthetic peptide and that anti-peptide serum specifically reacted with the ladder formations. The laddering of the nucleocapsid could be eliminated by incubation with trypsin thus further supporting the formation of a synthetic peptide-nucleocapsid complex. Due to the ability of the peptide to bind to trypsin and to the nucleocapsid protein its biological activity was investigated. It appeared that increasing concentrations of the peptide reduced the rate of virus plaque formation, thereby suggesting that virus replication was inhibited. These results illustrate two features of this synthetic peptide which warrant further investigation; (1) its capacity to mimic an enzyme cleavage site and, (2) its ability to complex tightly to another protein. In protection-challenge experiments performed using a murine model, animals immunized with VP4-peptide provided protection passively, to neonates suckling on the immune dams, against a virulent rotavirus. The potential applications of this peptide in rotavirus diagnosis, therapy and synthetic peptides based vaccine is discussed.

Characterization of bovine herpesvirus 1 UL49 homolog gene and product: bovine herpesvirus 1 UL49 homolog is dispensable for virus growth

The sequence of the bovine herpesvirus 1 (BHV-1) gene that is homologous to the herpes simplex virus UL49 gene was determined. The BHV-1 UL49 homolog open reading frame consists of 774 bp and is capable of encoding 258 amino acids. Northern (RNA) blot analysis showed that the BHV-1 UL49 homolog is transcribed into a 1.1-kb RNA which is coterminal with the transcripts of an upstream UL49.5 homolog gene. Rabbit antisera produced against synthetic peptides of the predicted UL49 homolog gene product recognized a polypeptide of 33 to 35 kDa in both virus-infected cells and isolated virions. Further analysis by unionic-detergent partition of isolated virions suggested that the UL49 homolog gene product is a virion tegument protein. Indirect immunofluorescence assay revealed that the UL49 homolog gene product was predominantly localized in the nuclei of BHV-1-infected cells. A mutant virus with the UL49 homolog gene deleted was produced, and it was able to replicate in noncomplementing cells. Nevertheless, the yield of mutant virus was significantly reduced. The results from this study suggest that the BHV-1 UL49 homolog gene encodes a nuclear protein which constitutes a tegument component in mature virions and that it is dispensable for virus growth in cell culture.

Effect of recombinant bovine interleukin-1 beta on viral/bacterial pneumonia in cattle

Bovine herpesvirus-1 (BHV-1) is an important pathogen of respiratory infections in cattle. Its continuing importance lies in its ability to predispose infected hosts to bacterial infections (e.g., Pasteurella haemolytica). In this study we determined whether the immunoregulatory effects induced by recombinant bovine interleukin-1 (rbIL-1) could stimulate appropriate host defense mechanisms to influence the course of BHV-1 and P. haemolytica infection in cattle. We first evaluated the effect of multiple doses (5 doses of 300 ng/kg) of rbIL-1 in normal cattle. An increase in polymorphonuclear (PMN) cells, as well as monocytes, in peripheral blood was observed during the course of IL-1 administration. In addition, the phagocytic activity of monocytes was increased. Although the phagocytic and oxidative burst activities in PMN decreased during the course of rbIL-1 treatment, no changes were observed in the bactericidal capacity of these cells. Lymphocyte numbers in peripheral blood remained unchanged; however, the functional activity of these cells, as measured by IFN-gamma production upon in vitro stimulation, was decreased. In the bovine respiratory disease model, multiple administration of IL-1 did not influence significantly the progression of BHV-1/P. haemolytica infection in cattle. Thus, our results demonstrated that IL-1, although not therapeutically effective, could be administered safely as an adjuvant, even during the course of BHV-1/P. haemolytica infection.

Delineation of the essential function of bovine herpesvirus 1 gD: an indication for the modulatory role of gD in virus entry

The entry process of alphaherpesviruses consists of two steps, initial virus attachment and subsequent virus penetration involving membrane fusion. Glycoprotein D (gD) of the alphaherpesvirus bovine herpesvirus 1 (BHV 1) is an essential envelope protein, and it has been previously documented that gD plays a significant part in both of the virus entry steps. In order to gain further insight into the virus entry process, we attempted to define the essential function of BHV 1 gD. We replaced the gD transmembrane and cytoplasmic domains with a lipid-addition signal sequence from human decay accelerating factor and produced a stably transfected Madin Darby bovine kidney (MDBK) cell line that expresses a nonfusogenic, glycosylphosphatidylinositol (GPI)-anchored gD. We found that this cell line was able to support the growth of a gD gene-deletion mutant; the resultant gD mutant progeny contained the GPI-anchored gD on its virions and was able to enter into and produce a production infection in MDBK cells. This result suggests that fusion activity does not constitute the essential function of gD. In addition, we found that a gD-null virus (a virus containing no gD on its virion) could infect gD-expressing cells, but not normal MDBK cells. The ability of the gD-null virus to infect gD-expressing cells was dependent on the gD present on the cell surface, since either treating cells with phosphatidylinositol-specific phospholipase C to remove the GPI-anchored gD or incubating cells with gD monoclonal antibodies could block gD-null virus infection. This demonstrates that gD present on the cell surface can act in trans to facilitate the entry of virion lacking gD. This indicates that essential gD function can take place in the absence of gD-mediated virus attachment and membrane fusion. We also found that the gD monoclonal antibodies that block gD-null virus entry into gD-expressing cells are strictly restricted to the monoclonal antibodies that show postadsorption neutralization activity, indicating that the trans-acting function exhibited by the gD present on the cell surface represents the same function as defined by postadsorption antibody neurtralization. The results from this study suggest that the essential function of gD in virus entry is to modulate other virus-cell interaction(s) involved in productive virus penetration.