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.