A DNA aptamer efficiently inhibits the infectivity of Bovine herpesvirus 1 by blocking viral entry.

Bovine herpesvirus 1 (BoHV-1) is an important pathogen of domestic and wild cattle responsible for major economic losses in dairy and beef industries throughout the world. Inhibition of viral entry plays a crucial role in the control of BoHV-1 infection and aptamers have been reported to inhibit viral replication. In this study, nine DNA aptamers that target BoHV-1 were generated using systemic evolution of ligands by exponential enrichment. Of the nine candidates, aptamer IBRV-A4 exhibited the highest affinity and specificity for BoHV-1, which bound to BoHV-1 with a Kd value of 3.519 nM and demonstrated the greatest virus binding as shown by fluorescence imaging. The neutralizing ability of aptamer IBRV-A4 was determined using neutralization assays and real time PCR in BoHV-1 infected Madin-darby bovine kidney cells. Virus titration, immunofluorescence and confocal laser scanning microscopy showed virus replication significantly decreased when aptamer IBRV-A4 was added to BoHV-1 infected MDBK cells at 0 and 0.5 hours post-infection, whereas no change was seen when IBRV-A4 was added 2 hours post-infection. This concludes that aptamer IBRV-A4 efficiently inhibits viral entry of BoHV-1 in MDBK cells and is therefore a novel tool for diagnosis and treatment of BoHV-1 infection in cattle.

[Study of antiviral activity of different drugs against bovine herpes virus and pestivirus]. / Izuchenie antivirusnykh svoistv preparatov razlichnogo proiskhozhdeniia v otnoshenii gerpes- i pestivirusov krupnogo rogatogo skota.

In vitro antiviral activity of 11 different drugs against the viruses of infectious bovine rhionotracheitis (IBR) and bovine viral diarrhea (BVD) was studied. The ID50 of the drugs were determined in monolayers of cell cultures MDBK and KCT: 20 mcg/ml for anandin, 25 mcg/ml for polyprenole, 50 mcg/ml for bromuridin, methisazone, aciclovir, gossypole, ribavirin and liposomal ribavirin, 100 mcg/ml for eracond, and 200 mcg/ml for phosprenil and argovit. Phosprenil was the only drug that showed virucidal activity against the IBR virus. All the drugs inhibited reproduction of the IBR virus in sensitive cell culture MDBK: 100,000-fold inhibition by bromuridin, aciclovir, ribavirin and methisazone, 1000-10000-fold inhibition by liposomal ribavirin, gossypole, anandin, polyprenole and phosprenil, 100-fold inhibition by eracond and argovit. As for the BVD virus, bromuridin, phosprenil, polyprenole, methisazone, aciclovir, gossypole, argovit, ribavirin and liposomal ribavirin also showed their activity in cell culture KCT (100-10,000-fold inhibition). The other drugs were ineffective.

Field study of undifferentiated respiratory disease in housed beef calves.

A severe outbreak of undifferentiated respiratory disease affecting 119 of 144 (82.6 per cent) two- to five-month-old housed beef calves was studied by monitoring their clinical signs and rectal temperatures daily or every second day for two months. New cases of respiratory disease, which were first identified three weeks after the calves were housed, occurred over a period of 29 days. The cause of the outbreak was not conclusively determined although 20 per cent of the calves sampled showed serological evidence of recent infection with bovine respiratory syncytial virus and parainfluenzavirus 3. Seventeen of 61 calves (27.9 per cent) which were treated with tilmicosin had to be treated again, compared with nine of 58 calves (15.5 per cent) which were treated with both tilmicosin and flunixin meglumine and did not need further treatment, but this difference was not statistically significant.

Recovery rate and plasma zinc and copper concentrations of steer calves fed organic and inorganic zinc and manganese sources with or without injectable copper and challenged with infectious bovine rhinotracheitis virus.

Two experiments were conducted using feeder calves in a randomized block design to determine the effects of organic and inorganic sources of Zn and Mn fed pre- and posttransit (Exp. 1 and 2) with or without injectable Cu (Exp. 2) on DMI, rectal temperature, BW changes, and plasma Zn and Cu concentrations of feedlot steers challenged with infectious bovine rhinotracheitis virus (IBRV). In Exp. 1, before weaning, all steers and their dams received the following free-choice mineral supplements: 1) control (no supplemental Zn or Mn), 2) ZnO+MnO (ZnMnO), and 3) Zn methionine+Mn methionine (ZnMnMet). In Exp. 2, 18 d before weaning and shipping, steers were allotted into two groups (22 steers/group) and fed 225 mg of Zn.steer-1 x d-1 in .9 kg of ground corn as ZnO or ZnMet. Half of the steers from each group were injected (s.c.) with 120 mg of Cu from Cu glycinate. Steers (Exp. 1 and 2) were weaned and shipped approximately 2,500 km to the feedlot, where they received the same supplements in the form of a complete diet for 34 d, during which time calves recovered from the stress due to shipment. All steers were initially sero-negative to IBRV. On d 34 (d 0 of IBRV), all steers were challenged with IBRV and DMI, rectal temperature, and BW change were monitored for 28 d.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of (S)-1-(3-hydroxy-2-phosphonyl-methoxypropyl)cytosine (HPMPC) on bovine herpesvirus-1 (BHV-1) infection and reactivation in cattle.

A reproducible pattern of respiratory disease was produced in calves inoculated intranasally with a pathogenic strain of bovine herpesvirus-1 (BHV-1). A latent infection was established which could be reactivated by means of corticosteroid administration. Groups of calves were given a single dose of 20 mg/kg of (S)-1-(3-hydroxy-2-phosphonyl-methoxypropyl)cytosine (HPMPC) either the day before or the day following virus inoculation. The drug markedly reduced clinical signs and virus replication; the therapeutic dose appeared to be more effective than the dose given one day before virus inoculation. The establishment of latency was not prevented and a single dose of HPMPC, the day before a course of dexamethasone (6 weeks after the acute infection), did not prevent virus shedding.

Feed intake, rectal temperature, and serum mineral concentrations of feedlot cattle fed zinc oxide or zinc methionine and challenged with infectious bovine rhinotracheitis virus.

Three experiments were conducted using feedlot steers in a randomized block design to determine the effect of zinc methionine (ZnMet) and zinc oxide (Exp. 3) on feed intake (DMI), rectal temperature, and serum mineral concentrations of feedlot cattle challenged with infectious bovine rhinotracheitis virus (IBRV). All the steers used were seronegative to IBRV. Steers were adapted for 7 d to their respective diets and challenged with 3.7 x 10(5) plaque forming units of IRBV on d 0 of each experiment. Live BW, rectal temperature, and individual daily DMI were recorded for 14 d. Blood samples were taken on d 0, 7, and 14. In Exp. 1, daily DMI of the control steers (Zn = 31 ppm) decreased 50% compared with 15% in the ZnMet (Zn = 90 ppm) steers 3 d after IBRV challenge. By d 6, the ZnMet steers had regained their pretrial mean daily DMI, but the control steers took 11 d. The ZnMet steers had lower (P less than .05) mean rectal temperature than the control steers on d 7 and 12. In Exp. 2, the control (Zn = 35 ppm) steers had lower (P less than .05) daily DMI on d 8 to 12 than the ZnMet (Zn = 89 ppm) steers. In Exp. 3, the mean decrease in daily DMI tended to be more rapid in the ZnO steers than in the control and ZnMet steers. All steers had the lowest daily DMI on d 5 and 6, coinciding with the highest rectal temperature. Serum Zn, P, and Mg concentrations decreased and serum Cu increased in all steers after infection. These data suggest that dietary Zn enhanced the recovery rate of IBRV-stressed cattle.

[The immunostimulating action of suramin in infection with the infectious rhinotracheitis virus]. / Imunovuzstanovitelno deistvie na suramin pri infektsiia s virusa na zarazniia rinotrakheit.

The immunostimulating antiviral preparation suramin has a favourable effect on the process and outcome of an experimental infection with the virus of infectious rhinotracheitis (bovine herpes virus type 1, BHV1), thus reducing the gravity of the clinical course and increasing the survival rate. The therapeutic protective effect of the preparation is expressed in the prevention of virus-induced immunosuppression which is markedly strong during the acute phase of the infection process. Suramin restored the number, viability, relative share in the bronchial lavage population, phagocytic and microbicidal capacity of the alveolar macrophages--a major factor of the local defence mechanisms of the lung. In a similar way suramin influenced some parameters of the systemic immunity (number and differential count of polymorphonuclear phagocytes, plaque- and rosette-forming cells). The application of suramin in doses lower than those used for virus inhibition and its considerable action on different mechanisms of the immune system suggested that the preparation's therapeutic effect could be related mainly to its immunostimulating properties.

Effect of infectious bovine rhinotracheitis virus immunization on viral shedding in challenge-exposed calves treated with dexamethasone.

Calves not vaccinated with infectious bovine rhinotracheitis virus (IBRV) became latently infected when challenge exposed and treated with dexamethasone (DM). Calves that shed IBRV after DM treatment were considered to be latently infected. Vaccination with a temperature-sensitive intranasal vaccine or with formalinized IBRV in Freund's complete adjuvant (IBRV-FCA) protected some, but not all, calves against latent infection--indicating a role for the immune response in preventing latent infection. That all latently infected calves were not detected after DM treatment was indicated by the fact that after a 2nd DM treatment of 3 calves treated 6 months previously and not found to shed virus, 1 of the calves was latently infected. Latently infected calves were inoculated with successive doses of IBRV-FCA and treated with DM. Nonvaccinated calves shed virus, whereas vaccinated calves similarly treated did not shed virus. Because both groups had a comparable cell-mediated immune response, as determined by blastogenic response to IBRV, but the vaccinated group had significantly higher virus-neutralizing antibody titers, a role for humoral antibody in preventing viral shedding was indicated.

Effect of levamisole in immune responses to bovine herpesvirus-1.

The effect of levamisole on bovine immune responses to infectious bovine rhinotracheitis virus was assessed under laboratory and commercial feedlot situations. In all instances, levamisole appeared to have a beneficial effect on antibody responses of the cattle after vaccination. In the smaller scale pilot trials, levamisole appeared to be more efficacious when given 7 days after vaccination, presumably when a large amount of viral antigens was present as a result of viral replication. In the larger feedlot trial, however, response to administration of levamisole at the time of vaccination appeared to be slightly better than if given 7 days later. In all instances that animals had an antibody response before they were challenge-exposed with virulent virus, rectal temperature responses remained below 40 C, indicating that a threshold level of immunity may be acquired after the vaccination and that elevation of this threshold level does not necessarily alter the clinical disease. However, the amount of virus replication and shedding after challenge exposure seemed to be correlated with the level of immunity. These results are discussed in relationship to the role of immunity levels to spread of virus within a feedlot.

Chemotherapeutic value of 2-deoxy-D-glucose in infectious bovine rhinotracheitis viral infection in calves.

Daily injection of 2-deoxy-D-glucose (2-dG) had no protective effect against respiratory tract infection in calves caused by infectious bovine rhinotracheitis virus. It also did not reduce the severity of this infection. Ocular instillation of the drug, however, markedly reduced the severity of viral-induced conjunctivitis and keratoconjunctivitis. The drug was effective when given at the time of ocular infection or after clinical conjunctivitis developed.

Effect of interferon respiratory infections of animals.

Several animal models are available for the evaluation of interferon in respiratory virus infections. Considerable variability exists among the respiratory viruses with respect to sensitivity to exogenous interferon or induced endogenous interferon. Due to this apparent variability, combinations of interferon with immune serum and chemotherapeutic agents may provide a means of more efficient control of respiratory infections.

Role of cell-mediated immunity in the recovery of cattle from primary and recurrent infections with infectious bovine rhinotracheitis virus.

When cattle infected with infectious bovine rhinotracheitis virus (IBRV) were treated 3 months later with a synthetic corticosteroid, consistent recrudescence of the infection was observed. Suppression of cell-mediated immunity, as measured by lymphocyte transformation responses, could be demonstrated at the time of recrudescence. Treatment with adrenocorticotropic hormone and trigeminal neurotomy also resulted in recrudescence of IBRV, but immunosuppression was not detected in these animals. The detection of specific, antigen-induced, lymphocyte transformation responses at the time of recovery from both primary and recurrent infections suggests that cell-mediated immunity may be important in determining the duration and severity of the recurrent infection. However, immunosuppression may not be the direct mechanism of recrudescence. Lesions were not observed in untreated animals, and virus could not be detected in either tissues or secretions. However, both lesions and virus were found consistently after corticosteroid treatment.

Infectious bovine rhinotracheitis virus infection in bulls, with special reference to preputial infection.

In an experiment with infectious bovine rhinotracheitis (IBR) virus in two bulls, observed over a period of 122 weeks, the pattern of virus release was studied. Recurrent, unprovoked release of virus was demonstrated after one year in a nasal washing from one of the bulls and in preputial washings of both on 13 and 4 occasions, respectively, and finally in weeks 113 and 110, although clinical disease was not observed. During periods of recurrent virus release, concentrations of virus in the prepuce were generally much lower than during the period of primary infection; usually, however, they were not of negligible titer. The frequency of such periods and the virus titers observed strongly suggest that an IBR antibody carrier should always be considered as a potential source of infection to other animals. When virus was demonstrated in semen an almost equal amount was found in the preputial washing (50 ml). In week 120, virus replication in the respiratory tract and prepuce was induced in both bulls by prednisolone injections. It is concluded that antibody carriers will rarely attain a state of absolute immunity.