Rapid detection of bovine herpesvirus 1 in the semen of infected bulls by a nested polymerase chain reaction assay.

A nested polymerase chain reaction (PCR) assay was developed for the detection of bovine herpesvirus 1 (BHV-1) in bovine semen and compared with the virus isolation method. When extended semen, commonly used in the bovine artificial insemination industry, was inoculated with BHV-1, the PCR assay detected BHV-1 DNA in semen inoculated at 0.25-2.5 TCID50 per 0.5 mL. In contrast, the lower limit of detection for virus isolation was 250 TCID50 of BHV-1 inoculated in 0.5 mL of extended semen. These methods were also used to detect BHV-1 in the semen of four bulls which were experimentally infected with BHV-1. All infected bulls demonstrated balanitis at 3 d post-inoculation (DPI) and severe balanoposthitis at 4 DPI. BHV-1 was detected in raw semen by virus isolation and PCR at 2 DPI, before balanitis was evident. For virus isolation, the last day that BHV-1 was detected during primary infection was 7 DPI for two bulls and 9 and 11 DPI for the other two bulls. In contrast, PCR detected BHV-1 in the bulls' semen until 14 or 18 DPI. For individual animals, PCR detected BHV-1 during primary infection for at least 1-10 d longer than virus isolation. Reactivation of BHV-1 from latency without the presence of visible lesions was promoted twice by two series of 5 d dexamethasone injections. For the first series of dexamethasone treatments, a positive virus isolation result was obtained on the 5th d of treatment for only one bull. In contrast, two bulls demonstrated evidence of viral reactivation on this day by PCR. All bulls shed BHV-1 in semen on d 4 after dexamethasone treatment, as evidenced by positive virus isolation and PCR results. One bull was still PCR positive 13 d later. For the second series of dexamethasone treatments, a small amount of virus was isolated from semen collected on d 3 or 4 after treatment for two bulls but not from the other two bulls. In contrast, semen samples from all bulls were PCR positive for either or both of these 2 d. In total, from 80 semen samples, 45 were PCR positive and 26 were virus isolation positive. Thus, the PCR assay detected BHV-1 shedding in bulls earlier, more often, and for a longer duration, than did the virus isolation method.     

Establishment of conditions for the detection of bovine herpesvirus-1 by polymerase chain reaction using primers in the thymidine kinase region.

Polymerase chain reaction (PCR) for detection of bovine herpesvirus-1 (BHV-1) was developed and optimized using 22 bp sense and 20 bp antisense primers in the thymidine kinase (TK) coding region. The amplification product is 183 bp long. The PCR optimization was done using BHV-1 tissue culture supernate (BHV-1TCS), concentrated BHV-1 tissue culture supernate (cBHV-1TCS) and sucrose gradient purified BHV-1 (pBHV-1). The sensitivity of four methods of sample preparation which are standard DNA extraction, modified proteinase K (PK) digestion, GeneReleaserTM + 34 cycles or + 44 cycles, and boiling were compared with virus isolation (VI) using BHV-1TCS. The incorporation of 10% glycerol in the reaction mixture, the incubation in PK for 18 hours and predenaturation of samples and cooling in ice prior to PCR were essential for the amplification of BHV-1 DNA for samples prepared by standard DNA extraction and modified PK digestion. The preparation of samples by Gene-ReleaserTM, a proprietary nucleic acid releasing cocktail, showed 10 to 1,000-fold increase in sensitivity compared to standard DNA extraction and modified PK digestion. No amplification was observed in samples prepared by boiling. The sample preparation of BHV-1 LA strain by GeneReleaserTM showed sensitivity equivalent to virus isolation. The BHV-1 TK PCR using GeneReleaserTM has a detection limit of 1 picogram and 10 fentograms of purified BHV-1 DNA using ethidium bromide stained gel and Southern blot hybridization, respectively. It could detect viral DNA in 1,000 infected cells in a total suspension of 10,000 cells using either ethidium bromide stained gel or Southern blot hybridization.     

Molecular detection of BHV-1 in artificially inoculated semen and in the semen of a latently infected bull treated with dexamethasone

Two polymerase chain reaction (PCR) assays specific for glycoprotein B (gB) and glycoprotein E (gE) gene detection, respectively, were adopted for the detection of bovine herpesvirus-1 (BHV-1) in naturally infected bulls. The methods were tested on bovine semen artificially inoculated with BHV-1 and were compared with an optimised virus isolation method. Raw and extended semen samples were diluted in minimal essential medium (MEM) and spiked with equal dose of BHV-1. The extended semen was found to be more toxic for the cells than the raw semen, while the viral DNA could be detected by the PCR method in all tested dilutions of raw and extended semen samples. The sensitivity of both methods was compared also for BHV-1 detection in semen, nasal swabs and leucocytes of a seropositive bull in a different time period after virus reactivation with dexamethasone treatment. The sensitivity of virus detection by the PCR method was equivalent to that of virus isolation in cell culture. However, PCR was shown to be faster and easier to perform and may be a good alternative to virus isolation especially when bovine semen has to be screened for BHV-1 prior to artificial insemination.     

Molecular diagnosis of alcelaphine herpesvirus (malignant catarrhal fever) infections by nested amplification of viral DNA in bovine blood buffy coat specimens

A fragment of alcelaphine herpesvirus-1 (AHV-1; malignant catarrhal fever) DNA was subcloned into pUC 18 and sequenced. The subclone hybridized strongly to AHV-1 DNA, weakly to alcelaphine herpesvirus-2 (AHV-2) DNA, and not at all to DNA from bovine herpesvirus-1 (BHV-1; infectious bovine rhinotracheitis [IBR] virus), bovine herpesvirus-2 (BHV-2; bovine herpes mamillitis [BHM] virus), and bovine herpesvirus-4 (BHV-4; isolate DN599). A 2-stage (nested) polymerase chain reaction (PCR) diagnostic test was devised based on a portion of the subcloned AHV-1 DNA sequence. First and second stage amplified AHV-1 DNA targets were 487 and 172 base pairs (bp) in length, respectively. Unique Pvu II and Stu I restriction endonuclease cleavage sites confirmed the identity of amplified AHV-1 DNA. Five AHV-1 and 2 AHV-2 isolates were identically and specifically PCR positive. BHV-1, BHV-2, and BHV-4 viruses were negative by the same procedure. As little as 0.01 TCID50 AHV-1 was detected using the nested amplification procedure. Simple methods of buffy coat isolation from bovine blood were employed to prepare specimens for PCR. An AHV-1-infected calf was PCR positive from 3 to 77 days postinoculation (PI), with rising seroconversion first noted 14 days PI. The AHV-1 DNA sequence was 62% homologous to a portion of the Epstein-Barr virus genome. The nested PCR procedure may improve the viral diagnosis of clinical and subclinical alcelaphine herpesvirus infections.     

Detection of BHV-1 in a Naturally Infected Bovine Fetus by a Nested PCR assay

Bovine herpesvirus 1 (BHV-1) is frequently associated with abortion in naturally and experimentally infected cattle. Most of the virus isolation and immunofluorescent antibody protocols described in the literature for detecting BHV-1 in bovine foetuses are rather laborious, costly and time-consuming. The detection is described of BHV-1 in the tissues of a naturally aborted bovine foetus by a nested PCR assay with no further hybridization procedures.Optimal results were achieved by filtering the foetal tissues on a chromatography column before DNA extraction, by using two pairs of primers in a nested PCR and by evaluating the amplification products on silver-stained polyacrylamide gels.This nested PCR was faster and easier to perform than the virus isolation test. To our knowledge, this is the first time that BHV-1 has been detected in the tissues of a naturally infected bovine foetus by means of a nested PCR. The test seems to be a practical alternative for rapid detection of BHV-1 in bovine foetus.     

Inactivation of bovine herpesvirus 1 in semen using a hyperimmune egg yolk semen extender

Hyperimmune egg yolk semen extender was used for the inactivation of bovine herpesvirus (BHV-1) in experimentally infected bovine semen. As much as 5 x 10(4) TCID50/ml of virus was inactivated in semen as assayed by tissue culture. Moreover the hyperimmune egg yolk semen extender did not produce any adverse effect on the quality of the semen after being frozen/thawed in comparison with normal egg yolk semen extender (P > 0.05). The hyperimmune egg yolk semen extender is considered an important tool for containing the spread of BHV-1 from infected semen.     

Evaluation of an antigen-capture ELISA for the detection of bovine herpesvirus type 1 shedding from feedlot cattle

A total of 457 nasal swab specimens from cases of respiratory disease in 2 feed lots were evaluated for the detection of bovine herpesvirus Type 1 (BHV-1) by ELISA. Thirty-three were found to be positive for BHV-1 by the recovery of infectious virus and 21 of these were positive by ELISA, yielding a sensitivity of 64%. Fifteen other virus isolations were made and included bovine viral diarrhea viruses, rhinoviruses and parainfluenza Type 3 viruses; none of these cases were positive with the BHV-1 ELISA. Specificity of the ELISA was 100%. Eighty percent of the specimens with BHV-1 titers greater than 10(5) TCID50 were detected by ELISA; the median amount of virus in positive specimens that were detected by ELISA was 7 X 10(5) TCID50 and the median amount of virus in specimens not detected was 1.5 X 10(4) TCID50. BHV-1 infection was most frequently diagnosed in feedlot cattle that had been in the feedlot for 40-80 days. Approximately half of the infected cattle were carrying virus-neutralizing antibodies in their serum.     

A polymerase chain reaction (PCR) assay for the detection of bovine herpesvirus 1 (BHV1) in selectively digested whole bovine semen

A PCR assay for the detection of bovine herpesvirus type 1 (BHV1) DNA in selectively digested whole bovine semen was developed and evaluated. A brief treatment with proteinase-K was used to lyse free virus, virus present in non-sperm cells and virus adhering to the spermatozoa. Genomic bovine DNA was not released by this treatment. Primers and probes were based on the nucleotide sequence of the gD gene. BHV1 virus-spiked split samples were used as positive controls and the PCR products were detected by eye in ethidium bromide-stained agarose gels. Sequentially collected non-extended semen samples from experimentally infected bulls were used to compare this assay with virus isolation. Of a total of 162 ejaculates, 51 were found positive by virus isolation, whereas PCR detected BHV1 DNA in 73. PCR detected BHV1 DNA for a longer period after infection and reaction. Apart from its superior sensitivity, this PCR assay also has the advantage of being a relatively simple procedure, providing results within 24 h.Abbreviations AI artificial insemination - BHV1 bovine herpesvirus type 1 - PCR polymerase chain reaction - TCID₅₀ tissue culture infective dose, 50%     

A rapid and sensitive PCR-based diagnostic assay to detect bovine herpesvirus 1 in routine diagnostic submissions

We describe a rapid, sensitive and specific polymerase chain reaction (PCR) assay for the detection of BHV1 DNA in a range of routine diagnostic submissions without the need for prior virus isolation. The assay, which is based on the selected amplification of a portion of the viral tk gene, detected both BHV1.1 and BHV1.2 subtypes in a panel of 15 characterised field isolates, and its sensitivity was estimated to be <0.125 TCID(50). BHV2, alcephaline herpesvirus, BHV4, equine herpesvirus 1 (EHV1), EHV4 and pseudorabies virus were not detected confirming the specificity of the assay. One hundred and five diagnostic submissions, including tissues, nasal secretions and nasal swabs were taken from cattle with respiratory disease and tested using the routine methods of virus isolation (VI) and the fluorescent antibody test (FAT), and the results were compared with those obtained by PCR. The PCR assay detected BHV1 DNA in all samples that were positive by VI. BHV1 DNA was also detectable by PCR in raw and extended semen samples at a sensitivity of 1 TCID(50) per 50microl. The assay also detected BHV5, permitting differentiation between it and BHV1 by virtue of the size of the amplified PCR product. The PCR assay is more sensitive and independent of sample quality than either virus isolation or FAT, and it is faster than virus isolation. The sample preparation method is simple with few steps involved. There are no extra post-amplification blotting/hybridisation steps and the assay is not based on a nested PCR strategy that might otherwise exacerbate the problem of oversensitivity/contamination in the routine use of such a test in a diagnostic laboratory. This assay would permit discrimination between those animals naturally infected with wild type BHV1 and those vaccinated with tk-BHV1 strains.     

Elimination of toxicity and enhanced detection of lumpy skin disease virus on cell culture from experimentally infected bovine semen samples

Lumpy skin disease virus (LSDV), a poxvirus of the genus Capripoxvirus, is shed in the semen of infected bulls. The screening of semen for infectious virus requires a sensitive diagnostic method. The isolation of the virus on cell cultures and/or the polymerase chain reaction (PCR) are sensitive diagnostic tests which may be used to screen semen for LSD viral DNA prior to artificial insemination. Although cell culture detects infectious virus and is a sensitive method, there are major difficulties in using this method due to the toxic effect of semen on the cells. The aim of this study was to find a method that decreases the toxic effect of semen and enhances the isolation of LSDV on cell culture. Semen samples from LSDV sero-negative bulls were collected and infected with a field isolate of LSDV, strain V248/93, with a titre of 6.5 log TCID50. The semen samples were treated with one of four different methods: centrifugation, serial dilution, filtration and chemical treatment with kaolin. The samples subjected to centrifugation, serial dilution and filtration were supplemented with gentamycin. Semen toxicity on cell cultures was eliminated when supernatants of semen samples centrifuged at 2000 rpm for 1, 3 and 5 min and serially diluted were used to inoculate confluent monolayer bovine dermis cells. The toxicity recorded when the pellet fractions of semen samples centrifuged for 5 min at 2000 rpm was comparable to results obtained from serially diluted samples supplemented with gentamycin. Filtration and kaolin treatment of semen samples did not remove the toxic effect.     

An international inter-laboratory ring trial to evaluate a real-time PCR assay for the detection of bovine herpesvirus 1 in extended bovine semen

Six laboratories participated in a ring trial to evaluate the reliability of a real-time PCR assay for the detection of bovine herpesvirus 1 (BoHV-1) from extended bovine semen. Sets of coded samples were prepared and distributed to each of the laboratories. The sample panel contained semen from naturally and artificially infected bulls, serial dilutions of positive semen with negative semen, semen from uninfected seronegative bulls, negative semen spiked with virus, as well as serial dilutions of reference virus. The samples were tested using a previously validated real-time PCR assay for the detection of BoHV-1 in each participating laboratory. The PCR tests were conducted with four different real-time PCR amplification platforms, including RotorGene 3000, Stratagene MX 3000/4000, ABI 7900, and Roche LightCycler 2.0. Virus isolation using one set of samples was performed in one laboratory. The results of the laboratories were compared with one another, and with those of virus isolation. It was found that the sensitivity and specificity of the real-time PCR test was greater than those of virus isolation (82.7% versus 53.6% and 93.6% versus 84.6%, respectively). A high level of agreement on PCR testing results between the laboratories was achieved (kappa value 0.59-0.95). The results of this study indicate that the real-time PCR assay is suitable for the detection of BoHV-1 in extended semen, and would be a good substitute for the slow and laborious virus isolation, for the screening testing at artificial insemination centres and for international trade.     

Persistent infection of bovine herpesvirus type 4 in bovine endothelial cell cultures

Herpesviruses can establish a persistent infection in the cells and tissues of their natural hosts and thus may produce diseases due to cytolytic infections. We have isolated a herpesvirus from a bovine vascular endothelial cell culture after continuous subculturing. Typical cytopathic changes were observed in bovine endothelial cell cultures 2 days after inoculation of the virus. The virus had an icosahedral nucleocapsid of 100-150 nm in diameter and an envelope. The sequences of some DNA fragments of the virus were highly homologous to those of the bovine herpesvirus type 4 (BHV-4) strains. The DNA restriction maps of the virus and the reference strains of BHV-4, DN 599 and Movar 33/63 were very similar but not identical. Therefore, the newly isolated virus has been designated Taiwan strain. The presence of BHV-4 DNA in apparently normal bovine endothelial cell cultures was shown by Southern blot hybridization with the BamHI fragment of the newly isolated BHV-4 and was further confirmed by digestion of the DNA with BamHI plus AccI. In conclusion, we have demonstrated that BHV-4 persisted in the bovine endothelial cell cultures and continuous subcultures could lead to the production of infectious viral particles.     

牛精液中基因I型牛病毒性腹泻病毒荧光探针定量RT-PCR检测方法的建立

为建立牛精液中基因I型牛病毒性腹泻病毒(BVDV-1)的快速检测方法,本研究采用Sephycral S-400凝胶对牛精液过滤处理后提取病毒核酸,根据BVDV-1 5'UTR保守区基因序列,设计特异性引物和荧光探针,通过反应条件的优化,建立了牛精液中BVDV-1荧光定量RT-PCR检测方法.该方法可以检测到牛精液中含量为0.0125 TCID50的病毒,灵敏度比病毒分离方法高200倍～2000倍,比常规RT-PCR方法高10倍.对从同一个牛场6个月内采集的120份新鲜牛精液和40份冷冻牛精液用该荧光RT-PCR方法检测,没有检测到BVDV-1阳性样品.对其中的10头牛定期检测精液中病毒的同时,并同步检测了全血中的病毒和血清抗体,结果血清抗体阳性牛精液中没有检测到病毒,本研究结果表明,不能以血清抗体阴阳性做为精液是否带毒的依据.     

Use of in situ hybridization with a biotinylated probe for the detection of bovine herpesvirus-1 in aborted fetal tissue

Forty-five cases of bovine abortion were examined using in situ hybridization (ISH) with a biotinylated DNA probe specific for bovine herpesvirus-1 (BHV-1). Of the 45 cases, 16 were diagnosed as due to BHV-1, 15 were determined to be due to other causes, and 14 were of undetermined etiology. Direct comparisons between ISH and an immunoperoxidase (IP) test specific for BHV-1 were performed on formalin-fixed, paraffin-embedded tissue sections of lung, liver, kidney, spleen, thymus, and placenta; fluorescent antibody tests for BHV-1 and virus isolation were performed on fresh lung and liver. In comparison to these routine BHV-1 detection techniques, ISH had an overall sensitivity of 88.2% and a specificity of 89.3% in detecting BHV-1 in aborted fetuses. Immunoperoxidase was more sensitive than ISH with tissue sections from lung (87.5% vs. 69%), liver (92% vs. 17%), spleen, and placenta; results of the tests on tissue sections from kidney were concordant. Liver sections presented special problems in that nonspecific reactions were frequently observed with hybridization. With thymus sections, the rate of detection was higher by hybridization than by IP, but the specificity of some of these reactions could not be confirmed.     

Detection of Brucella melitensis in semen using the polymerase chain reaction assay

An evaluation of the polymerase chain reaction (PCR) for detection of Brucella melitensis DNA in bovine and ovine semen was performed. Since semen contains different components that inhibit PCR amplification, a protocol was used to purify Brucella-DNA from bovine and ovine semen samples prior to conducting amplification of the targeted DNA. When separated fractions of naturally Brucella contaminated semen were analyzed by the PCR, most of B. melitensis DNA were present in the seminal fluid and non-sperm fractions.The PCR examination results for detection of B. melitensis DNA in different semen fractions were compared with the results for traditional cultural methods of Brucella from semen. The PCR was more sensitive than the traditional cultural methods since it detected Brucella-DNA in 12 (10%) out of 120 semen samples while direct culture detected only 7 (5.8%) in the same semen samples. The limit of detection by PCR was 100 CFU/ml of semen. In addition, the results of PCR were available in one day, whereas isolation and identification of Brucella organisms required days or even weeks. The PCR may be used as a supplementary test for detection of B. melitensis in semen.     

BHV-1在牛胚气管细胞中的增殖规律研究

为研究牛疱疹病毒Ⅰ型(BHV-1)在牛胚气管细胞(EBTr)中的生长特性和增殖规律,参考文献设计合成特异性引物和探针,建立了TaqMan实时荧光定量PCR方法,检测BHV-1感染EBTr细胞6、12、24、48、72、96、120、144h后病毒的增殖规律,并观察对应时间点的细胞病变(CPE)。结果显示,用100TCID_(50)的BHV-1感染EBTr细胞,48h后开始出现细胞病变,72h细胞病变明显,120h细胞大部分变圆,开始脱落,144h细胞大面积脱落、崩解。实时荧光定量PCR检测结果表明,BHV-1感染EBTr在6h~24h内,病毒缓慢增殖,48h~96h,病毒增殖速度加快,拷贝数呈对数增长,120h~144h,BHV-1的含量仍然呈现升高的趋势,但增长速度变慢。结果证明,BHV-1能够在EBTr中产生CPE,而且CPE程度与病毒DNA增殖规律一致,该结果可以为深入研究BHV-1对EBTr细胞的致病机理提供基础资料。     

Intrapreputial infection of young bulls with bovine herpesvirus type 1.2 (BHV-1.2): acute balanoposthitis, latent infection and detection of viral DNA in regional neural and non-neural tissues 50 days after experimental reactivation

Venereal infection of bulls with bovine herpesvirus type 1.2 (BHV-1.2) may result in acute balanoposthitis followed by the establishment of latent infection, presumably in dorsal root nerve ganglia. We herein report the characterization of the acute and latent infection of young bulls with a Brazilian BHV-1.2 isolate and the investigation of neural and non-neural sites in which viral DNA persists during latent infection, i.e. 110 days after inoculation and 50 days after experimental reactivation. Intrapreputial inoculation of BHV-1.2 isolate SV-56/90 (10(6.5)pfu per animal) resulted in severe balanoposthitis, characterized by redness of the penis and preputial mucosa, coalescent vesicles and fibrinous exsudate in all four infected bulls. Virus shedding was detected in preputial secretions and semen up to days 14 and 13 pi, respectively. Dexamethasone administration at day 60 pi led to reactivation of the infection in all animals, resulting in virus shedding in preputial secretions and/or in semen. At day 50 post-reactivation (pr), the animals were euthanized and regional tissues were collected for PCR and virus isolation. Viral DNA was consistently detected in the dorsal root ganglia of nerves genito-femoral (4/4) and obturator (4/4); frequently in the pudendal (3/4), sciatic (3/4) and rectal caudal nerve ganglia (2/3). In addition, viral DNA was detected in the pelvic sympathetic plexus of one bull and in regional lymph nodes (deep inguinal (2/4); sacral (1/4); medial iliac (1/4)) of two bulls. No infectious virus could be recovered from homogenates of DNA positive tissues, indicating the absence of actively replicating virus. These results demonstrate that BHV-1.2 DNA may persist in several sacral nerve ganglia and in regional lymph nodes as well during latent infection, i.e. 50 days after experimental reactivation. These findings may help in understanding the pathogenesis of acute and latent genital infection by BHV-1.2.     

A Comparison of Three Techniques for Detecting Bovine Herpesvirus Type 1 (BHV-1) in Naturally and Experimentally Contaminated Bovine Semen

Contents: Immune electron microscopy, hybridization (Sandwich, Southern-blot and dot-blot hybridization) as well as two cell culture inoculation techniques to detect bovine herpesvirus 1 (BHV-1) in naturally and artificially contamined bovine semen were compared. Immune electron microscopy was not a suitable method because of its low limit of detection. Dot-blot hybridization, as the most sensitive hybridization technique, could detect 150 pg BHV-1 DNA/semen straw (～ 10⁶TCID₅₀/ 500 μl semen). Best results were obtained by using cell culture techniques. With the first technique embryonic bovine lung cells (EBLC) on microtiterplates were inoculated with an ultracentrifuged pellet of seminal plasma (pelleting method). The second procedure comprised a dilution of 250 μl (1/2 content of a straw) in 6,25 ml cell culture medium which were overlayed on a confluent layer of EBLC in a 25 cm² flask. After an incubation of 4 hours at 37°C the medium was decanted and replaced by 6,5 ml fresh medium (dilution method). With both tissue culture methods as little as 5 TCID₅₀ of BHV-1 in 500 μl of artificially contaminated semen were detectable. However the dilution method was better suited than the pelleting method because toxic effects to cells were less pronounced. It was even possible to detect BHV-1 in naturally contaminated semen samples where all other methods failed. The DNA of virus isolates from semen showed three different restriction patterns. Inhalt: Vergleich dreier Methoden zum Nachweis von bovinem Herpesvirus Typ 1 (BHV-1) in natürlich und experimentell kontaminiertem Rindersamen Die Immunelektronenmikroskopie, die Hybridisation (Sandwich-, Southern-Blot- und die Dot-Blot Hybridisation) sowie zwei Zellkultur-Inokulationstechniken wurden zum Nachweis von bovinem Herpesvirus Typ-1 (BHV-1) in natürlich und künstlich kontaminiertem Stierensamen verglichen. Die Immunelektronenmikroskopie erwies sich dabei als zu wenig empfindliche Methode. Die Dot-Blot Hybridisation war die beste der Hybridbationsmethoden. Es lieβen sich damit bis zu 150 pg BHV-1 DNA/Paillette (～ 10⁶ TCID ₅₀ /500 μl Samen) nachweisen. Am besten eigneten sich Zellkulturmethoden. Eine erste Methode bestand darin, embyonale bovine Lungenzellen in Microtiterplatten mit einem Ultrazentrifugensediment des Samenplasmas zu inokulieren (pelleting method). In einem zweiten Verfahren wurde 1/2 Inhalt einer Pailette (250 μl) in 6,25 ml Zellkulturmedium verdünnt und damit ein Zellrasen von embyonalen bovinen Lungenzellen überschichtet. Nach 4 h bei 37°C wurde das Medium abgegossen und durch 6,5 ml neues Medium ersetzt (Verdünnungsmethode). Mit beiden Methoden lieβen sich 5 TCID₅₀ BHV-1 in 500 μl Rünstlich kontaminiertem Samen nachweisen. Die Verdünnungsmethode war aber besser geeignet, weil der toxische Effekt auf die Zellen geringgradiger war. Mit der Verdünnungsmethode lieβ sich aus Ejakulaten BHV-1 isolieren, auch in Fällen, in denen alle andern Methoden versagten. Die DNA's von Virusisolaten aus Rindersamen wiesen drei verschiedene Restriktionsmuster auf.     

Validating bovine sexed semen samples using quantitative PCR

In cattle, separation of X‐ and Y‐bearing sperm cells by flow‐sorting technology makes it possible to predetermine the sex of calves. Due to high costs and decrease in fertilization, the extensive use of sexed semen in livestock depends heavily on sorting purity of sperm cells. Validating the accuracy of sperm sexing requires reliable procedures, therefore a real‐time polymerase chain reaction (PCR) assay was established to calculate the male cell proportion in the sexed semen based on the relationship between the amplification of a SRY fragment and an autosomal gene (MSHR) fragment. Our results showed stable amplification of SRY for 100–1 ng of genomic DNA, which allows detection of 1% of male cells if 100 ng of target DNA is used. To account for the discrepancy in the efficiency of the MSHR and the SRY amplification correction of the difference of the mean values was performed. The ratio of male to female sperm cells in unsexed semen cells was very accurately determined. The fractions of the sexed samples, however, were different from the expected range appearing lower than estimated. Thus, the study reveals that real‐time PCR provides a good basis for the examination of sexed sperm cells, but needs to be optimized for the samples.     

Vaccination of calves against bovine herpesvirus-1: assessment of the protective value of eight vaccines

Eight separate, but related experiments, were carried out in which groups of six calves were vaccinated with one of eight commercial vaccines. In each experiment the vaccinated calves were subsequently exposed to three calves infected with virulent bovine herpesvirus-1 (BHV-1). In each experiment, all infected donor calves developed a typical severe infectious bovine rhinotracheitis (IBR) infection and excreted virus in their nasal secretions of up to 10(8.00) TCID50/0.1 ml. One live BHV-1 gE-negative vaccine (A) and three modified live vaccines (B, C, D), administered intranasally, all protected against clinical disease. The calves vaccinated with one vaccine (C) also did not excrete virus in the nasal secretions, whereas the calves protected by vaccines A, B and D excreted virus in their nasal secretions but at low titres (10(0.66)-10(1.24) TCID50/0.1 ml). A fourth modified live vaccine (E), given intramuscularly, failed to prevent mild clinical disease in the calves which also excreted virus in the nasal secretions at titre of 10(1.00) TCID50/0.1 ml. An analogous result was given by the calves vaccinated with either of the two inactivated vaccines (F and G) or with a BHV-1 subunit vaccine (H). All calves developed mild clinical signs and excreted virus at titres of 10(2.20)-10(3.12) TCID50/0.1 ml. Calves vaccinated with C vaccine were subsequently given dexamethasone, following which virus was recovered from their nasal secretions. The virus isolates did not cause disease when calves were infected and appeared to be closely related to the vaccine strain.