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Journal of Virology, September 1998, p. 7638-7641, Vol. 72, No. 9
Departments of
Immunology/Vaccinology,1
Virology,2 and
Histology/Embryology,3 Faculty of
Veterinary Medicine, University of Liège, B-4000 Liège,
Belgium
Received 10 March 1998/Accepted 12 June 1998
Bovine herpesvirus 1 (BHV-1) induces apoptotic cell death in bovine
peripheral blood mononuclear cells and B-lymphoma cells. Using a BHV-1
glycoprotein H null mutant, we have demonstrated that although
penetration of BHV-1 is not required, attachment of BHV-1 viral
particles is essential for the induction of apoptosis.
Bovine herpesvirus 1 (BHV-1) is a
member of the subfamily Alphaherpesvirinae (28).
In addition to causing initial respiratory infections (36),
BHV-1 can also predispose animals, presumably through immunosuppression
(4, 8), to secondary bacterial infections which lead to
severe pneumonia and death (36). There is increasing
evidence that in a variety of acute viral infections, immunosuppression
is directly associated with the induction of programmed death in cells
involved in immunity (21, 26). Programmed cell death or
apoptosis is an encoded suicide program which allows the elimination of
cells that have been produced in excess, developed improperly, or
sustained genetic damage (32). Apoptosis is characterized morphologically by cell shrinkage, apoptotic-body formation, and condensation of the chromatin (6, 20) and biochemically by fragmentation of DNA into oligonucleosomal DNA fragments (1, 35). BHV-1 can induce apoptosis in peripheral blood mononuclear cells (PBMC) (11, 16) and bovine B-lymphoma (BL-3) cells
(10). The mechanism by which BHV-1 induces apoptotic cell
death is not understood. However, since inactivated BHV-1 viral
particles are still able to induce apoptosis in PBMC cultures, the
mechanism of induction could involve either attachment, penetration, or decapsidation of BHV-1 (11). Several BHV-1 glycoproteins
play an important role during the initial interactions of the viral particle with target cells. Glycoprotein B (gB) and gC have been shown
to be involved in the attachment of BHV-1 to heparan sulfate proteoglycans on the cell surface (5, 18, 25, 33). In addition, gB and gD have been implicated in viral penetration (7,
17, 23, 29). A fourth glycoprotein, gH, which is highly conserved
among members of the subfamily Alphaherpesvirinae (31), is also essential for entry of BHV-1 into target cells (22, 34). Deletion of the gene for gH in BHV-1
(22) causes a defect in viral penetration but not
attachment. Therefore, to further characterize the mechanism by which
BHV-1 induces apoptosis, we used a BHV-1 strain with the gene for gH
deleted (22). This mutant virus offers the opportunity to
test whether viral penetration is required for BHV-1 to induce
apoptosis in BL-3 cells.
BL-3 cells (American Type Culture Collection CRL 8037) were cultured in
Optimem medium (Gibco) containing 20% fetal calf serum (Gibco),
100-IU/ml penicillin (Gibco), and 100-µg/ml streptomycin (Gibco). As
described by Meyer et al. (22), the BHV-1 gH null mutant was
multiplied on gH-expressing Madin-Darby bovine kidney (MDBK)
cells (American Type Culture Collection CCL22; multiplicity of
infection [MOI] of 10) to generate a virus stock in which
virions contain gH in the viral envelope but do not
genetically encode gH (BHV-1 gH We first investigated whether BHV-1 virions devoid of gH (BHV-1
gH
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Attachment but Not Penetration of Bovine
Herpesvirus 1 Is Necessary To Induce Apoptosis in Target
Cells
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ABSTRACT
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TEXT
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/+). A second virus stock
in which virions do not contain gH (BHV-1 gH
/
) and,
consequently, are no longer infectious (22) was generated after multiplication of the BHV-1 gH null mutant on normal MDBK cells
(MOI of 10). The parental wild-type (wt) strain used to construct the
BHV-1 gH null mutant (22) is the BHV-1 LAM strain (kindly
provided by J. T. van Oirschot, Lelystad, The Netherlands) and was
propagated on MDBK cells. After multiplication of the viruses, the
culture medium was clarified by centrifugation at 1,500 × g for 20 min at 4°C and the viruses were pelleted by
ultracentrifugation at 26,000 × g for 2 h at
4°C. Viral pellets were then resuspended in Optimem medium containing
100-IU/ml penicillin and 100-µg/ml streptomycin and stored at
70°C until use.
/
) induce DNA fragmentation in BL-3 cells. For this
purpose, BL-3 cells were mock infected or infected with BHV-1
gH
/
and incubated for 48 h. As a control, the
effects of wt BHV-1 and BHV-1 gH
/+ used at an MOI of 10 were also investigated. After being harvested, the cells were further
processed to detect the occurrence of DNA fragmentation by in situ DNA
fragment labeling and by agarose gel electrophoresis as previously
described (9). The percentages of cells undergoing DNA
fragmentation were determined by flow cytometry using a Becton
Dickinson fluorescence-activated cell sorter. Figure
1 shows that BHV-1 gH
/
is
able to induce DNA fragmentation at an even higher level (52%) than is
wt BHV-1 (30.6%) or BHV-1 gH
/+ (29.5%). The occurrence
of DNA fragmentation was confirmed by agarose gel electrophoresis, by
which the apoptosis-specific internucleosomal laddering was clearly
observable in the DNA obtained from BL-3 cells incubated with wt BHV-1,
BHV-1 gH
/+, or BHV-1 gH
/
, respectively
(Fig. 2, lanes 2 to 4). Mock-infected
cultures always showed background levels of DNA fragmentation (Fig. 1
and 2, lane 1). We also determined, by electron microscopy, the
morphological characteristics of BL-3 cells incubated with BHV-1
gH
/
. After 48 h of incubation, a significant
proportion of BL-3 cells had membrane-bound apoptotic bodies and
distinctive condensation of the chromatin (Fig.
3B). Comparable results were obtained
with wt BHV-1 and BHV-1 gH
/+ (data not shown). Together,
these results demonstrate the accumulation of cells with biochemical
and morphological characteristics of apoptosis in a BL-3 cell culture
incubated with BHV-1 gH
/
.

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FIG. 1.
Percentages of cells with DNA fragmentation in cultures
of BL-3 cells mock infected or infected with wt BHV-1, BHV-1
gH
/+, or BHV-1 gH
/
. Cells were incubated
for 48 h. Each value represents the average ± the standard
deviation of triplicate cultures.

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FIG. 2.
Agarose gel electrophoresis of DNA extracted from BL-3
cells mock infected (lane 1) or infected with wt BHV-1 (lane 2), BHV-1
gH
/+ (lane 3), or BHV-1 gH
/
(lane 4).
Cells were incubated for 48 h. One representative experiment out
of three is shown.

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FIG. 3.
Electron micrographs of BL-3 cells mock infected (A) or
infected with BHV-1 gH
/
(B). (B) BL-3 cells incubated
for 24 h with condensed chromatin in several electron-dense
masses. Bars, 1 µm.
To exclude the possibility that induction of apoptosis by BHV-1
gH
/
was due to phenotypically or genotypically rescued
virions, standard plaque assays were performed on normal and
gH-expressing MDBK cells. BHV-1 gH
/
was not able to
induce plaque formation on normal MDBK cells, while few plaques
developed on gH-expressing MDBK cells. We calculated that the amount of
BHV-1 gH
/
used to infect BL-3 cells still contained
0.001 PFU/BL-3 cell (MOI of 0.001). This residual infectivity of BHV-1
gH
/
could not be responsible for the induction of DNA
fragmentation in BL-3 cells. Indeed, the incubation of BL-3 cells with
BHV-1 gH
/+ at an MOI of 0.1 only induced 12.4% DNA
fragmentation (Fig. 1), which is not significantly higher than the
percentage obtained in mock-infected cultures (11.6%) (Fig. 1). The
induction of apoptosis by BHV-1 gH
/
in BL-3 cells was
therefore not due to phenotypically or genotypically rescued virions
present in this virus stock.
Virions devoid of gH (BHV-1 gH
/
) are unable to enter
MDBK cells (22). However, this observation has not been
confirmed with other cell lines, including BL-3 cells. We therefore
investigated whether BHV-1 gH
/
is indeed unable to
enter BL-3 cells. Since BHV-1 gH
/
contains the
Escherichia coli
-galactosidase gene under control of the
mouse cytomegalovirus immediate-early gene promoter-enhancer in place
of the gH gene (22), we quantified
-galactosidase activity to monitor virus entry into target cells. Indeed, production of
-galactosidase indicates that the virus has entered the cell, released its genome into the nucleus, and activated the constitutive promoter driving
-galactosidase expression (19). For this
assay, MDBK or BL-3 cells were mock infected or infected with wt BHV-1 (MOI of 10), BHV-1 gH
/+ (MOI of 10), or BHV-1
gH
/
(MOI of 0.001) and incubated for 24 h. After
being harvested, the cells were further processed to determine the
percentage of cells expressing
-galactosidase as previously
described (11). In cultures of BL-3 cells incubated with
BHV-1 gH
/+, 22.4% of the cells expressed
-galactosidase (Fig. 4D). In contrast, BL-3 cells which were mock
infected (Fig. 4A) or infected with wt
BHV-1 (Fig. 4B) or BHV-1 gH
/
(Fig. 4C) yielded very low
levels of
-galactosidase expression (0.5, 1.7, and 1.8%,
respectively) (Fig. 4). Similarly, in cultures of MDBK cells incubated
with BHV-1 gH
/+, 78.1% of the cells expressed
-galactosidase while only 1.5, 2, and 3%, respectively, of those in
cultures which were mock infected or infected with BHV-1
gH
/
or wt BHV-1 did so. These observations are
consistent with the results obtained by Meyer et al. (22)
and demonstrate that BHV-1 gH
/
is unable to penetrate
BL-3 cells.
|
Since attachment of BHV-1 is mediated through interactions of viral
glycoproteins with heparinlike moieties (15, 25), we
investigated the effect of heparin (Sigma), a well-known inhibitor of
BHV-1 attachment (15, 25), on the ability of BHV-1
gH
/
to induce apoptosis in BL-3 cells. For this
purpose, BL-3 cells were mock infected or infected with wt BHV-1 (MOI
of 10), BHV-1 gH
/+ (MOI of 10), or BHV-1
gH
/
(MOI of 0.001) with or without simultaneous
addition of heparin at concentrations of 10, 100, and 1,000 IU/ml.
After incubation for 4 h at 37°C, the cells were washed,
resuspended in fresh medium, and further cultivated for 44 h. The
cells were then harvested, and the occurrence of DNA fragmentation was
detected by in situ DNA fragment labeling. In the absence of heparin,
we observed 19% DNA fragmentation in cultures incubated with BHV-1
gH
/
(Fig. 5). In
contrast, cultures containing heparin at 10, 100, and 1,000 IU/ml
showed lower levels of DNA fragmentation (4.7, 3.8, and 1.5%,
respectively) (Fig. 5). Comparable results were obtained with wt BHV-1
and BHV-1 gH
/+ (data not shown). Furthermore, heparin
only slightly reduced the background level of apoptosis in a mock
infected culture (Fig. 5), indicating that the effect of heparin on the
ability of BHV-1 to induce apoptosis is a specific phenomenon.
Altogether, these data provide strong evidence for the involvement of
viral attachment in the induction of apoptosis by BHV-1.
|
The observation that attachment, but not penetration, of BHV-1 is necessary to induce apoptosis in target cells provides important information about the mechanism by which BHV-1 induces apoptosis. Engagement of a cellular receptor by a BHV-1 envelope protein(s) during the attachment process could be responsible for induction of the apoptotic process in target cells. Similarly, in human immunodeficiency virus-infected patients, interaction of the soluble human immunodeficiency virus envelope protein gp120 with CD4 molecules is thought to induce a defective signal transduction that leads to apoptosis of the T-helper population (3, 13, 14, 30). In this context, to identify the BHV-1 envelope protein(s) which could be involved in the activation of the apoptotic process, we have already tested BHV-1 mutants with the gC, gI, gE, or gG gene deleted (kindly provided by F. A. M. Rijsewijk, Lelystad, The Netherlands) (27). These BHV-1 mutants are still able to induce apoptosis in PBMC and BL-3 cells (11a). Therefore, it seems most likely that glycoproteins gC, gE, gI, and gG are not involved in the induction of the apoptotic process. Among the other BHV-1 glycoproteins, gD could be a potential candidate for the induction of apoptosis. It has been shown that gD of herpes simplex virus type 1, another member of the subfamily Alphaherpesvirinae (28), interacts with a member of the tumor necrosis factor-nerve growth factor receptor family (24). These receptors are implicated in a variety of cellular functions, including proliferation, differentiation, and apoptosis (2). In addition, the expression of BHV-1 gD in bovine cells has been shown to be toxic (7, 17). On the basis of these observations, we are currently investigating the possible involvement of gD in BHV-1-induced apoptosis.
The involvement of a BHV-1 envelope protein(s) in the induction of apoptosis opens a new area of investigation. Following BHV-1 infection, the high susceptibility of infected animals to secondary bacterial infection has been shown to be associated with immunosuppression (4, 8). Even a modified live BHV-1 vaccine decreases the immune response against an antigen administrated simultaneously to animals (12). We previously reported that BHV-1 is able to induce apoptosis in T lymphocytes, B lymphocytes, and monocytes, which play an important role in the immune system (10). Subtle amino acid substitutions in a specific BHV-1 envelope protein(s) may eliminate the ability of BHV-1 to induce apoptosis and, presumably, the immunosuppression. This strategy could have important applications in the development of new, more effective, and safer vaccines and also help us to better understand the pathogenesis of BHV-1.
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ACKNOWLEDGMENTS |
|---|
We thank L. Willems (Gembloux, Belgium) and N. Vanderheijden (Liège, Belgium) for helpful comments on the manuscript and M. Loncar, L. Karelle-Bui Thi, J.-P. Georgin, and A. Brichaud for excellent technical assistance. We also thank J.-F. Bradfer for assistance with electron microscopy.
Purchase of the flow cytometer was supported in part by a grant (9.4505.92) from Loterie Nationale of Belgium. E. Hanon and A. Vanderplasschen are senior research assistants of the Fonds National Belge de la Recherche Scientifique.
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FOOTNOTES |
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* Corresponding author. Mailing address: Department of Immunology/Vaccinology, Faculty of Veterinary Medicine, University of Liège, B43bis, Boulevard de Colonster, 20, B-4000 Liège, Belgium. Phone: 32 4 366 42 65. Fax: 32 4 366 42 61. E-mail: hanon{at}stat.fmv.ulg.ac.be.
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REFERENCES |
|---|
|
|
|---|
| 1. | Arends, M. J., R. G. Morris, and A. H. Wyllie. 1990. Apoptosis. The role of the endonuclease. Am. J. Pathol. 136:593-608[Abstract]. |
| 2. | Baker, S. J., and E. P. Reddy. 1996. Transducers of life and death: TNF receptor superfamily and associated proteins. Oncogene 12:1-9[Medline]. |
| 3. |
Banda, N. K.,
J. Bernier,
D. K. Kurahara,
R. Kurrle,
N. Haigwood,
R. P. Sekaly, and T. H. Finkel.
1992.
Crosslinking CD4 by human immunodeficiency virus gp120 primes T cells for activation-induced apoptosis.
J. Exp. Med.
176:1099-1106 |
| 4. | Bielefeldt Ohmann, H., and L. A. Babiuk. 1985. Viral-bacterial pneumonia in calves: effect of bovine herpesvirus-1 on immunologic functions. J. Infect. Dis. 151:937-947[Medline]. |
| 5. | Byrne, K. M., D. W. Horohov, and K. G. Kousoulas. 1995. Glycoprotein B of bovine herpesvirus-1 binds heparin. Virology 209:230-235[Medline]. |
| 6. | Duvall, E., and A. H. Wyllie. 1986. Death and the cell. Immunol. Today 7:115-119. |
| 7. |
Fehler, F.,
J. M. Herrmann,
A. Saalmüller,
T. C. Mettenleiter, and G. M. Keil.
1992.
Glycoprotein IV of bovine herpesvirus 1-expressing cell line complements and rescues a conditionally lethal viral mutant.
J. Virol.
66:831-839 |
| 8. |
Filion, L. G.,
R. L. McGuire, and L. A. Babiuk.
1983.
Nonspecific suppressive effect of bovine herpesvirus type 1 on bovine leukocyte functions.
Infect. Immun.
42:106-112 |
| 9. | Hanon, E., S. Hoornaert, F. Dequiedt, A. Vanderplasschen, J. Lyaku, L. Willems, and P. P. Pastoret. 1997. Bovine herpesvirus 1-induced apoptosis occurs at the G0/G1 phase of the cell cycle. Virology 232:351-358[Medline]. |
| 10. | Hanon, E., M. Lambot, S. Hoornaert, J. Lyaku, and P. P. Pastoret. 1997. Bovine herpesvirus 1-induced apoptosis: phenotypic characterisation of susceptible peripheral blood mononuclear cells. Arch. Virol. 143:441-452. |
| 11. | Hanon, E., A. Vanderplasschen, J. R. Lyaku, G. Keil, M. Denis, and P. P. Pastoret. 1996. Inactivated bovine herpesvirus 1 induces apoptotic cell death of mitogen-stimulated bovine peripheral blood mononuclear cells. J. Virol. 70:4116-4120[Abstract]. |
| 11a. | Hanon, E., et al. Unpublished data. |
| 12. | Harland, R. J., A. A. Potter, S. van Drunen Littel-van den Hurk, J. van Donkersgoed, M. D. Parker, T. J. Zamb, and E. D. Janzen. 1992. The effect of subunit or modified live bovine herpesvirus-1 vaccines on the efficacy of a recombinant Pasteurella haemolytica vaccine for the prevention of respiratory disease in feedlot calves. Can. Vet. J. 33:734-741[Medline]. |
| 13. | Laurent-Crawford, A. G., E. Coccia, B. Krust, and A. G. Hovanessian. 1995. Membrane-expressed HIV envelope glycoprotein heterodimer is a powerful inducer of cell death in uninfected CD4+ target cells. Res. Virol. 146:5-17[Medline]. |
| 14. | Laurent-Crawford, A. G., B. Krust, S. Muller, Y. Riviere, M. A. Rey-Cuille, J. M. Bechet, L. Montagnier, and A. G. Hovanessian. 1991. The cytopathic effect of HIV is associated with apoptosis. Virology 185:829-839[Medline]. |
| 15. | Li, Y., X. Liang, S. van Drunen Littel-van den Hurk, S. Attah-Poku, and L. A. Babiuk. 1996. 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. J. Virol. 70:2032-2037[Abstract]. |
| 16. | Li, Y., S. van Drunen Littel-van den Hurk, L. A. Babiuk, and X. Liang. 1995. Characterization of cell-binding properties of bovine herpesvirus 1 glycoproteins B, C, and D: identification of a dual cell-binding function of gB. J. Virol. 69:4758-4768[Abstract]. |
| 17. | Liang, X., C. Pyne, Y. Li, L. A. Babiuk, and J. Kowalski. 1995. Delineation of the essential function of bovine herpesvirus 1 gD: an indication for the modulatory role of gD in virus entry. Virology 207:429-441[Medline]. |
| 18. |
Liang, X. P.,
L. A. Babiuk,
S. van Drunen Littel-van den Hurk,
D. R. Fitzpatrick, and T. J. Zamb.
1991.
Bovine herpesvirus 1 attachment to permissive cells is mediated by its major glycoproteins gI, gIII, and gIV.
J. Virol.
65:1124-1132 |
| 19. |
MacGregor, G. R., and C. T. Caskey.
1989.
Construction of plasmids that express E. coli beta-galactosidase in mammalian cells.
Nucleic Acids Res.
17:2365 |
| 20. | Martin, S. J., D. R. Green, and T. G. Cotter. 1994. Dicing with death: dissecting the components of the apoptosis machinery. Trends Biochem. Sci. 19:26-30[Medline]. |
| 21. | McChesney, M. B., and M. B. Oldstone. 1987. Viruses perturb lymphocyte functions: selected principles characterizing virus-induced immunosuppression. Annu. Rev. Immunol. 5:279-304[Medline]. |
| 22. | Meyer, G., E. Hanon, D. Georlette, P. P. Pastoret, and E. Thiry. 1998. Glycoprotein gH of bovine herpesvirus type 1 (BHV-1) is essential for penetration and propagation in cell culture. J. Gen. Virol. 79:1983-1987[Abstract]. |
| 23. |
Miethke, A.,
G. M. Keil,
F. Weiland, and T. C. Mettenleiter.
1995.
Unidirectional complementation between glycoprotein B homologues of pseudorabies virus and bovine herpesvirus 1 is determined by the carboxy-terminal part of the molecule.
J. Gen. Virol.
76:1623-1635 |
| 24. | Montgomery, R. I., M. S. Warner, B. J. Lum, and P. G. Spear. 1996. Herpes simplex virus-1 entry into cells mediated by a novel member of the TNF/NGF receptor family. Cell 87:427-436[Medline]. |
| 25. | Okazaki, K., E. Honda, and Y. Kono. 1994. Heparin-binding domain of bovid herpesvirus 1 glycoprotein gIII. Arch. Virol. 134:413-419[Medline]. |
| 26. | Razvi, E. S., and R. M. Welsh. 1995. Apoptosis in viral infections. Adv. Virus Res. 45:1-60[Medline]. |
| 27. | Rijsewijk, F. A., M. Kaashoek, G. Keil, H. Pall, R. Ruuls, F. A. van Engelenburg, and J. T. van Oirschot. 1995. In vitro and in vivo role of the nonessential glycoproteins gC, gG, gI and gE of bovine herpesvirus 1, p. 27. In Abstracts of the Symposium on IBR and Other Ruminant Herpesvirus Infections. European Society for Veterinary Virology. Sart-Tilman, Liège, Belgium. |
| 28. | Roizman, B., R. C. Desrosiers, B. Fleckenstein, C. Lopez, A. C. Minson, and M. J. Studdert. 1992. The family Herpesviridae: an update. The Herpesvirus Study Group of the International Committee on Taxonomy of Viruses. Arch. Virol. 123:425-449[Medline]. |
| 29. | Schröder, C., G. Linde, F. Fehler, and G. M. Keil. 1997. From essential to beneficial: glycoprotein D loses importance for replication of bovine herpesvirus 1 in cell culture. J. Virol. 71:25-33[Abstract]. |
| 30. | Schwartz, O., M. Alizon, J. M. Heard, and O. Danos. 1994. Impairment of T cell receptor-dependent stimulation in CD4+ lymphocytes after contact with membrane-bound HIV-1 envelope glycoprotein. Virology 198:360-365[Medline]. |
| 31. | Spear, P. G. 1993. Entry of alphaherpesviruses into cells. Semin. Virol. 4:167-180. |
| 32. |
Thompson, C. B.
1995.
Apoptosis in the pathogenesis and treatment of disease.
Science
267:1456-1462 |
| 33. | Tikoo, S. K., M. Campos, and L. A. Babiuk. 1995. Bovine herpesvirus 1 (BHV-1): biology, pathogenesis, and control. Adv. Virus Res. 45:191-223[Medline]. |
| 34. |
van Drunen Littel-van den Hurk, S.,
S. Khattar,
S. K. Tikoo,
L. A. Babiuk,
E. Baranowski,
D. Plainchamp, and E. Thiry.
1996.
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.
J. Gen. Virol.
77:1515-1520 |
| 35. | Wyllie, A. H. 1980. Glucocorticoid-induced thymocyte apoptosis is associated with endogenous endonuclease activation. Nature 284:555-556[Medline]. |
| 36. | Yates, W. D. 1982. A review of infectious bovine rhinotracheitis, shipping fever pneumonia and viral-bacterial synergism in respiratory disease of cattle. Can. J. Comp. Med. 46:225-263[Medline]. |
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