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Latent infections by herpes simplex virus in experimental animals
SURVEY OF OPHTHALMOLOGY
VOLUME 21
l
NUMBER 2
l
SEPTEMBER-OCTOBER
1976
Latent Infections by Herpes Simplex Virus in Experimental
JACK G. STEVENS, D.V.M.,
Animals
PH.D.
The Reed Neurological California
Research
Center,
University of California, Los Angeles,
Abstract. Studies in experimental
animals, initially the rabbit and more recently the mouse, have been of great importance in establishing present day concepts concerning the phenomenon of herpesvirus latency. These early observations coupled with
more recent knowledge of virological consequences following surgical manipulation of the trigeminal tract have led to a general hypothesis for the natural history of herpetic infections: The infection follows a circuit from skin, mucous membrane, or eye (the primary infection) to the corresponding sensory ganglia via associated nerves. Virus becomes latent in the ganglia and later, as a result of one of the many provocations known to be associated with recurrence of herpetic lesions, is reactivated and travels via the nerve to the surface and again produces lesions. Current research investigating this hypothesis is reviewed. (Surv Ophthalmol 21:175-177, 1976) Key words. herpes simplex virus reactivation of virus - rabbit *
l
latent infection mouse
S
tudies in experimental animals, initially the rabbit and more recently the mouse, have been of great importance in establishing concepts concerning the phenomenon of herpesvirus latency.
Early Experimental Work Griiter” and then Li3wensteiP concluded the first serious experimental studies of herpetic disease when they reported the successful induction of herpetic keratitis in rabbits. This finding led immediately to the observation that nervous symptoms sometimes developed in rabbits with herpetic eye disease5-s and prompted the now classic studies carried out over the next ten-year period by Goodpasture and Teague. The latter experiments were among the most important in establishing present knowledge concerning the pathogenesis of both primary and recurrent herpetic disease. To summarize, experiments in which the virus was injected into various peripheral sites all indi175
l
cated that resultant disease in the central nervous system was induced by a virus traveling in nerves from the periphery.‘O Later, Goodpasture suggested that the most likely intraneuronal route taken was an axonal one,’ and transmission experiments in which noninfected animals were housed with those presenting keratitis indicated that the natural infection involved a port of entry through mucosa of the mouth, nose, and throat.’ The experimental results obtained in rabbits coupled with previous clinical observations in mans,‘.12’lS led Goodpasture to an amazingly accurate conclusion:g
It seems to me probable from experimental and clinical facts that herpetic virus does reside in the latent state within the human body and specifically in the nervous tissues, perhaps primarily within nerve cells of the ganglia, and that neural disturbances are frequently the basis for subsequent outbreaks. From these considerations, it is clear that from the beginning, experimental studies in
176
Surv Ophtholmol 21 (2) September-October 1976
rabbits were instrumental in establishing basic concepts involving the natural history of herpetic disease. In subsequent years, these early observations and observations of virological consequences following surgical manipulation of the trigeminal tract have led to a general hypothesis which explains the natural history of herpetic infections. The infection is postulated to follow a circuit from skin, mucous membrane, or eye (the primary infection) to the corresponding sensory ganglia via associated nerves. Virus then becomes latent in the ganglia and later, as a result of one of the many provocations known to be associated with recurrence of herpetic lesions, is reactivated, travels via the nerve to the surface and again produces lesions.
STEVENS
early experiments of Goodpasture have been confirmed by more quantitative studies in which different portions of the nervous system and other tissues were assayed for virus at different times after inoculation of the mouse footpad.**** The data derived from such studies show that there is a centripetal progression of virus from the footpad through the peripheral and central nervous systems to the brain. Evidence that the virus travels centrifugally from the ganglion has also been obtained. In these experimentsZo virus was reactivated in ganglia by a superimposed pneumococcal pneumonia, and traveled in associated nerves. Finally, it seems quite likely that the intraneuronal route taken by virus in travel between sites is an axonal one. The evidence supporting this conclusion is inRecent Experimental Work direct, but relates chiefly to the speed with In our laboratories, with the mouse used as which the infection moves in nerves even in the principal experimental animal, nearly all the presence of antiviral antibody.* Although reactivation of active infection aspects of the general hypothesis for the natural history of recurrent herpetic disease following a defined manipulation has been achave been substantiated, and much of the complished in the mouse, the subsequent work has been confirmed in other systems. appearance of lesions or clinically apparent However, reactivated virus has not yet been disease has not yet been shown to occur. In shown to produce clinically apparent lesions our own laboratory, an intensive study of or disease in the mouse or in any other experi- reactivation was begun soon after we had mental animal. Some four years ago, we found that latent infections could be esmade the initial demonstration that latent in- tablished. Although our earlier experiences fections are established in sensory ganglia were disappointing, as indicated above we are following infection of the externa. It was now able (by imposition of a severe pneumoshown that mice inoculated with virus in a coccal pneumonia) to reactivate virus from rear footpad harbored latent virus in sacro- latently infected ganglia. In addition, the sciatic spinal ganglia, probably for the life of agent then moves both proximally and disthe mouse.17 In those experiments, latent tally in associate nerves?O In other experivirus was reactivated when the ganglia were ments involving the mouse, Walz et al.*l were able to reactivate virus in latently infected explanted and maintained as organized tissues in vitro. Later, we and others found lumbo-sacral sensory ganglia by sectioning that other sensory ganglia in the mouse, the branches of the sciatic nerve at the point from rabbit and the guinea pig could be latently in- which they exited intervertebral foramina. system described by fected when various surface areas of the ani- The experimental Nesburn (see p. 185) is possibly the best yet mals had been inoculated with virus.14+18*1**21 Most important, when the techniques were described. Here, physical trauma applied to applied to appropriate human tissues, latent latently infected trigeminal ganglia in rabbits resulted in the subsequent appearance of virus infections were also detected (see Baringer, page 171). The results of subsequent experi- in the tear film. ments suggest that the latent virus is assoConclusions and Extensions ciated with neurons and maintained in a From these considerations, it is clear that nonreplicating state modulated by specific immune IgG.l~lB Whether the viral DNA is all aspects of the general hypothesis for integrated in the cellular chromosome is now natural history of recurrent herpetic disease under intensive investigation in our labora- except for reappearance of clinical disease following a defined manipulation have been tories. That the virus travels in nerves seems now substantiated in experimental animals. If, in to have been convincingly established. The the future, clinically apparent disease can be
LATENT INFECTIONS BY HSV IN EXPERIMENTAL ANIMALS
induced and surgical interruption of appropriate nerves prevents the phenomenon, then the general hypothesis will have complete experimental support. However, the biochemical basis of latency and reactivation is unknown. We are now attempting to approach this aspect (i.e., the intracellular phenomena which follow the interaction of infected neurons with antiviral antibody) through the use of temperature sensitive viral mutants with defined biochemical phenotypes employed in the mouse.
References 1. Cook ML, Stevens JG: Evidence that neurons harbor latent Herpes simplex virus. Infect Immun 9:946-951, 1974 2. Cook ML, Stevens JG: Pathogenesis of herpetic neuritis and ganglionitis in mice: Evidence for intra-axonal transport of infection. Infect Immun 7:272-288, 1973 3. Cushing H: Perineal zoster. Bull Johns Hopkins Hosp 158:172, 1904 4. Cushing H: The surgical aspects of major neuralgia of the trigeminal nerve. A report of 20 cases of operation on the gasserian ganglion, with anatomic and physiologic notes on the consequences of its removal. J Am Med Assoc 44:773-779, 860-865, 920-929, 1002-1008, 1088-1093, 1905 5. Doerr R: Sitzungsberichte der Gesellschaft der schweizerischen Augenarzte. Diskussion. Klin Monatsbl Augenheilkd 65:104, 1920 6. Doerr R, Viichting K: Etudes sur le virus de l’herpes febrile. Rev gen Ophthalmol (Paris) 34:409-421, 1920 I. Goodpasture EW: The axis cylinders of peripheral nerves as portals of entry to the central nervous system for the virus of herpes simplex in experimentally infected rabbits. Am J Pathol 1:l l-28, 1925 8. Goodpasture EW: The pathways of infection of the central nervous system in herpetic encephalitis of rabbits contracted by contact, with a comparative comment on medullary lesions in a case of human poliomyelitis. Am J Pathol 1:29-46, 1925 9. Goodpasture EW: Herpetic infections with special reference to involvement of the nervous system. Medicine (Baltimore) 7:223-243, 1929 10. Goodpasture EW, Teague 0: Transmission of the virus of herpes fibrilis along nerves in experimentally infected rabbits. J Med Res 4l:139-184, 1923
177
und klinische 11. Grbter W: Experimentelle Untersuchungen uber den sog. Herpes corneae. Klin Monatshl Augenheilkd 65:398-399, 1920 12. Howard WT: The pathology of labial and nasal herpes and of herpes of the body occurring in acute croupous pneumonia and their relation to so-called herpes zoster. Am J Med Sci 125: 256-272, 1903 13. Howard WT: Further observations on the relation of lesions of the gasserian and posterior root ganglia to herpes occurring in pneumonia and cerebrospinal meningitis. Am J Med Sci 130: 1012-1019, 1905 14. Knotts FB, Cook ML, Stevens JG: Latent Herpes simplex virus in the central nervous system of rabbits and mice. J Exp Med 138:740-744, 1973 15. Liiwenstein A: Atiologische Untersuchnugen uber den fieberhaften Herpes. Munch Med Wochenschr 66:769-770, 1919 16. Scriba M: Herpes Simplex virus infection in guinea pigs: an animal model for studying latent and recurrent Herpes simplex virus infection. Infect Immun 12:162-165, 1975 17. Stevens JG, Cook ML: Latent Herpes simplex virus in spinal ganglia of mice. Science 173:843-845, 197 1 18. Stevens JG, Nesburn AB, Cook ML: Latent Herpes simplex virus from trigeminal ganglia of rabbits with recurrent eye infection. Nature [New Biol] 235:216-217, 1972 19. Stevens JG, Cook ML: Maintenance of latent herpetic infection: an apparent role for antiviral IgG. J Immunol 113:1685-1693, 1974 20. Stevens JG, Cook ML, Jordan MC: Reactivation of latent Herpes simplex virus following pneumococcal pneumonia in mice. Infect Immun 11:635-639, 1975 21. Walz MA, Price RW, Notkins AL: Latent infection with Herpes simplex virus types 1 and 2: viral reactivation in vivo after neurectomy. Science 184:1185-l 187, 1974 22. Wildy P: The progression of Herpes simplex virus to the central nervous system of the mouse. J Hyg 65:173-192, 1967 Supported by USPHS Grants AI-06246 and NS-08711. This article is taken in part from Stevens, JG: Latent Herpes Simplex Virus in the Nervous System. Curr Top Microbial Immunol 70:31-50, 1975. Reprint requests should be addressed to: Dr. Jack G. Stevens, The Reed Neurological Research Center, University of California, Los Angeles, California 90024.
VOLUME 21
l
NUMBER 2
l
SEPTEMBER-OCTOBER
1976
Latent Infections by Herpes Simplex Virus in Experimental
JACK G. STEVENS, D.V.M.,
Animals
PH.D.
The Reed Neurological California
Research
Center,
University of California, Los Angeles,
Abstract. Studies in experimental
animals, initially the rabbit and more recently the mouse, have been of great importance in establishing present day concepts concerning the phenomenon of herpesvirus latency. These early observations coupled with
more recent knowledge of virological consequences following surgical manipulation of the trigeminal tract have led to a general hypothesis for the natural history of herpetic infections: The infection follows a circuit from skin, mucous membrane, or eye (the primary infection) to the corresponding sensory ganglia via associated nerves. Virus becomes latent in the ganglia and later, as a result of one of the many provocations known to be associated with recurrence of herpetic lesions, is reactivated and travels via the nerve to the surface and again produces lesions. Current research investigating this hypothesis is reviewed. (Surv Ophthalmol 21:175-177, 1976) Key words. herpes simplex virus reactivation of virus - rabbit *
l
latent infection mouse
S
tudies in experimental animals, initially the rabbit and more recently the mouse, have been of great importance in establishing concepts concerning the phenomenon of herpesvirus latency.
Early Experimental Work Griiter” and then Li3wensteiP concluded the first serious experimental studies of herpetic disease when they reported the successful induction of herpetic keratitis in rabbits. This finding led immediately to the observation that nervous symptoms sometimes developed in rabbits with herpetic eye disease5-s and prompted the now classic studies carried out over the next ten-year period by Goodpasture and Teague. The latter experiments were among the most important in establishing present knowledge concerning the pathogenesis of both primary and recurrent herpetic disease. To summarize, experiments in which the virus was injected into various peripheral sites all indi175
l
cated that resultant disease in the central nervous system was induced by a virus traveling in nerves from the periphery.‘O Later, Goodpasture suggested that the most likely intraneuronal route taken was an axonal one,’ and transmission experiments in which noninfected animals were housed with those presenting keratitis indicated that the natural infection involved a port of entry through mucosa of the mouth, nose, and throat.’ The experimental results obtained in rabbits coupled with previous clinical observations in mans,‘.12’lS led Goodpasture to an amazingly accurate conclusion:g
It seems to me probable from experimental and clinical facts that herpetic virus does reside in the latent state within the human body and specifically in the nervous tissues, perhaps primarily within nerve cells of the ganglia, and that neural disturbances are frequently the basis for subsequent outbreaks. From these considerations, it is clear that from the beginning, experimental studies in
176
Surv Ophtholmol 21 (2) September-October 1976
rabbits were instrumental in establishing basic concepts involving the natural history of herpetic disease. In subsequent years, these early observations and observations of virological consequences following surgical manipulation of the trigeminal tract have led to a general hypothesis which explains the natural history of herpetic infections. The infection is postulated to follow a circuit from skin, mucous membrane, or eye (the primary infection) to the corresponding sensory ganglia via associated nerves. Virus then becomes latent in the ganglia and later, as a result of one of the many provocations known to be associated with recurrence of herpetic lesions, is reactivated, travels via the nerve to the surface and again produces lesions.
STEVENS
early experiments of Goodpasture have been confirmed by more quantitative studies in which different portions of the nervous system and other tissues were assayed for virus at different times after inoculation of the mouse footpad.**** The data derived from such studies show that there is a centripetal progression of virus from the footpad through the peripheral and central nervous systems to the brain. Evidence that the virus travels centrifugally from the ganglion has also been obtained. In these experimentsZo virus was reactivated in ganglia by a superimposed pneumococcal pneumonia, and traveled in associated nerves. Finally, it seems quite likely that the intraneuronal route taken by virus in travel between sites is an axonal one. The evidence supporting this conclusion is inRecent Experimental Work direct, but relates chiefly to the speed with In our laboratories, with the mouse used as which the infection moves in nerves even in the principal experimental animal, nearly all the presence of antiviral antibody.* Although reactivation of active infection aspects of the general hypothesis for the natural history of recurrent herpetic disease following a defined manipulation has been achave been substantiated, and much of the complished in the mouse, the subsequent work has been confirmed in other systems. appearance of lesions or clinically apparent However, reactivated virus has not yet been disease has not yet been shown to occur. In shown to produce clinically apparent lesions our own laboratory, an intensive study of or disease in the mouse or in any other experi- reactivation was begun soon after we had mental animal. Some four years ago, we found that latent infections could be esmade the initial demonstration that latent in- tablished. Although our earlier experiences fections are established in sensory ganglia were disappointing, as indicated above we are following infection of the externa. It was now able (by imposition of a severe pneumoshown that mice inoculated with virus in a coccal pneumonia) to reactivate virus from rear footpad harbored latent virus in sacro- latently infected ganglia. In addition, the sciatic spinal ganglia, probably for the life of agent then moves both proximally and disthe mouse.17 In those experiments, latent tally in associate nerves?O In other experivirus was reactivated when the ganglia were ments involving the mouse, Walz et al.*l were able to reactivate virus in latently infected explanted and maintained as organized tissues in vitro. Later, we and others found lumbo-sacral sensory ganglia by sectioning that other sensory ganglia in the mouse, the branches of the sciatic nerve at the point from rabbit and the guinea pig could be latently in- which they exited intervertebral foramina. system described by fected when various surface areas of the ani- The experimental Nesburn (see p. 185) is possibly the best yet mals had been inoculated with virus.14+18*1**21 Most important, when the techniques were described. Here, physical trauma applied to applied to appropriate human tissues, latent latently infected trigeminal ganglia in rabbits resulted in the subsequent appearance of virus infections were also detected (see Baringer, page 171). The results of subsequent experi- in the tear film. ments suggest that the latent virus is assoConclusions and Extensions ciated with neurons and maintained in a From these considerations, it is clear that nonreplicating state modulated by specific immune IgG.l~lB Whether the viral DNA is all aspects of the general hypothesis for integrated in the cellular chromosome is now natural history of recurrent herpetic disease under intensive investigation in our labora- except for reappearance of clinical disease following a defined manipulation have been tories. That the virus travels in nerves seems now substantiated in experimental animals. If, in to have been convincingly established. The the future, clinically apparent disease can be
LATENT INFECTIONS BY HSV IN EXPERIMENTAL ANIMALS
induced and surgical interruption of appropriate nerves prevents the phenomenon, then the general hypothesis will have complete experimental support. However, the biochemical basis of latency and reactivation is unknown. We are now attempting to approach this aspect (i.e., the intracellular phenomena which follow the interaction of infected neurons with antiviral antibody) through the use of temperature sensitive viral mutants with defined biochemical phenotypes employed in the mouse.
References 1. Cook ML, Stevens JG: Evidence that neurons harbor latent Herpes simplex virus. Infect Immun 9:946-951, 1974 2. Cook ML, Stevens JG: Pathogenesis of herpetic neuritis and ganglionitis in mice: Evidence for intra-axonal transport of infection. Infect Immun 7:272-288, 1973 3. Cushing H: Perineal zoster. Bull Johns Hopkins Hosp 158:172, 1904 4. Cushing H: The surgical aspects of major neuralgia of the trigeminal nerve. A report of 20 cases of operation on the gasserian ganglion, with anatomic and physiologic notes on the consequences of its removal. J Am Med Assoc 44:773-779, 860-865, 920-929, 1002-1008, 1088-1093, 1905 5. Doerr R: Sitzungsberichte der Gesellschaft der schweizerischen Augenarzte. Diskussion. Klin Monatsbl Augenheilkd 65:104, 1920 6. Doerr R, Viichting K: Etudes sur le virus de l’herpes febrile. Rev gen Ophthalmol (Paris) 34:409-421, 1920 I. Goodpasture EW: The axis cylinders of peripheral nerves as portals of entry to the central nervous system for the virus of herpes simplex in experimentally infected rabbits. Am J Pathol 1:l l-28, 1925 8. Goodpasture EW: The pathways of infection of the central nervous system in herpetic encephalitis of rabbits contracted by contact, with a comparative comment on medullary lesions in a case of human poliomyelitis. Am J Pathol 1:29-46, 1925 9. Goodpasture EW: Herpetic infections with special reference to involvement of the nervous system. Medicine (Baltimore) 7:223-243, 1929 10. Goodpasture EW, Teague 0: Transmission of the virus of herpes fibrilis along nerves in experimentally infected rabbits. J Med Res 4l:139-184, 1923
177
und klinische 11. Grbter W: Experimentelle Untersuchungen uber den sog. Herpes corneae. Klin Monatshl Augenheilkd 65:398-399, 1920 12. Howard WT: The pathology of labial and nasal herpes and of herpes of the body occurring in acute croupous pneumonia and their relation to so-called herpes zoster. Am J Med Sci 125: 256-272, 1903 13. Howard WT: Further observations on the relation of lesions of the gasserian and posterior root ganglia to herpes occurring in pneumonia and cerebrospinal meningitis. Am J Med Sci 130: 1012-1019, 1905 14. Knotts FB, Cook ML, Stevens JG: Latent Herpes simplex virus in the central nervous system of rabbits and mice. J Exp Med 138:740-744, 1973 15. Liiwenstein A: Atiologische Untersuchnugen uber den fieberhaften Herpes. Munch Med Wochenschr 66:769-770, 1919 16. Scriba M: Herpes Simplex virus infection in guinea pigs: an animal model for studying latent and recurrent Herpes simplex virus infection. Infect Immun 12:162-165, 1975 17. Stevens JG, Cook ML: Latent Herpes simplex virus in spinal ganglia of mice. Science 173:843-845, 197 1 18. Stevens JG, Nesburn AB, Cook ML: Latent Herpes simplex virus from trigeminal ganglia of rabbits with recurrent eye infection. Nature [New Biol] 235:216-217, 1972 19. Stevens JG, Cook ML: Maintenance of latent herpetic infection: an apparent role for antiviral IgG. J Immunol 113:1685-1693, 1974 20. Stevens JG, Cook ML, Jordan MC: Reactivation of latent Herpes simplex virus following pneumococcal pneumonia in mice. Infect Immun 11:635-639, 1975 21. Walz MA, Price RW, Notkins AL: Latent infection with Herpes simplex virus types 1 and 2: viral reactivation in vivo after neurectomy. Science 184:1185-l 187, 1974 22. Wildy P: The progression of Herpes simplex virus to the central nervous system of the mouse. J Hyg 65:173-192, 1967 Supported by USPHS Grants AI-06246 and NS-08711. This article is taken in part from Stevens, JG: Latent Herpes Simplex Virus in the Nervous System. Curr Top Microbial Immunol 70:31-50, 1975. Reprint requests should be addressed to: Dr. Jack G. Stevens, The Reed Neurological Research Center, University of California, Los Angeles, California 90024.