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Intravenous inoculation of a bat-associated rabies virus causes lethal encephalopathy in mice through invasion of the brain via neurosecretory hypothalamic fibers.

Preuss MA, Faber ML, Tan GS, Bette M, Dietzschold B, Weihe E, Schnell MJ - PLoS Pathog. (2009)

Bottom Line: To determine whether certain RV variants might have the capacity to invade the CNS from the periphery via hematogenous spread, we infected mice either intramuscularly (i.m.) or intravenously (i.v.) with the dog-associated RV DOG4 or the silver-haired bat-associated RV SB.The earliest affected regions were those hypothalamic nuclei, which are connected by neurosecretory fibers to the circumventricular organs neurohypophysis and median eminence.Our data suggest that hematogenous spread of SB can lead to a fatal encephalopathy through direct retrograde invasion of the CNS at the neurovascular interface of the hypothalamus-hypophysis system.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Neuroscience, Institute of Anatomy and Cell Biology, Philipps University Marburg, Marburg, Germany.

ABSTRACT
The majority of rabies virus (RV) infections are caused by bites or scratches from rabid carnivores or bats. Usually, RV utilizes the retrograde transport within the neuronal network to spread from the infection site to the central nervous system (CNS) where it replicates in neuronal somata and infects other neurons via trans-synaptic spread. We speculate that in addition to the neuronal transport of the virus, hematogenous spread from the site of infection directly to the brain after accidental spill over into the vascular system might represent an alternative way for RV to invade the CNS. So far, it is unknown whether hematogenous spread has any relevance in RV pathogenesis. To determine whether certain RV variants might have the capacity to invade the CNS from the periphery via hematogenous spread, we infected mice either intramuscularly (i.m.) or intravenously (i.v.) with the dog-associated RV DOG4 or the silver-haired bat-associated RV SB. In addition to monitoring the progression of clinical signs of rabies we used immunohistochemistry and quantitative reverse transcription polymerase chain reaction (qRT-PCR) to follow the spread of the virus from the infection site to the brain. In contrast to i.m. infection where both variants caused a lethal encephalopathy, only i.v. infection with SB resulted in the development of a lethal infection. While qRT-PCR did not reveal major differences in virus loads in spinal cord or brain at different times after i.m. or i.v. infection of SB, immunohistochemical analysis showed that only i.v. administered SB directly infected the forebrain. The earliest affected regions were those hypothalamic nuclei, which are connected by neurosecretory fibers to the circumventricular organs neurohypophysis and median eminence. Our data suggest that hematogenous spread of SB can lead to a fatal encephalopathy through direct retrograde invasion of the CNS at the neurovascular interface of the hypothalamus-hypophysis system. This alternative mode of virus spread has implications for the post exposure prophylaxis of rabies, particularly with silver-haired bat-associated RV.

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Viral Burden in the CNS after SB i.m. or i.v. Inoculation.Twelve mice were infected i.m. or i.v. with 5×106 ffu of SB. Three mice per group were euthanized at each indicated time point and the number of RV genome equivalents per microgram total RNA isolated from spinal cord (A) and brain (B) was quantified by qRT-PCR. Data are mean RNA copy numbers (+standard error) calculated for three mice per time point. Asterisks indicate significant differences in the virus load at the indicated time point in dependence on the inoculation route (*, p<0.05).
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ppat-1000485-g004: Viral Burden in the CNS after SB i.m. or i.v. Inoculation.Twelve mice were infected i.m. or i.v. with 5×106 ffu of SB. Three mice per group were euthanized at each indicated time point and the number of RV genome equivalents per microgram total RNA isolated from spinal cord (A) and brain (B) was quantified by qRT-PCR. Data are mean RNA copy numbers (+standard error) calculated for three mice per time point. Asterisks indicate significant differences in the virus load at the indicated time point in dependence on the inoculation route (*, p<0.05).

Mentions: In order to analyze the migration pathways after i.v. and i.m. SB infection, the virus load in brain and spinal cord was monitored by qRT-PCR and immunohistochemical analysis. RNA from spinal cord and brain tissue was harvested from mice early after inoculation (2 hours post infection), before the onset of symptoms (2 days post infection), at the beginning of weight loss (5 days post infection) and in the progressed stage of disease (7 days post infection) and analyzed for SB genomic equivalents (Figure 4A and 4B). After i.m. inoculation, genomic SB RNA was detectable in the spinal cord in fairly low amounts only at day 2 post infection, but the virus load rapidly increased over more than six logs within the following three days (Figure 4A). In the brain, genomic SB RNA was detectable in higher concentrations only at day 5 post infection, but in very low amounts also at day 2 and even already 2 hours post infection (Figure 4B). The latter finding supported our working hypothesis that spill over of virus into the vascular system and spread throughout the whole organism can occur after i.m. inoculation. In comparison, after i.v. inoculation SB RNA was detectable in significantly (spinal cord, p<0.05) or slightly (brain) higher amounts especially at the early time points, whereas the amplification slope from the day of infection to day 7 post infection was significantly steeper in the CNS of i.m. inoculated mice (p<0.05); this became particularly noticeable at day 5 post infection in both CNS segments.


Intravenous inoculation of a bat-associated rabies virus causes lethal encephalopathy in mice through invasion of the brain via neurosecretory hypothalamic fibers.

Preuss MA, Faber ML, Tan GS, Bette M, Dietzschold B, Weihe E, Schnell MJ - PLoS Pathog. (2009)

Viral Burden in the CNS after SB i.m. or i.v. Inoculation.Twelve mice were infected i.m. or i.v. with 5×106 ffu of SB. Three mice per group were euthanized at each indicated time point and the number of RV genome equivalents per microgram total RNA isolated from spinal cord (A) and brain (B) was quantified by qRT-PCR. Data are mean RNA copy numbers (+standard error) calculated for three mice per time point. Asterisks indicate significant differences in the virus load at the indicated time point in dependence on the inoculation route (*, p<0.05).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2691950&req=5

ppat-1000485-g004: Viral Burden in the CNS after SB i.m. or i.v. Inoculation.Twelve mice were infected i.m. or i.v. with 5×106 ffu of SB. Three mice per group were euthanized at each indicated time point and the number of RV genome equivalents per microgram total RNA isolated from spinal cord (A) and brain (B) was quantified by qRT-PCR. Data are mean RNA copy numbers (+standard error) calculated for three mice per time point. Asterisks indicate significant differences in the virus load at the indicated time point in dependence on the inoculation route (*, p<0.05).
Mentions: In order to analyze the migration pathways after i.v. and i.m. SB infection, the virus load in brain and spinal cord was monitored by qRT-PCR and immunohistochemical analysis. RNA from spinal cord and brain tissue was harvested from mice early after inoculation (2 hours post infection), before the onset of symptoms (2 days post infection), at the beginning of weight loss (5 days post infection) and in the progressed stage of disease (7 days post infection) and analyzed for SB genomic equivalents (Figure 4A and 4B). After i.m. inoculation, genomic SB RNA was detectable in the spinal cord in fairly low amounts only at day 2 post infection, but the virus load rapidly increased over more than six logs within the following three days (Figure 4A). In the brain, genomic SB RNA was detectable in higher concentrations only at day 5 post infection, but in very low amounts also at day 2 and even already 2 hours post infection (Figure 4B). The latter finding supported our working hypothesis that spill over of virus into the vascular system and spread throughout the whole organism can occur after i.m. inoculation. In comparison, after i.v. inoculation SB RNA was detectable in significantly (spinal cord, p<0.05) or slightly (brain) higher amounts especially at the early time points, whereas the amplification slope from the day of infection to day 7 post infection was significantly steeper in the CNS of i.m. inoculated mice (p<0.05); this became particularly noticeable at day 5 post infection in both CNS segments.

Bottom Line: To determine whether certain RV variants might have the capacity to invade the CNS from the periphery via hematogenous spread, we infected mice either intramuscularly (i.m.) or intravenously (i.v.) with the dog-associated RV DOG4 or the silver-haired bat-associated RV SB.The earliest affected regions were those hypothalamic nuclei, which are connected by neurosecretory fibers to the circumventricular organs neurohypophysis and median eminence.Our data suggest that hematogenous spread of SB can lead to a fatal encephalopathy through direct retrograde invasion of the CNS at the neurovascular interface of the hypothalamus-hypophysis system.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Neuroscience, Institute of Anatomy and Cell Biology, Philipps University Marburg, Marburg, Germany.

ABSTRACT
The majority of rabies virus (RV) infections are caused by bites or scratches from rabid carnivores or bats. Usually, RV utilizes the retrograde transport within the neuronal network to spread from the infection site to the central nervous system (CNS) where it replicates in neuronal somata and infects other neurons via trans-synaptic spread. We speculate that in addition to the neuronal transport of the virus, hematogenous spread from the site of infection directly to the brain after accidental spill over into the vascular system might represent an alternative way for RV to invade the CNS. So far, it is unknown whether hematogenous spread has any relevance in RV pathogenesis. To determine whether certain RV variants might have the capacity to invade the CNS from the periphery via hematogenous spread, we infected mice either intramuscularly (i.m.) or intravenously (i.v.) with the dog-associated RV DOG4 or the silver-haired bat-associated RV SB. In addition to monitoring the progression of clinical signs of rabies we used immunohistochemistry and quantitative reverse transcription polymerase chain reaction (qRT-PCR) to follow the spread of the virus from the infection site to the brain. In contrast to i.m. infection where both variants caused a lethal encephalopathy, only i.v. infection with SB resulted in the development of a lethal infection. While qRT-PCR did not reveal major differences in virus loads in spinal cord or brain at different times after i.m. or i.v. infection of SB, immunohistochemical analysis showed that only i.v. administered SB directly infected the forebrain. The earliest affected regions were those hypothalamic nuclei, which are connected by neurosecretory fibers to the circumventricular organs neurohypophysis and median eminence. Our data suggest that hematogenous spread of SB can lead to a fatal encephalopathy through direct retrograde invasion of the CNS at the neurovascular interface of the hypothalamus-hypophysis system. This alternative mode of virus spread has implications for the post exposure prophylaxis of rabies, particularly with silver-haired bat-associated RV.

Show MeSH
Related in: MedlinePlus