Biomedical subjects

Brian P Schlitt

Publications and source records attributed to Brian P Schlitt.

6 recordsLinked to original sources

PubMed2004

Susceptibility of peritoneal macrophages to infection by Theiler's virus.

Theiler's murine encephalomyelitis virus (TMEV) strains fall into two groups: high-neurovirulence GDVII virus results in rapidly fatal encephalitis, while low-neurovirulence BeAn and DA viruses produce persistent central nervous system (CNS) infection and inflammatory demyelinating disease. Because macrophages (Mphis) are key components in BeAn virus-induced demyelinating disease, we examined the susceptibility of primary peritoneal macrophages (pMphis) to BeAn infection in vitro. Freshly isolated, thioglycollate-elicited pMphis were resistant to BeAn virus infection even at high multiplicity of infection. In contrast, after incubation of thioglycollate-elicited pMphis at 37 degrees C for 4 days before infection, approximately half of the cells expressed virus antigen(s) and contained nicked DNA indicative of apoptosis. However, BeAn virus RNA replication and virus yields were highly restricted. Interestingly, about one-third of the cells were apoptotic but negative for virus RNA and antigen(s). Tumor necrosis factor-alpha (TNF-alpha) and interferon-alpha (IFN-alpha) were elevated in BeAn-infected pMphi cultures suggesting that bystander killing may be responsible for the apoptosis seen in BeAn virus antigen-negative cells. These data show for the first time that pMphis are susceptible to BeAn virus infection, although the infection is highly restricted and most of these cells undergo BeAn-induced apoptosis.

Animals↗

PubMed2004

Heparan sulfate-independent infection attenuates high-neurovirulence GDVII virus-induced encephalitis.

The high-neurovirulence Theiler's murine encephalomyelitis virus (TMEV) strain GDVII uses heparan sulfate (HS) as a coreceptor to enter target cells. We report here that GDVII virus adapted to growth in HS-deficient cells exhibited two amino acid substitutions (R3126L and N1051S) in the capsid and no longer used HS as a coreceptor. Infectious-virus yields in CHO cells were 25-fold higher for the adapted virus than for the parental GDVII virus, and the neurovirulence of the adapted virus in intracerebrally inoculated mice was substantially attenuated. The adapted virus showed altered cell tropism in the central nervous systems of mice, shifting from cerebral and brainstem neurons to spinal cord anterior horn cells; thus, severe poliomyelitis, but not acute encephalitis, was observed in infected mice. These data indicate that the use of HS as a coreceptor by GDVII virus facilitates cell entry and plays an important role in cell tropism and neurovirulence in vivo.

Amino Acid Substitution↗

PubMed2004

Transition from acute to persistent Theiler's virus infection requires active viral replication that drives proinflammatory cytokine expression and chronic demyelinating disease.

The dynamics of Theiler's murine encephalomyelitis virus (TMEV) RNA replication in the central nervous systems of susceptible and resistant strains of mice were examined by quantitative real-time reverse transcription-PCR and were found to correlate with host immune responses. During the acute phase of infection in both susceptible and resistant mice, levels of viral replication were high in the brain and brain stem, while levels of viral genome equivalents were 10- to 100-fold lower in the spinal cord. In the brain, viral RNA replication decreased after a peak at 5 days postinfection (p.i.), in parallel with the appearance of virus-specific antibody responses; however, by 15 days p.i., viral RNA levels began to increase in the spinal cords of susceptible mice. During the transition to and the persistent phase of infection, the numbers of viral genome equivalents in the spinal cord varied substantially for individual mice, but high levels were consistently associated with high levels of proinflammatory Th1 cytokine and chemokine mRNAs. Moreover, a large number of viral genome equivalents and high proinflammatory cytokine mRNA levels in spinal cords were only observed for susceptible SJL/J mice who developed demyelinating disease. These results suggest that TMEV persistence requires active viral replication beginning about day 11 p.i. and that active viral replication with high viral genome loads leads to increased levels of Th1 cytokines that drive disease progression in infected mice.

Animals↗

PubMed2003

Apoptotic cells, including macrophages, are prominent in Theiler's virus-induced inflammatory, demyelinating lesions.

Theiler's murine encephalomyelitis virus (TMEV) persists in the mouse central nervous system principally in macrophages, and infected macrophages in culture undergo apoptosis. We have detected abundant apoptotic cells in perivascular cuffs and inflammatory, demyelinating lesions of SJL mice chronically infected with TMEV. T cells comprised 74% of apoptotic cells, while 8% were macrophages, 0.6% were astrocytes, and approximately 17% remained unidentified. In situ hybridization revealed viral RNA in approximately 1% of apoptotic cells.

Animals↗

PubMed2002

Theiler's virus.

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Animals↗

PubMed2002

Enhanced detection of Theiler's virus RNA copy equivalents in the mouse central nervous system by real-time RT-PCR.

Infection of mice by low-neurovirulence Theiler's murine encephalomyelitis virus (TMEV), such as BeAn and DA viruses, provides a relevant experimental animal model for multiple sclerosis (MS). As a step toward determining the kinetics of a persistent central nervous system (CNS) infection that leads to chronic demyelination, we adapted a rapid, accurate and highly specific real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay for detection and quantitation of BeAn virus RNA copy equivalents in mouse tissues. The assay enabled detection of as few as 20-30 copies of BeAn virus RNA per microg of total RNA from infected mouse tissues and results for spinal cord revealed the same high levels of BeAn RNA as detected by Northern hybridization during the first 4 months of the persistent infection, but also was able to detect virus RNA copies as late as 1 year post-infection. Real-time RT-PCR analysis of BeAn virus RNA copy equivalents in different parts of the CNS, analyses not possible by Northern hybridization, revealed the following cline of virus persistence: spinal cord>brainstem/cerebellum>cerebrospinal fluid (CSF)>cerebral hemispheres. Systemic organs, including heart, intestine and mesenteric lymph nodes of infected mice, showed no evidence of viral persistence at 4 months post-infection.

Animals↗