Experimental encephalitis in the newborn rat due to herpes simplex virus type 2

APOBEC1-mediated editing and attenuation of herpes simplex virus 1 DNA indicate that neurons have an antiviral role during herpes simplex encephalitis

APOBEC1 (A1) is a cytidine deaminase involved in the regulation of lipids in the small intestine. Herpes simplex virus 1 (HSV-1) is a ubiquitous pathogen that is capable of infecting neurons in the brain, causing encephalitis. Here, we show that A1 is induced during encephalitis in neurons of rats infected with HSV-1. In cells stably expressing A1, HSV-1 infection resulted in significantly reduced virus replication compared to that in control cells. Infectivity could be restored to levels comparable to those observed for control cells if A1 expression was silenced by specific A1 short hairpin RNAs (shRNA). Moreover, cytidine deaminase activity appeared to be essential for this inhibition and led to an impaired accumulation of viral mRNA transcripts and DNA copy numbers. The sequencing of viral gene UL54 DNA, extracted from infected A1-expressing cells, revealed G-to-A and C-to-T transitions, indicating that A1 associates with HSV-1 DNA. Taken together, our results demonstrate a model in which A1 induction during encephalitis in neurons may aid in thwarting HSV-1 infection.

Topography of remyelinated chronic spinal cord lesions in herpes simplex virus type 2 infections of mice

Six-week-old outbred mice were infected intracerebrally with a low dose of the MS strain of herpes simplex virus type 2. About 1% of neurologically abnormal survivors developed paralysis or severe leg weakness during the first three weeks of infection. Weakness persisted with little subsequent improvement. Five to 8 months later, 4 such mice were killed, and each spinal cord was examined in Epon sections in a series of transverse sections along their lengths. All cords had 2 or more major white matter lesions which were typically greatly elongated in the rostrocaudal dimension, as seen in multiple sequential sections. While a lesion's appearance frequently suggested some degree of tract association, its size, contour and position frequently varied from level to level in a manner which is not characteristic of tract degeneration. Further, axons were preserved in these lesions, and had been remyelinated. This was accomplished by a combination of oligodendrocytes and Schwann cells. The only evidence of Wallerian degeneration in these spinal cords was a modest reduction in the cross-sectional area of a white matter column associated with the most severe lesions. These pathological findings are consistent with previous ones in this model. Rostrocaudal elongation of spinal cord lesions may be seen in other animal models of virus-induced demyelination; this and other features reported here have been described in multiple sclerosis.

Leptomeningitis and polycaryocyte formation in the CNS of rats inoculated subcutaneously with herpes simplex virus

Wistar rats were inoculated subcutaneously with either type 1 (HSV1) or type 2 (HSV2) Herpes simplex virus at 5 days of age. Animals were killed in extremis or at the end of the 14-day observation period postinoculation. Acute destructive meningoencephalitis with hemorrhage and leukocytic infiltration was observed in both groups. Polycaryocytes comprised of cells of the internal granular layer of the cerebellum were observed in some animals inoculated with HSV1. These multinucleated cells appeared to be formed by fusion of virus-infected cells, and intranuclear inclusion bodies were observed. Lesions in the leptomeninges were particularly striking in animals inoculated with HSV2. Viral replication in resident cells of the leptomeninges was demonstrated by electron microscopy.