Spinal cord injury causes sustained disruption of the blood-testis barrier in the rat.

There is a high incidence of infertility in males following traumatic spinal cord injury (SCI). Quality of semen is frequently poor in these patients, but the pathophysiological mechanism(s) causing this are not known. Blood-testis barrier (BTB) integrity following SCI has not previously been examined. The objective of this study was to characterize the effects of spinal contusion injury on the BTB in the rat. 63 adult, male Sprague Dawley rats received SCI (n = 28), laminectomy only (n = 7) or served as uninjured, age-matched controls (n = 28). Using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), BTB permeability to the vascular contrast agent gadopentate dimeglumine (Gd) was assessed at either 72 hours-, or 10 months post-SCI. DCE-MRI data revealed that BTB permeability to Gd was greater than controls at both 72 h and 10 mo post-SCI. Histological evaluation of testis tissue showed increased BTB permeability to immunoglobulin G at both 72 hours- and 10 months post-SCI, compared to age-matched sham-operated and uninjured controls. Tight junctional integrity within the seminiferous epithelium was assessed; at 72 hours post-SCI, decreased expression of the tight junction protein occludin was observed. Presence of inflammation in the testes was also examined. High expression of the proinflammatory cytokine interleukin-1 beta was detected in testis tissue. CD68(+) immune cell infiltrate and mast cells were also detected within the seminiferous epithelium of both acute and chronic SCI groups but not in controls. In addition, extensive germ cell apoptosis was observed at 72 h post-SCI. Based on these results, we conclude that SCI is followed by compromised BTB integrity by as early as 72 hours post-injury in rats and is accompanied by a substantial immune response within the testis. Furthermore, our results indicate that the BTB remains compromised and testis immune cell infiltration persists for months after the initial injury.

The immune response to the VlsE antigenic variation protein of Borrelia burgdorferi

The spirochete Borrelia burgdorferi (Bb) is the causative agent of Lyme disease. During infection, a strong immune response is elicited towards Bb by its host; however, the organism is able to persist and to disseminate to many different tissues. The vls locus is located on the linear plasmid lp28-1, a plasmid shown to be important for virulence in the mouse model. During infection, vlsE undergoes antigenic variation through a series of gene conversions, which results in the insertion of sequences from the silent, unexpressed cassettes into the vlsE cassette. We hypothesize that this antigenic variation is important in the spirochete's ability to persist within mammals by allowing it to evade the immune system. To define the role of vls in immune evasion, the immune response against VlsE was determined by using a recombinant form of VlsE (VlsE1-His) as an antigen to screen patient sera. Lyme patients produce antibodies that recognize VlsE, and these antibodies are present throughout the course of disease. Immunization with the VlsE1-His protein provided protection against infection with Bb expressing the same variant of VlsE (VlsE1), but was only partially protective when mice were infected with organisms expressing VlsE variants; however, subsequent VlsE immunization studies yielded inconsistent protection. Successful immunizations produced different antibody reactivities to VlsE epitopes than non-protective immunizations, but the reason for this variable response is unclear. In the process of developing genetic approaches to transform infectious Bb, it was determined that the transformation barrier posed by plasmids lp25 and lp56 could be circumvented by replacing the required lp25 gene pncA. To characterize the role of vlsE in infectivity, Bb lacking lp28-1 were complemented with a shuttle plasmid containing the lp25 encoded virulence determinant pncA and vlsE. Complemented spirochetes express VlsE, but the gene does not undergo antigenic variation and infectivity in the mouse model was not restored, indicating that either antigenic variation of vlsE is necessary for survival in the mouse model or that other genes on lp28-1 are important for virulence. ^