Doctoral Dissertations

John S. Babu

Date of Award

8-1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Comparative and Experimental Medicine

Major Professor

Barry T. Rouse

Committee Members

John E. Wilkinson, L. N. D. Potgieter, Al Ichiki

Abstract

Herpetic stromal keratitis (HSK) is an inflammatory reaction of the corneal stroma and considered to represent an immunopathologic response to herpes simplex virus (HSV) infection. In marine models, CD4+ T cells act as an essential participants in manifestation of HSK. The contribution of Th1 (type 1) and Th2 (type 2) cytokines in the disease process was studied in immunocompetent and T cell reconstituted SCDD mouse models. When in vivo expression of cytokine mRNAs was analyzed and quantified by polymerase chain reaction in the immunocompetent animals, type 1 cytokine mRNAs, particularly IFN-γ, was expressed in the cornea prior to and during the peak clinical lesions. In draining lymph node (DLN) cells of the same animals, except IL-10, both type 1 and type 2 cytokines were expressed throughout the course of the disease. Similarly, in naive or HSV immune CD4+ T cell reconstituted SCID mice, spontaneous expression of high levels of IFN-y mRNA was evident in the inflammatory cornea and the donor cell cytokine profile did not reflect the cytokine pattern in the diseased cornea. In vitro stimulation of reconstituted SCID mice corneal inflammatory cells with HSV resulted in selective secretion of IFN-γ in the culture supernatant, although multiple non secreted cytokine mRNAs could be induced after stimulation. In addition, the inflammatory corneal T cells isolated from the CD4+ T cell reconstituted SCID mice were partially anergic to HSV specific in vitro proliferative response. However, IL-4 producing Th2 cells proliferating in response to HSV specific stimulation were demonstrable in the reconstituted SCID mice splenic cells. On the other hand, when some immunocompetent animals with mild disease begin to recover, high levels of type 2 cytokine mRNAs, particularly IL-10, were coexpressed along with IFN-γ in the inflammatory cornea and in the DLN. In addition, cytokine induction was higher at the local site as evident from in vitro cytokine secretion from few inflammatory corneal cells, as well as temporal comparison of cytokine mRNA transcription frequency between the corneal and the DLN cells. In HSV infected SCID and nude mouse models, adoptive transfer of I-Ed reactive CD4+ T cells resulted in HSK lesions. The autoreactive T cells were also present in HSV infected immunocompetent and reconstituted SCID mouse models. However, productive progeny viral infection in the cornea is necessary in the pathogenesis of HSK. Corneal infection with UV inactivated or replication defective HSV mutants did not induce the disease, even in the presence of adequate frequency of HSV reactive CD4+ T cells. Taken collectively, the results indicate that following productive viral infection, multiple cytokine producing CD4+ T cells enter the cornea but selective activation of Th1 cells occur within the corneal milieu and are involved in inducing HSK. The selective activation or recruitment of IL-10 producers in some immunocompetent animals with disease remission suggests that IL-10 may be involved in the disease resolution. The autoreactive T cell responses seen in HSV infected animals, and reconstitution of disease with autoreactive T cells indicate possible involvement of self determinant in activation of CD4+ T cells during the chronic inflammatory process of HSK.

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