Mapping of genes involved in murine herpes simplex virus keratitis: identification of genes and their modifiers

Abstract

Herpes simplex keratitis (HSK) is an inflammatory response to viral infection and self antigens in the cornea and is a major cause of blindness. Using two strains of mice which are susceptible (129/SVEV) and resistant (C57BL/6) to herpes simplex virus (HSV) strain KOS, (129/SVEV x C57BL/6)F(2) mice were generated and examined for their disease susceptibility in terms of clinical symptoms, ocular disease, and antibody production following corneal scarification with HSV (KOS). A genome-wide screen was carried out using microsatellite markers to determine the genetic loci involved in this response. Loci on chromosomes 4, 5, 12, 13, and 14 were shown to be involved in general susceptibility to clinical disease, whereas loci on chromosomes 10 and 17 were shown to be unique to ocular disease.

FIG. 1.

Kinetics of disease susceptibility. Ten mice each of the parental strains, 129/SVEV (129) and C57BL/6 (B6), and (129/SVEV × C57BL/6)F₁ and F₂ mice were infected with 10⁶ PFU of HSV/mouse and followed for clinical symptoms of disease for the next 15 days.

FIG. 2.

Severity and incidence of disease. Ten mice were examined on day 6 after HSV infection. The number of mice with an incidence at each clinical disease score is shown. The clinical scores are as follows: 0, normal; 1, light sensitivity; 2, mild blepharitis; 3, severe blepharitis; and 4, ruffled fur and shaking.

FIG. 3.

Disease incidence and severity in mapped F₂ population. One hundred and thirty-two F₂ mice were infected with HSV and examined on day 6 after infection for clinical symptoms as described in the legend to Fig. 2. The data presented are the number of mice at each level of clinical disease achieved. The three populations presented in this graph are the total population, the female group in the total population, and the male group in the total population.

FIG. 4.

Intervals for HSK loci. Interval maps for the trait of HSK clinical disease show significant linkages on chromosome 12 (both sexes) (B), chromosome 5 (significant in females only) (A), and chromosome 14 (females only) (C). T, total; F, female; M, male. The QTL shown are calculated with free regression statistics except for chromosome 12 in females, where the dominant inheritance pattern (F Dom) is also depicted. In all three of the intervals shown, a down slope on both sides of the peaks could not be shown; thus, end effects need to be considered.

FIG. 5.

Histological analysis of the eye after HSV (KOS) infection. Normal uninfected tissue from C57BL/6 mice (A and B) and tissue from infected (129/SVEV × C57BL/6)F₂ mice (C and D) were fixed in buffered 10% formalin, embedded in paraffin, and stained with hematoxylin and eosin. Infected mice showed corneal (C) infiltrates and swelling, neovascularization (arrows), and cellular infiltrates in the ciliary body (CB), iris, and anterior (AC) and posterior (PC) chambers. Magnification, ×40 (A, C, and D) or ×20 (B).

FIG. 6.

Intervals for ocular histopathology. Interval maps for the trait of total ocular histopathology show significant linkages on chromosome 10 (the total population) (A), chromosome 12 (both sexes) (B), and chromosome 17 (males only) (C). The QTL shown are calculated with free regression statistics. T, total; F, female; M, male.