Abstract
Purpose: :
To determine ocular tolerance of intravitreal anti-pneumolysin IgG immunoglobin (ab-PLY) and its efficacy as an adjunct to intravitreal vancomycin in experimental Streptococcus pneumoniae endophthalmitis.
Methods: :
Ab-PLY was isolated from the serum of New Zealand white (NZW) rabbits immunized with heat inactivated pneumolysin. IgG titers against PLY were determined by ELISA. The ab-PLY was run on a gel to rule out contamination. Rabbits were treated with intravitreal ab-PLY, 400 µg (n=6) and 200 µg (n=3) and sham intravitreal injections with either PBS or vancomycin (n=4). In the infection group, E353 strain of S. pneumoniae (102 CFU/10µl) was injected intravitreally into one eye of each animal. 24 hours later, the rabbits were divided into 3 groups; V gp (1mg/0.1 ml intravitreal vancomycin: n=3); V/ab-PLY gp (intravitreal vancomycin + 200 µg ab-PLY: n=3) and control (untreated: n=3). Animals had daily slit lamp examination and dilated indirect ophthalmoscopy and were euthanized on day 3 post infection (PI). Electroretinograms (ERG) were done on days 0 and 3 PI. Vitreous aspirate was diluted and plated on blood agar on day 3 PI.
Results: :
Sham injections caused no clinical reaction. Intravitreal ab-PLY caused severe fibrinous anterior chamber (AC) reaction and inferior vitreous exudates (400 µg >>200 µg).Histopathology (HPE) showed vitreous inflammatory cells without retinal damage. Controls developed panophthalmitis by day 3 PI. Treated eyes improved. AC and vitreous inflammation was more severe in the V/ab-PLY gp compared to V gp on all days. HPE showed that the V/ab-PLY gp had increased vitreous and AC inflammatory cells compared to V gp but had similar retinal damage. ERG amplitude was similar between the 2 treatment groups.
Conclusions: :
Intravitreal ab-PLY caused an ocular inflammatory reaction without structural or functional retinal damage. In experimental S. pneumoniae endophthalmitis, adjunctive intravitreal ab-PLY did not provide additional therapeutic benefits (evaluated by clinical examination, ERG, microbiology and HPE) compared to intravitreal vancomycin alone.
Keywords: endophthalmitis • bacterial disease • inflammation