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We appreciated the paper by Iriyama et al. The authors have
investigated the role of anti vascular endothelial growth factor (VEGF)
antibodies on retinal ganglion cells in rats. It is an interesting and
relevant paper considering the clinical use of anti-VEGF antibodies in a
variety of ocular conditions. However, there are a couple of issues
that require further clarification.
The authors demonstrate, in figure 1, that bevacizumab (AvastinTM;
Genentech Inc. San Francisco, CA) is unable to bind to murine VEGF and
they provide evidence by doing Western blot on rat ocular tissue (retina
and choroid) using anti-rat VEGF antibody (R&D systems, Minneapolis) and
bevacizumab. Membranes were developed using rabbit anti mouse IgG and
anti-goat IgG. Authors demonstrate that only anti rat VEGF antibody was
able to detect rat VEGF and not bevacizumab. Although the authors have
not mentioned it in their paper, the anti-rat VEGF antibody that the
authors used is raised in goat according to the information provided by
the source. It justifies the use of anti-goat secondary antibody. It is
not clear why and where they used anti-mouse IgG. On the other hand,
bevacizumab is a humanized antibody and it should be detected by
anti-human IgG 3, which was not used by the authors. This might explain
why they could not detect bevacizumab binding with rat VEGF. Consistent
with this argument, Bock et al. in a recent paper have been able to
show that bevacizumab binds to murine VEGF. They used a similar
technique (Western blot), and by using anti-human IgG were able to
detect bevacizumab bound to the murine VEGF. They further confirmed
their results using additional techniques such as ELISA (again utilizing
anti-human IgG) and surface Plasmon resonance (BIAcore assay).
Also, the figure legend of Figure 2 does not match the figure, nor
does the legend for Figure 4. It seems figures have switched.
Rajesh K Sharma, MD, PhD
Kakarla V Chalam, MD, PhD, MBA, FACS
Department of Ophthalmology
University of Florida, College of Medicine
1. Iriyama A, Chen YN, Tamaki Y et al. Effect of anti-VEGF antibody on retinal ganglion cells in rats. Br.J.Ophthalmol. 2007;91:1230-3.
2. Aggio FB, Farah ME, Silva WC et al. Intravitreal
bevacizumab for exudative age-related macular degeneration after multiple treatments.
Graefes Arch.Clin.Exp.Ophthalmol. 2006.
3. Heiduschka P, Fietz H, Hofmeister S et al. Penetration of bevacizumab through the retina after intravitreal injection in the monkey.
Invest Ophthalmol.Vis.Sci. 2007;48:2814-23.
4. Bock F, Onderka J, Dietrich T et al. Bevacizumab as a potent inhibitor of inflammatory corneal angiogenesis and lymphangiogenesis.
Invest Ophthalmol.Vis.Sci. 2007;48:2545-52.