Dear Editor,

We appreciated the paper by Iriyama et al.[1] 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.[2] 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[4] 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
Jacksonville FL

References

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.