Mini-Review: Cell Type-Specific Optogenetic Vision Restoration Approaches.

The expression of light-sensitive microbial opsins is a promising mutation-independent approach to restore vision in retinal degenerative diseases. Using viral vectors, optogenetic tools can be genetically expressed in various subpopulations of retinal neurons. The choice of cell type depends on the availability of surviving retinal cells. If cones are still alive but they lack outer segments, they can be targeted with optogenetic inhibitors, such as halorhodopsin. Alternatively, it is possible to bypass the photoreceptors and to target bipolar cells. In late-stage degeneration, when bipolar cells degenerate, "artificial photoreceptors" can be made from retinal ganglion cells, but with this approach, upstream retinal processing cannot be utilized. However, when ganglion cells are stimulated directly, higher brain regions might be able to compensate for some loss of retinal processing, which is indicated by clinical studies with epiretinal implants, where patients can perform simple visual tasks. Finally, optogenetics in combination with neuroprotective approaches could serve as a valuable strategy to restore the function of remaining cells, as well as to rescue retinal neurons from progressive degeneration.

Local and systemic responses following intravitreous injection of AAV2-encoded modified Volvox channelrhodopsin-1 in a genetically blind rat model.

We previously designed a modified channelrhodopsin-1 (mVChR1) protein chimera with a broader action than that of Chlamydomonas channelrhodopsin-2 and reported that its transduction into retinal ganglion cells can restore visual function in genetically blind, dystrophic Royal College of Surgeons (RCS) rats, with photostimuli ranging from 486 to 640 nm. In the current study, we sought to investigate the safety and influence of mVChR1 transgene expression. Adeno-associated virus type 2 encoding mVChR1 was administered by intravitreous injection into dystrophic RCS rats. Reverse-transcription PCR was used to monitor virus and transgene dissemination and the results demonstrated that their expression was restricted specifically within the eye tissues, and not in non-target organs. Moreover, examination of the blood, plasma and serum revealed that no excess immunoreactivity was present, as determined using standard clinical hematological parameters. Serum antibodies targeting the recombinant adeno-associated virus (rAAV) capsid increased after the injection; however, no increase in mVChR1 antibody was detected during the observation period. In addition, retinal histological examination showed no signs of inflammation in rAAV-injected rats. In conclusion, our results demonstrate that mVChR1 can be exogenously expressed without harmful immunological reactions in vivo. These findings will aid in studies of AAV gene transfer to restore vision in late-stage retinitis pigmentosa.

Immunomodulation by microbial ribosomes

Over the past twenty years, many authors have reported evidence of the immunoprotective capacity of ribosomes isolated from bacteria, fungi and parasites. Since 1971 we have explored the protective capacity of ribosomes isolated from a large variety of microorganisms responsible for human and animal diseases. More recently, using monoclonal antibodies raised against ribosomes and then selected for their ability to confer passive immunity to mice, we have studied the mechanism of the protection induced by ribosomes. These studies, in parallel with the development of a technology for the large scale production of ribosomes, have allowed us to achieve a new regard for ribosomal vaccines for use in human. The general concept of ribosomal vaccines in presented and examples of two such vaccines are described with data on the specific protection that they induce in mice against experimental infections with Klebsiella peneumoniae, Streptococcus pneumoniae, S. pyogenes and Haemophilus influenzae for the first one, and against Candida albicans type A and type B for the second one. Because of their high immunogenicity and their innocuity these vaccines represent a decisive improvement over classical microbial vaccines.