Table-1.

Characteristics, advantages and limitations of vectors used in corneal gene therapy

	Adenovirus	Retrovirus	Lentivirus	AAV	Non-viral	Nanoparticles
Family	Adenoviridae	Retrovirdae	Retrovirdae	Parvoviridae	---	---
Virion size	70-90 nm	80-130 nm	80-130 nm	18-26 nm	---	---
Genome size	38-39 kb	3-9 kb	3-9 kb	4.7 kb	---	---
Genome type	dsDNA	ssRNA	ssRNA	ssDNA	RNA or DNA	RNA or DNA
Virion size	70-90 nm	80-130 nm	80-130 nm	18-26 nm	---	---
Host genome integration	No	Yes	No, Yes (if impaired)	No	No	No
Efficiency	Low-high	Moderate-High	High	Moderate-High	Poor	Poor-moderate
Transgene expression	Transient (days-weeks)	Long-term (months-years)	Long-term (months-years)	Potentially long-term (months-years)	Transient (hours-days)	Variable (hours-months)
Immunogenicity	High	Moderate-high	Moderate-high	Low-moderate	Low	Low-high
Infection/tropism	Dividing cells	Dividing cells	Dividing and Non-dividing	Dividing and Non-dividing	Dividing and Non-dividing	Dividing and Non-dividing
Packaging capacity	≤ 7.5 kb	≤ 8 kb	≤ 8 kb	≤ 1.8 kb	No limit	No limit
Advantages	High titer, infect nearly all cell types, non-mutagenic	Highly efficient, sustained long gene expression	Highly efficient for all cell types sustained gene expression	Highly efficient for all cell types, stable transduction, site-specific integration	Safe, low immunogenicity, deliver any size gene	Safe, variable immunogenicity deliver any size gene
Limitations	Immunogenic, common human virus that reduce potency	Requires dividing cells, low titer, oncogenic, random integration	Immunogenic, HIV origin, random integration potential	Small insert size, low immunogenicity, HSV or adenovirus contamination potential	Poor efficiency, low-high immune reaction, short-term transgene expression	Poor efficiency, low-high immune reaction, short-term transgene expression