Table 1.

Engineering Tropism of Non-Enveloped Viruses.

Methods	Approach	Applications/Examples	Ref.
Rational Design	Mutation of surface-exposed tyrosine and threonine	Improved AAV2 and AAV8 transduction in CNS.	[35,36,37]
	Ligand/peptide incorporation into the exposed sites on AAV capsids	The MTS-modified AAV2 redirected AAV particles to the mitochondria. TVSALK on AAV9 improved systemic gene delivery efficiency via BBB. DARPins markers on AAV2 improved the transduction efficiency in CD4/CD32a double-positive cells	[38,39,40]
Directed Evolution	Error-prone PCR and DNA shuffling	The evolved AAV2-retro robustly travel retrograde in neuronal projections. AAV2.N54 exhibited an improved tropism for mouse, pig, rabbit, and monkey retinas.	[41,42]
	Peptide display	Novel CNS-targeting capsids, PHP.B, AAV.BI30, andAAV.CAP.B10.	[43,44,45]
	CREATE	Novel CNS-targeting capsids, PHP.B, PHP.eB, PHP.S.	[43]
	BRAVE	Novel AAV variant with retrograde transport and infectivity of dopamine neurons in both rodent and human cells.	[46]
	TRACER	BBB-penetrating AAV variants with high efficiency in mouse brain.	[47]
	NAVIGATE	Novel AAV3B and AAV.PEPIN variants with superior retina and ocular transduction profiles in multiple animal models.	[48]
In silico- or ML-based Design	Ancestral reconstruction algorithms	Novel Anc80L65 variant with improved thermostability and delivery efficiency.	[49,50,51,52,53]
	Machine learning	Improving AAV production and immune evasion.	[49,54,55,56]
Genetic Modification	Incorporation of targeting peptide sequences	Engineer CAR-independent entry.	[57]
	Development of artificial vectors	Artificial vectors for intravascular delivery (AVIDs) for gene delivery to human hematopoietic stem and progenitor cells	[58]