Hongyan Yang

Adeno-associated virus (AAV) vector genomes have been limited to 5 kilobases (kb) in length because their packaging limit was thought to be similar to the size of the parent AAV genome. Recent reports claim that significantly larger vector genomes can be packaged intact. We examined the packaged vector genomes from plasmid-encoded AAV vectors that ranged from 4.7 to 8.7 kb in length, using AAV types 2, 5, and 8 capsids. Southern blot analysis indicated that packaged AAV vector genomes never exceeded 5.2 kb in length irrespective of the size of the plasmid-encoded vector or the capsid type. This result was confirmed by vector genome probing with strand-specific oligonucleotides. The packaged vector genomes derived from plasmid-encoded vectors exceeding 5 kb were heterogeneous in length and truncated on the 5′ end. Despite their truncated genomes, vector preparations produced from plasmid-encoded vectors exceeding 5.2 kb mediated reporter gene expression in vitro at high multiplicity of infection (MOI). The efficiency of expression was substantially lower than that of reporter vectors with genomes <5 kb in length. We propose that transcriptionally functional, intact vector genomes are generated in cells transduced at high MOI from the fragmentary genomes of these larger vectors, probably by recombination. Adeno-associated virus (AAV) vector genomes have been limited to 5 kilobases (kb) in length because their packaging limit was thought to be similar to the size of the parent AAV genome. Recent reports claim that significantly larger vector genomes can be packaged intact. We examined the packaged vector genomes from plasmid-encoded AAV vectors that ranged from 4.7 to 8.7 kb in length, using AAV types 2, 5, and 8 capsids. Southern blot analysis indicated that packaged AAV vector genomes never exceeded 5.2 kb in length irrespective of the size of the plasmid-encoded vector or the capsid type. This result was confirmed by vector genome probing with strand-specific oligonucleotides. The packaged vector genomes derived from plasmid-encoded vectors exceeding 5 kb were heterogeneous in length and truncated on the 5′ end. Despite their truncated genomes, vector preparations produced from plasmid-encoded vectors exceeding 5.2 kb mediated reporter gene expression in vitro at high multiplicity of infection (MOI). The efficiency of expression was substantially lower than that of reporter vectors with genomes <5 kb in length. We propose that transcriptionally functional, intact vector genomes are generated in cells transduced at high MOI from the fragmentary genomes of these larger vectors, probably by recombination.

Natural antimicrobial peptides (AMPs) are promising candidates for the development of a new generation of antimicrobials to combat antibiotic-resistant pathogens. They have found extensive applications in the fields of medicine, food, and agriculture. However, efficiently screening AMPs from natural sources poses several challenges, including low efficiency and high antibiotic resistance. This review focuses on the action mechanisms of AMPs, both through membrane and non-membrane routes. We thoroughly examine various highly efficient AMP screening methods, including whole-bacterial adsorption binding, cell membrane chromatography (CMC), phospholipid membrane chromatography binding, membrane-mediated capillary electrophoresis (CE), colorimetric assays, thin layer chromatography (TLC), fluorescence-based screening, genetic sequencing-based analysis, computational mining of AMP databases, and virtual screening methods. Additionally, we discuss potential developmental applications for enhancing the efficiency of AMP discovery. This review provides a comprehensive framework for identifying AMPs within complex natural product systems.

Although few simian rotaviruses (RVs) have been isolated, such strains have been important for basic research and vaccine development. To explore the origins of simian RVs, the complete genome sequences of strains PTRV (G8P[1]), RRV (G3P[3]), and TUCH (G3P[24]) were determined. These data allowed the genotype constellations of each virus to be determined and the phylogenetic relationships of the simian strains with each other and with nonsimian RVs to be elucidated. The results indicate that PTRV was likely transmitted from a bovine or other ruminant into pig-tailed macaques (its host of origin), since its genes have genotypes and encode outer-capsid proteins similar to those of bovine RVs. In contrast, most of the genes of rhesus-macaque strains, RRV and TUCH, have genotypes more typical of canine-feline RVs. However, the sequences of the canine and/or feline (canine/feline)-like genes of RRV and TUCH are only distantly related to those of modern canine/feline RVs, indicating that any potential transmission of a progenitor of these viruses from a canine/feline host to a simian host was not recent. The remaining genes of RRV and TUCH appear to have originated through reassortment with bovine, human, or other RV strains. Finally, comparison of PTRV, RRV, and TUCH genes with those of the vervet-monkey RV SA11-H96 (G3P[2]) indicates that SA11-H96 shares little genetic similarity to other simian strains and likely has evolved independently. Collectively, our data indicate that simian RVs are of diverse ancestry with genome constellations that originated largely by interspecies transmission and reassortment with nonhuman animal RVs.

The family Cystoviridae comprises several bacteriophages with double-stranded RNA (dsRNA) genomes. We have previously purified the catalytic polymerase subunit (Pol) of one of the Cystoviridae members, bacteriophage phi6, and shown that the protein can catalyze RNA synthesis in vitro. In this reaction, both bacteriophage-specific and heterologous RNAs can serve as templates, but those containing 3' termini from the phi6 minus strands are favored. This provides a molecular basis for the observation that only plus strands, not minus strands, are transcribed from phi6 dsRNA segments in vivo. To test whether such a regulatory mechanism is also found in other dsRNA viruses, we purified recombinant Pol subunits from the phi6-related bacteriophages phi8 and phi13 and assayed their polymerase activities in vitro. The enzymes catalyze template-dependent RNA synthesis using both single-stranded-RNA (ssRNA) and dsRNA templates. However, they differ from each other as well as from phi6 Pol in certain biochemical properties. Notably, each polymerase demonstrates a distinct preference for ssRNAs bearing short 3'-terminal sequences from the virus-specific minus strands. This suggests that, in addition to other factors, RNA transcription in Cystoviridae is controlled by the template specificity of the polymerase subunit.