RNA modifications are a common occurrence across all domains
of life. Several chemical modifications, including N6-
methyladenosine, have also been found in viral transcripts
and viral RNA genomes. Some of the modifications increase
the viral replication efficiency while also helping the virus to
evade the host immune system. Nonetheless, there are numerous
examples in which the host's RNA modification enzymes
function as antiviral factors. Although established methods
like MeRIP-seq and miCLIP can provide a transcriptome-
wide overview of how viral RNA is modified, it is difficult
to distinguish between the complex overlapping viral
transcript isoforms using the short read-based techniques.
Nanopore direct RNA sequencing (DRS) provides both long
reads and direct signal readings, which may carry information
about the modifications. Here, we describe a refined protocol
for analyzing the RNA modifications in viral transcriptomes
using nanopore technology.
Shiga toxin-producing Escherichia coli (STEC) is a foodborne
pathogen capable of causing illness in humans. In a previous
study, our group showed that a STEC isolate belonging to
O22:H8 serotype (strain 154) can interfere with STEC O157:H7
colonization both in vitro and in vivo. Using whole-genome
sequencing and genomic comparative, we predicted a subset
of genes acquired by O22:H8 strain 154 through horizontal
gene transfer that might be responsible for the phenotype
previously described by our group. Among them were identified
genes related to the pathogenesis of non-LEE (locus of
enterocyte effacement) STEC, specific metabolic processes,
antibiotic resistance and genes encoding for the T6SS-1 that
is related to inter-bacterial competition. In addition, we showed
that this strain carries stx1c and stx2dact, a mucus-inducible
variant. The results obtained in this study provide insights
into STEC genomic plasticity and the importance of genomic
islands in the adaptation and pathogenesis of this
pathogen.
Available antibiotics to treat Acinetobacter baumannii infection
is limited due to increasing resistance and the emergence
of multiple drug-resistant strains. Hence, discovering effective
agents against A. baumannii to reduce the number of infectionrelated
deaths is imperative. In search of novel and alternative
antibiotics, the antibacterial function of lipocalin2 (Lcn2) was
investigated to treat systemic infections of A. baumannii using
a mouse neutropenia model. We observed a significant increase
in serum Lcn2 levels upon bacterial injection into the
mouse, and the administration of recombinant Lcn2 (rmLcn2)
extended their survival. Such protective effects were also observed
in rmLcn2-pretreated macrophages, where rmLcn2
reduced the survival of the pathogen inside the macrophages.
The underlying molecular mechanism of Lcn2 protection was
also investigated. We observed that pretreatment of the Raw-
264.7 macrophages with rmLcn2 markedly altered the expression
of tonB3, which encodes a component of the transporter
for ferrisiderophores in A. baumannii. However, the
expression of katG, the gene encoding catalase, remained unaffected.
These indicate that Lcn2-mediated defense against
the pathogen is related to nutritional immunity rather than
reactive oxygen species (ROS) production. Furthermore, the
addition of rmLcn2 in infected mice diminished bacterial burden
in multiple organs and enhanced the expression of tonB3
in the liver, spleen, and lungs of the infected mice. Increased
survival rate due to rmLcn2 treatment declined when the infection
model was established using lcn2-defective (lcn2-/-)
mice, which indicated the necessity of endogenous Lcn2. Therefore,
the antibacterial function of Lcn2 can be exploited to
develop an alternative therapeutic agent against A. baumannii.
Acinetobacter baumannii causes multidrug resistance, leading
to fatal infections in humans. In this study, we showed that
Lys AB2 P3-His–a hexahistidine-tagged form of an antimicrobial
peptide (AMP) loaded onto DNA aptamer-functionalized
gold nanoparticles (AuNP-Apt)–can effectively inhibit
A. baumannii infection in mice. When A. baumannii-infected
mice were intraperitoneally injected with AuNP-Apt loaded
with Lys AB2 P3-His, a marked reduction in A. baumannii
colonization was observed in the mouse organs, leading to
prominently increased survival time and rate of the mice compared
to those of the control mice treated with AuNP-Apt or
Lys AB2 P3-His only. This study shows that AMPs loaded
onto AuNP-Apt could be an effective therapeutic tool against
infections caused by multidrug-resistant pathogenic bacteria
in humans.