Influenza vaccine effectiveness within prospective cohorts of healthcare personnel in Israel and Peru 2016-2019.

BACKGROUND: There are limited data on influenza vaccine effectiveness (IVE) in preventing laboratory-confirmed influenza illness among healthcare personnel (HCP). METHODS: HCP with direct patient contact working full-time in hospitals were followed during three influenza seasons in Israel (2016-2017 to 2018-2019) and Peru (2016 to 2018). Trivalent influenza vaccines were available at all sites, except during 2018-2019 when Israel used quadrivalent vaccines; vaccination was documented by electronic medical records, vaccine registries, and/or self-report (for vaccinations outside the hospital). Twice-weekly active surveillance identified acute respiratory symptoms or febrile illness (ARFI); self-collected respiratory specimens were tested by real-time reverse transcription polymerase chain reaction (PCR) assay. IVE was 100 × 1-hazard ratio (adjusted for sex, age, occupation, and hospital). RESULTS: Among 5,489 HCP who contributed 10,041 person-seasons, influenza vaccination coverage was 47% in Israel and 32% in Peru. Of 3,056 ARFIs in Israel and 3,538 in Peru, A or B influenza virus infections were identified in 205 (7%) in Israel and 87 (2.5%) in Peru. IVE against all viruses across seasons was 1% (95% confidence interval [CI] = -30%, 25%) in Israel and 12% (95% CI = -61%, 52%) in Peru. CONCLUSION: Estimates of IVE were null using person-time models during six study seasons in Israel and Peru.

Complete genome sequence of Streptomyces venezuelae ATCC 15439, a promising cell factory for production of secondary metabolites.

Streptomyces venezuelae ATCC 15439, which produces 12- and 14-membered ring macrolide antibiotics, is a platform strain for heterologous expression of secondary metabolites. Its 9.05-Mb genome sequence revealed an abundance of genes involved in the biosynthesis of secondary metabolites and their precursors, which should be useful for the production of bioactive compounds.

Characterization and engineering of the ethylmalonyl-CoA pathway towards the improved heterologous production of polyketides in Streptomyces venezuelae.

Streptomyces venezuelae has an inherent advantage as a heterologous host for polyketide production due to its fast rate of growth that cannot be endowed easily through metabolic engineering. However, the utility of S. venezuelae as a host has been limited thus far due to its inadequate intracellular reserves of the (2S)-ethylmalonyl-CoA building block needed to support the biosynthesis of polyketides preventing the efficient production of the desired metabolite, such as tylactone. Here, via precursor supply engineering, we demonstrated that S. venezuelae can be developed into a more efficient general heterologous host for the quick production of polyketides. We first identified and functionally characterized the ethylmalonyl-CoA pathway which plays a major role in supplying the (2S)-ethylmalonyl-CoA extender unit in S. venezuelae. Next, S. venezuelae was successfully engineered to increase the intracellular ethylmalonyl-CoA concentration by the deletion of the meaA gene encoding coenzyme B12-dependent ethylmalonyl-CoA mutase in combination with ethylmalonate supplementation and was engineered to upregulate the expression of the heterologous tylosin PKS by overexpression of the pathway specific regulatory gene pikD. Thus, a dramatic increase (∼10-fold) in tylactone production was achieved. In addition, the detailed insights into the role of the ethylmalonyl-CoA pathway, which is present in most streptomycetes, provides a general strategy to increase the ethylmalonyl-CoA supply for polyketide biosynthesis in the most prolific family of polyketide-producing bacteria.

Development of a Streptomyces venezuelae-based combinatorial biosynthetic system for the production of glycosylated derivatives of doxorubicin and its biosynthetic intermediates.

Doxorubicin, one of the most widely used anticancer drugs, is composed of a tetracyclic polyketide aglycone and l-daunosamine as a deoxysugar moiety, which acts as an important determinant of its biological activity. This is exemplified by the fewer side effects of semisynthetic epirubicin (4'-epi-doxorubicin). An efficient combinatorial biosynthetic system that can convert the exogenous aglycone ε-rhodomycinone into diverse glycosylated derivatives of doxorubicin or its biosynthetic intermediates, rhodomycin D and daunorubicin, was developed through the use of Streptomyces venezuelae mutants carrying plasmids that direct the biosynthesis of different nucleotide deoxysugars and their transfer onto aglycone, as well as the postglycosylation modifications. This system improved epirubicin production from ε-rhodomycinone by selecting a substrate flexible glycosyltransferase, AknS, which was able to transfer the unnatural sugar donors and a TDP-4-ketohexose reductase, AvrE, which efficiently supported the biosynthesis of TDP-4-epi-l-daunosamine. Furthermore, a range of doxorubicin analogs containing diverse deoxysugar moieties, seven of which are novel rhodomycin D derivatives, were generated. This provides new insights into the functions of deoxysugar biosynthetic enzymes and demonstrates the potential of the S. venezuelae-based combinatorial biosynthetic system as a simple biological tool for modifying structurally complex sugar moieties attached to anthracyclines as an alternative to chemical syntheses for improving anticancer agents.

Engineering of plant-specific phenylpropanoids biosynthesis in Streptomyces venezuelae.

Phenylpropanoids, including flavonoids and stilbenes, are plant secondary metabolites with potential pharmacological and nutraceutical properties. To expand the applicability of Streptomyces venezuelae as a heterologous host to plant polyketide production, flavonoid and stilbene biosynthetic genes were expressed in an engineered strain of S. venezuelae DHS2001 bearing a deletion of native pikromycin polyketide synthase gene. A plasmid expressing the 4-coumarate/cinnamate:coenzyme A ligase from Streptomyces coelicolor (ScCCL) and the chalcone synthase from Arabidopsis thaliana (atCHS) under the control of a single ermE* promoter was constructed and introduced into S. venezuelae DHS2001. The resulting strain produced racemic naringenin and pinocembrin from 4-coumaric acid and cinnamic acid, respectively. Placement of an additional ermE* promoter upstream of the codon-optimized atCHS (atCHS(op)) gene significantly increased the yield of both flavanones. Expression of codon-optimized chalcone isomerase gene from Medicago sativa, together with ScCCL and atCHS(op) genes led to production of (2S)-flavanones, but the yield was reduced. On the other hand, a recombinant strain harboring the ScCCL and codon-optimized stilbene synthase gene from Arachis hypogaea generated stilbenes such as resveratrol and pinosylvin. This is the first report on the heterologous expression of plant phenylpropanoid biosynthetic pathways in Streptomyces genus.