Biology subjects

Melo, P.

Publications and source records attributed to Melo, P..

5 recordsLinked to original sources

bioRxiv2025

The cow udder is a potential mixing vessel for influenza A viruses

The incursion of high pathogenicity avian influenza A virus (IAV) into US dairy cows is unprecedented in the era of molecular diagnosis and pathogen sequencing. This raises questions over the likelihood of further outbreaks and whether dairy cattle could be a "mixing vessel" for novel strains of IAV. Using a panel of BSL2-safe reassortant viruses representing clade 2.3.4.4b H5 epizootic lineages circulating since 2020, we found that a cow B3.13 isolate displayed enhanced replication in cow mammary gland cells, along with increased viral polymerase activity and stronger interferon antagonism in cow cells compared to an earlier EA-2020-C genotype virus. However, multiple avian and mammalian IAV strains, including other clade 2.3.4.4b high pathogenicity genotypes, were replication competent in bovine cells, particularly those of the mammary gland, suggesting that there is a diverse circulating IAV pool with the potential to infect cows. Moreover, we show that cow mammary cells co-express -2,3 and -2,6 - linked sialic acids, and are susceptible to co-infection with human and avian IAVs. We conclude that the US cow influenza outbreak does not simply reflect a unique adaptation of the B3.13 genotype virus; rather, the bovine udder represents a permissive niche for IAV and a plausible site for reassortment, underscoring its potential role in generating novel influenza viruses with pandemic risk.

microbiology↗

bioRxiv2024

Bacterial metabolic remodelling by convergent evolution in response to host niche-dependent nutrient availability

New pathogens often arise after host jump events between species. However, our understanding of how bacterial pathogens pivot to distinct nutrient availabilities in a new host niche is limited. Staphylococcus aureus is a multi-host pathogen responsible for a global burden of disease in humans and farmed animals. Multiple human-to-bovine host switching events led to the emergence of S. aureus as a leading cause of intramammary infection in dairy cattle. Here, we employed ex vivo milk infections to investigate how bovine S. aureus has adapted to the dairy niche revealing metabolic remodelling including upregulation of genes for lactose utilisation and branched-chain amino acid biosynthesis in response to nutrient availability. Notably, infection of milk by bovine S. aureus results in a milk clotting phenotype associated with enhanced bacterial growth that is dependent on the protease aureolysin. The same adaptive phenotype has evolved convergently in different bovine S. aureus lineages via mutations in distinct regulatory gene loci that promote enhanced aureolysin expression. Taken together, we have dissected a key adaptive trait for a bacterial pathogen after a host-switch event, involving metabolic remodelling in response to the availability of nutrients. These findings highlight the remarkable evolutionary plasticity of S. aureus underpinning its multi-host species tropism.

microbiology↗

bioRxiv2024

Influence of asymmetric microchannels in the structure and function of engineered neuronal circuits

Understanding the intricate structure-function relationships of neuronal circuits is crucial for unraveling how the brain sustains efficient information transfer. In specific brain regions, like the hippocampus, neurons are organized in layers and form unidirectional connectivity, which is thought to help ensure controlled signal flow and information processing. In recent years, researchers have tried emulating these structural principles by providing cultured neurons with asymmetric environmental cues, namely microfluidics microchannels that promote directed axonal growth. Even though a few reports have claimed achieving unidirectional connectivity of in vitro neuronal circuits, given the lack of functional characterization, whether this structural connectivity correlates with functional connectivity remains unknown. We have replicated and tested the performance of asymmetric microchannel designs previously reported in the literature to be successful in the promotion of directed axonal growth, as well as other custom variations. A new variation of "Arrowhead", termed "Rams", was the best-performing motif with a [~]76% probability per microchannel of allowing strictly unidirectional connections at 14 days in vitro. Importantly, we assessed the functional implications of these different asymmetric microchannel designs. For this purpose, we combined custom microfluidics with microelectrode array (MEA) technology to record the electrophysiological activity of two segregated populations of hippocampal neurons ("Source" and "Target"). This functional characterization revealed that up to [~]94% of the spiking activity recorded along microchannels with the "Rams" motif propagates towards the "Target" population. Moreover, our results indicate that these engineered circuits also tended to exhibit network-level synchronizations with defined directionality. Overall, this characterization of the structure-function relationships promoted by asymmetric microchannels has the potential to provide insights into how neuronal circuits use specific network architectures for effective computations. Moreover, the here-developed devices and approaches may be used in a wide range of applications, such as disease modeling or preclinical drug screening.

neuroscience↗

bioRxiv2023

JAGGER localization and function is dependent on GPI anchor addition

In flowering plants, successful double fertilization requires the correct delivery of two sperm cells to the female gametophyte inside the ovule. The delivery of a single pair of sperm cells is achieved by the entrance of a single pollen tube into one female gametophyte. To prevent polyspermy, Arabidopsis ovules avoid the attraction of multiples pollen tubes to one ovule - polytubey block. In Arabidopsis jagger mutants, a significant number of ovules attract more than one pollen tube to an ovule due to an impairment in synergid degeneration. JAGGER encodes a putative arabinogalactan protein (AGP) which is predicted to be anchored to the plasma membrane by a glycosylphosphatidylinositol (GPI) anchor. Here, we show that JAGGER fused to citrine yellow fluorescent protein (JAGGER-cYFP) is functional and localizes mostly to the periphery of ovule integuments and transmitting tract cells. We further investigated the importance of GPI-anchor addition domains for JAGGER localization and function. Different JAGGER proteins with deletions in predicted {omega}-site regions and GAS (GPI attachment signal) domain, expected to compromise the addition of the GPI anchor, led to disruption of JAGGER localization in the cell periphery. All JAGGER proteins with disrupted localization were also not able to rescue the polytubey phenotype, pointing to the importance of GPI-anchor addition to in vivo function of the JAGGER protein.

plant biology↗

bioRxiv2020

Macrophage-derived miR-21 drives overwhelming glycolytic and inflammatory response during sepsis via repression of the PGE2/IL-10 axis.

Myeloid cells play a critical role in the development of systemic inflammation and organ damage during sepsis. The mechanisms the development of aberrant inflammatory response remains to be elucidated. MicroRNAs are small non-coding RNAs that could prevent the expression of inflammatory molecules. Although the microRNA-21 (miR-21) is abundantly expressed in macrophages, the role of miR-21 in sepsis is controversial. Here we showed that miR-21 is upregulated in neutrophils and macrophages from septic mice. We found that myeloid-specific miR-21 deletion enhances animal survival, followed by decreased bacterial growth and organ damage during sepsis. Increased resistance against sepsis was associated with a reduction of aerobic glycolysis (as determined by reduced extracellular acidification rate (ECAR) and expression of glycolytic enzymes) and systemic inflammatory response (IL-1{beta}TNF and IL-6). While miR-21-/- macrophages failed to induce aerobic glycolysis and production of pro-inflammatory cytokines, we observed increased levels of the anti-inflammatory mediators prostaglandin E2 (PGE2) and IL10. Using blocking antibodies and pharmacological tools, we further discovered that increased survival and decreased systemic inflammation in miR21{Delta}myel during sepsis is dependent on the PGE2/IL10-mediated glycolysis inhibition. Together, we are showing a heretofore unknown role of macrophage miR21 in the orchestrating the balance between anti-inflammatory mediators and metabolic reprogramming that drives cytokine storm and tissue damage during sepsis.

immunology↗