Biology subjects

Cunha, M.

Publications and source records attributed to Cunha, M..

4 recordsLinked to original sources

bioRxiv2026

Cryoelectron tomography of HIV-1 cell-cell transmission conjugates reveals a secluded environment for viral assembly and transfer

Cell-cell transmission of HIV-1 (CCT) is a highly efficient mode of intrahost transmission that provides viral particles broad protection from antiretroviral agents including antiretroviral drugs, host restriction factors, and broadly neutralizing antibodies. Interestingly, the exact factors that grant viral particles increased protection and efficiency during intrahost spread remain unclear. Using a T cell co-culturing system and correlative cryoelectron tomography (cryoET) workflow, we investigated the architecture of HIV-1 CCT sites in a near-native, in situ context to address why CCT is efficient and grants this resistance. Contrary to previous models which suggest large, virus-packed sites, our 3D reconstructions reveal that CCT occurs within small intercellular spaces containing on average 1-5 viral particles. Surrounding these spaces are long, tight membrane interfaces that seclude the viral particles from the remaining extracellular environment. These observations suggest a model where spatial isolation may limit accessibility of antiretroviral agents to the virus-containing spaces thereby conferring protection to viral particles during transmission. To functionally validate these structural insights, we developed a quantitative flow cytometry strategy that decouples CCT conjugate formation from successful CCT infection through the analysis of multicell events. This methodology allows us to systematically compare the impact different molecules such as Env and CD4 have on HIV-1 CCT in a quantitative and population-level manner. Using this approach, we determined that initial HIV-1 CCT conjugate formation is partially dependent on CD4, but the Env involved in conjugate formation may differ from Env used for viral entry. Overall, these findings may prompt a rethinking of intervention strategies for HIV-1 CCT and have further implications with cytoplasmic trafficking, nuclear import, and host restriction factors.

microbiology↗

bioRxiv2026

Unexpected changes in reproductive barriers between incipient species after experimental evolution in sympatry

Hybridization is generally considered a temporary phenomenon, but it is actually widespread and may last for large time periods between species that stably coexist. Here, to test whether evolving with a closely-related species modifies or maintains partial reproductive isolation, we performed experimental evolution in artificial sympatry vs. allopatry with two closely-related colour forms of spider mites (Tetranychus urticae) that exhibit an asymmetrical pattern of pre-mating isolation despite almost complete post-zygotic isolation. We assessed whether evolutionary changes occurred in traits associated to (i) pre-mating isolation, (ii) post-mating pre-zygotic and early post-zygotic isolation, and (iii) late post-zygotic isolation. Our results revealed that reinforcement did not occur even under forced long-term sympatric evolution. Instead, the strength of some reproductive barriers decreased (e.g., premating isolation and fertilization failure), and some trait changes indicated convergence rather than divergence between species (e.g., mating propensity, latency to copulation). In fact, both types of males showed the same decreased preference for red-form females across generations in sympatry. In line with this, traits underlying fertilization success evolved in the same direction and with similar amplitude in heterotypic crosses and in their homotypic control, as the offspring sex ratio of green-form females decreased in sympatry irrespective of the male they mated with. Finally, other changes in reproductive barriers resulted from trait correlations (e.g., decreased zygote mortality but increased juvenile mortality). Hence, despite very high costs of hybridization, responses occurring following evolution in sympatry were unrelated to selection directly associated to hybridization, but rather the by-product of other evolutionary forces, with cascading consequences for reproductive barriers. In particular, these results support the underappreciated hypothesis that within-species sexual interactions can constrain population diver-gence, or even drive trait convergence between species, thereby playing a role in the maintenance of partial reproductive isolation.

evolutionary biology↗

bioRxiv2019

Mitochondrial ascorbate synthesis acts as a pro-oxidant pathway and down-regulate energy supply in plants

Attempts to improve the ascorbate (AsA) content of plants are still dealing with the limited understanding of why exists a wide variability of this powerful anti-oxidant molecule in different plant sources, species and environmental situations. In plant mitochondria, the last step of AsA synthesis is catalyzed by the enzyme L-galactone-1,4-lactone dehydrogenase (L-GalLDH). By using GalLDH-RNAi silencing plant lines, biochemical and proteomic approaches, we here discovered that, in addition to accumulate this antioxidant, mitochondria synthesize AsA to down-regulate the respiratory activity and the cellular energy provision. The work reveals that the AsA synthesis pathway within mitochondria is a branched electron transfer process that channels electrons towards the alternative oxidase, interfering with conventional electron transport. It was unexpectedly found that significant hydrogen peroxide is generated during AsA synthesis, which affects the AsA level. The induced AsA synthesis shows proteomic alterations of mitochondrial and extra-mitochondrial proteins related to oxidative and energetic metabolism. The most identified proteins were known components of plant responses to high light acclimation, programmed cell death, oxidative stress, senescence, cell expansion, iron and phosphorus starvation, different abiotic stress/pathogen attack responses and others. We propose that changing the electron flux associated with AsA synthesis might be part of a new mechanism by which the L-GalLDH enzyme would adapt plant mitochondria to fluctuating energy demands and redox status occurring under different physiological contexts.

plant biology↗

bioRxiv2019

Rainfall and other meteorological factors as drivers of urban transmission of leptospirosis

BackgroundLeptospirosis is an important public health problem affecting vulnerable urban slum populations in developing country settings. However, the complex interaction of meteorological factors driving the temporal trends of leptospirosis remain incompletely understood.\n\nMethods and findingsFrom 1996 to 2010, we investigated the association between the weekly incidence of leptospirosis and climatic variables in the city of Salvador, Brazil by using a dynamic generalized linear model that accounted for time lags, overall trend and seasonal variation. Our model showed an increase of leptospirosis cases associated with rainfall, lower temperature and higher humidity. There was a lag of one-to-two weeks between weekly values for significant meteorological variables and leptospirosis incidence. Independent of the season, a weekly cumulative rainfall of 20 mm increased the risk of the leptospirosis by 10% compared to a week without rain. Finally, over the 14 year study period the incidence of leptospirosis decreased significantly by four fold (12.8 versus 3.6 per 100,000 people), independently of variations in climate.\n\nConclusionsStrategies to control leptospirosis should focus on avoiding contact with contaminated sources of Leptospira as well as on increasing awareness in the population and health professionals within the short time window after both low-level and extreme rainfall events. Increased leptospirosis incidence was restricted to one-to-two weeks after those events suggesting that infectious Leptospira survival may be limited to short time intervals.\n\nAuthor SummaryTo determine the role of meteorological variables, seasonal variation and temporal trends in the incidence of leptospirosis, we investigated the time series of leptospirosis incidence amongst residents of Salvador, Brazil, from 1996 to 2010. Exploratory and confirmatory statistical methods detected associations between meteorological factors and disease incidence. Results showed the importance of extreme meteorological conditions, particularly rainfall, as short-term predictors of leptospirosis incidence. In addition, we found a long-term decreasing trend of in disease incidence over the observation period.

epidemiology↗