Biology subjects

Porter, J. M.

Publications and source records attributed to Porter, J. M..

6 recordsLinked to original sources

bioRxiv2026

Human alpha-defensin 5 stabilizes the enterovirus A71 capsid and blocks infection

Human alpha-defensins are antimicrobial peptides abundantly expressed in neutrophils and the small intestine. They block infection of several families of non-enveloped DNA viruses by binding to and stabilizing the viral capsid during entry, thereby preventing the genome from reaching the nucleus to initiate replication. It is unclear if a similar mechanism also applies to RNA viruses. To study this further, we investigated the interaction of human alpha-defensin 5 (HD5) with enterovirus A71 (EV-A71). We found that HD5 disrupts EV-A71 infection in cell culture and blocks viral entry. HD5 binds directly to the EV-A71 capsid and disrupts key conformational changes essential to the initiation of in vitro uncoating as well as downstream viral genome release. Using a suite of HD5 point mutants, we found that these two uncoating blocks are separable, and HD5 must achieve both to fully neutralize EV-A71 infection. This work advances our understanding of alpha-defensin antiviral action and demonstrates several conserved features of HD5 inhibition that expand to a clinically important RNA virus. Author SummaryIn this study, we demonstrated that human defensin 5 (HD5) inhibits infection of pathogenic enterovirus A71 (EV-A71). HD5 binds to EV-A71 and disrupts in vitro viral uncoating by stabilizing the viral capsid and blocking genome release. Using a library of HD5 mutants, we identified a continuous surface within HD5 important for binding to EV-A71 and disrupting infection. This surface includes amino acid residues previously shown to be important for inhibition of human adenovirus 5 and human papillomavirus 16 and represents a conserved interface involved in broad-spectrum HD5 antiviral activity. We determined that capsid stabilization and blocked genome release are independent modes of HD5 action and identified individual HD5 mutants with separable functions. These mutants provide valuable tools to further study the biology of EV-A71 uncoating. Overall, this work demonstrates the first example of an enterovirus inhibited by an -defensin and advances our mechanistic understanding of HD5 antiviral action to a new pathogenic virus.

microbiology↗

bioRxiv2024

Mechanisms of AAV2 neutralization by human alpha-defensins

Antiviral immunity compromises the efficacy of adeno-associated virus (AAV) vectors used for gene therapy. This is well understood for the adaptive immune response. However, innate immune effectors like alpha-defensin antimicrobial peptides also block AAV infection, although their mechanisms of action are unknown. To address this gap in knowledge, we investigated AAV2 and AAV6 neutralization by human neutrophil peptide 1 (HNP1), a myeloid alpha-defensin, and human defensin 5 (HD5), an enteric alpha-defensin. We found that both defensins bind to AAV2 and inhibit infection at low micromolar concentrations, similar to our prior studies of AAV6. While HD5 prevents AAV2 and AAV6 from binding to cells, HNP1 does not. However, AAV2 and AAV6 exposed to HD5 after binding to cells are still neutralized, indicating an additional block to infection. Accordingly, both HD5 and HNP1 inhibit externalization of the VP1 unique domain of both AAV2 and AAV6, which contains a phospholipase A2 enzyme required for endosome escape and nuclear localization signals required for nuclear entry. Consequently, both defensins prevent AAV from reaching the nucleus. Disruption of intracellular trafficking of the viral genome to the nucleus is reminiscent of how alpha-defensins neutralize other non-enveloped viruses, suggesting a common mechanism of inhibition. These results will inform the development of vectors capable of overcoming these hurdles to improve the efficiency of gene therapy. Author SummaryAAVs are commonly used as gene therapy vectors due to their broad tropism and lack of disease association; however, host innate immune factors, such as human alpha-defensin antimicrobial peptides, can hinder gene delivery. Although it is becoming increasingly evident that human alpha-defensins can block infection by a wide range of nonenveloped viruses, including AAVs, their mechanism of action remains poorly understood. In this study, we describe for the first time how two types of abundant human alpha-defensins neutralize two AAV serotypes, AAV2 and AAV6. We found that one defensin prevents AAV binding to cells, the first step in infection, while both defensins block a critical later step in AAV entry. Our findings support the emerging idea that defensins use a common strategy to block infection by DNA viruses that replicate in the nucleus. Through understanding how innate immune effectors interact with and impede AAV infection, vectors can be developed to bypass these interventions and allow more efficient gene delivery.

microbiology↗

bioRxiv2024

Alpha-defensin binding expands human adenovirus tropism

Mammalian -defensins are a family of abundant effector peptides of the mucosal innate immune system. Although primarily considered to be antimicrobial, -defensins can increase rather than block infection by certain prominent bacterial and viral pathogens in cell culture and in vivo. We have shown previously that exposure of mouse and human adenoviruses (HAdVs) to -defensins is able to overcome competitive inhibitors that block cell binding, leading us to hypothesize a defensin-mediated binding mechanism that is independent of known viral receptors. To test this hypothesis, we used genetic approaches to demonstrate that none of several primary receptors nor integrin co-receptors are needed for human -defensin-mediated binding of HAdV to cells; however, infection remains integrin dependent. Thus, our studies have revealed a novel pathway for HAdV binding to cells that bypasses viral primary receptors. We speculate that this pathway functions in parallel with receptor-mediated entry and contributes to -defensin-enhanced infection of susceptible cells. Remarkably, we also found that in the presence of -defensins, HAdV tropism is expanded to non-susceptible cells, even when viruses are exposed to a mixture of both susceptible and non-susceptible cells. Therefore, we propose that in the presence of sufficient concentrations of -defensins, such as in the lung or gut, integrin expression rather than primary receptor expression will dictate HAdV tropism in vivo. In summary, -defensins may contribute to tissue tropism not only through the neutralization of susceptible viruses but also by allowing certain defensin-resistant viruses to bind to cells independently of previously described mechanisms. Author SummaryIn this study, we demonstrate a novel mechanism for binding of human adenoviruses (HAdVs) to cells that is dependent upon interactions with -defensin host defense peptides but is independent of known viral receptors and co-receptors. To block normal receptor-mediated HAdV infection, we made genetic changes to both host cells and HAdVs. Under these conditions, -defensins restored cell binding; however, infection still required the function of HAdV integrin co-receptors. This was true for multiple types of HAdVs that use different primary receptors and for cells that are either naturally devoid of HAdV receptors or were engineered to be receptor deficient. These observations suggest that in the presence of concentrations of -defensins that would be found naturally in the lung or intestine, there are two parallel pathways for HAdV binding to cells that converge on integrins for productive infection. Moreover, these binding pathways function independently, and both operate in mixed culture. Thus, we have found that viruses can co-opt host defense molecules to expand their tropism.

microbiology↗

bioRxiv2022

Virtual motivation: The psychological and transfer of learning effects of immersive virtual reality practice

Previous research has shown practice within an immersive virtual reality (VR) environment improves real-world (RW) performance. Increased user motivation is one possible advantage of practicing in VR. One recent study showed that an enriched gaming environment led to higher levels of engagement, resulting in a direct learning benefit. The purpose of this study was to compare the intrinsic motivation, engagement, and transfer of learning differences between VR practice and RW practice of the same motor skill. Participants (n = 61) were randomly assigned to a RW practice group (n = 30) or a VR practice group (n = 31) in which they performed a golf putting task. Analyses showed VR practice led to a significantly greater increase in average IMI score than RW practice. Analyses for performance showed there was a significant (p < .001) improvement in accuracy (i.e., radial error) from pre to posttest, but the two groups did not differ from one another. Overall, these results partially support our hypotheses and suggest that VR practice led to a greater increase in motivation compared to RW practice. Additionally, these results suggest that VR practice was similarly effective at improving accuracy compared to RW practice. Future research directions are discussed.

neuroscience↗

bioRxiv2022

Off the shelf: Investigating transfer of learning using commercially available virtual reality equipment

The evolution of virtual reality (VR) has created the opportunity for a relatively low-cost and accessible method to practice motor skills. Previous studies have demonstrated how motor skill practice in non-immersive virtual environments transfers to physical environments. Though minimal research has investigated motor learning and transfer within immersive VR, multiple experiments provide empirical evidence of positive transfer effects. To enhance the similarities between virtual and physical environments, most studies have used software engines and modified hardware. However, many learners and practitioners are currently using commercially available VR with the goal of enhancing real-world performance, though there is very little evidence to support the notion of positive transfer for these systems. Therefore, the purpose of this experiment was to investigate how motor skill practice using a commercially available VR system improved real-world performance and how that compared to physical practice. Participants (n = 68) were randomly selected into one of two groups: virtual reality (VR) practice (n = 33) or real-world (RW) practice (n = 35). The experiment took place over two consecutive days with a pretest, posttest, and practice phase occurring on both days. The pre- and post-testing phases were identical for both groups and consisted of putting a golf ball 10 times on a carpeted surface towards the center of a target. The practice phases consisted of 60 total putts per day in the respective environment (VR or RW). Participants continuously alternated golf putting holes from three different distances until they accrued 60 total putts. Participants in the RW group performed golf putts to three targets. Participants in the VR group also performed golf putts on three different miniature golf putting holes, using the commercially available Oculus Rift and the Cloudlands VR Minigolf game. The VR putting targets were designed to replicate the putting holes in the physical environment. Separate 2 (condition) x 4 (test phase) repeated measures ANOVAs were used to assess accuracy and club head kinematics. The results revealed a significant main effect for test phase, but not for condition. Post hoc analyses revealed both groups significantly improved their putting accuracy and club head kinematics at similar rates. The results from this study indicate that the transfer of learning that occurred from the commercially available VR practice was equally effective when compared to RW practice.

neuroscience↗

bioRxiv2019

The effects of combining focus of attention and autonomy support on shot accuracy in the penalty kick

The penalty kick is of great importance in the sport of soccer. Therefore, the aim of this study was to test predictions of the OPTIMAL theory and identify key attentional and motivational factors that impact the accuracy of the penalty kick. The following six groups of skilled participants performed penalty kicks following instructions that directed their focus of attention or impacted their autonomy support: external focus with autonomy support (EF/AS), external focus alone (EF), internal focus with autonomy support (IF/AS), internal focus alone (IF), autonomy support alone (AS) and control (C) groups. The analysis showed that the EF/AS group demonstrated better kicking accuracy relatively to the IF/AS, IF and C groups, but there were no significant differences between the EF/AS and EF or AS groups. Interestingly, the EF/AS group showed higher self-efficacy compared to the EF, IF/AS, IF and C groups. The finding suggest that a combination of attentional and motivational factors may produce benefits in motor performance.

scientific communication and education↗