Laureates of the Dominique Dormont 2024 thesis prizes: Diana Brychka and Alexandre Legrand

They answered our questions:

What is your academic background? Why did you turn to research?

Diana Brychka: My passion for biology and desire to contribute to advancing human health research led me to pursue a Master’s in Virology in Kyiv, Ukraine, where I gained a deep understanding of viral diseases. Alongside my studies, I worked at an R&D company to strengthen my technical skills. After graduation, I conducted research on an autoinflammatory disease in the Czech Republic, but I soon realized my true passion remained in infectious diseases. This realization motivated me to seek a PhD in HIV-1/AIDS research.

In 2020, I joined Dr. Raphael Gaudin’s team at IRIM (CNRS) in Montpellier, initially as an engineer, where I began my research on HIV-1. My commitment to the project and my ambition to pursue a PhD helped me secure both project and PhD funding from Sidaction. Over the past three years, I’ve investigated the mechanisms behind HIV-1 reservoir establishment in the brain, a project that reflects my belief that fundamental science should ultimately improve lives.

Alexandre Legrand: I first did a diploma in Bio-analysis and Control, then went on to do a degree in Life Sciences at the Université Jean Monnet in Saint-Etienne and a Masters in Fundamental Infectiology at the Université Claude Bernard Lyon 1. I did my Masters 2 placement and then my PhD under the supervision of Lucie Etienne at the Centre International de Recherche en Infectiologie in Lyon. I’ve always been interested in biology, particularly immunity and infectious agents. This led me to want to better understand the reasons for their pathogenicity and to dissect the host’s defence mechanisms, in a context of global public health that is still fragile in the face of epidemics.

What is the subject of your thesis?

Diana Brychka: HIV-1 forms a hidden reservoir in the central nervous system (CNS), contributing to HIV-associated neurocognitive disorders (HAND) and posing a major challenge to achieving a cure. My PhD thesis focused on understanding how HIV-1 infiltrates the CNS by hijacking monocytes, immune cells that can cross the blood-brain barrier (BBB), and uncovering potential strategies to prevent this process.

I discovered that monocytes non-canonically express Occludin, a tight junction-associated protein typically found in endothelial and epithelial cells. My research demonstrated that monocytic Occludin plays a pivotal role in monocyte transmigration across the brain endothelium. Furthermore, I showed that monocytes exposed to HIV-1 not only exhibit increased transmigration but they also more efficiently transport HIV-1 across the BBB compared to cell-free HIV-1 infiltration. Once in the neuroenvironment, HIV-1-exposed monocytes can differentiate into microglia-like cells and become productively infected, potentially contributing to the establishment of the HIV-1 reservoir in the CNS.

To counter this, I developed Occludin-derived peptides that significantly reduced monocyte infiltration and HIV-1 penetration in vitro and in vivo. These findings offer a novel strategy to target host cell mechanisms, potentially reducing HIV-1 reservoir in the CNS and alleviating HAND, with implications for other viruses exploiting similar pathways.

Alexandre Legrand: My thesis work focuses on the discovery and characterisation of new genes involved in human immunity to HIV. The aim is to gain a better understanding of our natural antiviral defences, in particular those capable of targeting HIV. This project focuses on two new candidates, SAMD9 and SAMD9L, two related genes that code for two complex proteins previously known to be involved in autoimmune diseases or immunity to poxviruses. The aim is to determine their involvement in viral replication by identifying, among other things, the stage of the viral cycle targeted and the mechanism employed, and also to study the evolution of these genes in order to assess their importance in the immunity of living organisms.

What do you consider to be the most significant result of your thesis work?

Diana Brychka: The most significant and unexpected result of my research was the drastic decrease in monocyte-associated HIV-1 infiltration across the brain endothelium into the brain when monocytes were treated with a peptide derived from extracellular loop 1 (EL1) of Occludin. While peptides from both extracellular loops (EL1 and EL2) reduced monocyte-associated HIV-1 infiltration, only the EL2 peptide decreased monocyte infiltration under non-infected conditions. For the first time, my work demonstrated that targeting a specific monocytic TJAP can selectively reduce HIV-1-infected monocyte infiltration into the brain.

My work not only presents a novel strategy to prevent immune cell infiltration into anatomical reservoirs of HIV-1 but also opens the possibility of targeting cell surface molecules on immune cells exploited by the virus, triggering a response specifically in HIV-1-exposed cells.

Alexandre Legrand: We have identified and characterised SAMD9L as constituting a new antiviral protein against HIV, impacting its translation via an enzymatic site that is also found in other known human antiviral proteins; the Schlafen. In addition, we have identified proteins analogous to SAMD9 or SAMD9L in bacteria, active via the same enzymatic site, which also appear to be involved in antiviral immunity in these hosts, and resulting from an evolutionary convergence.

What would you suggest for continuing your work? What do you see as the main challenges in this area?

Diana Brychka: If I were to continue my work on a smaller scale, I would focus on unraveling the molecular mechanisms behind EL1’s selective effect on HIV-1-exposed monocytes. Understanding these pathways could pave the way for translational research aimed at targeting monocytic TJAPs to specifically prevent the infiltration of HIV-1-carrying monocytes into the brain. On a larger scale, I would love to see the identification of surface molecules on immune cells carrying HIV-1, bringing targeted therapies against HIV-1 closer to reality.

Moreover, I believe it’s crucial not only to target the virus itself but also to address the damage it causes. This could offer new avenues for alleviating symptoms and improving patients’ quality of life. Additionally, such insights might help protect patients from the negative effects of viral reactivation, particularly if latency reversal strategies are used to eliminate HIV-1 from its reservoirs. These combined efforts could significantly enhance treatment outcomes and offer a more comprehensive approach to managing the disease.

The major challenges in the field include developing more physiologically relevant models to accurately mimic the HIV-1 reservoirs. Bridging research across disciplines is also crucial and it requires greater collaboration to fully understand viral persistence and immune cell hijacking by HIV-1. Additionally, the vast amount of available data, while valuable, needs systematic review to extract meaningful insights and avoid redundancy. Overcoming these difficulties is key to advancing targeted therapies and improving patient outcomes.

Alexandre Legrand: The question now is to determine why HIV is sensitive to SAMD9L, but not to SAMD9, which appears to have the opposite effect. In addition, our results suggest an effect of these proteins beyond the HIV translation step, which remains to be demonstrated. The mechanism by which SAMD9L is activated in the cell also remains to be elucidated, and could involve recognition of the virus’ RNA or certain of its proteins via the C-terminal part of SAMD9L. Finally, further study of the bacterial analogues identified could reveal similar mechanisms in the defence of bacteria against their own viruses, giving us a broader insight into immunity beyond humans, and how this has been shaped over the course of evolution.

What are your career plans after your thesis?

Diana Brychka: After my thesis, I continue working with my PhD supervisor Raphael Gaudin to identify dysregulated pathways in the brain during long-term HIV-1 infection, building on the foundation we have established. In the future, I would love to transition into more translational research, where I can help bridge the gap between scientific discoveries and real-world applications. I have always seen myself dedicating my life to helping others, and I believe that focusing on research with direct clinical impact is the best way for me to contribute meaningfully to improving patient outcomes.

Alexandre Legrand: I’m currently doing a post-doctorate in Paris, but I’m still interested in immunity and would like to take the competitive entrance exam to try and get a permanent position in public research. I’d like to continue exploring the field of immunity and the virus-host relationship, making a collaborative contribution to the advancement of knowledge.