Biology subjects

Hilt, Z. T.

Publications and source records attributed to Hilt, Z. T..

3 recordsLinked to original sources

bioRxiv2025

Humanizing a CD28 signaling domain affects CD8 activation, exhaustion and stem-like precursors

CD28 ligation provides critical signals that modulate activated T cell fate. In a human to mouse reverse-engineering approach, a single amino acid substitution adjacent to the C-terminal proline-rich domain created CD28A210P mice with enhanced signaling. CD28A210P mice experienced pro-inflammatory responses to CD28 superagonist antibody, analogous to severe cytokine storm induced in a human clinical trial, with a striking increase of activated CD8 T cells. In acute and chronic viral infections, early activation and expansion of CD28A210P CD8 effector T cells increased, with accelerated exhaustion in chronic infection. Mechanistically, CD28A210P enhanced JunB, IL-2, and inhibitory receptors driven by MEK1/2. Generation of CD28A210P stem-like progenitor (Tpex) cells was enhanced in acute and chronic infections, and further expanded by PD-L1 blockade in chronically-infected mice. Thus, humanized PYAP mice reveal key roles for CD28 signaling strength in CD8 activation, accelerating exhaustion during antigen persistence, while promoting and sustaining Tpex during acute and chronic viral infection. One sentence SummaryA single amino acid substitution adjacent to PYAP to humanize CD28 signaling enhances superagonist response, early CD8 activation and Tpex generation during viral infection while accelerating exhaustion and sustaining Tpex during chronic infection. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=101 SRC="FIGDIR/small/642460v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@13fc9f9org.highwire.dtl.DTLVardef@e50762org.highwire.dtl.DTLVardef@47c8eeorg.highwire.dtl.DTLVardef@d892d7_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical Abstract:C_FLOATNO Humanized CD28 PYAPP enhances numbers of CD8 T cell effectors and stem-like precursors during acute viral infection, and accelerates exhaustion while sustaining increased self-renewing Tpex cells that are favored during PD-L1 blockade. C_FIG

immunology↗

bioRxiv2025

Recent thymic emigrants are preferentially recruited into the memory pool during persistent infection

Cytomegalovirus (CMV) leads to a unique phenomenon known as memory inflation, where antigen-specific memory CD8+ T cells continue to accumulate in the peripheral tissues during the latent stage of infection. However, it is still not clear how the inflating pool of memory CD8+ T cells is generated and maintained. In this study, we used murine cytomegalovirus (MCMV) as a model of persistent infection and fate-mapping mice to determine the dynamics of CD8+ T cell recruitment into the memory pool. We found that neonatal exposure to CMV leads to an expansion of newly made CD8+ T cells (recent thymic emigrants, RTEs), which are maintained in the long-lived memory compartment. In contrast, CD8+ T cells made during the latent phase of infection (mature CD8+ T cells) contribute little to the memory pool. We also observed notable phenotypic differences between RTEs and mature cells. Whereas RTEs present at the time of infection gave rise to more effector memory cells, the cells produced later in infection were biased towards becoming central memory cells. Importantly, the preferential recruitment of RTEs into the effector memory pool also occurs during adult exposure to CMV. Collectively, these data demonstrate that persistent infection expands the RTE population, and timing of infection dictates whether neonatal or adult RTEs are locked in to the memory pool. Author SummaryFollowing infection with CMV, CD8+ T cells accumulate in the blood and peripheral organs over time, a feature termed memory inflation. However, it is not clear whether memory inflation is due to the continuous recruitment of cells made during the latent stage of infection or expansion of CD8+ T cells that were present at the time of infection. To address this question, we used a fate-mapping mouse model and examined the recruitment of CD8+ T cells that were produced during different stages of infection. Surprisingly, we discovered that CD8+ T cells exported from the thymus just prior to infection are preferentially recruited and maintained in the memory pool. In contrast, CD8+ T cells made during the latent stage contribute minimally to the inflating pool and exhibit a less differentiated phenotype. These results provide a new conceptual framework for understanding how the memory pool is generated and maintained after persistent viral infection.

immunology↗

bioRxiv2024

Enhanced RNA replication and pathogenesis in recent SARS-CoV-2 variants harboring the L260F mutation in NSP6

The COVID-19 pandemic has been driven by SARS-CoV-2 variants with enhanced transmission and immune escape. Apart from extensive evolution in the Spike protein, non-Spike mutations are accumulating across the entire viral genome and their functional impact is not well understood. To address the contribution of these mutations, we reconstructed genomes of recent Omicron variants with disabled Spike expression (replicons) to systematically compare their RNA replication capabilities independently from Spike. We also used a single reference replicon and complemented it with various Omicron variant Spike proteins to quantify viral entry capabilities in single-round infection assays. Viral entry and RNA replication were negatively correlated, suggesting that as variants evolve reduced entry functions under growing immune pressure on Spike, RNA replication increases as a compensatory mechanism. We identified multiple mutations across the viral genome that enhanced viral RNA replication. NSP6 emerged as a hotspot with a distinct L260F mutation independently arising in the BQ.1.1 and XBB.1.16 variants. Using mutant and revertant NSP6 viral clones, the L260F mutation was validated to enhance viral replication in cells and increase pathogenesis in mice. Notably, this mutation enhanced host lipid droplet consumption by NSP6 without impacting its known ER-zippering function or double-membrane vesicle morphology. Collectively, a systematic analysis of RNA replication of recent Omicron variants defined NSP6s key role in viral RNA replication that provides insight into evolutionary trajectories of recent variants with possible therapeutic implications. Author SummaryAs SARS-CoV-2 continues to spread and adapt in humans, viral variants with enhanced spread and immune evasion have emerged throughout the COVID-19 pandemic. While most of the mutations occur in the Spike protein and have been extensively studied, non-Spike mutations have been accumulating and are not as well understood. Here, we constructed Spike-defective genomes of recent Omicron variants and systematically compared their RNA replication capabilities independently from Spike. We also performed single-round infection assays with various Omicron variant Spike proteins to quantify viral entry capabilities. Interestingly, viral entry and RNA replication were negatively correlated, suggesting that as variants evolved reduced entry functions under growing immune pressure on Spike, RNA replication increased as a compensatory mechanism. We focused on a viral protein NSP6 that acquired mutations that significantly enhanced RNA replication. We validated that a frequently accessed L260F mutation in NSP6 enhanced viral infection in cells and increased pathogenesis in mice. While the mutation did not alter NSP6s role in maintaining a membranous network of viral replication factories, the mutation enhanced viral hijacking of the host lipid droplet machinery. Collectively, we highlight the important role of non-Spike mutations in the evolutionary trajectories of SARS-CoV-2 variants with possible monitoring and therapeutic implications.

microbiology↗