Gavin Robert Screaton

Deglycosylated (N153Q) dengue virus (DENV) mutant shows attenuated infection in a mouse model, mainly due to its increased antibody susceptibility. This is consistent with the neutralization assay showing human monoclonal antibodies 2D22 and C10 are more potent towards the mutant than the wild-type (WT) virus. Here, we compared the cryoEM structures of WT and mutant viruses complexed with these Fabs at 37 °C (2.7–3.2 Å resolution). We observed increased occupancies for both Fabs on the mutant virus, suggesting higher accessibility of epitopes that were previously blocked by glycosylation. Using biolayer interferometry, we showed that at 30 °C, the antibodies exhibited a slower binding rate with the mutant than with WT virus, along with a slower dissociation rate. However, at 37 °C, the affinities of both antibodies for DENV2 WT and N153Q increased significantly. N153Q mutant might be a good vaccine candidate, as important epitopes are made more accessible for stimulating highly potent antibodies.

Deglycosylated (N153Q) dengue virus (DENV) mutant shows attenuated infection in a mouse model, mainly due to its increased antibody susceptibility. This is consistent with the neutralization assay showing human monoclonal antibodies 2D22 and C10 are more potent towards the mutant than the wild-type (WT) virus. Here, we compared the cryoEM structures of WT and mutant viruses complexed with these Fabs (2.7-3.2 Å resolution). We observed increased occupancies for both Fabs on the mutant virus, suggesting higher accessibility of epitopes that were previously blocked by glycosylation. Using biolayer interferometry, we showed although the Fabs have slower binding rate to the mutant than WT virus, they also have slower dissociation rate. The slow dissociation rate might contribute to higher Fab occupancies, as once bound, they remain associated with the virus. N153Q mutant might be a good vaccine candidate, as important epitopes are made more accessible for stimulating highly potent antibodies.

Diverse human viruses deploy a common immune-evasion strategy: viral 2'-O-methylation coupled with STAT2 antagonism. Yet the importance of this coupling and whether targeting the coupled functions offers benefits in vaccine development, remains unknown. Using deep mutational scanning of the dengue NS5 protein, we discovered that the two immune-evasion functions work synergistically to cripple interferon signaling. Disrupting this synergy exposes a reciprocal regulatory relationship between the host proteins IFIT1 and STAT2 that controls both viral restriction and immune cell activation. Dengue viruses with mutations that disrupt the synergy are potently attenuated yet trigger antigen-presenting cell activation that exceeds a licensed dengue vaccine benchmark. Our results establish a generalizable principle: targeting synergies between viral immune evasion mechanisms can simultaneously achieve maximal viral attenuation and innate immune priming. This work provides a rational design framework for developing high-performance vaccines against many human viruses that exploit the IFIT1-STAT2 axis.

BA.3.2, a saltation variant of SARS-CoV-2 has 73 mutations in the spike sequence compared to ancestral Wuhan spike. BA.3, isolated from South Africa in November 2021 at a similar time to the BA.1 and BA.2 Omicron sub-lineages, appeared to fade out, however BA.3.2 was identified in South Africa in late 2024 and subsequently detected in other countries, maintaining a low-level presence. More recently derivatives of BA.3.2, largely BA.3.2.2, have markedly increased, comprising 13% (272/2099) of sequences deposited in March 2026 and have become dominant in several countries. Here we compare the neutralization capacity of serum collected a year ago from vaccinated volunteers and find that BA.3.2.2 is not more difficult to neutralize than other contemporaneously circulating strains such as XFG. However, we find that BA.3.2.2 is not neutralized by most of a panel of mAbs which potently neutralize the JN.1 variant. We explain this by structural analyses and suggest that the large evolutionary distance between JN.1-related variants and BA.3.2.2 is skewing the immune responses, increasing susceptibility to BA.3.2.2 accounting for its current uptick. Furthermore, structure and affinity measurements reveal a significantly remodelled RBD in the down configuration and increased affinity for ACE2. Finally, we looked at escape of BA.3.2.2 from commercially produced therapeutic mAbs and find that BA.3.2.2 has regained susceptibility to two mAbs produced by AstraZeneca.

Dengue virus (DENV) is a major global health threat, with secondary heterotypic infections potentially inducing detrimental memory immune responses. Antigen-specific CD8 + T cells contribute to both protection and pathogenicity, yet how their phenotypic heterogeneity relates to disease severity remains unclear. Here, we performed plate-based single-cell RNA sequencing of circulating DENV-specific CD8 + T cells identified by HLA tetramers loaded with DENV NS3-derived epitopes. Using tetramer binding to peptides corresponding to the currently and serologically inferred dominant previously infecting serotypes, we identify distinct CD8 + T cell subsets associated with disease severity. Asymptomatic dengue is enriched for lower tetramer binding cells with moderate cytotoxic programs, whereas dengue hemorrhagic fever is associated with high tetramer binding CX3CR1 + CD8 + T cells exhibiting enhanced expression of genes related to T cell receptor signaling and cytotoxicity. T cell receptor repertoires are similar among symptomatic cases but displayed temporal dynamics. Overall, DENV NS3-specific CD8 + T cells across disease severity and time are associated with distinct transcriptomic states and T cell receptor features.

The recent COVID-19 pandemic left behind the lingering question as whether new variants of concern might cause further waves of infection. Thus, it is important to investigate the long-term protection gained via vaccination or exposure to the SARS-CoV-2 virus. Here we compare the evolution of memory T-cell responses following primary infection with subsequent antigen exposures. Single-cell TCR analysis of three dominant SARS-CoV-2 spike-specific CD4⁺ T-cell responses identifies the dominant public TCRα clonotypes pairing with diverse TCRβ clonotypes that associated with mild disease at primary infection. These clonotypes are found at higher frequencies in pre-pandemic repertoires compared to other epitope-specific clonotypes. Longitudinal transcriptomics and TCR analysis, combined with functional evaluation, reveals that the clonotypes persisting 3–4 years post initial infection exhibit distinct functionality compared to those that were lost. Furthermore, spike-specific CD4⁺ T cells at this time point show decreased Th1 signatures and enhanced GZMA-driven cytotoxic transcriptomic profiles that were independent of TCR clonotype and associated with viral suppression. In summary, we identify common public TCRs used by immunodominant spike-specific memory CD4⁺ T-cells, associated with mild disease outcome, which likely play important protective roles to subsequent viral infection events.

Adenoviral (Ad) vectors and mRNA vaccines exhibit distinct patterns of immune responses and reactogenicity, but underpinning mechanisms remain unclear. We longitudinally compared homologous ChAdOx1 nCoV-19 and BNT162b2 vaccination, focusing on cytokine-responsive innate-like lymphocytes—mucosal-associated invariant T (MAIT) cells and Vδ2 ⁺ γδ T cells—which sense and tune innate-adaptive cross-talk. Ad priming elicited robust type I interferon (IFN)–mediated innate-like T cell activation, augmenting T cell responses (innate-to-adaptive signaling), which was dampened at boost by antivector immunity. Conversely, mRNA boosting enhanced innate-like responses, driven by prime-induced spike-specific memory T cell–derived IFN-γ (adaptive-to-innate signaling). Extending the dosing interval dampened inflammation at boost because of waning T cell memory. In a separate vaccine trial, preboost spike-specific T cells predicted severe mRNA reactogenicity regardless of the priming platform or interval. Overall, bidirectional innate-like and adaptive cross-talk, and IFN-γ–licensed innate-like T cells, orchestrate interval-dependent early vaccine responses, suggesting modifiable targets for safer, more effective regimens.

COVID-19 vaccines were updated to address immune escape from variants of concern (VOC). We explored the impact of ancestral/BA.1 bivalent mRNA booster vaccination (Autumn 2022) on peripheral and nasal antibody and T-cell responses to SARS-CoV-2 in 133 healthcare workers, building on previous longitudinal vaccination studies. We demonstrate that maintenance of antibody and T-cell responses up to eighteen months following the third vaccine is at least partially driven by intercurrent infection. Boosting with the bivalent vaccine increases the breadth of circulating and nasal antibodies to spike, which waned over time but was still detectable six months post-dose. T-cell responses are well maintained and highly cross-reactive to VOCs irrespective of booster vaccination. Vaccination strongly boosted nasal IgG, but this was short-lived compared to circulating antibodies. Overall, ongoing COVID-19 vaccination provides benefit, boosting immunity in individuals who have not been recently infected, but new strategies may be needed to provide longer-term nasal immunity.

Most previously authorized clinical antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have lost neutralizing activity to recent variants due to rapid viral evolution. To mitigate such escape, we preemptively enhance AZD3152, an antibody authorized for prophylaxis in immunocompromised individuals. Using deep mutational scanning (DMS) on the SARS-CoV-2 antigen, we identify AZD3152 vulnerabilities at antigen positions F456 and D420. Through two iterations of computational antibody design that integrates structure-based modeling, machine-learning, and experimental validation, we co-optimize AZD3152 against 24 contemporary and previous SARS-CoV-2 variants, as well as 20 potential future escape variants. Our top candidate, 3152-1142, restores full potency (100-fold improvement) against the more recently emerged XBB.1.5+F456L variant that escaped AZD3152, maintains potency against previous variants of concern, and shows no additional vulnerability as assessed by DMS. This preemptive mitigation demonstrates a generalizable approach for optimizing existing antibodies against potential future viral escape.