Biology subjects

Lahoud, M. H.

Publications and source records attributed to Lahoud, M. H..

4 recordsLinked to original sources

bioRxiv2025

Intranasal sarbecovirus vaccine booster elicits cross-clade, durable and protective systemic and mucosal immunity

Short-lived, clade-specific immune responses with limited mucosal priming are limitations faced by current COVID-19 mRNA vaccines against sarbecoviruses. We have developed a nasal booster vaccine candidate that induced robust and sustained, cross-clade, systemic and mucosal protective immunity. Two recombinant Clec9A-specific monoclonal antibodies fused to the Receptor Binding Domain (RBD) from Omicron XBB.1.5 and SARS-CoV-1, respectively were generated. In Comirnaty mRNA-vaccinated mice, boosting with each individual Clec9A-RBD construct induced immune responses that either were limited in breadth or waned over time; while boosting with both constructs combined (Clec9AOMNI) elicited robust cross-clade neutralizing antibodies (nAb) and T cell responses that were significantly more sustained compared to Bivalent Comirnaty (BC) mRNA vaccine booster. The persistence of RBD-specific follicular helper CD4+ T cells, germinal centre B cells, and long-lived plasma cells that facilitated affinity maturation in Clec9AOMNI-boosted mice, correlated with the detection of triple cross-reactive B cells that bind to ancestral SARS-CoV-2 ancestral, SARS-CoV-2 XBB.1.5 and SARS-CoV-1 RBD. Remarkably, intranasal boosting with Clec9AOMNI generated robust and sustained mucosal immune responses in the upper and lower respiratory compartments, including RBD-specific IgA, cross-clade nAb and cellular immunity together with functional tissue-resident memory T cells, without compromising the systemic immune responses. Correspondingly, Clec9AOMNI booster conferred superior protection against Omicron BA.1 compared to BC booster when challenge was performed at six months post-boost. Hence, Clec9AOMNI is a promising nasal booster vaccine candidate that has the potential to mitigate pandemic threats from emerging sarbecoviruses. One Sentence SummaryNasal booster immunization with dendritic cell-targeting vaccine candidate in mRNA-vaccinated mice induced cross-clade, sustained, systemic and mucosal protective immunity.

immunology↗

bioRxiv2024

Long lived liver-resident memory T cells of biased specificities for abundant sporozoite antigens drive malaria protection by radiation-attenuated sporozoite vaccination

Vaccination with radiation-attenuated sporozoites (RAS) can provide highly effective protection against malaria in both humans and mice. To extend understanding of malaria immunity and inform the development of future vaccines, we studied the protective response elicited by this vaccine in C57BL/6 mice. We reveal that successive doses of Plasmodium berghei RAS favour the generation of liver CD8+ tissue-resident memory T cells (TRM cells) over circulating memory cells, and markedly enhance their longevity. Importantly, RAS immunisation strongly skews the composition of the liver CD8+ TRM compartment towards cells specific for abundant sporozoite antigens, such as thrombospondin-related adhesive protein (TRAP) and circumsporozoite protein (CSP), which become major mediators of protection. The increased prevalence of sporozoite specificities is associated with limited intrahepatic parasite development and inhibition of naive T cell responses to all parasite antigens in previously vaccinated mice. This leads to the exclusive expansion of effector T cells formed upon initial immunisation, ultimately reducing the diversity of the liver TRM pool later established. These findings provide novel insights into the mechanisms governing malaria immunity induced by attenuated sporozoite vaccination and highlight the susceptibility of this vaccine to limitations imposed by strain-specific immunity associated with the abundant, yet highly variable sporozoite antigens CSP and TRAP. Author SummaryMalaria remains a significant global health challenge. An efficient vaccine could significantly enhance malaria control. Vaccination with radiation-attenuated sporozoites (RAS) can induce highly efficient protection against malaria, and our study brings critical insights into the protective mechanisms elicited by this vaccine. We show that RAS stimulates the formation of parasite-specific cytotoxic memory T cells that permanently reside in the liver (liver TRM cells). These cells are critical mediators of protection. Interestingly, multiple doses of RAS extend the lifespan of these memory cells, potentially improving long term immunity. However, we found that the induced memory T cell response is strongly skewed towards abundant, but highly variable, sporozoite proteins. Thus, this phenomenon exposes a potential limitation of the RAS vaccine against the great parasite diversity in the field, as it focuses the T cell response away from less abundant, but more conserved, parasite antigens.

immunology↗

bioRxiv2024

A Simple and Rapid Protocol for the Isolation of Murine Bone Marrow Suitable for the Differentiation of Dendritic Cells

The generation of bone marrow-derived dendritic cells is a widely used approach in immunological research to study antigen processing and presentation as well as T cell activation responses. However, the initial step of isolating the bone marrow can be time-consuming, especially when larger numbers of precursor cells are required. Here, we assessed whether an accelerated bone marrow isolation method using centrifugation is suitable for the differentiation of FMS-like tyrosine kinase 3 ligand-driven dendritic cells. Compared to the conventional flushing method, the centrifugation-based isolation method resulted in a similar bone marrow cell yield on day 0, increased cell numbers by day 8, similar proportions of dendritic cell subsets, and consequently a higher number of type 1 conventional dendritic cells (cDC1) from the culture. Although the primary purpose of the method optimization was to improve experimental efficiency and increase the output of cDC1s, the protocol is also compatible with the differentiation of other dendritic cell subsets such as cDC2 and plasmacytoid dendritic cells, with an improved output cell count and a consistent phenotype.

immunology↗

bioRxiv2023

Single shot dendritic cell targeting SARS-CoV-2 vaccine candidate induces broad and durable systemic and mucosal immune responses

Current COVID-19 vaccines face certain limitations, which include waning immunity, immune escape by SARS-CoV-2 variants, limited CD8+ cellular response, and poor induction of mucosal immunity. Here, we engineered a Clec9A-RBD antibody construct that delivers the Receptor Binding Domain (RBD) from SARS-CoV-2 spike protein to conventional type 1 dendritic cells (cDC1). We showed that single dose immunization with Clec9A-RBD induced high RBD-specific antibody titers with a strong T-helper 1 (TH1) isotype profile and exceptional durability, whereby antibody titers were sustained for at least 21 months post-vaccination. Uniquely, affinity maturation of the antibody response was observed over time, as evidenced by enhanced neutralization potency and breadth across the sarbecovirus family. Consistently and remarkably, RBD-specific T-follicular helper cells and germinal center B cells were still detected at 12 months post-immunization. Increased antibody-dependent cell-mediated cytotoxicity (ADCC) activity of the immune sera was also measured over time with comparable efficacy against ancestral SARS-CoV-2 and variants, including Omicron. Furthermore, Clec9A-RBD immunization induced a durable poly-functional TH1-biased cellular response that was strongly cross-reactive against SARS-CoV-2 variants, including Omicron, and with robust CD8+ T cell signature. Lastly, Clec9A-RBD single dose systemic immunization primed effectively RBD-specific cellular and humoral mucosal immunity in lung. Taken together, Clec9A-RBD immunization has the potential to trigger robust and sustained, systemic and mucosal immune responses against rapidly evolving SARS-CoV2 variants.

immunology↗