Biology subjects

Triccas, J.

Publications and source records attributed to Triccas, J..

4 recordsLinked to original sources

bioRxiv2026

A mobile ESX type VII secretion system enhances intracellular persistence in globally distributed Mycobacterium abscessus

Mycobacterium abscessus are non-tuberculous mycobacteria that are widespread in the environment and of increasing global clinical significance. Accumulating evidence shows that M. abscessus has emerged as an important pathogen, driven by highly drug-resistant lineages, enhanced transmissibility and the acquisition of specific virulence factors. In this study, we describe a previously uncharacterised ESX secretion system encoded on a 123-kbp plasmid identified in a clinical isolate of M. abscessus. This ESX system, termed ESX-pMA07, is distinct from ESX systems previously reported in M. abscessus in both sequence composition and locus organisation, characterised by a unique arrangement of core ESX components and low sequence identity to ESX-3, ESX-4 and plasmid-borne ESX-P systems. ESX-pMA07 was detected in geographically diverse clinical isolates but was restricted to particular genotypes within the global M. abscessus phylogeny. Transcriptional profiling revealed expression of ESX-pMA07 components in artificial cystic fibrosis media and during intracellular growth in macrophage cell lines. Using CRISPR interference, we show that inducible silencing of eccC, encoding the ATPase component of ESX-pMA07, significantly reduced intracellular survival of M. abscessus within macrophages. To our knowledge, this is the first characterisation of a functional, plasmid-borne ESX secretion system in M. abscessus, demonstrating that mobile genetic elements contribute to the pathogens intracellular persistence and may influence its evolving virulence. Author SummaryMycobacterium abscessus is a rapidly emerging, highly drug-resistant bacterium that causes chronic infections, particularly in people with underlying lung disease such as cystic fibrosis. The factors that enable certain M. abscessus strains to persist inside host cells are not fully understood. In this study, we identified a previously unrecognised type VII secretion system (ESX) encoded on a large plasmid in a clinical isolate of M. abscessus. This plasmid-borne ESX system, which we termed ESX-pMA07, is genetically distinct from the ESX systems normally found on the chromosome and was detected in geographically diverse clinical isolates, but restricted to specific lineages within the global M. abscessus population. We show that ESX-pMA07 genes are expressed under conditions relevant to lung infection and during intracellular growth in macrophages. Using inducible CRISPR interference to silence the ESX ATPase gene eccC, we demonstrate that ESX-pMA07 contributes to intracellular survival of M. abscessus in macrophages. These findings reveal that mobile genetic elements can encode functional secretion systems that enhance intracellular persistence, providing a mechanism for the emergence and spread of virulence traits in this important pathogen.

microbiology↗

bioRxiv2024

A Single Chimeric Spike Antigen Induces Pan-Sarbecovirus Immunity

Next-generation vaccines are required to address the evolving nature of SARS-CoV-2 and to protect against emerging pandemic threats from other coronaviruses. These vaccines should aim to elicit broad-protection, provide long-lasting immunity and facilitate equitable access for all populations. In this study, a panel of chimeric, full-length spike antigens were developed that incorporate mutations from previous, circulating and predicted SARS-CoV-2 variants. The lead candidate (CoVEXS5) was obtained from a high-yield production process in stable CHO cells with purity of >95%, long-term stability and elicitation of broadly cross-reactive neutralising antibodies when delivered to mice in a squalene emulsion adjuvant (Sepivac SWE). In both mice and hamsters, CoVEXS5 immunisation reduced clinical disease signs, lung inflammation and organ viral titres after SARS-CoV-2 infection, including challenge with the highly immunoevasive Omicron XBB.1.5 subvariant. In mice previously primed with a licenced protein vaccine (NVX-CoV2373), CoVEXS5 could boost T cell immunity, as well as neutralising antibodies levels against viruses from three sarbecoviruses clades. The breadth of sarbecovirus cross-reactivity elicited by CoVEXS5 exceeded that observed after boosting with the NVX-CoV2373 vaccine. These findings highlight the potential of a chimeric spike antigen, formulated in an open-access adjuvant, as a next-generation vaccine candidate to enhance cross-protection against emerging sarbecoviruses in vaccinated populations globally.

immunology↗

bioRxiv2024

An LNP-mRNA vaccine provides potent immunogenicity and protection against Mycobacterium tuberculosis

Mycobacterium tuberculosis remains the largest infectious cause of mortality worldwide, even with over a century of widespread administration of the only licensed tuberculosis (TB) vaccine, Bacillus Calmette-Guerin (BCG). mRNA technology remains an underexplored approach for combating chronic bacterial infections such as TB. We have developed a lipid nanoparticle (LNP)-mRNA vaccine encoding for a fusion protein of two immunogenic TB antigens, termed mRNACV2. In C57BL/6 mice intramuscularly vaccinated with mRNACV2, high frequencies of polyfunctional, antigen-specific Th1 CD4+ T cells were observed in the blood and lungs, which was associated with the rapid recruitment of both innate and adaptive immune cells to lymph nodes draining the site of immunisation. mRNACV2 vaccination provided significant pulmonary protection in M. tuberculosis-infected mice, reducing bacterial load and inflammatory infiltration in the lungs. As BCG is widely administered in infants in TB endemic countries, new TB vaccines should be able to boost the effects of BCG. Importantly, mRNACV2 enhanced immune responses and long-term protection when used to boost BCG-primed mice. These findings, which provide the first report of a highly protective LNP-mRNA vaccine for TB, highlight the potential of the LNP-mRNA platform for TB control and support further research to facilitate translation to humans.

immunology↗

bioRxiv2021

Immunisation of ferrets and mice with recombinant SARS-CoV-2 spike protein formulated with Advax-SM adjuvant protects against COVID-19 infection

The development of a safe and effective vaccine is a key requirement to overcoming the COVID-19 pandemic. Recombinant proteins represent the most reliable and safe vaccine approach but generally require a suitable adjuvant for robust and durable immunity. We used the SARS-CoV-2 genomic sequence and in silico structural modelling to design a recombinant spike protein vaccine (Covax-19). A synthetic gene encoding the spike extracellular domain (ECD) was inserted into a baculovirus backbone to express the protein in insect cell cultures. The spike ECD was formulated with Advax-SM adjuvant and first tested for immunogenicity in C57BL/6 and BALB/c mice. The Advax-SM adjuvanted vaccine induced high titers of binding antibody against spike protein that were able to neutralise the original wildtype virus on which the vaccine was based as well as the variant B.1.1.7 lineage virus. The Covax-19 vaccine also induced potent spike-specific CD4+ and CD8+ memory T-cells with a dominant Th1 phenotype, and this was shown to be associated with cytotoxic T lymphocyte killing of spike labelled target cells in vivo. Ferrets immunised with Covax-19 vaccine intramuscularly twice 2 weeks apart made spike receptor binding domain (RBD) IgG and were protected against an intranasal challenge with SARS-CoV-2 virus 2 weeks after the second immunisation. Notably, ferrets that received two 25 or 50g doses of Covax-19 vaccine had no detectable virus in their lungs or in nasal washes at day 3 post-challenge, suggesting the possibility that Covax-19 vaccine may in addition to protection against lung infection also have the potential to block virus transmission. This data supports advancement of Covax-19 vaccine into human clinical trials.

immunology↗