A ferritin-based COVID-19 nanoparticle vaccine that elicits robust, durable, broad-spectrum neutralizing antisera in non-human primates

While the rapid development of COVID-19 vaccines has been a scientific triumph, the need remains for a globally available vaccine that provides longer-lasting immunity against present and future SARS-CoV-2 variants of concern (VOCs). Here, we describe DCFHP, a ferritin-based, protein-nanoparticle vaccine candidate that, when formulated with aluminum hydroxide as the sole adjuvant (DCFHP-alum), elicits potent and durable neutralizing antisera in non-human primates against known VOCs, including Omicron BQ.1, as well as against SARS-CoV-1. Following a booster ~one year after the initial immunization, DCFHP-alum elicits a robust anamnestic response. To enable global accessibility, we generated a cell line that can enable production of thousands of vaccine doses per liter of cell culture and show that DCFHP-alum maintains potency for at least 14 days at temperatures exceeding standard room temperature. DCFHP-alum has potential as a once-yearly (or less frequent) booster vaccine, and as a primary vaccine for pediatric use including in infants

Elicitation of broadly protective sarbecovirus immunity by receptor-binding domain nanoparticle vaccines

Understanding vaccine-elicited protection against SARS-CoV-2 variants and other sarbecoviruses is key for guiding public health policies. We show that a clinical stage multivalent SARS-CoV-2 spike receptor-binding domain nanoparticle vaccine (RBD-NP) protects mice from SARS-CoV-2 challenge after a single immunization, indicating a potential dose-sparing strategy. We benchmarked serum neutralizing activity elicited by RBD-NP in non-human primates against a lead prefusion-stabilized SARS-CoV-2 spike (HexaPro) using a panel of circulating mutants. Polyclonal antibodies elicited by both vaccines are similarly resilient to many RBD residue substitutions tested although mutations at and surrounding position 484 have negative consequences for neutralization. Mosaic and cocktail nanoparticle immunogens displaying multiple sarbecovirus RBDs elicit broad neutralizing activity in mice and protect mice against SARS-CoV challenge even in the absence of SARS-CoV RBD in the vaccine. This study provides proof of principle that multivalent sarbecovirus RBD-NPs induce heterotypic protection and motivates advancing such broadly protective sarbecovirus vaccines to the clinic

Characterization of an M. marinum Vaccine: Examination of Both Mucosal Immunity and Systemic Immunity in a Fish Model

Mycobacterium marinum (Mm) shares at least 80% amino acid sequence identity with over 3,000 orthologous genes of Mycobacterium tuberculosis (Mtb) and is thus used as a surrogate pathogen for Mtb research. Our laboratory investigates mycobacteriosis using Japanese medaka ( Oryzias latipes) as an aquatic animal model. Mm disease presentation in medaka is similar to Mtb disease presentation in humans, including growth in macrophages, granulomatous lesions, and lifelong chronic disease. We have previously shown that a major route of infection in fish is through an oral route and have thus developed methods to infect medaka with Mm utilizing mosquito larvae as vectors. Recently, our lab was able to show that Mm is able to cross the gut epithelia of medaka in a relatively short-time frame and travel to the underlying submucosa. Therefore, Mm must have the ability to attach to the gut mucosal layer and evade killing by GALT immune cells. Mm is apparently able to exploit macrophages of the mucosal immune system to transport the bacteria to target organs like the head kidney, liver, and spleen for a systemic infection. Utilizing an Mm strain engineered to carry a deletion in the RD-1 region, known to include a number of virulence genes, our lab has shown that mucosal immunity against Mm can be induced in medaka. We have shown that exposure to the mutant RD-1 strain offers some protection against a chronic wild-type oral challenge. Since we know that mutant RD-1 can elicit a mucosal immune response, I tested to see if sensitizing mucosal immunity would also induce systemic immunity by first priming fish with mutant RD-1 and then subsequently challenging them with wild type Mm via an IP route. This thesis demonstrates that mucosal immunity is limited to the gut and thus does not appear to provide broad systemic immunity. Additionally, I tested to see if systemic vaccination would protect against a systemic virulent wild-type challenge by vaccinating and challenging fish via an IP route of infection. Results showed that systemic vaccination does not induce systemic immunity and thus does not protect against an IP injected virulent challenge. Collectively, results from this thesis have shown mutant RD-1 to only be effective as a vaccine against mycobacteriosis if given orally since it was shown to only induce a mucosal immune response and only be protective against an oral virulent wild type challenge

Extended insight into the Mycobacterium chelonae-abscessus complex through whole genome sequencing of Mycobacterium salmoniphilum outbreak and Mycobacterium salmoniphilum-like strains

Members of the Mycobacterium chelonae-abscessus complex (MCAC) are close to the mycobacterial ancestor and includes both human, animal and fish pathogens. We present the genomes of 14 members of this complex: the complete genomes of Mycobacterium salmoniphilum and Mycobacterium chelonae type strains, seven M. salmoniphilum isolates, and five M. salmoniphilum-like strains including strains isolated during an outbreak in an animal facility at Uppsala University. Average nucleotide identity (ANI) analysis and core gene phylogeny revealed that the M. salmoniphilum-like strains are variants of the human pathogen Mycobacterium franklinii and phylogenetically close to Mycobacterium abscessus. Our data further suggested that M. salmoniphilum separates into three branches named group I, II and III with the M. salmoniphilum type strain belonging to group II. Among predicted virulence factors, the presence of phospholipase C (plcC), which is a major virulence factor that makes M. abscessus highly cytotoxic to mouse macrophages, and that M. franklinii originally was isolated from infected humans make it plausible that the outbreak in the animal facility was caused by a M. salmoniphilum-like strain. Interestingly, M. salmoniphilum-like was isolated from tap water suggesting that it can be present in the environment. Moreover, we predicted the presence of mutational hotspots in the M. salmoniphilum isolates and 26% of these hotspots overlap with genes categorized as having roles in virulence, disease and defense. We also provide data about key genes involved in transcription and translation such as sigma factor, ribosomal protein and tRNA genes

Extensive genomic diversity among Mycobacterium marinum strains revealed by whole genome sequencing

Mycobacterium marinum is the causative agent for the tuberculosis-like disease mycobacteriosis in fish and skin lesions in humans. Ubiquitous in its geographical distribution, M. marinum is known to occupy diverse fish as hosts. However, information about its genomic diversity is limited. Here, we provide the genome sequences for 15 M. marinum strains isolated from infected humans and fish. Comparative genomic analysis of these and four available genomes of the M. marinum strains M, E11, MB2 and Europe reveal high genomic diversity among the strains, leading to the conclusion that M. marinum should be divided into two different clusters, the "M"- and the "Aronson"-type. We suggest that these two clusters should be considered to represent two M. marinum subspecies. Our data also show that the M. marinum pan-genome for both groups is open and expanding and we provide data showing high number of mutational hotspots in M. marinum relative to other mycobacteria such as Mycobacterium tuberculosis. This high genomic diversity might be related to the ability of M. marinum to occupy different ecological niches

Visualization of early events in mRNA vaccine delivery in non-human primates via PET–CT and near-infrared imaging

These authors contributed equally : Kevin E. Lindsay, Sushma M. Bhosle and Chiara Zurla.International audienceVisualization of the spatio-temporal trafficking of vaccines after their delivery would help evaluate the efficacy of candidate formulations and aid their rational design for preclinical and translational studies. Here, we show that a dual radionuclide-near-infrared probe allows for quantitative, longitudinal and non-invasive monitoring, via positron emission tomography-computed tomography and near-infrared imaging of cynomolgus macaques, of the trafficking dynamics to draining lymph nodes of a model messenger RNA vaccine labelled with the probe. After intramuscular administration of the vaccine to the monkeys, we observed the dynamics of the mRNA vaccine at the injection site and in the draining lymph nodes, performed cellular analyses of the involved tissues using flow cytometry and identified through immunofluorescence that professional antigen-presenting cells are the primary cells containing the injected mRNA and encoding the antigen. This approach may reveal spatio-temporal determinants of vaccine efficacy in preclinical and translational studies employing large mammals

Delayed vaginal SHIV infection in VRC01 and anti-α4β7 treated rhesus macaques.

VRC01 protects macaques from vaginal SHIV infection after a single high-dose challenge. Infusion of a simianized anti-α4β7 mAb (Rh-α4β7) just prior to, and during repeated vaginal exposures to SIVmac251 partially protected macaques from vaginal SIV infection and rescued CD4+ T cells. To investigate the impact of combining VRC01 and Rh-α4β7 on SHIV infection, 3 groups of macaques were treated with a suboptimal dosing of VRC01 alone or in combination with Rh-α4β7 or with control antibodies prior to the initiation of weekly vaginal exposures to a high dose (1000 TCID50) of SHIVAD8-EO. The combination Rh-α4β7-VRC01 significantly delayed SHIVAD8-EO vaginal infection. Following infection, VRC01-Rh-α4β7-treated macaques maintained higher CD4+ T cell counts and exhibited lower rectal SIV-DNA loads compared to controls. Interestingly, VRC01-Rh-α4β7-treated macaques had fewer IL-17-producing cells in the blood and the gut during the acute phase of infection. Moreover, higher T cell responses to the V2-loop of the SHIVAD8-EO envelope in the VRC01-Rh-α4β7 group inversely correlated with set point viremia. The combination of suboptimal amounts of VRC01 and Rh-α4β7 delayed infection, altered antiviral immune responses and minimized CD4+ T cell loss. Further exploration of the effect of combining bNAbs with Rh-α4β7 on SIV/HIV infection and antiviral immune responses is warranted and may lead to novel preventive and therapeutic strategies

Germline-targeting HIV vaccination induces neutralizing antibodies to the CD4 binding site

Eliciting potent and broadly neutralizing antibodies (bnAbs) is a major goal in HIV-1 vaccine development. Here, we describe how germline-targeting immunogen BG505 SOSIP germline trimer 1.1 (GT1.1), generated through structure-based design, engages a diverse range of VRC01-class bnAb precursors. A single immunization with GT1.1 expands CD4 binding site (CD4bs)–specific VRC01-class B cells in knock-in mice and drives VRC01-class maturation. In nonhuman primates (NHPs), GT1.1 primes CD4bs-specific neutralizing serum responses. Selected monoclonal antibodies (mAbs) isolated from GT1.1-immunized NHPs neutralize fully glycosylated BG505 virus. Two mAbs, 12C11 and 21N13, neutralize subsets of diverse heterologous neutralization-resistant viruses. High-resolution structures revealed that 21N13 targets the same conserved residues in the CD4bs as VRC01-class and CH235-class bnAbs despite its low sequence similarity (~40%), whereas mAb 12C11 binds predominantly through its heavy chain complementarity-determining regio