Randomized, Open-Label Phase 3 Study Evaluating Immunogenicity, Safety, and Reactogenicity of RSVPreF3 OA Coadministered with FLU-QIV-HD in Adults Aged ≥ 65.

INTRODUCTION: Respiratory syncytial virus (RSV) and influenza pose major disease burdens in older adults due to an aging immune system and comorbidities; seasonal overlap exists between these infections. In 2023, the RSV prefusion protein F3 older adult (RSVPreF3 OA) vaccine was first approved in the USA as a single dose for prevention of lower respiratory tract disease due to RSV in adults aged ≥ 60 years. The vaccine has since been approved in the European Union and elsewhere. RSVPreF3 OA and FLU-QIV-HD could be coadministered if immunogenicity, safety, and reactogenicity are not affected. METHODS: This open-label, randomized (1:1), controlled, phase 3 study in 1029 adults aged ≥ 65 years in the USA evaluated the immunogenicity (up to 1 month after last vaccine dose) and safety (up to 6 months after last vaccine dose) of RSVPreF3 OA coadministered with FLU-QIV-HD (co-ad group) versus FLU-QIV-HD alone followed by RSVPreF3 OA at a separate visit 1 month later (control group). Non-inferiority criterion was defined as an upper limit of the two-sided 95% confidence interval of the geometric mean titer (GMT) group ratio (control/co-ad) ≤ 1.5. Secondary endpoints included safety and reactogenicity. RESULTS: Proportions of participants across age categories between groups and proportions of male (50.4%) and female (49.6%) participants were well balanced; most participants were white (68.7%). Group GMT ratios for RSV-A neutralizing titers, hemagglutination inhibition titers for four influenza vaccine strains, and RSV-B neutralizing titers were non-inferior in the co-ad group versus the control group. No clinically meaningful differences in local or systemic solicited and unsolicited adverse events (AEs), serious AEs, and potential immune-mediated diseases were identified. The most common solicited AEs in both groups were injection-site pain and myalgia. CONCLUSION: In adults aged ≥ 65 years, coadministration of RSVPreF3 OA and FLU-QIV-HD was immunogenically non-inferior to the sequential administration of both vaccines 1 month apart, and had clinically acceptable safety and reactogenicity profile. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT05559476.

Adults aged 65 years or older are vulnerable to infections caused by influenza and respiratory syncytial viruses, due to an aging immune system and other underlying conditions. Infections with both viruses increase during autumn and winter seasons in temperate climates. In 2023, a vaccine against respiratory syncytial virus, called RSVPreF3 OA, was first approved for use in adults aged 60 years or older in the USA; the vaccine has since also been approved in the European Union and elsewhere. Giving RSVPreF3 OA in the same vaccination visit (coadministration) with a high-dose influenza vaccine, called FLU-QIV-HD, which is given to adults aged 65 years or older, could help protect against both respiratory syncytial virus and influenza. This article reports the results of a phase 3 trial comparing coadministration of the RSVPreF3 OA and FLU-QIV-HD vaccines with sequential administration (FLU-QIV-HD followed by RSVPreF3 OA 1 month later) in 1029 adults aged 65 years or older in the USA. Proportions of participants across age categories between groups, and the proportions of male (50.4%) and female (49.6%) participants were well balanced; most participants were white (68.7%). Immune response to both the vaccines among participants in the coadministration arm was non-inferior to that in the sequential arm. Coadministration was well tolerated, with no meaningful differences in adverse reactions to the vaccines compared with sequential administration. The most common adverse reactions were pain at the injection site and muscle aches. This study supports the coadministration of RSVPreF3 OA and FLU-QIV-HD in adults aged 65 years or older.

Patient experience surveys are vital in the twenty-first century: let's put some myths to rest.

Patient-reported data derived from surveys places patient feedback at the heart of quality improvement and health system responsiveness. Such surveys are not without critics, however, who contend that there are better ways to collect feedback. Criticisms assert that response rates are too low and measures are not robust, valid or reliable, that patient experience surveys are neither valid nor reliable for Maori and Pacific peoples and that such surveys do not contribute to improved outcomes for patients. We debunk these myths in the context of the Te Tahu Hauora Health Quality & Safety Commission (Te Tahu Hauora) patient experience survey programme. We explain the centrality of a strong consumer and whanau voice in a twenty-first century health system, and that listening to and acting on this voice-including use of patient-reported data-is now a statutory requirement for health entities under the Pae Ora (Healthy Futures) Act 2022. We describe the different surveys in the programme and explain the differences between patient satisfaction and patient experience. We address sample size and response rates, including representativeness in the surveys of Maori and Pacific peoples' experience. We look at how survey data can be used for quality improvement and to guide us toward providing equitable, culturally safe care. We assert that, contrary to criticisms, the programme delivers valid, reliable, relevant, systematic and practical patient experience surveys and resulting data, with guides for improvement, and that we are both legally and ethically bound to listen to and use these results to improve the healthcare we deliver.

Finding an Appropriate Mouse Model to Study the Impact of a Treatment for Friedreich Ataxia on the Behavioral Phenotype.

Friedreich ataxia (FRDA) is a progressive neurodegenerative disease caused by a GAA repeat in the intron 1 of the frataxin gene (FXN) leading to a lower expression of the frataxin protein. The YG8sR mice are Knock-Out (KO) for their murine frataxin gene but contain a human frataxin transgene derived from an FRDA patient with 300 GAA repeats. These mice are used as a FRDA model but even with a low frataxin concentration, their phenotype is mild. We aimed to find an optimized mouse model with a phenotype comparable to the human patients to study the impact of therapy on the phenotype. We compared two mouse models: the YG8sR injected with an AAV. PHP.B coding for a shRNA targeting the human frataxin gene and the YG8-800, a new mouse model with a human transgene containing 800 GAA repeats. Both mouse models were compared to Y47R mice containing nine GAA repeats that were considered healthy mice. Behavior tests (parallel rod floor apparatus, hanging test, inverted T beam, and notched beam test) were carried out from 2 to 11 months and significant differences were noticed for both YG8sR mice injected with an anti-FXN shRNA and the YG8-800 mice compared to healthy mice. In conclusion, YG8sR mice have a slight phenotype, and injecting them with an AAV-PHP.B expressing an shRNA targeting frataxin does increase their phenotype. The YG8-800 mice have a phenotype comparable to the human ataxic phenotype.

Removal of the GAA repeat in the heart of a Friedreich's ataxia mouse model using CjCas9.

Most Friedreich ataxia (FRDA) cases are caused by the elongation of the GAA repeat (GAAr) sequence in the first intron of the FXN gene, leading to a decrease of the frataxin protein expression. Deletion of this GAAr with CRISPR/Cas9 technology leads to an increase in frataxin expression in vitro. We are therefore aiming to develop FRDA treatment based on the deletion of GAAr with CRISPR/Cas9 technology using a single AAV expressing a small Cas9 (CjCas9) and two single guide RNAs (sgRNAs) targeting the FXN gene. This AAV was intraperitoneally administrated to YG8sR (250-300 GAAr) and to YG8-800 (800 GAAr) mice. DNA and RNA were extracted from different organs a month later. PCR amplification of part of intron 1 of the FXN gene detected some GAAr deletion in some cells in heart and liver of both mouse models, but the editing rate was not sufficient to cause an increase in frataxin mRNA in the heart. However, the correlation observed between the editing rate and the distribution of AAV suggests a possible therapy based on the removal of the GAAr with a better delivery tool of the CRISPR/Cas9 system.

A promising mouse model for Friedreich Ataxia progressing like human patients.

Friedreich Ataxia (FRDA) is a genetic disease caused by an expended GAA repeat in the FXN gene leading to a reduction in frataxin protein production. Frataxin is an essential protein involved in mitochondrial iron-sulfur-cluster formation, its absence affecting numerous cellular rections. In patients, the disease leads to a progressive neuromuscular degeneration and, most of the time, death from heart failure. In order to determine if a treatment is effective or not, it is essential to have the mouse model, which best reflects all of the characteristics of this disease. Many groups were working on the creation of mouse models by decreasing the mouse frataxin or knocking it out, by introducing a transgene with a human frataxin with long GAA repeat. Most of the mouse models are limited to one problem, either neurologic or cardiac symptoms, and, for those who have both, generally these symptoms are too severe and mice have a very short life span, which does not reflect the human disease's progression. Jackson Laboratories Inc. developed a new mouse model that has 800 GAA repeats. We demonstrate here that these mice accurately reflect the human disease with a progressive neuromuscular degeneration highlighted by the two beam tests and the beginning of heart hypertrophy at 26 weeks. YG8-800 mice are thus currently a promising mouse model for FRDA.

Persisting variance in middle ear ventilation tube insertion in Auckland children: why ethnic disparity continues.

AIM: Insertion of ventilation tubes (VTs) is a common surgical treatment for recurrent and persistent otitis media, but surgical practice varies internationally. The current study explored variations in practice within New Zealand by examining VT insertion rates. The aim of the study was to determine time trends and current variations in VT insertion rates by ethnicity and district health board (DHB), with a focus on comparison of two DHBs in Auckland (Counties Manukau and Auckland DHB) to national average data. METHOD: Data for surgical procedures were analysed in the Atlas of Healthcare Variation domain, available via the Health Quality & Safety Commission website. Publicly funded events for New Zealand residents over a 10-year period (2009-2018) were examined for 0-4-year-olds. Individuals were assigned to their DHB of residence. VT rates for each DHB are presented per 1,000 population, with upper and lower confidence intervals calculated to the 95% level. RESULTS: There was a general decline in the rates of VT insertions for the 0-4-year-olds over the 2009-2018 decade. Analysis of the 2018 year showed variation by ethnicity and DHB. In CMDHB, ADHB and nationally, Asian and Pacific ethnic groups had the lowest rates of VT insertions compared to other ethnic groups. In CMDHB, the VT rates for Maori, Pacific and Asian children were less than half that of their respective groups in ADHB. The NZ European/Other ethnic group had the highest rates of VT insertions in CMDHB and nationally, but in ADHB, the rate for the NZ European/Other group was similar to that for Maori. CONCLUSION: These results are incongruent with evidence that Maori and Pacific children in New Zealand experience a greater burden of middle ear disease than NZ European children. The finding of persisting inequities in VT treatment for middle ear disease in 0-4-year-olds, with greatest impact on Pacific children, suggests that there may be a need for targeted middle ear screening for preschool children to detect pre-schoolers with ear disease, earlier than the 4-year-old B4 School Check.

Serum extracellular vesicles for delivery of CRISPR-CAS9 ribonucleoproteins to modify the dystrophin gene.

Extracellular vesicles (EVs) mediate intercellular biomolecule exchanges in the body, making them promising delivery vehicles for therapeutic cargo. Genetic engineering by the CRISPR system is an interesting therapeutic avenue for genetic diseases such as Duchenne muscular dystrophy (DMD). We developed a simple method for loading EVs with CRISPR ribonucleoproteins (RNPs) consisting of SpCas9 proteins and guide RNAs (gRNAs). EVs were first purified from human or mouse serum using ultrafiltration and size-exclusion chromatography. Using protein transfectant to load RNPs into serum EVs, we showed that EVs are good carriers of RNPs in vitro and restored the expression of the tdTomato fluorescent protein in muscle fibers of Ai9 mice. EVs carrying RNPs targeting introns 22 and 24 of the DMD gene were also injected into muscles of mdx mice having a non-sense mutation in exon 23. Up to 19% of the cDNA extracted from treated mdx mice had the intended deletion of exons 23 and 24, allowing dystrophin expression in muscle fibers. RNPs alone, without EVs, were inefficient in generating detectable deletions in mouse muscles. This method opens new opportunities for rapid and safe delivery of CRISPR components to treat DMD.

Whole-blood cytokine secretion assay as a high-throughput alternative for assessing the cell-mediated immunity profile after two doses of an adjuvanted SARS-CoV-2 recombinant protein vaccine candidate.

OBJECTIVES: We previously described the Phase I-II evaluation of SARS-CoV-2 recombinant protein candidate vaccine, CoV2-PreS-dTM, with AF03- or AS03-adjuvant systems (ClinicalTrials.gov, NCT04537208). Here, we further characterise the cellular immunogenicity profile of this vaccine candidate using a whole-blood secretion assay in parallel to intracellular cytokine staining (ICS) of cryopreserved peripheral blood mononuclear cells (PBMCs). METHODS: A randomly allocated subset of 90 healthy, SARS-CoV-2-seronegative adults aged ≥ 18 years who had received (random allocation) one or two separate injections (on study day [D]1 and D22) of saline placebo or CoV2-PreS-dTM formulated with AS03 or AF03 were included. Cytokine secretion was assessed using a TruCulture® whole-blood stimulation system in combination with multiplex bead array, and intracellular cytokine profiles were evaluated on thawed PBMCs following ex vivo stimulation with recombinant S protein at pre-vaccination (D1), post-dose 1 (D22) and post-dose 2 (D36). RESULTS: Both methods detected similar vaccine-induced responses after the first and second doses. We observed a Th1 bias (Th1/Th2 ratio > 1.0) for most treatment groups when analysed in whole blood, mainly characterised by increased IFN-γ, IL-2 and TNF-α secretion. Among participants aged ≥ 50 years, the Th1/Th2 ratio was higher for those who received vaccine candidate with AS03 versus AF03 adjuvant. ICS revealed that this higher Th1/Th2 ratio resulted from higher levels of IFN-γ expression and that the vaccine induced polyfunctional CD4+ T cells. CONCLUSIONS: The whole-blood cytokine secretion assay is a high-throughput alternative for assessing the quantity and character of vaccine-induced cellular responses.

Role for the metalloproteinase ADAM28 in the control of airway inflammation, remodelling and responsiveness in asthma.

Background: Asthma is characterized by morphological modifications of the airways (inflammation and remodelling) and bronchial hyperresponsiveness. Mechanisms linking these two key features of asthma are still poorly understood. ADAM28 (a disintegrin and metalloproteinase 28) might play a role in asthma pathophysiology. ADAM28 exists as membrane-bound and soluble forms and is mainly expressed by lymphocytes and epithelial cells. Methods: ADAM28-/- mice and ADAM28+/+ counterparts were sensitized and exposed to ovalbumin (OVA). Airway responsiveness was measured using the flexiVent® system. After sacrifice, bronchoalveolar lavage (BAL) was performed and lungs were collected for analysis of airway inflammation and remodelling. Results: The expression of the soluble form of ADAM28 was lower in the lungs of OVA-exposed mice (as compared to PBS-exposed mice) and progressively increased in correlation with the duration of allergen exposure. In lungs of ADAM28-/- mice exposed to allergens, the proportion of Th2 cells among CD 4 + cells and the number of B cells were decreased. Bronchial responsiveness was lower in ADAM28-/- mice exposed to allergens and similar to the responsiveness of sham-challenged mice. Similarly, features of airway remodelling (collagen deposition, smooth muscle hyperplasia, mucous hyperplasia) were significantly less developed in OVA-exposed ADAM28-/- animals in sharp contrasts to ADAM28+/+. In addition, we report the first evidence of ADAM28 RNA expression by lung fibroblasts and we unveil a decreased capacity of lung fibroblasts extracted from OVA-exposed ADAM28-/- mice to proliferate as compared to those extracted from OVA-exposed ADAM28+/+ suggesting a direct contribution of this enzyme to the modulation of airway remodelling. Conclusion: These results suggest that ADAM28 might be a key contributor to the pathophysiology of asthma.

Using a randomised controlled trial to test the effectiveness of social norms feedback to reduce antibiotic prescribing without increasing inequities.

AIMS: Antibiotic overprescription is a key driver of antimicrobial resistance, and rates of community dispensing of antibiotics in New Zealand are high compared to other developed countries. We aimed to test whether a social-norm-based intervention successful elsewhere would have an effect on GPs with high prescribing rates of antibiotics. We also aimed to assess the effects on prescribing for Maori and Pacific patients. METHODS: A randomised controlled trial (n=1,214) tested the effects of a letter mailed to high-prescribing GPs that presented their prescribing data in comparison to their peers. RESULTS: In September-December 2019, after the letters were mailed, the antibiotic prescribing rate in the control arm was 178.8 patients prescribed antibiotics per 1,000 patients prescribed any medicine, and in the intervention arm it was 162.3, a relative difference of 9.2% (p<0.001). GPs in the intervention arm were responsible for an average of 173.5 prescriptions, versus an average of 186.8 prescriptions for GPs in the control arm, a relative difference of 13.3 or 7.1% (p<0.01). Exploratory analyses showed the intervention reduced prescribing to Maori and Pacific patients among historically high prescribing GPs but had no statistically significant impact on low prescribers. CONCLUSIONS: A targeted intervention using social norms reduced prescribing of antibiotics by high-prescribing GPs. Such an approach may be promising to address inequities in access to and use of antibiotics by Maori and Pacific peoples, historically underserved by prescribers, but further investigation is needed.

Self-antigen MASH2 combined with the AS15 immunostimulant induces tumor protection in colorectal cancer mouse models.

Human achaete scute homolog 2 (HASH2) and its murine ortholog MASH2 are potential targets for colorectal cancer immunotherapy. We assessed immunogenicity and antitumor potential of recombinant MASH2 protein combined with AS15 immunostimulant (recMASH2+AS15) in CB6F1 and Apc+/Min-FCCC mice. CB6F1 mice received 4 injections of recMASH2+AS15 or AS15 alone before challenge with TC1-MASH2 tumor cells (Tumor Challenge). Apc+/Min-FCCC mice received 9 injections of recMASH2+AS15 or vehicle (phosphate buffer saline [PBS] or AS15 alone), before (two independent Prophylactic Studies) or after (Immunotherapy) colon adenomas were detectable by colonoscopy. CB6F1 mice immunized with recMASH2+AS15 had a significantly smaller mean tumor size and improved survival rate compared to controls (104 mm2 vs. 197 mm2 [p = 0.009] and 67% vs. 7% [p = 0.001], respectively). In Prophylactic Study 1, the mean number of colon adenomas was significantly lower in Apc+/Min-FCCC mice receiving recMASH2+AS15 compared to PBS (1.8 [95% confidence interval 1.0-3.3] vs. 5.2 [3.7-7.4], p = 0.003). Fewer microadenomas were observed in recMASH2+AS15 groups compared to PBS in both Prophylactic Studies (Study 1: mean 0.4 [0.2-1.0] vs. 1.5 [0.9-2.4], p = 0.009; Study 2: 0.4 [0.2-0.6] vs. 1.1 [0.8-1.5], p = 0.001). In the Immunotherapy Study, fewer colon adenomas tended to be observed in recMASH2+AS15-treated mice (4.1 [2.9-6.0]) compared to controls (AS15 4.7 [3.3-6.6]; PBS 4.9 [3.5-6.9]; no significant difference). recMASH2+AS15 induced MASH2-specific antibody and CD4+ responses in both mouse models. recMASH2+AS15 partially protected mice against MASH2-expressing tumors and reduced spontaneous colorectal adenomas in Apc+/Min-FCCC mice, indicating that MASH2/HASH2 antigens are targets for colorectal cancer immunotherapy.

ADAM10 mediates malignant pleural mesothelioma invasiveness.

Malignant pleural mesothelioma (MPM) is an aggressive cancer with limited therapeutic options and treatment efficiency. Even if the latency period between asbestos exposure, the main risk factor, and mesothelioma development is very long, the local invasion of mesothelioma is very rapid leading to a mean survival of one year after diagnosis. ADAM10 (A Disintegrin And Metalloprotease) sheddase targets membrane-bound substrates and its overexpression is associated with progression in several cancers. However, nothing is known about ADAM10 implication in MPM. In this study, we demonstrated higher ADAM10 expression levels in human MPM as compared to control pleural samples and in human MPM cell line. This ADAM10 overexpression was also observed in murine MPM samples. Two mouse mesothelioma cell lines were used in this study including one primary cell line obtained by repeated asbestos fibre injections. We show, in vitro, that ADAM10 targeting through shRNA and pharmacological (GI254023X) approaches reduced drastically mesothelioma cell migration and invasion, as well as for human mesothelioma cells treated with siRNA targeting ADAM10. Moreover, ADAM10 downregulation in murine mesothelioma cells significantly impairs MPM progression in vivo after intrapleural cell injection. We also demonstrate that ADAM10 sheddase downregulation decreases the production of a soluble N-cadherin fragment through membrane N-cadherin, which stimulated mesothelioma cell migration. Taken together, we demonstrate that ADAM10 is overexpressed in MPM and takes part to MPM progression through the generation of N-cadherin fragment that stimulates mesothelioma cell migration. ADAM10 inhibition is worth considering as a therapeutic perspective in mesothelioma context.

Increased Frataxin Expression Induced in Friedreich Ataxia Cells by Platinum TALE-VP64s or Platinum TALE-SunTag.

Frataxin gene (FXN) expression is reduced in Friedreich's ataxia patients due to an increase in the number of GAA trinucleotides in intron 1. The frataxin protein, encoded by that gene, plays an important role in mitochondria's iron metabolism. Platinum TALE (plTALE) proteins targeting the regulatory region of the FXN gene, fused with a transcriptional activator (TA) such as VP64 or P300, were used to increase the expression of that gene. Many effectors, plTALEVP64, plTALEp300, and plTALESunTag, targeting 14 sequences of the FXN gene promoter or intron 1 were produced. This permitted selection of 3 plTALEVP64s and 2 plTALESunTag that increased FXN gene expression by up to 19-fold in different Friedreich ataxia (FRDA) primary fibroblasts. Adeno-associated viruses were used to deliver the best effectors to the YG8R mouse model to validate their efficiencies in vivo. Our results showed that these selected plTALEVP64s or plTALESunTag induced transcriptional activity of the endogenous FXN gene as well as expression of the frataxin protein in YG8R mouse heart by 10-fold and in skeletal muscles by up to 35-fold. The aconitase activity was positively modulated by the frataxin level in mitochondria, and it was, thus, increased in vitro and in vivo by the increased frataxin expression.

Inappropriate prescribing of antibiotics following discharge after major surgery: an area for improvement.

AIM: This study aims to determine the indications for antibiotic use in patients discharged following major surgery at Auckland City Hospital (ACH); to determine if the indications were appropriate and to identify opportunities where antimicrobial stewardship interventions would be beneficial. METHODS: This was a retrospective study of adult patients who were dispensed an antibiotic within the first two days of discharge after major surgery at ACH between 1 January 2013 and 31 December 2013. The indication for antibiotic use was determined and subsequently classified as either 'appropriate', 'not assessable' or 'inappropriate'. RESULTS: Among the 378 patients analysed, an indication for antibiotic use was not documented in 52 patients (13.8%). Antibiotics were prescribed for an established infection in 172 patients (45.5%), as empiric therapy in 100 patients (26.4%), and as prolonged surgical antimicrobial prophylaxis in 41 patients (10.8%). Overall, nearly half of the antibiotic courses dispensed (48.7%) were either 'inappropriate' or the indication was 'not assessable'. CONCLUSIONS: This study demonstrates that a significant proportion of antibiotics prescribed in patients discharged following surgery are inappropriate and there is need for enhanced antimicrobial stewardship in this area.

Medical practice variation: public reporting a first necessary step to spark change.

From previous work, we know that medical practice varies widely, and that unwarranted variation signals low value for patients and society. We also know that public reporting helps to create awareness of the need for quality improvement. Despite the availability of rich data, most Western countries have no routine surveillance of the geographic distribution of utilization, costs, and outcomes of healthcare, including trends in variation over time. This paper highlights the role of transparent public reporting as a necessary first step to spark change and reduce unwarranted variation. Two recent examples of public reporting are presented to illustrate possible ways to reduce unwarranted variation and improve care. We conclude by introducing the Value Improvement Cycle, which underscores that reporting is only a necessary first step, and suggests a path toward developing a multi-stakeholder approach to change.

Microenvironment-derived ADAM28 prevents cancer dissemination.

Previous studies have linked cancer cell-associated ADAM28 expression with tumor progression and metastatic dissemination. However, the role of host-derived ADAM28 in cancer dissemination processes remains unclear. Genetically engineered-mice fully deficient for ADAM28 unexpectedly display increased lung colonization by pulmonary, melanoma or breast tumor cells. In experimental tumor cell dissemination models, host ADAM28 deficiency is further associated with a decreased lung infiltration by CD8+ T lymphocytes. Notably, naive ADAM28-deficient mice already display a drastic reduction of CD8+ T cells in spleen which is further observed in lungs. Interestingly, ex vivo CD8+ T cell characterization revealed that ADAM28-deficiency does not impact proliferation, migration nor activation of CD8+ T cells. Our data highlight a functional role of ADAM28 in T cell mobilization and point to an unexpected protective role for host ADAM28 against metastasis.

Neutrophil-Derived Interleukin 16 in Premetastatic Lungs Promotes Breast Tumor Cell Seeding.

The premetastatic niche in distant organs prior to metastatic cell arrival emerged as an important step in the metastatic cascade. However, molecular mechanisms underlying this process are still poorly understood. In particular, whether neutrophil recruitment at a premetastatic stage promotes or inhibits metastatic cell seeding has to be clarified. We aimed at unraveling how neutrophil infiltration in lung parenchyma induced by the distant primary tumor influences the establishment of lung metastasis. Elevated neutrophil counts and IL-16 levels were found in premetastatic lungs in a syngenic mouse model using 4T1 tumor cells. 4T1 cell-derived soluble factors stimulated IL-16 secretion by neutrophils. The functional contribution of IL-16 is supported by metastasis burden reduction in lungs observed on instillation of an IL-16 neutralizing antibody. Moreover, IL-16 promotes in vitro 4T1 cell adhesiveness, invasiveness, and migration. In conclusion, at a premetastatic stage, neutrophil-derived IL-16 favors tumor cell engraftment in lung parenchyma.