Mucosal associated invariant T (MAIT) cells are abundant unconventional T cells that recognize microbe-derived riboflavin metabolites presented by MR1. Upon recognition, they become activated, produce proinflammatory cytokines, chemokines and cytotoxic molecules. MAIT cells are also activated by cytokines independently of T cell receptor (TCR) engagement, however these two signals can also act in concert to finetune MAIT cell functions. Additionally, multiple other co-stimulatory signals have also been reported that can boost MAIT cell effector responses to TCR or cytokine stimulation. However, a comprehensive study exploring the role of surface bound TNF receptor superfamily (TNFRSF) molecule 4-1BB, well known for its co-stimulatory function during conventional T cell activation, is lacking in the context of MAIT cells. In this study, we show that 4-1BB is the earliest and most highly expressed TNFRSF co-stimulatory molecule on MAIT cells upon activation by Escherichia coli, with expression seen as early as six hours where it was predominantly MR1 mediated. 4-1BB expression on MAIT cells following late activation was due to both TCR signaling and cytokine signaling. We found marked differences in MAIT cell activation and cytokine expression between 4-1BB+ and 4-1BB- MAIT cells suggesting 4-1BB expression on MAIT cells is associated with functional superiority. By blocking 4-1BB signaling or co-culturing with a 4-1BBL overexpressing cell line we demonstrated an important role of co-stimulation via 4-1BB in MAIT cells during activation. Expression and signaling via 4-1BB also enhanced T-bet and Blimp1 expression. In summary, our study confirms a role for 4-1BB signaling during MAIT cell activation.

Vaccines capable of eliciting broadly neutralizing antibodies (bnAbs) are a major goal for pandemic preparedness. A challenge across vaccine fields is how to deliberately recruit the rare B cell clones that recognize conserved epitopes shared across diverse viral variants. BnAbs have been known to frequently emerge through extensive somatic hypermutation during affinity maturation, here we describe an alternative mechanism for bnAb selection. We designed an mRNA vaccine in which two antigenically distinct (severe acute respiratory syndrome coronavirus 2) SARS-CoV-2 variant’s (Omicron and Delta; O-Δ) receptor binding domains (RBDs) are physically fused on a single polypeptide. This design is predicted to favor B cell antigen receptors capable of engaging conserved epitopes on both RBDs with enhanced avidity. A matched nondivergent tandem RBD (Delta-Delta; Δ-Δ) served as a control. In mice, immunization elicited potent antibody responses and increased the frequency of cross-reactive B cells, recognizing Delta, Omicron, and the 2002 pandemic strain SARS-CoV RBDs. Using multicolor RBD tetramers and single-cell B cell receptor sequencing, we show that breadth arises via two distinct pathways. The divergent vaccine preferentially enriches clonally distinct cross-reactive B cells (not present within non-cross-reactive B cell pools) with low levels of somatic hypermutation, consistent with selection of germline-biased precursors. In contrast, the matched control vaccine yields cross-reactivity primarily within existing clonal lineages (clonal overlap between cross-reactive and non-cross-reactive cells) and at higher mutational burdens, consistent with affinity-maturation-driven acquisition of breadth. This work establishes a simple, modular antigen-design principle in which juxtaposing appropriately divergent antigens on a single scaffold promotes the enrichment of bnAb-prone B cells.

Mucosal-associated invariant T (MAIT) cells are unconventional cytotoxic T cells restricted by MHC class 1 related molecule, MR1. They are activated through their T cell receptor (TCR) by derivatives from microbial riboflavin synthesis or independently of TCR signalling via IL-12 and IL-18. Upon activation, MAIT cells upregulate cytotoxic molecules granzyme B and perforin and lyse bacterially-infected cells. While cytokines act as co-stimulatory molecules that enhance MAIT cell activation, their specific role in regulating MAIT cell cytotoxicity remains unresolved. We show that the cytokine IL-21 enhances expression of granzyme B and perforin on TCR or IL-12/IL-18-activated MAIT cells but has a limited effect on MAIT cell cytokine production. Using a flow cytometry-based cytotoxic assay, we show priming MAIT cells with IL-21 enhances their ability to kill 5-OP-RU-treated B cell lines. We demonstrate a previously unexplored co-stimulatory role for IL-21 that selectively augments the cytotoxic potential of MAIT cells.

Introduction:Tuberculosis (TB) remains a major public health concern in Fiji, but genomic data on the circulating Mycobacterium tuberculosis complex (MTBC) are limited. Methods:We analysed 65 MTBC isolates collected during 2019-2022 using whole-genome sequencing to characterize lineage distribution, drug resistance, and transmission patterns. Results:Of the isolates, 62 (95.4%) were Mycobacterium tuberculosis and 3 (4.6%) were Mycobacterium bovis. Lineage 4 was the most common (29/62, 46.8%). Genomic analysis identified 12 transmission clusters, with epidemiological links involving households, schools, and neighbouring communities. Most MTBC isolates (57/65, 87.7%) were susceptible to first-line anti-TB drugs; however, 8 (12.3%) carried resistance-associated mutations in katG, rpoB, rrs, or pncA. Treatment outcomes indicated that 20 (30.8%) patients were lost to follow-up. Discussion:Detection of M. bovis suggests possible zoonotic transmission and highlights limitations of routine diagnostics. These findings indicate diverse MTBC lineages and localized transmission networks, supporting integration of genomic surveillance into TB control efforts in Fiji.

Introduction:Understanding antimicrobial susceptibility patterns is essential for guiding clinical management and informing surveillance strategies. This study aimed to analyse antimicrobial susceptibility trends of WHO-designated critical Gram-negative pathogens in Fijian hospitals. Methods:We conducted a retrospective study of antimicrobial susceptibility among Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae isolated from three hospitals in Fiji from 1 January 2016 to 31 December 2021. Data were stratified by hospital, hospital setting, and specimen type. Only the first isolate per patient was included. Chi-square tests and linear regression were used to assess group differences and temporal trends. Results:A total of 44 524 isolates were analysed: K. pneumoniae 17 016 (38.2%), E. coli 14 935 (33.5%), P. aeruginosa 6632 (14.9%), and A. baumannii 5941 (13.3%). Specimens included blood 4612 (10.4%), urine 13 369 (30.0%), and other types 26 543 (59.6%). Meropenem susceptibility declined significantly in A. baumannii (60.4% to 40.8%, P = 0.0004) and P. aeruginosa (100% to 40.8%, P = 0.005). Ceftriaxone susceptibility was low in E. coli (49.8%) and K. pneumoniae (32.7%). Meropenem susceptibility remained high in K. pneumoniae (96.6% in 2021) and E. coli (>80%). ESBL production was identified in 18.2% of E. coli and 37.6% of K. pneumoniae. Conclusions:These findings highlight substantial AMR challenges in Fijian hospitals, including declining carbapenem susceptibility and high ceftriaxone resistance, underscoring the need for strengthened antimicrobial stewardship, infection control, and surveillance systems.

OBJECTIVES:Rickettsioses are frequent causes of treatable febrile illness in Southeast Asia, including Myanmar. Accurate estimates of the incidence of rickettsioses are needed to inform investments in disease prevention and control. We sought to estimate the incidence of rickettsioses among adults and adolescents by combining sentinel hospital surveillance with a healthcare utilisation survey in Yangon, Myanmar. METHODS:We conducted a household-based healthcare utilisation survey in the Yangon Region from 12 March through 5 April 2018. Multipliers derived from this survey were then applied to scrub typhus, murine typhus, and spotted fever group rickettsioses infections identified from a study of adolescent and adult community-onset febrile illness done from 5 October 2015 through 4 October 2016 at Yangon General Hospital to estimate disease incidence. Acute serum was collected at enrolment and convalescent serum 14-30 days after enrolment. Confirmed acute scrub typhus, murine typhus, and spotted fever group infections were diagnosed by a ≥ 4-fold rise between acute and convalescent immunofluorescent antibody test titre to Orientia tsutsugamushi pooled Karp, Kato, and Gilliam antigens; Rickettsia typhi Wilmington strain; and Rickettsia honei and Rickettsia conorii antigens, respectively. RESULTS:After applying multipliers, we estimated the overall annual incidence of acute scrub typhus among adolescents and adults in the Yangon Region at 211 cases per 100,000 persons, and the overall estimate of acute murine typhus among adults and adolescents was 44 cases per 100,000 persons per year for 2015-2016. There were no confirmed spotted fever group infections. CONCLUSIONS:We provide the first estimates of scrub typhus and murine typhus community incidence in Myanmar. Similar research in children and from other parts of Myanmar, as well as studies of illness duration, complications, and deaths, is needed to estimate the disease burden.

OBJECTIVES:To inform patient management and disease prevention, we sought to estimate the prevalence of, and identify risk factors for, scrub typhus, murine typhus, and spotted fever group rickettsioses (SFGR) among febrile patients presenting to hospital in Myanmar. METHODS:We recruited patients ≥12 years old with fever ≥38°C among those seeking care at Yangon General Hospital from 5 October 2015 through 4 October 2016. Standardised clinical and risk factor assessments were conducted. Confirmed scrub typhus, murine typhus, and SFGR infections were defined as a positive polymerase chain reaction or ≥4-fold rise in immunofluorescence assay antibody titre to Orientia tsutsugamushi, Rickettsia typhi or Rickettsia honei or Rickettsia conorii, respectively. Probable infection was defined as IgM titre ≥1:400 to O. tsutsugamushi, an IgM titre of ≥1:800 or IgG ≥1:1600 to R. typhi or an IgG titre of ≥1:200 to R. honeii or R. conorii. Univariate and multivariable logistic regression was used to identify associations. RESULTS:Among 944 participants, the median (range) age was 37 (12-94) years, 444 (47.0%) were female, and 704 (74.6%) resided in rural areas. Among participants, 63 (6.7%) had confirmed or probable scrub typhus and 15 (1.6%) had confirmed or probable murine typhus. No SFGR infections were identified. The odds of confirmed or probable scrub typhus were lower among females than males (adjusted odds ratio [aOR] 0.5, p = 0.014), lower among those earning >300,000 Kyat per month compared with those earning less than 100,000 Kyat per month (aOR 0.28, p = 0.039), and higher among agricultural workers compared with others (aOR 2.9, p = 0.004). CONCLUSION:Scrub typhus was common among patients presenting with fever in Yangon, murine typhus was uncommon, and SFGR was not found. Empiric treatment of severe febrile illness should include an antimicrobial with activity against rickettsial diseases. Public health campaigns targeting agricultural workers are recommended.

Staphylococcus aureus is a major zoonotic bacterial pathogen that causes a broad spectrum of human and animal diseases, including skin infections, sepsis, endocarditis, and bovine mastitis. In the geographically isolated setting of New Zealand, the population structure of S. aureus exhibits a distinct genomic profile. Globally, bovine S. aureus isolates are primarily associated with sequence types (STs), ST97 and ST151, whereas in New Zealand, ST1 predominates, accounting for approximately 70% of bovine isolates. ST1 is also a clinically significant sequence type in humans. This study employed a comparative One Health approach to investigate genetic differences in 520 S. aureus ST1 isolated from bovine milk and human clinical samples. We aimed to explore genomic features associated with persistence and diversification across hosts, focusing on antimicrobial resistance (AMR), virulence, and mobile genetic elements. Comparative genomics revealed that human isolates carried a significantly higher burden of AMR genes, consistent with clinical selective pressure. In contrast, 83% of bovine isolates harbored a prophage (φSabovST1) similar to S. aureus prophage φSaov3. This prophage encodes bovine-adapted leukocidins (LukMF'), supporting host-specific adaptation. Phylogenetic analysis revealed long branches, suggesting insufficient sampling, highlighting the need for broader genomic surveillance to resolve evolutionary relationships and transmission dynamics of S. aureus ST1 in New Zealand. These findings highlight the complex history of host interactions, historical transmission events, and ongoing bacterial adaptation. Expanding sampling efforts across human, animal, and environmental reservoirs will provide deeper insights into strain diversity, elucidate transmission pathways, and inform strategies to mitigate zoonotic risks.IMPORTANCEThis study presents a comprehensive genomic analysis of S. aureus ST1, a lineage that is unusually dominant in both bovine and human populations in New Zealand. Leveraging New Zealand's geographical isolation, we provide critical insights into the persistence, diversification, and adaptation of S. aureus, offering valuable knowledge to advance disease prevention in both public and veterinary health and strengthening global biosecurity. The development of the first bovine ST1 reference genome serves as a valuable resource for future research, while the identification of a novel prophage (φSabovST1) carrying bovine-specific leukocidins underscores the role of mobile genetic elements in host specificity and virulence. Human isolates exhibited a higher prevalence of antimicrobial resistance genes. Phylogenetic analysis further revealed two main circulating clades of ST1 with interspersed host origins, highlighting the critical need for integrated One Health approaches to more effectively monitor and manage zoonotic pathogens across agricultural and public health systems.

Background Certain micronutrient levels have been associated with the risk of developing TB disease. We explored the possible association of selected at-risk micronutrient levels with the development of Mycobacterium tuberculosis (M.tb) infection.Methods This cohort study in Bandung, Indonesia, followed Interferon Gamma Release Assay (IGRA) negative TB case contacts with a repeat IGRA test at 3 mo. At baseline, blood was analysed for haemoglobin, 25-hydroxyvitamin D, retinol-binding protein, C-reactive protein, alpha-1-acid glycoprotein, serum transferrin receptor (sTfR), ferritin, zinc and selenium. Total body iron was calculated using ferritin and sTfR status. Associations between case contact micronutrient concentration and IGRA conversion were estimated using Poisson regression.Results Of 430 contacts, 115 (27%) underwent IGRA conversion. Ferritin concentration (adjusted for inflammation) was positively associated with risk of IGRA conversion (incidence rate ratio [IRR] for ferritin=1.17; 95% CI 1.01 to 1.35; p=0.03), but other select micronutrients were not. This association held for ferritin in the final multivariable model (IRR=1.27; 95% CI 1.09 to 1.47; p=0.002).Conclusions The risk of developing M.tb infection, as defined by IGRA conversion, is associated with increasing ferritin. Interventions in TB case contacts to temporarily reduce iron levels, including considering withholding any iron supplementation, may be worthy of evaluation.

AbstractSome individuals, even when heavily exposed to an infectious tuberculosis patient, do not develop a specific T-cell response as measured by interferon-gamma release assay (IGRA). This could be explained by an IFN-γ-independent adaptive immune response, or an effective innate host response clearing Mycobacterium tuberculosis (Mtb) without adaptive immunity. In heavily exposed Indonesian tuberculosis household contacts (n = 1347), a persistently IGRA negative status was associated with presence of a BCG scar, and - especially among those with a BCG scar - with altered innate immune cells dynamics, higher heterologous (Escherichia coli-induced) proinflammatory cytokine production, and higher inflammatory proteins in the IGRA mitogen tube. Neither circulating concentrations of Mtb-specific antibodies nor functional antibody activity associated with IGRA status at baseline or follow-up. In a cohort of adults in a low tuberculosis incidence setting, BCG vaccination induced heterologous innate cytokine production, but only marginally affected Mtb-specific antibody profiles. Our findings suggest that a more efficient host innate immune response, rather than a humoral response, mediates early clearance of Mtb. The protective effect of BCG vaccination against Mtb infection may be linked to innate immune priming, also termed ‘trained immunity’.

The successive dominance of SARS-CoV-2 omicron sublineages presents challenges for vaccination strategies with respect to the antigenic content of boosters. New Zealand's COVID-19 elimination strategy (2020-2021) ensured the major vaccination campaign (Pfizer-BioNTech BNT162b2) was completed pre-omicron in an infection-naive population, providing a unique setting to explore the impact of omicron infection waves on vaccine responses. This study compared neutralising antibodies (NAb) to eight SARS-CoV-2 omicron sublineages 28-days and 11-months after a third dose. Participants (n = 219) were classified by antigen exposure in the intervening 10 months including additional vaccinations and/or infections. Both vaccination and infection boosted NAb levels to all sublineages. Antigenic maps showed infection had a major impact on NAb breadth, despite all participants being vaccinated with an ancestral-based vaccine. While vaccination remains an important tool to boost immunity, the breadth of NAbs observed suggest that attempts to match booster specificity with current circulating variants may not always be necessary.

Vaginitis presentations are common, but traditional diagnostic methods are imperfect. Molecular methods for bacterial vaginosis (BV) and vulvovaginal candidiasis (CV) are increasingly available but not commonly utilized in Aotearoa New Zealand. We evaluated the Hologic Aptima BV and CV/Trichomonas vaginalis (TV) assays against our current methods (Gram stain, yeast culture, and Hologic Aptima TV assay) and performed a retrospective BV clinical audit. The BV Aptima assay performed well with high sensitivity (97.5%) and specificity (96.3%) when the indeterminate BV category was excluded. BV indeterminate samples were almost evenly split between positive and negative results when tested on the Aptima BV assay. BV Gram stain interpretation was error prone, with 20% of samples discordant on duplicate examination. Although the Aptima CV assay was highly sensitive, it lacked specificity compared with Gram stain (83.5%) but was similar to culture (91.2%). Our BV clinical audit showed that patients with a BV indeterminate result were less likely to be treated for BV than those with a positive result, meaning more women may be treated for BV if this assay were implemented. Overall, implementation may improve laboratory workflow and consistency of reporting, but cost may be a barrier. The clinical impact of changing methods needs to be considered.IMPORTANCEIn this paper, we evaluate the performance of the Aptima molecular assays against current Gram stain and culture methods, as well as a clinical audit to determine the potential clinical impact of implementation. Although molecular methods are increasingly used in other countries, New Zealand has not yet adopted this approach. Importantly, we found Gram stain for bacterial vaginosis (BV) to be error prone, with 20% of Gram stain results discordant on repeat examination. We show the potential for molecular methods to increase BV diagnoses and improve reproducibility and consistency of reporting which, according to our clinical audit results, would lead to more women being treated for this dysbiosis condition overall.

Background Carbapenem resistant organisms (CROs) such as Acinetobacter baumannii (CR Ab ), Pseudomonas aeruginosa (CR Pa ), Escherichia coli (CR Ec ), and Klebsiella pneumoniae (CR Kp ) have been identi fi ed by the World Health Organization (WHO) as global priority pathogens. The dissemination of these pathogens and clonal outbreaks within healthcare facilities are of serious concern, particularly in regions with limited resources. In Fiji, where healthcare services are primarily provided by public hospitals, understanding the extent and nature of this problem is essential for the development of effective patient management, prevention interventions and control strategies. Methods CROs isolated from 211 (77.3%) non -sterile (urinary catheters, urine, sputum, wound swab, and endotracheal tube) and 62 (22.7%) normally sterile (blood, cerebrospinal fl uid, intravascular catheter, and aspirates) body sites of 272 patients treated at the three major hospitals in Fiji, the Colonial War Memorial Hospital (CWMH), Lautoka Hospital (LTKH), and Labasa Hospital (LBSH), and outer peripheral health centres around Fiji, were analysed. Clinical and demographic patient data such as age, sex, admission diagnosis, admission and discharge dates, patient outcomes, date of death, start and end date of meropenem and colistin treatment were reviewed. These CRO isolates comprised A. baumannii , P. aeruginosa , E. coli , and K. pneumoniae , that were prospectively collected at the microbiology laboratory of CWMH and LBSH from January 2020 through August 2021 and at the LTKH from January 2020 to December 2021. In addition, 10 retrospectively stored CR Pa isolates collected from patients at the CWMH from January through December 2019, were also included in the study. All isolates were characterised using mass spectrometry, antimicrobial susceptibility testing, and whole genome sequencing. Phylogenetic relationships among the CROs were assessed through core genome single nucleotide polymorphism (SNP) analysis. The CR Ab isolates were also compared to the CR Ab isolates from CWMH isolated in 2016/2017 and 2019, along with CR Ab isolates obtained from Fijian patients admitted to New Zealand hospitals in 2020 and 2021 from our retrospective study. Findings Of 272 patients, 140 (51.5%) were male, the median (range) age of patients was 45 (<1-89) years, 161 (59.2%) were I-Taukei, 104 (38.2%) Fijians of Indian descent, and 7 (2.6%) were from other ethnic backgrounds. 234 (86.0%) of these 272 patients, had their first positive CRO sample collected >= 72 h following admission and the remaining 38 (14.0%) were isolated within 72 h following admission. Of the 273 CROs, 146 (53.5%) were collected at the CWMH, 66 (24.2%) LTKH, and 61 (22.3%) LBSH, while 62 (22.7%) were isolated from normally sterile sites and 211 (77.3%) from sites that are not sterile. Of 273 isolates, 131 (48.0%) were CRAb, 90 (33.0%) CRPa, 46 (16.8%) CREc, and 6 (2.2%) CRKp. Of 131 CRAb, 108 (82.4%) were ST2, with three distinct clones, all encoding bla(OXA-23) and bla(OXA)(-)(66), while clone 3 also encoded bla(NDM-1); bla(OXA-23) was associated with two copies of ISAba1 insertion element, forming the composite transposon Tn2006. The first two CRAb ST2 clones were genetically linked to those isolated at CMWH 2016 through 2019, while the third was genetically linked to isolates from Fijian patients admitted to New Zealand hospitals in 2020 and 2021. Of CRPa, 65 (72. 2%) were ST773 and carried beta-lactamase genes bla(NDM-1), bla(OXA-50), and bla(OXA-395). Of 10 retrospective CRPa isolates, all belonged to CRPa ST773 and carried bla(NDM-1), bla(OXA-50), and bla(OXA-395). Of 46 CREc, 44 (95.7%) were ST410 and encoded bla(NDM-7) on an IncX3 plasmid. Of 6 CRKp, 4 (66.7%) were ST16 and carried bla(NDM-5) on an IncX3 plasmid. Other sequence types of CRPa (ST9, ST357, ST654, ST664), CRAb (ST25, ST374, ST499), CREc (ST167), and CRKp (ST45, ST336) were also detected. Of those receiving meropenem treatment in the prospective study, 30 (57.7%) received it inappropriately. Of 272 patients, 65 (23.9%) died within the 30 days after first positive CRO isolation. Interpretation We identified nosocomial transmission of distinct clones of CRAb ST2, CRPa ST773, CREc ST410, and CRKp ST16 within and between the three major hospitals in Fiji. Moreover, community onset infections associated with CRPa, CREc, and CRAb were also detected. Of note, cross-border transmission of CRAb ST2 clone 3 strain between Fiji and New Zealand was also detected. These clones encoded an array of carbapenem resistance genes associated with mobile genetic elements, including plasmids, transposons, and integrative and conjugative elements, signifying their potential for increased mobility, further acquisition of resistance genes, and spread. Inappropriate use of meropenem was common. Of note, the majority of patients who died had acquired CRO during their hospital stay. These findings highlight the need for stringent IPC strategies focusing on catheter and ventilator management, meticulous wound care, rigorous sepsis control, consistent hand hygiene, effective use of disinfectants, and thorough sanitisation of both hospital environments and medical equipment in the three major hospitals in Fiji. Additionally, diligent surveillance of AMR and robust antimicrobial stewardship are crucial for effectively managing nosocomial infections.

Introduction There are multiple ongoing outbreaks of carbapenem resistant Acinetobacter baumannii (CRAb) infection in Fiji's hospitals. CRAb is able to colonize and persist on various hospital surfaces for extended periods. We conducted a study to understand the extent of hospital environmental contamination and phylogenetic links with clinical isolates. Methods Swabs were collected from high-touch surfaces at Colonial War Memorial Hospital (CWMH) September 2021 and December 2022; Lautoka Hospital (LTKH) August 2022; and Labasa Hospital (LBSH) November 2022. All bacterial isolates were identified, and antimicrobial susceptibility testing (AST) performed; isolates resistant to carbapenems and producing a carbapenemase underwent whole genome sequencing. Comparison was made to clinical isolates obtained from CWMH in 2016-2017 and 2019-2021 and from LTKH and LBSH from 2020-2021. Results From the 180 environmental samples collected, ten (5.6%) CRAb were isolated; no other carbapenem-resistant gram-negative organisms were isolated. Seven (70%) of the CRAb were isolated from CWMH and three (30%) from LTKH; no CRAb were isolated from LBSH. Of the seven CWMH CRAb, two were sequence type 2 (ST2), three ST25, and two ST499. All LTKH isolates were ST499. The two environmental CRAb ST2 isolates were closely genetically linked to isolates obtained from patients in CWMH, LTKH, and LBSH 2020-2021. Similarly, the three environmental CRAb ST25 isolates were closely genetically linked to isolates obtained from patients admitted to CWMH in 2019-2021 and LBSH in 2020. The environmental CRAb ST499 isolates represented two distinct clones, with clone 1 comprising two genetically identical isolates from CWMH and clone 2 the three isolates from LTKH. Although no genetic linkages were observed when comparing environmental ST499 isolates to those from CWMH patients in 2020-2021, both clone 1 isolates were genetically identical to an isolate obtained from a patient admitted during the sampling period. Conclusion Our study highlights the contamination of high-touch surfaces within Fiji hospitals with CRAb, suggesting that these may serve as important sources for CRAb. Phylogenetic linkages to CRAb isolated from patients since 2019 underscores the persistence of this resistant pathogen in hospital settings and the ongoing risk for hospital-acquired infections.

EDITORIAL article Front. Immunol., 06 September 2023Sec. T Cell Biology Volume 14 - 2023 | https://doi.org/10.3389/fimmu.2023.1281881

Emerging SARS-CoV-2 variants pose a threat to human health worldwide. SARS-CoV-2 receptor binding domain (RBD)-based vaccines are suitable candidates for booster vaccines, eliciting a focused antibody response enriched for virus neutralizing activity. Although RBD proteins are manufactured easily, and have excellent stability and safety properties, they are poorly immunogenic compared to the full-length spike protein. We have overcome this limitation by engineering a sub-unit vaccine composed of an RBD tandem dimer fused to the N-terminal domain (NTD) of the spike protein. We found that inclusion of the NTD (1) improved the magnitude and breadth of the T cell and anti-RBD response, and (2) enhanced T follicular helper cell and memory B cell generation, antibody potency, and cross-reactive neutralization activity against multiple SARS-CoV-2 variants, including B.1.1.529 (Omicron BA.1). In summary, our uniquely engineered RBD-NTD-subunit protein vaccine provides a promising booster vaccination strategy capable of protecting against known SARS-CoV-2 variants of concern.

The ability of a third dose of the Pfizer-BioNTech BNT162b2 SARS-CoV-2 vaccine to stimulate immune responses against subvariants, including Omicron BA.1, has not been assessed in New Zealand populations. Unlike many overseas populations, New Zealanders were largely infection naïve at the time they were boosted. This adult cohort of 298 participants, oversampled for at-risk populations, was composed of 29% Māori and 28% Pacific peoples, with 40% of the population aged 55+. A significant proportion of the cohort was obese and presented with at least one comorbidity. Sera were collected 28 days and 6 months post second vaccination and 28 days post third vaccination. SARS-CoV-2 anti-S IgG titres and neutralising capacity using surrogate viral neutralisation assays against variants of concern, including Omicron BA.1, were investigated. The incidence of SARS-CoV-2 infection, within our cohort, prior to third vaccination was very low (<6%). This study found a third vaccine significantly increased the mean SARS-CoV-2 anti-S IgG titres, for every demographic subgroup, by a minimum of 1.5-fold compared to titres after two doses. Diabetic participants experienced a greater increase (∼4-fold) in antibody titres after their third vaccination, compared to non-diabetics (increase of ∼ 2-fold). This corrected for the deficiency in antibody titres within diabetic participants which was observed following two doses. A third dose also induced a neutralising response against Omicron variant BA.1, which was absent after two doses. This neutralising response improved regardless of age, BMI, ethnicity, or diabetes status. Participants aged ≥75 years consistently had the lowest SARS-CoV-2 anti-S IgG titres at each timepoint, however experienced the greatest improvement after three doses compared to younger participants. This study shows that in the absence of prior SARS-CoV-2 infection, a third Pfizer-BioNTech BNT162b2 vaccine enhances immunogenicity, including against Omicron BA.1, in a cohort representative of at-risk groups in the adult New Zealand population.

Background: In 2019, Aotearoa New Zealand (NZ) experienced its worst measles outbreak since 1997. Due to declining childhood vaccination rates since the beginning of the SARS-CoV-2 pandemic, NZ is at serious risk of another major measles outbreak. Our laboratory provides diagnostic services to NZ's Southern region. In 2019 the Southern region experienced the greatest number of cases outside of Auckland and Northland, however we did not have a validated measles PCR assay in our laboratory. Objectives: We sought to develop reverse transcription real-time polymerase chain reaction (RT-PCR) assays for measles on the Hologic Panther Fusion (R) System by utilising its open access function. Study Design: Previously published real-time RT-PCR assays were modified and optimised to detect wild-type measles virus (LDT-Mea), and the vaccine strain of measles virus (LDT-MeaVacA), on the Hologic Panther Fusion (R) System. The assays were clinically validated. Results: The LDT-Mea assay has a limit of detection (LoD) of 0.1 CCID50, while the LDT-MeaVacA assay is less sensitive with a LoD of 1 CCID50. Using 27 samples, the clinical sensitivity and specificity was 100% for both assays. Other common respiratory viruses were found not to cross-react with either the LDT-Mea or LDT-MeaVacA assays. Conclusion: We have successfully adapted and validated for diagnostic use on the Hologic Panther Fusion (R) System previously published assays to detect wild-type and vaccine strains of the measles virus. The imple-mentation of measles testing on this system will greatly improve the turn-around time for measles testing, and better support the measles public health response, for our region.