Type I interferons and MAVS signaling are necessary for tissue resident memory CD8+ T cell responses to RSV infection.

Respiratory syncytial virus (RSV) can cause bronchiolitis and viral pneumonia in young children and the elderly. Lack of vaccines and recurrence of RSV infection indicate the difficulty in eliciting protective memory immune responses. Tissue resident memory T cells (TRM) can confer protection from pathogen re-infection and, in human experimental RSV infection, the presence of lung CD8+ TRM cells correlates with a better outcome. However, the requirements for generating and maintaining lung TRM cells during RSV infection are not fully understood. Here, we use mouse models to assess the impact of innate immune response determinants in the generation and subsequent expansion of the TRM cell pool during RSV infection. We show that CD8+ TRM cells expand independently from systemic CD8+ T cells after RSV re-infection. Re-infected MAVS and MyD88/TRIF deficient mice, lacking key components involved in innate immune recognition of RSV and induction of type I interferons (IFN-α/ß), display impaired expansion of CD8+ TRM cells and reduction in antigen specific production of granzyme B and IFN-γ. IFN-α treatment of MAVS deficient mice during primary RSV infection restored TRM cell expansion upon re-challenge but failed to recover TRM cell functionality. Our data reveal how innate immunity, including the axis controlling type I IFN induction, instructs and regulates CD8+ TRM cell responses to RSV infection, suggesting possible mechanisms for therapeutic intervention.

COVID-19 Vaccine Safety in Pregnancy, A Nested Case-Control Study in Births From April 2021 to March 2022, England.

OBJECTIVE: Assessment of COVID-19 vaccine safety in pregnancy using population-based data. DESIGN: Matched case-control study nested in a retrospective cohort. SETTING: April 2021-March 2022, England. POPULATION OR SAMPLE: All pregnant individuals aged between 18 and 50 years with valid health records. METHODS: Individuals identified from the national Maternity Services Data Set (MSDS) had their records linked to hospital admission, national COVID-19 vaccine and COVID-19 testing databases. Matching included participant's age and estimated week of conception. We compared outcomes across multiple COVID-19 vaccine exposures using conditional multivariable logistic regression, adjusting for demographic and health characteristics. MAIN OUTCOME MEASURES: Adverse pregnancy, maternal and neonatal outcomes. RESULTS: 514 013 individuals were included. We found lower odds of giving birth to a baby who was low birthweight (aOR = 0.86, 95% CI: 0.79-0.93), preterm (aOR = 0.89, 95% CI: 0.85-0.92) or who had an Apgar score < 7 at 5 min of age (aOR = 0.89, 95% CI: 0.80-0.98) for individuals who received at least one dose of COVID-19 vaccine during pregnancy. The odds of admission to intensive care unit during pregnancy were lower in those vaccinated (aOR = 0.85, 95% CI: 0.76-0.95). There was no association between vaccination in pregnancy and stillbirth, neonatal death, perinatal death and maternal venous thromboembolism in pregnancy. CONCLUSIONS: COVID-19 vaccines are safe to use in pregnancy. Our findings generated important information to communicate to pregnant individuals and health professionals to support COVID-19 maternal vaccination programmes.

High-throughput transposon sequencing highlights the cell wall as an important barrier for osmotic stress in methicillin resistant Staphylococcus aureus and underlines a tailored response to different osmotic stressors.

Staphylococcus aureus is an opportunistic pathogen that can cause soft tissue infections but is also a frequent cause of foodborne illnesses. One contributing factor for this food association is its high salt tolerance allowing this organism to survive commonly used food preservation methods. How this resistance is mediated is poorly understood, particularly during long-term exposure. In this study, we used transposon sequencing (TN-seq) to understand how the responses to osmotic stressors differ. Our results revealed distinctly different long-term responses to NaCl, KCl and sucrose stresses. In addition, we identified the DUF2538 domain containing gene SAUSA300_0957 (gene 957) as essential under salt stress. Interestingly, a 957 mutant was less susceptible to oxacillin and showed increased peptidoglycan crosslinking. The salt sensitivity phenotype could be suppressed by amino acid substitutions in the transglycosylase domain of the penicillin-binding protein Pbp2, and these changes restored the peptidoglycan crosslinking to WT levels. These results indicate that increased crosslinking of the peptidoglycan polymer can be detrimental and highlight a critical role of the bacterial cell wall for osmotic stress resistance. This study will serve as a starting point for future research on osmotic stress response and help develop better strategies to tackle foodborne staphylococcal infections.

Population genetic structure and adaptation of malaria parasites on the edge of endemic distribution.

To determine whether the major human malaria parasite Plasmodium falciparum exhibits fragmented population structure or local adaptation at the northern limit of its African distribution where the dry Sahel zone meets the Sahara, samples were collected from diverse locations within Mauritania over a range of ~1000 km. Microsatellite genotypes were obtained for 203 clinical infection samples from eight locations, and Illumina paired-end sequences were obtained to yield high coverage genomewide single nucleotide polymorphism (SNP) data for 65 clinical infection samples from four locations. Most infections contained single parasite genotypes, reflecting low rates of transmission and superinfection locally, in contrast to the situation seen in population samples from countries further south. A minority of infections shared related or identical genotypes locally, indicating some repeated transmission of parasite clones without recombination. This caused some multilocus linkage disequilibrium and local divergence, but aside from the effect of repeated genotypes there was minimal differentiation between locations. Several chromosomal regions had elevated integrated haplotype scores (|iHS|) indicating recent selection, including those containing drug resistance genes. A genomewide FST scan comparison with previous sequence data from an area in West Africa with higher infection endemicity indicates that regional gene flow prevents genetic isolation, but revealed allele frequency differentiation at three drug resistance loci and an erythrocyte invasion ligand gene. Contrast of extended haplotype signatures revealed none to be unique to Mauritania. Discrete foci of infection on the edge of the Sahara are genetically highly connected to the wider continental parasite population, and local elimination would be difficult to achieve without very substantial reduction in malaria throughout the region.

The impact of COVID-19 vaccine spring boosters on COVID-19 hospital admissions in England 2022/23.

BACKGROUND: In the spring of 2022 and 2023 COVID-19 vaccine boosters were recommended for those aged ≥75 years in England as well as those in an immunosuppression risk group. The aim was to reduce severe COVID-19 disease in these groups. METHODS: The large difference in coverage between those above and below age 75 years was the basis for applying an age-discontinuity approach for measuring the impact of vaccination on COVID-19 hospitalisations in both spring 2022 and 2023. Hospitalisations in individuals positive by PCR for COVID-19 were obtained from the national secondary user service hospital dataset. The ratio of hospital counts by each year of age in 8-week periods after compared to before the roll out was modelled using negative binomial regression to estimate the discontinuity at age 75 years. RESULTS: A clear discontinuity was seen at age 75 years of 17.0% (95% CI: 6.1%-26.6%) in 2022 and 18.0% (3.3%-30.4%) in 2023. If applied to those aged ≥75 years this translates to 1302 and 418 averted hospitalisations in the 8-week period in 2022 and 2023, respectively. CONCLUSIONS: This study shows a clear impact of vaccination on preventing COVID-19 hospitalisations and compliments other epidemiological methods assessing the impact of COVID-19 vaccines. PLAIN LANGUAGE SUMMARY: One way to see if the booster vaccines doses given to protect against COVID-19 disease are working is to compare hospital admissions in groups of people who were and were not eligible for the dose. In England the spring booster doses were recommended for those aged 75 years and above. We could therefore compare hospitalisations in those above this age to those just below (aged 65-74) and see if there is a step change in rates from age 74 to 75 in the time after the vaccine was given. The results showed hospitalisations were about 18% lower in the group that were eligible, which is evidence that the vaccine is protecting against severe COVID-19.

Effectiveness of autumn 2023 COVID-19 vaccination and residual protection of prior doses against hospitalisation in England, estimated using a test-negative case-control study.

INTRODUCTION: The last COVID-19 vaccine offered to all adults in England became available from November 2021. The most recent booster programme commenced in September 2023. Bivalent BA.4-5 or monovalent XBB.1.5 boosters were given. During the study period, the JN.1 variant became dominant in England. METHODS: Vaccine effectiveness against hospitalisation was estimated throughout using the test-negative case-control study design where positive PCR tests from hospitalised individuals are cases and comparable negative PCR tests are controls. Multivariable logistic regression was used to assess vaccine effectiveness against hospitalisation with the test result as the outcome, vaccination status as the primary exposure variable of interest and confounder adjustment. RESULTS: There was no evidence of residual protection for boosters given as part of previous campaigns. There were 28,916 eligible tests included to estimate the effectiveness of the autumn 2023 boosters in those aged 65 years and older. VE peaked at 50.6% (95% CI: 44.2-56.3%) after 2-4 weeks, followed by waning to 13.6% (95% CI: -11.7 to 33.2%). Estimates were generally higher for the XBB.1.5 booster than the BA.4-5 booster, but this difference was not statistically significant. Point estimates were highest against XBB sub-lineages. Effectiveness was lower against both JN.1 and EG.5.1 variants with confidence intervals non-overlapping with the effectiveness of the XBB sub-lineages at 2-4 weeks for EG.5.1 where VE was 44.5% (95% CI: 20.2-61.4%) and at 5-9 weeks for JN.1 where VE was 26.4% (95%CI: -3.4 to 47.6%). CONCLUSIONS: The recent monovalent XBB.1.5 and bivalent BA.4-5 boosters provided comparable and good protection against hospitalisation, however there was evidence of lower VE against hospitalisation of these boosters against JN.1.

Neutrophils in respiratory viral infections.

Viral respiratory infections are a common cause of severe disease, especially in infants, people who are immunocompromised, and in the elderly. Neutrophils, an important innate immune cell, infiltrate the lungs rapidly after an inflammatory insult. The most well-characterized effector mechanisms by which neutrophils contribute to host defense are largely extracellular and the involvement of neutrophils in protection from numerous bacterial and fungal infections is well established. However, the role of neutrophils in responses to viruses, which replicate intracellularly, has been less studied. It remains unclear whether and, by which underlying immunological mechanisms, neutrophils contribute to viral control or confer protection against an intracellular pathogen. Furthermore, neutrophils need to be tightly regulated to avoid bystander damage to host tissues. This is especially relevant in the lung where damage to delicate alveolar structures can compromise gas exchange with life-threatening consequences. It is inherently less clear how neutrophils can contribute to host immunity to viruses without causing immunopathology and/or exacerbating disease severity. In this review, we summarize and discuss the current understanding of how neutrophils in the lung direct immune responses to viruses, control viral replication and spread, and cause pathology during respiratory viral infections.

MAVS Deficiency Is Associated With a Reduced T Cell Response Upon Secondary RSV Infection in Mice.

Infections with respiratory syncytial virus (RSV) occurs repeatedly throughout life because sustained, protective memory responses fail to develop. Why this occurs is not known. During RSV infection the recognition of the virus via the cytosolic RIG-I like receptors and signaling via the adaptor protein MAVS is crucial for mounting an innate immune response. However, if this signaling pathway is important for T cell responses during primary infection and during re-infection is not fully elucidated. We describe a second peak of pro-inflammatory mediators during the primary immune response to RSV that coincides with the arrival of T cells into the lung. This second peak of cytokines/chemokines is regulated differently than the early peak and is largely independent of signaling via MAVS. This was concurrent with Mavs-/- mice mounting a strong T cell response to primary RSV infection, with robust IFN-γ; and Granzyme B production. However, after RSV re-infection, Mavs-/- mice showed fewer CD4+ and CD8+ short term memory T cells and their capacity to produce IFN-γ; and Granzyme B, was decreased. In sum, cytosolic recognition of RSV is important not only for initiating innate anti-viral responses but also for generating or maintaining efficient, short term T cell memory responses.

Neutrophil recruitment and activation are differentially dependent on MyD88/TRIF and MAVS signaling during RSV infection.

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections, especially in infants. Lung neutrophilia is a hallmark of RSV disease but the mechanism by which neutrophils are recruited and activated is unclear. Here, we investigate the innate immune signaling pathways underlying neutrophil recruitment and activation in RSV-infected mice. We show that MyD88/TRIF signaling is essential for lung neutrophil recruitment while MAVS signaling, leading to type I IFN production, is necessary for neutrophil activation. Consistent with that notion, administration of type I IFNs to the lungs of RSV-infected Mavs-/- mice partially activates lung neutrophils recruited via the MyD88/TRIF pathway. Conversely, lack of neutrophil recruitment to the lungs of RSV-infected Myd88/Trif-/- mice can be corrected by administration of chemoattractants and those neutrophils become fully activated. Interestingly, Myd88/Trif-/- mice did not have increased lung viral loads during RSV infection, suggesting that neutrophils are dispensable for viral control. Thus, two distinct pathogen sensing pathways collaborate for neutrophil recruitment and full activation during RSV infection.

Novel DNA sensor system for highly sensitive and quantitative retrovirus detection using virus encoded integrase as a biomarker.

In the current study we describe a novel DNA sensor system that allows the detection of single catalytic DNA integration events mediated by retrovirus encoded integrase (IN) present in viral particles. This is achieved by rolling circle amplification mediated conversion of enzymatic reactions happening within nanometer dimensions to directly detectable micrometer sized DNA products. The system utilizes the unique integration reaction of IN to generate a surface anchored nicked DNA circle that serves as a substrate for rolling circle amplification and allows for specific, quantitative and sensitive detection of purified recombinant IN or virus particles with a detection limit of less than 30 virus particles per µL of sample. Moreover, by modifying the nucleotide sequences of the utilized DNA it was possible to tailor the system to distinguish between the highly pathogenic lentivirus HIV and the gammaretrovirus murine leukemia virus present in a given sample. Infections with HIV remain a major threat to global health with more than 2 million new infections and 1 million deaths each year. The sensitive and specific detection of HIV particles based on IN activity holds promise for the development of a new type of diagnostic tools suitable for early (within hours of infection) detection of HIV, which would be valuable for prevention strategies as well as for efficient treatment.