Tracking the clonal dynamics of SARS-CoV-2-specific T cells in children and adults with mild/asymptomatic COVID-19.

Children infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) develop less severe coronavirus disease 2019 (COVID-19) than adults. The mechanisms for the age-specific differences and the implications for infection-induced immunity are beginning to be uncovered. We show by longitudinal multimodal analysis that SARS-CoV-2 leaves a small footprint in the circulating T cell compartment in children with mild/asymptomatic COVID-19 compared to adult household contacts with the same disease severity who had more evidence of systemic T cell interferon activation, cytotoxicity and exhaustion. Children harbored diverse polyclonal SARS-CoV-2-specific naïve T cells whereas adults harbored clonally expanded SARS-CoV-2-specific memory T cells. A novel population of naïve interferon-activated T cells is expanded in acute COVID-19 and is recruited into the memory compartment during convalescence in adults but not children. This was associated with the development of robust CD4+ memory T cell responses in adults but not children. These data suggest that rapid clearance of SARS-CoV-2 in children may compromise their cellular immunity and ability to resist reinfection.

First Report of Candidatus Mycoplasma haemohominis Infection in Australia Causing Persistent Fever in an Animal Carer.

BACKGROUND: Hemotropic mycoplasmas (hemoplasmas) infect animals and humans and can lead to clinical syndromes mainly characterized by hemolytic anemia. A novel pathogen, Candidatus Mycoplasma haemohominis, was recently associated with a case of human hemoplasmosis in Europe. Here we report the first detection of this pathogen in an Australian patient exhibiting persistent fever, hemolytic anemia, and pancytopenia over a 10-month period. METHODS: After exhaustive negative testing for human infectious diseases, whole genome sequencing (WGS) was performed on the patient's bone marrow aspirate, using an Illumina NextSeq500 platform. Conventional polymerase chain reaction (PCR), followed by Sanger sequencing, was then performed on blood samples using novel Mycoplasma-specific primers targeting the 16S ribosomal RNA gene. In addition, a Mycoplasma-specific fluorescence in situ hybridization (FISH) assay was developed to differentiate Mycoplasma cells from other erythrocyte inclusions (eg, Pappenheimer and Howell-Jolly bodies) which are morphologically similar to bacterial cocci by light microscopy. RESULTS: WGS analysis revealed that approximately 0.04% of the total number of unmapped reads to human genome corresponded to Mycoplasma species. A 1-kb Mycoplasma 16S fragment was successfully amplified by conventional PCR, and sequence analyses revealed 100% identity with Candidatus Mycoplasma haemohominis. FISH confirmed that several (approximately 2%) epierythrocytic inclusions initially observed by light microscopy corresponded to Mycoplasma cells. CONCLUSIONS: This represents the second report of hemolytic anemia associated with hemoplasma infection in a human, and the first report of human hemoplasmosis in Australia. This study highlights the importance of new and emerging diagnostic approaches and need for further investigations on the epidemiology of Candidatus Mycoplasma haemohominis in Australia.

Demographics, clinical characteristics and outcomes among 197 patients with COVID-19 in the Gold Coast area.

BACKGROUND: Clinical characteristics and outcomes of coronavirus disease 2019 (COVID-19) patients have been varied internationally but have not been studied in an Australian cohort. AIM: To describe characteristics and outcomes of approximately the first 200 documented COVID-19 cases during the first outbreak in the Gold Coast. METHODS: Retrospective observational cohort study of COVID-19 patients managed by Gold Coast Hospital and Health Service (GCHHS). Demographics, clinical characteristics and outcomes data were collected. RESULTS: One hundred and ninety-seven patients were included (mean age 45 years); 52.3% were female and 9.1% were healthcare workers. Most were overseas travellers (53.8%), contacts of a local confirmed case (25.4%) or cruise ship passengers (17.3%). The commonest comorbidities were hypertension (14.2%) and asthma (11.2%). The commonest symptoms were cough (74.1%), fever (58.9%), sore throat (48.7%), headache (48.7%) and rhinorrhoea (46.2%). Sixty-three patients were hospitalised and the rest admitted to a 'virtual ward'. Of 63 hospitalised patients, 5 (7.9%) required intensive care unit (ICU) admission and 3 (4.8%) required intubation. No patients died. Due to low numbers of accurate exposure dates, the incubation period could not be reliably calculated for a significant proportion of the cohort. Average duration of symptoms was 14 days, time from first symptom to hospitalisation was 5.3 days and time from first symptom to ICU admission was 11.6 days. The majority (88%) experienced mild disease and achieved complete symptom resolution (97%). Nasopharyngeal swab polymerase chain reaction was the main diagnostic method (99%). Twenty-four patients received anti-viral pharmacotherapy, with 87.5% getting hydroxychloroquine. CONCLUSIONS: The present study provides characteristics and outcomes of the first 197 patients with COVID-19 in the Gold Coast.

COVID-19 in Australia: our national response to the first cases of SARS-CoV-2 infection during the early biocontainment phase.

BACKGROUND: On 31 December 2019, the World Health Organization recognised clusters of pneumonia-like cases due to a novel coronavirus disease (COVID-19). COVID-19 became a pandemic 71 days later. AIM: To report the clinical and epidemiological features, laboratory data and outcomes of the first group of 11 returned travellers with COVID-19 in Australia. METHODS: This is a retrospective, multi-centre case series. All patients with confirmed COVID-19 infection were admitted to tertiary referral hospitals in New South Wales, Queensland, Victoria and South Australia. RESULTS: The median age of the patient cohort was 42 years (interquartile range (IQR), 24-53 years) with six men and five women. Eight (72.7%) patients had returned from Wuhan, one from Shenzhen, one from Japan and one from Europe. Possible human-to-human transmission from close family contacts in gatherings overseas occurred in two cases. Symptoms on admission were fever, cough and sore throat (n = 9, 81.8%). Co-morbidities included hypertension (n = 3, 27.3%) and hypercholesterolaemia (n = 2, 18.2%). No patients developed severe acute respiratory distress nor required intensive care unit admission or mechanical ventilation. After a median hospital stay of 14.5 days (IQR, 6.75-21), all patients were discharged. CONCLUSIONS: This is a historical record of the first COVID-19 cases in Australia during the early biocontainment phase of the national response. These findings were invaluable for establishing early inpatient and outpatient COVID-19 models of care and informing the management of COVID-19 over time as the outbreak evolved. Future research should extend this Australian case series to examine global epidemiological variation of this novel infection.

Controlled Infection Immunization Using Delayed Death Drug Treatment Elicits Protective Immune Responses to Blood-Stage Malaria Parasites.

Naturally acquired immunity to malaria is robust and protective against all strains of the same species of Plasmodium This develops as a result of repeated natural infection, taking several years to develop. Evidence suggests that apoptosis of immune lymphocytes due to uncontrolled parasite growth contributes to the slow acquisition of immunity. To hasten and augment the development of natural immunity, we studied controlled infection immunization (CII) using low-dose exposure to different parasite species (Plasmodium chabaudi, P. yoelii, or P. falciparum) in two rodent systems (BALB/c and C57BL/6 mice) and in human volunteers, with drug therapy commencing at the time of initiation of infection. CIIs with infected erythrocytes and in conjunction with doxycycline or azithromycin, which are delayed death drugs targeting the parasite's apicoplast, allowed extended exposure to parasites at low levels. In turn, this induced strong protection against homologous challenge in all immunized mice. We show that P. chabaudi/P. yoelii infection initiated at the commencement of doxycycline therapy leads to cellular or antibody-mediated protective immune responses in mice, with a broad Th1 cytokine response providing the best correlate of protection against homologous and heterologous species of PlasmodiumP. falciparum CII with doxycycline was additionally tested in a pilot clinical study (n = 4) and was found to be well tolerated and immunogenic, with immunological studies primarily detecting increased cell-associated immune responses. Furthermore, we report that a single dose of the longer-acting drug, azithromycin, given to mice (n = 5) as a single subcutaneous treatment at the initiation of infection controlled P. yoelii infection and protected all mice against subsequent challenge.

Vaccination with chemically attenuated Plasmodium falciparum asexual blood-stage parasites induces parasite-specific cellular immune responses in malaria-naïve volunteers: a pilot study.

BACKGROUND: The continuing morbidity and mortality associated with infection with malaria parasites highlights the urgent need for a vaccine. The efficacy of sub-unit vaccines tested in clinical trials in malaria-endemic areas has thus far been disappointing, sparking renewed interest in the whole parasite vaccine approach. We previously showed that a chemically attenuated whole parasite asexual blood-stage vaccine induced CD4+ T cell-dependent protection against challenge with homologous and heterologous parasites in rodent models of malaria. METHODS: In this current study, we evaluated the immunogenicity and safety of chemically attenuated asexual blood-stage Plasmodium falciparum (Pf) parasites in eight malaria-naïve human volunteers. Study participants received a single dose of 3 × 107 Pf pRBC that had been treated in vitro with the cyclopropylpyrolloindole analogue, tafuramycin-A. RESULTS: We demonstrate that Pf asexual blood-stage parasites that are completely attenuated are immunogenic, safe and well tolerated in malaria-naïve volunteers. Following vaccination with a single dose, species and strain transcending Plasmodium-specific T cell responses were induced in recipients. This included induction of Plasmodium-specific lymphoproliferative responses, T cells secreting the parasiticidal cytokines, IFN-γ and TNF, and CD3+CD45RO+ memory T cells. Pf-specific IgG was not detected. CONCLUSIONS: This is the first clinical study evaluating a whole parasite blood-stage malaria vaccine. Following administration of a single dose of completely attenuated Pf asexual blood-stage parasites, Plasmodium-specific T cell responses were induced while Pf-specific antibodies were not detected. These results support further evaluation of this chemically attenuated vaccine in humans. TRIAL REGISTRATION: Trial registration: ACTRN12614000228684 . Registered 4 March 2014.

A Review of Clinical Cases of Infection with Photorhabdus Asymbiotica.

The three recognised Photorhabdus species are bioluminescent Gram-negative bacilli of the family Enterobacteriaceae. They are all pathogenic to insects and form a symbiotic relationship with nematodes of the genus Heterorhabditis. P. luminescens and P. temperata are both harmless to humans whilst P. asymbiotica, on the other hand, is a human pathogen that is a symbiont of the newly described nematode vector, Heterorhabditis gerrardi. In this chapter, we review the epidemiological and clinical features of eighteen human cases of P. asymbiotica infection including fifteen from the published literature and three previously unreported cases. Human infection has been reported in the USA and Australia and probably occurs in other parts of Asia where it remains undocumented. Infection occurs most commonly in warmer months particularly after rainfall. Patients may have a history of recent exposure to sand or sandy soil. P. asymbiotica causes both locally invasive soft tissue infection and disseminated disease with bacteraemia. Soft tissue infection may be multifocal with involvement of more than one limb and the trunk. The organism is sensitive to a number of antibiotics in vitro, but treatment failures have been associated with the use of beta-lactams and aminoglycosides. We suggest treatment with a four-week course of an oral fluoroquinolone such as ciprofloxacin. The organism grows readily on standard media from specimens such as wound swabs, pus, blood and even sputum and can be identified in a clinical microbiology laboratory but the diagnosis needs to be considered. The correct diagnosis is most likely to be made where there is close cooperation between clinician and microbiologist.

Infectivity of Plasmodium falciparum in Malaria-Naive Individuals Is Related to Knob Expression and Cytoadherence of the Parasite.

Plasmodium falciparum is the most virulent human malaria parasite because of its ability to cytoadhere in the microvasculature. Nonhuman primate studies demonstrated relationships among knob expression, cytoadherence, and infectivity. This has not been examined in humans. Cultured clinical-grade P. falciparum parasites (NF54, 7G8, and 3D7B) and ex vivo-derived cell banks were characterized. Knob and knob-associated histidine-rich protein expression, CD36 adhesion, and antibody recognition of parasitized erythrocytes (PEs) were evaluated. Parasites from the cell banks were administered to malaria-naive human volunteers to explore infectivity. For the NF54 and 3D7B cell banks, blood was collected from the study participants for in vitro characterization. All parasites were infective in vivo However, infectivity of NF54 was dramatically reduced. In vitro characterization revealed that unlike other cell bank parasites, NF54 PEs lacked knobs and did not cytoadhere. Recognition of NF54 PEs by immune sera was observed, suggesting P. falciparum erythrocyte membrane protein 1 expression. Subsequent recovery of knob expression and CD36-mediated adhesion were observed in PEs derived from participants infected with NF54. Knobless cell bank parasites have a dramatic reduction in infectivity and the ability to adhere to CD36. Subsequent infection of malaria-naive volunteers restored knob expression and CD36-mediated cytoadherence, thereby showing that the human environment can modulate virulence.

Venoarterial extracorporeal membrane oxygenation for cardiac support in human immunodeficiency virus-positive patients: a case report and review of a multicentre registry.

BACKGROUND: Human immunodeficiency virus (HIV) is associated with increased risk of heart failure via multiple mechanisms both in patients with and without access to highly active antiretroviral therapy (HAART). Limited information is available on outcomes among this population supported on Venoarterial Extracorporeal Membrane Oxygenation (VA ECMO), a form of temporary mechanical circulatory support. METHODS: We aimed to assess outcomes and complications among patients with HIV supported on VA ECMO reported to a multicentre registry and present a case report of a 32 year old male requiring VA ECMO for cardiogenic shock as a consequence of his untreated HIV and acquired immune deficiency syndrome (AIDS). A retrospective analysis of the Extracorporeal Life Support Organization (ELSO) registry data from 1989 to 2019 was performed in HIV patients supported on VA ECMO. RESULTS: 36 HIV positive patients were reported to the ELSO Database who received VA ECMO during the study period with known outcomes. 15 patients (41%) survived to discharge. No significant differences existed between survivors and non-survivors in demographic variables, duration of VA ECMO support or cardiac parameters. Inotrope and/or vasopressor requirement prior to or during VA ECMO support was associated with increased mortality. Survivors were more likely to develop circuit thrombosis. The patient presented was supported on VA ECMO for 14 days and was discharged from hospital day 85. CONCLUSIONS: A limited number of patients with HIV have been supported with VA ECMO and more data is required to ascertain the indications for ECMO in this population. HIV should not be considered an absolute contraindication to VA ECMO as they may have comparable outcomes to other patient groups requiring VA ECMO support.

Predicting influenza A and 2009 H1N1 influenza in patients admitted to hospital with acute respiratory illness.

OBJECTIVE: To create a clinical decision tool for suspected influenza A (including 2009 H1N1) to facilitate treatment and isolation decisions for patients admitted to hospital with an acute respiratory illness from the emergency department (ED) during a 2009 H1N1 pandemic. METHODS: Cross-sectional study conducted in two hospitals in Queensland, Australia. All patients admitted to hospital from the ED between 24 May and 16 August 2009 with an acute respiratory illness were included. All had nasal and throat swabs taken. Data were collected from clinical chart review regarding clinical symptoms, co-morbidities, examination findings, pathology and radiology results. Influenza A status was detected by reverse transcription-PCR assay. Univariate and multivariate regression analyses were performed to identify independent predictors of influenza A status. RESULTS: 346 consecutive patients were identified, of which 106 were positive for 2009 H1N1 influenza; an additional 11 patients were positive for other influenza A viruses. Independent clinical predictors (with points allocated using weighted scoring) for all types of influenza A in patients admitted with acute respiratory illness were: age 18-64 years (2 points); history of fever (2); cough (1); normal level of consciousness (2); C-reactive protein >5 and ≤ 100 mg/l (2) and normal leucocyte count (1). A clinical score of 5 (presence of two or three predictors) gave a sensitivity of 93% (95% CI 87% to 96%), specificity of 36% (95% CI 30% to 42%), resulting in a negative-predictive value of 91% (95% CI 83% to 95%). CONCLUSION: A clinical prediction tool was developed that may be able to assist in making appropriate isolation decisions during future 2009 H1N1 outbreaks.

Antibodies to neutralising epitopes synergistically block the interaction of the receptor-binding domain of SARS-CoV-2 to ACE 2.

OBJECTIVES: A major COVID-19 vaccine strategy is to induce antibodies that prevent interaction between the Spike protein's receptor-binding domain (RBD) and angiotensin-converting enzyme 2 (ACE2). These vaccines will also induce T-cell responses. However, concerns were raised that aberrant vaccine-induced immune responses may exacerbate disease. We aimed to identify minimal epitopes on the RBD that would induce antibody responses that block the interaction of the RBD and ACE2 as a strategy leading to an effective vaccine with reduced risk of inducing immunopathology. METHODS: We procured a series of overlapping 20-amino acid peptides spanning the RBD and asked which were recognised by plasma from COVID-19 convalescent patients. Identified epitopes were conjugated to diphtheria-toxoid and used to vaccinate mice. Immune sera were tested for binding to the RBD and for their ability to block the interaction of the RBD and ACE2. RESULTS: Seven putative vaccine epitopes were identified. Memory B-cells (MBCs) specific for one of the epitopes were identified in the blood of convalescent patients. When used to vaccinate mice, six induced antibodies that bound recRBD and three induced antibodies that could partially block the interaction of the RBD and ACE2. However, when the sera were combined in pairs, we observed significantly enhanced inhibition of binding of RBD to ACE2. Two of the peptides were located in the main regions of the RBD known to contact ACE2. Of significant importance to vaccine development, two of the peptides were in regions that are invariant in the UK and South African strains. CONCLUSION: COVID-19 convalescent patients have SARS-CoV-2-specific antibodies and MBCs, the specificities of which can be defined with short peptides. Epitope-specific antibodies synergistically block RBD-ACE2 interaction.

Outbreak of health care-associated Burkholderia cenocepacia bacteremia and infection attributed to contaminated sterile gel used for central line insertion under ultrasound guidance and other procedures.

BACKGROUND: We report an outbreak of Burkholderia cenocepacia bacteremia and infection in 11 patients predominately in intensive care units caused by contaminated ultrasound gel used in central line insertion and sterile procedures within 4 hospitals across Australia. METHODS: Burkholderia cenocepacia was first identified in the blood culture of a patient from the intensive care unit at the Gold Coast University Hospital on March 26, 2017, with 3 subsequent cases identified by April 7, 2017. The outbreak response team commenced investigative measures. RESULTS: The outbreak investigation identified the point source as contaminated gel packaged in sachets for use within the sterile ultrasound probe cover. In total, 11 patient isolates of B cenocepacia with the same multilocus sequence type were identified within 4 hospitals across Australia. This typing was the same as identified in the contaminated gel isolate with single nucleotide polymorphism-based typing, demonstrating that all linked isolates clustered together. CONCLUSION: Arresting the national point-source outbreak within multiple jurisdictions was critically reliant on a rapid, integrated, and coordinated response and the use of informal professional networks to first identify it. All institutions where the product is used should look back at Burkholderia sp blood culture isolates for speciation to ensure this outbreak is no larger than currently recognized given likely global distribution.

Protein-based profiling of the immune response to uropathogenic Escherichia coli in adult patients immediately following hospital admission for acute cystitis.

Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) are common infections in humans. Despite the substantial healthcare cost represented by these infections, the human immune response associated with the infection immediately following the onset of symptoms in patients remains largely undefined. We performed a prospective study aimed at defining the milieu of urinary cytokines in adult inpatients in the 24-48 h period immediately following hospital admission for acute cystitis due to UPEC. Urine samples, analyzed using 27-target multiplex protein assays, were used to generate immune profiles for patients and compared to age- and gender-matched healthy controls. The levels of multiple pro-inflammatory cytokines were significantly elevated in urine as a result of infection, an observation consistent with prior findings in murine models and clinical literature. We also identified significant responses for several novel factors not previously associated with the human response to UTI, including Interleukin (IL)-4, IL-7, IL-9, IL-17A, eotaxin, Granulocyte-macrophage colony-stimulating factor (GM-CSF) and several growth factors. These data establish crucial parallels between the human immune response to UPEC and murine model UTI studies, and emphasize the complex but poorly defined nature of the human immune response to UPEC, particularly in the immediate period following the onset of symptoms for acute cystitis.

Surgeons' perspectives on surgical wound infection rate data in Queensland, Australia.

BACKGROUND: The results of the Study on the Efficacy of Nosocomial Infection Control (SENIC) project demonstrated that hospitals with active infection control programs had lower rates of nosocomial infection than those without such programs. A key component of these programs was the inclusion of a systematic method for monitoring nosocomial infection and reporting these infections to clinicians. OBJECTIVES: To identify the perspectives of surgeons in Queensland, Australia, regarding infection rate data in terms of its accuracy and usefulness as well as their perceptions regarding acceptable infection rates for surgical procedures classified as "clean" or "contaminated." METHODS: A postal survey was conducted, with a convenience sample of 510 surgeons. RESULTS: More than 40% (n = 88) of respondents believed that the acceptable infection rate associated with clean surgical procedures should be less than 1%, a rate much lower than the threshold of 1.4% to 4.1% set by the Australian Council on Healthcare Standards (ACHS). Almost 30% (n = 55) of respondents reported that they would accept infection rates of 10% or higher for contaminated surgical procedures, which is higher than the ACHS threshold of 1.4% to 7.9%. Respondents identified failure to include postdischarge infections in the data and difficulties standardizing criteria for diagnosis of infection as the major impediments to the accuracy and usefulness of data provided. CONCLUSION: The results of this study have significant implications in relation to the preparation of surgical site infection reports, especially in relation to the inclusion of postdischarge surveillance data and information regarding pathogens, antibiotic sensitivities, and comorbidities of patients developing surgical site infection. Surgeons also identified the need to include information regarding the use of standardized definitions in the diagnosis of wound infection and parameters that allow comparison of infection rates to improve their perceptions regarding data accuracy and usefulness.