HCMV exploits STING signaling and counteracts IFN and ISG induction to facilitate dendritic cell infection

Human cytomegalovirus (HCMV) is a widespread obligatory human pathogen causing life-threatening disease in immunocompromised hosts. Myeloid cells such as monocyte-derived dendritic cells (moDCs) are targets of HCMV. Here, we performed single-cell RNA sequencing, which revealed infection of most moDCs upon in vitro HCMV exposure, whereas only a fraction of them initiated viral gene expression. We identified three moDC subsets, of which CD1a−/CD86− cells showed the highest susceptibility. Upon HCMV entry, STING activation not only induced IFN-β, but also promoted viral gene expression. Upon progression of infection, IFN-β but not IFN-λ1 expression was inhibited. Similarly, ISG expression was initially induced and then shut off and thus allowed productive infection. Increased viral gene expression was associated with the induction of several pro- (RHOB, HSP1A1, DNAJB1) and anti-viral (RNF213, TNFSF10, IFI16) genes. Thus, moDC permissiveness to HCMV depends on complex interactions between virus sensing, regulation of IFNs/ISGs and viral gene expression.

Antigenic evolution of SARS-CoV-2 in immunocompromised hosts

The apparent lack of antigenic evolution by the Delta variant (B.1.617.2) of SARS-CoV-2 during the COVID-19 pandemic is puzzling. The combination of increasing immune pressure due to the rollout of vaccines and a relatively high number of infections following the relaxation of non-pharmaceutical interventions should have created perfect conditions for immune escape variants to evolve from the Delta lineage. Instead, the Omicron variant (B.1.1.529), which is hypothesised to have evolved in an immunocompromised individual, is the first major variant to exhibit significant immune escape following vaccination programmes and is set to become globally dominant in 2022. Here, we use a simple mathematical model to explore possible reasons why the Delta lineage did not exhibit antigenic evolution and to understand how and when immunocompromised individuals affect the emergence of immune escape variants. We show that when the pathogen does not have to cross a fitness valley for immune escape to occur, immunocompromised individuals have no qualitative effect on antigenic evolution (although they may accelerate immune escape if within-host evolutionary dynamics are faster in immunocompromised individuals). But if a fitness valley exists between immune escape variants at the between-host level, then persistent infections of immunocompromised individuals allow mutations to accumulate, therefore facilitating rather than simply speeding up antigenic evolution. Our results suggest that better global health equality, including improving access to vaccines and treatments for individuals who are immunocompromised (especially in lower- and middle-income countries), may be crucial to preventing the emergence of future immune escape variants of SARS-CoV-2.

Host defense mechanisms induce genome instability leading to rapid evolution in an opportunistic fungal pathogen

The ability to generate genetic variation facilitates rapid adaptation in stressful environments. The opportunistic fungal pathogen Candida albicans frequently undergoes large-scale genomic changes, including aneuploidy and loss-of heterozygosity (LOH), following exposure to host environments. However, the specific host factors inducing C. albicans genome instability remain largely unknown. Here, we leveraged the genetic tractability of nematode hosts to investigate whether innate immune components, including antimicrobial peptides (AMPs) and reactive oxygen species (ROS), induced host-associated C. albicans genome instability. C. albicans associated with immunocompetent hosts carried multiple large-scale genomic changes including LOH, whole chromosome, and segmental aneuploidies. In contrast, C. albicans associated with immunocompromised hosts deficient in AMPs or ROS production had reduced LOH frequencies and fewer, if any, additional genomic changes. To evaluate if extensive host-induced genomic changes had long-term consequences for C. albicans adaptation, we experimentally evolved C. albicans in either immunocompetent or immunocompromised hosts and selected for increased virulence. C. albicans evolved in immunocompetent hosts rapidly increased virulence, but not in immunocompromised hosts. Taken together, this work suggests that host-produced ROS and AMPs induces genotypic plasticity in C. albicans which facilitates rapid evolution.

Cryptococcal Infection with Ruxolitinib in Primary Myelofibrosis: A Case Report and Literature Review

Cryptococcus neoformans (CN) is an encapsulated yeast that causes disseminated and potentially life-threatening in immunocompromised hosts. We present a patient with primary myelofibrosis on ruxolitinib who developed disseminated disease due to CN. The report underscores the importance of suspecting infections with intracellular pathogens in immunosuppressed patients on ruxolitinib.

Genomic and Metabolic Characteristics of the Pathogenicity in Pseudomonas aeruginosa

In recent years, the effectiveness of antimicrobials in the treatment of Pseudomonas aeruginosa infections has gradually decreased. This pathogen can be observed in several clinical cases, such as pneumonia, urinary tract infections, sepsis, in immunocompromised hosts, such as neutropenic cancer, burns, and AIDS patients. Furthermore, Pseudomonas aeruginosa causes diseases in both livestock and pets. The highly flexible and versatile genome of P. aeruginosa allows it to have a high rate of pathogenicity. The numerous secreted virulence factors, resulting from its numerous secretion systems, the multi-resistance to different classes of antibiotics, and the ability to produce biofilms are pathogenicity factors that cause numerous problems in the fight against P. aeruginosa infections and that must be better understood for an effective treatment. Infections by P. aeruginosa represent, therefore, a major health problem and, as resistance genes can be disseminated between the microbiotas associated with humans, animals, and the environment, this issue needs be addressed on the basis of an One Health approach. This review intends to bring together and describe in detail the molecular and metabolic pathways in P. aeruginosa’s pathogenesis, to contribute for the development of a more targeted therapy against this pathogen.

Acute Suppurative Thyroiditis Secondary to Escherichia coli Infection

Infections of the thyroid gland are rare. Its innate resistance to infections can be attributed to its unique anatomical features and rich blood supply. High clinical suspicion is required as a delay in diagnosis can lead to significant morbidity and mortality. Major pathogens include the Gram-positive Staphylococcus aureus and Streptococcus species; however, Gram-negative organisms have been found especially in immunocompromised hosts. We present a rare case of acute suppurative thyroiditis (AST) secondary to Escherichia coli (E. coli) infection in a woman known to be infected with human immunodeficiency virus (HIV).

Vaccination Schedules

First vaccines and vaccination schedules were based on “trial and error” and on immunogenicity data (serology). Latest since the 1990s, vaccination schedules are based on well-defined phase 1–3 development programs as basis for licensure of any new product. Vaccination schedules must bear in mind the epidemiology of the targeted disease; the biology of available vaccine product(s); local opportunities to vaccinate; monitoring for the desired outcome. There are 4 basic primary vaccination schedules for children, based on historical development and local needs. Birth doses are recommended with BCG and hepatitis B vaccine. Dosing in the 2nd year of life is usually needed for long term-protection induced by polysaccharide-conjugate vaccines. Live vaccines (MMR, VZV) are usually given as of 9 months of age – later dosing may induce improved immune responses; a second dose is needed before school entry for optimal protection. In addition to “general regular schedules” vaccines and schedules emerge for pregnant women, international travelers, persons above 60 or 65 years, immunocompromised hosts.

Radionuclide Imaging of Invasive Fungal Disease in Immunocompromised Hosts

Invasive fungal disease (IFD) leads to increased mortality, morbidity, and costs of treatment in patients with immunosuppressive conditions. The definitive diagnosis of IFD relies on the isolation of the causative fungal agents through microscopy, culture, or nucleic acid testing in tissue samples obtained from the sites of the disease. Biopsy is not always feasible or safe to be undertaken in immunocompromised hosts at risk of IFD. Noninvasive diagnostic techniques are, therefore, needed for the diagnosis and treatment response assessment of IFD. The available techniques that identify fungal-specific antigens in biological samples for diagnosing IFD have variable sensitivity and specificity. They also have limited utility in response assessment. Imaging has, therefore, been applied for the noninvasive detection of IFD. Morphologic imaging with computed tomography (CT) and magnetic resonance imaging (MRI) is the most applied technique. These techniques are neither sufficiently sensitive nor specific for the early diagnosis of IFD. Morphologic changes evaluated by CT and MRI occur later in the disease course and during recovery after successful treatment. These modalities may, therefore, not be ideal for early diagnosis and early response to therapy determination. Radionuclide imaging allows for targeting the host response to pathogenic fungi or specific structures of the pathogen itself. This makes radionuclide imaging techniques suitable for the early diagnosis and treatment response assessment of IFD. In this review, we aimed to discuss the interplay of host immunity, immunosuppression, and the occurrence of IFD. We also discuss the currently available radionuclide probes that have been evaluated in preclinical and clinical studies for their ability to detect IFD.

Cellular and humoral Immune response to mRNA COVID-19 vaccination in subjects with chronic lymphocytic leukemia

Chronic Lymphocytic Leukemia (CLL) is predominantly a B-lymphocyte leukemia associated with immune defects that are often exacerbated by CLL directed therapies. SARS-CoV-2 infection poses a significant risk of illness or mortality to CLL patients, and while SARS-CoV-2 vaccines are highly effective in immunocompetent individuals, efficacy varies substantially in immunocompromised patients, including those with CLL. To date, studies of COVID-19 vaccine immune responses in immunocompromised hosts have largely relied on semi-quantitative antibody titers that only partially characterize vaccine-elicited immune responses and do not measure B or T-cell specific responses that may also play a protective role in vaccinees. Here, we report RBD-specific antibody as well as B-cell and T-cell responses in an observational cohort of sixteen CLL subjects who received mRNA vaccination against SARS-CoV-2, finding a strong association between CLL treatment and vaccine immunogenicity, with important implications for vaccination timing in the context of CLL treatment or recovery from prior treatment.

P.031 A Rare Canadian Case of Cervical Pyomyosistis Presenting as Occipital Neuralgia

Background: Pyomyositis is an infectious disease usually encountered in tropical regions. It typically occurs in immunocompromised hosts and most commonly affects lower limb muscles. Our patient was a healthy Canadian with an atypical presentation of cervical pyomyositis. Methods: We report a case of a healthy 22-year old woman presenting to the emergency department with unprovoked severe bilateral cervico-occipital pain and nuchal rigidity. She remained afebrile. Review of the literature was conducted to search for similar presentations. Results: A Computed Tomography scan of the head and neck demonstrated the presence of a ring enhancing lesion in the semispinalis capitis muscle extending from the occiput to the C4 level. The abscess was surgically drained and cultures grew staphylococcus aureus. The patient rapidly improved on intravenous antibiotics. Literature review revealed this to be the first Canadian case of cervical pyomyositis. Conclusions: Cervical pyomyositis can be complicated by local destruction of the vertebrae, septic shock, endocarditis, septic emboli, brain abscess or rhabdomyolysis. Early diagnosis and source control is necessary to reduce the risk of morbidity. Therefore, it is important to consider this rare disease in the differential diagnosis of cervicalgia even in healthy immunocompetent patients.