Evaluation of Genetic or Cellular Impairments in Type I IFN Immunity in a Cohort of Young Adults with Critical COVID-19

Several genetic and immunological risk factors for severe COVID-19 have been identified, with monogenic conditions relating to 13 genes of type I interferon (IFN) immunity proposed to explain 4.8% of critical cases. However, previous cohorts have been clinically heterogeneous and were not subjected to thorough genetic and immunological analyses. We therefore aimed to systematically investigate the prevalence of rare genetic variants causing inborn errors of immunity (IEI) and functionally interrogate the type I IFN pathway in young adults that suffered from critical COVID-19 yet lacked comorbidities. We selected and clinically characterized a cohort of 38 previously healthy individuals under 50 years of age who were treated in intensive care units due to critical COVID-19. Blood samples were collected after convalescence. Two patients had IFN-α autoantibodies. Genome sequencing revealed very rare variants in the type I IFN pathway in 31.6% of the patients, which was similar to controls. Analyses of cryopreserved leukocytes did not indicate any defect in plasmacytoid dendritic cell sensing of TLR7 and TLR9 agonists in patients carrying variants in these pathways. However, lymphocyte STAT phosphorylation and protein upregulation upon IFN-α stimulation revealed three possible cases of impaired type I IFN signaling in carriers of rare variants. Together, our results suggest a strategy of functional screening followed by genome analyses and biochemical validation to uncover undiagnosed causes of critical COVID-19.

Respiratory viral infections in otherwise healthy humans with inherited IRF7 deficiency

Autosomal recessive IRF7 deficiency was previously reported in three patients with single critical influenza or COVID-19 pneumonia episodes. The patients' fibroblasts and plasmacytoid dendritic cells produced no detectable type I and III IFNs, except IFN-β. Having discovered four new patients, we describe the genetic, immunological, and clinical features of seven IRF7-deficient patients from six families and five ancestries. Five were homozygous and two were compound heterozygous for IRF7 variants. Patients typically had one episode of pulmonary viral disease. Age at onset was surprisingly broad, from 6 mo to 50 yr (mean age 29 yr). The respiratory viruses implicated included SARS-CoV-2, influenza virus, respiratory syncytial virus, and adenovirus. Serological analyses indicated previous infections with many common viruses. Cellular analyses revealed strong antiviral immunity and expanded populations of influenza- and SARS-CoV-2-specific memory CD4+ and CD8+ T cells. IRF7-deficient individuals are prone to viral infections of the respiratory tract but are otherwise healthy, potentially due to residual IFN-β and compensatory adaptive immunity.

Functional paralysis of human natural killer cells by alphaherpesviruses

Natural killer (NK) cells are implicated as important anti-viral immune effectors in varicella zoster virus (VZV) infection. VZV can productively infect human NK cells, yet it is unknown how, or if, VZV can directly affect NK cell function. Here we demonstrate that VZV potently impairs the ability of NK cells to respond to target cell stimulation in vitro, leading to a loss of both cytotoxic and cytokine responses. Remarkably, not only were VZV infected NK cells affected, but VZV antigen negative NK cells that were exposed to virus in culture were also inhibited. This powerful impairment of function was dependent on direct contact between NK cells and VZV infected inoculum cells. Profiling of the NK cell surface receptor phenotype by multiparameter flow cytometry revealed that functional receptor expression is predominantly stable. Furthermore, inhibited NK cells were still capable of releasing cytotoxic granules when the stimulation signal bypassed receptor/ligand interactions and early signalling, suggesting that VZV paralyses NK cells from responding. Phosflow examination of key components in the degranulation signalling cascade also demonstrated perturbation following culture with VZV. In addition to inhibiting degranulation, IFN-γ and TNF production were also repressed by VZV co-culture, which was most strongly regulated in VZV infected NK cells. Interestingly, the closely related virus, herpes simplex virus type 1 (HSV-1), was also capable of efficiently infecting NK cells in a cell-associated manner, and demonstrated a similar capacity to render NK cells unresponsive to target cell stimulation–however HSV-1 differentially targeted cytokine production compared to VZV. Our findings progress a growing understanding of pathogen inhibition of NK cell function, and reveal a previously unreported strategy for VZV to manipulate the immune response.

Natural killer (NK) cells–as their name implies–are the immune system’s ready to respond ‘killers’, being able to help control viral infection by cytolytic killing of infected cells and secretion of pro-inflammatory cytokines to activate and direct the immune response. In retaliation, viruses like varicella zoster virus (VZV; the cause of chickenpox and shingles) work to dampen the immune system in order to establish infection in human hosts. We have identified a previously uncharacterised ability of VZV to render NK cells unresponsive to target cells, hindering NK cells from both cytotoxic function and cytokine production. NK cells still maintained predominantly stable expression of functional surface receptors, and were capable of releasing cytotoxic granules when given a receptor-independent stimulus. In this way, VZV paralyses NK cells from functionally responding to target cells, essentially taking the ‘killer’ out of natural killer cells.

Varicella zoster virus productively infects human natural killer cells and manipulates phenotype

Varicella zoster virus (VZV) is a ubiquitous human alphaherpesvirus, responsible for varicella upon primary infection and herpes zoster following reactivation from latency. To establish lifelong infection, VZV employs strategies to evade and manipulate the immune system to its advantage in disseminating virus. As innate lymphocytes, natural killer (NK) cells are part of the early immune response to infection, and have been implicated in controlling VZV infection in patients. Understanding of how VZV directly interacts with NK cells, however, has not been investigated in detail. In this study, we provide the first evidence that VZV is capable of infecting human NK cells from peripheral blood in vitro. VZV infection of NK cells is productive, supporting the full kinetic cascade of viral gene expression and producing new infectious virus which was transmitted to epithelial cells in culture. We determined by flow cytometry that NK cell infection with VZV was not only preferential for the mature CD56^dim NK cell subset, but also drove acquisition of the terminally-differentiated maturity marker CD57. Interpretation of high dimensional flow cytometry data with tSNE analysis revealed that culture of NK cells with VZV also induced a potent loss of expression of the low-affinity IgG Fc receptor CD16 on the cell surface. Notably, VZV infection of NK cells upregulated surface expression of chemokine receptors associated with trafficking to the skin –a crucial site in VZV disease where highly infectious lesions develop. We demonstrate that VZV actively manipulates the NK cell phenotype through productive infection, and propose a potential role for NK cells in VZV pathogenesis.

Varicella zoster virus (VZV) is a pervasive pathogen, causing chickenpox during primary infection and shingles when the virus reactivates from latency. VZV is therefore a lifelong infection for humans, warranting investigation of how this virus interacts with the immune system. One of the first immune cells to respond to viral infection are natural killer (NK) cells, yet little is known about how VZV interacts with NK cells. We demonstrate for the first time that VZV infects human blood NK cells and can use them to pass on infection to other cells in culture. Furthermore, VZV displays a predilection for infecting mature NK cells, and amplifies expression of receptors that would promote trafficking to the skin– the site of highly infectious lesions during chickenpox and shingles. Our findings suggest a role for NK cells in VZV disease and enhances our understanding of how lifelong infections interact with the human immune system.

Bone replaces articular cartilage in the rat knee joint after prolonged immobilization

BACKGROUND

Lost joint range of motion (ROM) is common in chronic osteoarthritis, alters regional weight-bearing across the articular surfaces, and contributes to loss of cartilage and bone alterations. Limited data exist on the regional effects on joints subjected to chronic losses of ROM.

OBJECTIVE

To characterize the regional replacement by bone as part of articular cartilage degeneration after prolonged immobilization.

METHODS

Eleven rat knees were rigidly-immobilized in flexion for 32weeks with contralateral and sham-operated (n=6) knees as controls. Sagittal medial tibial epiphysis histological sections assessed the anterior (non-weight-bearing), middle and posterior (both weight-bearing) regions. We quantified the distribution of collagen I, collagen II, cartilage thickness, glycosaminoglycan (GAG) staining, Mankin scoring, and subchondral bone plate cross-sectional area. Using immunohistochemistry (IHC), we visualized blood vessels, osteoblasts, and mesenchymal stem cells (MSCs).

RESULTS

Immobilized cartilage had increased collagen I content in the anterior tibial region with picrosirius red staining (immobilized=61±20%; contralateral=43±12%, p=0.033; sham=20±10%, p=0.028) and collagen I IHC (immobilized=40±10%; contralateral=11±4%, p=0.003; sham=5±3%, p=0.043). Articular cartilage was thinner anteriorly (18±30μm) in immobilized knees versus contralateral (124±40μm, p<0.001) and sham (125±43μm, p=0.043). GAG staining covered 2±4% of the anterior articular area in immobilized knees versus 28±12% contralaterally (p=0.003) and 26±7% in sham (p=0.043). Mankin scores in immobilized knees were 4.7±1.7 versus 0.2±0.4 and 0±0 for contralateral and sham (p=0.003, p=0.042), respectively. The trabecular bone plate area of anterior and posterior regions showed relative loss of cross-sectional area in immobilized knees compared to controls (immobilized/contralateral area ratios of 0.67 and 0.46 respectively, both p=0.003), while the area in the middle region was preserved. Movat's pentachrome stain and CD31 staining showed chondral vascular ingrowth from subchondral bone. Osteocalcin and CD90 MSC staining were decreased in immobilized knees versus contralateral (p=0.003, p=0.036 respectively).

CONCLUSIONS

Bony replacement characterizes articular cartilage degeneration of knees immobilized for 32weeks in the anterior, non-weight bearing region of the tibia. Replacement of cartilage by bone may have been mediated by chondral vascularization, suggesting irreversible changes. These findings stress the importance of weight-bearing and joint motion to maintain cartilage structure.

Immunophenotype of skin lymphocytic infiltrate in patients co-infected with Mycobacterium leprae and human immunodeficiency virus: a scenario dependent on CD8+ and/or CD20+ cells

BACKGROUND

Leprosy occurs rarely in human immunodeficiency virus (HIV)-positive patients. In contrast to tuberculosis, there has been no report to date of an increase in HIV prevalence among patients with leprosy or of differences in leprosy's clinical spectrum. While several studies describe the systemic immune response profile in patients co-infected with HIV and leprosy, the local immune skin response has been evaluated in only a small number of case reports and limited series of patients.

OBJECTIVE

To investigate the interaction between Mycobacterium leprae and HIV infection in the skin.

METHODS

We investigated the presence and frequency of cells positive for CD4, CD8, CD20, TIA-1, FOXP3 and CD123 in lymphocytic infiltrates from 16 skin biopsies taken from 15 patients with HIV-leprosy co-infection.

RESULTS

CD4+ cells were absent in infiltrates from 6 (38%) skin biopsies and present in 10 (62%) cases at low levels (<1·16%) of the lymphocytic infiltrate. CD8+ was the predominant phenotype in the infiltrate (99·4%), followed by TIA-1, expressed by >75% of CD8+ cells. FOXP3+ cells were also present, representing 3·4% of the lymphocytic infiltrate. CD20+ cells were detected in 75% of the cases; however, in two cases (12%) these cells represented 25-50% of the infiltrate, while in the other 10 cases (62%) they were present only focally (<25% of the infiltrate). CD123+ cells were not observed in any of the studied specimens.

CONCLUSIONS

Data presented here suggest that cell-mediated immune responses to M. leprae are preserved at the site of disease and that in the absence of CD4+ cells, CD8+FOXP3+ and CD20+ cells may be involved in granuloma formation.

Imported leprosy in Italy

BACKGROUND

Leprosy is far from being eliminated with more than 200,000 new cases detected (NCD)/year.

OBJECTIVE

Retrospective analysis between 2003 and 2009 to compare the New Case Detected Rate (NCDR) observed in Italy in the immigrant population with the NCDR of the same population in their country of origin to verify if the cases observed are those expected or not.

METHODS

Leprosy statistics were retrieved from the Italian leprosy register and from official WHO data.

RESULTS

The NCD in Italy were lower than expected, from 2003 when the expected number of NCD was 40.5 between the legally resident immigrants, but only one case was diagnosed (98% of lower from the expected), to 2009 when four NCD were diagnosed and 41 were expected (90% lower from expected).

CONCLUSIONS

This study points out a discrepancy between the observed and the expected cases of leprosy in Italy. Specifically, the number of NCD was less than expected for each studied year. Of course our data do not represent a validation, but only an indication of the leprosy diagnosis in Italy. Difficulty in accessing the health systems, fear of segregation, ignorance and illegal immigrant status with consequent fear of police arrest are possible explaining factors. The critical issue anyhow is the medical expertise. The role of the dermatologist is fundamental. For these reasons, there is still a need for wide spread leprosy teaching programmes. Although with few limitations, this study represents a first approach to validate the accuracy in leprosy diagnosis in Italy.

Establishment of a model of cortical bone repair in mice

A model of cortical bone repair has been established for use in mice. The cortical defect consisted of a hole drilled through the entire diameter of the tibial diaphysis. The hematoma that initially filled the drill site was invaded by cells of mesenchymal appearance within 5 days of injury. Trabeculae of mineralized woven bone were present throughout the drill site by day 9. A reaction in the periosteum adjacent to the drill site, consisting of both new bone and cartilage formation, preceded deposition of bone tissue in the drill site. New woven bone was modeled to restore the marrow cavity to normal by 4 weeks after injury, and almost normal cortical structure was achieved by 6 weeks after injury. Immunohistochemical studies indicated that type III collagen was expressed within the drill site by day 5, reached a peak at day 7, and was diminished by day 9. In contrast, type I collagen was first detectable in the drill site at day 7, and staining was more intense by day 9. Osteopontin expression in the drill site coincided with the process of mineralization of new bone in this location. The model of bone repair described here provides a method for inducing reproducible bone lesions in a readily identifiable location in mice. It will be useful in the investigation of bone cell function in mouse strains that have been subjected to genetic manipulation.

Rat middle cerebral artery occlusion: Correlations between histopathology, T2-weighted magnetic resonance imaging, and behavioral indices

During attempts to develop the intraluminal suture model of transient middle cerebral artery occlusion (MCAO) in the Sprague Dawley strain of rats, we noticed a wide variability in lesion size seen with T2-weighed magnetic resonance imaging (MRI) or histopathology, as well as in scores for behavioral indices. It was our intent to examine the results of the study carefully and determine whether there were strong point-to-point correlations between the degree of lesion size determined from T2-weighted MRI or histopathology and intermediate or long-term neurologic/behavioral assessments. Baseline behavioral scores for forelimb dexterity (staircase test) were obtained on all animals in the period before receiving 60 minutes of transient MCAO. After MCAO, animals were tested at specified intervals from 1 to 21 days for composite neurologic deficits. T2-weighted MRI was taken at 2 and 7 days post-MCAO. At 30 and 60 days post-MCAO, animals were retested in the staircase test with subsequent histopathologic examination of the brains. Indeed, there were highly significant correlations between lesion size determined by MRI and histopathology. The damage observed in the T2-weighted MRI, as well as the size of the histopathologic lesions, were in turn highly correlated to deficiencies observed in the composite neurologic assessments, as well as to deficits at 30 and 60 days post-MCAO for skilled use of the contralateral forepaw (damaged side). In the latter test, the correlations were somewhat less significant for the ability of rats to reach for food with the ipsilateral forepaw (undamaged side).

Effect of fucoidan treatment on collagenase-induced intracerebral hemorrhage in rats

Inflammatory cells are postulated to mediate some of the brain damage following ischemic stroke. Intracerebral hemorrhage is associated with more inflammation than ischemic stroke. We tested the sulfated polysaccharide fucoidan, which has been reported to reduce inflammatory brain damage, in a rat model of intracerebral hemorrhage induced by injection of bacterial collagenase into the caudate nucleus. Rats were treated with seven day intravenous infusion of fucoidan (30 micrograms h-1) or vehicle. The hematoma was assessed in vivo by magnetic resonance imaging. Motor behavior, passive avoidance, and skilled forelimb function were tested repeatedly for six weeks. Fucoidan-treated rats exhibited evidence of impaired blood clotting and hemodilution, had larger hematomas, and tended to have less inflammation in the vicinity of the hematoma after three days. They showed significantly more rapid improvement of motor function in the first week following hemorrhage and better memory retention in the passive avoidance test. Acute white matter edema and eventual neuronal loss in the striatum adjacent to the hematoma did not differ between the two groups. Investigation of more specific anti-inflammatory agents and hemodiluting agents are warranted in intracerebral hemorrhage.

-(S)-Alpha-phenyl-2-pyridine-ethanamine Dihydrochloride-, a low affinity uncompetitive N-methyl-D-aspartic acid antagonist, is effective in rodent models of global and focal ischemia

[(S)-Alpha-phenyl-2-pyridine-ethanamine dihydrochloride] (ARL 15896AR) is a low affinity uncompetitive N-methyl-D-aspartic acid receptor antagonist that was tested in animal models of anoxia and ischemia. Pretreatment of rodents with ARL 15896AR extended survival time during exposure to hypoxia. With the rat four-vessel occlusion model of global ischemia (20 min), oral dosing commencing at reflow, resulted in significant protection of the CA1 hippocampal neurons. ARL 15896AR was, however, ineffective in the rat two-vessel occlusion model and in the gerbil models of forebrain ischemia, the latter due to an inability to attain suitable plasma levels. In the spontaneously hypertensive rat model of middle cerebral artery occlusion (MCAO) (2 hr plus 22 hr reflow), acute dosing with ARL 15896AR (i.p.) beginning from 30 min before or up to 1 hr post-MCAO significantly reduced cortical infarct volume. The ability of ARL 15896AR to influence infarct size, as well as functional correlates was examined in SHR after 90 min of MCAO. T2 weighted magnetic resonance images taken at 2 and 6 days post-MCAO revealed significantly smaller lesion sizes in the group receiving injections with ARL 15896AR beginning 30 min after occlusion. Spontaneously hypertensive rats were subsequently tested (30-42 days post-MCAO) and found to be deficient in skilled use of the forepaws (staircase test). The contralateral forepaw was most severely impaired, however, ARL 15896AR treatment prevented motor impairment in only the ipsilateral forepaw. Histopathological examination of cortical infarct size was unremarkable between treated and control rats. The findings indicate that ARL 15896AR exhibits neuroprotection in global and focal models of ischemia

A vinyl polysiloxane die used to make interim restorations

A die made of vinyl polysiloxane is a great aid for making interim restorations and for establishing correct gingival contours for finer restorations. This article describes the rationale and procedures for such a procedure.

Nodular pulmonary amyloidosis

An elderly man had a 10-year history of multiple pulmonary nodules that he had refused to have investigated. He died of a ruptured abdominal aortic aneurysm. At autopsy the nodules were shown to consist of amyloid. There was no evidence of systemic amyloidosis.

Attempted reconstitution of a foal with primary severe combined immunodeficiency

A foal with primary severe combined immunodeficiency, diagnosed within the first two weeks of life, was maintained with its dam in semi-isolation. The foal received continuous prophylactic antibiotic therapy, plasma from a sibling hyperimmunised with equine adenovirus vaccine, and intensive general nursing care. A full sibling female was selected as a bone marrow donor on the basis of red blood cell cross-matching and mixed lymphocyte reactions. Cyclophosphamide was given before two bone marrow transfusions at 35 and 73 days of age. To prevent graft versus host disease graft versus host disease the foal was maintained on methotrexate therapy. Reconstitution was not achieved nor were there signs of graft versus host disease. The foal died suddenly four days after the second bone marrow transfer when 77 days old. It had remained clinically free of any life threatening infectious disease and at necropsy a remarkable degree of freedom from infectious disease was confirmed. The most notable necropsy findings were bilateral nephrosis and myocardial degeneration and fibrosis. The likely cause of death was an electrolyte imbalance, particularly hypokalaemia, which secondarily affected the myocardium. Renal toxicity caused by the cytotoxic drugs, especially cyclophosphamide, may have contributed to the electrolyte imbalance.

Reconstitution of primary, severe, combined immunodeficiency in man and horse

Severe combined immunodeficiency disease (SCID) in foals is the only known animal model for the autosomal recessive form of primary SCID in man. A major requirement in the treatment of SCID is the maintenance of the patient in a disease free state until definitive therapy can be undertaken. This paper reviews the current status of prophylactic and definitive therapy in man and the horse. Particular emphasis is placed on the methods of reconstitution available, involving foetal tissues and bone marrow.

Immunogenicity of equine herpesvirus type 1 (EHV1) and equine rhinovirus type 1 (ERhV1) following inactivation by betapropiolactone (BPL) and ultraviolet (UV) light

Some kinetic data on the inactivation of equine herpesvirus type 1 (EHV1) and equine rhinovirus type 1 (ERhV1) by betapropiolactone (BPL) and ultraviolet (UV) irradiation are reported. 0.25% BPL at 37 degrees C for 1 h reduced the titre of EHV1 by greater than 10(3 . 4) and of ERhV1 by greater than 10(4 . 1) TCID50/ml. UV irradiation (334 microW/cm2) produced similar reductions in titre after 2 min. These data were used as a basis for inactivating EHV1 and ERhV1 by the combined action of BPL and UV irradiation. Viruses were exposed to 0.1% BPL for 1 h at 4 degrees C with constant stirring, followed by UV irradiation for 2 min, followed by incubation for 3 h at 37 degrees C. Inactivated EHV1 elicited secondary immune responses only in horses whereas ERhV1 produced primary immune responses in mice (including athymic nu/nu mice), rabbits and probably in horses.

In vitro blastogenesis of equine lymphocytes by inactivated equine adenovirus type 1 antigen

An inactivated equine adenovirus type 1 (EAdV1) vaccine was administered to 4 horses. The horses had virus-neutralizing (VN) antibody titers before they were vaccinated, but developed higher VN antibody titers in response to vaccination. Nonvaccinated control horses did not show increases in VN antibody during the study, indicating that any increase in antibody titer in vaccinated horses was a result of vaccination and not due to an EAdV1 epizootic during the study. Specific EAdV1 in vitro lymphocyte blastogenesis (LB) was evaluated, using lymphocytes from 4 vaccinated and 2 control horses. Horses were vaccinated on days 0 and 14, and the LB assays were conducted on days -4, 0, 3, 7, 10, 14, 17, 21, 24, and 28. Lymphocytes from horses were incubated for 4 days with 2 concentrations of inactivated, concentrated and purified EAdV1 antigen. The LB responses for the 2 control horses showed no significant changes during the study period (maximum stimulation indices to EAdV1 antigen for individual horses were between 2.8 and 3.6). The 4 vaccinated horses showed marked increases in stimulation indices in response to EAdV1 antigen (maximum stimulation indices, between 5.3 and 18.6). In control assays, identical lymphocyte preparations from all horses responded normally to phytohemagglutinin.