Respiratory syncytial virus nephropathy in rats

The expression of respiratory tract virus in pediatric glomerular disease: a retrospective study of 45 renal biopsy in China

BACKGROUND

More attention has been put on the relationship between pediatric glomerular disease and respiratory tract virus infection. Children with glomerular illness, however, are uncommonly found to have biopsy-proven pathological evidence of viral infection. The purpose of this study is to determine whether and what kind of respiratory viruses are found in renal biopsy from glomerular disorders.

METHODS

We used a multiplex PCR to identify a wide range of respiratory tract viruses in the renal biopsy samples (n = 45) from children with glomerular disorders and a specific PCR to verify their expression.

RESULTS

These case series included 45 of 47 renal biopsy specimens, with 37.8% of male and 62.2% of female patients. Indications for a kidney biopsy were present in all of the individuals. In 80% of the samples, respiratory syncytial virus was discovered. Following that, the RSV subtypes in several pediatric renal disorders were found. There were 16 RSVA positives, 5 RSVB positives, and 15 RSVA/B positives, accounting for 44.4%, 13.9%, and 41.7%, respectively. Nephrotic syndrome samples made up 62.5% of RSVA positive specimens. The RSVA/B-positive was detected in all pathological histological types.

CONCLUSIONS

Patients with glomerular disease exhibit respiratory tract viral expression in the renal tissues, especially respiratory syncytial virus. This research offers new information on the detection of respiratory tract viruses in renal tissue, which may facilitate the identification and treatment of pediatric glomerular diseases.

Respiratory Syncytial Virus Exacerbates Kidney Damages in IgA Nephropathy Mice via the C5a-C5aR1 Axis Orchestrating Th17 Cell Responses

Respiratory viral infections can directly lead to kidney damage such as IgA nephropathy (IgAN), partly due to mucosal immune system dysfunction. Although the activated C5a-C5aR1 axis results in increased Th1 and Th17 frequencies but reduced Treg frequencies in Respiratory syncytial virus (RSV) infection, how this axis affects Th cell disorders in RSV-induced IgAN exacerbation remains unknown. Here, we used a mouse model to dissect the activation of C5a-C5aR1 by RSV and the consequences on the regulation of Th1, Th17, and Treg immune responses in IgA nephropathy. RSV fusion protein was clearly deposited not only in the pulmonary interstitium but also in the glomerulus in RSV-IgAN mice, and RSV infection led to more severe pathological changes in the kidneys in IgAN mice. Blocking the C5a-C5aR1 axis resulted in a decrease in the albumin-to-creatinine ratio, and the attenuation of kidney damage in IgAN and RSV-IgAN mice might be partly attributed to the inhibition of Th cell and cytokine dysfunction. Th1, Th17 and Treg immune responses and their corelative cytokines were disrupted by RSV infection and rescued by C5aR1 inhibition. Moreover, we constructed a coculture system of human mesangial cells and CD4⁺ T cells and found that RSV infection might lead to CD4⁺ T cell production via human mesangial cells-enhanced CD4⁺ T cell proliferation, consequently increasing IL-17 levels. These pathological behaviors were augmented by C5a stimulation and decreased by C5aR1 inhibition. Thus, C5aR1 inhibition alters both kidney damage and Th1, Th17, and Treg cell dysfunction in RSV-induced IgAN exacerbation and locally regulates HMC antigen presentation function in the kidney. Taken together, our data offer profound evidence that blocking the C5a-C5aR1 axis might be a potential therapy for RSV-induced IgAN.

Low molecular weight heparin may benefit nephrotic remission in steroid‑sensitive nephrotic syndrome via inhibiting elastase

Low molecular weight heparin (LMWH) has a structure similar to heparan sulfate, which exerts anti-inflammatory effects via inhibiting elastase (Ela) activity. Release of Ela along the glomerular capillary wall may induce glomerular injury and proteinuria. The present study aimed to investigate the influence of LMWH on steroid-sensitive nephrotic syndrome (SSNS) and the potential underlying mechanism. A total of 40 SSNS patients and 20 healthy controls were recruited. SSNS patients were treated with LMWH and prednisone simultaneously (LMWH+pred group) or with prednisone alone (pred group). Proteinuria, urinary glycosaminoglycans (GAGs), serum Ela and urinary creatinine levels were measured. The nephrotic period of SSNS was 15.93±5.78 days. The nephrotic period of SSNS in LMWH+pred group was significantly reduced compared with the pred group (14.13±4.56 vs. 18.63±6.49 days; P<0.05). At the follow-up of the SSNS patients, there was no statistically significant difference in number of relapses between the LMWH+pred and pred groups. Proteinuria (2.51±0.97 g/24 h), urinary GAG levels (4.92±0.87 mg/mmol creatinine) and serum Ela levels (77.64±10.99 ng/l) were significantly greater in the nephrotic period of SSNS compared with the remission period (0.107±0.026 g/24 h, 1.53±0.27 mg/mmol Cr and 41.92±7.81 ng/l, respectively) and the healthy control group (0.098±0.027 g/24 h, 1.40±0.26 mg/mmol creatinine and 38.43±9.83 ng/l, respectively; P<0.05). During the remission period, urinary GAG and serum Ela levels in the LMWH+pred group were significantly reduced compared with the pred group (P<0.05), whereas proteinuria did not differ between these groups (P>0.05). Positive correlations were revealed between urinary GAG excretion and proteinuria (r=0.877; P<0.05), proteinuria and serum Ela levels (r=0.844; P<0.05) and serum Ela levels and urinary GAG excretion (r=0.881; P<0.05). The results of the present study indicated that elevated serum Ela levels may induce proteinuria by degrading GAGs in the glomerular basement membrane in children with SSNS. LMWH may benefit nephrotic remission of SSNS via inhibiting Ela.

Respiratory Syncytial Virus Aggravates Renal Injury through Cytokines and Direct Renal Injury

The purpose of this study was to investigate the relationship between renal injury and reinfection that is caused by respiratory syncytial virus (RSV) and to analyze the mechanism of renal injury. Rats were repeatedly infected with RSV on days 4, 8, 14, and 28, then sacrificed and examined on day 56 after the primary infection. Renal injury was examined by transmission electron microscopy and histopathology. The F protein of RSV was detected in the renal tissue by indirect immunofluorescence. Proteinuria and urinary glycosaminoglycans (GAGs), serum levels of albumin, urea nitrogen, and creatinine, secretion of cytokines, T lymphocyte population and subsets, and dendritic cell (DC) activation state were examined. The results showed that renal injury was more serious in the reinfection group than in the primary infection group. At a higher infection dose, 6 × 10⁶ PFU, the renal injury was more severe, accompanied by higher levels of proteinuria and urinary GAGs excretion, and lower levels of serum albumin. Podocyte foot effacement was more extensive, and hyperplasia of mesangial cells and proliferation of mesangial matrix were observed. The maturation state of DCs was specific, compared with the primary infection. There was also a decrease in the ratio of CD4⁺ to CD8⁺ T lymphocytes, due to an increase in the percentage of CD8⁺ T lymphocytes and a decrease in the percentage of CD4⁺ T lymphocytes, and a dramatic increase in the levels of IL-6 and IL-17. In terms of the different reinfection times, the day 14 reinfection group yielded the most serious renal injury and the most significant change in immune function. RSV F protein was still expressed in the glomeruli 56 days after RSV infection. Altogether, these results reveal that RSV infection could aggravate renal injury, which might be due to direct renal injury caused by RSV and the inflammatory lesions caused by the anti-virus response induced by RSV.

Human Respiratory Syncytial Virus: Infection and Pathology

The human respiratory syncytial virus (hRSV) is by far the major cause of acute lower respiratory tract infections (ALRTIs) worldwide in infants and children younger than 2 years. The overwhelming number of hospitalizations due to hRSV-induced ALRTI each year is due, at least in part, to the lack of licensed vaccines against this virus. Thus, hRSV infection is considered a major public health problem and economic burden in most countries. The lung pathology developed in hRSV-infected individuals is characterized by an exacerbated proinflammatory and unbalanced Th2-type immune response. In addition to the adverse effects in airway tissues, hRSV infection can also cause neurologic manifestations in the host, such as seizures and encephalopathy. Although the origins of these extrapulmonary symptoms remain unclear, studies with patients suffering from neurological alterations suggest an involvement of the inflammatory response against hRSV. Furthermore, hRSV has evolved numerous mechanisms to modulate and evade the immune response in the host. Several studies have focused on elucidating the interactions between hRSV virulence factors and the host immune system, to rationally design new vaccines and therapies against this virus. Here, we discuss about the infection, pathology, and immune response triggered by hRSV in the host.

[Acute tubulointerstitial nephritis following adenovirus and respiratory syncytial virus infection]

Acute tubulointerstitial nephritis (TIN) is responsible for nearly 10% of acute renal failure (ARF) cases in children. It is mostly drug-induced, but in a few cases viruses are involved, probably by an indirect mechanism. An immune-competent 13-month-old boy was admitted to the intensive care unit for severe ARF with anuria in a context of fever, cough, and rhinorrhea lasting 1 week. The kidney biopsy performed early brought out tubulointerstitial damage with mild infiltrate of lymphocytes, without any signs of necrosis. There were no virus inclusion bodies, no interstitial hemorrhage, and no glomerular or vascular damage. Other causes of TIN were excluded: there was no biological argument for an immunological, immune, or drug-induced cause. Adenovirus (ADV) and respiratory syncytial virus (RSV) were positive in respiratory multiplex polymerase chain reaction (PCR) in nasal aspirate but not in blood, urine, and renal tissue. The patient underwent dialysis for 10 days but the response to corticosteroid therapy was quickly observed within 48 h. The mechanism of TIN associated with virus infection is unknown. However, it may be immune-mediated to be able to link severe renal dysfunction and ADV and/or RSV invasion of the respiratory tract.

A novel respiratory syncytial virus (RSV) F subunit vaccine adjuvanted with GLA-SE elicits robust protective TH1-type humoral and cellular immunity in rodent models

Background

Illness associated with Respiratory Syncytial Virus (RSV) remains an unmet medical need in both full-term infants and older adults. The fusion glycoprotein (F) of RSV, which plays a key role in RSV infection and is a target of neutralizing antibodies, is an attractive vaccine target for inducing RSV-specific immunity.

Methodology and Principal Findings

BALB/c mice and cotton rats, two well-characterized rodent models of RSV infection, were used to evaluate the immunogenicity of intramuscularly administered RSV vaccine candidates consisting of purified soluble F (sF) protein formulated with TLR4 agonist glucopyranosyl lipid A (GLA), stable emulsion (SE), GLA-SE, or alum adjuvants. Protection from RSV challenge, serum RSV neutralizing responses, and anti-F IgG responses were induced by all of the tested adjuvanted RSV sF vaccine formulations. However, only RSV sF + GLA-SE induced robust F-specific T_H1-biased humoral and cellular responses. In mice, these F-specific cellular responses include both CD4 and CD8 T cells, with F-specific polyfunctional CD8 T cells that traffic to the mouse lung following RSV challenge. This RSV sF + GLA-SE vaccine formulation can also induce robust RSV neutralizing titers and prime IFNγ-producing T cell responses in Sprague Dawley rats.

Conclusions/Significance

These studies indicate that a protein subunit vaccine consisting of RSV sF + GLA-SE can induce robust neutralizing antibody and T cell responses to RSV, enhancing viral clearance via a T_H1 immune-mediated mechanism. This vaccine may benefit older populations at risk for RSV disease.

Prevalence of herpesviruses at onset of idiopathic nephrotic syndrome

BACKGROUND

Idiopathic nephrotic syndrome (INS) is likely a primary immune disorder, but viruses might also be involved in the mechanisms of the disease. Here, we investigate the link between herpesvirus infection and the first manifestation of INS in children.

METHODS

A prospective, multicentre, and population-based case-control study called NEPHROVIR included 164 patients, aged 6 months to 15 years old, newly diagnosed with INS, and 233 controls matched for gender, age, and period of sample. The analysis was done on 124 patients and 196 controls. Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpesvirus-6 (HHV-6), and human herpesvirus-7 (HHV-7) DNA prevalence at diagnosis were assessed from whole peripheral blood samples, as well as EBV and CMV viral load and seroprevalence.

RESULTS

EBV DNA was significantly more prevalent in cases than in controls (50.8 vs 29.1 %; OR = 2.6; p = 0.0002), with no difference in viral load. A significant difference was also found for CMV (11.3 vs 3.6 %; p = 0.02) and HHV-7 (83 vs 72 %; p = 0.02) DNA prevalence between cases and controls. There were significantly more EBV and CMV recent infections or reactivations based on VCA-IgM and CMV IgM in cases than controls, while there were no differences in IgG seroprevalence.

CONCLUSION

The prevalence of positive EBV DNA detection and recent infection or reactivation is higher in children at onset of INS compared to a population matched for age, gender, and time of sampling.

Respiratory syncytial virus and asthma: speed-dating or long-term relationship?

PURPOSE OF REVIEW

Respiratory syncytial virus (RSV) is the most common respiratory pathogen in infants and young children worldwide. Furthermore, epidemiological evidence has been accumulating that RSV lower respiratory tract infection in infants may be linked to subsequent development of recurrent wheezing and asthma in childhood. This article reviews the epidemiological evidence linking RSV and asthma and some new hypotheses of the cellular and molecular mechanisms of postviral airway inflammation and hyperreactivity that have been proposed to explain the epidemiological link.

RECENT FINDINGS

New epidemiological studies have suggested that viral pathogens other than RSV, especially human rhinoviruses (HRV), may play an important role in the inception of atopic asthma. Also, recent experimental evidence is challenging the widely accepted axiom that RSV is cleared from immunocompetent hosts within weeks from the onset of the infection. In particular, bone marrow stromal cells may be a frequent target of human RSV infection, develop structural and functional changes when infected, participate actively in the pathogenesis of the acute disease, and harbor the virus chronically, allowing persistence of the infection.

SUMMARY

RSV - and possibly other common respiratory pathogens - play an important role not only in the exacerbation, but also in the inception of asthma. The latter effect may involve the persistence of latent virus in extrapulmonary tissues, similar to what has been recently found for some bacterial species. The most immediate consequence of these discoveries is that future prophylactic and therapeutic strategies for common infections caused by viral or bacterial pathogens may have to address the coverage of remote sites of latent persistence or replication, in order to avoid chronic sequelae-recurrent wheezing and asthma.

Impaired learning resulting from respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the major cause of respiratory illness in infants worldwide. Neurologic alterations, such as seizures and ataxia, have been associated with RSV infection. We demonstrate the presence of RSV proteins and RNA in zones of the brain--such as the hippocampus, ventromedial hypothalamic nucleus, and brainstem--of infected mice. One month after disease resolution, rodents showed behavioral and cognitive impairment in marble burying (MB) and Morris water maze (MWM) tests. Our data indicate that the learning impairment caused by RSV is a result of a deficient induction of long-term potentiation in the hippocampus of infected animals. In addition, immunization with recombinant bacillus Calmette-Guérin (BCG) expressing RSV nucleoprotein prevented behavioral disorders, corroborating the specific effect of RSV infection over the central nervous system. Our findings provide evidence that RSV can spread from the airways to the central nervous system and cause functional alterations to the brain, both of which can be prevented by proper immunization against RSV.

Vertical transmission of respiratory syncytial virus modulates pre- and postnatal innervation and reactivity of rat airways

Background

Environmental exposure to respiratory syncytial virus (RSV) is a leading cause of respiratory infections in infants, but it remains unknown whether this infection is transmitted transplacentally from the lungs of infected mothers to the offspring. We sought to test the hypothesis that RSV travels from the respiratory tract during pregnancy, crosses the placenta to the fetus, persists in the lung tissues of the offspring, and modulates pre- and postnatal expression of growth factors, thereby predisposing to airway hyperreactivity.

Methodology

Pregnant rats were inoculated intratracheally at midterm using recombinant RSV expressing red fluorescent protein (RFP). Viral RNA was amplified by RT-PCR and confirmed by sequencing. RFP expression was analyzed by flow cytometry and viral culture. Developmental and pathophysiologic implications of prenatal infection were determined by analyzing the expression of genes encoding critical growth factors, particularly neurotrophic factors and receptors. We also measured the expression of key neurotransmitters and postnatal bronchial reactivity in vertically infected lungs, and assessed their dependence on neurotrophic signaling using selective biological or chemical inhibition.

Principal Findings

RSV genome was found in 30% of fetuses, as well as in the lungs of 40% of newborns and 25% of adults. RFP expression was also shown by flow cytometry and replicating virus was cultured from exposed fetuses. Nerve growth factor and its TrkA receptor were upregulated in RSV- infected fetal lungs and co-localized with increased cholinergic innervation. Acetylcholine expression and smooth muscle response to cholinergic stimulation increased in lungs exposed to RSV in utero and reinfected after birth, and blocking TrkA signaling inhibited both effects.

Conclusions/Significance

Our data show transplacental transmission of RSV from mother to offspring and persistence of vertically transmitted virus in lungs after birth. Exposure to RSV in utero is followed by dysregulation of neurotrophic pathways predisposing to postnatal airway hyperreactivity upon reinfection with the virus.

Respiratory syncytial virus infection in human bone marrow stromal cells

Respiratory syncytial virus (RSV) is the most common respiratory pathogen in infants and young children. The pathophysiology of this infection in the respiratory system has been studied extensively, but little is known about its consequences in other systems. We studied whether RSV infects human bone marrow stromal cells (BMSCs) in vitro and in vivo, and investigated whether and how this infection affects BMSC structure and hematopoietic support function. Primary human BMSCs were infected in vitro with recombinant RSV expressing green fluorescent protein. In addition, RNA from naive BMSCs was amplified by PCR, and the products were sequenced to confirm homology with the RSV genome. The BMSC cytoskeleton was visualized by immunostaining for actin. Finally, we analyzed infected BMSCs for the expression of multiple cytokines and chemokines, evaluated their hematopoietic support capacity, and measured their chemotactic activity for both lymphoid and myeloid cells. We found that BMSCs support RSV replication in vitro with efficiency that varies among cell lines derived from different donors; furthermore, RNA sequences homologous to the RSV genome were found in naive primary human BMSCs. RSV infection disrupted cytoskeletal actin microfilaments, altered cytokine/chemokine expression patterns, decreased the ability of BMSCs to support B cell maturation, and modulated local chemotaxis. Our data indicate that RSV infects human BMSCs in vitro, and this infection has important structural and functional consequences that might affect hematopoietic and immune functions. Furthermore, we have amplified viral RNA from naive primary BMSCs, suggesting that in vivo these cells provide RSV with an extrapulmonary target.

Ability of low-molecular-weight heparin to alleviate proteinuria by inhibiting respiratory syncytial virus infection

AIM

Low-molecular-weight heparin (LMWH) is a negatively charged glycoprotein and has a very similar structure to that of cell surface heparin sulfate (HS). Thus, LMWH, an analog of HS, may inhibit positively charged respiratory syncytial virus (RSV) infection through cooperative electrostatic association.

METHODS

In this study, rats were respectively treated with 400 IU/kg LMWH before, during or after being inoculated with 6 x 10(6) plaque-forming unit (PFU) RSV. RSV and normal control groups were respectively inoculated by RSV and virus-free Dulbecco's modified Eagle's medium (DMEM). HeLa cells in vitro were pretreated with LMWH, elastase (ELA), heparinase (HpaIII) and protamine before being inoculated with 6 x 10(1) PFU RSV. RSV infectivity was determined by in situ hybridization and plaque assay.

RESULTS

After inoculation, the urinary protein excretion and serum parameters in LMWH-treated rats were significantly lower than those in the RSV group. No abnormalities of glomerular structure were observed in LMWH-treated groups whereas swelling and slight hypercellularity in minority glomeruli and foot process effacement were observed in the RSV group. RSV RNA of LMWH-treated rats had weaker expression than that of the RSV group. In vitro, RSV infection in RSV + LMWH, HpaIII + ELAI, protamine + ELAI, ELAI, HpaIII and protamine treatment cells were significantly lower than that of the RSV control, and that in RSV + LMWH was the least. There were no significant differences in RSV infection between ELAI + LMWH and RSV control.

CONCLUSION

Our study confirmed that there is a correlation between RSV and proteinuria in rats. LMWH can alleviate proteinuria in rats through inhibiting RSV from binding with HS which plays an important role in the onset of RSV infection.