Impact of human metapneumovirus and human cytomegalovirus versus other respiratory viruses on the lower respiratory tract infections of lung transplant recipients

Human Cytomegalovirus (HCMV) - specific T-cell response after letermovir prophylaxis is predictive for subsequent HCMV reactivation in haematopoietic stem cell transplant recipients

BACKGROUND

Human Cytomegalovirus (HCMV) is still one of the major concerning infection in hematopoietic stem cell transplant (HSCT) recipients. Letermovir (LTV) has been recently introduced for HCMV prophylaxis in adult patients who received allogeneic HSCT. However, many aspects related to immune reconstitution need to be further explored. The aim of this study was to define the prognostic role of HCMV-specific T-cell frequency measured at the end of LTV prophylaxis in predicting the risk for clinically significant HCMV infection (i.e. infection requiring antiviral treatment) after the stop of the prophylaxis.

METHODS

Sixty-six adult patients who underwent allogeneic HSCT were enrolled and HCMV DNAemia was prospectively monitored. Additionally, HCMV-specific T-cell response was evaluated using ELISpot assay against two different antigens (HCMV infected cell lysate and pp65 peptide pool).

RESULTS

Ten patients (15.2%) developed at least one positive HCMV DNAemia episode during LTV prophylaxis, whereas 50/66 (75.8%) patients developed at least one positive HCMV DNA event after LTV prophylaxis. Of note, 25 of them (50%) experienced a clinically significant HCMV infection. The median HCMV-specific T-cell response measured against HCMV lysate but not against pp65 peptide pool was lower in patients who developed HCMV clinically significant infection after prophylaxis. A ROC analysis revealed that the level of 0.04 HCMV-specific T cells/µl should be used as cut-off for development of clinically significant HCMV reactivation after prophylaxis.

CONCLUSION

Assessment of HCMV-specific immunity upon discontinuation of universal prophylaxis with LTV should be considered as a method for identification of patients at risk for clinically significant HCMV infection.

Human cytomegalovirus-specific T-cell reconstitution and late-onset cytomegalovirus infection in hematopoietic stem cell transplant recipients following letermovir prophylaxis

BACKGROUND

Letermovir (LTV), recently approved for the prophylaxis of human Citomegalovirus (HCMV) reactivation after hematopoietic stem cell transplantation (HSCT), has decreased the rate of infection in the first months post-transplant.

OBJECTIVE

The aim of this study was to evaluate the impact of LTV prophylaxis on immune reconstitution and late-onset infection.

STUDY DESIGN

We studied HCMV infection and HCMV-specific T-cell reconstitution in two matched groups of HSCT recipients receiving LTV prophylaxis (N=30, LTV group) vs pre-emptive therapy (N=31, PET group). Rate of GvHD, neutropenia, baseline disease recurrence and overall survival were analyzed.

RESULTS

Clinically significant infections requiring pre-emptive therapy showed a similar rate in the PET (21/31, 68%) vs the LTV group (17/30, 57%; P=0.434), but occurred significantly later (after prophylaxis discontinuation) in the LTV group. No difference was found in peak HCMV DNAemia levels (P=0.232). HCMV-specific T-cell recovery was delayed by about 100 days in the LTV group. HCMV-specific CD4 and CD8 T cells were significantly lower in the LTV group between days 120-360 and 90-120, respectively. A lower rate of chronic GvHD (P=0.024) was found in the LTV-group. Time to engraftment, rate of disease relapse and one-year survival were not different in the two groups, whereas a trend towards a lower occurrence of neutropenia (P=0.124) and higher occurrence of acute GvHD grade III-IV (P=0.103) was observed in the LTV group.

CONCLUSIONS

LTV prophylaxis delays HCMV infection and HCMV-specific immune reconstitution, therefore immunological and virological monitoring should be implemented post-prophylaxis discontinuation. The potential effect of LTV prophylaxis in reducing chronic GvHD should be evaluated by prospective studies.

Impact of COVID-19 on Lung Allograft and Clinical Outcomes in Lung Transplant Recipients: A Case-control Study

BACKGROUND

The impacts of COVID-19 on lung allograft function, rejection, secondary infection, and clinical outcomes in lung transplant recipients (LTRs) remain unknown.

METHODS

A 1:2 matched case-control study was performed to evaluate rehospitalization, lung allograft function, and secondary infections up to 90 d after COVID-19 diagnosis (or index dates for controls).

RESULTS

Twenty-four LTRs with COVID-19 (cases) and 48 controls were identified. Cases and controls had similar baseline characteristics and lung allograft function. LTRs with COVID-19 had higher incidence of secondary bacterial infection (29.2% versus 6.3%, P = 0.008), readmission (29.2% versus 10.4%, P = 0.04), and for-cause bronchoscopy (33.3% versus 12.5%, P = 0.04) compared with controls. At d 90, mortality in cases versus controls was 8.3% versus 2.1% (P = 0.21), incidence of invasive fungal infections in cases versus controls was 20.8% versus 8.3% (P = 0.13) and forced expiratory volume in 1 s (FEV1) decline ≥10% from baseline occurred in 19% of cases versus 12.2% of controls (P = 0.46). No acute cellular rejection, acute antibody-mediated rejection, or new donor-specific anti-HLA antibodies were observed among cases or controls within 90 d post index date.

CONCLUSIONS

We found LTRs with COVID-19 were at risk to develop secondary infections and rehospitalization post COVID-19, compared with controls. While we did not observe post viral acute cellular rejection or antibody-mediated rejection, further studies are needed to understand if LTRs with COVID-19 who did not recover baseline lung function within 90 d have developed chronic lung allograft dysfunction stage progression.

Community-Acquired Respiratory Viruses Post-Lung Transplant

Survival in lung transplant recipients (LTRs) lags behind heart, liver, and kidney transplant, in part due to the direct and indirect effects of infection. LTRs have increased susceptibility to infection due to the combination of a graft continually exposed to the outside world, multiple mechanisms for impaired mucus clearance, and immunosuppression. Community-acquired respiratory viral infections (CARVs) are common in LTRs. Picornaviruses have roughly 40% cumulative incidence followed by respiratory syncytial virus and coronaviruses. Although single-center retrospective and prospective series implicate CARV in rejection and mortality, conclusive evidence for and well-defined mechanistic links to long-term outcome are lacking. Treatment of viral infections can be challenging except for influenza. Future studies are needed to develop better treatments and clarify the links between CARV and long-term outcomes.

Positive HCMV DNAemia in stem cell recipients undergoing letermovir prophylaxis is expression of abortive infection

Letermovir (LMV) inhibits HCMV replication by binding to components of the HCMV-terminase complex showing a potential role in prevention of HCMV-related complications in allogenic hematopoietic stem cell transplant recipients (allo-HSCTRs). However, little is known about breakthrough HCMV infection and the relevance of HCMV DNAemia during prophylaxis. We reported the results of a multicenter prospective study involving five Italian centers in the management of HCMV DNAemia in 75 adult HCMV-seropositive allo-HSCTRs undergoing LMV prophylaxis. The aim of the present study was to characterize the presence of real HCMV reactivation during LMV prophylaxis. Then, the presence of circulating infectious HCMV particles was determined by virus isolation and degradation of free-floating viral DNA. This report provides the first evidence that during LMV prophylaxis the clinical relevance of HCMV DNAemia should be critically considered.

Human Metapneumovirus and Parainfluenza Virus Infections in Lung Transplant Recipients: the Effects on Lung Allograft and Clinical Outcomes

BACKGROUND

Human metapneumovirus (HMPVi) and parainfluenza virus (PIV) infections are common community acquired infection in lung transplant recipients (LTRs), but data is extremely limited.

METHODS

A retrospective study including all LTRs at the Johns Hopkins Hospital during July 2010-June 2019 with positive HMPV and PIV polymerase chain reaction (PCR) respiratory specimens was performed.

RESULTS

Thirty-one HMPV- and 53 PIV-infected LTRs were identified. LTRs with HMPVi and PIVi had similar baseline characteristics, infection parameters, treatment allocation, and allograft function outcomes. Among entire cohort, 31.6% had CLAD stage progression within 1-year post infections (29.2% vs 35.5% for PIV vs HMPV, respectively, p= 0.56). In forced expiratory volume in 1 second percent (FEV1%) trajectory analysis showed steadily decline of FEV1 across time among CLAD stage progressor from both viruses. FEV1% decline ≥ 10% at 90 days had adjusted hazard ratio for CLAD stage progression of 18.4 [4.98, 67.76] and 4.6 [1.36, 15.34] for PIVi and HMPVi, respectively. PIVi caused higher DSA development (11.8% vs 3.2%, p=0.18) and 1-year mortality (9.4% vs 0%, p=0.11), compared to HMPVi, even though the results were not statistically significant. Ribavirin did not show protective effect and mycophenolate discontinuation during infection did not increase risk of CLAD stage progression.

CONCLUSION

One-third of HMPV- and PIV- infected LTRs developed CLAD stage progression within 1 year. The lack of early lung function recovery may predict long term CLAD progression.

Early T cell reconstitution and cytokine profile may help to guide a personalized management of human cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Human cytomegalovirus (HCMV) infection is one of the major causes of mortality and morbidity after allo-hematopoietic stem cell transplantation (HSCT). Antiviral therapies are associated with toxicity and high economic burden. The aim of this retrospective study was to identify allo-HSCT HCMV-seropositive recipients at low risk of clinically significant HCMV infection who could avoid antiviral therapies. Sixty adult patients who underwent allo-HSCT were clustered in two groups: i) 22 (37%) spontaneously controlling HCMV reactivation (Controllers); ii) 38 (63%) developing clinically significant HCMV infection and receiving pre-emptive therapy (Non-Controllers). We analyzed several patient baseline characteristics, total/HCMV-specific CD4⁺ and CD8⁺ T-cell counts and their cytokine production (IFNγ, TNFα, IL2). Controllers presented a higher number of total/HCMV-specific CD4⁺ and CD8⁺ T-cells (P=0.001 and P=0.017 for total CD4⁺ and CD8⁺ T-cells respectively; P<0.001 for HCMV-specific T-cells) and a lower percentage of mono-functional IFNγ-producing HCMV-specific CD8⁺ T-cells (P=0.002). In bi-variable models, the prognostic impact of the percentage of mono-functional HCMV-specific CD8⁺ T-cells on treatment-free survival, adjusted for total/HCMVspecific CD4⁺ and CD8⁺ T-cells, was confirmed. An HCMV-seronegative donor was the only baseline characteristic associated with a clinically significant infection. These data, when confirmed by a larger prospective study, may provide information for guiding the personalized management of HCMV infection in allo-HSCT recipients.

Community-acquired respiratory viruses

PURPOSE OF REVIEW

Incidence of community-acquired respiratory viruses (CARVs) after lung transplantation (LTx) is 10-68 cases per 100 patient-years. Infected patients may develop graft failure and there seems to be an association between CARV infection and development of chronic lung allograft dysfunction (CLAD). This review summarizes the impact of CARV infection after LTx and potential treatment strategies.

RECENT FINDINGS

Detection rate of CARV depends on diagnostic methods. CARV infections after LTx are reported more frequently probably attributed to improved diagnostic methods, especially nucleic acid testing. Paramyxoviridae and picornaviridae are most frequent. For paramyxoviridae, the association with CLAD is reported in various single-center observational studies. Neuraminidase inhibitors are approved for influenza and can be safely used in flu-infected LTx patients. There is no approved treatment for paramyxoviruses, most centers use ribavirin in the infected LTx recipient.

SUMMARY

Antivirals against CARV in LTx recipients have not yet demonstrated reduced morbidity in randomized clinical trials. Agents against CARV under development are inhibiting viral attachment and use silencing mechanisms of viral replication. The cohort of lung transplant recipients is a focus of intense research because of the high morbidity of CARV infection and intense surveillance of LTx recipeints.

Absence of evidence that respiratory viral infections influence pediatric lung transplantation outcomes: Results of the CTOTC-03 study

Based on reports in adult lung transplant recipients, we hypothesized that community-acquired respiratory viral infections (CARVs) would be a risk factor for poor outcome after pediatric lung transplant. We followed 61 pediatric lung transplant recipients for 2+ years or until they met a composite primary endpoint including bronchiolitis obliterans syndrome/obliterative bronchiolitis, retransplant, or death. Blood, bronchoalveolar lavage, and nasopharyngeal specimens were obtained with standard of care visits. Nasopharyngeal specimens were obtained from recipients with respiratory viral symptoms. Respiratory specimens were interrogated for respiratory viruses by using multiplex polymerase chain reaction. Donor-specific HLA antibodies, self-antigens, and ELISPOT reactivity were also evaluated. Survival was 84% (1 year) and 68% (3 years). Bronchiolitis obliterans syndrome incidence was 20% (1 year) and 38% (3 years). The primary endpoint was met in 46% of patients. CARV was detected in 156 patient visits (74% enterovirus/rhinovirus). We did not find a relationship between CARV recovery from respiratory specimens and the primary endpoint (hazard ratio 0.64 [95% confidence interval: 0.25-1.59], P = .335) or between CARV and the development of alloimmune or autoimmune humoral or cellular responses. These findings raise the possibility that the immunologic impact of CARV following pediatric lung transplant is different than that observed in adults.

Determination of anti-p52 IgM and anti-gB IgG by ELISA as a novel diagnostic tool for detection of early and late phase of primary human cytomegalovirus infections during pregnancy

BACKGROUND

Dating of primary human cytomegalovirus (HCMV) infection in pregnancy is crucial to define whether infection occurred before or during pregnancy and at which gestational age.

OBJECTIVE

The aim of this study was to identify a diagnostic strategy for determination of early, intermediate and late phase of HCMV primary infection during pregnancy.

STUDY DESIGN

Sequential serum samples from 40 pregnant women with defined onset of HCMV primary infection were tested retrospectively for IgM, IgG and IgG avidity against whole HCMV lysate, along with anti-p52 IgM and anti-gB IgG (Euroimmun AG).

RESULTS

Anti-HCMV IgM were positive in all samples collected within the first 2 months, then decreased remaining weakly positive in about 40% of samples collected within 6-12 months after infection. Anti-p52 IgM followed similar kinetics but decreased earlier, remaining weakly positive only in 20% of late samples. Anti-HCMV IgG were positive in all samples and showed variable kinetics. Their avidity increased from low levels, observed within 2 months, to intermediate/high levels from 4 months onwards. Anti-gB IgG increased over time following kinetics similar to anti-HCMV IgG avidity. By combining results of anti-HCMV IgM plus IgG avidity, and confirming them with anti-p52 IgM plus anti-gB IgG as second-line assays, the early (within 2-3 months) and late (after 3 months) phases of HCMV infection were satisfactorily defined, whereas the intermediate phase overlapped with the beginning of the late phase.

CONCLUSION

Anti-p52 IgM and anti-gB IgG provide additional tools besides classical anti-HCMV IgM, IgG and IgG avidity in dating HCMV primary infections.

Respiratory Viral Infections in Transplant Recipients

Respiratory viral infections (RVIs) are common among the general population; however, these often mild viral illnesses can lead to serious morbidity and mortality among recipients of hematopoietic stem cell and solid organ transplantation. The disease spectrum ranges from asymptomatic or mild infections to life-threatening lower respiratory tract infection or long-term airflow obstruction syndromes. Progression to lower respiratory tract infection or to respiratory failure is determined by the intrinsic virulence of the specific viral pathogen as well as various host factors, including the type of transplantation, status of the host’s immune dysfunction, the underlying disease, and other comorbidities. This chapter focuses on the epidemiology, clinical manifestations, diagnosis, and management of RVIs in this susceptible population and includes respiratory syncytial virus, parainfluenza virus, human metapneumovirus, influenza virus, human coronavirus, and human rhinovirus. The optimal management of these infections is limited by the overall paucity of available treatment, highlighting the need for new antiviral drug or immunotherapies.

Community-Acquired Respiratory Viruses

The incidence of community-acquired respiratory viruses (CARVs) is ∼15 cases per 100 patient-years after lung transplantation (LTx). Paramyxoviruses account for almost 50% of the cases of CARV infection in LTx. Most patients will be symptomatic with a mean decline of 15 to 20% in forced expiratory volume in 1 second. The attributable death rate is low in recent years 15 to 25% CARV infected LTx patients will develop chronic lung allograft dysfunction within a year after CARV infection. This risk seems to be increased in comparison to the noninfected LTx recipient.

Detection rate of CARV dependent on clinical awareness, sampling, and diagnostic method with nucleic acid testing by polymerase chain reaction in bronchoalveolar lavage is the gold standard after LTx.

There is no approved treatment for paramyxoviruses, most centers use ribavirin by various routes. Toxicity of systemic ribavirin is of concern and some patients will have contraindication to this treatment modality. Treatment may reduce the risk to develop chronic lung allograft dysfunction and respiratory failure. Agents under development are inhibiting viral attachment and use silencing mechanisms of viral replication.

Cytomegalovirus (CMV) DNA Quantitation in Bronchoalveolar Lavage Fluid From Hematopoietic Stem Cell Transplant Recipients With CMV Pneumonia

Background

Quantitative cytomegalovirus (CMV) DNA-specific polymerase chain reaction (PCR) analysis is widely used as a surveillance method for hematopoietic stem cell transplant (HCT) recipients. However, no CMV DNA threshold exists in bronchoalveolar lavage (BAL) to differentiate pneumonia from pulmonary shedding.

Methods

We tested archived BAL fluid samples from 132 HCT recipients with CMV pneumonia and 139 controls (100 patients with non-CMV pneumonia, 18 with idiopathic pneumonia syndrome [IPS], and 21 who were asymptomatic) by quantitative CMV and β-globin DNA-specific PCR.

Results

Patients with CMV pneumonia had higher median viral loads (3.9 log10 IU/mL; interquartile range [IQR], 2.6-6.0 log10 IU/mL) than controls (0 log10 IU/mL [IQR, 0-1.6 log10 IU/mL] for patients with non-CMV pneumonia, 0 log10 IU/mL [IQR, 0-1.6 log10 IU/mL] for patients with IPS, and 1.63 log10 IU/mL [IQR, 0-2.5 log10 IU/mL] for patients who were asymptomatic; P < .001 for all comparisons to patients with CMV pneumonia). Receiver operating characteristic curve analyses and predictive models identified a cutoff CMV DNA level of 500 IU/mL to differentiate between CMV pneumonia and pulmonary shedding, using current CMV pneumonia prevalence figures. However, different levels may be appropriate in settings of very high or low CMV pneumonia prevalence. The presence of pulmonary copathogens, radiographic presentation, or pulmonary hemorrhage did not alter predictive values.

Conclusion

CMV DNA load in BAL can be used to differentiate CMV pneumonia from pulmonary shedding.

Infectious Triggers of Chronic Lung Allograft Dysfunction

Survival after lung transplantation is limited in large part due to the high incidence of chronic rejection, known as chronic lung allograft dysfunction (CLAD). Pulmonary infections are a frequent complication in lung transplant recipients, due both to immunosuppressive medications and constant exposure of the lung allograft to the external environment via the airways. Infection is a recognized risk factor for the development of CLAD, and both acute infection and chronic lung allograft colonization with microorganisms increase the risk for CLAD. Acute infection by community acquired respiratory viruses, and the bacteria Pseudomonas aeruginosa and Staphylococcus aureus are increasingly recognized as important risk factors for CLAD. Colonization by the fungus Aspergillus may also augment the risk of CLAD. Fostering this transition from healthy lung to CLAD in each of these infectious episodes is the persistence of an inflammatory lung allograft environment.

Neutralizing and ELISA IgG antibodies to human cytomegalovirus glycoprotein complexes may help date the onset of primary infection in pregnancy

BACKGROUND

Definition of onset for primary human cytomegalovirus (HCMV) infection during pregnancy is critical for several reasons, including diagnosis of pre-conceptional infections and definition of gestational age at the time of infection.

OBJECTIVE

To determine the onset of primary HCMV infection, differential kinetics of antibodies neutralizing infection of epithelial and fibroblast cells, as well as ELISA IgG antibodies to HCMV glycoprotein complexes (gC) gH/gL/pUL128L, gH/gL/gO, and gB were exploited and compared with conventional assays.

STUDY DESIGN

In a series of 40 pregnant women with primary HCMV infection and ascertained HCMV-related mild clinical symptoms, the kinetics of different types of neutralizing and ELISA IgG antibodies were investigated with the aim of establishing criteria for dating the onset of primary infection in pregnant women without clinical symptoms.

RESULTS

IgG antibodies to gB and gH/gL/pUL128L, as well as antibodies neutralizing infection of epithelial cells appeared early after infection onset (within 2-3 weeks) and increased rapidly, whereas antibodies to gH/gL/gO and antibodies neutralizing infection of fibroblasts appeared later (>30 days) and increased slowly. Both the conventional diagnostic assays (IgG, and IgM antibody, and IgG avidity index) and the novel assays for determination of antibody responses directed against HCMV gC allowed the definition of an algorithm indicating the onset of primary HCMV infection in asymptomatic women within a period of 1-2 months.

CONCLUSION

New neutralization and ELISA IgG assays to HCMV gC provide additional tools for dating the onset of primary infection in pregnancy.

Emerging and Rare Viral Infections in Transplantation

Immunocompromised patients such as those undergoing solid organ or hematopoietic stem cell transplantation are at substantial risk for infection with numerous pathogens. Infections with cytomegalovirus (CMV), herpes simplex virus (HSV), Epstein–Barr virus (EBV), and human herpesvirus-6 (HHV-6) are well-described complications of transplantation. As viruses previously believed to be quiescent through widespread vaccination (e.g., measles and mumps) reemerge and molecular diagnostic techniques are refined, rare and emerging viral infections are increasingly diagnosed in transplant recipients. This chapter will review the clinical manifestations, diagnosis, and potential antiviral therapies for these viruses in the transplant population.

T-lymphocyte subsets in lung transplant recipients: association between nadir CD4 T-cell count and viral infections after transplantation

BACKGROUND

Little is known about the kinetics of T-cell subsets in lung transplant recipients (LTR) and their association with the occurrence of opportunistic infections (OI).

OBJECTIVES

To analyze the kinetics of T-lymphocyte subsets in LTR and the association between nadir CD4 T-cell count and viral infections after transplantation.

STUDY DESIGN

Serial measurements of peripheral blood CD4 and CD8 T-cell counts obtained during the first year post-transplantation from 83 consecutive LTR and their correlation with both viral OI and community-acquired infections post-transplantation were retrospectively analyzed.

RESULTS

LTR with a nadir CD4 T-cell count <200 cells/μl had consistently lower CD4 and CD8 T-cell counts than LTR with a nadir CD4 T-cell count >200 cells/μl (p<0.001). In LTR with a nadir CD4 T-cell count <200 cells/μl, the cumulative incidence of viral infections detected in peripheral blood and in bronchoalveolar lavage (BAL) samples was higher than in LTR with a nadir CD4 T-cell count >200 cells/μl (p=0.0012 and p=0.0058, respectively). A nadir CD4 T-cell count <200 cells/μl within the first three months post-transplantation predicted a higher frequency of viral infectious episodes in BAL samples within the subsequent six month period (p=0.0066).

CONCLUSIONS

Stratification of patients according to nadir CD4 T-cell count may represent a new and simple approach for early identification of patients at risk for subsequent virus infections.

Reduced frequencies of polyfunctional CMV-specific T cell responses in infants with congenital CMV infection

PURPOSE

CMV infection remains a priority for vaccine development. Vaccination of infants could modify congenital infection and provide lifetime immunity. Properties of CMV-specific T cells associated with control of viral replication in early life have not been fully defined.

METHODS

CMV-specific CD4 and CD8 T cell responses were investigated in infants with congenital CMV infection and compared to adults with primary or chronic infection. PBMC were stimulated with UL83 (pp65) or UL122 (IE-2) peptide pools then stained with antibodies to markers of T cell subset (CD4 or CD8), phenotype (CD45RA, CCR7), or function (MIP1β, CD107, IFNγ, IL2) for flow cytometry analysis.

RESULTS

Detection of CMV pp65-specific CD4 T cells was less common in infants than adults. Responder cells were primarily effector memory (EM, CD45RA-CCR7-) in adults, but mixed memory subsets in infants. Detection of CMV pp65-specific CD8 T cells did not differ between the groups, but infants had lower frequencies of total responding cells and of MIP1β- or CD107-expressing cells. Responder cells were EM or effector memory RA (CD45RA + CCR7-) in all groups. Polyfunctional T cells were less commonly detected in infants than adults. Responses to IE-2 were detected in adults but not infants. All infants had detectable circulating CMV DNA at initial study (versus 60 % of adults with primary infection) despite longer duration of CMV infection.

CONCLUSIONS

Reduced frequencies and altered functional profile of CMV-specific CD4 and CD8 T cell responses were detected in infants compared to adults, and were associated with persistent CMV DNA in peripheral blood.

Respiratory metapneumoviral infection without co-infection in association with acute and chronic lung allograft dysfunction

Background

Metapneumoviral respiratory infection is a community-acquired respiratory viral (CARV) infection. Lung transplantation recipients exposed to CARV are at risk for development of allograft rejection. The cellular and molecular pathways initiated by viral infection leading to allograft dysfunction are not completely understood. The aim of this study was to identify human metapneumoviral (hMPV) cases in association with allograft rejection.

Methods

A literature search was conducted to identify cases of both hMPV and allograft rejection within 6 months of the initial infection. This resulted in 1,007 lung transplantation recipients, with a total of 2,883 samples identified. Of these, 57 demonstrated isolated hMPV without co-infection with other agents.

Results

The results of the study indicate that 35% of acute hMPV infections without co-infection, at the time of detection by molecular diagnostic platforms, were associated with acute cellular rejection within 3 months. There were 9.4% of the cases subsequently associated with chronic allograft dysfunction/bronchiolitis obliterans syndrome, which was collectively termed chronic rejection for purposes of analysis. In conclusion, the prompt identification of isolated hMPV from lung transplantation patients is an important treatable risk factor for subsequent allograft dysfunction. The cellular and molecular pathogenesis of viral-induced allograft rejection remains a topic of future study.

Human cytomegalovirus (HCMV)-specific CD4+ and CD8+ T cells are both required for prevention of HCMV disease in seropositive solid-organ transplant recipients

In solid-organ transplant recipients (SOTR) the protective role of human cytomegalovirus (HCMV)-specific CD4+, CD8+ and γδ T-cells vs. HCMV reactivation requires better definition. The aim of this study was to investigate the relevant role of HCMV-specific CD4+, CD8+ and γδ T-cells in different clinical presentations during the post-transplant period. Thirty-nine SOTR underwent virologic and immunologic follow-up for about 1 year after transplantation. Viral load was determined by real-time PCR, while immunologic monitoring was performed by measuring HCMV-specific CD4+ and CD8+ T cells (following stimulation with autologous HCMV-infected dendritic cells) and γδ T-cells by flow cytometry. Seven patients had no infection and 14 had a controlled infection, while both groups maintained CD4+ T-cell numbers above the established cut-off (0.4 cell/µL blood). Of the remaining patients, 9 controlled the infection temporarily in the presence of HCMV-specific CD8+ only, until CD4+ T-cell appearance; while 9 had to be treated preemptively due to a viral load greater than the established cut-off (3×10(5) DNA copies/mL blood) in the absence of specific CD4+ T-cells. Polyfunctional CD8+ T-cells as well as Vδ2- γδ T-cells were not associated with control of infection. In conclusion, in the absence of HCMV-specific CD4+ T-cells, no long-term protection is conferred to SOTR by either HCMV-specific CD8+ T-cells alone or Vδ2- γδ T-cell expansion.

Epidemiology of respiratory viruses in bronchoalveolar lavage samples in a tertiary hospital

Background

The prevalence of respiratory viruses in adults is largely underexplored, as most studies focus on children. Additionally, in severely ill or immunocompromised adults, where respiratory infections are mostly attributed to bacteria and fungi; respiratory viruses can lead to severe complications.

Objectives

To evaluate the epidemiology of respiratory viruses in bronchoalveolar lavage fluid (BAL) specimens from patients with lower respiratory tract disease. The study population consisted of different groups including immunocompetent patients (control patients), solid organ transplant recipients, patients with haematological malignancies and other immunocompromised adults.

Study design

A total of 134 BAL fluid specimens collected during 2009–2011 were retrospectively assessed with the new commercial multiplex real-time PCR FTD Respiratory 21 Plus^®, targeting 18 different viruses and 2 atypical bacterial pathogens.

Results

Viral or atypical bacterial pathogens were detected in 29.1% of BAL fluid specimens. Coronaviruses were most prevalent (13.4%), followed by rhinoviruses (5.2%), RSV (4.5%) and bocaviruses (3.7%). Comparing the total number of viruses detected, a statistically significant difference was observed between the control group and patients with haematological malignancies (27.5% vs. 57.1%, p < 0.05).

Conclusion

In conclusion, our study highlights the high prevalence of respiratory viruses in BAL fluid specimens from adult patients with lower respiratory tract disease. The methods to be used should be sensitive and cover a wide range of potential pathogens. The specific patient population can also influence the detection rates of respiratory viruses.

Respiratory virus detection in nasopharyngeal aspirate versus bronchoalveolar lavage is dependent on virus type in children with chronic respiratory symptoms

Background

The comparative yield of respiratory virus detection from nasopharyngeal aspirate (NPA) versus bronchoalveolar lavage (BAL) is uncertain. Furthermore, the significance of virus detection and its relationship to lower airway neutrophilic inflammation is poorly studied.

Objectives

To evaluate the sensitivity, specificity and predictive values of NPA for detecting respiratory viruses in BAL; and to determine the relationship between viruses and lower airway neutrophilia in children with non-acute respiratory illness.

Study design

150 paired NPA and BAL samples were obtained from 75 children aged <18 years undergoing flexible bronchoscopy for investigation of chronic respiratory symptoms. Viral studies were performed using polymerase chain reaction (PCR). Cellularity studies were performed on BALs. Diagnostic parameters of NPA compared to BAL and associations between viruses and lower airway %neutrophils were evaluated.

Results

NPA had a higher yield than BAL for detection of any respiratory virus (52 versus 38, respectively). NPA had a high sensitivity (92%) and low specificity (57%) for detecting HRV in BAL with poor kappa agreement value of 0.398 (95% CI 0.218–0.578, p < 0.001). NPA had a fair sensitivity (69%) and good specificity (90.3%) for detecting HAdV on BAL, kappa agreement was 0.561 (95% CI 0.321–0.801, p < 0.001). HAdV positivity on NPA, compared to negativity, was independently associated with heightened airway neutrophilia [mean difference (95% CI): 18 (1,35); p = 0.042].

Conclusions

NPA has a higher yield for respiratory virus detection than BAL, however its diagnostic accuracy is dependent on viral species. Adenovirus positivity is associated with significantly heightened lower airway neutrophilia in children with chronic respiratory symptoms.

Polymerase-chain-reaction-based diagnosis of viral pulmonary infections in immunocompromised children

Aim

Viral pneumonia is a serious complication in immunocompromised children. Its aetiology is difficult to identify owing to the limitations of conventional microbiological tests. The aim of this study was to determine whether polymerase chain reaction (PCR) assays for respiratory viruses increase the diagnostic yield of bronchoalveolar lavage (BAL) in immunocompromised children.

Methods

BAL samples obtained from immunocompromised children hospitalized with pneumonia were processed for respiratory viruses by viral culture, rapid antigen test and PCR (for CMV, adenovirus, influenza, parainfluenza, herpesvirus, RSV and hMPV).

Results

The study group included 42 patients (mean age 7.2 ± 5.1 years) with 50 episodes of clinical pneumonia (50 BAL samples). Forty viral pathogens were identified in 30 episodes (60%). PCR increased the diagnostic rate by fourfold (75% identified by PCR alone, p < 0.0001). When viral culture and rapid antigen test were used as the gold standard, PCR was found to have high sensitivity (86–100% when assessed) and specificity (80–96%). The PCR results prompted the initiation of specific antiviral therapy and the avoidance of unnecessary antibiotic treatment in 17 (34%) episodes.

Conclusion

PCR‐based diagnosis from BAL may increase the rate of pathogen detection in immunocompromised children, decrease the time to diagnosis and spare patients unnecessary antimicrobial treatment.

Fetal human cytomegalovirus transmission correlates with delayed maternal antibodies to gH/gL/pUL128-130-131 complex during primary infection

Primary human cytomegalovirus (HCMV) infections during pregnancy are associated with a high risk of virus transmission to the fetus. To identify correlates of intrauterine HCMV transmission, serial serum samples from HCMV transmitter and non-transmitter pregnant women with primary HCMV infection were analyzed for the presence of neutralizing antibodies against different glycoproteins and glycoprotein complexes, which are known to mediate entry into distinct types of host cells. Neutralizing activity was detected in the sera early after primary infection; absorption with a soluble pentameric complex formed by gH/gL/pUL128-131, but not with gH/gL dimer or with gB, abolished the capacity of sera to neutralize infection of epithelial cells. Importantly, an early, high antibody response to pentamer antigenic sites was associated with a significantly reduced risk of HCMV transmission to the fetus. This association is consistent with the high in vitro inhibition of HCMV infection of epithelial/endothelial cells as well as cell-to-cell spreading and virus transfer to leukocytes by anti-pentamer antibodies. Taken together, these findings indicate that the HCMV pentamer complex is a major target of the antibody-mediated maternal immunity.

Elucidation and clinical role of emerging viral respiratory tract infections in children

Acute respiratory viral infections (ARVI's) are the most common infectious disease in humans. With the appearance of molecular techniques the recovery of viruses has dramatically increased. Nowadays virologists can quickly discriminate virological families and related viruses from emerging viruses and consequently identify novel viruses. Many new respiratory viruses have been identified in children in the past 15 years. In this review we shortly discuss novel respiratory viruses and their pathogenic role in pediatric respiratory disease. Advantages and drawbacks of the technique and our current knowledge will be discussed. We will conclude this review with a general discussion on the future role of molecular diagnostic virology in the clinic.

Rhinovirus and other respiratory viruses exert different effects on lung allograft function that are not mediated through acute rejection

BACKGROUND

Community acquired respiratory virus (CARV) infections in lung transplant recipients (LTR) have been associated with adverse outcomes, including acute rejection (AR) and decline in allograft function, in some but not in all studies.

METHODS

Spirometry and transbronchial biopsy results of LTR diagnosed with CARV infection over a two-yr period were extracted from clinical records. Primary outcomes, studied at 1-2.5 months postinfection, were as follows: (i) incidence of biopsy-proven AR (grade >A0) and (ii) allograft function, defined by forced expiratory volume in one s (FEV(1)). A reference group of biopsies (n = 526) collected during the study period established the baseline incidence of AR. Rhinovirus (RV) and non-rhinovirus (non-RV) infections were analyzed as subgroups.

RESULTS

Eighty-seven cases of CARV infection were identified in 59 subjects. Incidences of AR were similar in the post-CARV and reference groups and did not differ significantly after RV vs. non-RV infection. Allograft function declined significantly after non-RV infection, but not after RV infection.

CONCLUSIONS

In LTR, CARV infections other than RV are associated with allograft dysfunction at 1-2.5 months after infection. However, CARVs do not appear associated with AR at this time point. The impact of specific CARVs on lung allografts, including the development of chronic allograft rejection, merits further study.

Kinetics of human cytomegalovirus (HCMV) DNAemia in transplanted patients expressed in international units as determined with the Abbott RealTime CMV assay and an in-house assay

BACKGROUND

Consensus human cytomegalovirus (HCMV) DNA cut-off values for preemptive therapy in transplant recipients have not yet been defined, mainly due to the lack of real-time PCR standardization.

OBJECTIVES

(i) To compare the kinetics of HCMV DNA in transplanted patients using an in-house real-time PCR assay (Pavia assay) and the new Abbott RealTime CMV assay; (ii) to verify assay concordance in the identification of patients eligible for preemptive treatment and (iii) standardize results with international units (IUs) using the WHO International HCMV DNA Standard as a reference.

STUDY DESIGN

The kinetics of HCMV disseminated infection was retrospectively evaluated in 513 stored whole blood samples from 37 transplanted patients enrolled in randomized prospective studies designed for the clinical validation of HCMV DNA cut-off values. Conversion factors of HCMV DNA copy number to WHO international units (IUs) were determined.

RESULTS

Among the 513 samples, 352 (68.6%) were concordant positive, 42 (8.1%) concordant negative and 119 (23.1%) discordant. All discordant samples resulted positive by the Abbott RealTime CMV assay and negative by the Pavia assay, showing higher sensitivity for the Abbott RealTime CMV assay. A significant correlation was observed between concordant positive samples (r=0.89). HCMV DNAemia determined by each assay showed overlapping kinetics. Expression of results as IU/ml provided the best results in preemptive treatment simulation.

CONCLUSION

HCMV DNAemia cut-off values determined using our in-house assay and expressed as IU/ml appear valid for use in commercial assays as well as other potential in-house assays.

Monitoring of human cytomegalovirus and virus-specific T-cell response in young patients receiving allogeneic hematopoietic stem cell transplantation

In allogeneic hematopoietic stem-cell transplantation (HSCT) recipients, outcome of human cytomegalovirus (HCMV) infection results from balance between viral load/replication and pathogen-specific T-cell response. Using a cut-off of 30,000 HCMV DNA copies/ml blood for pre-emptive therapy and cut-offs of 1 and 3 virus-specific CD4⁺ and CD8⁺ T cells/µl blood for T-cell protection, we conducted in 131 young patients a prospective 3-year study aimed at verifying whether achievement of such immunological cut-offs protects from HCMV disease. In the first three months after transplantation, 55/89 (62%) HCMV-seropositive patients had infection and 36/55 (65%) were treated pre-emptively, whereas only 7/42 (17%) HCMV-seronegative patients developed infection and 3/7 (43%) were treated. After 12 months, 76 HCMV-seropositive and 9 HCMV-seronegative patients (cumulative incidence: 90% and 21%, respectively) displayed protective HCMV-specific immunity. Eighty of these 85 (95%) patients showed spontaneous control of HCMV infection without additional treatment. Five patients after reaching protective T-cell levels needed pre-emptive therapy, because they developed graft-versus-host disease (GvHD). HSCT recipients reconstituting protective levels of HCMV-specific T-cells in the absence of GvHD are no longer at risk for HCMV disease, at least within 3 years after transplantation. The decision to treat HCMV infection in young HSCT recipients may be taken by combining virological and immunological findings.

Respiratory viral infections post-lung transplantation

Community-acquired respiratory viruses (CARVs) are common pathogens in lung transplant recipients. Infection due to these viruses is associated with multiple complications including: rhinitis, pharyngitis, bronchitis, pneumonia, respiratory failure and even death. CARVs have also become increasingly recognized as a risk factor for acute rejection (AR) and bronchiolitis obliterans syndrome (BOS). Newer diagnostic techniques have enhanced the accuracy of diagnosis, but proven treatment options for CARVs are limited. Further insight into the immune response and allograft dysfunction associated with CARV infections is needed in order to develop novel management strategies which can reduce the morbidity and mortality caused by these infectious agents.

Virologic and immunologic monitoring of cytomegalovirus to guide preemptive therapy in solid-organ transplantation

Control of human cytomegalovirus (HCMV) infection during the posttransplant period was investigated in 134 solid-organ transplant recipients by monitoring in parallel virologic and immunologic parameters for at least 1 year of follow-up. Virologic monitoring was achieved by determining HCMV DNAemia with real-time PCR, using the threshold of 300 000 DNA copies/mL blood as a cutoff for starting preemptive therapy. Immunologic monitoring included measurement of HCMV-specific CD4+ and CD8+ T cells by cytokine flow cytometry, using HCMV-infected dendritic cells as a stimulus. HCMV infection was diagnosed in 110 (82%) and required treatment in 49 (36%) patients. At 12 months after transplantation 'protective' immunity (≥0.4 CD4+ and CD8+ HCMV-specific T cells/μL blood) was achieved in 115/129 (89%) patients. During the entire study period, 122 patients reconstituting HCMV-specific CD4+ and CD8+ T-cell immunity at 60 days posttransplant onward were able to control HCMV infection, except for one patient who developed HCMV disease because of a rejection episode. Patients reconstituting HCMV-specific CD8+ only did not control HCMV infection. In conclusion, the presence of both HCMV-specific CD4+ and CD8+ T cells ≥ 0.4/μL blood appears to be protective against HCMV disease. This result does not apply to patients undergoing antirejection treatment, or reconstituting HCMV-specific CD8+ T cells only.

Molecular epidemiology of human coronavirus OC43 reveals evolution of different genotypes over time and recent emergence of a novel genotype due to natural recombination

Although human coronavirus OC43-OC43 (HCoV-OC43) is the coronavirus most commonly associated with human infections, little is known about its molecular epidemiology and evolution. We conducted a molecular epidemiology study to investigate different genotypes and potential recombination in HCoV-OC43. Twenty-nine HCoV-OC43 strains from nasopharyngeal aspirates, collected from 2004 to 2011, were subjected to RNA-dependent RNA polymerase (RdRp), spike, and nucleocapsid gene analysis. Phylogenetic analysis showed at least three distinct clusters of HCoV-OC43, although 10 unusual strains displayed incongruent phylogenetic positions between RdRp and spike genes. This suggested the presence of four HCoV-OC43 genotypes (A to D), with genotype D most likely arising from recombination. The complete genome sequencing of two genotype C and D strains and bootscan analysis showed recombination events between genotypes B and C in the generation of genotype D. Of the 29 strains, none belonged to the more ancient genotype A, 5 from 2004 belonged to genotype B, 15 from 2004 to 2006 belonged to genotype C, and 1 from 2004 and all 8 from 2008 to 2011 belonged to the recombinant genotype D. Molecular clock analysis using spike and nucleocapsid genes dated the most recent common ancestor of all genotypes to the 1950s, genotype B and C to the 1980s, genotype B to the 1990s, and genotype C to the late 1990s to early 2000s, while the recombinant genotype D strains were detected as early as 2004. This represents the first study to describe natural recombination in HCoV-OC43 and the evolution of different genotypes over time, leading to the emergence of novel genotype D, which is associated with pneumonia in our elderly population.

Respiratory viral infections in hematopoietic stem cell and solid organ transplant recipients

Respiratory viral infections (RVIs) are common causes of mild illness in immunocompetent children and adults with rare occurrences of significant morbidity or mortality. Complications are more common in the very young, very old, and those with underlying lung diseases. However, RVIs are increasingly recognized as a cause of morbidity and mortality in recipients of hematopoietic stem cell transplants (HSCT) and solid organ transplants (SOTs). Diagnostic techniques for respiratory syncytial virus (RSV), parainfluenza, influenza, and adenovirus have been clinically available for decades, and these infections are known to cause serious disease in transplant recipients. Modern molecular technology has now made it possible to detect other RVIs including human metapneumovirus, coronavirus, and bocavirus, and the role of these viruses in causing serious disease in transplant recipients is still being worked out. This article reviews the current information regarding epidemiology, pathogenesis, clinical presentation, diagnosis, and treatment of these infections, as well as the aspects of clinical significance of RVIs unique to HSCT or SOT.

Respiratory viruses in lung transplant recipients: a critical review and pooled analysis of clinical studies

Lung transplant recipients present an increased risk for severe complications associated with respiratory infections. We conducted a review of the literature examining the clinical relationship between viral respiratory infection and graft complications. Thirty-four studies describing the clinical impact of influenza, respiratory syncytial virus, parainfluenza, human metapneumovirus, rhinovirus, enterovirus, coronavirus, bocavirus or adenovirus were identified. The detection rate of respiratory viral infection ranged from 1.4% to 60%. Viruses were detected five times more frequently when respiratory symptoms were present [odds ratio (OR) = 4.97; 95% CI = 2.11-11.68]. Based on available observations, we could not observe an association between respiratory viral infection and acute rejection (OR = 1.35; 95% CI = 0.41-4.43). We found a pooled incidence of 18% (9/50) of bronchiolitis obliterans syndrome (BOS) in virus-positive cases compared to 11.6% (37/319) in virus-negative cases; however, limited number of BOS events did not allow to confirm the association. Our review confirms a causal relationship between respiratory viruses and respiratory symptoms, but cannot confirm a link between respiratory viruses and acute lung rejection. This is related in part to the heterogeneity and limitations of available studies. The link with BOS needs also to be reassessed in appropriate prospective studies.

Role of prenatal diagnosis and counseling in the management of 735 pregnancies complicated by primary human cytomegalovirus infection: a 20-year experience

BACKGROUND

The burden of congenital human cytomegalovirus (HCMV) infection is well recognized. However, screening for maternal infection remains controversial in view of diagnostic challenges, counseling difficulties, and absence of medical treatment.

OBJECTIVE

To assess the role of prenatal diagnosis and counseling in the management of pregnancy complicated by primary HCMV infection.

STUDY DESIGN

Retrospective study aimed at investigating diagnostic features, options, and pregnancy outcome in 735 women with primary HCMV infection over a period of 20 years (1990-2009).

RESULTS

Overall, 25.6% women were found to be seronegative before the actual pregnancy. However, none were informed about HCMV infection and potential prevention strategies. Diagnosis of primary HCMV infection was achieved by seroconversion in 44.4% cases and by different combinations of virus-specific IgM, low IgG avidity, and DNAemia in 43.9% cases. Non-specific symptoms and/or haematological/biochemical alterations were recalled by 73.5% women. The onset of infection could be established, and counseling adjusted accordingly in >90% cases. The overall rate of vertical transmission was 37.1%, ranging from 5.6% for preconceptional infections to 64.1% for third trimester infections. Amniocentesis was chosen by 43.1% women, whereas pregnancy termination was requested by 15.6%.

CONCLUSIONS

Reference virology centers and ad hoc trained and experienced physicians are required for accurate diagnosis of primary infection in pregnancy and ensuing counseling. Prenatal diagnosis has a central role in the management of pregnancies complicated by primary HCMV infection. HCMV-seronegative women should receive adequate information.

Prognostic markers of symptomatic congenital human cytomegalovirus infection in fetal blood

OBJECTIVE

To identify fetal cord blood prognostic markers of symptomatic congenital human cytomegalovirus infection (HCMV).

DESIGN

Retrospective observational study.

SETTING

Fetal medicine unit in Milan and Medical virology unit in Pavia, Italy.

POPULATION

HCMV-infected and -uninfected fetuses of mothers with primary HCMV infection during the period 1995-2009.

METHODS

Overall, 94 blood samples from as many fetuses of 93 pregnant women experiencing primary HCMV infection were examined for multiple immunological, haematological and biochemical markers as well as virological markers. Congenital HCMV infection was diagnosed by detection of virus in amniotic fluid, and symptomatic/asymptomatic infections were determined by ultrasound scans, nuclear magnetic resonance imaging, histopathology or clinical examination at birth. Blood sample markers were retrospectively compared in symptomatic and asymptomatic fetuses with congenital infection.

MAIN OUTCOME MEASURES

A statistical analysis was performed to determine the value of each parameter in predicting outcome.

RESULTS

Univariate analysis showed that most nonviral and viral markers were significantly different in symptomatic (n = 16) compared with asymptomatic (n = 31) fetuses. Receiver operator characteristics analysis indicated that, with reference to an established cutoff for each marker, the best nonviral factors for differentiation of symptomatic from asymptomatic congenital infection were β(2) -microglobulin and platelet count, and the best virological markers were immunoglobulin M antibody and DNAaemia. β(2) -Microglobulin alone or the combination of these four markers reached the optimal diagnostic efficacy.

CONCLUSIONS

The determination of multiple markers in fetal blood, following virus detection in amniotic fluid samples, is predictive of perinatal outcome in fetuses with HCMV infection.

Analysis of viral load in children infected with human metapneumovirus

OBJECTIVE

Human metapneumovirus (hMPV) is a respiratory pathogen responsible for disease and subsequent hospitalizations in young children around the world. The disease pathology, including how viral load correlates with respiratory disease severity, remains unclear. This study investigated the correlation between viral load and clinical characteristics of hMPV infections.

METHODS

Nasopharyngeal aspirate (NPA) samples collected from 18 infants hospitalized for lower respiratory tract infections (LRTIs) in winter were tested for hMPV by reverse transcriptase polymerase chain reaction (RT-PCR) and real-time RT-PCR. Their NPA samples were collected every-other-day to monitor changes in hMPV viral load during hospitalization. Also all these 18 patients were monitored to characterize clinically their illness.

FINDINGS

hMPV load was not correlated with infection severity (P=0.5, 0.9, 0.5). In contrast, the log(10) of hMPV viral load was significantly different between those lasted for 6-11 days and those for less than 5 days (P=0.01), also the significant difference was shown between those of 6-11 days duration and those of more than 11 days (P=0.006), but there was no significant difference between those lasted for less than 5 days and those for more than 11 days (P=0.4). Additionally, high hMPV viral shedding occured between 6 and 11days.

CONCLUSION

hMPV load was significantly correlated with the course of illness. The association between hMPV viral load and the course of disease suggested that hMPV is an important pathogen in lower respiratory tract infection in children. But hMPV did not always lead to more severe respiratory illness.

Upper and lower respiratory tract viral infections and acute graft rejection in lung transplant recipients

BACKGROUND

Lung transplant recipients are frequently exposed to respiratory viruses and are particularly at risk for severe complications. The aim of this study was to assess the association among the presence of a respiratory virus detected by molecular assays in bronchoalveolar lavage (BAL) fluid, respiratory symptoms, and acute rejection in adult lung transplant recipients.

METHODS

Upper (nasopharyngeal swab) and lower (BAL) respiratory tract specimens from 77 lung transplant recipients enrolled in a cohort study and undergoing bronchoscopy with BAL and transbronchial biopsies were screened using 17 different polymerase chain reaction-based assays.

RESULTS

BAL fluid and biopsy specimens from 343 bronchoscopic procedures performed in 77 patients were analyzed. We also compared paired nasopharyngeal and BAL fluid specimens collected in a subgroup of 283 cases. The overall viral positivity rate was 29.3% in the upper respiratory tract specimens and 17.2% in the BAL samples (P < .001). We observed a significant association between the presence of respiratory symptoms and positive viral detection in the lower respiratory tract (P = .012). Conversely, acute rejection was not associated with the presence of viral infection (odds ratio, 0.41; 95% confidence interval, 0.20-0.88). The recovery of lung function was significantly slower when acute rejection and viral infection were both present.

CONCLUSIONS

A temporal relationship exists between acute respiratory symptoms and positive viral nucleic acid detection in BAL fluid from lung transplant recipients. We provide evidence suggesting that respiratory viruses are not associated with acute graft rejection during the acute phase of infection.

Population-based incidence of human metapneumovirus infection among hospitalized children

Background. Human metapneumovirus (HMPV) is a leading cause of acute respiratory illness (ARI) in children. Population-based incidence rates and comprehensive clinical characterizations of disease have not been established.

Methods. We conducted population-based prospective surveillance for 2 years in 2 US counties of HMPV infection among children <5 years old who were hospitalized with ARI or fever. Nasal and throat specimens obtained with swabs were tested for HMPV by real-time reverse-transcription polymerase chain reaction and genotyped.

Results. Forty-two (3.8%) of 1104 children tested positive for HMPV. The overall annual rate of HMPVassociated hospitalizations per 1000 children <5 years old was 1.2 (95% confidence interval [CI], 0.9–1.6). This rate was highest among infants 0–5 months old (4.9 per 1000 [95% CI, 2.9–7.2]), followed by children 6–11 months old (2.9 per 1000 [95% CI, 1.4–4.7]). The annual rate of hospitalization for HMPV infection was less than that for respiratory syncytial virus infection but similar to that for influenza and parainfluenza virus 3 infection in all age groups. The mean age of children hospitalized with HMPV infection was 6 months. Bronchiolitis, pneumonia, and asthma were the most common diagnoses among children with HMPV infection. All 4 HMPV subgroups were detected during both years at both sites. HPMV infection was most prominent from March through May.

Conclusion. HMPV was detected in 3.8% of children hospitalized with ARI or fever, with a population incidence similar to that of influenza virus and parainfluenza virus 3.

Long-term impact of respiratory viral infection after pediatric lung transplantation

To evaluate the epidemiology and to investigate the impact of RVI on chronic allograft rejection after pediatric lung transplantation, a retrospective study of pediatric lung transplant recipients from 2002 to 2007 was conducted. Association between RVI and continuous and categorical risk factors was assessed using Wilcoxon rank-sum tests and Fisher's exact tests, respectively. Association between risk factors and outcomes were assessed using Cox proportional hazards models. Fifty-five subjects were followed for a mean of 674 days (range 14-1790). Twenty-eight (51%) developed 51 RVI at a median of 144 days post-transplant (mean 246; range 1-1276); 41% of infections were diagnosed within 90 days. Twenty-five subjects developed 39 LRI, and eight subjects had 11 URI. Organisms recovered included rhinovirus (n = 14), adenovirus (n = 10), parainfluenza (n = 10), influenza (n = 5), and RSV (n = 4). Three subjects expired secondary to their RVI (two adenovirus, one RSV). Younger age and prior CMV infection were risks for RVI (HR 2.4 95% CI 1.1-5.3 and 17.0; 3.0-96.2, respectively). RVI was not associated with the development of chronic allograft rejection (p = 0.25) or death during the study period. RVI occurs in the majority of pediatric lung transplant recipients, but was not associated with mortality or chronic allograft rejection.

Challenges of T cell therapies for virus-associated diseases after hematopoietic stem cell transplantation

IMPORTANCE OF THE FIELD

Hematopoietic stem cell transplantation (HSCT) is the treatment of choice for many hematological malignancies and genetic disorders. The majority of patients do not have a human leukocyte antigen (HLA) identical sibling donor, and alternative stem cell sources include HLA-matched or mismatched unrelated donors and haploidentical related donors. However, alternative donor HSCT are associated with three major complications i) graft rejection; ii) graft-versus-host disease (GvHD); and iii) delayed immune reconstitution leading to viral infections and relapse.

AREAS COVERED IN THIS REVIEW

Graft rejection and the risk of GvHD can be significantly reduced by using intensive conditioning regimens, including in vivo T cell depletion as well as ex vivo T cell depletion of the graft. However, the benefits of removing alloreactive T cells from the graft are offset by the concomitant removal of T cells with anti-viral or anti-tumor activity as well as the profound delay in endogenous T cell recovery post-transplant. Thus, opportunistic infections, many of which are not amenable to conventional small-molecule therapeutics, are frequent in these patients and are associated with significant morbidity and high mortality rates. This review discusses current cell therapies to prevent or treat viral infections/reactivations post-transplant.

WHAT THE READER WILL GAIN

The reader will gain an understanding of the current state of cell therapy to prevent and treat viral infections post-HSCT, and will be introduced to preclinical studies designed to develop and validate new manufacturing procedures intended to improve therapeutic efficacy and reduce associated toxicities.

TAKE HOME MESSAGE

Reconstitution of HSCT recipients with antigen-specific T cells, produced either by allodepletion or in vitro reactivation, can offer an effective strategy to provide both immediate and long-term protection without harmful alloreactivity.