What do we know about the genomics of human adenovirus type 55 (HAdV-55)?
This pathogen was fully characterized by whole-genome sequencing
INTRODUCTION: Since 2008, severe cases of emerging human adenovirus type 55 HAdV-55 in immunocompetent adults have been reported sporadically in China. The clinical features and outcomes of the most critically ill patients with severe acute respiratory distress syndrome ARDS caused by HAdV-55 requiring invasive mechanical ventilation IMV and/or extracorporeal membrane oxygenation ECMO are lacking. METHODS: We conducted a prospective, single-center observational study of pneumonia with ARDS in immunocompetent adults admitted to our respiratory ICU. We prospectively collected and analyzed clinical, laboratory, radiological characteristics, sequential tests of viral load in respiratory tract and blood, treatments and outcomes. RESULTS: The results for a total of five consecutive patients with severe ARDS with confirmed HAdV-55 infection were included. All five patients were immunocompetent young men with a median age of 32 years. RESULTS: The results for a total of five consecutive patients with severe ARDS with confirmed HAdV-55 infection were included. All five patients were immunocompetent young men with a median age of 32 years. The mean time from onset to dyspnea was 5 days. Arterial blood gas analysis at ICU admission revealed profound hypoxia. Mean partial oxygen pressure/fraction of inspired oxygen was 58.1. Mean durations from onset to a single-lobe consolidation shown on chest X-rays CXRs and, from the first positive CXR to bilateral multilobar lung infiltrates, were 2 days and 4.8 days, respectively. The viral load was higher than 1 × 10. copies in three patients and was 1 × 10. in one patient. Mean durations from onset to a single-lobe consolidation shown on chest X-rays CXRs and, from the first positive CXR to bilateral multilobar lung infiltrates, were 2 days and 4.8 days, respectively. The viral load was higher than 1 × 10. copies in three patients and was 1 × 10. in one patient. It was negative in the only patient who survived. The mean duration for noninvasive positive pressure ventilation NPPV failure and IMV failure were 30.8 hours and 6.2 days, respectively. Four patients received venovenous ECMO. Four 80% of the five patients died despite receiving appropriate respiratory support. CONCLUSIONS: HAdV-55 may cause severe ARDS in immunocompetent young men. Four patients received venovenous ECMO. Four 80% of the five patients died despite receiving appropriate respiratory support. CONCLUSIONS: HAdV-55 may cause severe ARDS in immunocompetent young men. Persistent high fever, dyspnea and rapid progression to respiratory failure within 2 weeks, together with bilateral consolidations and infiltrates, are the most frequent clinical manifestations of HAdV-55-induced severe ARDS. Viral load monitoring may help predict disease severity and outcome. The NPPV and IMV failure rates were very high, but ECMO may still be the respiratory support therapy of choice. TRIAL REGISTRATION: Clinicaltrials.gov NCT01585922. The NPPV and IMV failure rates were very high, but ECMO may still be the respiratory support therapy of choice. TRIAL REGISTRATION: Clinicaltrials.gov NCT01585922. Registered 20 April 2012 Text: Human adenoviruses HAdVs are notorious pathogens in people with compromised immune function and a frequent cause of outbreaks of acute respiratory disease among young children. Life-threatening adenoviral pneumonia has previously been documented among military trainees, patients with AIDS and transplant recipients  . Human adenovirus type 55 HAdV-55 , which is emerging as a highly virulent pathogen for acute fatal adenoviral pneumonia among immunocompetent adults in China, has gained increasing attention . HAdV-55 is a newly identified, emergent acute respiratory disease pathogen causing two recent outbreaks in China in 2006 and in Singapore in 2005 . Human adenovirus type 55 HAdV-55 , which is emerging as a highly virulent pathogen for acute fatal adenoviral pneumonia among immunocompetent adults in China, has gained increasing attention . HAdV-55 is a newly identified, emergent acute respiratory disease pathogen causing two recent outbreaks in China in 2006 and in Singapore in 2005 . In 2011, this pathogen apparently re-emerged in Beijing, China, causing several cases of severe community-acquired pneumonia . This pathogen was fully characterized by whole-genome sequencing . Comparative studies showed that the ability of HAdV to cause severe disease may relate to the serotypes of HAdVs. Severe adenoviral pneumonia induced by HAdV-55 has been reported to be more closely related to severe cases compared to other serotypes HAdV-3, HAdV-7 and HAdV-14 . Comparative studies showed that the ability of HAdV to cause severe disease may relate to the serotypes of HAdVs. Severe adenoviral pneumonia induced by HAdV-55 has been reported to be more closely related to severe cases compared to other serotypes HAdV-3, HAdV-7 and HAdV-14 . Current knowledge of HAdV-55-induced severe acute respiratory distress syndrome ARDS requiring invasive mechanical ventilation and/or extracorporeal membrane oxygenation ECMO support in immunocompetent adults is derived from single case reports or relatively small, single-center series. As a result, little information is available on HAdV-55 pneumonia complicated with severe ARDS, the frequency of which is expected to increase in the coming years. Here we describe the clinical features and outcomes of five prospective cases of HAdV-55 pneumonia complicated with severe ARDS in immunocompetent adults in our ICU. Beginning in May 2012, a randomized trial of noninvasive positive pressure ventilation NPPV in ARDS patients was carried out in our center ClinicalTrials.gov ID: NCT01585922 . Here we describe the clinical features and outcomes of five prospective cases of HAdV-55 pneumonia complicated with severe ARDS in immunocompetent adults in our ICU. Beginning in May 2012, a randomized trial of noninvasive positive pressure ventilation NPPV in ARDS patients was carried out in our center ClinicalTrials.gov ID: NCT01585922 . From May 2012 to April 2014, all adult patients with ARDS caused by pneumonia who were admitted to the respiratory ICU of Beijing Chao-Yang Hospital were prospectively enrolled. Severe ARDS was diagnosed according to the Berlin definition: . developing within 1 week of a known clinical insult or new or worsening respiratory symptoms; . bilateral opacities not fully explained by effusions, lobar and/or lung collapse, or nodules; . developing within 1 week of a known clinical insult or new or worsening respiratory symptoms; . bilateral opacities not fully explained by effusions, lobar and/or lung collapse, or nodules; . respiratory failure not fully explained by cardiac failure or fluid overload; . partial oxygen pressure/ fraction of inspired oxygen PaO 2 /FiO 2 ≤100 mmHg with positive end-expiratory pressure PEEP ≥5 cmH 2 O; and . a chest radiograph with three or four quadrants with opacities. Patients with HAdV-55 infection and severe ARDS who failed conventional NPPV and invasive mechanical ventilation IMV were included in the analysis. This study was approved by the Institutional Review Board of Beijing Chao-Yang Hospital LLKYPJ2012031 . Data were analyzed anonymously. This study was approved by the Institutional Review Board of Beijing Chao-Yang Hospital LLKYPJ2012031 . Data were analyzed anonymously. Each patient gave written informed consent for their data to be used for research and publication. Clinical information collected by investigators with a standardized data form included the following: demographic characteristics age and sex , comorbidities, clinical symptoms fever, cough, sputum, dyspnea, chest pain, rash, nausea, vomiting, abdominal pain, diarrhea and headache , signs body temperature, heart rate, respiratory frequency, blood pressure and crackles in the lungs , laboratory tests whole-blood cell count and blood chemistry and microbiological findings and images of the lung chest X-ray CXR and computed tomography . Concomitant medications, respiratory support, complications and outcomes were also recorded. Patients' specimens, including sputum, whole blood and serum samples, were collected upon admission and during hospitalization. Concomitant medications, respiratory support, complications and outcomes were also recorded. Patients' specimens, including sputum, whole blood and serum samples, were collected upon admission and during hospitalization. Microbiological tests were performed at the Department of Infectious Disease and Clinical Microbiology in our center, and the detection methods used were described in our previous report . Common viruses causing respiratory illness were screened using a kit with 15 different viral assays. Serum samples were used for Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella pneumophila antibodies. All patients had their HAdV-55 infection confirmed by RT-PCR assay. Partial sequences of the hexon gene were analyzed to type the phylogeny of HAdV-55 strains. All patients had their HAdV-55 infection confirmed by RT-PCR assay. Partial sequences of the hexon gene were analyzed to type the phylogeny of HAdV-55 strains. The adenoviral load was also performed on both respiratory specimens and blood by multiplex RT-PCR assay. Viral pneumonia was diagnosed based on the presence of HAdV detected in sputum or throat swab samples by molecular methods. Continuous variables were summarized as mean ± standard deviation SD or median interquartile range . During the study period, a total of eight patients diagnosed with HAdV infection and respiratory failure were admitted to our ICU, and seven of them received a diagnosis of ARDS. Continuous variables were summarized as mean ± standard deviation SD or median interquartile range . During the study period, a total of eight patients diagnosed with HAdV infection and respiratory failure were admitted to our ICU, and seven of them received a diagnosis of ARDS. Five consecutive patients with severe ARDS with confirmed HAdV-55 infection were admitted to our ICU between April and July 2013. They were included in the analysis. The other two patients had mild ARDS and were infected with other types of HAdVs. All five patients were immunocompetent young men with a median age of 32 years range, 28 to 40 years . The other two patients had mild ARDS and were infected with other types of HAdVs. All five patients were immunocompetent young men with a median age of 32 years range, 28 to 40 years . All of the patients shared a B blood type and came from the same city: Baoding city, Hebei province, northern China. All patients had no exposure to farm animals, corn or hay. Patient 3 had tuberculosis pleuritis and received antituberculosis therapy at ICU admission. His blood tests, including the T-SPOT tuberculosis assay Oxford Immunotec, Marlborough, MA, USA and antibody of Mycobacterium tuberculosis, were negative. Patient 3 had tuberculosis pleuritis and received antituberculosis therapy at ICU admission. His blood tests, including the T-SPOT tuberculosis assay Oxford Immunotec, Marlborough, MA, USA and antibody of Mycobacterium tuberculosis, were negative. Flulike symptoms, such as fever, cough and little sputum, were commonly observed at the onset of illness. All patients presented with a high fever, with a mean body temperature of 39.5°C range, 39.0°C to 40.0°C , which persisted for 8 days range, 6 to 11 days . Productive cough was observed in two patients. Dull substernal chest pain and rash were also observed in two patients. All patients had dyspnea. Productive cough was observed in two patients. Dull substernal chest pain and rash were also observed in two patients. All patients had dyspnea. The mean time from onset to dyspnea was 5 days range, 1 to 10 days . After the onset of dyspnea, patients usually progressed to respiratory failure or hypoxemia. The mean time from onset to ICU admission was 9.6 days range, 8 to 11 days Table 1 . All patients had tachypnea when admitted to the ICU, with a mean rate of 43 breaths per minute range = 38 to 52 . The mean time from onset to ICU admission was 9.6 days range, 8 to 11 days Table 1 . All patients had tachypnea when admitted to the ICU, with a mean rate of 43 breaths per minute range = 38 to 52 . Arterial blood gas analysis at ICU admission revealed profound hypoxia, with a mean PaO 2 /FiO 2 of 58.1 range = 49 to 62.5 . White blood cell counts were low or in the normal range. All patients had elevated serum aspartate aminotransferase AST , lactate dehydrogenase LDH and hydroxybutyrate dehydrogenase HBDH Table 1 . At admission, all patients' levels of immunoglobulin serum immunoglobulins G and M and components C3 and C4 were in the normal range. All patients had elevated serum aspartate aminotransferase AST , lactate dehydrogenase LDH and hydroxybutyrate dehydrogenase HBDH Table 1 . At admission, all patients' levels of immunoglobulin serum immunoglobulins G and M and components C3 and C4 were in the normal range. Four patients had lower than normal T-cell subset counts Table 2 . CXRs revealed multiple bilateral lobar or segment consolidation in the lungs of all five patients, and radiographic lesions progressed rapidly after ICU admission Figure 1 . Three patients were examined by highresolution computed tomography HRCT . Unilateral or bilateral consolidations and infiltrates were found on HRCT scans of all three of these patients. Three patients were examined by highresolution computed tomography HRCT . Unilateral or bilateral consolidations and infiltrates were found on HRCT scans of all three of these patients. Consolidations within a single lobe or several lobes with a clear border and air bronchogram were the most common findings on HRCT scans. Nodules, patches, pleural effusion, abscess and a cavity were also seen visualized by HRCT Figure 2 . The mean duration from onset to a single-lobe consolidation on CXRs was 2 days range = 1 to 5 days . The mean duration from the first positive CXR to bilaterally multilobar lung infiltrates was 4.8 days range = 4 to 7 days . All patients had HAdV-55 viremia. The mean duration from the first positive CXR to bilaterally multilobar lung infiltrates was 4.8 days range = 4 to 7 days . All patients had HAdV-55 viremia. In four of the five patients, it was first detected in endotracheal aspirate ETA samples. The time between initial ETA sample collection of adenoviruses and positive results for HAdV-55 nucleic acid in the blood was 1 to 10 days Table 3 . Virus DNA copies in ETAs were determined for all patients during their ICU stay. The viral load was higher than 1 × 10 8 copies in three patients and 1 × 10 4 in one patient. The viral load became negative in the only patient who survived. The viral load was higher than 1 × 10 8 copies in three patients and 1 × 10 4 in one patient. The viral load became negative in the only patient who survived. In the four patients who did not survive, DNA copies did not decrease, even with antiviral therapy Figure 3 . Oxygenation was not maintained with conventional NPPV or IMV support in any of the patients. The mean duration until NPPV failure was 30.8 hours range = 22 to 48 hours , and the mean time until IMV failure was 6.2 days range 2 = to 13 days Table 1 . Four patients received venovenous ECMO to maintain oxygen saturation, and one patient refused ECMO support and received high-frequency oscillatory ventilation instead. The mean duration until NPPV failure was 30.8 hours range = 22 to 48 hours , and the mean time until IMV failure was 6.2 days range 2 = to 13 days Table 1 . Four patients received venovenous ECMO to maintain oxygen saturation, and one patient refused ECMO support and received high-frequency oscillatory ventilation instead. Table 4 gives the oxygenation data of patients before and after venovenous ECMO support. All patients received antiviral therapy, including acyclovir 10 mg/kg, every 8 hours, intravenous drip , ganciclovir 5 mg/kg, every 12 hours, intravenous drip and ribavirin 250 mg, twice daily, intravenous drip . Considering that bacterial coinfection may combine with a severe viral infection, broad-spectrum intravenous antibiotics were given to all patients. Tests for bacterial pathogens were negative for only one patient Table 3 . Considering that bacterial coinfection may combine with a severe viral infection, broad-spectrum intravenous antibiotics were given to all patients. Tests for bacterial pathogens were negative for only one patient Table 3 . Four 80% of the five patients died. Among the four patients receiving venovenous ECMO, only one patient survived. The other four patients died due to ARDS, Aspergillus fumigatus coinfection, septic shock and catheter-related bloodstream infection due to Acinetobacter baumannii, respectively. To the best of our knowledge, this is the first cohort observational study on the clinical characteristics of patients with severe ARDS caused by emergent HAdV-55 infection and also the first on the evaluation of a viral load test for monitoring the reaction to therapy and for prediction of patient outcome. The other four patients died due to ARDS, Aspergillus fumigatus coinfection, septic shock and catheter-related bloodstream infection due to Acinetobacter baumannii, respectively. To the best of our knowledge, this is the first cohort observational study on the clinical characteristics of patients with severe ARDS caused by emergent HAdV-55 infection and also the first on the evaluation of a viral load test for monitoring the reaction to therapy and for prediction of patient outcome. The following are the main findings of this study. . HAdV-55 may cause severe ARDS in immunocompetent young men with blood type B. All of our patients were from the same city of Hebei province, northern China. . . HAdV-55 may cause severe ARDS in immunocompetent young men with blood type B. All of our patients were from the same city of Hebei province, northern China. . Persistent high fever, dyspnea and rapid progression to respiratory failure within 2 weeks, together with bilateral consolidations and infiltrates at the same time, are the most frequent clinical manifestations of severe HAdV-55induced ARDS. . Viral load monitoring may help predict disease severity and patient outcome. . The NPPV and IMV failure rates were very high, and ECMO may be the last support method for this group of patients. . HAdV-55-induced severe ARDS has a very high mortality rate 80% despite appropriate respiratory support. . HAdV-55-induced severe ARDS has a very high mortality rate 80% despite appropriate respiratory support. Sporadic severe adenoviral infection in healthy adults has historically been described for serotype 4 , serotype 7 and, more recently, serotype 14 in the general population and in military trainees . HAdV-55 was first completely characterized in Shaanxi, China and then reemerged in Hebei, a province close to Beijing, where it caused several cases of acute respiratory disease . It was presumed that HAdV-55 was a recombinant form of the B2 species of HAdV-14 and HAdV-11 due to its sharing a hexon gene with the HAdV-11 and HAdV-14 chassis . The results of our study show that HAdV-55, as an emerging pathogen among immunocompetent adults, may cause severe ARDS. It was presumed that HAdV-55 was a recombinant form of the B2 species of HAdV-14 and HAdV-11 due to its sharing a hexon gene with the HAdV-11 and HAdV-14 chassis . The results of our study show that HAdV-55, as an emerging pathogen among immunocompetent adults, may cause severe ARDS. The prevalence of severe fatal adenoviral pneumonia induced by HAdV-55 in our study is somewhat similar to that described by Cao and colleagues . All cases of reported HAdV-55 in our study were from the same city: Baoding, Hebei province, northern China. They occurred between April and July 2013, just partly overlapping or following the influenza epidemic. The patients with severe disease also came from the same region and were treated during a similar time period, which suggests that HAdV-55 may be an important viral pathogen derived from this region. They occurred between April and July 2013, just partly overlapping or following the influenza epidemic. The patients with severe disease also came from the same region and were treated during a similar time period, which suggests that HAdV-55 may be an important viral pathogen derived from this region. Our study results suggest that the following may be clinical features of ARDS caused by HAdV-55: persistent high fever, rapid progression of dyspnea, need for mechanical ventilation support, elevated AST level and rapid progression from unilateral infiltrates to bilateral consolidations. These clinical features are highly similar to those of ARDS caused by other types of HAdV described in previous reports . Recent studies have shown that the immune system plays a crucial role in the clearance of HAdV viremia and survival of the host . Chen et al. Recent studies have shown that the immune system plays a crucial role in the clearance of HAdV viremia and survival of the host . Chen et al. reported that, in the acute phase of HAdV-55 infection, patients with severe disease may have high levels of dendritic cells and Th17 cells . In our study, the only patient who recovered from severe infection had higher T-cell counts. Three of the five patients had relatively low T-cell counts when admitted. Our results suggest that these three patients may have been relatively immunocompromised and that a lower T-cell count may be a risk factor for HAdV-55 infection in young adults. Three of the five patients had relatively low T-cell counts when admitted. Our results suggest that these three patients may have been relatively immunocompromised and that a lower T-cell count may be a risk factor for HAdV-55 infection in young adults. HAdV-55 DNA was previously reported in 41.2% of patients with severe infection . In our study, HAdV-55 DNA was detected and monitored in all patients with severe ARDS. The initial, and trend of, viral load that presented as HAdV-55 DNA copies in the respiratory tract samples and blood may suggest the severity of infection and may predict both the reaction to therapy and patient outcome. The use of mechanical ventilation and ECMO in patients with ARDS caused by HAdV-55 has not been detailed in previous studies. The initial, and trend of, viral load that presented as HAdV-55 DNA copies in the respiratory tract samples and blood may suggest the severity of infection and may predict both the reaction to therapy and patient outcome. The use of mechanical ventilation and ECMO in patients with ARDS caused by HAdV-55 has not been detailed in previous studies. In our cohort, we found that severe HAdV-55 infection could cause a rapid progression of respiratory failure, with a very high failure rate for NPPV and IMV. This failure rate may be a result of the large area of consolidation that induced a severe shunt in the lung, which may lead to lack of response to positive pressure ventilation. For patients with severe ARDS, ECMO should be considered a better choice for oxygenation. Our study has limitations. For patients with severe ARDS, ECMO should be considered a better choice for oxygenation. Our study has limitations. It is an observational study with no comparison group, so the difference between the severe and modest infections could not be clarified in terms of immune status, clinical features, radiological findings, viral load and treatment effects on respiratory support and antiviral therapy. Sequential dynamic analysis is needed to determine the relationship between HAdV-55 viremia and treatment response.