Therese Popow-Kraupp

Single versus dual respiratory virus infections in hospitalized infants : Impact on clinical course of disease and interferon-γ response

Background: Dual respiratory viral infections are frequently associated with lower respiratory tract illness in infants. This study aimed to determine the impact of a dual respiratory viral infection on specific aspects of the infants immune response and the clinical course of illness. Methods: A prospective study was performed with 772 infants hospitalized from October 2000 through July 2004. Sensitive polymerase chain reaction methodology revealed the presence of a single respiratory virus in 443 (57%) of 772 cases, whereas dual infections were identified in 153 (20%) of cases. From 250 infants with confirmed respiratory viral infection, fresh heparinized blood was analyzed for interferon-γ (IFN-γ) responses by flow cytometry. Of these, 191 patients had a single infection with respiratory syncytial virus (RSV), rhinoviruses, adenoviruses or influenza viruses; and 59 patients had a dual infection with RSV and rhinoviruses, RSV and adenoviruses, influenza viruses and rhinoviruses or adenoviruses and rhinoviruses. The clinical features and peripheral lymphocyte IFN-γ responses were compared among infants with single or dual infections. Results: It was found that dual infections with non-RSV respiratory viruses induced peripheral blood mononuclear cell IFN-γ responses that mimic those of single infections, whereas coinfection with RSV was associated with reduced IFN-γ responses and a more severe clinical course of lower respiratory tract disease. Conclusions: The results indicate that the clinical characteristics and the IFN-γ response differ significantly in single and dual respiratory viral infection, depending on the nature of the simultaneously detected viruses. In dual infections, RSV involvement was associated with a decreased IFN-γ response in peripheral blood mononuclear cell and an increase in severity of illness.

Recurrent granulocytic aplasia as clinical presentation of a persistent parvovirus B19 infection

Summary. We report a case of persistent infection with human parvovirus B19 (PVB19), manifesting clinically as recurrent agranulocytosis and in bone marrow biopsy as recurrent pure granulocytic aplasia. Persistence of parvovirus infection was documented by the presence of PVB19 DNA and anti‐PVB19‐IgM antibodies in the serum for a period of 19 months. Granulocytic aplasia occurred only when anti‐PVB19‐IgG antibodies were not detectable in the serum and granulopoiesis showed immediate recovery with high dose intravenous immunoglobulin treatment. This case report suggests that the erythroid precursor cell may not be the only target cell of PVB19 infection. We suggest testing for active parvovirus infection in cases of aplasia of any lineage of the haematopoietic system.

Emergence of Multiple Cytomegalovirus Strains in Blood and Lung of Lung Transplant Recipients

Background. Cytomegalovirus (CMV) is a major pathogen in lung transplant recipients (LTRs). The emergence of different CMV strains in lung and blood after transplantation has not yet been analyzed. Methods. In total, 75 serum and 91 broncheoalveolar lavage (BAL) samples obtained from 25 LTRs in the follow-up after transplantation were tested for the presence of different CMV strains. The gB, gN, and gO genes of the CMV isolates were analyzed by subtype-specific PCR, restriction fragment length polymorphism (RFLP), sequencing, and phylogenetic analysis. Results. Mixed CMV-strain populations were detected after cessation of antiviral prophylaxis in up to 80% and 90% of the patients’ BAL and serum, respectively, and this was independent of the CMV serostatus of donor and recipient. In five patients, the same single CMV strain was consistently detectable over at least 1 year in lung and blood, although in two of these cases donor and recipient had both been CMV-seropositive. Most CMV strains were distributed in the lung and blood compartment. Symptomatic CMV infection within the first year after transplantation was observed only in patients with mixed CMV-strain populations (P<0.05). Conclusion. Most LTRs harbor more than one CMV strain in their lung and blood compartment after cessation of prophylaxis, but the CMV strain distribution within and between the compartments varies between individuals and is not associated with the donor/recipient serostatus. The data further show that compartmentalization of CMV strains in lung versus blood seems to be a rare event and that the presence of mixed CMV-strain infections within the first year after transplantation may be disadvantageous for LTRs.

Improved detection of respiratory syncytial virus in nasal aspirates by seminested RT-PCR

A seminested RT‐PCR for amplification of Respiratory syncytial virus (RSV)‐RNA in nasal aspirates has been developed and used to test nasopharyngeal aspirates (NPAs) from 132 infants hospitalized with acute respiratory tract infections during winter epidemics. The results were compared with those obtained by virus isolation in tissue culture and antigen detection with an enzyme‐linked immunosorbent assay (Ag‐ELISA). RSV‐RNA was detected by seminested RT‐PCR in 57 of the 59 samples that were positive by virus isolation and/or ELISA, as well as in 25 of 73 samples negative by virus isolation and ELISA. Eighteen of these 25 samples were obtained from children older than one year of age, 17 of whom were experiencing reinfection, as indicated by the presence of preexisting serum RSV‐IgG antibodies. These results indicate that seminested RT‐PCR is more sensitive than conventional methods for the detection of RSV in patients experiencing reinfections and suggest that this assay might also be useful for rapid diagnosis of RSV infections in older people. J. Med. Virol. 53:366–371, 1997.

Clinical Manifestations of Respiratory Tract Infections due to Respiratory Syncytial Virus and Rhinoviruses in Hospitalized Children

ABSTRACT. From September 1984 to May 1986, nasopharyngeal secretions were obtained from 519 children with some form of respiratory tract infection. The nasal secretions were screened for respiratory syncytial virus (RSV), rhinoviruses, adenoviruses, parainfluenza virus types 1, 2,3, influenza virus types A and B, and enteroviruses by tissue culture virus isolation technique and/or enzyme‐linked immunosorbent assay. A uniform questionnaire gave information about age, sex, individual signs and symptoms, findings of the physical examination and clinical diagnosis of the patients. RSV was detected in 119 (23%) specimens and was thus the most frequent causative agent of respiratory infections. After RSV, rhinoviruses were the most frequently recovered pathogens accounting for 60 (12%) cases of acute respiratory disease. A comparison of the individual signs and symptoms, the findings of the physical examination and the clinical diagnosis of RSV and rhinovirus infected children revealed that there was no characteristic clinical pattern associated with either of the two viral respiratory pathogens. According to our results, rhinovirus infections were a major cause of lower respiratory tract infections in hospitalized children ≤3 years old.

Human metapneumovirus subgroup changes and seasonality during epidemics.

Background: Human metapneumovirus (HMPV) is a major cause of respiratory tract illness in young children and causes annual outbreaks in winter and spring seasons. We evaluated the subgroups of HMPV that caused annual outbreaks and its seasonal occurrence during a 21-year period. Methods: Real-time PCR was used for detection of HMPV in 3576 nasopharyngeal aspirates that had been continuously collected year-round for the years 1987 to 2008 from infants hospitalized with acute respiratory tract illness. Phylogenetic analysis was used to assess HMPV subgroups. Results: Of the 3576 samples obtained, 202 (5.6%) tested positive for HMPV. All known HMPV subgroups (A1, A2a, A2b, B1, B2) could be identified as important respiratory tract pathogens in infants. We found that one HMPV subgroup predominated each year, and it was displaced by another subgroup every 1 to 3 years. Besides the frequent change in predominant HMPV subgroups, we observed a yearly shift in the seasonal occurrence, with a strong peak of HMPV activity in late spring-summer months every second year. Conclusion: HMPV activity is characterized by a periodic change in the predominant subgroup and it shows a stable seasonal rhythm of alternating winter and spring activity.

Biennial spring activity of human metapneumovirus in Austria.

Background: Human metapneumovirus (HMPV) is considered an important respiratory pathogen in young children. To gain insight into the seasonality and epidemiologic characteristics of HMPV infection, this study determined the frequency of HMPV infections in hospitalized infants during a 7-year period. Methods: By use of real-time reverse-transcriptase polymerase chain reaction, nasopharyngeal aspirates from 1612 infants less than 2 years of age who were hospitalized for acute respiratory tract illness were tested for the presence of HMPV. Weekly HMPV testing data were analyzed to assess the timing of HMPV activity. Season variability was estimated by comparing the onset, duration, peak, and end of outbreaks from October 2000 through October 2007. Results: Overall, 109 (6.8%) of 1612 cases of acute respiratory illness were associated with HMPV infection. Seasonal HMPV activity varied substantially from year to year, both in prevalence rates of HMPV cases and in seasonal timing of outbreaks. HMPV activity was characterized by a biennial rhythm, with spring seasons occurring every second year, and these accounted for a substantial proportion, up to 30%, of hospitalized cases of acute respiratory tract illness. Conclusions: HMPV activity varies substantially from year to year, both in the frequency and timing of illness and shows a biennial pattern of alternating winter and spring activity.

Diagnosis of Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is one of the most important pathogen causing severe lower respiratory tract infections in all age groups often requiring hospitalization. Rapid laboratory diagnosis of RSV infection significantly decreases the use of antibiotics, additional laboratory testing and is associated with shorter hospitalization periods. The specific diagnosis of RSV infection is based on the detection of virus or viral antigens or virus specific nucleic acid sequences in respiratory secretions. The kind and quality of the clinical specimen exerts a considerable influence on the results of all currently used viral detection assays. Antigen based tests are widely available, easy to perform and the results are available in a short time but their reduced sensitivity and specificity represent a considerable shortcoming. Among the methods available isolation in cell culture was considered the gold standard for the sensitive identification of RSV but is gradually replaced by highly sensitive and specific nucleic acid amplification assays that provide more rapid results. Of these reverse transcription polymerase chain reaction (PCR) was the first and is still the most frequently used nucleic acid-based assay. New methodologies, as for example the real-time PCR methods allow the quantification of viral nucleic acids in the clinical sample. Disadvantages of the nucleic acid based assays are their high costs and their limited standardization. Future research on new methodologies for the diagnosis of viral respiratory tract infections should focus on the development of sensitive, rapid and cost effective test systems allowing the screening for all probable causative agents. In addition varying testing protocols for summer and winter months based on epidemiologic data are needed to direct their practical use.

Adenovirus DNA in Serum of Children Hospitalized Due to an Acute Respiratory Adenovirus Infection

Serum samples from 68 immunocompetent infants (mean age, 12.6 months) with an acute adenovirus infection of the respiratory tract (39 experiencing their first adenovirus infection) were tested for the presence of adenovirus DNA, to investigate whether viral dissemination via the blood is usually present in the immunocompetent patient. Using a nested polymerase chain reaction assay, adenovirus DNA could be detected in acute-phase serum samples from 28 (41%) children. Adenovirus DNA was never found in follow-up serum samples, indicating a short period ( approximately 1 week) of viral dissemination. In children experiencing their first adenovirus infection, viral DNA could be detected in 72% of the acute-phase serum samples collected within the first week after onset of symptoms. Adenovirus DNA could also be detected in 25% of the acute-phase serum samples from patients with reinfection.

Rabies and Herpes simplex virus encephalitis

A retrospective study on the frequency, site and distribution of rabies and Herpes simplex virus (HSV) type 1 antigens by means of immunofluorescence (IF) and immunoperoxidase (IP) techniques was performed on routinely processed (formol-fixed, paraffin-embedded) brain autopsy material stored for up to 25 years. In 2 animal and 2 human rabies cases, inclusion bodies in neuronal cytoplasm and processes were brilliantly stained for rabies antigens by IF but were much less prominent or absent in usual histological stains. In 33 cases of histopathologically diagnosed necrotizing encephalitis, HSV antigens were demonstrated in 18 of 26 acute cases; 7 subacute cases (course longer than 4 weeks) were all negative for HSV antigens. Neuronal cytoplasm and nuclear membranes were the main sites of HSV antigens; nuclear inclusion bodies were inconstantly stained. Since most of HSV antigen negative cases also showed intranuclear inclusion bodies in HE stains, such nuclear inclusions are no reliable criterion for an HSV aetiology. On the other hand, their absence does not rule out a herpetic aetiology, but such a constellation is rare (only one of 18 HSV positive cases). Distribution of cells showing a positive reaction for HSV antigens may be patchy and irregular; therefore, a false negative result must be expected if very small tissue samples are examined (e.g, in needle biopsies from temporal lobe). In the leptomeninges, HSV antigen positive cells were found inconstantly and only in small numbers; this finding makes unlikely the possibility of an intravital diagnosis of HSV encephalitis by immunostaining of cerebrospinal fluid (CSF) cell preparations. Both immunohistological techniques applied in this study (IF and IP) gave the same results. Imprint preparations are useful when quick diagnosis is necessary. Immunohistological investigations are a simple and effective means to demonstrate a viral aetiology even in routinely processed material; the use of such material rules out hazards in laboratories which are not designed to handle highly infectious fresh material.