Molecular characterization of a nosocomial outbreak of influenza B virus in an acute care hospital setting.

AIM: To describe a hospital outbreak of influenza B virus (InfB) infection during season 2015/2016 by combining clinical and epidemiological data with molecular methods. METHODS: Twenty patients diagnosed with InfB from a hospital outbreak over a four-week-period were included. Nasopharyngeal samples (NPS) positive for InfB by multiplex real-time polymerase chain reaction were sent for lineage typing and whole genome sequencing (WGS). Medical records were reviewed retrospectively for data regarding patient characteristics, localization, exposure and outcome, and assembled into a timeline. In order to find possible connections to the hospital outbreak, all patients with a positive NPS for influenza from the region over an extended time period were also reviewed. FINDINGS: All 20 cases of InfB were of subtype B/Yamagata, and 17 of 20 patients could be linked to each other by either shared room or shared ward. WGS was successful or partially successful for 15 of the 17 viral isolates, and corroborated the epidemiological link supporting a close relationship. In the main affected ward, 19 of 75 inpatients were infected with InfB during the outbreak period, resulting in an attack rate of 25%. One probable case of influenza-related death was identified. CONCLUSION: InfB may spread within an acute care hospital, and advanced molecular methods may facilitate assessment of the source and extent of the outbreak. A multi-faceted approach, including rapid diagnosis, early recognition of outbreak situations, simple rules for patient management and the use of regular infection control measures, may prevent nosocomial transmission of influenza virus.

Age-specific differences in influenza virus type and subtype distribution in the 2012/2013 season in 12 European countries.

The epidemiology of seasonal influenza is influenced by age. During the influenza season, the European Influenza Surveillance Network (EISN) reports weekly virological and syndromic surveillance data [mostly influenza-like illness (ILI)] based on national networks of sentinel primary-care providers. Aggregated numbers by age group are available for ILI, but not linked to the virological data. At the end of the influenza season 2012/2013, all EISN laboratories were invited to submit a subset of their virological data for this season, including information on age. The analysis by age group suggests that the overall distribution of circulating (sub)types may mask substantial differences between age groups. Thus, in cases aged 5-14 years, 75% tested positive for influenza B virus whereas all other age groups had an even distribution of influenza A and B viruses. This means that the intepretation of syndromic surveillance data without age group-specific virological data may be misleading. Surveillance at the European level would benefit from the reporting of age-specific influenza data.

Does viral interference affect spread of influenza?

This short communication hypothesises that rhinovirus epidemics occurring after start of school may interfere with the spread of influenza during the period when warm and humid climate decreases the influenza spread by aerosol. Limited laboratory data supporting this hypothesis are included in the article, but the report is written mainly to stimulate interest and research concerning the possibility that viral interaction may affect influenza epidemiology.

Effectiveness of ganciclovir against human herpesvirus-6 excreted in saliva in stem cell transplant recipients.

The aim of this study was to evaluate the effect of ganciclovir on human herpesvirus-6 (HHV)-6. Forty allogeneic stem cell transplant recipients were prospectively studied by repeated sampling of the saliva. The saliva samples were assayed for HHV-6 by quantitative polymerase chain reaction. HHV-6 was detected in 33 patients. Ganciclovir was given as preemptive therapy for cytomegalovirus infection during 15 episodes that were compared to 18 episodes without any concomitant antiviral therapy. The mean HHV-6 load decreased 0.49 (s.e. 0.31) log(10)/week in patients receiving ganciclovir whereas it increased 0.15 (s.e. 0.17) log(10)/week in episodes without antiviral therapy (P=0.04). We conclude that ganciclovir can decrease the HHV-6 viral load in saliva.

Human cell lines used in a micro neutralization test for measuring influenza-neutralizing antibodies.

An in situ neutralization test (NT) including ELISA for the measurement of influenza antigen was developed and evaluated. Two human cell lines, fibroblasts (HS27) cells and salivary gland epithelial duct (HSG) cells, were compared with Madin-Darby Canine Kidney (MDCK) cells. The viral production in the human cell lines was lower than that for MDCK cells, which influenced the results of the assay in the HSG and HS27 cells. However, when lowering the infectious dose, the NT using HS27 cells gave a sensitive and stable assay with low background in the ELISA. The NT titres were very low when using HSG cells compared to MDCK cells. The HS27 NT was used to analyze the humoral response after an influenza A infection in patients from a placebo-controlled zanamivir study. We found no differences in NT titres between patients treated with zanamivir or placebo. The MDCK and HS27 NT gave higher titres and more pronounced titre differences than the gold standard haemagglutinin inhibition (HAI) assay. Compared to the HAI assay, the sensitive NT using HS27 cells also revealed heterologous NT-titre rises after influenza infection in the patients.

Variations in the cytomegalovirus DNA polymerase and phosphotransferase genes in relation to foscarnet and ganciclovir sensitivity.

BACKGROUND: Identification of human cytomegalovirus (CMV) genome variation is important for understanding mutations associated with drug resistance. OBJECTIVES: To investigate the CMV resistance to foscarnet (PFA) and ganciclovir (GCV) in patients treated with antiviral drugs and to identify the DNA polymerase (UL54) and phosphotransferase (UL97) gene mutations inducing resistance. STUDY DESIGN: Antiviral susceptibility of CMV strains/isolates for PFA and GCV was compared by plaque reduction assay and in situ ELISA. UL54 and UL97 gene mutations were identified by sequencing. Growth phenotype of two CMV recombinants with mutations in UL54 was studied. RESULTS: Six of seven GCV resistant strains had alterations within the UL97. Five of them also had alterations in the UL54 (F412C, L802M or K513E), previously shown to induce GCV resistance. Seven isolates had no or reduced susceptibility to PFA, which had alterations in the UL54 (D588N, E756K, V781I or L802M). By in vitro mutagenesis, it was shown that a mutation at codon D588N of UL54 conferred 9-fold reduced susceptibility to PFA, while a mutation at codon V781I induced 4-fold reduced susceptibility to PFA and GCV. Both recombinants showed the same kinetics of protein expression (IE, E, and L antigen) and virus yields as the CMV Towne strain. CONCLUSIONS: The recombinants containing alterations within the UL54 (D588N and V781I) showed a reduced susceptibility to antiviral drugs but no change in the replication rate compared to the CMV Towne.

Sequence analysis of UL54 and UL97 genes and evaluation of antiviral susceptibility of human cytomegalovirus isolates obtained from kidney allograft recipients before and after treatment.

The frequency of infections caused by drug-resistant cytomegalovirus (CMV) in solid-organ transplant recipients is not known. Only a few resistant strains have been described in transplant recipients. Antiviral susceptibility to ganciclovir (GCV) and foscarnet (PFA) of CMV isolates from 24 renal transplant patients with CMV viremia and CMV disease before and after therapy were investigated by a solid phase ELISA. The CMV DNA polymerase (UL54) and viral phosphotransferase (UL97) genes were also sequenced. Ten patients did not receive antiviral treatment; five and nine patients were treated with PFA and GCV, respectively. No appearance of drug-resistant viruses was observed in the present study, but one isolate showed a reduced sensitivity to PFA after treatment with GCV. This finding could not be explained by the presence or development of mutations that have been associated with drug resistance in UL54. We found no evidence that short-term treatment of CMV with PFA- or GCV-induced resistance.

Growth phenotypes of cytomegalovirus isolates do not correlate with glycoprotein B, major immediate early genotypes or antiviral sensitivity.

Human Cytomegalovirus (CMV) is generally described from in vitro experiments as a slowly replicating virus. A doubling time of one day in blood, however, has been shown in vivo. The growth phenotypes of CMV isolates and laboratory strains were studied in human fibroblasts. The viruses were found to replicate either rapidly or slowly. Comparison of CMV protein expression in lung and foreskin fibroblast cultures showed that two tissue culture adapted CMV strains (AD169 and Towne) and 3 clinical isolates belonged to the rapidly replicating viruses, whereas another 3 clinical isolates replicated slowly. CMV antigen concentrations were 6-fold and virus yields were 10-1000-fold higher for the rapidly replicating viruses than for the slow replicators. The antigen expression of two slowly replicating isolates was enhanced after 20 passages compared to the isolates at passage 5, but it was not as efficient as that of strain Towne. Slow or fast replication was related neither to major immediate early gene exon 4, and gB genotypes, nor to antiviral susceptibility. Proteins of the beta cascade may contribute to differences in the replication rate of CMV isolates.

Human cytomegalovirus strain-dependent changes in NK cell recognition of infected fibroblasts.

NK cells play a key role in the control of CMV infection in mice, but the mechanism by which NK cells can recognize and kill CMV-infected cells is unclear. In this study, the modulation of NK cell susceptibility of human CMV (hCMV)-infected cells was examined. We used a human lung and a human foreskin fibroblast cell line infected with clinical isolates (4636, 13B, or 109B) or with laboratory strains (AD169, Towne). The results indicate that all three hCMV clinical isolates confer a strong NK resistance, whereas only marginal or variable effects in the NK recognition were found when the laboratory strains were used. The same results were obtained regardless of the conditions of infection, effector cell activation status, cell culture conditions, and/or donor-target cell combinations. The NK cell inhibition did not correlate with HLA class I expression levels on the surface of the target cell and was independent of the leukocyte Ig-like receptor-1, as evaluated in Ab blocking experiments. No relevant changes were detected in the adhesion molecules ICAM-I and LFA-3 expressed on the cell surface of cells infected with hCMV clinical and laboratory strains. We conclude that hCMV possesses other mechanisms, related neither to target cell expression of HLA-I or adhesion molecules nor to NK cell expression of leukocyte Ig-like receptor-1, that confer resistance to NK cell recognition. Such mechanisms may be lost during in vitro passage of the virus. These results emphasize the differences between clinical hCMV isolates compared with laboratory strains.

Prevalence of parvovirus B19 DNA in bone marrow of patients with haematological disorders.

Patients with haematological disorders (n = 100) were examined for prevalence of parvovirus B19 DNA in the bone marrow and serum, irrespective of B19-related symptoms. B19 DNA was studied using 2 nested PCRs and the serum samples were further analysed with B19-specific IgG, IgM and avidity as well as seroreactivity against linear and conformational epitopes of the B19 VP2 antigen. The latter assays specify whether the IgG antibody response represents acute or past B19 infection. B19 DNA was detected in 4 of the 100 bone marrow samples, whereas all the serum samples were B19 DNA negative. None of the 4 B19 DNA positive patients had symptoms typical of B19 infection and serology showed past infection. Furthermore, 2 were still B19 DNA positive in bone marrow more than 1 y after the first sample indicating virus persistence. The seroprevalence for B19 IgG was 59% and 2 patients were B19 IgM positive. Thus, presence of B19 DNA in bone marrow from patients with haematological disorders is not a general finding in seropositive patients. B19 DNA can persist in bone marrow, but in our material this finding showed no clear correlation with symptomatic B19 infection.

Solid phase ELISA for determination of the virus dose dependent sensitivity of human cytomegalovirus to antiviral drugs in vitro.

The main problems in determining the true in vivo susceptibility of human cytomegalovirus (CMV) to antiviral compounds are the influence of the size of the viral inoculum, the variation in the replication capacity of different CMV strains and the subjective evaluation of the inhibition of viral growth in the plaque assay. In this study, a specific assay was developed which reproducibly determines the sensitivity of primary isolates of CMV. The assay includes simultaneous virus titration and determination of the antiviral sensitivity. When individual virus doses were evaluated, the IC50 was generally dependent on the virus dose, except for resistant isolates, where the IC50 did not change irrespective of the dose of virus. The novel method of IC50 calculation takes into account all values derived from the linear part of the inhibition curve. This may better reflect the in vivo conditions, where the antiviral drug encounters different amounts of virus in different organs. Two human fibroblast-derived cell lines showed similar results.

Sequence variation within three important cytomegalovirus gene regions in isolates from four different patient populations.

We determined the nucleotide (nt) and amino acid (aa) heterogeneities of three distinct regions of the human cytomegalovirus (CMV) genome for 46 low-passage CMV isolates from four different patient populations (congenitally infected infants, children attending day-care centers, renal transplant recipients, and human immunodeficiency virus-infected individuals) and for two laboratory strains (CMV Ad169 and Towne). The gene regions for the major immediate-early (MIE) exon 4 gene (nt positions 1702 to 1982, aa positions 152 to 244), the DNA polymerase gene (nt positions 2797 to 3046, aa positions 713 to 795), and the glycoprotein B (gB) gene (nt positions 1698 to 1884, aa positions 567 to 628) were sequenced. The sequence information was used to design sets of nested PCR primers directed against the most highly conserved regions identified. MIE was the most variable gene region compared to the variability of the DNA polymerase and gB gene regions. Comparison of the sequences of all 46 isolates with that of Ad169 revealed nt and aa sequence homologies of 87.9 and 87.2%, respectively, within the MIE gene compared to 92.8 and 100% homologies, respectively, within the DNA polymerase gene and 93 and 95.2% homologies, respectively, within the gB gene. Within the MIE gene, compared to the Ad169 nt sequence the homology at the nt level among isolates obtained from children attending day-care centers was high (96.4%), while it was lower (90%) among isolates obtained from the other three patient populations. Preliminary results of a nested PCR with oligonucleotide primers selected from the DNA polymerase gene region with a low level of nt sequence variation indicates that primers selected from this region might be more powerful for use in PCR than primers selected from the MIE gene region.

Shedding of cytomegalovirus and herpesviruses 6, 7, and 8 in saliva of human immunodeficiency virus type 1-infected patients and healthy controls.

We used the polymerase chain reaction to study the presence of DNA from cytomegalovirus (CMV) and human herpesvirus (HHV)-6, HHV-7, and HHV-8 in saliva from 44 human immunodeficiency virus (HIV) type 1-infected patients at different stages of disease and in 15 healthy HIV-seronegative controls. CMV DNA, HHV-6 DNA, and HHV-7 DNA were found in all groups, but HHV-8 DNA was found only in symptomatic HIV-1-infected patients (5 [17%] of 29). One of the patients with HHV-8 DNA in saliva had oral Kaposi's sarcoma at the time of sampling, and another later developed the tumor. CMV DNA was found most often in the patients with AIDS. HHV-6 shedding tended to be less frequent among HIV-1-infected patients than among healthy controls. HHV-7 DNA was detected least frequently in the group of patients with AIDS. The presence of viral DNA was not correlated either with antiherpesvirus drug therapy or with oral symptoms, apart from Kaposi's sarcoma.

Infrequent detection of cytomegalovirus and Epstein-Barr virus DNA in synovial membrane of patients with rheumatoid arthritis.

OBJECTIVE: To study the role of the cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex virus types 1 and 2 (HSV-1 and 2), varicella zoster virus (VZV), and human herpes virus 6 (HHV-6) in the etiology of rheumatoid arthritis (RA). METHODS: Polymerase chain reaction (PCR) was used to detect DNA of the different herpes viruses in synovial membranes from 31 patients with chronic RA and 14 control patients. Specific antibodies were determined by indirect immunofluorescence and ELISA. RESULTS: Out of 31 patients with RA, CMV DNA was detected in synovial membranes from 2 patients and EBV DNA was detected in synovial membranes from 2 other patients. All samples from the patients with RA were negative for DNA from HSV-1 and 2, VZV, and HHV-6. All samples from the 14 control patients were negative in all PCR assays. No statistically significant differences in IgG antibodies were found for CMV, HSV-1, VZV, and HHV-6 in patients with RA compared to controls. Higher titers of IgG antibodies against EBV viral capsid antigen were found in patients with RA, with a significance of p < 0.05. CONCLUSION: Both CMV and EBV DNA were detected in synovial membranes from 6% of the patients with RA. We cannot exclude the possibility that these viruses were associated with disease development in a minority of patients with RA.

DNA increases the potency of vaccination against infectious diseases.

In the past couple of years, the idea that naked DNA can be used to vaccinate against infections has been rapidly developing. In contrast to traditional protein or live attenuated vaccines, there is no risk of disease caused by DNA vaccines as only selected proteins are encoded. The ease with which DNA may be manipulated means that vaccines can be custom designed to meet many needs. In animal model systems, DNA vaccines have proved to be as effective as traditional vaccines. Additionally, this technology may also be used to control existing chronic infections. Possibilities for treating hepatitis B, herpes simplex virus-2 and HIV, as well as infections with parasites, are being explored with success.

Recognition of prominent viral epitopes induced by immunization with human immunodeficiency virus type 1 regulatory genes.

Mice immunized with the regulatory genes nef, rev, and tat from human immunodeficiency virus type 1 developed both humoral and cellular immune responses to the gene products Nef, Rev, and Tat. This study demonstrates that it is feasible to induce immune reactions to all of these regulatory gene products. Humoral responses were seen after DNA boosts, while potent T-cell proliferative responses were noted already after a single immunization. A Th1-directed immune response was demonstrated early after immunization. A 3- to 75-fold-stronger T-cell response was seen in animals receiving DNA epidermally compared to that in animals receiving intramuscular injections. Nef, Rev, and Tat putative B- and T-cell epitopes were clearly mapped by using peptides derived from the regulatory proteins and were similar to those which are detected in human immunodeficiency virus infection. Although immunization by the Nef, Rev, and Tat proteins raised high immunoglobulin G titers in serum, the epitope spreading appeared broader after DNA immunization. The combination of all of these regulatory genes together with two genes for structural proteins, the envelope and gag genes, demonstrated that a combined approach is feasible in that reactivities to all antigens persisted or were even augmented. No interference between plasmids was noted.