Isolation and characterization of Puumala hantavirus from Norway: evidence for a distinct phylogenetic sublineage.

Puumala (PUU) hantavirus is the aetiological agent of nephropathia epidemica (NE), a mild form of haemorrhagic fever with renal syndrome, which occurs in Fennoscandia, central Europe and Russia. In Norway, NE-like disease has been reported since 1946 and about 50 cases are diagnosed annually; however, the causative agent has not been characterized. In this study, a virus originating from bank voles (Clethrionomys glareolus) trapped near the town of Eidsvoll (Akershus county) was isolated and passaged in laboratory-bred bank voles. The bank vole strain was identified as a PUU virus by serological typing and by sequence analysis of the S and M gene segments. For comparison, complete or partial S sequences were determined for wild-type PUU strains from five locations in Sweden, two inhabited by the southern variant of bank vole present in Fennoscandia, and three by the northern variant. Phylogenetic analysis showed that Norwegian PUU strains are clustered together with Swedish strains from the first group forming a well-supported sublineage within the PUU genotype, distinct from other sublineages from northern Sweden, Finland, Russia and France. The results are consistent with the view of a complex evolutionary history of PUU strains in post-glacial Fennoscandia. Analyses of the current collection of nucleotide sequences suggest that PUU is the most variable genotype of the known hantaviruses.

Serological diagnosis of hantavirus infections by an enzyme-linked immunosorbent assay based on detection of immunoglobulin G and M responses to recombinant nucleocapsid proteins of five viral serotypes.

Worldwide, hantaviruses cause more than 100,000 human infections annually. Rapid and accurate methods are important both in monitoring acute infections and for epidemiological studies. We and others have shown that the amino termini of hantavirus nucleocapsid proteins (Ns) are sensitive tools for the detection of specific antibodies in hantavirus disease. Accordingly, we expressed truncated Ns (amino acids 1 to 117) in Escherichia coli from the five hantaviruses known to be pathogenic to man; Hantaan (HTN), Seoul (SEO), Dobrava (DOB), Sin Nombre (SN), and Puumala (PUU) viruses. In order to obtain pure antigens for use in an enzyme-linked immunosorbent assay (ELISA), the recombinant proteins were purified by polyhistidine-metal chelate affinity chromatography. Polyclonal animal antisera and a panel of serum specimens from hantavirus-infected individuals from Scandinavia, Slovenia, Russia, Korea, China, and the United States were used to evaluate the usefulness of the method. With both human and animal sera, it was possible to designate the antibody response into two groups: those with HTN, SEO, and DOB virus reactivity on the one hand and those with SN and PUU virus reactivity on the other. In sera from Scandinavia, European Russia, and the United States, the antibody response was directed mainly to the PUU and SN virus group. The sera from Asia reacted almost exclusively with the HTN, SEO, and DOB types of viruses. This was true for both the immunoglobulin M (IgM) and IgG antibody responses, indicating that this type of discrimination can be done during the acute phase of hantavirus infections. Both the HTN, SEO, and DOB virus and the PUU and SN virus types of antibody response patterns were found in patients from the Balkan region (Solvenia).

[Early serological diagnosis of nephropathia epidemica]. / Tidlig serologisk diagnose av nephropathia epidemica.

The viral disease nephropathia epidemica is probably more common throughout Norway than previously reported. Since 1986, outbreaks of the disease have been registered every year but in different regions of the country. Very few cases have been reported in certain counties in spite of the presence of a small rodent reservoir for this zoonosis. Nephropathia epidemica may be underdiagnosed, since the disease is not equally well recognized in all parts of Norway. However, effective and reliable serological diagnostic tests are now available which use a single serum sample taken early in the acute phase of the disease. Test results are available at a time when they can help the physician to make an early diagnosis. This should lead to a more effective and rational treatment of these patients.

Haemorrhagic fever with renal syndrome: evaluation of ELISA for detection of Puumala-virus-specific IgG and IgM.

IgM and IgG ELISA to Puumala virus were evaluated using sera from patients with haemorrhagic fever with renal syndrome (HFRS) from different geographical regions: Sweden, Denmark, Norway, Belgium and the European USSR. IgM ELISA proved useful in the diagnosis of HFRS in patients from all the regions mentioned above. Specific IgM could be detected as early as day 1 post onset of disease, and patients remained IgM-positive for several months. Specific IgG ELISA antibodies were also frequently detected in acute sera, and acute-convalescent serum pairs often failed to show a significant titre rise or increase in optical density (OD) values. This limits the use of IgG ELISA in patient diagnosis. Sera collected 2 years after infection revealed higher IgG ELISA OD readings than convalescent sera, and very high values were still detectable 10 to 20 years postinfection. IgG ELISA is therefore useful for the testing of immunity and in seroepidemiological studies. Acute and convalescent sera from HFRS patients in Korea and the Asian USSR showed no or only very weak reactivity in the Puumala virus IgG and IgM ELISA. These results are consistent with the "one-way" crossing described earlier.

The potency determination of human varicella-zoster immunoglobulin by enzyme-linked immunosorbent assay, complement-fixation test and indirect fluorescent antibody tests.

Traditionally, plasma for the production of the human varicella-zoster immunoglobulin (VZIG) has been selected on the basis of the complement-fixing antibody (CFA) titre. Since immune individuals may lack CFA to varicella-zoster virus (VZV), non-CFA may be of importance in protection. In a search for a simple and reliable method for potency determination, 24 VZIG preparations were quantified by enzyme-linked immunosorbent assay (ELISA), the complement-fixation test (CFT), the indirect fluorescent antibody test to acetone-fixed (IF) and viable (FAMA) VZV-infected cells, respectively. The antibody titres obtained by the various methods were compared. Arranged in order of decreasing agreement, the correlation coefficients (r) of the regression equations between the variables were 0.62 for CFT and FAMA, 0.50 for CFT and ELISA and 0.26 for CFT and IF in a log2 plot. There was complete agreement between the titres obtained by the commercially available Enzygnost Varicella/Zoster kits (Behring Institute, Marburg, F.R. Germany) and the ELISA microtitre plates produced at our institute (r = 1). The regression equation lines for ELISA/CFT and FAMA/CFT titres tended to be parallel to each other, while the line for IF/CFT titres had a less steep slope. Similar titration curves were obtained for VZIGs fractionated by two different methods. Furthermore, the titration curves of serum pools from varicella and zoster convalescents, respectively, had a similar shape below delta OD = 0.4. Generally, a steeper slope was observed above delta OD = 0.4. As antibody detectable by ELISA seems to correlate with protection and the method is sensitive, specific, reproduceable, simple to carry out and easily automated, it may be suitable for the potency determination of VZIGs.

Binding site and subclass specificity of the herpes simplex virus type 1-induced Fc receptor.

Immunoglobulin Fc-binding activity was detected by indirect immunofluorescence employing fluorochrome conjugated F(ab')2 antibody fragments on acetone-fixed cell cultures infected with herpes simplex virus type 1 (HSV-1). Using this method the Fc receptor-like activity seemed to be restricted to the IgG class of human immunoglobulins. While IgG1, IgG2, and IgG4 myeloma proteins bind to this putative Fc gamma receptor at a concentration of 0.002 mg/ml, IgG3 myeloma proteins were without activity at 0.1 mg/ml. The binding activity was associated with the Fc fragments of IgG, while the pFc' fragments of IgG appeared to be unable to bind in this assay system. The reactivity and specificity of the HSV-1 Fc receptor was independent of both the type of tissue culture cells used and the strain of HSV-1 inducing the Fc receptor-like activity. The HSV-1-induced Fc receptor has a similar specificity for human immunoglobulin class and subclasses as staphylococcal Protein A. However, these two Fc receptors exhibit at least one striking difference. The IgG3 G3m(st) protein which binds to Protein A does not bind to HSV-1-induced Fc receptor. A possible reaction site for the HSV-1 Fc receptor on IgG could be at or near Asp 276.

Vaccination of children with malignant disease against varicella.

Nineteen seronegative children and one young adult with malignant disease in remission and on maintenance chemotherapy were immunized with the Oka-strain live attenuated varicella vaccine (Varilrix). Side effects were moderate and a rash was seen in 50% of the patients after vaccination. Humoral immune response to the vaccine was tested by the fluorescent antibody to membrane antigen (FAMA) test, a simpler indirect immunofluorescence test (IFT), and an enzyme-linked immunosorbent assay (ELISA). The seroconversion rate after immunization varied according to the method used. Seven out of 8 responded by FAMA, 15 out of 20 by IFT, and 12 out of 20 by ELISA. A decline in post-vaccination varicella-zoster virus (VZV) antibodies was seen in some responders. In 2 children, detectable levels of passively transferred VZV antibodies at the time of vaccination, due to varicella-zoster immune globulin, may have interfered with or modified the response to the vaccine. Cross-reacting antibodies to herpes simplex virus may have possibly interfered with vaccine response in a third child. Six out of 8 children receiving a second vaccine dose showed a good serological response. Specific cell-mediated immune response to the vaccine, measured by lymphocyte proliferation tests, corresponded well with the humoral response in the initial study of 8 patients. Two children who had responded to the vaccine were exposed to varicella in their families without contracting the clinical disease.

Demonstration of anti-rubella antibody-secreting cells in rheumatoid arthritis patients.

In the present study we describe a plaque-forming cell assay using erythrocytes coated with viral antigen, which detected anti-viral antibody-secreting cells against various viral antigens. These anti-viral antibody-secreting cell were studied in normal individuals with known viral infections and in rheumatoid arthritis patients. Rubella anti-viral antibody-secreting cells were present after induction in the peripheral blood of eight out of ten patients. No plaques were seen before induction. Synovial tissue of seven patients out of ten showed rubella-antigen-specific plaques before induction. In all three patients tested, the numbers of plaques increased after induction. The peripheral blood of only one patient showed plaque-forming cells against mumps virus and cytomegalovirus (CMV) antigen. No other patients showed any plaque against CMV, respiratory syncytial virus, mumps virus, measles virus, adenovirus, and varicella zoster virus antigens. The method appears to be promising in studying viral antibody-secreting cells in human immunopathology.

IgG1 subclass restriction of oligoclonal IgG from cerebrospinal fluids and brain extracts in patients with multiple sclerosis and subacute encephalitides.

Oligoclonal-IgG-containing cerebrospinal fluids (CSF) from patients with multiple sclerosis and subacute encephalitides were studied for IgG subclass distribution by immunoelectrophoretic and hemagglutination inhibition methods. The immunoelectrophoretic results indicated the presence of electrophoretically restricted IgG1 proteins in a number of CSF, compatible with an association between this IgG subclass and oligoclonal IgG proteins. The combined results indicated a greater dominance of IgG1 over other IgG subclass proteins in CSF than in matching sera. Similar results were obtained in experiments with brain extracts from patients with subacute sclerosing panencephalitis. The results differed from those obtained with normal CSF, where the distribution of IgG subclasses resembled that of the matching sera. It is concluded that the oligoclonal IgG of the CSF and brain in the patients studied belong mainly to the IgG1 subclass.

Morphological features in the peripheral blood film indicating the presence of cryoproteins.

Light gray, irregular threads in a May-Grünwald & Giemsa stained blood film made of EDTA-blood some time after drawing may sometimes call attention to a previously unsuspected cryoproteinaemia. The cryoproteinaemia discovered in this way in our patient consisted of IgG complexes resulting in proteinuria. After treatment with prednisone and cyclophosphamide the cryoproteinaemia and proteinuria disappeared.