Aimo Salmi

Structure of the mengo virion V. Distribution of the capsid polypeptides with respect to the surface of the virus particle

Abstract The disposition of the Mengo capsid polypeptides (α, β, γ, and δ) with respect to the external surface of the virion has been investigated by measuring their relative susceptibilities to lactoperoxidase-catalyzed iodination and their reactivities in immunological tests with specific antisera. When intact virions were subjected to iodination for a brief period of time (1 min), radioactive iodine was incorporated predominantly into the a polypeptides and to a lesser extent into β polypeptides. Only with longer incubation times (15 min or more) did label appear in the γ and δ polypeptides; and this coincided with a progressive loosening and ultimate collapse of the viral capsid. Antisera specific for each of the capsid polypeptide species were produced in rabbits using isolated proteins as antigens. Reaction of virions with these antisera in plaque-neutralization and hemagglutination-inhibition tests showed that only the anti-α serum was capable of blocking virus-cell interactions. Complement-fixation and immunodiffusion tests confirmed the observations that the α polypeptides occupy most of the external surface of the virus particle and that the β polypeptides are partially exposed. The γ and δ polypeptides apparently occupy internal locations in the capsid of the Mengo virion.

Antibodies to coronaviruses OC43 and 229E in multiple sclerosis patients

Multiple sclerosis (MS) and matched control sera had similar antibody titers to coronaviruses OC43 and 229E when tested by a radioimmunoassay method. In contrast, cerebrospinal fluid from MS patients contained coronavirus antibodies more frequently and in higher titers than matched controls. Intrathecal antibody synthesis to OC43 and 229E viruses was detected in 41% (9/22) and 26% (7/27) of MS patients, respectively, but was not found in any of the neurologic control patients. This intrathecal antibody synthesis may mean that coronaviruses play an etiologic or pathogenic role in MS. Alternatively, intrathecal synthesis of coronavirus antibodies may be but part of a generalized and variable intrathecal antibody synthesis that is typical for MS patients.

Antigenicity of the measles virus haemagglutinin studied by using synthetic peptides.

A combined analysis of hydrophilicity, accessibility and flexibility parameters of the deduced amino acid sequence of measles virus (MV) haemagglutinin (H) was used to select 10 regions for synthesis of 10- or 11-amino acid-long peptides. Nine of these sites are probably exposed on the surface of the protein, as polyclonal sera against either purified MV or purified H bound to these peptides as tested by enzyme immunoassay (EIA). Nevertheless, human sera from acute or chronic MV infection did not bind significantly to any peptide, indicating that the selected sites do not function as natural complete epitopes. All antisera raised in rabbits against keyhole limpet haemocyanin-conjugated peptides had a high titre to the homologous peptide and nine of them bound to MV lysate antigen, purified MV and/or purified H as tested in EIA. None of the sera had haemagglutination-inhibiting antibodies and only one antiserum (against peptide 185-195) had a neutralizing antibody titre of 1/160. Only a minority of the antisera were positive in Western blot (four of 10), radioimmunoprecipitation (two of 10) or immunofluorescence (three of 10). The results indicate that the computer program used in this analysis can predict surface-exposed areas of MV H but that the small peptides synthesized have little resemblance to natural antigenic sites.

Temporal relationship between environmental influenza A and Epstein-Barr viral infections and high multiple sclerosis relapse occurrence.

Background: Multiple sclerosis (MS) relapses have been associated with viral and bacterial infection epidemics in MS patients who have not used interferon. Objectives: We studied whether environmental viral infections in the general population can be associated with increased MS relapse occurrence using retrospective data from 1986 to 1995 when interferons were not yet available. Methods: Logistic regression modelling was used to compare retrospectively the monthly relapse occurrence from 407 MS patients in Turku University hospital archives and data on ten different specifically diagnosed viral infection epidemics in the general population of Southwestern Finland from 1986 to 1995. The outcome was the odds ratio (OR) of very high relapse occurrence versus low relapse occurrence, or moderate versus low relapse occurrence. Results: After a peak in diagnosed influenza A cases in the general population, the MS relapse occurrence was 6.5 times more likely to be very high (95% CI 1.8–24.0) and 7.1 times more likely to be moderately high (95% CI 1.5–33.2). An increase in MS relapse counts also followed Epstein–Barr virus (EBV) infections (OR 4.4, 95% CI 1.3–15.1), but we found no significant association with adenovirus infections and MS relapses. The MS relapse occurrence was lowest in the summer months July–August (Chi-square test, pu2009<u20090.01). Conclusions: Our findings suggest that influenza A and EBV viral infections in the general population are associated with a higher occurrence of exacerbations in MS patients, and thus environmental infection data should be included in epidemiological models on MS relapses.

Effect of viral infection on experimental allergic encephalomyelitis in mice

BALB/c mice were irradiated with 350 R and injected with mouse spinal cord homogenate (MSCH) in complete Freunds adjuvant. Only 15-30% of these animals developed signs of experimental allergic encephalomyelitis (EAE) at 21-28 days after inoculation. Intraperitoneal infection with the non-lethal A7 strain of Semliki forest virus (SFV) 7 days after sensitization reduced the mean appearance time of the EAE symptoms to 14 days and the number of animals with clinical EAE increased up to 70%. In contrast, virus inoculation 10 days before induction of EAE decreased significantly the incidence of clinical EAE in both BALB/c and SJL mice. Demyelination with increased cellularity, presence of macrophages, stripping of myelin from the axons and sparing of oligodendrocytes was observed in spinal cords of animals at days 13-16 after induction of EAE and subsequent virus infection. No demyelination was seen in specimens taken at the same time from mice inoculated with MSCH or SFV alone. Combined MSCH and virus inoculations induced changes in the general immune response which may be one of the major reasons for the increase or decrease in demyelination in this model.

Cloning of human T cells specific for measles virus haemagglutinin and nucleocapsid

T cell lines specific for measles virus (MV) were generated from blood of two DR1/DR2 heterozygous healthy donors with a history of past measles infection. The antigenic specificity of 66 T cell clones derived from the lines was studied in a blastogenic assay using whole measles virus and two purified virus components, haemagglutinin and nucleocapsid. Thirty‐nine of the clones were specific for one of the two purified antigens. None of seven synthetic peptides covering 20% of the MV haemagglutinin amino acid sequence stimulated T cell clones with haemagglutinin specificity. Responsiveness of the majority of the clones were restricted by HLA‐D/DR antigens, although two clones were isolated that responded only to MV antigens presented by autologous cells. Ten of 11 clones recognizing the nucleocapsid antigen were DR1‐restricted, while the haemagglutinin antigen and whole measles virions were recognized more often in association with the DR2 antigen. These results indicate that much of the MV‐specific memory T cell response is specific for the haemagglutinin and nucleocapsid virus antigens, with the DR antigen being the main restriction element involved.

Monoclonal antibodies against measles virus haemagglutinin react with synthetic peptides

The ability of 17 monoclonal antibodies (MoAb) antibodies measles virus haemagglutinin (MV‐H) to bind to 10 selected MV‐H‐specific synthetic peptides was tested in an enzyme immunoassay (EIA). Three peptides representing residues 126–135 (close to the NH2 terminus). 309–318 (middle), and 587–596 (C‐terminal) reacted with MoAb designated 48, 129, and 18, respectively. Binding of MoAb 129 to purified virus was abolished after pre‐incubation with the peptide 309–318. Similarly. MoAb 48 did not bind to the virus after absorption with the peptide 126–135. Longer peptides of 19 residues from the regions reacting with the MoAb were also synthesized and tested in EIA. None of the MoAb recognized these longer peptides when the latter were bound as free peptides on solid phase. However, MoAb 129 binding to purified virus was blocked equally well by peptides 304–322 and 309–318. In contrast, peptide 121–139 absorbed the reactivity of the MoAb 48 much more weakly than the shorter peptide 126–135, suggesting that the conformation of the longer peptide in solution is different. To analyse affinities in the antigen antibody reactions, the plates were washed with buffers of varying pH after absorption of the MoAb to MV or peptides. The MoAb 129 bound both to MV and peptide 309–318 with equal affinity, but MoAb 48 and 18 bound to the peptides 126–135 and 587–596 with lower affinity than to the virus. This study indicates that regions corresponding to amino acids 126–135, 309–318, and 587–596 define antigenic sites of the H protein.

A comparative study of BK and polyoma viruses

Abstract A comparative study of BK and polyma (Py) viruses has shown that the molecular anatomy of the two virions is strikingly similar. The capsids of both are composed of 72 capsomeres arranged in a T = 7d icosahedral lattice. Analysis of the DNAs of the two viruses suggest that the full-length DNA of BK virus may be slightly smaller than that of Py virus. The two virions contain the same number of structural polypeptides, but the molecular mass of BK-VP1 is about 4000 daltons less, and those of BK-VP2 and 3 about 4000 daltons more than those of the corresponding Py polypeptides. The observation that the major capsid polypeptide, BK-VP1, is smaller than Py-VP1, is compatible with the observed difference in the diameters of the two virions (BK = 405 ± 10A; Py = 430 ± 15A). The two viruses differ sharply in the relative efficiencies with which they hemagglutinate guinea pig and human erythrocytes. BK virus, unlike Py virus, replicates only in certain human or monkey cells; and of the cells examined in this study, human fetal kidney cells are the most satisfactory for the propagation of this agent.

Isolation and characterization of BK virus-transformed hamster cells.

Abstract BK virus (BKV) was used to transform baby hamster kidney (HK) and hamster embryo fibroblast (HE) cells in culture. Six clones of each of the BKV-transformed HK and HE cells were isolated and characterized with respect to a number of biological properties. None of the cloned lines was found to produce infectious BKV, and all 12 lines were shown to contain BKVT antigen, to have a lower serum dependency for growth and to grow to higher saturation densities than the corresponding untransformed cells, to have higher plating efficiencies than control cells, to have acquired the ability to produce colonies in soft agar, and to produce progressively growing tumors when injected subcutaneously into weanling hamsters. Differences were found to exist among the cell lines of each group with respect to these parameters, and, in general, transformed HK cells have a lower serum dependency, grow to higher saturation densities, and have higher plating efficiencies and a greater capacity to produce colonies in soft agar than do the transformed HE cells. Infection of secondary cultures of HE cells with various input multiplicities of BKV showed that transformation is a multiplicity-dependent phenomenon and can be achieved with an input multiplicity as low as 3 PFU/cell.

ASSOCIATION OF MEASLES ANTIBODY ACTIVITY WITH ELECTROPHORETIC FRACTIONS OF CSF IN A PATIENT WITH MULTIPLE SCLEROSIS

The immunoglobulin production in the central nervous system (CNS) of patients with multiple sclerosis (MS) is characterized by an oligoclonal pattern ( L i n k & Miiller 1971). Similar production in patients with subacute sclerosing panenccphalitis (SSPE) has been shown to be directed against antigens of measles virus (Link et al . 1972, Vandvik & NorrbU 1972). In some MS patients antibody production to measles virus has been suggested to occur in the CNS ( S a l m i et al . 1972 a, b). As a preliminary report, we now demonstrate measles-specific antibody activity associated with immunoglobulin fractions of IgG in the cerebrospinal fluid (CSF) from a patient with MS.