Influence of Quillaja saponaria triterpenoid content on the immunomodulatory capacity of Epstein-Barr virus iscoms

The immune responses to immunostimulating complexes (iscoms) containing recombinant Epstein-Barr virus (EBV) gp340 envelope protein was evaluated in BALB/c (H-2(d)) and CBA (H-2(k)) mice. Gp340-iscoms were used either with a low content of Quillaja triterpenoid adjuvant (L-iscoms) or supplemented with additional Quillaja adjuvant in the form of iscomatrix (S-iscoms). Class and subclass distribution of anti-gp340 antibodies, EBV-neutralizing antibodies, antigen-specific T cell proliferation and cytokine production were determined and these results compared to those obtained by immunization with non-adjuvated gp340. The H-2(d) and H-2(k) mice were characterized as low or high responders in respect to the level of specific anti-gp340 antibodies, secretion of IgG2a isotype, antigen-specific lymphoproliferative capacity, interferon-gamma (IFN-gamma) and interleukin-10 (IL-10) production in the basic immunizations with gp340. While presentation of the antigen in iscom formulations with low levels of Quillaja triterpenoids induces a moderate enhancement of the immune responses in the low responder H-2(d) mice, supplementation with high levels of iscomatrix immunomodulator was required to enhance the immune responses in the high responder H-2(k) mice. In both mouse strains subcutaneous immunization with S-iscoms resulted in a significant increase of IgG1- and IgG2a-specific antibodies, as well as in strong antigen-specific proliferative response confirmed by the simultaneous cytokine production. The enhanced antigen-specific secretion of IL-2 and IFN-gamma together with the abrogation of IL-10 and the absence of IL-4 indicates that the responses were driven towards a Th1-type rather than Th2-type immune response. The S-iscom formulations minimized the differences in immune responses between the two mouse strains, but the capacity of immune sera to neutralize EBV transformation in vitro remained completely strain-dependent. These data indicate that immune responses generated by iscoms can be manipulated by altering the triterpenoid composition of the iscoms and that the levels of triterpenoids can determine whether or not a Th1-type response is made.

Observations on the use of ELISA for detection of Babesia bigemina specific antibodies

An indirect enzyme-linked immunosorbent assay (ELISA) was evaluated to study the cause of the high level of background reactions which hinders the application of ELISA as a field diagnostic test for Babesia bigemina. Different blockers to improve the specificity of the ELISA were compared. THe use of soya milk (25%), gelatin (2.5%) and chicken serum (2%) did not significantly improve the specificity of the test. It was noted that the presence of fibrinogen contributed to the positive ELISA results more than the presence of B. bigemina specific antigen. This conclusion was confirmed by testing bovine fibrinogen as a host protein antigen in ELISA which strongly responded against B. bigemina positive control sera. It is suggested that application of ELISA for B. bigemina is still unreliable until a more purified Babesia-specific antigen or specific monoclonal antibodies are available.

Antigenicity and immunogenicity of experimental equine influenza ISCOM vaccines

A comparison of the antigenicity and immunogenicity of ISCOM vaccines prepared from equine influenza viruses H3N8 and H7N7 was made with inactivated whole-virus vaccines containing equivalent amounts of virus haemagglutinin. ISCOMs stimulated superior antibody responses in terms of both amount and duration. As with conventional whole-virus vaccines, the levels of antibody to virus haemagglutinin induced by ISCOMs correlated with protection.

Four-year study of caries inhibition of intensive Duraphat application in 11-15-year-old children

The purpose of the study was to evaluate the caries preventive effect and cost of an intensive application of Duraphat varnish, added to the regular preventive program for 11-15-yr-old children in a Swedish Dental Community Clinic. In 1987, the 134 11-yr-old children in Floda were divided into two groups, every second child to each. Children with fixed orthodontic appliances were excluded. The test group received three applications of Duraphat varnish during 1 week, once a year, by a dental nurse. The control group received one application at the annual check-up. Both groups were included in the regular preventive program at the clinic. The total time cost for the clinic was estimated and used to calculate the cost per hour for dentists and nurses. The caries increment and progression were estimated both by routine diagnosis and by a careful study of radiographs taken at the beginning and end of the study period. There was a small caries increment and progression in the test group as compared to the control group. The difference was statistically significant for all aspects studied. The costs were about the same in both groups but more time was used in the test group. The administrative effort for the staff was considerable for the intensive Duraphat application.

Evaluation of a monoclonal blocking enzyme-linked immunosorbent assay for the detection of Mycoplasma gallisepticum-specific antibodies

A monoclonal blocking enzyme-linked immunosorbent assay (blocking-ELISA) was developed to detect antibodies to Mycoplasma gallisepticum (MG) in poultry sera with the help of a peroxidase-labeled monoclonal antibody (MAb) recognizing an epitope of a 56-kilodalton polypeptide (p56) of MG. Immunoglobulins from undiluted MG-positive sera prevent the MAb conjugate from attaching to its specific binding site on p56, which results in no color development. The opposite result--a strong color reaction--was obtained after incubation with MG-negative sera (or when no serum was added before the MAb conjugate). Results were expressed in percent inhibition or ELISA titers. The blocking-ELISA detected 84.7% positive chickens in an experimentally infected flock and 72.6% of chickens in naturally infected flocks, whereas the hemagglutination-inhibition (HI) test was positive only with 68.4% and 48.6% of these serum samples, respectively. All HI-positive serum samples reacted positively in blocking-ELISA. Of sera negative by the HI test, 51.6% and 46.8% proved to be positive when examined with the blocking-ELISA. Overall agreement between the ELISA and HI test was 76.8%. Infection with closely related M. synoviae did not induce any false-positive reactions in blocking-ELISA. There was a strong positive correlation between HI and blocking-ELISA titers (r = 0.83).

An immune stimulating complex (ISCOM) subunit rabies vaccine protects dogs and mice against street rabies challenge

Dogs and mice were immunized with either a rabies glycoprotein subunit vaccine incorporated into an immune stimulating complex (ISCOM) or a commercial human diploid cell vaccine (HDCV) prepared from a Pitman Moore (PM) rabies vaccine strain. Pre-exposure vaccination of mice with two intraperitoneal (i.p.) doses of 360 ng ISCOM or 0.5 ml HDCV protected 95% (38/40) and 90% (36/40) of mice, respectively, against a lethal intracerebral (i.c.) dose with challenge virus strain (CVS). One 360 ng i.p. dose of ISCOM protected 87.5% (35/40) of mice against i.c. challenge with CVS. Three groups of five dogs were vaccinated intramuscularly (i.m.) with 730 ng of rabies ISCOM prepared from either the PM or the CVS rabies strains, and they resisted lethal street rabies challenge. Postexposure treatment of mice with three or four 120 ng i.m. doses of ISCOM protected 90% (27/30) and 94% (45/48), respectively, of mice inoculated in the footpad with street rabies virus, but three doses of HDCV conferred no protection. When four doses of HDCV were administered postexposure, 78% (32/41) of the mice died of anaphylactic shock; 21% (11/52) of mice had already died of rabies 4 days after the third vaccine dose was administered.

Characterization of purified gp 51 from bovine leukemia virus integrated into iscom. Physicochemical properties and serum antibody response to the integrated gp51

It is proposed that the envelope glycoprotein, gp 51, is the protective antigen of bovine leukemia virus (BLV). An experimental iscom vaccine has been prepared from immunoaffinity purified gp 51. To overcome the problem of integrating a nonamphipathic protein, gp 51 was partially denatured at pH 2.4 before integration into the iscom. The recovery of gp 51 into the iscom was calculated to be 85%. The gp 51 incorporated into iscom retained its physicochemical properties and the neutralizing epitopes F, G and H were found to be intact. The iscom preparation was shown to induce a specific immune response to gp 51 after inoculation into mice and calves, as tested by ELISA and Western blotting. Sera from the immunized calves specifically inhibited the VSV-(BLV) pseudotypes. Thus the gp 51-iscom preparations appear to be highly immunogenic and to induce a gp 51 specific response.

Immunoaffinity purification of two major proteins of bovine leukemia virus (gp51 and p24) and their use for discrimination between vaccinated and infected animals

The outer envelope glycoprotein gp51 and the core protein p24 of bovine leukemia virus (BLV), were purified from culture media of FLK-BLV cells by a single-step procedure, using immunoaffinity chromatography based on monoclonal antibodies to the respective proteins. About 90% of the envelope glycoprotein in the culture medium was recovered as a highly purified product. Both purified protein (gp51 and p24) preparations, were found to be highly specific antigens by ELISA, and did not cross-react with sera raised against the other antigen. The conformational epitopes on the purified gp51 were preserved as judged by their reactions with the corresponding monoclonal antibodies. The p24 ELISA reacted only with sera from naturally infected animals and not with sera from animals immunized with an experimental gp51-iscom vaccine. The p24 antigen is therefore useful for discriminating between BLV-infected animals and those immunized with a gp51 subunit vaccine.

Protective effect of an ISCOM bovine virus diarrhoea virus (BVDV) vaccine against an experimental BVDV infection in vaccinated and non-vaccinated pregnant ewes

Fifteen pregnant ewes were vaccinated twice with an experimental immunostimulating complex (ISCOM) subunit vaccine designed to contain the envelope proteins of a Danish cytopathic bovine virus diarrhoea virus (BVDV). The serological responses were measured in ELISA and virus neutralization (VN) tests. All ISCOM-vaccinated ewes developed high VN antibody titres to BVDV in contrast to the 14 non-vaccinated ewes. Both groups of ewes were challenged parenterally when 48-65 days pregnant with a Swedish cytopathic BVDV isolate. In the vaccinated group 26 fetuses out of 29 detected by ultrasound were liveborn, whereas only six out of 26 were liveborn in the non-vaccinated group. It is concluded that the ISCOM vaccine had the potential of eliciting high VN titres as well as protecting fetuses against transplacental infection after challenge with a virulent BVDV isolate.

Protection against lethal equine herpes virus type 1 (subtype 1) infection in hamsters by immune stimulating complexes (ISCOMs) containing the major viral glycoproteins

An experimental ISCOM vaccine has been prepared from gradient purified equine herpes virus type 1 (EHV-1). Radiolabelling studies demonstrated that this vaccine contained all the major viral glycoproteins in relative amounts similar to those found in non-detergent disrupted viral preparations. This EHV-1 ISCOM vaccine generated fully protective responses in hamsters challenged with an otherwise lethal dose of the hamster-adapted EHV-1 strain RACH.

Characterization and purification of Parafilaria bovicola antigens by chromatofocusing to enhance specificity in serodiagnosis

A study was conducted to determine if the purification of Parafilaria bovicola antigens can increase the specificity of serodiagnosis of parafilariasis in enzyme-linked immunosorbent assay. Antigens released from adult worms of P. bovicola were separated by chromatofocusing on a polybuffer exchanger of the pH range 7.3-4.0 Polypeptide analysis by sodium dodecyl sulphate polyacrylamide gel electrophoresis showed the presence of four major polypeptides with MWs of 41, 36, 24 and 20 kDa. Additional biochemical characterization identified the 24- and 20-kDa polypeptides as hydrophobic glycoproteins. The chromatofocusing purification procedures were also applied for separation of a whole-worm extract. Again, the 41- and 36-kDa antigens were identified in separate peak fractions. Using ELISA, it was shown that the 41- and 35-kDa antigens were recognized by bovine antibodies specific for P. bovicola, but not by other sera collected from cattle infected by Onchocerca gutturosa, Onchocerca lienalis, Ostertagia ostertagi and Dictyocaulus viviparus. The serological evaluation strongly suggests that the 41- and 36-kDa antigens are P. bovicola specific.

Equine herpes virus 1 (EHV-1) in liver, spleen, and lung as demonstrated by immunohistology and electron microscopy

Ten aborted foals, diagnosed as infected with Equine Herpes Virus 1 (EHV-1) on histopathological criteria, were examined for the presence of EHV-1 using immunohistology as the investigative instrument. The primary reagent was an antiserum specific for viral envelope glycoproteins. Immunohistology localised EHV-1 to areas of liver necrosis and to the cytoplasm of infected Kupffer cells and hepatocytes. Cytoplasmic immunolabelling was also prominent in reticular cells of the red pulp of the spleen and in intact and degenerated bronchiolar epithelium. Cytoplasmic immunolabelling was seen in morphologically unchanged cells and in cells containing intranuclear inclusion bodies. Three aborted foetuses with no histological signs of EHV-1 infection were negative when immunostained for EHV-1. Detection by electron microscopy of EHV-1 virions confirmed the EHV-1 specificity of the immunolabelling procedure.

Preparation and evaluation of the specificity of Parafilaria bovicola antigen for detection of specific antibodies by ELISA

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies in bovine sera against Parafilaria bovicola nematodes was developed and its sensitivity was compared with the immunodiffusion (ID) method. An exoantigen of P. bovicola which was shown to contain four major polypeptides was used in these procedures. The serological reactivity of the antigen polypeptides was defined by using the enzyme-linked immunoelectrotransfer blot technique (EITB) and whole-worm extract proteins. It identified only four serologically reactive polypeptides with sera from one experimentally infected calf and a verified field case. These two positive sera reacted mainly with four major antigens which coincided in molecular weights of the polypeptides of the exoantigenic preparation, namely, 43, 39, 28 and 25 KDa. Calves experimentally infected with P. bovicola showed a positive reaction with ELISA at 4 months after inoculation, and after this period a rapid increase in serum antibody response occurred. In these cases the ID reaction was observed for the first time at 7 months after inoculation. The specificity of an ELISA method using crude exoantigen preparation of P. bovicola was tested for the diagnosis of bovine parafilariasis. No cross-reactivity was detected when the P. bovicola exoantigen preparation was tested against sera from calves experimentally infected with Onchocerca lienalis, as well as against the sera from cattle naturally infected with Dictyocaulus viviparus or from cattle chronically infected with Ostertagia ostertagi. In addition, testing of 740 field sera from cattle in areas non-endemic and endemic for P. bovicola indicated a specificity of the antigen preparation used. Forty sera from laboratory-confirmed field cases of P. bovicola infection were tested by ELISA and immunodiffusion. All of these sera were ELISA positive, whereas only 70% of these were positive in the ID test. Seven (2.1%) of 328 sera from 21 herds from non-endemic P. bovicola areas were ELISA positive, as opposed to none in the ID test. Of the 94 sera from six herds in areas endemic for P. bovicola infection, 51 (54%) were ELISA positive whereas only 24 (26%) were positive in the ID test. When 56 slaughtered cattle, with varying degrees of meat condemnations due to parafilariasis, were tested for P. bovicola specific antibody, 91% of the serum samples were positive by ELISA. These results suggest that the exoantigen of P. bovicola can be used in a sensitive and reliable serological detection of parafilariasis by ELISA.

Measles virus fusion protein presented in an immune-stimulating complex (iscom) induces haemolysis-inhibiting and fusion-inhibiting antibodies, virus-specific T cells and protection in mice

Immune-stimulating complexes (iscoms), which have recently been shown to be highly effective for the antigenic presentation of membrane proteins of viruses, were prepared with affinity-purified fusion (F) protein of measles virus (MV), using an adaptation of the standard method for iscom preparation. Immunization of monkeys with the F iscom preparation induced biologically active anti-F protein antibodies as was shown in haemolysis inhibition and cell-cell fusion inhibition tests. A whole MV iscom preparation, which also contained the haemagglutinin protein, induced not only also haemolysis-inhibiting antibodies, but, in contrast to the F iscom preparation, also haemagglutination-inhibiting and virus-neutralizing antibodies. In addition the F iscom preparation was shown to activate measles virus-specific T cells in mice. This was demonstrated by the generation of an MV-specific delayed type hypersensitivity response in F iscom-immunized animals and by the isolation of T cell clones specific for MV F protein with the T helper phenotype. Vaccination of mice with MV iscom or F iscom protected them from MV-induced fatal encephalopathy. The data concerning the immunogenicity of MV proteins presented in iscoms are discussed in relation to their potential for the development of an inactivated measles vaccine.

Influenza virus ISCOMs: biochemical characterization

Immunostimulating complexes (ISCOMs) have been prepared from influenza A virus envelope glycoproteins, i.e. haemagglutinin (HA) and neuraminidase (NA). An ISCOM consists of a matrix, which is the micellar form of the glycoside, Quil A, in hydrophobic interaction with both the envelope glycoproteins (HA/NA). The Quil A bound to the ISCOM amounted to 50 micrograms mg-1 (5%) of ISCOM protein. ISCOMs were morphologically identified as symmetrical cage-like structures of approximately equal to 40 nm in diameter with hexagonal or pentagonal subunits of approximately equal to 12 nm. The sedimentation coefficient was approximately equal to 19 S as compared to 30 S for the glycoprotein micelles. The biological activities of the HA and NA are preserved in both ISCOMs and micelles.

Influenza virus ISCOMs: antibody response in animals

A monovalent experimental ISCOM vaccine has been prepared with the envelope glycoproteins haemagglutinin and neuraminidase of the equine virus strain A/Solvalla/79 (H3N8). In vaccination trials on BALB/c mice the ISCOM vaccine induced more than ten times higher serum antibody titres measured in ELISA than a corresponding experimental micelle vaccine. Similarly, in guinea-pigs the ISCOMs induced about tenfold higher haemagglutination inhibition (HI) and neuraminidase inhibition (NI) titres than a micelle vaccine or a conventional killed influenza whole virus vaccine. Horses vaccinated with a divalent experimental ISCOM vaccine, containing the equine strains A/Prague/56 (H7N7) and A/Solvalla/79 (H3N8), responded with ELISA antibody titres against haemagglutinin which were higher and lasted considerably longer than those in horses vaccinated with conventional whole virus vaccine. ISCOMs induced complete immunoprotection in mice vaccinated with a dose of 1 microgram envelope glycoproteins of the mouse pathogenic strain A/PR/8/34 (H1N1).

Preparation and properties of immune-stimulating complexes containing hepatitis B virus surface antigen

Immune-stimulating complexes (iscoms) have been prepared containing the major S gene products (HBsAg) of the hepatitis B virus genome. Immunization of BALB/c mice with a single dose of hepatitis B iscoms in saline resulted in a high titre antibody response to HBsAg. In contrast, the original HBsAg preparation required an adjuvant to produce equivalent amounts of antibody. Analysis of sera from mice immunized with hepatitis B iscoms revealed antibodies directed against the major a determinants of HBsAg. High secondary antibody responses were observed in immunized animals previously inoculated with a sub-immunogenic dose of HBsAg indicating that hepatitis B iscoms may represent a suitable immunogen for use in individuals in whom a course of immunization with currently licensed hepatitis B vaccines has failed to produce a significant anti-HBs response.

Comparison of 252californium plasma desorption and fast atom bombardment mass spectrometry for analysis of small peptides

The data obtained with 252Cf plasma desorption (PD) and fast atom bombardment mass spectrometry of eight tri-, tetra- and pentapeptides were compared. Good spectra were obtained with 1-10 nmol of peptide. In both techniques molecular weight information was obtained. The PD mass spectra are often dominated by the cationized molecular ions in contrast to the fast atom bombardment (FAB) mass spectra, where cationization is rarely observed. Amino acid content is reflected in the immonium ions equally well in both techniques. The fragmentation patterns observed with the two techniques are almost identical. However, practical sequencing of peptides based on either FAB or PD mass spectrometry of underivatized peptides alone is difficult. This is due to the unpredictable and sometimes absent cleavage yield at certain peptide bonds. Another difficulty is the many simultaneous fragmentation pathways. However, for many peptides enough information is present to allow sequence determination for at least a major part of the molecule.

Induction of protective immune response in cats by vaccination with feline leukemia virus iscom

An effective candidate subunit vaccine consisting of the gp 70/85 of feline leukemia virus (FeLV) was prepared by using the immunostimulating complex (iscom) method for the presentation of membrane proteins of enveloped viruses. Two 32-wk-old specific pathogen-free (SPF) cats were immunized with a FeLV iscom vaccine prepared from the supernatant fluid of the FL74 tumor cell line without adjuvant. Both cats developed FeLV serum antibodies, as measured in an enzyme-linked immunosorbent assay (ELISA) and in a virus neutralization test. A proportion of the antibodies were directed to an epitope located on gp70/85, which was shown in competition ELISA with a peroxidase-labeled virus-neutralizing monoclonal antibody to be shared by all three subtypes of FeLV. The protective effect of FeLV iscom was studied by vaccinating six 8-wk-old SPF cats with iscom prepared from cell culture supernatant of another tumor cell line F422, followed by oronasal challenge with 10(6) ffu FeLV-A (strain Glasgow-1). Six unvaccinated cats were also challenged with the same dose of FeLV. The vaccinated cats developed FeLV serum antibodies, some of which were directed to the shared epitope on gp70/85. At 10 wk after challenge, none was viremic, whereas three of the control cats had developed FeLV viremia. The potential of FeLV iscom as a vaccine against FeLV-associated disease in cats, and of iscom vaccines for protection against mammalian retrovirus infections, is discussed.

Induction of protective immune response in cats by vaccination with feline leukemia virus iscom

An effective candidate subunit vaccine consisting of the gp 70/85 of feline leukemia virus (FeLV) was prepared by using the immunostimulating complex (iscom) method for the presentation of membrane proteins of enveloped viruses. Two 32-wk-old specific pathogen-free (SPF) cats were immunized with a FeLV iscom vaccine prepared from the supernatant fluid of the FL74 tumor cell line without adjuvant. Both cats developed FeLV serum antibodies, as measured in an enzyme-linked immunosorbent assay (ELISA) and in a virus neutralization test. A proportion of the antibodies were directed to an epitope located on gp70/85, which was shown in competition ELISA with a peroxidase-labeled virus-neutralizing monoclonal antibody to be shared by all three subtypes of FeLV. The protective effect of FeLV iscom was studied by vaccinating six 8-wk-old SPF cats with iscom prepared from cell culture supernatant of another tumor cell line F422, followed by oronasal challenge with 10(6) ffu FeLV-A (strain Glasgow-1). Six unvaccinated cats were also challenged with the same dose of FeLV. The vaccinated cats developed FeLV serum antibodies, some of which were directed to the shared epitope on gp70/85. At 10 wk after challenge, none was viremic, whereas three of the control cats had developed FeLV viremia. The potential of FeLV iscom as a vaccine against FeLV-associated disease in cats, and of iscom vaccines for protection against mammalian retrovirus infections, is discussed.

A non-haemagglutinating isolate of mink enteritis virus

A virus was isolated from mink showing clinical and pathological signs of mink enteritis. This virus was identified as mink enteritis virus (MEV) from results of serological tests, determination of its density in CsCl (1.415 g cm-3), and morphology, including size (20 nm in diameter). The isolate was designated MEV-S. In contrast to other known MEV strains, the MEV-S isolate has no haemagglutinating (HA) activity with swine red blood cells (RBCs) at 4 degrees C and pH 6.8. Neither was there any HA at other pH values and temperatures, or when horse, bovine and rhesus monkey RBC's were used.

Iscom, a novel structure for antigenic presentation of membrane proteins from enveloped viruses

We describe here a novel type of immunostimulating complex, called 'iscom', in which virus membrane proteins are presented in a multimeric form. The matrix of the iscom is the glycoside Quil A (Spikoside; Iscotec AB), extracted from the bark of Quillaja saponaria Molina, which forms micelles at the critical micellar concentration of 0.03%. In micelle form, Quil A probably has regions accessible for hydrophobic interaction with the membrane proteins so that it can form complexes with them. Iscoms have been prepared with membrane proteins of para-influenza-3 (PI-3), measles and rabies viruses, and their immunizing potency tested in animals. In these experiments, iscoms prove to be at least 10 times more potent than micelles formed by aggregation of the membrane proteins alone. Iscoms of PI-3 and measles viruses also stimulate the formation of antibody to the fusion (F) protein, which is considered to be poorly immunogenic. No side effects of iscoms or of protein micelles have been observed.

Assay of detergents by rocket electrophoresis in agarose gels containing red blood cells: "rocket hemolysis"

A method is described for quantitation of charged detergents using their hemolytic property in an electrophoresis assay in agarose gels containing red blood cells. After electrophoresis the zone of hemolysis is directly proportional to the concentration of detergent in the sample. Using this technique we have determined the smallest detectable concentration for the negatively charged detergents, sodium dodecyl sulfate (SDS) and Quil A to about 10 micrograms/ml and 25 micrograms/ml, respectively and the positively charged cetyltrimethylammonium bromide (CTAB) to about 10 micrograms/ml.

Protein subunit vaccines of parainfluenza type 3 virus: immunogenic effect in lambs and mice

Protein subunit vaccines were prepared from a mixture of the haemagglutinin (HN) and fusion (F) glycoproteins of parainfluenza type 3 virus (PI-3). The glycoproteins were isolated in three different forms and characterized by their sedimentation coefficients: 30S protein micelles (a complex of several HN and F glycoproteins devoid of detergent and lipid), 18S protein-TX complexes (a complex of several glycoproteins containing the detergent Triton X-100), and 4S protein-TX complexes (probably monomers of the glycoproteins complexed to Triton X-100). These preparations were tested as vaccines in mice and lambs. The immune response in the mice was assayed both in the serum and in extracts from the lungs using an ELISA technique. Both of the multimeric complexes were highly immunogenic. The 30S protein micelles induced a high antibody response after two injections with either 10 or 1 microgram protein. The serum IgG titres reached levels of about 90 micrograms/ml and 40 micrograms/ml respectively. Similar titres were reached with the 18S protein-TX complexes. After two injections of either the 30S or the 18S complexes IgA antibody responses were detected in the lung extracts. The 4S protein-TX complexes were poor immunogens and induced low antibody responses in mice. The lambs were vaccinated with the 30S protein micelles, and the immune response was evaluated serologically and in challenge experiments. The 30S protein micelles in an oil adjuvant induced detectable serum antibody titres as well as protective immunity against the pneumonia caused by the PI-3 virus.

Goat visna virus: isolation of a retrovirus related to visna virus of sheep

Choroid plexus (GCP-3) cell cultures were prepared from an adult goat with symptoms of visna. The GCP-3 cell layer had partly fused into large multinucleated giant cells and electronmicrographs showed virus particles morphologically indistinguishable from sheep visna virus (SVV). A virus, designated goat visna virus (GVV), was subsequently purified from the GCP-3 cultures. The virus particles have a density of 1.15 g/ml and a high molecular weight RNA similar in size to that of SVV. A virion-associated DNA polymerase was identified which is stimulated to the same extent as the SVV polymerase by different synthetic RNA and DNA template-primer combinations and which shows the same Mg2+ and Mn2+ stimulation optima. Polypeptide analysis by SDS-PAGE revealed that the virion proteins of GVV and SVV had similar molecular weights. By immunodiffusion tests it was demonstrated that the major internal proteins of GVV and SVV are related. Consequently, we conclude that GVV should be classified as a retrovirus and that it is closely related to visna virus of sheep.

Visna virus meningoencephalomyelitis in goats

A progressive paresis was encountered in herds of Swedish goats. The symptoms developed during a period of weeks or months, and were initially often seen as a weakness of the hind limbs before the animals became paralytic. The development and the histopathological lesions of the disease in the GNS and the lungs were similar to those of visna in sheep. In vitro grown choroid plexus cells, prepared from affected goats, showed foci of polykaryocytes. Electron microscopy revealed the presence of particles morphologically similar to those of sheep visna virus (SVV). Goats experimentally infected with the goat visna virus (GVV) developed GNS lesions similar to those of visna in sheep and became seropositive to SVV. The results of complement fixation tests, carried out on sera from 11 goat herds, showed a coincidence between seropositiveness and the occurrence of disease in one and the same herd. Using the ELISA method, an average of 80 % of the goats in 5 herds were found to be seropositive to GVV.

Phosphonoformate inhibits reverse transcriptase

The new antiviral substance phosphonoformate (PFA) has been tested in a cell-free system for its effect on reverse transcriptases from an avian retrovirus (avian myeloblastosis virus, AMV) and from mammalian retroviruses (Rauscher leukaemia virus, RMuLV; bovine leukaemia virus; baboon endogenous virus; simian sarcoma virus; visna virus). The observed inhibitory effect of PFA has been compared with that of a structurally related substance, phosphonoacetate (PAA). Phosphonoformate, at a concentration of 100 microM, reduced the activities of all the above mentioned polymerases by 90% when (rA)n.(dT)10 was used as a template/primer. The dose-response curves for AMV and RMuLV polymerases primed with (rA)n.(dT)10 showed PFA to be a 1000-fold more active than PAA; the RMuLV polymerase activity was reduced to 50% after incubation with 0.7 microM-PFA and 0.7 mM-PAA, respectively. There was no difference in PFA inhibition of virus-associated and purified reverse transcriptase activity. Results with various synthetic templates showed that both the RNA- and the DNA-dependent polymerase activities of reverse transcriptase were inhibited by PFA. The endogenous polymerase activity of AMV was inhibited to 50% at 100 microM-PFA, while PAA had no effect. The PFA inhibition was dependent on whether Mg2+ or Mn2+ was used as divalent cation in the assay. Phosphonoformate arrested DNA synthesis immediately after being added to the assay system. The mechanism of inhibition of the AMV polymerase was non-competitive with respect to substrate and template and the apparent inhibition constants were 16 microM and 9 microM, respectively.

Phosphonoformate inhibition of visna virus replication

Phosphonoformate (PFA) inhibits multiplication of visna virus in sheep choroid plexus cells; a 50% reduction of virus yield was obtained by 20 to 80 microM PFA. Morphological changes, such as syncytial formation and cell degeneration, could be reversibly prevented by PFA. Cell growth was not significantly affected at 500 microM PFA, although prolonged treatment with 2 mM PFA did arrest cell growth. Cell-free reverse transcriptase activity primed with various synthetic template-primers was inhibited about 90% in the presence of 100 microM PFA. The results from kinetic experiments suggested that reverse transcriptase was utilized early but not late in the infection cycle. A structurally related substance, phosphonoacetate, did not inhibit visna virus multiplication and had no inhibitory effect on reverse transcriptase activity at a concentration of 500 microM.

Effect of homopolyribonucleotides on messenger ribonucleoprotein particles

A discrete set of polypeptides copurify with and appear to be specifically attached to mRNA from polysomes of eukaryotic cells. This report describes the effect of homopolyribonucleotides on mRNA-protein complexes separated from ribosome subunits by oligo(dT)-cellulose chromatography. It is shown that poly (U) and poly (A) can release mRNA-protein complexes adsorbed to oligo(dT)-cellulose, whereas poly (C) and poly(I) are much less effective in this process. Analysis of polyribonucleotide released material showed that poly(U) effectively dissociated the mRNA-protein complexes while poly(A) caused no or only partial derangement of these particles. The specificities seen in the polyribonucleotide effects in turn suggest a high degree of specificity in the interaction between the proteins and mRNA.

Characterization of mRNA-protein complexes from mammalian cells

In a previous report we described the use of oligo(dT)-cellulose for the isolation of mRNA-protein complexes from EDTA-dissociated polysomes extracted from normally growing or adenovirus infected KB-cells (I). Experiments presented here provide evidence that proteins involved in these complexes bind specifically to mRNA since: a) the proteins and mRNA cosediment through sucrose gradients, b) they adsorb and elute from oligo(dT)-cellulose together, and c) analysis of the products from ribonuclease digestion experiments show that the poly (A) end and a separate small fraction of the mRNA are resistant to the enzymes and attached to protein.

Assembly of adenoviruses

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified incomplete particles of adenoviruses type 2 and 3 revealed that core proteins V and VII and capsid proteins VI, VIII, and X were absent in these particles, but they contained polypeptides not present in complete particles. Two types of incomplete particles were observed in the electron microscope, appearing as deoxyribonucleic acid-less particles with single discontinuities in the capsid structure (about 80%), or more amorphous particles resembling hexon aggregates (about 20%). The amount of incomplete and complete particles increased in parallel during the infectious cycle. Detectable amounts were found at 13 h with a maximum rate of synthesis for both particles at 24 h after infection. (3)H-labeled amino acids were incorporated into incomplete particles without a detectable lag period, but the label appeared in complete particles with a 60- to 80-min lag. Early after the pulse in pulse-chase experiments, the radioactivity was higher for incomplete particles than for complete particles and leveled off before the activity of complete particles reached a maximum. In the adenovirus type 2 system, pulse-chase experiments suggested a precursor-product relationship between incomplete and complete particles. After a short pulse, 19 h postinfection, entrance of (3)H-labeled amino acids into the hexon polypeptide of complete particles was delayed for 80 min, but no delay was observed for the labeling of the hexon polypeptide of incomplete particles. The core polypeptides appear in complete particles without a delay, also suggesting that incomplete particles were precursors to complete particles. Incorporation of (3)H-labeled amino acids into the hexon polypeptide of complete and incomplete particles was drastically decreased by inhibition of protein synthesis with emetine. However, the uptake of label into core proteins of complete particles was only decreased to 50% on inhibition of protein synthesis. The results suggest that incomplete particles are intermediates in virus assembly in vivo and that the assembly of capsid polypeptides into incomplete and complete particles is dependent on continuing protein synthesis.

Mechanism of the arginine requirement for adenovirus synthesis. I. Synthesis of structural proteins

The mechanism of the arginine requirement for adenovirus was studied in cultures of KB cells infected with adenovirus type 2. Macromolecular synthesis was found to be severely impaired in uninfected cells under complete arginine deprivation, whereas an arginine concentration of 50 mum yielded a moderate and reversible inhibition of growth and nucleic acid synthesis. At this concentration, viral structural proteins were accumulated in excess although the virus yield was reduced more than 1,000-fold. The arginine-sensitive step appeared to occur early during the first 15 hr postinfection in the virus growth cycle. Virus-infected cells deprived of arginine to 50 mum showed, when reversed, a 4- to 5-hr lag period before the increase in virus growth was observed. Analysis of the radioactive pattern of labeled virions synthesized after reversion showed that all polypeptides were synthesized after addition of arginine to the medium, and none of the virion-polypeptides which are revealed by gel electrophoresis appeared to be preferentially synthesized after arginine reversion. The excess pool of structural proteins formed during depletion appeared to a large extent to be unavailable for virus assembly.