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Detection of antibody to recombinant proteins derived from hepatitis C virus (HCV) genotype 1 represents the principal method for diagnosis of HCV infection. A method was developed for quantifying antibody reactivity in two third-generation enzyme immunoassays (Ortho EIA 3.0 and Murex VK48), and the influence of viraemia, HCV genotype, and host factors such as age, gender, and risk group upon antibody levels were investigated in a consecutive series of 117 anti-HCV-positive volunteer blood donors. Viraemic donors (as assessed by the polymerase chain reaction; PCR) showed significantly higher levels of anti-HCV by the Ortho EIA than those who were nonviraemic (adjusted mean difference of 10.1 fold after multiple regression analysis). The only other factor to influence significantly antibody level was genotype, where it was found that donors infected with type 1 showed 4 to 4.5 times greater serological reactivity by the Ortho assay than those infected with type 2 or 3. Antibody levels by the Ortho assay correlated closely to those detected by the Murex VK48 assay, and similar differences between PCR-positive and negative donors and between those infected with different genotypes were found. Differences in serological reactivity between genotypes indicate that a large proportion of epitopes of the type 1a or 1b recombinant proteins used in current assays are genotype specific. Variation in sensitivity of screening assays for different genotypes is of potential concern when used in countries where non-type 1 genotypes predominate in the blood donor or patient population.

All blood donors in Scotland who were found to be infected with hepatitis C virus (HCV) in the first 6 months of routine testing of all donations for anti-HCV were contacted. Those who attended were counselled, a history of exposure to risk was sought, and blood was taken for alanine aminotransferase (ALT) level as a measure of liver function. The epidemiological features were then correlated with the virological findings and ALT. In the period under study between September 1991 and February 1992, 180,658 blood donors attended. The prevalence of HCV infection was 0.088%. Of the 151 donors who attended for counselling, 101 (68%) were male. Intravenous drug use was the most common risk activity (39%), followed by previous blood transfusion (15.2%), other parenteral exposure (11.2%) and heterosexual contact with a parenterally infected partner (8.6%); 29.1% of donors gave no history of possible exposure. Elevated ALT levels were found in 59%. ALT levels were higher in donors with HCV types 1 and 3 than in HCV type 2 or non-viraemic donors. The prevalence of HCV in Scottish blood donors is thus relatively low. This may relate to the effectiveness of donor selection procedures, but donors with risk activities which should debar them continue to donate. The combination of ALT and PCR appears to be useful in counselling and assessing infected donors.

The frequency of infection with the six classified major genotypes of hepatitis C virus (HCV) was investigated in 447 infected volunteer blood donors from the following nine countries: Scotland, Finland, The Netherlands, Hungary, Australia, Egypt, Japan, Hong Kong, and Taiwan. Viral sequences in plasma from blood donors infected with HCV were amplified in the 5'-noncoding region and were typed by restriction fragment length polymorphism analysis. Electrophoresis of DNA fragments produced by cleavage with HaeIII-RsaI and ScrFI-HinfI allowed HCV types 1 (or 5), 2, 3, 4, and 6 to be identified. Further analysis with MvaI-HinfI allowed sequences of the type 5 genotype to be distinguished from sequences of the type 1 genotype. Types 1, 2, and 3 accounted for almost all infections in donors from Scotland, Finland, The Netherlands, and Australia. Types 2 and 3 were not found in the eastern European country (Hungary), where all but one of the donors were infected with type 1. Donors from Japan and Taiwan were infected only with type 1 or 2, while types 1, 2, and 6 were found in those from Hong Kong. HCV infection among Egyptians was almost always by type 4. Donors infected with HCV type 1 showed broad serological reactivity with all four antigens of the second generation Chiron RIBA-2 assay (Chiron Corporation, Emeryville, Calif.), while infection with divergent HCV genotypes elicited antibodies mainly reactive to c22-3 and c33c. Reactivities with antibodies 5-1-1 and c100-3 were infrequent and were generally weak, irrespective of the geographical origin of the donor. Because the envelope region of HCV is even more variable than the NS-4 region, it is likely that vaccines based on these proteins need to be multivalent and perhaps specifically adapted for different geographical regions.

Hepatitis C infection (HCV) is more prevalent in patients who have received kidney transplants than in the general population but the morbidity and mortality associated with infection in this group is unclear. Sera taken from 36 renal transplant recipients with chronic liver dysfunction and from 42 with normal liver function were tested for HCV infection by second generation ELISA (Abbott Laboratories) and second generation recombinant immunoblot assay (Chiron Corporation) (RIBA-2). Evidence of HCV replication was sought by reverse transcription poly-merase chain reaction (RT PCR) using primers from the 5′ nontranslated region (5′NTR). Infection was detected in 20/36 (54%) and in 2/42 (4.8%) controls (P < 0.01). Twelve liver dysfunction patients were positive by all three tests, six were positive by ELISA and RT PCR but had indeterminate RIBA-2, one was positive by ELISA and RIBA but negative by RT PCR, and one was positive only by RT PCR. Of two infected control patients, one was positive by all three tests and one who was later found to have been in the early stage of infection was positive only by RT PCR. Follow-up of infected patients showed persistence of viraemia in 14/15 (93%). Evidence of infection with different types of HCV was shown by the lack of amplification by RT PCR by primers with mismatching bases with HCV types 2 and 3. It is concluded that in our renal transplant patients, chronic HCV infection is usually associated with liver dysfunction and persistent infection is common. © 1994 Wiiey-Liss, Inc.

The effect of sequence variability between different types of hepatitis C virus (HCV) on the antigenicity of the NS-4 protein was investigated by epitope mapping and by enzyme-linked immunosorbent assay with branched oligopeptides. Epitope mapping of the region between amino acid residues 1679 and 1768 in the HCV polyprotein revealed two major antigenic regions (1961 to 1708 and 1710 to 1728) that were recognized by antibody elicited upon natural infection of HCV. The antigenic regions were highly variable between variants of HCV, with only 50 to 60% amino acid sequence similarity between types 1, 2, and 3. Although limited serological cross-reactivity between HCV types was detected between peptides, particularly in the first antigenic region of NS-4, type-specific reactivity formed the principal component of the natural humoral immune response to NS-4. Type-specific antibody to particular HCV types was detected in 89% of the samples from anti-HCV-positive blood donors and correlated almost exactly with genotypic analysis of HCV sequences amplified from the samples by polymerase chain reaction. Whereas almost all blood donors appeared to be infected with a single virus type (97%), a higher proportion of samples (40%) from hemophiliacs infected from transfusion of non-heat-inactivated clotting factor contained antibody to two or even all three HCV types, providing evidence that long-term exposure may lead to multiple infection with different variants of HCV.

The serological reaction to HIV infection is almost invariably a dynamic progression towards strong reactivity to a wide range of viral antigens. Serological diagnosis should therefore be based either on the presence of this wide range in a single specimen or on the demonstration of increasing activity between two specimens collected at an interval of two or more weeks and tested in parallel. When a specimen is reactive a second should in any case be collected to check the identity of the first. These precepts are sometimes being ignored, especially in non-clinical testing, e.g., for purpose of life assurance. Two recent cases in which there were false but unchanging enzyme immunoassay and Western blot reactions that might have been interpreted as positive illustrate the potential for error.

A method is described for identifying different genotypes of hepatitis C virus (HCV) by restriction endonuclease cleavage of sequences amplified by PCR from the 5′ non-coding region. Using the enzymes HaeIII-RsaI and HinfI-MvaI, followed by cleavage with BstU1 or ScrFI, it was possible to identify and distinguish HCV genotypes 1a, 1b, 2a, 2b, 3a, 3b, 4, 5 and 6. The method was used to investigate the prevalence of these genotypes in 723 blood donors in 15 countries, the largest survey to date, and one which covered a wide range of geographical regions (Europe, America, Africa and Asia). These results, combined with a review of the existing literature, indicate the existence of several distinct regional patterns of HCV genotype distribution, and provide the framework for future detailed epidemiological investigations of HCV transmission.

Two hundred Asian and 100 each of African, Chinese, and Scottish children were screened for intestinal parasitic infestations, salmonellosis, brucellosis, hepatitis B antigen (HBsAg), and tuberculosis. There was a fairly high incidence of Giardia lamblia among Asian and Scottish children and of Trichuris trichiura among the Chinese. Hookworm ova were seen only in Africa children. There were no chronic carriers of Salmonella or Brucella, and no one was suffering from salmonellosis or brucellosis. Tuberculin sensitivity was found in only 4% of immigrant and 1% of Scottish children: the difference was small and neither figure suggests a continuing high incidence of tuberculosis in Glasgow. Only seven immigrant children were found to be HBsAg carriers. Among the families of these carriers there was a high incidence (84%) of HBsAg or antibody (HBsAb). The survey shows that immigrant children in Glasgow do not constitute a health hazard to the indigenous population. Moreover, severe overcrowding is not a prominent feature among the immigrant families in Glasgow but is greatest among the local Scots.

Liver function was studied in 139 of 291 haemophiliacs known to a single Regional Haemophilia Centre including patients with classical haemophilia, Christmas disease and von Willebrand's disease. In 57 patients, six-monthly liver function tests over a five year period were also available. Thirty-nine of the 139 patients had had jaundice or hepatitis and 56 had a positive test for HBsAb in the blood although few of these had had an identifiable clinical illness. Fifty-eight haemophiliacs had elevated serum aminotransferases at the time of study, but the five year review revealed only six patients who had had persistently abnormal results, although none had clinically evident liver disease. Liver dysfunction was unrelated to a history of hepatitis, to a positive HBsAb test, or to age, type of haemophilia, factor level or frequency of factor replacement treatment. Abnormalities of liver function in haemophilia appear to be unrelated to past or present hepatitis B infection in most cases and may not be related to any single transmitted infectious agent.

The growth of vaccinia virus in monolayers of BSC-1 cells enucleated by centrifugation in the presence of cytochalasin B has been studied. No evidence for the production of infectious virus in these cells was obtained, and the production of virus particles was reduced to 8.3% compared with the yield from cytochalasin-treated, uncentrifuged cells. Virus DNA and early and late polypeptides were synthesized with normal timing in enucleate cells, but in reduced amounts; cleavage of structural polypeptide precursors P4a and Px also occurred in enucleate cells. Factories containing immature virus particles were demonstrated in enucleate cells by electron microscopy; these factories were reduced in number and size compared with those found in cytochalasin-treated, uncentrifuged cells.

SummarySince 1973 epidemiological surveillance of laboratory-confirmed hepatitis B virus infection has been undertaken in Scotland. During the ten-year period, 1973–82, 2893 persons with laboratory evidence of infection were reported and the number increased by almost threefold between the beginning and the end of this time. Males accounted for 66 % of the patients and intravenous drug abuse was the most commonly encountered risk factor. The low risk to laboratory staff is confirmed, but among National Health Service hospital staff nurses accounted for 54% of those reported.

The requirement of the presence of a nucleus for the replication of vesicular stomatitis virus and influenza virus has been examined by following the growth and development of these viruses in enucleate BS-C-1 cells. Vesicular stomatitis virus replicates normally in enucleate cells with the rate of production of infectious virus, the amount of virus-specific protein synthesis, and the type of proteins produced being essentially the same in nucleate and enucleate cells. Influenza virus does not replicate in enucleate cells, no virus gene products can be detected, and there is no inhibition of cellular protein synthesis.

The development of measles virus (Edmonston) and SSPE measles virus (Horta-Barbosa) has been examined in enucleate BSC 1 cells. New antigen synthesis in measles virus infected enucleate cells has been demonstrated by fluorescent antibody, by the formation of extensive syncytia from enucleate cells alone and by analysis of polypeptide formation by polyacrylamide gel electrophoresis. All polypeptides formed in nucleate cells were also present in enucleate cells but the amount synthesized was reduced to around 20% of that in nucleate cells. There was also a significant reduction in the amount of antigen detected by fluorescent antibody in enucleate as compared to nucleate preparations. Examination of RNA synthesis in infected enucleate cells revealed only a marginal increase in acid-insoluble material. Titration of the output of infectious virus from enucleate cells infected at both 37 and 31 degrees C indicated a consistent reduction of almost two log units compared to nucleate cells. That the enucleate cells were capable of replicating input genome at these times was demonstrated by the successful growth of respiratory syncytial virus, both at 37 and 31 degrees C. SSPE measles virus grew to higher yield in nucleate BSC 1 than measles virus but there was again a reduction of more than two log units in enucleate cells. All polypeptides synthesized in SSPE infected nucleate cells were apparent in enucleate cells.

The mineralogy of the clay fractions of two soil profiles representing the end-members of a catena developed on a glacial till derived from basic lavas has been determined. Particular attention has been given to the assessment of the nature of the amorphous inorganic material in the clay fraction of these soils. Chemical dissolution techniques were used and their effects on the clay fraction were followed by X-ray diffraction, differential thermal, infrared absorption, electron-optical and surface area measurements. The principal conclusion is that the soil clays are a continuum from completely disordered, through poorly ordered to well crystallized material.

The removal of the alkali-soluble fraction from soil clays has been found to influence markedly the efficiency with which iron oxides can be removed from such clays. In clays pretreated with 5% Na2CO3, up to 40% more iron oxide was extracted by dithionite (Na2S2O4) than from soil clays treated with this reagent alone. Chemical analysis, electron microscopy, X-ray and differential thermal examination, and specific surface area and cation-exchange capacity measurements indicated an improved dispersion brought about by the removal of aluminosilicate binding material by Na2CO3. The electron-optical studies also showed that the dithionite-soluble iron was principally in the form of small granules. These were amorphous to X-rays and electrons and chemical analysis of the dithionite-soluble fraction suggested that they were ferruginous complexes containing considerable quantities of silica and alumina.

Ultra-thin sections of a synthetic graphite have been examined in the electron microscope before and after oxidation in air at a temperature of 500 °C. In unirradiated material, micrographs of individual areas showed that oxidative attack occurred at grain boundaries and at pores between individual crystallites. Parallel experiments on material which had been irradiated to a dose of 8.7 x 10 19 n .v .t. again showed etching at pores and at grain boundaries, but, in addition, in the majority of specimens, a shallow surface pitting of the entire (0001) faces of the individual crystallites took place. The density of these shallow pits varied from 5 x 10 10 /cm 2 to 5 x 10 u /cm 2 . Variations in reaction rate were observed and were traced to impurity which, especially when metallic, greatly increased the oxidation rate. In unirradiated graphite, this impurity appeared to be absorbed only at pores and intercrystallite boundaries, oxidation effects being observed only at these sites. In irradiated material impurity was also absorbed at sites on the (0001) crystal faces where oxidation produced etch pits of widely varying depth and density. Channelling of the (0001) layer nets occurred in both irradiated and unirradiated specimens. Annealing of the irradiated graphite at 650 °C for 1 h produced no significant change in the pattern of attack by oxygen. The observed etch pit density measured on the (0001) layer nets was 8 x 10 10 cm 2 . A mechanism for pit formation relating pit density and vacancy content is proposed. The general appearance of irradiated samples differed from the unirradiated in that the well-defined moire patterns characteristic of thin sections of synthetic graphite were absent in irradiated samples, but reappeared when the samples were annealed at 650 °C. This change is related to the known behaviour of interstitial atoms in graphite on annealing the materials

Summary Examination of the physical structure of cauliflower mosaic virus DNA by electron microscopy and ultracentrifugal analysis showed that the DNA could be isolated mainly as a circular molecule of mol. wt. 4.7 × 106. Nearest-neighbour frequency analysis showed that the DNA has a chemical structure which exhibits close similarities to that of the host cauliflower DNA. The relationships of this plant virus DNA and the small mammalian virus DNAs to the DNA of their respective hosts are discussed.

The ultra-microtome has been used to obtain thin sections of synthetic graphite blocks. The thickness of the sections was measured by shadowcasting and measuring the shadow length at appropriate edges. An average value of 150 Å was obtained. Transmission electron micrographs of thin sections showed moire patterns and the interrelation of these moire patterns revealed a characteristic grain structure in graphite akin to that seen in metals but with component microcrystals of smaller dimensions. The area of the individual micro - crystals forming the grain structure was measured and was found to be 0·11 + 0·074μ 2 . The boundary between neighbouring microcrystals was narrow and of around 50 A in width. Pores were visible at the junction of three or more contiguous microcrystals and were of diameter 400 to 800 Å. The selected-area electron diffraction technique was used to determine the orientation of individual microcrystals in the graphite sections. It was found that the hexagonal layer net planes were lying parallel or at a very small angle to the plane of the section. The electron diffraction patterns were also used to correlate the layer stacking faults in individual microcrystals both by counts of individual reflexions on the (1120) diffraction ring and by counts of the extra reflexions due to the long spacings between successive displaced layers. The average value of 13 Å found for the distance between successive stacking faults is equivalent to the distance between four hexagonal layer net planes. The moire patterns in the electron micrographs could be related to the long spacings in the electron diffraction patterns. It was possible to calculate the angle of twist between successive stacking faults from the long spacing or from the moire pattern. Dislocations were seen in many of the thin sections and were observed as extra terminating half-lines in the moire patterns; these dislocations were present in the hexagonal layer net planes themselves and indicated that there was in this region a considerable deformation of the benzenoid structure of the hexagonal layer nets. The measured frequency for their occurrence was 3·3 x 10 7 /cm 2 . Slip planes were also detected in some specimens.

The relationship between culture density and the number of microvilli on the cell surface has been studied using BHK21 cells in established monolayer culture. The number of microvilli can be estimated quantitatively by a scanning electron-microscope technique. It can be increased by applying specific antiserum, but whether antibody is applied or not a significant number of cells regularly bear microvilli. This number is characteristic of the culture density. In sparse cultures above a certain minimum density it is relatively high, and in confluent cultures it is much reduced. These results indicate that microvilli may be inhibited by cell contact.

We tested 150 patients infected with human immunodeficiency virus (HIV) for the presence of oligoclonal bands in serum, prompted by reports that these abnormal proteins may have prognostic significance. Sixty HIV-negative individuals from "at-risk" groups were tested along with 80 HIV-negative, healthy blood donors for the presence of these bands. All sera were tested by isoelectric focusing, because it is more sensitive for this purpose than more-conventional electrophoretic techniques. In the HIV-positive group, 61% of the sera had oligoclonal bands; in the HIV-negative "at-risk" group, 36% had bands. No bands were detectable in sera from the healthy blood-donor group. Some patients were also followed for differing periods throughout their infection, and changes in their oligoclonal banding patterns could not be correlated with disease progression. The fact that oligoclonal bands were found to be present without HIV infection in a substantial number of individuals from within the "at-risk" groups leads us to conclude that the presence of oligoclonal bands in HIV infection is of limited prognostic significance.

The cell mediated immune response was evaluated in vivo in 29 patients with clinically severe haemophilia by means of the dinitrochlorobenzene skin test. All patients had a response below the median normal value, and in 19 the response was on or below the lower limit of the normal range. There was no difference in skin response between patients positive and negative for the human immunodeficiency virus (HIV; formerly known as human T cell lymphotropic virus III or lymphadenopathy associated virus). In the whole group, and in seronegative patients (n = 17), there was an inverse relation between exposure to clotting factor and skin response. In seropositive patients (n = 12) no such association was apparent. This study shows that clotting factor concentrate impairs the cell mediated immune response to a new antigen in the absence of infection with HIV.

In 1983 304 serum samples, and in 1984 432 serum samples submitted to the Hepatitis Reference Laboratory, Ruchill Hospital, Glasgow were found to be positive for HBsAg by radio-immunoassay. Of these, 37 in 1983 and 50 in 1984 were from persons less than 18 years, while 38 and 46 respectively were from persons greater than 39 years. This increase from 1983 to 1984 was due to more acute infections among males. In males less than 18 years, infections were related to drug abuse, whereas in men greater than 39 years sexual transmission appeared to be the main source. Women greater than 39 years may be at increased risk of infection from other members of the household. A finding of HBsAg in a person greater than 39 years is likely to be from an acute infection as from a carrier.

SUMMARYThe molecular epidemiology of rotavirus infections in Glasgow and the west of Scotland during 1981/82 and 1982/83 was investigated by electron microscopy, ELISA testing and RNA migration pattern analysis. In 1981/82, rotaviruses of both the ‘long’ and the ‘short’ electropherotype (in different variants) co-circulated from the onset throughout the winter peak of the outbreak. Approximately 80 % of the children were infected during the first year of life. No differences in incidence were found between sexes. In 1982/83 the isolated rotaviruses were almost exclusively of the ‘long’ electropherotype (in different variants) and 36% of the children were infected beyond the first year of life. Rotaviruses of the ‘long’ electropherotype serologically were of subgroup II and serotype 1 and those of the ‘short’ electropherotype of subgroup I and serotype 2.

The prevalence of anti-HAV in blood donors in West Scotland and in children admitted to a Glasgow hospital was determined. By the age of five years, 16% of the children had antibody and at 15 years, 30%. In adults, prevalence continued to rise with age, with 78% of those over 40 years showing evidence of past infection. Cases of acute hepatitis A in West Scotland have declined since 1983. At present the peak age group for infection is 25–34 years whereas in the early 80s the peak group was five to 14 years.

Summary A group of RNA viruses, echovirus, poliovirus, reovirus, respiratory syncytial virus and Semliki Forest virus have been examined for ability to grow in enucleate African green monkey kidney (BSC1) cells. Semliki Forest virus produced an almost normal yield of virus but poliovirus, echovirus, reovirus and respiratory syncytial virus, although showing clear evidence of virus replication when compared with a nuclear DNA virus (pseudorabies virus) gave much lower yields than those from nucleate cells. Analysis of enucleate cells infected with echovirus and reovirus showed no evidence of a specific block in the synthesis of any virus-specified polypeptide. Infection with vesicular stomatitis virus at intervals after enucleation demonstrated a diminishing ability to support virus growth with increasing time. It is suggested that the yield of virus obtained from an enucleate cell is related to the length of the growth cycle of the virus, the reduced yield obtained with some viruses reflecting the declining ability of the enucleate cell to support virus growth.

In 1979, 43 cases of acute hepatitis A infection were diagnosed by the presence of hepatitis A specific IgM antibodies in acute phase sera. The majority (34) were in patients under 30 years with 13 in children under 10 years: 23 were males. Few cases occurred in the winter months, most in autumn, with a peak in September. A total of 17 cases had a history of recent travel abroad, and six of contact with a case of jaundice/hepatitis. There were 11 cases in members of the immigrant community.

In a study of 195 patients derived from five centres in northern Britain and with histologically confirmed alcoholic liver disease we have found an increased prevalence of serological markers of hepatitis B. This increased prevalence was found in each of the five centres; the overall frequency ranged from 11% sero-positivity in fatty liver, 12% in alcoholic hepatitis and 27% in cirrhosis.

The effect of a number of rifamycin derivatives and related compounds on the reversibility of the rifampin-induced virus maturation block was studied by using BHK-21 cells infected with vaccinia virus. All of the derivatives of 3-formyl rifamycin SV maintained this block, the required concentration varying from 100 to 1,000 μg/ml. These compounds vary only in the nature of the side-chain attached to the 3C atom on the naphthohydroquinone moiety; no obvious correlation between the nature of this side-chain and antiviral activity was found. Streptovaricin complex and tolypomycin R also maintained the maturation block; tolypomycin also produced marked alterations in the appearance of the viroplasm contained in rifampin-induced inclusions and immature virus particles.

Summary Infectivity titration, sedimentation analysis in sucrose gradients and electron microscopy have been used to study virus maturation following the reversal of the inhibition of vaccinia virus growth by rifampicin. Electron-dense inclusions containing tubular structures develop in the cytoplasm of infected BHK 21/C 13 cells maintained in rifampicin, but the formation of immature and mature virus particles is prevented. The removal of rifampicin is followed by a rise of the virus infectivity. Spicule-covered membranes appear at the periphery of the inclusions and both immature and mature virus particles are seen. A proportion of the DNA synthesized in the presence of rifampicin is incorporated into particles and becomes resistant to deoxyribonuclease I. If protein synthesis is inhibited, spicule-covered membranes and immature particles appear but no mature particles are seen; the virus infectivity does not increase and the DNA remains susceptible to deoxyribonuclease I. It is suggested that rifampicin binds reversibly to a virus-specified protein, thereby preventing the formation of immature virus particles. Possible effects of rifampicin on the subsequent stages of virus maturation are discussed.

THE antibiotic rifampicin inhibits the growth of bacteria by inhibiting DNA dependent RNA polymerase1,2. It also inhibits the growth of vaccinia and other poxviruses3,4. An interaction between the antibiotic and the viral polymerase has not been demonstrated, however, and the antiviral mode of action of the drug remains unknown.

Summary Rabbit kidney vacuolating virus is similar to polyoma virus in the size and structure of the virus particle. The DNA of the virus is also similar to the DNA of polyoma virus, being supercoiled and circular with a molecular weight of approximately 3 million. The base composition of the DNA, 43% guanine plus cytosine (GC), is intermediate between that of polyoma virus DNA, 48% GC, and that of simian virus 40 DNA, 41% GC. It is concluded that rabbit kidney vacuolating virus should be placed with polyoma virus and simian virus 40 as a member of the polyoma group of viruses.

The cell surface of a non-fruiting myxobacterium,Cytophaga johnsonii, was investigated by electron optical techniques. Negative staining revealed an irregularly undulating surface topography and the presence of strands of material arising from the cells. Replicas of freeze-dried cells and thin sections confirmed the uneven nature of the surface and showed that, in contrast to eubacteria, the cell was surrounded by an envelope of amorphous, electron-translucent material contained within a crenated, outer, “unit” membrane. This material could be extruded as long strands. It is considered that this envelope of material represents the slime layer of the organism. The appearance of the slime layer at various stages in the growth of the organism was followed by negative staining and the image of the organism presented by negative staining was compared to that given byMyxococcus xanthus andFlavobacterium aquatile.

SUMMARY: Electron microscopic study of vibrio flagella by using the negative staining technique revealed differences in chemical reactivity as between the sheath and core components. The sheath was easily degraded by autolysis and exposure to acid and urea, whereas the core was relatively resistant. These differences suggest that the sheath and core are of different composition and that, whereas the core consists of the protein ‘flagellin’, the sheath is probably of cell-wall origin.

Summary The nearest neighbour frequency pattern analyses of the DNAs of a minute virus of mice, Kilham rat virus and H-1 virus were very similar to each other. They were also similar to the pattern of the host cell DNA, apart from differences related to structure, the virus DNAs being single-stranded and the host double-stranded. All three DNAs exhibited the low frequency of the dinucleotide sequence CpG previously found in mammalian DNAs and in the nucleic acids of small mammalian viruses. The sizes and densities of the virus particles were measured, and the molecular weight of H-1 DNA was determined.

Summary The base composition of DNA from a minute virus of mice was determined by hydrolysis of 32P-labelled DNA to give 3′ and 5′ nucleotides. The analyses were consistent only with a single-stranded structure for the virus DNA. This was confirmed by the results of nearest neighbour base sequence analyses. Comparison of minute virus of mice with phage φX 174 and adeno-associated virus type 1 showed a close similarity of minute virus of mice and φX 174 and suggested that all three small DNA virus particles contain not more than 1.7 × 106 daltons of DNA.

Defective particles were the major product after undiluted passage of certain temperature-sensitive ( ts ) mutants of the Indiana C strain of vesicular stomatitis virus in BHK-21 cells at the permissive temperature (31 C). Essentially homogeneous preparations of defective particles were obtained with the wild-type and individual ts mutants. The defective particles associated with some of the ts mutants, however, were morphologically and physically distinguishable from wild type and from each other. All varieties of defective particle interfered with the multiplication of mutant and wild-type virus at the permissive temperature at early times of infection but failed to complement virions of different complementation groups at the restrictive temperature (39 C) at any time during infection.

Interferon induces protection of enucleated BSC-1 cells against infectious vesicular stomatitis virus production if cells are treated before, but not after, enucleation.