Compact zinc finger architecture utilizing toxin-derived cytidine deaminases for highly efficient base editing in human cells

Nucleobase editors represent an emerging technology that enables precise single-base edits to the genomes of eukaryotic cells. Most nucleobase editors use deaminase domains that act upon single-stranded DNA and require RNA-guided proteins such as Cas9 to unwind the DNA prior to editing. However, the most recent class of base editors utilizes a deaminase domain, DddAtox, that can act upon double-stranded DNA. Here, we target DddAtox fragments and a FokI-based nickase to the human CIITA gene by fusing these domains to arrays of engineered zinc fingers (ZFs). We also identify a broad variety of Toxin-Derived Deaminases (TDDs) orthologous to DddAtox that allow us to fine-tune properties such as targeting density and specificity. TDD-derived ZF base editors enable up to 73% base editing in T cells with good cell viability and favorable specificity.

Behavioral risk factors for disease and preventive health practices among lesbians

OBJECTIVES

This study compared the prevalence of health behaviors among lesbians and in the general population of women.

METHODS

We used a cross-sectional community-based survey of 1010 self-identified lesbians 18 years or older.

RESULTS

Compared with the general population of women, lesbians were more likely to report cigarette use, alcohol use, and heavy alcohol use. A higher percentage of lesbians were categorized as overweight, and lesbians were more likely to participate in vigorous physical activity. They were less likely to report having had a Papanicolaou test within the past 2 years but more likely to report ever having had a mammogram.

CONCLUSIONS

While there may be differences in health behaviors between lesbians and the general population of women, how these differences influence the risk of subsequent disease is unknown.

Epitopes functional in neutralization of varicella-zoster virus

By competition neutralization assay using monoclonal antibodies (MAbs) to varicella-zoster virus (VZV) glycoproteins (gps), we attempted to determine the topographical relationship of epitopes which are functional in VZV neutralization. MAbs against gpI interfered moderately to strongly with neutralization of MAbs against gpIII, and one antigenic domain with two distinct epitopes was identified on gpIII. Competition neutralization assays performed with MAbs to gpI revealed at least three distinct antigenic domains: the first contained two complement-dependent neutralizing epitopes; the second contained five complement-dependent neutralizing, overlapping epitopes and one nonneutralizing, nonoverlapping epitope; and the third contained one complement-enhanced neutralizing epitope. Competition neutralization assays performed with MAbs to gpIV showed one antigenic domain with two distinct epitopes which competed with nonneutralizing gpI MAbs. gpII did not interfere with neutralization of gpI, gpIII, or gpIV. Our data suggest that neutralizing and nonneutralizing MAbs can interfere with the action of viral neutralization either by inhibition or by enhancement. This report describes the epitope mapping of VZV gps by a functional biological assay.

Sensitivity of different assay systems for immunoglobulin M responses to varicella-zoster virus in reactivated infections (zoster)

An immunoglobulin M response to varicella-zoster virus was detected in 70% of zoster patients by solid-phase radioimmunoassay, in 52% by indirect immunofluorescence, in 48% by neutralization on sucrose density gradient fractions, and in 27% by an antibody class capture enzyme immunoassay. The patients showed marked variations in their varicella-zoster virus immunoglobulin M responses detectable in the different assays.

Rapid detection of herpes simplex virus DNA in human brain tissue by in situ hybridization

A commercial system for detection of herpes simplex virus (HSV) DNA by in situ hybridization gave positive results on 16 of 17 stored human brain specimens that were positive for HSV on initial testing by virus isolation and immunofluorescence staining, and the hybridization system gave negative results on 13 brain specimens that showed no evidence of HSV by isolation or immunofluorescence staining.

Racial differences in incidence of juvenile-onset type 1 diabetes: epidemiologic studies in southern California

We have studied the epidemiologic characteristics of insulin-dependent (Type 1) diabetic patients aged 0-19 in a city (San Diego, southern California, USA) characterized by an impressive racial diversity and especially mild and constant climatic conditions. Ascertainment was through retrospective review of medical records in 19 hospitals. For the 3 years 1978-1981 the mean annual incidence of diabetes was 7.3 cases/100,000, with no statistical difference between the sexes. The observed incidence rates in the various ethnic groups was significantly different from expected (p less than 0.03), with an excess of cases among Caucasians and fewer than expected cases among Mexicans, Blacks and Orientals. There was no identifiable seasonal trend. Some of the clinical characteristics at diagnosis differed between the sexes: males were slightly older (9.3 +/- 5.2 years versus 8.8 +/- 3.9 for females), had a shorter duration of diabetes-related symptoms and a higher frequency of infections both at the time of diabetes diagnosis and in preceding months. Females tended to have a higher frequency of Type 1 diabetes in first-degree relatives. This study documents for the first time that, among multiple racial groups living in the same environment, Caucasians are at the highest risk of developing juvenile-onset Type 1 diabetes.

Diabetogenic potential of coxsackie B viruses in nature

Thirty-seven clinical isolates of coxsackievirus (CV) serotypes B-1, B-3, B-4, and B-5 were inoculated into male SJL mice. Twelve strains resulted in minor abnormalities of glucose metabolism in one or more of six infected mice (Tables 1 and 2). Sequential infection of male SJL mice with CVB-3, CVB-4, and CVB-5 resulted in abnormal glucose metabolism in 25 percent of the mice (Fig. 1). The glucose index of the abnormal animals was similar to that produced by sequential infection with reovirus and cytomegalovirus but less than that seen with more severe beta cell tropic agents such as streptozotocin or encephalomyocarditis virus. Infection of autoimmune New Zealand (NZB X NZW) F1 male mice with CBV-3, CVB-4, and CVB-5 resulted in transient elevation of the blood glucose concentration associated with acute acinar pancreatitis (Fig. 2). In spite of recent evidence that infection with the coxsackie B viruses can result in human diabetes mellitus, the diabetogenic potential of CVB field strains appears to be limited. Diabetes mellitus may occur as a rare event, limited to genetically susceptible hosts. Autoimmune mechanisms or repeated infection with other CVB serotypes may convert minimal beta-cell destruction into clinically overt disease.

Varicella-zoster viral glycoproteins analyzed with monoclonal antibodies

Monoclonal antibodies to varicella-zoster virus were used to study viral glycoproteins by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Based on the viral glycoproteins immunoprecipitated, the five monoclonal antibodies fell into three groups. Two antibodies, 4B7 and 8G9 (group 1), immunoprecipitated a single glycoprotein of molecular weight (MW) 118,000 (118K glycoprotein) and had high neutralizing activity in the absence of complement. One antibody, 3C7 (group 2), which lacked neutralizing activity, immunoprecipitated two glycoproteins of MWs 120,000 and 118,000 and a glycoprotein giving a diffuse band in the region of 64,000 to 65,000. Pulse-chase experiments and experiments with monensin as an inhibitor of glycosylation suggested that the 120K polypeptide was derived by glycosylation of the 118K polypeptide and that a 43K antigen was processed into the 64 to 65K glycoprotein. Two antibodies, 3G8 and 4E6 (group 3), both had neutralizing activity only in the presence of complement, and both immunoprecipitated at least five polypeptides, with MWs ranging from 50,000 to 90,000. Antibody 3G8 was isotype immunoglobulin G2b (IgG2b), and its immunoprecipitating activity was stronger than that of 4E6, which was isotype IgG1. Pulse-chase experiments with antibody 3G8 showed that lower-MW glycopeptides chased into three polypeptides of MWs 90,000, 80,000, and 60,000 by 24 h. Immunoprecipitation experiments with antibody 3G8 on infected cells treated with glycosylation inhibitors 2-deoxyglucose, monensin, and tunicamycin, suggested that a prominent, early-appearing 70K polypeptide may have been processed into the glycoproteins of higher MWs and that the 60K polypeptide may have been derived by glycosylation of polypeptides of lower MWs.

Coxsackievirus B3 persistence and myocarditis in N:NIH(S) II nu/nu and +/nu mice

N:NIH(S) II nu/nu (athymic) and +/nu (euthymic) mice were inoculated with coxsackievirus B3 (CBV-3) and examined at various times after infection for virus titres in the heart, myocarditis and serum neutralizing antibodies. Virus was recovered from the hearts of nu/nu mice for up to 94 days post-inoculation, but was not recovered from the hearts of any +/nu mice beyond 14 days. Inflammatory cell infiltration and necrosis were present in the hearts of +/nu mice at all harvest times (7, 14, 21 and 28 days). Inflammation and necrosis did not become evident in nu/nu mice until 14 days post-inoculation, and was the present in mice from each harvest until the end of the experiment (94 days). In athymic mice, myocarditis showed a strong correlation with persistence of CBV-3 in the heart. In N:NIH(S) II mice, the presence (+/nu) or absence (nu/nu) of a thymus had a major influence on the clearance of virus from the heart and on the development of myocarditis.

Coxsackievirus B3 persistence and myocarditis in NFR nu/nu and +/nu mice

NFR nude (nu/nu) and euthymic (+/nu) littermates were infected with coxsackievirus B3 (CBV-3) and assayed for virus persistence in the heart, pancreas and spleen, for development of myocarditis and for antibody production. The virus grew to higher titer and persisted longer in hearts of nu/nu mice. In both types of mice there was comparable myocarditis with a mononuclear cell inflammatory response, and there was some evidence of chronic lesions for up to 21 days in +/nu and 28 days in nu/nu mice. Antibody of the IgM class was present at 7 days in both strains of mice. Thereafter, +/nu mice produced high titers of virus-specific IgG antibody, while nu/nu mice produced little or no viral IgG antibody. The persistence of virus for up to 28 days in NFR nude mice is longer than has been reported previously, and offers an opportunity for further study of the role of T-cells in virus persistence and myocarditis.

Differing cardiotropic and myocarditic properties of group B type 4 coxsackievirus strains

A murine model system for evaluation of myocarditic and cardiotropic properties of strains of group B, type 4 coxsackievirus (CBV-4) was developed in male BALB/c mice 4 weeks of age. Differing cardiotropic and myocarditic properties could be identified among field strains within the CBV-4 serotype. These properties were consistent for the virus strains, and were independent of the infecting virus dose. Virus replication in the heart appeared to be essential for development of myocarditis, but some infected hearts with high levels of infectious virus did not show myocarditis. Two of the myocarditic strains showed different histopathology in infected hearts; with one strain (Mil) the myocarditis was characterized by a marked inflammatory reaction with occasional accompanying myofiber necrosis. With the other strain (Bol), necrosis was the predominant finding, with a much lesser degree of inflammation. These findings suggest that there may be various pathogenic or immunopathogenic mechanisms by which CBV-4 can produce myocarditis.

Antibody class capture assays for varicella-zoster virus

Pooled monoclonal antibodies to varicella-zoster virus (VZV) were used as "detector" antibodies in a four-phase enzyme immunofluorescence assay for determination of immunoglobulin M (IgM), IgA, and IgG antibodies to VZV. Polyclonal antisera specific for heavy chains of human IgM, IgA, and IgG were employed as "capture" antibodies on the solid phase. The antibody class capture assay (ACCA) for VZV IgM antibody detected high titers of virus-specific IgM in all patients with varicella and in 5 of 10 zoster patients. VZV IgM antibody was not detected in patients with primary herpes simplex virus infections or in other individuals without active VZV infection, with one exception, a patient with encephalitis who had other serological findings compatible with a reactivated VZV infection. VZV-specific IgA and IgG antibody titers demonstrable by ACCA were compared with those measured by solid-phase indirect enzyme immunofluorescence assay (EIFA). VZV IgA antibody titers detected in patients with varicella and zoster were variable and could not be considered to be reliable markers of active VZV infection. IgA antibody titers detected by ACCA tended to be higher than those demonstrated by solid-phase indirect EIFA in varicella and zoster patients. VZV IgG antibody titers detected by ACCA in patients with varicella, and to a lesser extent in zoster patients, were as high as or higher than those demonstrated by solid-phase indirect EIFA. However, ACCA was totally insensitive in detecting VZV IgG antibody in individuals with past infections with VZV and would not be a suitable approach for determination of immunity status to VZV.

Monoclonal antibodies for study of antigenic variation in coxsackievirus type B4: association of antigenic determinants with myocarditic properties of the virus

Monoclonal antibodies were produced to a field strain ( Mil ) of group B coxsackievirus type 4 (CBV-4), and to the prototype JVB strain. Nine were neutralizing antibodies and four were non-neutralizing antibodies with virus-specific activity in indirect immunofluorescence (IF) staining. On the basis of reactivity with the panel of monoclonal antibodies, nine different strains of CBV-4 were found to fall into five distinct antigenic groups. Antigenic variants were produced by using the neutralizing monoclonal antibodies to select variants from the Mil virus stock which were no longer susceptible to the selecting antibody. A high frequency of antigenic variation was seen. By using the variants in cross-neutralization and IF tests with the monoclonal antibodies, it was possible to identify five tentative antigenic sites functional in neutralization; one site appeared to be complex and possibly to consist of overlapping epitopes. Reactivity of the monoclonal antibodies was similar, but not necessarily identical, by neutralization and by IF staining. The antigenic variants were found to differ from the parent Mil strain, and from one another, in their myocarditic and cardiotropic properties in a murine model. Two of the variants produced more extensive cardiac pathology, and two produced higher virus titres in the heart than was produced by the parent strain. One variant was notable for extensive production of necrotic lesions in the myocardium. Four of the variants showed less histopathology and three produced less virus in the heart than was produced by the parent strain.

Persistent infection of mouse fibroblasts with Coxsackievirus

Infection of fibroblast cell lines initiated from BALB/c or NFR mice with coxsackievirus B3 (CBV-3) or B4 (CBV-4) resulted in infections which persisted for a limited number of subpassages of the infected cells in most cases, but for over a year in one case. In all instances primary acute infections were characterized by cytopathology and release of infectious virus progeny. Viral antigen could be detected during the acute phase of infection, but not in subcultured infected cells. Infectious center assays showed that every cell was infected during the acute phase of infection, but that from the first subcultivation on, the numbers of cells which were able to initiate infection were greatly reduced. The long term persistent CBV-3 infection was characterized by wide fluctuations in titers of virus released into the supernatant fluids. Interferon did not appear to play a role in maintenance of the persistent infection. Information derived from studies on mechanisms of CBV persistence in the in vitro model may help to elucidate the role of CBV in chronic human diseases such as myocarditis.

Class-specific antibody responses to early and late antigens of varicella and herpes simplex viruses

Antibody responses to early antigens of varicella-zoster virus (VZV), simian varicella virus, and herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) were studied in primary, secondary, and latent infections. IgG antibody responses to the early antigens occurred in primary and secondary VZV and HSV infections, and antibodies to early antigens were also demonstrable in healthy individuals with latent VZV and HSV infections, indicating that the presence of antibodies to early antigens cannot be taken as evidence of active infection with the viruses. Patients with current VZV or HSV infections showed heterotypic IgG antibody responses to early antigens of VZV and HSV to the same extent as to late antigens. In all groups of patients, IgG antibody titers to early antigens were similar to those against the corresponding late antigens, and no difference was seen in the reactivity of early antigens produced with four different blocking agents (cytosine arabinoside, bromodeoxyuridine, trisodium phosphonoformate, and cycloheximide). Antibodies of the IgM and IgA classes reacted with both early and late antigens of HSV, but only with late antigens of VZV and simian varicella virus, suggesting that these antibodies may be directed against late proteins that are expressed to a greater extent in HSV-infected cells treated with blocking agents than they are expressed in treated VZV-infected cells. Homologous IgM antibody responses occurred in both primary and secondary VZV infections, but only in primary HSV infections. Heterotypic IgM responses to HSV-2 antigen were noted in a few VZV patients who did not have demonstrable IgG antibody to HSV, suggesting that even in patients without prior experience with HSV, a VZV infection may stimulate the production of IgM antibodies that react with antigens that are shared by VZV and HSV-2. IgA antibodies to late antigens of VZV and HSV were demonstrable in latent, as well as active, infections with these viruses.

Serological investigation of an outbreak of simian varicella in Erythrocebus patas monkeys

An epizootic of simian varicella occurring in a colony of Erythrocebus patas monkeys was studied serologically by using radioimmunoassay and neutralization tests against (i) a virus strain isolated from an animal that died during the epizootic, (ii) a simian varicella virus strain from an earlier outbreak of simian varicella-like disease at another facility, and (iii) human varicella-zoster virus. Serological tests detected more cases of infection among the animals exposed to virus during the epizootic than were evidenced by clinical findings; only 6 of the 26 animals with seroconversion developed a rash. Good correlation was seen between antibody responses demonstrated by radioimmunoassay and by the neutralization tests. Specificity of the radioimmunoassay was evidenced by the complete agreement with neutralization results for 17 animals which failed to show an antibody response over the course of the outbreak and were assumed not to have been infected. Thus radioimmunoassay is a reliable, rapid, and relatively economical method which could be used for serological screening of primates entering experimental colonies to identify those which might be potential sources of outbreaks through activation of latent simian varicella virus infection. Close correlation was seen between antibody responses to the virus strain from the current outbreak and the one from another epizootic, indicating that the two outbreaks were caused by antigenically similar viruses. Animals showing neutralizing antibody responses to the simian varicella viruses also showed responses to human varicella-zoster virus, which further substantiates the close antigenic relationship between human and simian varicella viruses.

Rapid viral diagnosis

There has been much interest and activity in the development of techniques for rapid viral diagnosis which would allow successful intervention in the treatment of patients or their contacts or in the control of viral diseases in the community. The greatest emphasis has been on techniques that permit viral detection directly in the clinical specimen, since these avoid the need to cultivate the agent, are feasible for detection of viruses that cannot be cultivated, and can detect virus in specimens in which the agent is no longer infectious. Direct methods used for viral detection include electron microscopy and various immunoassays which are based on demonstrating reactivity of viral antigen in the specimen with known viral antisera. The use of immunoassays for more rapid identification of viruses isolated in laboratory host systems and for selective detection of viral antigen in inoculated cell cultures even before the agents produce an observable effect has been an important advance in viral diagnosis by the approach of isolation and identification. The reliability of all specific viral identification procedures depends on the use of high quality viral antisera. Some of the problems previously encountered in preparing satisfactory viral immune reagents are being overcome through the availability of highly specific monoclonal antibodies produced by cell hybridization techniques. Virus-specific IgM antibody assays for rapid diagnosis have been improved greatly through the use of a "capture" technique in which antibody to the human mu chain is used in the solid phase to separate IgM from other serum components which might compete with IgM antibody or give nonspecific reactivity, and also through the availability of highly specific monoclonal antibodies to the human mu chain. A variety of simple assays for determination of viral antibody status have been developed, and many are commercially available. The reliability of some of these antibody assays has been improved through the incorporation of more suitable controls and through better definition of interpretations which should be made from test results.

Association of herpes simplex virus with platelets of experimentally infected mice

In mice infected with herpes simplex virus (HSV) type 1 by the intracerebral route or with HSV type 2 by the vaginal route, virus was shown to be present in greater quantities in purified platelets than in leucocytes or other blood components. Results of the studies described suggest that platelets may play a major role in the hematogenous dissemination of HSV infection.

Use of monoclonal antibodies to human immunoglobulin M in "capture" assays for measles and rubella immunoglobulin M

Monoclonal antibodies to human immunoglobulin M (IgM) were used in a four-phase enzyme immunofluorescence "capture" assay for determination of IgM antibodies to measles and rubella viruses. Little or no background reactivity was seen in the test system, and interfering effects of rheumatoid factor were avoided by preabsorption of test sera with aggregated human IgG. Virus-specific IgM antibody was demonstrable in 23 of 24 patients with serological evidence of measles virus infections and in 36 of 36 patients with serological evidence of postnatal rubella infection. A few of the rubella patients did not show IgM antibody until 5 days after onset of illness. The enzyme immunofluorescence assay was able to demonstrate rubella IgM antibody in congenitally infected newborns, whereas indirect immunofluorescence results for virus-specific IgM were negative. Viral IgM antibody was not detected in persons with past infections with the test viruses, in young children without evidence of past infection, or in patients infected with heterotypic viruses, rickettsiae, chlamydiae, or mycoplasmas.

Comparison of direct immunofluorescence and direct immunoperoxidase procedures for detection of herpes simplex virus antigen in lesion specimens

Direct immunofluorescence and direct immunoperoxidase staining were equally sensitive and specific for detection of herpes simplex virus antigen in lesion specimens, and each method showed 82% agreement with virus isolation results.

Broadly reactive immunofluorescence test for measurement of immunoglobulin M and G antibodies to Ureaplasma urealyticum in infant and adult sera

The indirect immunofluorescence test was used to measure immunoglobulin M (IgM) and IgG antibodies to acetone-fixed Ureaplasma urealyticum organisms in sera from 128 adults with genital infections and from 713 symptomatic newborns and babies 1 day to 18 months old. Thirty-four percent of the adults had demonstrable IgG antibody to ureaplasma. IgM antibody was detected in 2 of the adult sera and in 17 of the infant sera. These babies were divided into two distinct groups. Ten of the infants presented at birth with various physical findings, whereas the onset of symptoms for the other 7 occurred 3 to 13 weeks after birth, and the major clinical finding in 6 of the 7 was respiratory distress. The results of this study suggested that U. urealyticum infection may be associated with fetal damage and infant pneumonia, and if this is substantiated, the indirect immunofluorescence test employing acetone-fixed antigen to measure IgM antibody to U. urealyticum may be an important diagnostic tool.

Effect of the pesticide carbaryl on replication of human and simian varicella viruses

Pretreatment of host cells with carbaryl delayed the early spread of simian and human varicella virus infections. Toward the end of the growth cycle there was an apparent enhancement of infection, since treated cultures showed more infectious centers than did untreated ones in which infectivity had reached maximum levels and then declined.

Production of monoclonal antibodies to human IgM for assay of viral IgM antibodies

Monoclonal antibodies to human IgM were produced by fusing the Sp 2/0-Ag 14 line of mouse myeloma cells with spleen cells from BALB/c mice immunized with purified human IgM. From 6 clones which secreted antibody to human IgM, the one which produced the highest levels of antibody and grew relatively rapidly was selected for expansion and production of immune reagents for viral IgM antibody assays. Mouse ascitic fluids produced with this clone of cells had antibody titers for human IgM of 1 X 10(-10) by indirect enzyme immunofluorescence assay (EIFA). The monoclonal antibodies were found to belong to subclass 1 of murine IgG, and their specificity was shown to be directed against the Fab portion of the mu chain of human IgM. Antibodies from murine ascitic fluid conjugated with horseradish peroxidase were shown to be suitable for assay of measles IgM antibody by indirect immunoperoxidase staining. Antibodies conjugated with alkaline phosphatase could be used in an indirect EIFA for determination of measles IgM antibodies; use of monoclonal conjugates in this system eliminated the nonspecific activity observed in tests utilizing polyclonal anti-mu reagents. Further, the monoclonal antibodies were highly satisfactory for use in a 'capture' system for viral IgM antibody assays. The availability of monoclonal antibodies to human IgM overcomes problems with specificity, consistency and supply which have previously hindered development and standardization of viral IgM antibody assays.

Improved yields and assay of simian varicella virus, and a comparison of certain biological properties of simian and human varicella viruses

Studies were performed to define conditions under which propagation, assay and stabilization of the Delta herpesvirus (DHV) strain of simian varicella virus might be improved, and to compare biological properties of DHV with those of human varicella zoster virus (VZV). A mycoplasma contaminant was successfully eliminated from the DHV seed virus by treatment with a specific anti-serum. DHV was found to replicate more efficiently in the BS-C-1 line of African green monkey kidney cells than in Vero cells, and seed virus preparations in the form of virus-infected cells were produced which had infectivity titers greater than or equal to 1 X 10(6) p.f.u./ml. Greater yields of virus were produced in cultures infected as dispersed cells than as preformed monolayers. Infectious DHV could be released from host cells by sonic treatment of heavily infected cultures at 48 h post infection. Certain agents reported to enhance replication of herpes viruses (caffeine, carbaryl, the tumor promoter 12-0-tetra-decanoyl-phorbol-13-acetate, and DEAE-dextran) had no enhancing effect on replication of DHV. However, DEAE-dextran in the maintenance medium enhanced spontaneous release of DHV into culture fluids. Plaquing efficiency and plaque size of DHV were greater in BS-C-1 than in Vero cells, and plaque assays and plaque reduction neutralization tests were developed in this cell system using a solid overlay medium with neutral red vital stain. Neutralization of DHV was markedly enhanced by fresh guinea pig complement. The newly developed neutralization test demonstrated more vigorous antibody responses to DHV in active and latent VZV infections than were demonstrated with previous procedures. In addition to their preferential growth in monkey and human cells respectively, DHV and VZV were found to differ markedly in their rates of attachment to host cells, with DHV requiring over 6 h of adsorption, while VZV adsorption was essentially complete at 1 h. Also, cell-free DHV was much more resistant than cell-free VZV to repeated cycles of freezing and thawing.

Monoclonal antibodies for rapid, strain-specific identification of influenza virus isolates

Monoclonal antibodies conjugated with fluorescein permitted rapid, strain-specific identification of influenza A isolates and type-specific identification of influenza B isolates by direct immunofluorescence staining. Identification of H1 influenza A strains could be accomplished by direct immunofluorescence on cell culture fluids lacking sufficient hemagglutinin activity to permit identification by hemagglutination inhibition.

Serological reactivity of some monoclonal antibodies to varicella-zoster virus

Monoclonal antibodies to varicella-zoster virus, free from host cell reactivity, were produced by cell fusion technics. Antibodies from four different clones showed diverse activities in neutralization immunofluorescence and complement fixation assays. The antibodies provide useful reagents for viral diagnosis and viral antigenic characterization.

Alpha interferon administration to infants with congenital rubella

Three infants with congenital rubella syndrome were given human leukocyte (alpha) interferon at doses of 2 x 10(5) to 7 X 10(5) U/kg per day for 10 days. A transient decrease in pharyngeal virus excretion was observed with treatment. No significant side effects were associated with the administration of human leukocyte interferon to these infants.

Further evidence for common antigens in herpes simplex and varicella-zoster viruses

To elucidate the mechanism of heterologous antibody responses to herpes simplex virus (HSV) and varicella-zoster virus (VZV) which occur in some patients with HSV or VZV infections, stronger evidence was sought for the existence of cross-reacting antibodies to these viruses, using antibody absorption procedures. Absorption of sera from initial HSV infections with HSV antigen was found to abolish heterologous antibody titer rises to VZV, as demonstrated in complement fixation, neutralization, and anti-complement immunofluorescence test systems. In most instances, convalescent-phase titers to heterologous VZV were reduced by HSV absorption to levels comparable to those in the acute-phase serum, indicating that cross-reacting antibodies were, in fact, responsible for the heterologous antibody titer rises. Absorption of convalescent-phase sera from HSV or VZV patients with homologous antigen also abolished or greatly diminished immunoprecipitating activity with the heterologous antigen, furnishing additional evidence of the existence of cross-reacting antibodies. Absorption of sera with insolubilized IgG to re-remove rheumatoid factor, which was present in a number of the sera studied, had no effect on either homologous or heterologous antibody titer increases. The demonstration of cross-reacting antibodies to HSV and VZV supports the concept that these two human herpesviruses share common antigen(s).

Comparison of anticomplement immunofluorescence and fluorescent antibody-to-membrane antigen tests for determination of immunity status to varicella-zoster virus and for serodifferentiation of varicella-zoster and herpes simplex virus infections

The anticomplement immunofluorescence (ACIF) test was compared with the fluorescent antibody-to-membrane antigen (FAMA) test for determining varicella-zoster virus antibody levels as a measure of varicella-zoster virus immunity status. The ACIF test was found to be comparable to the FAMA test in sensitivity and could be used for examining sera at low dilutions of 1:2 and 1:4. In addition, the ACIF method proved to be a more economical procedure in terms of antigen required and personnel time necessary to perform the test. Heterologous varicella-zoster virus antibody titer rises were demonstrated by the FAMA test with 10 serum pairs from patients with clinically diagnosed genital herpes simplex virus infection, indicating that the FAMA test is no more suitable than other serological methods for serodifferentiation of those herpes simplex virus and varicella-zoster virus infections in which antibody increases occur to both antigens.

Application of immunoperoxidase staining to more rapid detection and identification of rubella virus isolates

Efforts were made to shorten the time required for detection of rubella virus in clinical materials through the use of immunoperoxidase (IP) staining. Comparative studies were performed in which specimens were inoculated in parallel into BHK-21 hamster kidney cells, which were examined by IP staining at 5 days, and into BK-13 and BS-C-1 cells, which were examined in two ways, viz., by subpassage at 7 days into BHK-21 cells and IP staining 3 days later and by subpassage at 7 days into BS-C-1 cells followed by interference testing and immunofluorescence (IF) staining on positive materials (standard method). Direct inoculation into BHK-21 cells with IP staining at 5 days permitted detection and identification of 59% of the 63 positive specimens. Toxicity of some specimens preserved with sorbitol and of certain tissue specimens reduced the number of satisfactory examinations which could be performed in this system. Virus detection and identification by IP staining on subpassaged RK-13 and BS-C-1 materials, requiring a total of 18 days, was comparable to the longer interference-IF method, requiring 17 days. Results obtained by IP staining and interference-IF showed 98% correlation on RK-13 materials and 97% correlation on BS-C-1 materials. IP staining on inoculated BHK-21 cells can be a useful method for rapid identification of a relatively high proportion of rubella-positive specimens, particularly if sorbitol-preserved specimens are avoided, and IP staining on subpassaged RK-13 and BS-C-1 materials is a highly satisfactory alternative to the longer interference-IF method.

Clostridium difficile toxin as a confounding factor in enterovirus isolation

A peculiar cytotoxic effect, occasionally encountered in the course of inoculating cell cultures with fecal specimens for routine enterovirus isolation attempts, was shown to be produced by Clostridium difficile toxin.

Direct immunofluorescence staining for detection of herpes simplex and varicella-zoster virus antigens in vesicular lesions and certain tissue specimens

Direct immunofluorescence (IF) staining was compared with virus isolation for detection of herpes simplex viruses (HSV) and varicella-zoster virus (VZV) directly in clinical materials. These included 199 vesicular lesion specimens and 280 tissue specimens. Correspondence between IF and isolation results was 88% in testing for HSV in lesion specimens and 98% in testing for HSV in various tissue (mostly brain) specimens. Overall, IF was positive for 82% of the specimens in which HSV was demonstrated, and virus was isolated from 89% of the HSV-positive specimens. IF was markedly more sensitive than isolation for demonstrating VZV in lesion and tissue specimens, detecting all of the specimens positive for VZV, whereas isolation detected only 23%. IF detected VZV antigen in a number of lesion specimens taken late after onset, past the time when they would be expected to yield infectious virus. Specificity of positive IF reactions for HSV or VZV in the absence of virus isolation was supported by the facts that (i) staining was obtained with only a single, presumably homologous, immune conjugate, (ii) clinical symptoms were compatible with infection with the virus for which positive IF findings were obtained, and (iii) positive electron microscopy findings for herpesviruses or positive serological results for VZV were also obtained in some instances. Factors to be considered in achieving specificity of IF staining for these human herpesviruses are discussed.

Visual reading of enzyme immunofluorescence assays for human cytomegalovirus antibodies

Enzyme immunofluorescence assays for cytomegalovirus antibodies could be read satisfactorily using a light box with ultraviolet illumination. Higher antibody titers were obtained with a fluorogenic substrate than with a color-producing substrate.

Antigenic comparisons of two new rotaviruses from rhesus monkeys

Two rotavirus strains isolated in cell culture from infant rhesus monkeys with diarrhea were closely related to SA 11 virus and to each other by plaque reduction neutralization tests. However, results of immune electron microscopy suggested possible antigenic differences between the two rhesus rotavirus strains.

Specific identification of human cytomegalovirus isolates by anti-complement immunofluorescence with immune hamster sera

An anti-complement immunofluorescence test utilizing cytomegalovirus immune hamster sera specifically identified cytomegalovirus isolates showing an early, typical cytopathic effect. Inclusion of a control conjugate against adenovirus group antigen permitted correct identification, as adenoviruses, of a few isolates initially suspected of being cytomegalovirus on the basis of cytopathic effect.

Humoral immune response to virions and dense bodies of human cytomegalovirus determined by enzyme immunofluorescence assay

An enzyme immunoassay utilizing a fluorogenic substrate (EIFA) was employed to compare humoral antibody responses to purified virion and dense body antigens in human cytomegalovirus (CMV) infections. Results of these antibody assays were also compared to those obtained by plaque reduction neutralization and complement fixation (CF). In adults with CMV infections diagnosed by a significant rise in CF antibody titer, there was also a vigorous antibody response to the virion and dense body antigens. There was better correlation between antibody levels to the virion and dense body antigens than between antibody levels detected by other combinations of tests. Antibody responses to the virion and dense body antigens were similar, but not identical, suggesting that although the two structures share major antigens, they may also possess unique antigens to which the host can mount independent antibody responses. All individuals with CMV neutralizing antibody also had virion and dense body antibodies, but there was poor correlation between neutralization titers and those detected by EIFA, perhaps reflecting greater strain specificity of the neutralization test. Some individuals with serological diagnoses of Mycoplasma pneumoniae or influenza A infection showed fourfold or greater antibody titer rises to CMV in two or more assays, suggesting reactivation of latent CMV in these infections.

Rotavirus antibody assays on monkey sera: a comparison of enzyme immunoassay with neutralization and complement-fixation tests

An enzyme immunoassay (EIA) for the detection of rotaviral antibodies was developed, using a purified, cell culture-grown SA 11 viral antigen and alkaline phosphatase as an enzyme label. This technique was evaluated by comparative testing with tube neutralization and complement-fixation assays on a collection of simian sera. There was close correlation between positive and negative results obtained by EIA and by neutralization. The EIA was as easy to perform as complement fixation testing, but showed greater sensitivity and fewer nonspecific reactions. Thus, EIA was shown to be a very suitable test for routine detection of rotaviral antibodies in serum. Results of neutralization tests suggested that the monkeys (mostly rhesus macaques) in the present study were infected with viruses varying in their antigenic relatedness to SA 11 virus and to a British isolate of calf rotavirus.

Immunoperoxidase staining for detection of Colorado tick fever virus, and a study of congenital infection in the mouse

Indirect immunoperoxidase (IP) staining was evaluated for sensitivity and specificity in detecting Colorado tick fever (CTF) virus antigen in infected cell cultures and infected mouse tissues, and then was applied to a study of congenital CTF infection in mice. The sensitivity of IP staining was comparable to that of immunofluorescence staining in detecting CTF antigen in infected cell cultures. Endogenous peroxidase activity of mouse tissues caused nonspecific reactivity in the IP system, but this could be abolished by treatment with sodium azide and hydrogen peroxide without destroying CTF antigen. Offspring of mice infected with CTF virus during the 2nd week of pregnancy showed a highly significant increase in the incidence of stillbirths and neonatal deaths as compared with offspring of uninfected controls. CTF antigen or virus was demonstrable in only a low proportion (7%) of embryos, ill newborns or stillborns examined, but a high proportion of mice examined at a time when maternal antibody would be lost (6 and 12 weeks) showed CTF antibody, indicating a higher incidence of infection. IP staining showed potential for use in studies of viral pathogenesis in the mouse model.

Antigen requirements, sensitivity, and specificity of enzyme immunoassays for measles and rubella viral antibodies

Enzyme immunoassay (EIA) systems for measles virus and rubella virus were studied from the standpoints of requirements for suitable viral antigens and control antigens, and the sensitivity and specificity of the tests for detecting antibody elicited by past infection (determination of immunity status), and for serodiagnosis of currenet infections. Crude or semipurified measles virus antigens were satisfactory for EIA, but antigens derived by pelleting virus from infected cell culture fluids were slightly more specific in their reactivity than were antigens produced from lysates of infected cells. However, reliable rubella EIA antigens could be produced only from infected cell culture fluids, and they required density gradient purification to render them suitably specific. Even with gradient-purified rubella antigens, it was necessary to use antigen prepared in an identical fashion from uninfected cell culture fluids as a control on the specificity of reactions obtained with test sera. With appropriate viral antigens and control antigens, both measles and rubella EIA systems were highly sensitive and specific for determination of immunity status and for serodiagnosis of current infections. Antibody was detectable earlier in the course of infection by EIA than by hemagglutination inhibition or complement fixation, but this did not limit the diagnostic value of the test, since titer increases demonstrable by EIA were usually greater than those detectable by hemagglutination inhibition or complement fixation tests.

Possible pitfalls in the study of IgG receptors produced by herpesvirus-infected cells. Brief report

The presence of specific antibodies to human herpesviruses in certain purified human IgG preparations from commercial sources may produce misleading results when such preparations are used in studied on the IgG receptors produced by virus-infected cells.

Varicella-zoster virus immunizes patas monkeys against simian varicella-like disease

To define further the antigenic relationship between human varicella-zoster virus and herpesviruses which produce varicella-like disease in certain simian species, patas monkeys were inoculated with varicella-zoster virus and then challenged with Delta herpesvirus, which uniformly produces severe, clinically apparent disease in susceptible animals. Protection against Delta herpesvirus was conferred both by hyperimmunization with varicella-zoster virus and by a single immunization with a cell-free preparation of varicella-zoster virus. Although the immunological relationship between the human and simian varicella viruses is not completely reciprocal, these studies confirmed that antigens which induce immunity are shared by the human and simian viruses. No clinical symptoms were seen in monkeys inoculated with varicella-zoster virus, but the rapid and marked antibody responses to the virus suggested that subclinical infection had occurred. In contrast, a chimpanzee inoculated with one of the same varicella-zoster virus preparations produced only low levels of antibody.

Identification of Bulgarian strain 258 of enterovirus 71

In 1975 in Bulgaria a severe epidemic of central nervous system (CNS) disease occurred. Clinically, histopathologically, and epidemiologically the cases resembled poliomyelitis, aseptic meningitis, meningoencephalitis, and, in some cases, encephalomyocarditis. About 21% of the 700 reported cases developed paralysis, 44 with fatal outcome [ref. 1]. In 65 cases, 92 strains of enterovirus of the same serologic type were isolated: 38 strains from the CNS, 10 from mesenteric lymph nodes and tonsils, and 44 from feces [ref. 1,2]. A typical representative strain, No. 258, isolated from the spinal cord of a 3-month-old baby who died on the 5th day of disease with signs of focal polioencephalitis, was selected for intensive study. Cross-neutralization tests established the antigenic identity of the Bulgarian 258 strain (Stanchev) with American strains of enterovirus type 71 (BrCr and JaFr strains) and Swedish strains of the same type (Nos. 52343, 52500, and 6041). From its biological [ref. 1,2], physicochemical [ref. 3], and antigenic properties, the etiological agent of this large epidemic can be classified as a member of enterovirus type 71, one of the most highly pathogenic of the recently recognized enteroviruses.

Antibody assays for varicella-zoster virus: comparison of enzyme immunoassay with neutralization, immune adherence hemagglutination, and complement fixation

An enzyme immunossay (EIA) was adapted for detection of antibody to varicella-zoster virus, and its sensitivity and specificity were compared with those of neutralization, immune adherence hemagglutination (IAHA), and complement fixation tests. Test sera showed little nonspecific reactivity in the EIA system, and valid results could usually be obtained at serum dilutions as low as 1:8. Demonstration of the presence or absence of varicella-zoster viral antibody by EIA showed 94% correlation with results obtained in neutralization tests, but EIA titers were 2- to 16-fold higher than neutralizing antibody titers. Results by IAHA showed 87% correlation with those obtained by neutralization. No false positive IAHA results were seen, but a number of false negative IAHA results were seen at the 1:8 serum dilution, particularly in older individuals. With increasing age (>40 years), and presumably increased time from varicella infection, neutralizing antibody levels generally declined to 1:8 or 1:16, EIA levels fell to 1:128 or 1:256, and IAHA and complement fixation antibody titers were usually <1:8 or 1:8. EIA and IAHA were as reliable as the neutralization and complement fixation tests for serodiagnosis of varicella and zoster infections. All tests demonstrated heterotypic varicella-zoster antibody titer rises in selected patients with initial herpes simplex virus infections, but fewer heterotypic responses were seen by EIA than by the other methods. EIA offers a rapid, sensitive, and specific method for varicella-zoster antibody assay that is applicable to use in a clinical setting.

Comparative sensitivity of various cell culture systems for isolation of viruses from wastewater and fecal samples

In efforts to define the most sensitive cell culture systems for recovery of viruses from wastewaters, 181 samples were inoculated in parallel into tube cultures of various cell types and were plaqued in bottle and petri dish cultures of three types of monkey kidney cells. Polioviruses were recovered most frequently in the RD line of human rhabdomyosarcoma cells, group A coxsackieviruses in RD and human fetal diploid kidney (HFDK) cells, group B coxsackieviruses in the BGM line of African green monkey kidney cells, echoviruses in RD and primary rhesus monkey kidney (RhMK) cells, and reoviruses in RhMK cells. BGM cells were unsatisfactory for recovery of viruses other than polioviruses and group B coxsackieviruses, and a line of fetal rhesus monkey kidney (MFK) was not a satisfactory substitute for primary RhMK. With RhMK cells, comparable numbers of virus isolations were made in tube cultures and in plaque assays conducted in bottle cultures, but with BGM and MFK cells, fewer isolations were made by plaquing than by inoculation of tube cultures. In comparative plaque assays on fecal samples under three different overlays in bottle and plate cultures of RhMK, BGM, and MFK cells, it was found that plaquing in the most sensitive system, RhMK, was less efficient for virus recovery than was inoculation of tube cultures of RhMK or HFDK cells. Overall, plaque assays performed in petri dishes in a CO(2) incubator yielded fewer virus isolates than did parallel plaque assays performed in closed bottle cultures. Other limitations of plaque assays for recovery of human enteric viruses are discussed.

Comparison of immunofluorescence and immunoperoxidase staining for identification of rubella virus isolates

To explore possible advantages which immunoperoxidase (IP) staining might have over immunofluorescence (IF) staining for identifying rubella virus isolates, direct comparative studies were done on the same coded clinical materials using the same rubella immune rabbit serum as the primary antiserum in both systems. The rubella immune rabbit serum and conjugated anti-rabbit immune globulins could be used more dilute in the IP system than in the IF system. Both IP and IF staining detected rubella antigen in all specimens which were positive by interference. IP staining also detected low levels of rubella antigen in a few additional specimens which had originally been positive for rubella virus, but which on retesting were negative by interference and IF staining. With second-cell-culture-passage material, IP and IF staining showed comparable specificity, and the few specimens which reacted nonspecifically generally did so in both systems. Cell cultures inoculated directly with urine specimens showed greater nonspecificity by IP than by IF, but this activity could be abolished by pretreatment with sodium azide and peroxide; other methods tried for inactivating endogenous peroxidase activity destroyed rubella antigen as well. The intensity of staining for positive specimens was comparable in the two systems. However, more antigen was demonstrable in both systems when BHK-21 cells were inoculated as a cell suspension and then permitted to grow into monolayers than when the same specimens were inoculated into preformed monolayers. IP staining was considered to be a highly satisfactory alternative to IF staining for identification of rubella virus isolates.

Anti-complement immunofluorescence test for antibodies to human cytomegalovirus

An anti-complement immunofluorescence (ACIF) test that detects human cytomegalovirus (CMV) antigen in the nuclei of infected cells was used for assay of CMV antibodies in human sera. Various factors influencing the sensitivity and specificity of the ACIF test system were investigated, and results were applied to the development of a procedure which could be completed in a relatively short length of time and gave reproducible results. Results obtained in the ACIF test were compared with those obtained in complement fixation, indirect hemagglutination, and neutralization tests, and the ACIF test was shown to be suitable for detection of significant antibody titer rises and stationary levels of CMV antibody. Heterotypic antibody responses were not seen with sera from other human herpesvirus infections. The nonspecific cytoplasmic staining that occurs in indirect immunofluorescence tests for CMV did not occur in the ACIF system, and sera that were anti-complementary in complement fixation tests could be examined satisfactorily by ACIF. Thus, the test is a valuable supplemental or back-up procedure for the serodiagnosis of CMV infection.