Humoral immune response to human cytomegalovirus DNA polymerase

In this work, we show that antibodies to baculovirus recombinant DNA polymerase of human cytomegalovirus are present in human sera during natural infection. Specific antibody was found to be of the immunoglobulin G class, produced at low titers only for a short period of time at the beginning of acute infection and not detectable in sera from patients with a convalescent or a latent phase of infection. These results were compared with those obtained with procaryotically expressed p52, the polymerase accessory protein.

Comparison of immunological reactivity to two major antigens of homologous and AD169 human cytomegalovirus strains during primary infection in renal transplant patients

The IgG and IgM immunoblotting patterns for the major HCMV antigens p65 and p55/52 were studied in 5 renal transplant recipients during primary HCMV infections. Sequential sera from the 5 patients were tested in parallel with standardized antigens derived from the reference strain AD169 and from the patient'own isolates. The immunoblotting patterns differed from patient to patient as well as between strain AD169 and the patient's homologous isolates. The differences consisted in a better response to the antigens derived from the reference strain AD169, suggesting a delay of the IgM/IgG switch and of the affinity maturation of IgG antibodies to the homologous p65 and p55/52 antigens. The results suggest caution in the interpretation of immunoblotting data derived from laboratory strains such as AD169.

Large-scale testing of human serum to determine cytomegalovirus neutralising antibody

Complement (C')-dependent neutralising cytomegalovirus (CMV) antibody titres were determined in 4150 serum samples obtained from infants and children, as well as women of childbearing age. In a smaller group of samples, C'-independent neutralising antibody titres were also measured together with their reactivity to each individual CMV structural polypeptide in addition to total CMV antibody concentration. Results showed that primary CMV infection takes place mainly in early infancy and that 30-40% women of childbearing age do not have any or have very low titres of CMV neutralising antibody. Since poor correlation was found between the results of neutralisation tests and those of enzyme immunoassay, routine testing of neutralising antibody is warranted in those subjects, such as pregnant women, at risk of CMV infection. Results of immunoblotting suggest a correlation between high titres of neutralising antibody and antibody reactivity with three proteins of MW 86, 65, 60 kDa.

Human cytomegalovirus nuclear and cytoplasmic dense bodies

One of the characteristic features of cytomegalovirus (CMV) replication is the formation of cytoplasmic dense bodies. Recent findings revealed similar structures also in the nuclei of CMV-infected cells. By transmission electron microscopy, immuno electronmicroscopy, and cytochemistry, we have studied the morphogenetic steps and macromolecular composition of both structures. Our results show that both structures contain DNA, RNA and viral antigenic proteins. Nuclear dense bodies are probably an expression of a stimulated cellular metabolism, while cytoplasmic dense bodies may represent the site where surplus cellular and viral molecules are stored before being eliminated.

Lack of correlation between virus detection and serologic tests for diagnosis of active cytomegalovirus infection in patients with AIDS

The aim of this study was to evaluate the usefulness of serologic analysis for the diagnosis of active cytomegalovirus infection in patients with AIDS. Active cytomegalovirus infection was diagnosed by virus isolation from urine and saliva and detection of antigenemia. Serologic analysis was done by several conventional and innovative procedures. The results indicate no correlation between any of the most popular serologic procedures and virus detection by culture in urine or saliva or antigenemia.

Comparison of four techniques for detection of antibodies to cytomegalovirus

Four serological methods were compared and evaluated for use in detecting cytomegalovirus antibody in blood and organ donors. Western blotting (immunoblotting), latex agglutination, enzyme-linked immunosorbent assay, and a recent available microparticle enzyme immunosorbent assay were used. The microparticle enzyme immunoassay appears to compare favorably with each of the other three assays tested for screening blood and organ donors for a previous cytomegalovirus infection.

Antibody response to cytomegalovirus (CMV) polypeptides in liver transplant recipients with CMV hepatitis

Immunoblotting (IB) was used to detect the presence of serum antibody against each individual CMV structural polypeptide and the major nonstructural antigen during CMV hepatitis in 12 orthotopic liver transplant recipients to evaluate the diagnostic utility of this technique. The basic phosphoprotein p150 primarily, and to a much lesser extent p65 (lower matrix protein) and p52 (nonstructural DNA-binding protein) were the most recognized antigens by both IgG and IgM class antibodies. Collectively, IgM antibodies were detected to p150 in 9 of 12 (75%) patients and were detected before (2 cases), at the same time (1 case), or after (6 cases) detection of virus in cell cultures. IB was equal to indirect immunofluorescence (IIF) and enzyme immune assay (EIA) for the detection of IgG and superior to EIA for IgM class antibodies to CMV in OLT patients. Our results indicate that the p150 phosphoroprotein is an essential component of serologic assays, especially for the detection of IgM antibodies to CMV.

Enzyme-linked immunoadsorbent assay for the detection of cytomegalovirus-IgM: comparison between eight commercial kits, immunofluorescence, and immunoblotting

Eight commercially available enzyme-linked immunoadsorbent assays (ELISA) for the detection of cytomegalovirus (CMV)-specific IgM were used in parallel to determine the presence of CMV-IgM in 123 serum samples from pregnant women. The results obtained with the eight kits were compared. Based on concordance of six or more of the eight kits, we assessed sensitivity, specificity, and overall agreement, as well as incidence of false-positive and -negative results for each kit. The results obtained by ELISA were then compared with those obtained by immunofluorescence (IF) and immunoblotting (IB). Our study did not single out one outstanding ELISA kit among the eight evaluated, nor did it suggest that IF or IB are better than ELISA. Furthermore our results indicate that IB might be useful in several cases as, beside its good sensitivity, most IB-false-positive sera are easily recognized as reacting exclusively with pp150, the unique reactivity to pp150 not being among the IB profiles of IB-true-positive sera. Nevertheless 14.6% of sera remained CMV-IgM-indeterminate.

Evidence that human cytomegalovirus assembly protein shares antigenic sites with an uninfected cell membrane protein

Immunological abnormalities of an autoimmune nature often develop during acute primary human cytomegalovirus (HCMV) infection. IgM antibodies reacting with the membrane of uninfected human embryonic fibroblasts can be detected in most patients undergoing a primary HCMV infection. In this work, we have found that there is a common antigenic epitope shared by a cell membrane component of Mr 60K (mp60), which is recognized by IgM in sera from patients with primary HCMV infection, and a linear determinant in the C-terminal half of the HCMV assembly protein of Mr 38K (vp38), which is known to be one of the most IgM-reactive antigens of HCMV. While vp38 seems to contain other specific IgM-reactive regions, IgM reactivity to mp60 is due exclusively to this shared epitope. Furthermore, mp60 is found abundantly on the surface of human red blood cells, a possible explanation for the pathogenesis of the haemolytic anaemia that may appear during primary HCMV infection.

Human cytomegalovirus structural proteins: immune reaction against pp150 synthetic peptides

In the present study, several peptides of the major structural antigen (pp150) of human cytomegalovirus (CMV) have been chemically synthesized and tested by a modified slot blotting procedure for their ability to bind CMV-specific immunoglobulin G (IgG) and IgM present in human sera. The sequences of the peptides were deduced on the basis of either (i) their presence in a fusion protein already known to be frequently recognized by human antibody or (ii) their high content of hydrophilic amino acids as deduced from the published nucleotide sequence. An important IgM-binding epitope was found to be located in the last 38 amino acids at the carboxy terminus of the molecule. This region reacts with anti-CMV IgM present in the great majority (83.3%) of IgM-positive human sera, and adsorption experiments have shown that IgM titers to the entire pp150 decrease 25 to 50% in most sera previously absorbed with this region. The overall results obtained endorse the continued synthesis of other sequences in order to define a group of peptides sensitive and specific enough to replace the virus and infected cells as an antigenic substrate in the serological evaluation of anti-CMV antibody.

Antigenic variation of cytomegalovirus isolates recovered from infected children

The present work investigated antigenic variations of the most immunogenic polypeptides of Cytomegalovirus (CMV), namely two nonstructural polypeptides of MW 72 Kd and 52 Kd, and 5 structural proteins of MW 150, 65, 58, 38 and 28 Kd, in several low-passage CMV isolates from urine of infected children. The polypeptides showing the greatest variations were the non structural p72 and p52, and the structural proteins p65 and p38. Furthermore the reactivity of the children's sera was studied with regard to the antigenic proteins of the homologous virus strain. We failed to recognize any reactivity pattern typical of an acute CMV infection and the results obtained indicate that CMV-infected children may have a very low and variable IgG and IgM response, p150 and p65 being the two most often recognized antigens.

Human cytomegalovirus structural components: intracellular and intraviral localization of p38

Rabbit antisera raised against the product of ORF UL 80 of human cytomegalovirus (CMV) genome (HindIII L fragment of AD169 strain) as well as IgM from acutely infected patients recognize an antigen of Mr 38 kDa. In the viral particle this antigen is bound via S-S bridge to a lower Mr compound to form a final complex of 62 kDa that is also recognized by rabbit antisera as well as patients' IgM. P38 is present both in the nucleus and in the cytoplasm of CMV-infected cells starting from 24 h p.i. and increasingly thereafter. Immunoelectron microscopy revealed that this antigen is mainly associated with the internal portion of viral capsids both in the nucleus and in the cytoplasm.

Humoral immune response to human cytomegalovirus proteins: a brief review

Although human cytomegalovirus (HCMV) has a genome of 150 x 10(6) Da, and a protein-coding content of over 200 open reading frames, few viral proteins seem able to elicit a strong antibody response in the natural host during viral infection. The immunodominant polypeptides include a component of 72 kDa among immediate early proteins, a polypeptide of 52 kDa among delayed early proteins and a glycoprotein complex of 58 and 93-130 kDa and two phosphoproteins of mol. wt 150 and 65 kDa among the structural proteins. Following a general overview of the humoral immune response, this brief survey mainly deals with the antibody response to these proteins. As significant epitopes of the major HCMV immunogenic polypeptides have been expressed in procaryotic cells over the last few years, an overview of the state of the art in this particular field will also be given.

Large-scale screening of human sera with cytomegalovirus recombinant antigens

One of the major problems regarding cytomegalovirus (CMV) serodiagnosis is the use of poorly defined viral antigens. Individual CMV proteins expressed via recombinant DNA procedures are a promising approach to solving this problem. In this work, 10 different fusion proteins containing antigenic epitopes of the major CMV structural proteins of 150, 71, 65, 38, and 28 kilodaltons and of the nonstructural protein of 52 kilodaltons were subjected to Western (immuno-) blotting to assay their reactivities with immunoglobulins G and M in 395 CMV-seropositive and 100 CMV-seronegative unselected human serum samples. As a whole, the results obtained indicate that CMV can be replaced by recombinant viral proteins in the serological evaluation of anti-CMV antibodies.

Procaryotic expression of phosphorylated tegument protein pp65 of human cytomegalovirus and application of recombinant peptides for immunoblot analyses

The tegument of human cytomegalovirus (HCMV) contains a phosphorylated protein of 65 kilodaltons, termed pp65, which was reported to carry significant epitopes for the stimulation of the humoral immune response during natural infection. A monoclonal antibody directed against this protein was used to screen a lambda gt11 cDNA library for recombinant polypeptides. Two DNA fragments from purified lambda clones and one fragment from genomic DNA were used for cloning in a bacterial high-level expression vector. The resulting fusion proteins were tested for their reactivity with a panel of monoclonal antibodies directed against pp65 and with polyspecific anti-HCMV rabbit antisera. The binding site for all the monoclonal antibodies tested was found to be contained in one of the recombinant proteins with a viral portion of 26 amino acids. Immunoblot analyses with HCMV-positive human sera revealed that pp65 alone is not a reliable antigen for serodiagnosis but may be very useful in combination with other HCMV proteins.

A simple and rapid procedure for the direct detection of cytomegalovirus in urine samples

We compared cytomegalovirus (CMV) isolation in tissue culture and viral DNA detection by DNA:DNA hybridization in 60 clinical urine samples concentrated by different procedures. Our results showed that urine concentration by filtration is the easiest and quickest procedure allowing further detection of CMV. With optimized working conditions, the CMV detection in urine can be done in 5 hr without requiring cell cultures or costly instruments.

Comparison of immunoblotting with other serological methods and virus isolation for the early detection of primary cytomegalovirus infection in allograft recipients

Sequential specimens from nine allograft recipients were examined by using a variety of methods to detect primary cytomegalovirus (CMV) infection as rapidly as possible posttransplantation. Sera were examined for immunoglobulin G (IgG) and IgM antibodies by immunoblotting, enzyme immunoassay, and immunofluorescence and also by complement fixation, latex agglutination, and an immunofluorescence test for antibody to CMV early antigen. Urine and occasionally blood, tissue, and other specimens were centrifuged onto cell cultures to enhance CMV infectivity. Eight of the nine patients showed laboratory evidence of primary CMV infection, and CMV was isolated from seven of the eight: in no case was virus isolated before seroconversion had become evident. However, serological tests differed in their abilities to detect antibody response to CMV infection in different patients; while immunoblotting, latex agglutination, and enzyme immunoassay for IgG antibodies generally detected seroconversion before complement fixation, this was not invariably the case. At present, optimal laboratory detection of CMV infections in these patients can be achieved only by a combination of serological methods and virus isolation.

Antibody response to recombinant lambda gt11 fusion proteins in cytomegalovirus infection

Significant epitopes of two of the major cytomegalovirus antigens, a nonstructural DNA-binding protein of 52 kilodaltons (kDa) and a structural phosphoprotein of 150 kDa, expressed as fusion proteins with the beta-galactosidase, were induced in Escherichia coli after infection with recombinant lambda gt11 clones. The epitopes were then used in immunoblotting to assay specific immunoglobulin G (IgG) and IgM in several groups of sera from long-term seropositive subjects and from patients undergoing primary or secondary virus infection. The data obtained showed that IgM reacting with the 52-kDa nonstructural antigen are linked to primary virus infection and can therefore be considered a serological marker of this infection.

Antibodies to Campylobacter pylori in patients with idiopathic dyspepsia

We used Western Blotting analysis to determine the immune profile to Campylobacter pylori polypeptides in: A) sera from patients with idiopathic dyspepsia and bacteriological evidence of C. pylori gastric colonization, B) sera from patients with the same symptoms but no bacteriological evidence of C. pylori infection and C) healthy subjects. To avoid interference of aspecific reactions due to antigenic cross reactivity with other thermophilic Campylobacter species, antisera were raised in rabbits against C. pylori as well as against C. coli and C. jejuni. Some bands (with an approximate molecular weight of 118, 85, 40, 34, 28, 18 and 12 Kd) which can be considered specific for C. pylori were identified and the IgG reaction to some of them (40, 34, 28 Kd) was shown to be significantly higher in patients with bacteriological evidence of C. pylori infection than in the other two groups. IgM reactivity to two bacterial proteins of molecular weight 118 and 40 Kd was particularly evident in the second group of patients suggesting a possible diagnostic tool to identify C. pylori infection at a very early stage.

Identification and preliminary use of recombinant lambda gt11 fusion proteins in human cytomegalovirus diagnosis

We have isolated reactive clones from a lambda gt11 expression library of human cytomegalovirus (HCMV) DNA using HCMV-positive human sera. Among the recombinant clones obtained, one carried a fragment encoding a portion of p52, the major non-structural DNA-binding protein of 52K (p52) and another carried a part of the gene coding for pl50, the major structural phosphoprotein. These two fusion proteins were examined by immunoblot analysis to test their ability to bind specific antibodies in human sera. The results showed that high titres of antibody to the DNA-binding protein are present in sera of patients undergoing acute HCMV infection, whereas high titres of antibodies to the structural phosphoprotein are widespread in the healthy HCMV-seropositive population. The use of these fusion proteins as antigens for differential screening of serum as a way of detecting recent HCMV infection is discussed.

A human cytomegalovirus-neutralizing monoclonal antibody recognizes a normal cell protein

A monoclonal antibody (MAb), N2, neutralized human cytomegalovirus (HCMV) infectivity in the absence of complement and recognized a normal cell protein. By immunofluorescence, MAb N2 detected antigens in uninfected human cells, but not in cells of non-human origin. Antigens were present at the membrane and were dispersed diffusely within the cytoplasm. MAb N2 immunoprecipitated a glycoprotein with an Mr of 94K from uninfected and infected cells. In infected cells only, it also recognized a protein of Mr 34K which was not linked to the 94K Mr glycoprotein by disulphide bonds. N2 neutralized both laboratory and field isolates of HCMV. A study of the distribution of the N2 neutralization epitope recognized among fresh isolates of HCMV showed that only 67% of the isolates could be neutralized by this antibody. There was no correlation between the number of in vitro passages and the level of neutralization. The 34K Mr polypeptide was present in cells infected by all isolates. It thus appears that, during virus assembly, HCMV acquires a normal cell protein that bears a neutralization epitope.

Antibody reactivity to cytomegalovirus structural polypeptides in subclinical and clinical human immunodeficiency virus infections

A total of 56 sera from asymptomatic HIV-seropositive subjects and patients with symptomatic HIV infection were studied by immunoblotting for IgM, IgG and IgG subclass reactivity against cytomegalovirus structural polypeptides. The results showed a high percentage of IgM-positive sera in the asymptomatic patients, and IgM reactivity was particularly high against a polypeptide of intermediate molecular weight (p66). IgG reactivity was very high against the majority of viral structural polypeptides with the possible exceptions of p82 and p61, in all patients. Antibody to these polypeptides decreased with the increase in HIV-specific symptoms. No significant difference in the reactivity of IgG subclass to viral polypeptides was found among the different groups of subjects, except for a generalized increase in IgG subclass reactivity from asymptomatic to HIV-specific symptomatic patients.

IgM to human cytomegalovirus: comparison of two enzyme immunoassays and IgM reactivity to viral polypeptides detected by immunoblotting

IgM detection by enzyme-linked immunosorbent assay (ELISA) is the most used method of establishing a cytomegalovirus (CMV) infection during pregnancy. In this paper, we discuss the results obtained assaying 1,000 sera from pregnant women by two ELISA kits: a traditional indirect ELISA and a more recent IgM-capture ELISA. All the sera that gave a positive ELISA value with one or both kits were further tested by immunoblotting (IB) to establish which CMV polypeptides were detected by IgM antibodies. From the results obtained, IgM-capture ELISA seems less sensitive than indirect ELISA, but correlates better with serological evidence of active CMV infections as judged by typical IB profiles.

Diagnostic avail of a biotinylated DNA probe made from the XbaI E fragment of human cytomegalovirus genome

A biotinylated DNA probe has been constructed using the Xba I E fragment of human cytomegalovirus (CMV) genome. This fragment contains a genomic region which is transcribed immediately after infection. The probe proved useful in detecting CMV genome directly in pathological materials and both immediate early viral transcripts and virus genome in infected tissue cultures. The results obtained indicate very good sensitivity and specificity of the probe, suggesting its possible use in routine diagnosis of CMV infection.

Antibodies to human cytomegalovirus structural polypeptides during primary infection

This study aimed at broadening the understanding of the immunogenic potential of cytomegalovirus (CMV) structural polypeptides during natural infection and to ascertain their possible use in serological diagnosis. Immunoblotting was used to analyse the appearance and development of serum IgG and IgM against human CMV structural polypeptides in sequential sera from renal transplant recipients during the first 1-3 months of primary CMV infection. The results showed that the first IgG to appear is specific for a polypeptide of 66 kDa and these antibodies appear either alone or together with others against another polypeptide of 82 kDa. IgG to the 150 kDa protein appears at least one week later. The first IgM to appear reacts preferentially with a 38 and 66 kDa polypeptide. The early detection of antibody against the major viral antigenic proteins in the diagnosis of CMV primary infection is discussed.

Identification and procaryotic expression of the gene coding for the highly immunogenic 28-kilodalton structural phosphoprotein (pp28) of human cytomegalovirus

Human cytomegalovirus contains a structural polypeptide that is 28 kilodaltons in apparent molecular size and is reactive in Western blot (immunoblot) analysis with the majority of human sera. The gene coding for this polypeptide was mapped on the genome of human cytomegalovirus strain AD169. A monoclonal antibody specific for the 28-kilodalton polypeptide was used to screen a cDNA library constructed from poly(A)+ RNA of human cytomegalovirus-infected cells in the procaryotic expression vector lambda gt11. Hybridization of cDNA with cosmid and plasmid clones mapped the gene to the HindIII R fragment. The gene was transcribed into a late 1.3-kilobase RNA. The nucleotide sequence of the coding region was determined. Parts of the 28-kilodalton polypeptide were expressed in Escherichia coli as hybrid proteins fused to beta-galactosidase. In Western blots these proteins were recognized by human sera. Antibodies raised against the hybrid proteins reacted specifically with the viral antigen in immunoprecipitations and Western blots. In vitro phosphorylation of HCMV virions and immunoprecipitation showed that the 28-kilodalton polypeptide was phosphorylated.

Human cytomegalovirus morphogenesis: an ultrastructural study of the late cytoplasmic phases

The late cytoplasmic phases of human Cytomegalovirus (HCMV) morphogenesis in cultured fibroblasts have been studied by transmission electron microscopy focusing attention on the relationship between the viral particles and host cell organelles. The results obtained largely reflect changes in cells subjected to sublethal injurious stimuli induced by many viruses as well as different noxious agents. A great increase in the number of Golgi apparatuses and lysosomes was observed, both of them interacting with the viral progeny. HCMV seems to acquire its final envelope from Golgi-derived structures and, less frequently, from the plasma membrane.

Reactivity of cytomegalovirus structural polypeptides with different subclasses of IgG present in human serum

Human cytomegalovirus (CMV) has at least 15 structural polypeptides which are immunogenic during natural infection. In this report we used immunoblotting to study the reactivity of each polypeptide with the four IgG subclasses present in CMV antibody-positive human serum obtained from both convalescent patients and from patients with serological evidence of active CMV infection. The results showed that in the serum of patients reactivity to several CMV polypeptides is mostly due to all four IgG subclasses, with IgG3 being the most prevalent followed by IgG1. Intermediate molecular weight polypeptides (namely p66, p61, p55, p49, p38) appear to be the major antigens responsible for the preferential induction of the IgG3 response. During convalescence the reactivity of all four IgG subclasses is evident only against a structural polypeptide of 150 kD molecular weight (MW), while intermediate MW polypeptides show variable IgG subclass reactivity. The presence of IgG3 to one or more polypeptides of intermediate MW might be of diagnostic interest.

A 46 KD polypeptide, present in purified human cytomegalovirus, is provided with DNase activity and is antigenically related to a higher molecular weight, enzymatically inactive, cellular protein

DNase activity can be detected in lysates of extensively purified human cytomegalovirus (HCMV) particles. The presence of activity only in purified virions and not in dense bodies and its neutralization by HCMV-positive human sera strongly suggest that the enzyme is virus-specific. In situ analysis of the enzymatic activity of individual HCMV polypeptides, separated in a DNA-containing polyacrylamide gel, has shown that the DNase activity present in purified virions is mainly associated with a polypeptide of 46,000 dalton MW (p46). A monospecific anti-p46 serum, raised in mice, neutralizes about 80% of the DNase activity present in extracts of purified virions and recognizes an enzymatically inactive, 76,000 dalton MW polypeptide both in non-infected and HCMV-infected cells.

Human cytomegalovirus structural components: intracellular and intraviral localization of p28 and p65-69 by immunoelectron microscopy

Using specific monoclonal antibodies, we have localized two structural proteins (p65-69 and p28) of human cytomegalovirus in infected cells and in virions and/or virus-related particles by immunoelectron microscopy using protein A-gold. Protein p65-69 is present in some roundish structures in the nuclei, often in contact with the viroplasm, and in the cytoplasm, exclusively within the dense body matrix. Protein p28 is present only in the outline of cytoplasmic capsids, and reaches the highest density in the large aggregates of virions and dense bodies which are particularly numerous during the late phases of the viral replication cycle.

Antibody response to individual cytomegalovirus structural proteins in different groups of subjects

The antibody response to cytomegalovirus structural polypeptides in sera from three groups of acutely infected subjects was analyzed. Differences in number and types of polypeptides were noted. Immunoblotting could be used to distinguish sera from patients with acute cytomegalovirus hepatitis from convalescent sera by the detection of antibody to viral proteins of 82, 66, 62, and 55 kilodalton molecular weight at a high serum dilution.

Structural components of human cytomegalovirus: in situ localization of the major glycoprotein

The localization of the major cytomegalovirus glycoprotein, both in the viral particle and in the cell membrane, was studied by means of indirect immunofluorescence and immunoelectron microscopy using a guinea pig anti-glycoprotein hyperimmune serum recently obtained by Gonczol et al. [1986]. By indirect immunofluorescence a slight and uneven positivity was observed on the plasma membrane of unfixed cells starting from 72 h postinfection (p.i.) until the end of our observation time (7 days p.i.). At immunoelectron microscopy the plasma membrane proved positive only where the virus and dense bodies budded through the membrane to form their own envelope. Extracellular viral particles (both viruses and dense bodies) appeared very strongly labeled on the external surface.

Relationship between antibody titres against human cytomegalovirus detected by enzyme immunoassay and titres to individual viral polypeptides studied by immunoblotting

Several sera with different IgG and IgM titres measured by enzyme immunoassay were studied in serial dilutions for their reactivity with human Cytomegalovirus structural polypeptides separated in SDS-PAGE and electrotransferred to nitrocellulose. The different immunogenicity of the viral proteins is documented and a hypothetical evolution of the humoral immune response to individual polypeptides is presented.

Serum antibodies to individual cytomegalovirus structural polypeptides in renal transplant recipients during viral infection

In a longitudinal study we examined by immunoblotting (IB) the development and the evolution of the humoral immune response against individual cytomegalovirus (CMV) structural polypeptides in a total of 80 serum samples from 13 renal transplant recipients showing serological evidence of CMV infection and five renal transplant recipients with an anti-CMV antibody level unchanged over the observation period. The results showed that the IB reactivity at the time of transplantation may be a good index of the host's humoral immune status against CMV; by using this procedure it is possible to identify a seroconversion by the detection of antibodies reacting with some intermediate molecular weight proteins in sera examined at high dilution. Furthermore, IB is a very sensitive procedure also for IgM detection as it anticipates the positivity of the enzyme immune assay for IgM.

Changes in membrane permeability in cells infected by human cytomegalovirus

To analyze whether human cytomegalovirus could induce changes in membrane permeability we studied both Hygromycin B (HyB) inhibition of protein synthesis and glycine and choline uptake during viral replication. A higher sensitivity to HyB was observed both immediately after virus adsorption and in concomitance with the release of viral progeny. HyB sensitivity immediately after virus adsorption was not associated with changes in membrane permeability to glycine and choline while 60 hours p.i. a remarkable increase in choline uptake was detected.

Human immune response to cytomegalovirus structural polypeptides studied by immunoblotting

To define better the human immune response to individual structural proteins of human cytomegalovirus (HCMV), 55 human sera with different IgG and IgM titres were studied for their reactivity with HCMV structural polypeptides separated by SDS-PAGE and electrotransferred to nitrocellulose paper. The results obtained showed that antibody titres detected by immunoassay correlate with the intensity and the number of polypeptides reacting by immunoblotting (IB). The IB profiles of HCMV polypeptides reacting with different sera having the same antibody titres show considerable variation. Sera with high levels of IgG antibody and that are IgM-positive frequently react with 155, 149, 82.5, 74.5, 67, 57, 55, 38.5, and 28 kD polypeptides; all these sera react with 155, 67, 57, 55, 38.5 kD polypeptides. Sera with high levels of IgG antibody but that are IgM negative frequently react with all these polypeptides, with the exception of 149 and 74.5. Only 155 and 28 kD polypeptides were recognized by all sera of this group. The sera with moderate levels of IgG antibody preferentially recognize 155, 110, 82.5, 62, 55, 38.5 and 28 kD polypeptides. The sera with low levels of antibody reacted especially with 155 and 62 kD polypeptides. IgM antibody seems to recognize preferentially 155, 110, 67, 57, 55, 38.5 kD polypeptides.

A 28000 molecular weight human cytomegalovirus structural polypeptide studied by means of a specific monoclonal antibody

We have produced a monoclonal antibody against human cytomegalovirus (HCMV) which recognizes a structural protein of 28 000 mol. wt. which is present in both the cytoplasm of infected cells during the late phase of the viral replication cycle and in the extracellular viral particles. This antigen was detected in all HCMV strains assayed and reacted with human sera having anti-HCMV antibodies.

Antibody response against early antigens in Herpesviridae infections

For the serological diagnosis of Herpesvirus infection, increasing use is made of the determination of the antibodies against virus-specific early antigens. The presence of serum antibody to early antigens is a widely accepted marker of acute Epstein-Barr virus infection or Varicella-Zoster virus infection. Controversial data are present in the literature about the significance of Cytomegalovirus early antigens antibody response. This is discussed in view of the possibility that controversial results could be due to different methods used to produce early antigens by different authors.

Increased accumulation of a lipophilic cation (tetraphenylphosphonium) in human embryo fibroblasts after infection with cytomegalovirus

The distribution of a lipophilic cation, tetraphenylphosphonium (TPP+), has been used to monitor changes in mitochondrial and plasma membrane potentials within human embryo fibroblasts infected with human cytomegalovirus. An increase in TPP+ accumulation was observed throughout the whole viral replication cycle, beginning 6 h after infection. This effect requires an active viral DNA and seems to be dependent on the early transcription of the viral genome. In the early phase of viral replication, the increase in TPP+ accumulation is insensitive to mitochondrial inhibitors and sensitive to ouabain, and could be due to a hyperpolarization of the plasma membrane. Later during the infectious cycle, enhanced accumulation of the lipophilic cation is sensitive to mitochondrial inhibitors.

The immune response to human cytomegalovirus-induced early nuclear and early membrane antigens and its possible clinical significance

Before replication of the human cytomegalovirus (HCMV) genome takes place, two major antigenic complexes are induced in the infected cell by an early expression of parental viral genome: one (Early antigen or EA) is localised in the nucleus, the other (Early membrane antigen or EMA) on the plasma-membrane. Sequential samples of serum from renal transplant recipients, pregnant women, blood donors and patients with known HCMV disease were examined by means of indirect immunofluorescence tests for the presence of IgG, IgM and IgA antibodies against EA and EMA. Serum antibody reacting with EMA belongs almost exclusively to the IgM class while that reacting with EA may be of the IgG, IgM or IgA class. IgM antibody to EMA seems to be preferentially associated with primary active HCMV infection.

Increased levels of ADP ribosylation during cytomegalovirus replication in human embryo fibroblasts

ADP ribosylation has been studied during human Cytomegalovirus (HCMV) replication in human embryo fibroblasts. The intranuclear level of this enzyme is higher during the whole viral replication cycle with respect to mock infected cells. The increase begins during the first hour ater the addition of the viral stock to the cells. Results are discussed in view of the possibility that this enhanced activity might be correlated with HCMV-induced alteration of the cell chromatin leading to an increase in host cell macromolecular synthesis.

Early enhanced glucose uptake in human cytomegalovirus-infected cells

The uptake rate of some sugars was demonstrated in human embryo fibroblasts following infection by human cytomegalovirus (HCMV) and a significant increase in glucose uptake was demonstrated. Quantitative and sequential analysis of glucose uptake during the HCMV replication cycle showed that the enhanced uptake began during the first 20 h after infection and occurred even when a high glucose level was constantly present in the medium. The increase in sugar uptake requires an active viral genome, de novo protein synthesis and seems to be dependent only on the early transcription of the viral genome, as it did occur when replication of the viral genome was limited (non-permissive cells or cells infected in the presence of DNA synthesis inhibitors).

Detection of antibodies to Legionella pneumophila serogroup 1 by indirect immunofluorescence and enzyme-linked immunosorbent assay

Indirect immunofluorescence and enzyme-linked immunosorbent assay to detect serum antibodies against Legionella pneumophila serotype 1 were compared. A very good agreement was found with the great majority of serum samples (85.07%). For detecting high antibody levels and rise in antibody titres, both methods seem to be suitable, however for the detection of relatively low antibody titres, very important in epidemiological studies, enzyme immunoassay could be more accurate.

In-vivo effect of novobiocin on primary cytomegalovirus infection

.5 mM of novobiocin completely suppresses the replication of human cytomegalovirus (HCMV) in vitro. Based on the evidence that murine cytomegalovirus (MCMV) titres were reduced in vitro by 60% with the same concentration of the drug, the in vivo antiviral activity of novobiocin has been tested in the murine model. The results showed that if treatment started before the infection virus was not isolated from parenchymal organs during treatment. Virus could be isolated 24 h after stopping treatment, but not from kidney or spleen.