Cerebral protection in TAVR – can we do without? Impact on stroke rate, length of hospital stay and 12-month mortality

 

Stroke associated with transcatheter aortic valve replacement (TAVR) is a potentially devastating complication. Until recently, the Sentinel™ Cerebral Protection System (CPS; Boston Scientific) has been the only commercially available device for mechanical prevention of TAVR-related stroke. However, its effectiveness is still undetermined.

Methods

Between January 2019 and August 2020 consecutive patients were randomly assigned to TAVR with or without Sentinel™ in a 1:1 fashion. We defined as primary endpoint clinically detectable cerebrovascular events within 72 hours after TAVR, and as secondary endpoints LOS and 12-month mortality. Logistic and linear regression analyses were used to assess associations of Sentinel™ use with endpoints.

Results

Of 411 patients (80±7 y/o, 47.4% female, EuroSCORE II 6.3±5.9%), Sentinel™ was used in 213 (51.8%), with both filters correctly deployed in 189 (46.0%). 20 (4.9%) cerebrovascular events were recorded, 10 (2.4%) of which were disabling strokes. Sentinel™ reduced cerebrovascular events in univariate analysis by 71% (OR 0.29, 95% CI 0.11–0.82; p=0.02) and after multivariate adjustment by 75% (adj. OR 0.25; 95% CI 0.08–0.80; p=0.02). Sentinel™ use was also significantly associated with shorter LOS (8.4±9.6 versus 6.7±6.1 days; p=0.03) and lower 12-month all-cause mortality (15.7% versus 7.5%, p=0.01).

Conclusions

In the present prospective all-comers TAVR cohort, Sentinel™ significantly 1) reduced cerebrovascular events, 2) shortened LOS, and 3) improved 12-month survival. These data promote the use of a CPS when implanting TAVR valves.

Funding Acknowledgement

Type of funding sources: None.

Anticoagulation and outcomes after surgical aortic valve replacement with a biological prosthesis

Background

No strong recommendation exists regarding the use of short-term anticoagulation after surgical aortic valve replacement (SAVR) with a biological prosthesis.

Purpose

Our aim was to analyze outcomes of patients receiving warfarin versus low-molecular weight heparin (LMWH) after isolated SAVR.

Methods

We retrospectively analyzed all adult patients who underwent surgery between 2009 and 2017 at our department (n=598). Exclusion criteria included pre-operative anticoagulation, atrial fibrillation, dialysis, previous aortic valve replacement, or active endocarditis. Patients who were discharged alive were stratified according to the type of anticoagulation (warfarin, n=332, 55.5%; LMWH, n=266, 44.5%). Long-term survival during the follow-up period was analyzed (median follow-up, 5.6 years).

Results

Patients who received warfarin had significantly lower logistic EuroSCORE and were younger (Table 1). Warfarin was more frequently utilized between 2009 and 2014, whereas LMWH was more commonly used between 2015 and 2017. Kaplan-Meier curves in Figure 1 show that patients who received warfarin had significantly superior long-term survival (log-rank test: p=0.002). Multivariable Cox proportional hazards regression analysis confirmed that the use of warfarin was associated with significantly lower risk of long-term mortality when compared with LMWH (hazard ratio [HR] 0.50, 95% confidence interval [CI] 0.34–0.74, p=0.001). Covariables in this model included logistic EuroSCORE, era, and duration of cardiopulmonary bypass.

Conclusions

The present analysis suggests that the use of warfarin is associated with significantly superior survival after SAVR with a biological prosthesis. Our findings require validation in a prospective randomized controlled trial.

Figure 1. Kaplan-Meier survival curves

Funding Acknowledgement

Type of funding source: None

Impact of perinatal hypoxia on the developing brain

Perinatal hypoxia is still one of the greatest threats to the newborn child, even in developed countries. However, there is a lack of works which summarize up-to-date information about that huge topic. Our review covers a broader spectrum of recent results from studies on mechanisms leading to hypoxia-induced injury. It also resumes possible primary causes and observed behavioral outcomes of perinatal hypoxia. In this review, we recognize two types of hypoxia, according to the localization of its primary cause: environmental and placental. Later we analyze possible pathways of prenatal hypoxia-induced injury including gene expression changes, glutaminergic excitatory damage (and a role of NMDA receptors in it), oxidative stress with ROS and RNS production, inflammation and apoptosis. Moreover, we focus on the impact of these pathophysiological changes on the structure and development of the brain, especially on its regions: corpus striatum and hippocampus. These brain changes of the offspring lead to impairments in their postnatal growth and sensorimotor development, and in their motor functions, activity, emotionality and learning ability in adulthood. Later we compare various animal models used to investigate the impact of prenatal and postnatal injury (hypoxic, ischemic or combinatory) on living organisms, and show their advantages and limitations.

Rare causes of respiratory insufficiency in newborns

Congenital lung masses (CLM) the rare group of causes of acute respiratory insufficiency (RI) in newborns include congenital airway pulmonary malformation (CAPM), congenital overinflation, bronchopulmonary sequestration, and bronchial atresia. The presenting group consists of 13 newborns who were admitted to the Neonatal Department of Intensive Medicine (NDIM) during January 1st 2015-December 31st 2019 (8 males, 5 females, 2 premature/11 term newborns, spontaneous delivery: 2, caesarean section: 11) with positive prenatal diagnosis of CAPM in all cases. In 2 cases prenatal intervention was performed (drainage of the amniotic fluid, attempt of thoracentesis). Signs of acute RI immediately after delivery were seen in 5 newborns. Postnatal echocardiographic investigation confirmed the presence of increased pulmonary pressure in 8 patients, no patient had congenital heart abnormality. A thorax x-ray was positive also in asymptomatic patients. Computed tomography in patients brought detailed information about the position, size and character of CAPM. Six patients underwent surgery. In 15.4 % right lungs were affected by cystic malformation and in 23 % left lungs were affected. A final diagnosis of CAPM was confirmed in 5 patients using histopathologic examination. Multidisciplinary cooperation during prenatal as well as postnatal period is necessary.

Impact of asphyxia on red blood cell folate concentration levels in newborns

OBJECTIVES

To determine whether red blood cell (RBC) folate concentration levels are correlated with the occurrence of neonatal asphyxia and to study the effects of gestational age, gender, and mode of delivery on RBC folate concentration levels in newborns.

BACKGROUND

Asphyxia is one of the frequent causes of morbidity and mortality of newborns. Severe perinatal asphyxia can arise due to many factors.

METHODS

In a prospective study, the RBC folate concentrations were determined on day 1 of life in the whole group (n=181) of full-term (n=121) and preterm (n=60) newborns. Immunochemical analysis for the determination of folate in erythrocytes was performed.

RESULTS

RBC folate concentration levels in asphyxiated newborns (n=16) were significantly decreased (median 974 ng/ml; p=0.023) in comparison with healthy newborns. On the other hand, the RBC folate concentration levels were significantly increased in preterm newborns (median 1,212 ng/ml; p=0.01) in comparison with full-term newborns (median 1,098 ng/ml). Higher RBC folate concentration levels were found in newborns which had been delivered by Caesarean section (median 1,188 ng/ml; p=0.02) compared to those born vaginally (median 1,098 ng/ml).

CONCLUSION

Our results confirmed a significant decrease in RBC folate concentration in asphyxiated newborns on their first day of life (Fig. 4, Ref. 36).

Distal monosomy 16p13.3/distal trisomy 2p24.2-pter: molecular-cytogenetic characterisation and phenotype

We describe a 4-year-old boy with various facial dysmorphic features such as downslanting palpebral fissures, ptosis, hypertelorism, broad nasal bridge, small and low-set ears, broad philtrum, and micrognathia. In addition, profound mental retardation, myopia, muscular hypotonia as well as genital and cardiovascular abnormalities are also present. Refinement of the breakpoints by cytogenetic techniques, in particular the increase of banding resolution in conventional cytogenetic analysis, has enabled the correct diagnosis, as proven by fluorescence in situ hybridisation (FISH) using whole chromosome painting and single copy probes. We were able to demonstrate an unbalanced translocation that the patient inherited from his father resulting in a submicroscopic monosomy 16p13.3 and a trisomy 2p24.2-pter.

Effects of combined exposure to pyridostigmine bromide and shaker stress on acoustic startle response, pre-pulse inhibition and open field behavior in mice

The present study investigated the effect of combined exposure of pyridostigmine bromide (PB) and chronic shaker stress on acoustic startle responses (ASR), pre-pulse inhibition (PPI) and open field behavior of adult C57BL/6J mice. PB (10 mg kg(-1) day(-1) for 7 days) or saline was administered subcutaneously using osmotic Alzet minipumps implanted under the skin on the back of the mice. At the same time, the mice were exposed to 7 days of intermittent shaker stress. They were tested for ASR (100 dB and 120 dB stimuli) and PPI (70 dB + 100 dB and 70 dB + 120 dB) in the acoustic startle monitor system. The mice were assessed during the shaker stress on days 2 and 7 and 7, 14, 21 and 28 days after discontinuation of treatment. Separate groups of mice were tested in the open field in 15 min sessions on days 1, 3 and 6 during shaker stress and PB treatment. Exposure of mice to PB resulted in an exaggerated ASR, reduced PPI and non-significant decrease in locomotor activity. These behavioral changes were apparent only during exposure to PB. Repeated shaker stress did not have any effect on sensorimotor functions or open field behavior of mice. There was no prolonged or delayed effect of PB and/or stress on individual behavioral variables. The study found C57BL/6J mice to be behaviorally sensitive to PB treatment.

Teratological study of the herbicide 4-chloro-2-methylphenoxyacetic acid in rabbits

4-Chloro-2-methylphenoxyacetic acid (MCPA) is an aryloxyacetic acid derivative categorised as a plant hormone herbicide. The aim of the study was to evaluate the effect of MCPA on pregnant females and the prenatal development of rabbits. The substance tested was administered orally to pregnant New Zealand White rabbits from day 6 to day 27 of gestation at doses of 5, 10 and 25 mg kg(-1) day(-1). The animals were killed on day 28 of gestation and live fetuses were examined for gross, skeletal and visceral anomalies. Administration of MPCA did not induce any signs of maternal toxicity. There was a significant decrease of fetal and placental weight compared with controls at the highest dose of MPCA. No adverse effect of the substance tested was seen on uterine content variables, e.g. corpora lutea, pre-implantation and post-implantation loss, early, late resorptions, live and dead fetuses and sex ratio. Rabbit fetuses treated with the middle and highest doses of MPCA had a significantly elevated incidence of skull and pelvic bone delays. In conclusion, prenatal administration of MCPA did not exhibit a teratogenic effect on rabbit fetus development.

Effect of melatonin and stobadine on maternal and embryofoetal toxicity in rats due to intrauterine hypoxia induced by phenytoin administration

The aim of the present study was to test the hypothesis that the natural antioxidant melatonin (MEL) and the synthetic antioxidant stobadine (STO) could reduce the incidence of maternal and embryofoetal toxicity in rats due to intrauterine hypoxia. Chronic hypoxia was induced pharmacologically by the administration of the anticonvulsant phenytoin (PHT) during the entire period of pregnancy. PHT disturbed the normal course of pregnancy, affected reproductive parameters and increased the incidence of skeletal anomalies. MEL did not protect the PHT-induced development toxicity in rat. On the other hand, STO partially prevented PHT-induced reduction of foetal and placental weights. Administration of STO also decreased the frequency of pre- and post-implantation loss and resorptions in the PHT group. We concluded that pretreatment of pregnant rats with STO prevented to a certain extent reproductive and foetal development alterations caused by chronic intrauterine hypoxia.

Effect of melatonin on biochemical variables induced by phenytoin in organs of mothers, foetuses and offsprings of rats

The present pre- and postnatal study was carried out to investigate the effect of melatonin (MEL), a potent antioxidant, on biochemical variables in the in vivo model of intrauterine hypoxia in rats. Chronic hypoxia was induced pharmacologically by the administration of the anticonvulsant phenytoin (PHT) during pregnancy. Rats were orally treated by PHT (150 mg/kg) from day 7 to 18 of gestation. MEL in drinking water (40 microg/ml) was administered from day 0 to 19 of gestation. The activity of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase (NAGA) and the level of glutathione (GSH) were used as markers of tissue damage. In the prenatal study PHT-induced toxic damage was associated with an increase in NAGA activity and decrease of GSH level in placenta and in maternal serum and heart. MEL partially inhibited the changes of NAGA activity given above. MEL was able to increase only the decreased level of GSH in maternal heart. PHT decreased the level of GSH and increased the activity of NAGA in foetal organs, the improvement occurred in the liver and lungs, but not in foetal brain. In the postnatal study a significant increase of liver GSH level was found in all (control, MEL, PHT, MEL+PHT) groups of 1-day-old pups, while the activity of NAGA remained unchanged. We did not observe any significant differences in NAGA activity in the lungs and heart of pups. MEL increased the GSH level in lungs and heart. We concluded that administration of MEL during pregnancy partially inhibited the biochemical changes induced by PHT.

Direct liquid chromatography method for retinol, α- and γ-tocopherols in rat plasma

An HPLC method for Vitamins A and E in rat plasma has been developed. The main goals of the method are the small amount of sample, 50 microl, and the direct extraction of analytes in one step with acetone, which is a solvent compatible with the reverse-phase mobile phases. Recoveries, as compared with classical and more tedious methods, were near 100%. The method employs a Supelco Discovery C18 column and methanol/water (95:5, v/v) as mobile phase. After being developed, the method was validated following ICH guidelines, with UV, fluorescence and electrochemical detectors. It proved to be selective, lineal, accurate and precise. This method greatly simplifies sample treatment and that is a critical point when working with a large number of samples.

Glycoprotein gpTRL10 of human cytomegalovirus is dispensable for virus replication in human fibroblasts

Human cytomegalovirus (HCMV) has a coding capacity for glycoproteins which by far exceeds that of other herpesviruses. Few of these proteins have been characterized. Glycoprotein gpTRL10 represents a structural component of HCMV. The protein has no homologous counterparts in other herpesviruses. We have isolated bacterial artificial chromosomes (BACs) harboring the genome from the low passage clinical isolate PAN and constructed a deletion mutant in reading frame TRL10. Our results show that deletion of gpTRL10 has only minimal effects on viral replication in human fibroblasts.

Human cytomegalovirus glycoprotein N (gpUL73-gN) genomic variants: identification of a novel subgroup, geographical distribution and evidence of positive selective pressure

Human cytomegalvirus (HCMV) ORF UL73 is a polymorphic locus, encoding the viral glycoprotein gpUL73-gN, a component of the gC-II envelope complex. The previously identified gN genomic variants, denoted gN-1, gN-2, gN-3 and gN-4, were further investigated in this work by analysing a large panel of HCMV clinical isolates collected from all over the world (223 samples). Sequencing and phylogenetic analysis confirmed the existence of the four gN genotypes, but also allowed the identification of a novel subgroup belonging to the gN-3 genotype, which was designated gN-3b. The number of non-synonymous (d(N)) and synonymous (d(S)) nucleotide substitutions and their ratio (d(N)/d(S)) were estimated among the gN genotypes to evaluate the possibility of positive selection. Results showed that the four variants evolved by neutral (random) selection, but that the gN-3 and gN-4 genotypes are maintained by positive selective pressure. The 223 HCMV clinical isolates were subdivided according to their geographical origin, and four main regions of gN prevalence were identified: Europe, China, Australia and Northern America. The gN variants were found to be widespread and represented within the regions analysed without any significant difference, and no new genotype was detected. Finally, for clinical and epidemiological purposes, a rapid and low-cost method for genetic grouping of the HCMV clinical isolates was developed based on the RFLP revealed by SacI, ScaI and SalI digestion of the PCR-amplified UL73 sequence. This technique enabled us to distinguish all four gN genomic variants and also their subtypes.

Molecular characteristics of some commercial high-molecular-weight hyaluronans

Commercially available hyaluronan (HA) samples were investigated by the method of size exclusion chromatography (SEC). The fractions eluted from the SEC column were on-line molecularly characterized by using a multi-angle laser light scattering (MALLS) photometer. Along with the SEC-MALLS technique, the high-molecular-weight HA biopolymers were (off-line) analyzed by capillary viscometry.

Identification of glycoprotein gpTRL10 as a structural component of human cytomegalovirus

Human cytomegalovirus (HCMV) has a coding capacity for glycoproteins which far exceeds that of other herpesviruses. Few of these proteins have been characterized. We have investigated the gene product(s) of reading frame 10, which is present in both the internal and terminal repeat regions of HCMV strain AD169 and only once in clinical isolates. The putative protein product is a 171-amino-acid glycoprotein with a theoretical mass of 20.5 kDa. We characterized the protein encoded by this reading frame in the laboratory strain AD169 and a recent isolate, TB40E. The results from both strains were comparable. Northern blot analyses showed that the gene was transcribed with early/late kinetics. Two proteins of 22 and 23.5-kDa were detected in virus-infected cells and in cells transiently expressing recombinant TRL10. Both forms contained only high-mannose-linked carbohydrate modifications. In addition, virus-infected cells expressed small amounts of the protein modified with complex N-linked sugars. Image analysis localized transiently expressed TRL10 to the endoplasmic reticulum. Immunoblot analyses as well as immunoelectron microscopy of purified virions demonstrated that TRL10 represents a structural component of the virus particle. Immunoblot analysis in the absence of reducing agents indicated that TRL10, like the other HCMV envelope glycoproteins, is present in a disulfide-linked complex. Sequence analysis of the TRL10 coding region in nine low-passage clinical isolates revealed strain-specific variation. In summary, the protein product of the TRL10 open reading frame represents a novel structural glycoprotein of HCMV and was termed gpTRL10.

Effect of repeated administration of the antioxidant stobadine on the behavior of singly-housed male mice in intraspecies conflict

The aim of the present study was to assess the effect of repeated oral administration of stobadine (70 mg/kg) on the occurrence of selected behavioral elements during exposure to an intraspecies conflict between singly-housed and group-housed male mice. Isolation induced timidity (defensive-escape behavior without attacks) in most mice (87%). This isolation-induced timidity was reduced after stobadine treatment. In the stobadine-treated group, sociable activities (following, climbing) were also decreased. After discontinuation of the treatment (18 days), aggressive behavior tended to increase in the stobadine-treated group. The results of this study are indicative of an inhibitory effect of repeated administration of stobadine on some behavioral activities of singly-housed male mice in an intraspecies conflict.

Characterization of antibody response to human cytomegalovirus in Indian renal transplant patients

BACKGROUND & OBJECTIVES

Cytomegalovirus (CMV) disease in seroendemic transplant populations is due to reactivation of the virus, or reinfection. In this context, the antibody response is likely to influence presentation, clinical severity and outcome of the disease, and may provide a diagnostic and prognostic marker. This study was carried out in Indian renal transplant patients and healthy adults to characterize the antibody response to cytomegalovirus.

METHODS

Thirty three transplant recipients with CMV illness (symptomatology with IgM and/or nPCR positive status), 20 recipients who were asymptomatic in the 6 months of follow up after transplantation and 62 healthy controls were investigated for markers of CMV infection. These individuals were tested for IgG avidity and neutralizing antibody by ELISA techniques.

RESULTS

All 53 transplant recipients were found to have an IgG avidity index of > 50 per cent. Antibody to a CMV envelope glycoprotein gB/AD-1 (putative neutralizing antibody) was expressed as S/N ratio and was > or = 5 in asymptomatic (65%) and symptomatic (27%) immunosuppressed renal transplant recipients. However, none of the 53 CMV IgG positive healthy controls were positive for neutralizing antibodies S/N ratio > or = 5 (S/N ratio = sample mean OD/mean OD of 3 negative controls in each run). We observed the simultaneous presence of CMV PCR signal in leukocytes and neutralizing antibody (S/N ratio > or = 5) in the plasma in 22 (41.5%) of the 53 renal transplant recipients.

INTERPRETATION & CONCLUSIONS

In this study among the immunosuppressed transplant patients we observed an association between symptomatic disease and the relative absence of neutralizing antibodies. The neutralizing antibodies are less frequently demonstrable among controls; while appearance in a higher proportion of asymptomatic recipients especially in association with high IgG avidity (> 90%) is suggestive of its role in control of CMV disease despite reactivation as evidenced by DNAemia while on immunosuppressive therapy.

Intrauterine transmission of cytomegalovirus to infants of women with preconceptional immunity

BACKGROUND

Preconceptional immunity against cytomegalovirus (CMV) provides only partial protection against intrauterine transmission of the virus. Whether congenital CMV infection in the offspring of women who are seropositive for CMV can occur after maternal reinfection with a different strain of CMV is unknown.

METHODS

Serum specimens from 46 women with preconceptional immunity against CMV that were obtained during the previous pregnancy and the current pregnancy were analyzed for antibodies against the strain-specific epitopes of CMV glycoprotein H. Virus-neutralizing activity in maternal serum samples was measured against the AD169 laboratory strain of CMV and the CMV isolates available from seven infected infants. In addition, the nucleotide sequences of the glycoprotein H gene from the seven CMV isolates were determined.

RESULTS

Eleven of the 16 mothers with infected infants (69 percent) had antibodies against the glycoprotein H epitopes present on two laboratory strains of CMV, AD169 and Towne. Ten of the 16 mothers with infected children (62 percent) acquired new antibody specificities against glycoprotein H, as compared with only 4 of the 30 mothers of uninfected infants (13 percent, P<0.001). The samples obtained at the time of the current delivery from four of the seven mothers contained at least twice as many neutralizing antibodies against the CMV isolated from their infants as were present in the samples obtained at the previous delivery. The specificity of the newly acquired maternal antibodies reflected the amino acid sequence of the glycoprotein H epitope of CMV from these four infants.

CONCLUSIONS

In women who are seropositive for CMV, reinfection with a different strain of CMV can lead to intrauterine transmission and symptomatic congenital infection.

The product of human cytomegalovirus UL73 is a new polymorphic structural glycoprotein (gpUL73)

OBJECTIVES

This work focuses on human cytomegalovirus (HCMV) UL73, which encodes for a putative transmembrane glycoprotein that is highly conserved among herpesviruses.

STUDY DESIGN

pUL73 expression was analyzed both in transiently transfected and in HCMV-infected cells using a pUL73-specific antiserum by immunoblot and immunofluorescence. Sequencing analysis from several clinical isolates and laboratory-adapted strains was also performed.

RESULTS

pUL73 expressed in transiently transfected cells consists in a polypeptide of the expected size (15-18 kd) with cytoplasmic localization. In infected cells, pUL73 is expressed with true-late kinetics and localizes both in perinuclear granular formations and on the cell surface. A broad band (39-53 kd), sensitive to O-glycosidase digestion was detected in purified virus. In addition, sequence analysis showed that the N-terminal portion of pUL73 from clinical isolates is highly polymorphic.

CONCLUSIONS

UL73 encodes for a new structural glycoprotein (gpUL73) expressed on the cell surface of infected cells and highly polymorphic among clinical isolates.

Complex formation by human cytomegalovirus glycoproteins M (gpUL100) and N (gpUL73)

The envelope glycoproteins of human cytomegalovirus (HCMV) virions are incompletely characterized. We have analyzed complex formation between glycoprotein M (gM or gpUL100) and a second glycoprotein. gM-homologous proteins are conserved throughout the herpesvirus family and represent type III membrane proteins containing multiple hydrophobic sequences. In extracellular HCMV particles, gM was found to be complexed through disulfide bonds to a second protein with an apparent molecular mass of 50 to 60 kDa. The 50- to 60-kDa protein was found to be derived from reading frame UL73 of HCMV strain AD169. UL73-homologous genes are also conserved within herpesviruses. When transiently expressed by itself, the UL73 gene product consisted of a protein of 18 kDa. However, in the presence of gM, the UL73 gene product was posttranslationally modified to the 50- to 60-kDa species. Thus, gM and the UL73 gene product, which represents the gN homolog of herpesviruses, form a disulfide-linked complex in HCMV virions. Transient expression of gM and gN followed by fluorescence imaging with monoclonal antibodies against either protein demonstrated that complex formation was required for transport of the proteins from the endoplasmic reticulum to the Golgi and trans-Golgi compartments. Finally, we tested the gM-gN complex for reactivity with sera from HCMV-seropositive donors. Whereas most sera failed to react with either gM or gN when expressed alone, 62% of sera were positive for the gM-gN complex. Because a murine monoclonal antibody reactive with gN in the gM-gN complex efficiently neutralizes infectious virus, the gM-gN complex may represent a major antigenic target of antiviral antibody responses.

Dense bodies of human cytomegalovirus induce both humoral and cellular immune responses in the absence of viral gene expression

Infection of fibroblast cell cultures with human cytomegalovirus (HCMV) leads to the production of significant amounts of defective enveloped particles, termed dense bodies (DB). These noninfectious structures contain major antigenic determinants which are responsible for induction of both the humoral and the cellular immune response against HCMV. We tested the hypothesis that, by virtue of their unique antigenic and structural properties, DB could induce a significant immune response in the absence of infectious virus. Mice were immunized with gradient-purified DB, which were either left untreated or subjected to sequential rounds of sonication and freeze-thawing to prevent cellular entry. Titers of neutralizing antibodies induced by DB were in a range comparable to levels present in convalescent human sera. The virus-neutralizing antibody response was surprisingly durable, with neutralizing antibodies detected 12 months following primary immunization. The HCMV-specific major histocompatibility complex class I-restricted cytolytic T-cell (CTL) response was assayed using mice transgenic for the human HLA-A2 molecule. Immunization with DB led to high levels of HCMV-specific CTL in the absence of de novo viral protein synthesis. Maximal total cytolytic activity in mice immunized with DB was nearly as efficient as the cytolytic activity induced by a standard immunization with murine cytomegalovirus. Furthermore, DB induced a typical T-helper 1 (Th1)-dominated immune response in mice, as determined by cytokine and immunoglobulin G isotype analysis. Induction of humoral and cellular immune responses was achieved without the concomitant use of adjuvant. We thus propose that DB can serve as a basis for the future development of a recombinant nonreplicating vaccine against HCMV. Finally, such particles could be engineered for efficient delivery of antigens from other pathogens to the immune system.

Strain-specific neutralization of human cytomegalovirus isolates by human sera

Induction of an effective antibody response against human cytomegalovirus (HCMV) is an important defense mechanism since it is potentially capable of neutralizing infectious viruses. We have analyzed the extent of HCMV strain-specific neutralization capacity in human sera. Nine recent HCMV isolates and their corresponding sera were investigated in cross-neutralization assays. We observed differences, independent of the overall neutralization capacity, in the 50% neutralization titers of the sera against individual strains, differences that ranged from 8-fold to more than 60-fold. For one isolate, complete resistance to neutralization by two human sera was observed. The neutralization capacity of human sera was not influenced by the presence of various concentrations (up to 100-fold excess) of noninfectious envelope glycoproteins, an inherent contamination of virus preparations from recent HCMV isolates. This indicated that the decisive parameter for neutralization is the titer of the neutralizing antibodies and that neutralization is largely independent of the concentration of virus. Analysis with transplant patients revealed that during primary infection strain-specific and strain-common antibodies are produced asynchronously. Thus, our data demonstrate that the induction of strain-specific neutralizing antibodies is a common event during infection with HCMV and that it might have important implications for the course of the infection and the development of anti-HCMV vaccines.

Immunohistochemical studies of productive rhesus cytomegalovirus infection in rhesus monkeys (Macaca mulatta) infected with simian immunodeficiency virus

In humans infected with the human immunodeficiency virus (HIV), clinical disease due to human cytomegalovirus (HCMV) infection is one of the AIDS-defining diseases; HCMV is the most common opportunistic infection found postmortem. Histologically, the typical lesions are characterized by "owl's eye cells." In rhesus monkeys infected with simian immunodeficiency virus (SIV), comparable lesions are caused by an infection with the rhesus CMV (RhCMV). The aim of this study was to investigate the incidence of productive and latent RhCMV infection in monkeys infected with SIV macaques (SIVmac). Eleven SIVmac-infected rhesus monkeys, which were euthanatized after developing AIDS-like disease, and 11 clinically healthy and uninfected animals comprised the study. The monkeys were screened serologically for RhCMV by western-blot analysis. Immunohistochemistry was performed by an indirect immunoperoxidase technique with a polyclonal rabbit RhCMV-antiserum. Lesions characteristic of RhCMV-associated diseases were detected histologically. All animals were latently RhCMV-infected. Seven of eleven (63.6%) SIV-infected macaques were productively RhCMV infected according to immunohistochemistry. RhCMV antigen was identified in the gastrointestinal tract, the hepatobiliary system, the lungs, and the testicles. Two of these seven animals showed characteristic inflammatory lesions associated with productive infection. Consequently, the CMV prevalence in SIVmac-infected rhesus monkeys and human AIDS patients is comparable.

Kinetics of the antibody response against human cytomegalovirus-specific proteins in allogeneic bone marrow transplant recipients

The humoral immune response against human cytomegalovirus (CMV) was retrospectively investigated in >800 serum samples from 31 recipients of allogeneic bone marrow transplants. To this end, an ELISA was performed that allowed the individual analysis of IgG antibodies against known antigenic domains of CMV-derived phospho- and glycoproteins and nonstructural polypeptides. Twenty-nine patients developed active CMV infection after transplantation, as determined by repeatedly positive samples in polymerase chain reaction (PCR) assays. Seventeen patients responded serologically to viral replication by producing CMV-specific antibodies against a variety of antigens. The response was detectable concomitantly with PCR positivity and was seen as early as 20 days after transplantation. High titers of glycoprotein-specific neutralizing antibodies were correlated with the absence of viral DNA in blood (P<.002). Nineteen patients developed CMV disease. Survival was associated with the production of high titers of CMV glycoprotein-specific antibodies in response to viral replication.

Identification of the gene coding for rhesus cytomegalovirus glycoprotein B and immunological analysis of the protein

The nucleotide sequence of the gene encoding glycoprotein B (gB) of rhesus cytomegalovirus (RhCMV) was determined and the protein characterized. The open reading frame of gB encoded a protein of 854 amino acids with 60% identity and 75% similarity at the amino acid level to human cytomegalovirus (HCMV) gB. Cysteine residues in the extraluminal part of the protein are perfectly conserved. Out of the 16 potential N-linked glycosylation sites present in HCMV gB, 15 are conserved in RhCMV gB. Immunoblot analyses with antisera detected three bands of 150 kDa, 90-110 kDa and 55 kDa representing the full-length gB as well as the proteolytic cleavage products. Cross-reactivity and cross-neutralization of a number of HCMV gB-specific monoclonal antibodies with RhCMV gB indicated sharing of immunogenic epitopes between the two molecules. The RhCMV gB regions corresponding to antigenic domains AD-1, 2 and 3 of HCMV gB were immunogenic during natural RhCMV infection with the AD-1 region being the immunodominant domain. The data indicate that RhCMV might represent a useful model to investigate pathogenesis and immune surveillance of cytomegaloviruses.

The humoral immune response against human cytomegalovirus is characterized by a delayed synthesis of glycoprotein-specific antibodies

An individual analysis of IgG antibodies against 12 known antigenic domains of human cytomegalovirus (HCMV)-derived structural phospho- and glycoproteins and nonstructural polypeptides was performed. In HCMV-seropositive healthy persons, the separate determination of antibody titers against the various antigens resulted in an antibody profile that was characteristic for each individual. Profiles were qualitatively stable over a period of >4 years. However, quantitative changes were observed in some persons. During primary HCMV infection, a delay of 50-100 days in the appearance of glycoprotein-specific antibodies was observed, whereas immunoglobulins directed against other HCMV-specific antigens were promptly synthesized. In contrast, during reactivation or reinfection, a synchronized production of antibodies was found. Levels of glycoprotein-specific antibodies and detection of viral DNA in peripheral blood inversely correlated. Precursor B cell analyses showed no significant differences between glycoprotein-specific and phosphoprotein-specific B cells.

Glycoprotein H of human cytomegalovirus is a major antigen for the neutralizing humoral immune response

A recombinant baculovirus expressing glycoprotein H (gpUL75) of human cytomegalovirus was used to examine the humoral immune response in naturally infected individuals. Recombinant baculovirus infected insect cells produced two forms of gH with molecular masses of 78-82 kDa and 94 kDa. The 94 kDa polypeptide was modified by high mannose oligosaccharide side-chains as shown by reduction in molecular mass after treatment with endoglycosidases H and F. The 78-82 kDa protein represented the non-glycosylated precursor which was resistant to the enzymes. In contrast to gH expressed in mammalian cells, the recombinant baculovirus expressed gH was transported to the cell surface. Glycoprotein H produced in insect cells was reactive with human convalescent sera and all tested neutralizing monoclonal antibodies recognizing either linear or conformational epitopes. Antibodies reacting with insect cell derived gH were detected in 96 percent of HCMV seropositive human sera. Using insect cells infected with the gH expressing recombinant baculovirus as immunoabsorbent, between 0 percent and 58 percent of the total virus neutralizing activity was removed from sera of individuals with a past HCMV infection. gH must therefore be considered a major antigen for the induction of neutralizing antibodies during natural infection.

Analysis of T helper cell response to glycoprotein H (gpUL75) of human cytomegalovirus: evidence for strain-specific T cell determinants

The proliferative response of helper T cells against glycoprotein H (gH; gpUL75) of human cytomegalovirus (HCMV) was determined in T cell lines from 5 healthy HCMV-seropositive donors. A differential response in two lines was noted when gH from strain AD169 or Towne was used as antigen. T cell-reactive domains between aa 15 and 510 were identified using beta-galactosidase fusion proteins containing overlapping fragments of gH, and they were confirmed with synthetic peptides as stimulating antigen. T cell proliferation was observed with antigens containing aa 34-51, 111-142, 284-302, 324-342, and 454-510 of gH. None of the determinants stimulated all donors. The T cell epitope defined by aa 34-51 is located in close proximity to a strain-specific dominant B cell epitope; however, no strain dependence for this T cell determinant was observed. In contrast, the dominant T cell response against aa 284-302, which was observed in three T cell lines, was strain specific.

Antibodies specific for the antigenic domain 1 of glycoprotein B (gpUL55) of human cytomegalovirus bind to different substructures

Glycoprotein B (gB, gpUL55) is a major antigen for the induction of neutralizing antibodies against human cytomegalovirus, making it an attractive antigen for active and passive immunoprophylaxis. The immunodominant region on gB is the antigenic domain 1 (AD-1), a complex structure which requires a minimal linear amino acid sequence of more than 75 amino acids (aa 552-635) for antibody binding. We have analyzed the fine specificity of neutralizing and nonneutralizing AD-1-binding monoclonal antibodies. Point mutations were introduced into AD-1 and mutants were expressed as bacterial fusion proteins. The antigens were analyzed in immunoblots using a panel of 13 human and murine monoclonal antibodies. Complete loss of binding of all antibodies was observed with mutations at cysteine residues 573 and 610 as well as with a combinatorial exchange of prolines at position 577 and 613. The remaining mutations had different effects on antibody binding. Six individual recognition patterns were observed, indicating various antigenic substructures on AD-1. Changing the Fc portions of 3 murine monoclonal antibodies to human IgG1 showed that neutralization of AD-1-binding immunoglobulins is exerted by different mechanisms. Dependent on the recognized substructure within AD-1, avidity-dependent as well as Fc portion-mediated effects were observed.

Human cytomegalovirus glycoproteins

The complex biology of human cytomegalovirus (HCMV) necessarily begins with an initial interaction between the envelope of the infectious virion and the host cell. Understanding the initial events of infection will require a further analysis of the glycoprotein components of the virion envelope as well as their expression in the membranes of the infected cell. This experimental goal has been hindered by the large genome of HCMV, which may encode over 65 unique glycoproteins. Protein homologs of only 4 herpes simplex virus (HSV) glycoproteins, gB, gH, gL and gM, have been identified, and potential functions have been postulated based on studies of specific glycoprotein null mutants of HSV and other herpesviruses. Additional glycoproteins have been analyzed but to date their function in the replicative cycle of this virus is unknown. Several of the envelope glycoproteins elicit strong host immune responses, including the production of virus-neutralizing antibodies. This response is felt to be a key component of host immunity and represents a goal of vaccine development. Finally, recent findings have also provided evidence that HCMV glycoproteins may contribute to evasion of host cellular immune responses by limiting viral antigen presentation.

Light chain shuffling of a high affinity antibody results in a drift in epitope recognition

Human polyclonal and monoclonal antibodies against pathogens and toxins are potentially useful in the treatment of various diseases. A number of human monoclonal antibodies with protective capacity in vitro have been established by conventional hybridoma technology. However, with the development of phage-display technology, the possibility of specifically tailoring antigen-binding properties has improved substantially. We show here that the reactivity of a high affinity, virus-neutralizing human antibody against the AD-2 epitope of cytomegalovirus gB can be modified by introducing other Vkappa sequences together with the original VH sequence. The fine specificity, as determined by the requirement of particular amino acid residues in the epitope, is shifted in these new antibody fragments. It was also evident that the VH/Vkappa pairing was not promiscuous, since antibody fragments selected by phage display retained light chain sequences very similar to the original hybridoma-derived light chain, proving that a high affinity interaction was very dependent on a co-operativity between both variable domains. These findings show that phage display technology might modify the binding properties of pre-existing, high affinity antibodies.

Searching for antibodies specific for human cytomegalovirus: is it diagnostically useful? When and how

Diagnosis of human cytomegalovirus (CMV) infection can be obtained by direct demonstration of the virus or virus components in pathological materials or indirectly through serology. Serological diagnosis gives only indirect evidence of the presence of the virus, and is problematic because of the immunological disorders occurring in most patients at risk of developing a CMV infection. Furthermore, antigenic reagents used in commercially available kits are not standardized and discordant results are often obtained. However, serology is cheaper than the other diagnostic tests, requires a short execution time, is safe and can be completely automated. Therefore, it is worthwhile exploring the possible application fields in which the use of serology is justified nowadays. This is what this review will attempt to do.