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Background The role of viral infection in Alzheimer Disease (AD) pathogenesis is an area of great interest in recent years. Several studies have suggested an association between the human roseoloviruses, HHV-6 and HHV-7, and AD. Amyloid-β (Aβ) plaques are a hallmark neuropathological finding of AD and were recently proposed to have an antimicrobial function in response to infection. Identifying a causative and mechanistic role of human roseoloviruses in AD has been confounded by limitations in performing in vivo studies. Recent -omics based approaches have demonstrated conflicting associations between human roseoloviruses and AD. Murine roseolovirus (MRV) is a natural murine pathogen that is highly-related to the human roseoloviruses, providing an opportunity to perform well-controlled studies of the impact of roseolovirus on Aβ deposition. Methods We utilized the 5XFAD mouse model to test whether MRV induces Aβ deposition in vivo. We also evaluated viral load and neuropathogenesis of MRV infection. To evaluate Aβ interaction with MRV, we performed electron microscopy. RNA-sequencing of a cohort of AD brains compared to control was used to investigate the association between human roseolovirus and AD. Results We found that 5XFAD mice were susceptible to MRV infection and developed neuroinflammation. Moreover, we demonstrated that Aβ interacts with viral particles in vitro and, subsequent to this interaction, can disrupt infection. Despite this, neither peripheral nor brain infection with MRV increased or accelerated Aβ plaque formation. Moreover, −omics based approaches have demonstrated conflicting associations between human roseoloviruses and AD. Our RNA-sequencing analysis of a cohort of AD brains compared to controls did not show an association between roseolovirus infection and AD. Conclusion Although MRV does infect the brain and cause transient neuroinflammation, our data do not support a role for murine or human roseoloviruses in the development of Aβ plaque formation and AD.

Despite the usefulness of guinea pig cytomegalovirus (GPCMV) for studies on congenital CMV infection, its viral mechanisms for the evasion of host defense strategies have not been fully elucidated. We reported previously that GPCMV gp38.1 functions as a viral mitochondria-localized inhibitor of apoptosis-like function, and its weak activity suggested the presence of an additional inhibitory molecule(s). Here, we identified gp38.3-2, a 42-amino-acid (aa) reading frame embedded within the gp38.3 gene that encodes a positional homolog of murine CMV (MCMV) m41. Characterization of gp38.3-2 resulted in the following findings: (i) the aa sequence of gp38.3-2 shows some similarity to that of MCMV m41.1, a viral inhibitor of oligomerization of a member of Bcl-2 family protein BAK, but there is no correspondence in their predicted secondary structures; (ii) gp38.3-2, but not gp38.3, showed inhibitory activities against staurosporine-induced apoptosis; (iii) three-dimensional protein complex prediction suggests that the N-terminal α-helix of gp38.3-2 interacts with residues in the BH3 and BH1 motifs of BAK, and analysis of gp38.3-2 and BAK mutants supported this model; (iv) guinea pig fibroblast cells infected with gp38.3-2-deficient GPCMV strain Δ38.3-2 died earlier than cells infected with rescued strain r38.3-2, resulting in lower yields of Δ38.3-2; (v) Δ38.3-2 exhibited a partial but significant decrease in monocyte and macrophage infection in comparison with r38.3-2; and, however, (vi) little difference in the viral infection of guinea pigs was observed between these two strains. Therefore, we hypothesize that gp38.3-2 contributes little to the evasion of host defense mechanisms under the experimental conditions used. IMPORTANCE Although GPCMV provides a useful animal model for studies on the pathogenesis of congenital CMV infection and the development of CMV vaccine strategies, our understanding of the viral mechanisms by which it evades apoptosis of infected cells has been limited in comparison with those of murine and human CMVs. Here, we report a second GPCMV apoptosis inhibitor (42 amino acids in length) that interacts with BAK, a Bcl-2 family proapoptotic protein. Three-dimensional structural prediction indicated a unique BAK recognition by gp38.3-2 via the BH3 and BH1 motif sequences. Our findings suggest the potential development of BH3 mimetics that can regulate inhibition or induction of apoptosis based on short ~40-amino-acid peptide molecules as with GPCMV.

The guinea pig is the only small animal model for congenital cytomegalovirus (CMV) but requires species-specific guinea pig cytomegalovirus (GPCMV). Infection of epithelial cells and trophoblasts by GPCMV requires the viral glycoprotein pentamer complex (PC) and endocytic entry because of the absence of platelet-derived growth factor receptor alpha (PDGFRA). Endothelial cells represent an important cell type for infection, dissemination in the host, and disease but have been poorly evaluated for GPCMV. Novel endothelial cell lines were established from animal vascular systems, including aorta (EndoC) and placental umbilical cord vein (GPUVEC). Cell lines were characterized for endothelial cell protein markers (PECAM1, vWF, and FLI1) and evaluated for GPCMV infection. Only PC-positive virus was capable of infecting endothelial cells. Individual knockout mutants for unique PC components (GP129, GP131, and GP133) were unable to infect endothelial cells without impacting fibroblast infection. Ectopic expression of PDGFRA in EndoC cells enabled GPCMV(PC(−)) infection via direct cell entry independent of the PC. Neutralizing antibodies to the essential viral gB glycoprotein were insufficient to prevent endothelial cell infection, which also required antibodies to gH/gL and the PC. Endothelial cell infection was also dependent upon viral tegument pp65 protein (GP83) to counteract the IFI16/cGAS-STING innate immune pathway, similar to epithelial cell infection. GPCMV endothelial cells were lytically (EndoC) or persistently (GPUVEC) infected dependent on tissue origin. The ability to establish a persistent infection in the umbilical cord could potentially enable sustained and more significant infection of the fetus in utero. Overall, results demonstrate the importance of this translationally relevant model for CMV research. IMPORTANCE Congenital CMV is a leading cause of cognitive impairment and deafness in newborns, and a vaccine is a high priority. The only small animal model for congenital CMV is the guinea pig and guinea pig cytomegalovirus (GPCMV) encoding functional HCMV homolog viral glycoprotein complexes necessary for cell entry that are neutralizing-antibody vaccine targets. Endothelial cells are important in HCMV for human disease and viral dissemination. GPCMV endothelial cell infection requires the viral pentamer complex (PC), which further increases the importance of this complex as a vaccine target, as antibodies to the immunodominant and essential viral glycoprotein gB fail to prevent endothelial cell infection. GPCMV endothelial cell infection established either a fully lytic or a persistent infection, depending on tissue origin. The potential for persistent infection in the umbilical cord potentially enables sustained infection of the fetus in utero, likely increasing the severity of congenital disease.

Cytomegaloviruses (CMVs) employ an array of strategies designed to interfere with host defence responses against pathogens. Studies on such evasion mechanisms are important for understanding the pathogenesis of CMV diseases. Although guinea pig CMV (GPCMV) provides a useful animal model for congenital CMV infection, its evasion strategies are not fully elucidated. Here, we analysed a genome locus that may encode gene products for the GPCMV evasion mechanisms and found the following. (1) RACE analyses identified five transcripts in the GP38-gp38.4 locus, one of which was a spliced product encoding gp38.1. Similarities in the splicing pattern and gene position of gp38.1 to human CMV UL37 and its exon 1 encoding vMIA (viral mitochondria-localized inhibitor of apoptosis) suggest that the gp38.1 gene encodes an apoptosis inhibitor. (2) In a transient transfection assay, gp38.1 localized in the mitochondria and relocated BAX from the cytoplasm to the mitochondria, although its co-localization with BAK was not evident. Further, the expression of gp38.1 partially reduced staurosporine-induced apoptosis. (3) GPCMV defective in the gp38.1 ORF (Δ38.1) and the virus that rescues the defect (r38.1) were generated. Guinea pig fibroblast cells infected with Δ38.1 died earlier than r38.1-infected cells, which resulted in the lower yields of Δ38.1. (4) In animals, viral loads in the spleens of r38.1-infected guinea pigs were higher than those in the spleens of Δ38.1-infected animals. In conclusion, although GPCMV gp38.1 exerts a vMIA-like function, its inhibitory effect was not robust, suggesting the presence of additional inhibitory molecule(s), such as a BAK-specific inhibitor.

Congenital cytomegalovirus (CMV) is a leading cause of disease in newborns and a vaccine is a high priority. The guinea pig is the only small animal model for congenital CMV but requires guinea pig cytomegalovirus (GPCMV). Previously, a disabled infectious single cycle (DISC) vaccine strategy demonstrated complete protection against congenital GPCMV (22122 strain) and required neutralizing antibodies to various viral glycoprotein complexes. This included gB, essential for all cell types, and the pentamer complex (PC) for infection of non-fibroblast cells. All GPCMV research has utilized prototype strain 22122 limiting the translational impact, as numerous human CMV strains exist allowing re-infection and congenital CMV despite convalescent immunity. A novel GPCMV strain isolate (designated TAMYC) enabled vaccine cross strain protection studies. A GPCMV DISC (PC+) vaccine (22122 strain) induced a comprehensive immune response in animals, but vaccinated animals challenged with the TAMYC strain virus resulted in sustained viremia and the virus spread to target organs (liver, lung and spleen) with a significant viral load in the salivary glands. Protection was better than natural convalescent immunity, but the results fell short of previous DISC vaccine sterilizing immunity against the homologous 22122 virus challenge, despite a similarity in viral glycoprotein sequences between strains. The outcome suggests a limitation of the current DISC vaccine design against heterologous infection.

Infections with herpesviruses, including human roseoloviruses, have been proposed to cause autoimmune disease, but defining a causal relationship and mechanism has been difficult due to the ubiquitous nature of infection and development of autoimmunity long after acute infection. Murine roseolovirus (MRV) is highly related to human roseoloviruses. Herein we show that neonatal MRV infection induced autoimmune gastritis (AIG) in adult mice in the absence of ongoing infection. MRV-induced AIG was dependent on replication during the neonatal period and was CD4+ T cell and IL-17 dependent. Moreover, neonatal MRV infection was associated with development of a wide array of autoantibodies in adult mice. Finally, neonatal MRV infection reduced medullary thymic epithelial cell numbers, thymic dendritic cell numbers, and thymic expression of AIRE and tissue-restricted antigens, in addition to increasing thymocyte apoptosis at the stage of negative selection. These findings strongly suggest that infection with a roseolovirus early in life results in disruption of central tolerance and development of autoimmune disease.

The potential for a donor-derived transmission of porcine cytomegalovirus/porcine roseolovirus (PCMV/PRV) to the recipient has been recognized since pigs were considered candidate donors for xenotransplantation. This review gives a short description of the viral properties and summarizes the current evidence of the effects of PCMV/PRV transmission in preclinical xenotransplantation. Despite evidence that PCMV/PRV does not infect human and non-human primate cells, activation in the transplanted organ and detrimental systemic complications have been described. As PCMV/PRV is a herpesvirus able to establish latency, the importance of adequate screening of donor pigs is emphasized, as no efficient treatment is available. Furthermore, easy and successful ways of elimination of PCMV/PRV from pig herds are indicated.

A vaccine against congenital cytomegalovirus infection is a high priority. Guinea pig cytomegalovirus (GPCMV) is the only congenital CMV small animal model. GPCMV encodes essential glycoprotein complexes for virus entry (gB, gH/gL/gO, gM/gN) including a pentamer complex (gH/gL/GP129/GP131/GP133 or PC) for endocytic cell entry. The cohorts for protection against congenital CMV are poorly defined. Neutralizing antibodies to the viral glycoprotein complexes are potentially more important than an immunodominant T-cell response to the pp65 protein. In GPCMV, GP83 (pp65 homolog) is an evasion factor, and the GP83 mutant GPCMV has increased sensitivity to type I interferon. Although GP83 induces a cell-mediated response, a GP83-only-based vaccine strategy has limited efficacy. GPCMV attenuation via GP83 null deletion mutant in glycoprotein PC positive or negative virus was evaluated as live-attenuated vaccine strains (GP83dPC+/PC-). Vaccinated animals induced antibodies to viral glycoprotein complexes, and PC+ vaccinated animals had sterilizing immunity against wtGPCMV challenge. In a pre-conception vaccine (GP83dPC+) study, dams challenged mid-2nd trimester with wtGPCMV had complete protection against congenital CMV infection without detectable virus in pups. An unvaccinated control group had 80% pup transmission rate. Overall, gB and PC antibodies are key for protection against congenital CMV infection, but a response to pp65 is not strictly necessary.

Animal models to study Alzheimer’s disease (AD) pathogenesis are under development. Since herpesviruses have been postulated to be capable of triggering the pathogenic process, AD animal models (mouse, pig, and non-human primates) should be controlled for the presence of these viruses. Only virus-free models allow studying the genetic factors and the effect of adding viruses. Roseoloviruses such as human herpesvirus 6 and the related viruses in the animals are the main topic of this commentary.

Введение. Вирус герпеса человека 6-го типа (ВГЧ-6) способен вызывать активную и латентную инфекции, для диагностики которых применяются количественные различия в содержании вирусной ДНК в крови пациентов. Цель. Изучение количественной характеристики ВГЧ-6 инфекции у детей с различными проявлениями розеоловирусной инфекции. Материалы и методы. Для исследований сформированы следующие группы пациентов с различными проявлениями клинически подозреваемой розеоловирусной инфекции: дети с нейроинфекциями (№ 1), с экзантемными инфекциями неуточненной этиологии (№ 2), с фармакорезистентной эпилепсией / пароксизмальным приступом (№ 3). В качестве групп сравнения в исследованиях участвовали здоровые дети (№ 4) и дети с острой кишечной инфекцией (ОКИ) (№ 5). Количественное выявление ДНК ВГЧ-6 проводили в образцах сыворотки, клеток крови, слюны пациентов с помощью набора реагентов «АмплиСенс EBV/CMV/HHV6-cкрин-FL» для проведения ПЦР в режиме реального времени. Результаты. В доступном для исследования биологическом материале (у здоровых детей – только слюна) ДНК ВГЧ-6 была выявлена у детей всех обследованных групп. В значительной концентрации (более 1000 ГЭ/мл), свидетельствующей об активной инфекции, ДНК ВГЧ-6 была зарегистрирована в отдельных случаях только в группах детей с нейроинфекциями (№ 1), экзантемными инфекциями неуточненной этиологии (№ 2), с фармакорезистентной эпилепсией / пароксизмальным приступом (№ 3). У детей в группах сравнения (№ 4, 5) концентрация генетического материала ВГЧ-6 в биологических образцах не превышала 1000 ГЭ/мл. Заключение. Полученные результаты согласуются с позицией зарубежных специалистов о необходимости установления количественных показателей вирусной нагрузки для определения формы розеоловирусной инфекции. В наших исследованиях высокие концентрации ДНК ВГЧ-6 в исследуемом биологическом материале, указывающие на наличие активной розеоловирусной инфекции, регистрировались в группах детей с характерными ее клиническими проявлениями, но не у детей групп сравнения (здоровые дети, дети с ОКИ). Вместе с тем обнаруженные различия не были статистически значимыми для всех сформированных групп пациентов (p>0,05), что может быть связано с недостаточным их количественным составом и диктует необходимость проведения более масштабных исследований., Introduction. Human herpesvirus type 6 (HHV-6) causes active and latent infections, the diagnosis of which depends on the amount of DNA in the patient's blood. Purpose. To study the quantitative characteristics of HHV-6 infection in children with various manifestations of roseolovirus infection. Materials and methods. The study included the following groups of patients with various manifestations of clinically suspected roseolovirus infection: children with neuroinfections (№ 1), exanthemic infections of unspecified etiology (№ 2), with drug-resistant epilepsy / paroxysmal seizure (№ 3). Healthy children (№ 4) and children with gastroenteritis (№ 5) participated in the studies as the groups of comparison. Quantitative detection of HHV-6 DNA was carried out in the samples of serum, blood cells, and saliva of patients using the "AmpliSens EBV / CMV / HHV6-screen- FL" reagent kit for real-time PCR. Results. HHV-6 DNA was detected in the biological material of all examined groups (only saliva was available from healthy children). In a significant concentration (more than 1000 copies per ml), indicating an active infection, HHV-6 DNA was registered in some cases in the groups of children with neuroinfections (№ 1), exanthemic infections of unspecified etiology (№ 2), with pharmacoresistant epilepsy / paroxysmal attack (№ 3). In children from the comparison groups (№ 4, 5), the concentration of HHV-6 genetic material in biological samples did not exceed 1000 copies per ml. Conclusion. The obtained results are consistent with the position of foreign experts on the need to establish quantitative indicators of viral load to determine the form of roseolovirus infection. In our studies, high concentrations of HHV-6 DNA in the biological material, indicating the presence of active roseolovirus infection, were registered in the groups of children with its typical clinical manifestations, but not in children of the groups of comparison (healthy children, children with gastroenteritis). At the same time, the found differences were not statistically significant for all the formed groups of patients (p, Лабораторная диагностика. Восточная Европа, Выпуск 4 2021, Pages 438-443

Backgroung Roseolovirus latency and persistence in salivary glands that are frequently reactivated after renal transplantation to cause infection have been reported. However, limited information is available on the persistence and excretion of HHV-6 and HHV-7 during and after transplant. Methods 32 renal transplant recipients were followed up before (T1) and after transplant (T2 and T3) and viral replication (via assessment of mRNA) in oral fluid samples investigated. Roseolovirus DNA was detected and quantified via multiplex qPCR. For evaluation of mRNA replication, positive samples were subjected to nested RT-PCR. Results Viral replication of HHV-7 was significantly increased during T3 (72.9%), compared to the pre-transplant period T1 (25%; McNemar Test, p= 0.001). Analysis of the viral replicative to quantitative ratio disclosed ahigher number of DNA copies (>106) in positive cases of replication (p

Cytomegaloviruses (CMVs) encode various immunoevasins, including viral receptors for the Fc domain of host IgG (vFcγR), to evade host immune responses. Although guinea pig CMV (GPCMV) provides a useful animal model for congenital CMV infection, the GPCMV genes encoding such receptors have not yet been characterized. In this study, we analyzed a locus that may encode gene products for the GPCMV immune evasion mechanisms and identified the following. (a) RACE analyses identified four transcripts in the GP117 to GP122 locus. One of the transcripts contained the GP119.1 ORF, which has weak homologies with human CMV UL119/UL118 encoding a viral FcγR and with guinea pig FcγR. (b) A transient transfection assay with plasmids expressing EGFP-tagged GP119.1 or its mutated forms identified its true translational initiation site, localization mainly in the endoplasmic reticulum, and N-glycosylation. (c) Importantly, GP119.1 bound to guinea pig IgG or the IgG-Fc fragment. (d) GP119.1 is present in the virion with a molecular mass of 15 and 23~30 kDa, and a portion of the GP119.1 products are N-glycosylated. (e) GP119.1 was dispensable for viral growth on guinea pig fibroblasts and epithelial cells in vitro. Taken together, our findings indicate that GP119.1 is an IgG-Fc binding glycoprotein incorporated into the virion, and this finding warrants further studies on the functions of GP119.1 in animal models.

Background: Human herpesviruses (HHV)-6A, HHV-6B and HHV-7 are considered to be involved in the pathogenesis of epilepsy, a common neurological disorder. The objective of this study was to determine the association of roseoloviruses infection with epilepsy. Methods: 53 epilepsy patients and 104 ordinary blood donors were analyzed to determine presence of virus-specific antibodies by enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assay (IFA), genomic sequences, viral load and gene expression by polymerase chain reactions (PCRs) and restriction analysis, HHV-6 protein expression by IFA and level of cytokines by ELISA. Results: Roseoloviruses genomic sequences in DNA samples from whole blood were found in 86.8% of patients versus 54.8% of controls and active infection was revealed only in patients with epilepsy (19.6% of roseolovirus-positive patients). Significantly higher viral load and more frequent gene expression was detected in patients compared to the controls. HHV-6-encoded protein expression was demonstrated in 53.3% of patients with previously detected HHV-6 DNA. Changes in level of cytokines were determined in patients with elevated viral load compared to the patients without elevated viral loads and to the controls. Conclusions: Results on frequent active HHV-6 and HHV-7 infection in epilepsy patient&rsquo, peripheral blood indicate on possible involvement of these viruses in the disease development.

Human betaherpesviruses 6A and 6B (HHV-6A and HHV-6B) are highly prevalent in human populations. The genomes of these viruses can be stably integrated at the telomeres of human chromosomes and be vertically transmitted (inherited chromosomally integrated HHV-6A/HHV-6B, iciHHV-6A/iciHHV-6B). We reconstructed the population structures of HHV-6A and HHV-6B, showing that HHV-6A diverged less than HHV-6B genomes from the projected common ancestral population. Thus, HHV-6B genomes experienced stronger drift, as also supported by calculation of nucleotide diversity and Tajima’s D. Analysis of ancestry proportions indicated that HHV-6A exogenous viruses and iciHHV-6A derived most of their genomes from distinct ancestral sources. Conversely, ancestry proportions were similar in exogenous HHV-6B viruses and iciHHV-6B. In line with previous indications, this suggests the distinct exogenous viral populations that originated iciHHV-6B in subjects with European and Asian ancestry are still causing infections in the corresponding geographic areas. Notably, for both iciHHV-6A and iciHHV-6B, we found that European and American sequences tend to have high proportions of ancestry from viral populations that experienced considerable drift, suggesting that they underwent one or more bottlenecks followed by population expansion. Finally, analysis of HHV-6B exogenous viruses sampled in Japan indicated that proportions of ancestry components of most of these viruses are different from the majority of those sampled in the USA. More generally, we show that, in both viral species, both integrated and exogenous viral genomes have different ancestry components, partially depending on geographic location. It would be extremely important to determine whether such differences account for the diversity of HHV-6A/HHV-6B-associated clinical symptoms and epidemiology. Also, the sequencing of additional exogenous and integrated viral genomes will be instrumental to confirm and expand our conclusions, which are based on a relatively small number of genomes, sequenced with variable quality, and with unequal sampling in terms of geographic origin.

The development of a vaccine against congenital human cytomegalovirus (HCMV) infection is a major priority. The pentameric complex (PC) of virion envelope proteins gH, gL, UL128, UL130, and UL131A is a key vaccine target. To determine the importance of immunity to the homologous PC encoded by guinea pig cytomegalovirus (GPCMV) in preventing congenital CMV, PC-intact and PC-deficient live-attenuated vaccines were generated and directly compared for immunogenicity and efficacy against vertical transmission in a vertical transmission model. A virulent PC-intact GPCMV (PC/intact) was modified by galK mutagenesis either to abrogate PC expression (PC/null; containing a frame-shift mutation in GP129, homolog of UL128) or to delete genes encoding three MHC Class I homologs and a protein kinase R (PKR) evasin while retaining the PC (3DX/Δ145). Attenuated vaccines were compared to sham immunization in a two-dose preconception subcutaneous inoculation regimen in GPCMV seronegative Hartley guinea pigs. Vaccines induced transient, low-grade viremia in 5/12 PC/intact-, 2/12 PC/null-, and 1/11 3DX/Δ145-vaccinated animals. Upon completion of the two-dose vaccine series, ELISA titers for the PC/intact group (geometic mean titer (GMT) 13,669) were not significantly different from PC/null (GMT 8127) but were significantly higher than for the 3DX/Δ145 group (GMT 6185; p < 0.01). Dams were challenged with salivary gland-adapted GPCMV in the second trimester. All vaccines conferred protection against maternal viremia. Newborn weights were significantly lower in sham-immunized controls (84.5 ± 2.4 g) compared to PC/intact (96 ± 2.3 g), PC/null (97.6 ± 1.9 g), or 3DX/Δ145 (93 ± 1.7) pups (p < 0.01). Pup mortality in sham-immunized controls was 29/40 (73%) and decreased to 1/44 (2.3%), 2/46 (4.3%), or 4/40 (10%) in PC/intact, PC/null, or 3DX/Δ145 groups, respectively (all p < 0.001 compared to control). Congenital GPCMV transmission occurred in 5/44 (11%), 16/46 (35%), or 29/38 (76%) of pups in PC/intact, PC/null, or 3DX/Δ145 groups, versus 36/40 (90%) in controls. For infected pups, viral loads were lower in pups born to vaccinated dams compared to controls. Sequence analysis demonstrated that infected pups in the vaccine groups had salivary gland-adapted GPCMV and not vaccine strain-specific sequences, indicating that congenital transmission was due to the challenge virus and not vaccine virus. We conclude that inclusion of the PC in a live, attenuated preconception vaccine improves immunogenicity and reduces vertical transmission, but PC-null vaccines are equal to PC-intact vaccines in reducing maternal viremia and protecting against GPCMV-related pup mortality.

Currently there are about 200 different studied herpes viruses, only 8 types are pathogenic for humans. They all belong to the family Herpesviridae, which according to the structure of the virion and biological properties is divided into three subfamilies: α, β, and γ. Human herpesvirus 6B belongs to the subfamily of β-herpesvirus, genus Roseolovirus. The overview of current information on the etiology, epidemiology, clinical manifestations of infection caused by human herpesvirus 6B is presented. The diagnosis of the viral exanthema using modern laboratory technology is considered.

Guinea pig cytomegalovirus (GPCMV) immediate early proteins, IE1 and IE2, demonstrated structural and functional homologies with human cytomegalovirus (HCMV). GPCMV IE1 and IE2 co-localized in the nucleus with each other, the viral polymerase and guinea pig ND10 components (gpPML, gpDaxx, gpSp100, gpATRX). IE1 showed direct interaction with ND10 components by immunoprecipitation unlike IE2. Additionally, IE1 protein disrupted ND10 bodies. IE1 mutagenesis mapped the nuclear localization signal to the C-terminus and identified the core domain for gpPML interaction. Individual knockout of GPCMV GP122 or GP123 (IE2 and IE1 unique exons respectively) was lethal to the virus. However, an IE1 mutant (codons 234–474 deleted), was viable with attenuated viral growth kinetics and increased susceptibility to type I interferon (IFN-I). In HCMV, the IE proteins are important T cell target antigens. Consequently, characterization of the homologs in GPCMV provides a basis for their evaluation in candidate vaccines against congenital infection.

Human herpesviruses 6A, 6B, and 7 (HHV-6A, HHV-6B, HHV-7) are genetically related to cytomegalovirus. They belong to the Roseolovirus genus and to the Betaherpesvirinae subfamily. They infect T cells, monocytes-macrophages, epithelial cells, and central nervous system cells. These viruses are ubiquitous and are responsible for lifelong chronic infections, most often asymptomatic, in the vast majority of the general adult population. HHV-6B is responsible for exanthema subitum, which is a benign disease of infants. HHV-6A and HHV-6B also cause opportunistic infections in immunocompromised patients: encephalitis, hepatitis, bone marrow suppression, colitis, and pneumonitis. Their etiological role in chronic diseases such as multiple sclerosis, cardiomyopathy, and thyroiditis is still controversial. The pathogenicity of HHV-7 is less clear and seems to be much more restricted. Chromosomal integration of HHV-6A and HHV-6B is transmissible from parents to offspring and observed in about 1% of the general population. This integration raises the question of potential associated diseases and can be a confounding factor for the diagnosis of active infections by both viruses. The diagnosis of HHV-6A, HHV-6B, and HHV-7 infections is rather based on gene amplification (PCR), which allows for the detection and quantification of the viral genome, than on serology, which is mainly indicated in case of primary infection. Ganciclovir, foscarnet, and cidofovir inhibit the replication of HHV-6A, HHV-6B, and HHV-7. Severe infections may thus be treated but these therapeutic indications are still poorly defined.

Human herpesvirus 6A (HHV-6A) and 6B (HHV-6B) are members of the genus Roseolovirus in the Betaherpesvirinae subfamily. HHV-6B infects humans in the first years of life, has a seroprevalence of more than 90% and causes Roseola Infantum, but less is known about HHV-6A. While most other herpesviruses maintain their latent genome as a circular episome, HHV-6A and HHV-6B (HHV-6A/B) have been shown to integrate their genome into the telomeres of infected cells. HHV-6A/B can also integrate into the chromosomes of germ cells, resulting in individuals carrying a copy of the virus genome in every nucleated cell of their bodies. This review highlights our current understanding of HHV-6A/B integration and reactivation as well as aspects that should be addressed in the future of this relatively young research area. It forms part of an online symposium on the prevention and therapy of DNA virus infections, dedicated to the memory of Mark Prichard.

Congenital cytomegalovirus (CMV) infection is a leading cause of mental retardation and deafness in newborns. The guinea pig is the only small animal model for congenital CMV infection. A novel CMV vaccine was investigated as an intervention strategy against congenital guinea pig cytomegalovirus (GPCMV) infection. In this d isabled i nfectious s ingle- c ycle (DISC) vaccine strategy, a GPCMV mutant virus was used that lacked the ability to express an essential capsid gene (the UL85 homolog GP85 ) except when grown on a complementing cell line. In vaccinated animals, the GP85 mutant virus (GP85 DISC) induced an antibody response to important glycoprotein complexes considered neutralizing target antigens (gB, gH/gL/gO, and gM/gN). The vaccine also generated a T cell response to the pp65 homolog (GP83), determined via a newly established guinea pig gamma interferon enzyme-linked immunosorbent spot assay. In a congenital infection protection study, GP85 DISC-vaccinated animals and a nonvaccinated control group were challenged during pregnancy with wild-type GPCMV (10 5 PFU). The pregnant animals carried the pups to term, and viral loads in target organs of pups were analyzed. Based on live pup births in the vaccinated and control groups (94.1% versus 63.6%), the vaccine was successful in reducing mortality ( P = 0.0002). Additionally, pups from the vaccinated group had reduced CMV transmission, with 23.5% infected target organs versus 75.9% in the control group. Overall, these preliminary studies indicate that a DISC CMV vaccine strategy has the ability to induce an immune response similar to that of natural virus infection but has the increased safety of a non-replication-competent virus, which makes this approach attractive as a CMV vaccine strategy. IMPORTANCE Congenital CMV infection is a leading cause of mental retardation and deafness in newborns. An effective vaccine against CMV remains an elusive goal despite over 50 years of CMV research. The guinea pig, with a placenta structure similar to that in humans, is the only small animal model for congenital CMV infection and recapitulates disease symptoms (e.g., deafness) in newborn pups. In this report, a novel vaccine strategy against congenital guinea pig cytomegalovirus (GPCMV) infection was developed, characterized, and tested for efficacy. This d isabled i nfectious s ingle- c ycle (DISC) vaccine strategy induced a neutralizing antibody or a T cell response to important target antigens. In a congenital infection protection study, animals were protected against CMV in comparison to the nonvaccinated group (52% reduction of transmission). This novel vaccine was more effective than previously tested gB-based vaccines and most other strategies involving live virus vaccines. Overall, the DISC vaccine is a safe and promising approach against congenital CMV infection.

BACKGROUND Congenital cytomegalovirus infection can be life-threatening and often results in significant developmental deficits and/or hearing loss. Thus, there is a critical need for an effective anti-CMV vaccine. OBJECTIVE To determine the efficacy of replication-defective lymphocytic choriomeningitis virus (rLCMV) vectors expressing the guinea pig CMV (GPCMV) antigens, gB and pp65, in the guinea pig model of congenital CMV infection. METHODS Female Hartley strain guinea pigs were divided into three groups: Buffer control group (n = 9), rLCMV-gB group (n = 11), and rLCMV-pp65 (n = 11). The vaccines were administered three times IM at 1.54 × 10(6)FFU per dose at 21-day intervals. At two weeks after vaccination, the female guinea pigs underwent breeding. Pregnant guinea pigs were challenged SQ at ∼ 45-55 days of gestation with 1 × 10(5)PFU of GPCMV. Viremia in the dams, pup survival, weights of pups at delivery, and viral load in both dam and pup tissues were determined. RESULTS Pup survival was significantly increased in the LCMV-gB vaccine group. There was 23% pup mortality in the gB vaccine group (p = 0.044) and 26% pup mortality in the pp65 vaccine group (p = 0.054) compared to 49% control pup mortality. The gB vaccine induced high levels of gB binding and detectable neutralizing antibodies, reduced dam viremia, and significantly reduced viral load in dam tissues compared to control dams (p < 0.03). Reduced viral load and transmission in pups born to gB-vaccinated dams was observed compared to pups from pp65-vaccinated or control dams. CONCLUSIONS The rLCMV-gB vaccine significantly improved pup survival and also increased pup weights and gestation time. The gB vaccine was also more effective at decreasing viral load in dams and pups and limiting congenital transmission. Thus, rLCMV vectors that express CMV antigens may be an effective vaccine strategy for congenital CMV infection.

As congenital cytomegalovirus (CMV) infection is the major cause of developmental abnormalities in children, the development of effective vaccines is critical to public health. Recent studies have demonstrated that the pentameric complex (Pentamer) of glycoproteins, which is required for human CMV infection of endothelial and epithelial cells, could be a potent vaccine antigen. As guinea pig CMV (GPCMV) infects congenitally and encodes homologues of all Pentamer components, GPCMV models are considered to be useful for the development of vaccine strategies. Here, to clarify the precise requirement of GP131, one of the GPCMV Pentamer components, for the infection of epithelial cells and macrophages, we prepared several mutants with a charged amino acid-to-alanine alteration in GP131 and found some differences in the effects of the mutations on the infection of the two cell types, suggesting the existence of cell type-dependent recognition or function of Pentamer in GPCMV infection.

Virions are the vehicle for cell-to-cell and host-to-host transmission of viruses. Virions need to be assembled reliably and efficiently, be released from infected cells, survive in the extracellular environment during transmission, recognize and then trigger entry of appropriate target cells, and disassemble in an orderly manner during initiation of a new infection. The betaherpesvirus subfamily includes four human herpesviruses (human cytomegalovirus and human herpesviruses 6A, 6B, and 7), as well as viruses that are the basis of important animal models of infection and immunity. Similar to other herpesviruses, betaherpesvirus virions consist of four main parts (in order from the inside): the genome, capsid, tegument, and envelope. Betaherpesvirus genomes are dsDNA and range in length from ~145 to 240 kb. Virion capsids (or nucleocapsids) are geometrically well-defined vessels that contain one copy of the dsDNA viral genome. The tegument is a collection of several thousand protein and RNA molecules packed into the space between the envelope and the capsid for delivery and immediate activity upon cellular entry at the initiation of an infection. Betaherpesvirus envelopes consist of lipid bilayers studded with virus-encoded glycoproteins; they protect the virion during transmission and mediate virion entry during initiation of new infections. Here, we summarize the mechanisms of betaherpesvirus virion assembly, including how infection modifies, reprograms, hijacks, and otherwise manipulates cellular processes and pathways to produce virion components, assemble the parts into infectious virions, and then transport the nascent virions to the extracellular environment for transmission.

Cytomegalovirus (CMV) subunit vaccine candidates include glycoprotein B (gB), and phosphoprotein ppUL83 (pp65). Using a guinea pig cytomegalovirus (GPCMV) model, this study compared immunogenicity, pregnancy outcome, and congenital viral infection following pre-pregnancy immunization with a three-dose series of modified vaccinia virus Ankara (MVA)-vectored vaccines consisting either of gB administered alone, or simultaneously with a pp65 homolog (GP83)-expressing vaccine. Vaccinated and control dams were challenged at midgestation with salivary gland-adapted GPCMV. Comparisons included ELISA and neutralizing antibody responses, maternal viral load, pup mortality, and congenital infection rates. Strikingly, ELISA and neutralization titers were significantly lower in the gB/GP83 combined vaccine group than in the gB group. However, both vaccines protected against pup mortality (63.2% in controls vs. 11.4% and 13.9% in gB and gB/GP83 combination groups, respectively; p