Search

Aims: Human cytomegalovirus (HCMV) infection is the most common congenital viral infection and the leading cause of lasting perinatal brain damage, with the inflammatory response being the primary cause of pathogenic manifestations. Accordingly, it has been shown that anti-inflammatory drugs can reduce abnormalities in newborn mice infected with mouse cytomegalovirus (MCMV). Since contemporary anti-viral drugs have inadequate efficiency, finding new therapeutic targets that can reduce brain damage is of utmost importance. There are growing indications that cellular prion protein (PrPC) dampens the immune response in various organs and prevents collateral, immune response- mediated pathologies. In addition to being expressed on immune cells, PrPC can also bind to immune cells, suggesting its interaction with immune receptors. Our primary goal is to characterize the role and impact of PrPC on the course and severity of congenital cytomegalovirus infection and associated brain pathology. Material and Methods: Intraperitoneal infection of newborn mice with MCMV recapitulates the major hallmarks of human congenital CMV infection: virus dissemination to the brain parenchyma, neuroinflammation and altered brain development. To determine the correlation between PrPC expression, inflammation and developmental and functional changes, we com-pare the following parameters in infected newborn WT and PrPC-KO mice: i) viral load ; ii) cytokines (FACS, xMAP technology) ; iii) activation status and transcriptional profiles of immune cells (FACS, scRNA-seq) ; iv) CMV-related brain anomalies (IHC). In addition, we monitor the impact of CMV on PrPC biology at the cellular level in vitro (antibody development, FACS, confocal microscopy, immunoblot). Results: We show that CMV infection in different cell lines and primary cells affects the amount of PrPC. After initial strong induction of PrPC expression at early time points of infection, cell-associated PrPC levels are largely reduced, partially by triggering its ADAM10-mediated cell surface shedding. Intriguingly, PrPC-KO mice have significantly lower virus titers in multiple organs, including the brain. Immune cell subsets and mechanisms responsible for more efficient virus clearance in the absence of PrPC protein are still being investigated. Conclusions: Obtained data indicate that PrPC is involved in the immune response to CMV infection in newborn mice. Absence of PrPC improves control of the virus due to enhanced immune system activation.

Congenital human cytomegalovirus (HCMV) infection is the most common viral cause of long-term neurodevelopmental sequelae, including mental retardation, microcephaly and sensorineural hearing loss. As HCMV does not cross the species barrier, we employed a mouse model in which newborn mice are infected by intraperitoneal (i.p.) inoculation of mouse cytomegalovirus (MCMV). Following infection the virus disseminates to the central nervous system (CNS) and replicates in the brain parenchyma. CNS infection leads to the activation of resident microglial cells and the recruitment of peripheral immune cells. In addition, the virus induces delay in cerebellar growth. In our model of congenital MCMV infection, the initial neuroimmune responses are dominated by activation of resident microglial cells and the influx of NK cells, whose appearance coincides with detection of the virus in the brain. The number of NK cells in the CNS peaked at day 8 post infection (p.i.). In addition, we also observed recruitment of other peripheral immune cells, of which CD8+ T cells were the most numerous and peaked on day 21 p.i. Phenotypic analysis showed that MCMV-specific CD8+ T cells are highly activated and display tissue resident memory phenotype during latency. Our results demonstrated the coordinated action of innate and acquired immunity in the clearance of congenital MCMV infection of the brain. Furthermore, the results demonstrated the functional role of antigen-specific CD8+ T cells in protection from virus-induced pathology in the neonatal CNS.

Development of an effective vaccine against human cytomegalovirus (HCMV) is a need of utmost medical importance. Generally, it is believed that a live attenuated vaccine would best provide protective immunity against this tenacious pathogen. Here, we propose a strategy for an HCMV vaccine that aims at the simultaneous activation of innate and adaptive immune responses. An HCMV strain expressing the host ligand ULBP2 for the NKG2D receptor was found to be susceptible to control by natural killer (NK) cells, and preserved the ability to stimulate HCMV-specific T cells. Infection with the ULBP2-expressing HCMV strain caused diminished cell surface levels of MHC class I molecules. While expression of the NKG2D ligand increased the cytolytic activity of NK cells, NKG2D engagement in CD8+ T cells provided co-stimulation and compensated for lower MHC class I expression. Altogether, our data indicate that triggering of both arms of the immune system is a promising approach applicable to the generation of a live attenuated HCMV vaccine.

Congenital human cytomegalovirus (HCMV) infection is the most common cause of long-term neurodevelopmental sequelae, including mental retardation and sensorineural hearing loss. As HCMV does not cross the species barrier, we employed a mouse model in which newborn mice are infected by intraperitoneal (i.p.) inoculation of mouse cytomegalovirus (MCMV). Following i.p. inoculation of newborn mice, the virus disseminates to the CNS and replicates in the brain parenchyma. Histological analysis revealed virus-induced cellular changes in the brain, including perivascular- and tissue-infiltrating leukocytes. In addition, we observed a virus-induced retardation in cerebellum growth, and delay in granular neuron migration. CNS infection is coupled with the activation of resident microglial cells and the recruitment of peripheral immune cells, of which CD8+ T cells were the most numerous and peaked on day 21 post infection. We observed persistent polarization of microglial cells toward proinflammatory phenotype which is characterized by upregulation of MHC class I and II molecules, iNOS and TNFa production. Phenotypic analysis also showed that MCMV-specific CD8+ T cells are highly activated and display tissue resident memory phenotype. Furthermore, by adoptive transfer of CD8+ T cells from MHC class I-restricted TCR transgenic mice with specificity for the MCMV-derived epitope M38, we demonstrate that upon MCMV infection, CD8+ T cells migrated from the periphery to the newborn mouse brain. Additional experiments are required to clarify the mechanisms by which brain-resident memory CD8+ T cells are maintained during persistent MCMV infection and the potential role of activated microglial cells in this proces.

Congenital human cytomegalovirus (HCMV) infection is a leading infectious cause of long-term neurodevelopmental sequelae, including microcephaly, mental retardation and sensorineural hearing loss. The pathogenesis of the central nervous system (CNS) infection may arise as a result of direct damage of CMV-infected neurons or indirectly secondary to inflammatory response to infection. CMV infection of the CNS initiates the production of chemokines and proinflammatory cytokines, resulting in microglial activation and recruitment of systemic inflammatory cells to the CNS. The early cellular immune response is characterized by the efflux of innate immune constituents such as natural killer cells and macrophages. Depending on the tissue microenvironment, macrophages and microglia can acquire distinct functional phenotypes. Two well-established polarized phenotypes are often referred to as classically activated (M1) which have enhanced proinflammatory cytokine production, generate nitric oxide and participate in the elimination of intracellular pathogens, and alterna¬tively activated (M2) which participate in the blockade of inflammatory responses and in the promotion of tissue repair. To investigate the pathogenesis of congenital HCMV infection, we employed a newborn mouse model that recapitulates the major characteristics of CNS infection in human infants, including the route of neuroinvasion and neuropathological findings (Koontz et al., 2008). We showed that an M1 macrophage response is rapidly induced following MCMV infection of the CNS. At later time points post infection we observed phenotypic switch in brain macrophages. Macrophages isolated from brain at later time points express hallmarks of polarization toward an alternatively activated state. During MCMV infection of the CNS, microglia showed persistently activated phenotype and produced TNF-α. Chronic production of this proinflammatory mediator could have adverse effects on the brain, keeping it in a state of constant inflammation. Further studies to evaluate the effects of prolonged neuroimmune activation are necessary to determine its contribution to long-term neuropathological sequelae.

Human cytomegalovirus (HCMV) is a major viral cause of morbidity following congenital infection and a cause of miscarriage during early pregnancy. Employing the murine cytomegalovirus (MCMV) model, we show early pregnancy loss to be due to an exquisite, overwhelming infection of ovarian corpora lutea (CL). Excessive infection of CL granulosa cells, the main producers of progesterone during early pregnancy, was accompanied by a detrimental regulation of key genes involved in the synthesis and degradation of serum progesterone levels and substantial pregnancy loss. In contrast to CL, ovarian follicles are completely resistant to MCMV infection even in highly immunocompromised hosts. Here we have characterized and discussed the mechanisms of differential innate resistance of CL and ovarian follicles to MCMV infection.

INTRODUCTION. NKG2D is a potent activating receptor expressed by cells of innate and adaptive immunity that recognizes cell surface molecules structurally related to MHC-I proteins induced by infection or other type of cellular stress. Engagement of NKG2D leads to cytotoxicity and cytokine secretion by NK cells, or to costimulation of CD8+ T cells. Both human and mouse cytomegalovirus (CMV) developed numerous evasive mechanisms to prevent expression of NKG2D ligands. We have recently shown that insertion of the gene encoding NKG2D ligand in the place of its viral inhibitor is a powerful approach for engineering immunologically attenuated viruses (Slavuljica et al., JCI 2010). Here we present the ability of such recombinant virus to serve as a vaccine vector able to promote robust and protective CD8+ T cell response to various pathogens. METHODS AND RESULTS. On the backbone of MCMV expressing RAE-1 we constructed recombinant viruses bearing immunodominant CD8+ T cell epitopes such as listeriolysin (LLO) of Listeria monocytogenes or SIINFEKL peptide derived from ovalbumin. These epitopes were introduced in the place of MCMV CD8+ T cell epitope m164 by orthotopic peptide swap method (Lemmermann et al., 2011). The recombinant viruses were tested for their capacity to activate NK cells and to induce specific memory CD8+ T cell response. Although extremely attenuated, MCMV expressing RAE1 and foreign epitope induced a strong and long-lasting CD8+ T cell response able to protect immunized mice against bacterial challenge infection. CONCLUSIONS. Our results demonstrated that herpesviruses engineered to express NKG2D ligand in addition to a foreign CD8+ T cell epitope dramatically improved efficacy and longevity of the protective CD8+ T cell response, suggesting that a similar approach could be used in designing new vaccine vectors.

Congenital human cytomegalovirus (HCMV) infections are the most common cause of mental retardation and hearing loss in adolescents. As HCMV does not cross the species barrier, we employed a mouse model to study brain inflammatory responses to perinatal mouse cytomegalovirus (MCMV) infection. Infection of newborn mice led to systemic virus dissemination, with virus persistence in salivary glands and lungs. In the brain of MCMV infected mice, virus titers peaked at day 14 post infection (p.i.), followed by a wave of inflammatory cells, of which CD8 T cells were the most numerous and peaked on day 21 p.i. Histological analysis revealed virus-induced cellular changes in the brain, including perivascular- and tissue-infiltrating leukocytes. In addition, we observed a virus-induced retardation in cerebellum growth, a delay in granular neuron migration and disturbances in radial glia formation. Immunohistological analysis confirmed that day 21 p.i. was the time point with the largest number of tissue-infiltrating T-cells. Phenotypic analysis showed that brain-isolated MCMV-specific CD8 T cells were highly activated, as compared to those in peripheral organs. Interestingly, during the course of MCMV infection, and also after virus clearance, the percentage of CD103 cells increased, indicating the presence of a brain-resident memory T-cell population. Furthermore, by adoptive transfer of CD8 T cells from MHC class I-restricted TCR transgenic mice with specificity for the MCMV-derived epitope M38, we demonstrated that upon viral infection, CD8 T cells migrated from the periphery to the brain of newborn mice, where they continued to expand. Importantly, adoptively transferred transgenic cells did not suppress the endogenous CD8 T cell response

There is a large number of pathogens for which post-infection acquired immunity does not fully protect against re-infection and disease. Therefore, vaccines which offer superior protection compared to the one following natural infection are needed. We have previously demonstrated that a recombinant CMV expressing a cellular ligand for the NKG2D receptor has tremendous potential for the induction of a potent antiviral immune response in spite of a strong attenuation in vivo. In this study we have used a MCMV vector expressing NKG2D ligand RAE-1gamma and the CD8+ T cell epitope of Listeria monocytogenes and have demonstrated that the expression of NKG2D ligand dramatically enhanced the effectiveness and longevity of epitope-specific CD8+ T cell response, conferring protection against a subsequent challenge infection with Listeria monocytogenes. We believe that a similar approach can be used in CD8+ T cell-based vaccination strategies against multiple human pathogens.

We have developed a recombinant mouse cytomegalovirus expressing high affinity NKG2D ligand Rae-1γ (RAE-1γ MCMV). NKG2D is a potent activating receptor expressed by cells of both innate and adaptive immunity. Its importance in CMV immunosurveillance is indicated by the elaborative viral evasion mechanisms evolved to avoid NKG2D. Expression of Rae-1γ by MCMV resulted in profound virus attenuation in vivo. Infection was efficiently controlled by adult and immunologically immature neonatal host as well as immunodeficient hosts. RAE-1γ MCMV was also highly attenuated in naturally more resistant C57BL/6 mice and induced even stronger virus specific CD8+ T cell response upon higher viral load. At early days post infection RAE-1γ MCMV decreased systemic IFNα level, preserved conventional dendritic cells and promoted effector CD8+ T cell response. Despite tight immune control, RAE-1γMCMV infection elicited strong, long-lasting protective immunity. These results prompted us to test vector capacity of Rae-1γ MCMV. Our results indicate that a recombinant virus encoding ligand for the NKG2D receptor might provide a new, powerful approach for development of a safe immunogenic CMV vaccine as well as CMV-based vaccine vector.

The authors showed that passive immunization of mcmv infected newborn mice with virus specific antibodies resulted in reduced rate of mcmv replication and improved cerebellum development in these mice.

Human cytomegalovirus (HCMV) infection of the central nervous system (CNS) is the most frequent cause of congenital abnormalities that include learning disabilities, microcephaly and hearing loss. The pathogenesis of the CNS infection is still insufficiently defined, and may arise upon direct damage of CMV-infected neurons or indirectly, due to inflammatory response to infection. We used a recently established model of murine CMV (MCMV) infection in newborn mice (Koontz T. et al. J. Exp. Med. 2008) to analyze the contribution of humoral immunity to virus clearance from the brain. In brains of MCMV-infected newborn mice treated with immune serum virus titer was reduced below detection limit as compared to brains of mice receiving control (non-immune) serum where significant amounts of virus were recovered. Treatment with MCMV specific monoclonal antibodies also resulted in the reduction of virus titer in the brain. Histopathological analyses revealed significantly less CNS inflammation in mice treated with immune serum or monoclonal antibodies as compared to recipients of control serum or irrelevant antibodies which had marked mononuclear cell infiltrates and prominent glial nodules in the brain parenchyma. Antiviral antibodies were also effective in preventing virus associated developmental abnormalities in MCMV-infected newborn brain in terms of improved neuronal migration and increased cerebellar area as compared to control mice. In conclusion, our data indicate that virus specific antibodies have a protective role in the development of CNS pathology in MCMV infected newborn mice, suggesting that antiviral antibodies are an important component of immunological responses during CMV infection of developing CNS.

Though congenital cytomegalovirus infection represents one of the most common infectious causes of brain damage in the developed world, little is known about the means of virus dissemination to the CNS.

Human Cytomegalovirus (HCMV) infection of the developing CNS results in encephalitis and disordered neuronal migration. Similar pathological manifestations in the CNS, specifically in the cerebellum, are also observed following murine cytomegalovirus (MCMV) infection of neonatal mice. However, the pathogenic mechanisms leading to MCMV and HCMV induced CNS maldevelopment remain undefined. Since neuronal migration and foliation are ongoing in the cerebellum until postnatal day 21, we investigated if peripheral MCMV infection of newborn mice affected postnatal cerebellar development. In this mouse model, newborn Balb/c mice were intra-peritoneally infected with a low titer of MCMV. At 5 days post-infection (dpi) MCMV was detected in the brain parenchyma by using immunohistochemistry, PCR and plaque assays. Infectious virus peaked at 12 dpi but was undetectable by 16 dpi ; however, MCMV genomic DNA was still shown to be present by PCR at 21 dpi. Peripheral infection resulted in delayed cerebellar morphogenesis. Early in infection (P8-P16), cerebellum from MCMV infected mice displayed significantly less foliation than mock infected mice. In addition, the external granular layer (EGL) was increased in thickness suggesting delayed granule neuron migration in infected mice. Both EGL thickness and foliation however, were more comparable to mock infected controls at later time points (P18-21). Since chemokines play a crucial role in neural development and in host immune response to viral infection by recruitment of immune effector cells, we examined the pattern of chemokine expression in the CNS after peripheral MCMV infection of newborn mice. By using Ribonuclease Protection Assays (RPA) we demonstrated that RANTES, MCP-1, IP10 and TCA-3 are the major chemokines expressed in the CNS starting at 8 dpi. MIP1-alpha and MIP1-beta were also present however at lower levels. Chemokine expression levels peaked at 14 dpi and decreased at later time points. However at 21 dpi, RANTES expression was still significantly high compared to MCP-1, IP-10 and TCA-3. Since our results show that the increase in chemokine expression levels correlated with a decrease in viral titer and with delayed cerebellar morphogenesis, these findings suggest that host chemokine expression was associated with MCMV clearance in the CNS, however it may also have an adverse effect on cerebellar development

Cytomegalovirus (CMV) is the most significant infectious cause of congenital abnormalities of the central nervous system including retardation, microcephaly, cerebellar atrophy, hearing loss and blindness. The pathogenesis of a viral infection has not been fully elucidate yet and it may arise either because of direct viral damage to neuronal cells or indirectly because of different humoral factors. We have established a model of murine CMV (MCMV) brain infection in newborn mice. This model was used to determine the effect of MCMV infection on neuronal development. We have focused our analysis on the cerebellum because the majority of its cells mature postnatally making it accessible for our examination. Moreover, cerebellum has distinct cytoarchitecture and migration pattern of its neuronal cells has been well defined therefore each developmental disruption is easy to follow. Newborn mice have been infected intraperitoneally with MCMV. The viral presence in the brain has been analysed by plaque assay on murine embrional fibroblasts. Histological evaluation and immunostaining for different neuronal population was used to detect disturbance in cerebellar development. Mice infected with MCMV consistently showed several abnormalities. The development of cerebellar folia was defective. The position and number of folia was not altered but they expressed delay in growth. Whole cerebellar area, as well as volume, was reduced in size throughout cerebellar development. In infected animals significant delay in granule cell migration from external granular layer (EGL) to internal granular layer (IGL) was detected. Purkinje cell (PC) loss was observed in all stages of postnatal development. Moreover an ectopic PC located in IGL was observed after calbindin staining. Our results revealed marked impairment in neuronal migration and maturation indicating that MCMV infection has multiple influence in neuronal development.

Cytomegalovirus (CMV) is the most significant infectious cause of congenital abnormalities of the central nervous system including retardation, microcephaly, cerebellar atrophy, hearing loss and blindness. The pathogenesis of a viral infection has not been fully elucidate yet and it may arise either because of direct viral damage to neuronal cells or indirectly because of different humoral factors. We have established a model of murine CMV (MCMV) brain infection in newborn mice. We used this model to study neuronal development after MCMV infection and have focused our analysis to the cerebellum because the majority of its cells mature postnatally making it accessible for our examination. Cerebellum has distinct cytoarchitecture and migration pattern of its neuronal cells has been well defined so every developmental disruption is easy to follow. Newborn mice have been infected intraperitoneally with MCMV. The viral presence in the brain has been analysed by plaque assay on murine embrional fibroblasts. Histological evaluation and immunostaining for different neuronal population was used to detect disturbance in cerebellar development. Mice infected with MCMV consistently showed several abnormalities. The development of cerebellar folia was defective. The position and number of folia was not altered but they expressed delay in growth. Whole cerebellar area, as well as volume, was reduced in size throughout cerebellar development. In infected animals significant delay in granule cell migration from external granular layer (EGL) to internal granular layer (IGL) was detected. Purkinje cell (PC) loss was observed in all stages of postnatal development. Moreover an ectopic PC located in IGL was observed after calbindin staining. Our results revealed marked impairment in neuronal migration and maturation indicating that MCMV infection has multiple influence in neuronal development.

PROBLEM: Congenital cytomegalovirus (CMV) infection is among the leading causes of brain disease in infants and the most common non-familial cause of hearing loss in developed countries. Small animal models in adult hosts have recapitulated many of the features of human CMV infection with the exception of brain infection. We have established a model of murine CMV (MCMV) brain infection in newborn mice. We used this model to study the feasibility of antiviral antibodies as a therapy means of CMV infection of the brain. METHOD OF STUDY: Newborn mice have been infected intraperitonealy (IP) with various doses of MCMV. Anti-CMV antisera were IP inoculated at different time points following infection and mice were sacrificed on days 7, 11, 14 and 21 after infection. Control mice received the same amount of non-immune sera or no serum at all. The viral presence in the brain has been analysed by plaque assay on murine embrional fibroblasts and immunohistochemistry. RESULTS: Mice treated with antisera consistently showed lower virus titres as compared to control mice. Consistently with that the histological examination showed reduced local inflammatory changes in mice treated with anti-CMV sera. CONCLUSION: Our results indicate that antiviral antibodies can both prevent the CMV spread to the brain and reduce the infection upon it has been established in the brain. Thus, passive antibody transfer to the host may prove as a valuable therapeutics in the congenital CMV infection.

Infekcija humanim citomegalovirusom (HCMV) spada među najčešće intrauterine i perinatalne virusne infekcije ljudi i predstavlja jedan od glavnih uzroka moždanih oštećenja dojenčadi. Ni danas nije potpuno rasvijetljen mehanizam nastanka tih oštećenja. Kako bi pokušali dati odgovor na to pitanje koristili smo model infekcije mišjim citomegalovirusom (MCMV)na netom okoćenim miševima soja BALB/c, G129 IFNgR-/-(delecija IFN gama receptora , mMT/mMT BALB7c (homozigoti za mutacija na mi lancu, tj. deficitni za B limfocite). Šest do 12 sati po okotu inficirali smo miševe s 2000PFU MCMV-a te pratili titar virusa u mozgu tijekom 3 tjedna. Sedmog, 14. i 21. dana analizirali smo histološke promjene u mozgu inficiranih miševa i usporedili ih s neinficiranim miševima iste dobi i soja. Kod BALB/c miševa virus se javljao u mozgu 5. dana po infekciji, titar je rastao do 9.dana da bi nakon toga padao, a 19 dana ga više nismo mogli detektirati. U G129 IFNgR-/- miševa virus se javljao u mozgu već trećeg dana, rastao je do 11.dana, a niti jedan miš nije doživio 14.dan po infekciji. U mMT/mMT BALB/c miševa virus se javljao 4. dan po infekciji, titar mu je rasto do 9. dana, ali ni ovdje miševi nisu doživjeli 15.dan po infekciji. Titar virusa u mozgu BALB/c miševa bio je niži od onogas u ostala dva soja. Histološkom analizom mozga 7. i 14. dana po infekciji upočili smo da astrociti inficiranih miševa imaju tanja i nepravilnije raspoređena vlakna. Budući da astrociti posreduju u migraciji neurona tijekom razvitka slojeva kore mozga, opisane pojave upućuju na utjecaj CMV infekcije na nastanak razvojnih anomalija mozga. Tek 14. dana se uočavaju i izravna oštećenja u vidu perivaskularnih infiltrata te glijalnih čvorića u kori velikog mozga, hipokampusu i dorzalnom dijelu mezencefalona. Slične promjene uočene su kod sva tri soja, iako nešto izraženije kod G129 IFNgR-/- miševa. Imunohistokemijsko bojenje na virusni antigen pokazalo je pozitivne stanice u hipokampusu i kor velikog mozga kod svih sojeva, te u ependimu bočnih komora kod G129 IFNgR-/- miševa. Naši rezultati upućuju na mogućnost da razvojni poremećaj rasporeda neurona, a ne samo upalni odgovor ili citopatogeni učinak virusa, dovodi do neurološkihposljedica CMV infekcije. S druge strane, bolje preživljavanje BALB/c miševa u odnosu na korištene imunodeficitne transgenične sojeve govori u prilog mogućoj protektivnoj ulozi bilo humoralnog bilo staničnog imunog odgovora.

The effects of irradiation on different cell compartments in the submandibular gland were analyzed in adult C57BL/6 mice exposed to X-ray irradiation and followed up for 10 days. Apoptosis was quantified using the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end labeling method (TUNEL). Cell proliferation was detected using immunohistochemistry for proliferating cell nuclear antigen (PCNA). Radiation-induced apoptosis occurred rapidly, reaching a maximum 3 days post-irradiation. The percentage of apoptotic cells increased with the irradiation dose. At day 1 post-irradiation, cell proliferation was significantly reduced in comparison to sham-irradiated controls. After post-irradiation arrest of the cell cycle, proliferation increased in all gland compartments, reaching a maximum at day 6 post-irradiation. The proliferation response corresponded to the dose of irradiation. We suggest that the reason for gland dysfunction could be the coexistence of high apoptotic and proliferative activity in the irradiated gland.