Postnatal acquisition of primary rhesus cytomegalovirus infection is associated with prolonged virus shedding and impaired CD4+ T lymphocyte function

Effects of co-infection with Clonorchis sinensis on T cell exhaustion levels in patients with chronic hepatitis B

To investigate the effects of co-infection with Clonorchis sinensis (C. sinensis) on T cell exhaustion levels in patients with chronic hepatitis B, we enrolled clinical cases in this study, including the patients with concomitant C. sinensis and HBV infection. In this study, we detected inhibitory receptors and cytokine expression in circulating CD4+ and CD8+ T cells by flow cytometry. PD-1 and TIM-3 expression levels were significantly higher on CD4+ T and CD8+ T cells from co-infected patients than on those from the HBV patients. In addition, CD4+ T cells and CD8+ T cells function were significantly inhibited by C. sinensis and HBV co-infection compared with HBV single infection, secreting lower levels of Interferon gamma (IFN-γ), Interleukin-2 (IL-2), and TNF-α. Our current results suggested that C. sinensis co-infection could exacerbate T cell exhaustion in patients with chronic hepatitis B. PD-1 and TIM-3 could be novel biomarkers for T cell exhaustion in patients with Clonorchis sinensis and chronic hepatitis B co-infection. Furthermore, it may be one possible reason for the weaker response to antiviral therapies and the chronicity of HBV infection in co-infected patients. We must realize the importance of C. sinensis treatment for HBV-infected patients. It might provide useful information for clinical doctors to choose the right treatment plans.

Protective effect of pre-existing natural immunity in a nonhuman primate reinfection model of congenital cytomegalovirus infection

Congenital cytomegalovirus (cCMV) is the leading infectious cause of neurologic defects in newborns with particularly severe sequelae in the setting of primary CMV infection in the first trimester of pregnancy. The majority of cCMV cases worldwide occur after non-primary infection in CMV-seropositive women; yet the extent to which pre-existing natural CMV-specific immunity protects against CMV reinfection or reactivation during pregnancy remains ill-defined. We previously reported on a novel nonhuman primate model of cCMV in rhesus macaques where 100% placental transmission and 83% fetal loss were seen in CD4+ T lymphocyte-depleted rhesus CMV (RhCMV)-seronegative dams after primary RhCMV infection. To investigate the protective effect of preconception maternal immunity, we performed reinfection studies in CD4+ T lymphocyte-depleted RhCMV-seropositive dams inoculated in late first / early second trimester gestation with RhCMV strains 180.92 (n = 2), or RhCMV UCD52 and FL-RhCMVΔRh13.1/SIVgag, a wild-type-like RhCMV clone with SIVgag inserted as an immunological marker, administered separately (n = 3). An early transient increase in circulating monocytes followed by boosting of the pre-existing RhCMV-specific CD8+ T lymphocyte and antibody response was observed in the reinfected dams but not in control CD4+ T lymphocyte-depleted dams. Emergence of SIV Gag-specific CD8+ T lymphocyte responses in macaques inoculated with the FL-RhCMVΔRh13.1/SIVgag virus confirmed reinfection. Placental transmission was detected in only one of five reinfected dams and there were no adverse fetal sequelae. Viral whole genome, short-read, deep sequencing analysis confirmed transmission of both reinfection RhCMV strains across the placenta with ~30% corresponding to FL-RhCMVΔRh13.1/SIVgag and ~70% to RhCMV UCD52, consistent with the mixed human CMV infections reported in infants with cCMV. Our data showing reduced placental transmission and absence of fetal loss after non-primary as opposed to primary infection in CD4+ T lymphocyte-depleted dams indicates that preconception maternal CMV-specific CD8+ T lymphocyte and/or humoral immunity can protect against cCMV infection.

Protective effect of pre-existing natural immunity in a nonhuman primate reinfection model of congenital cytomegalovirus infection

Congenital cytomegalovirus (cCMV) is the leading infectious cause of neurologic defects in newborns with particularly severe sequelae in the setting of primary CMV infection in the first trimester of pregnancy. The majority of cCMV cases worldwide occur after non-primary infection in CMV-seropositive women; yet the extent to which pre-existing natural CMV-specific immunity protects against CMV reinfection or reactivation during pregnancy remains ill-defined. We previously reported on a novel nonhuman primate model of cCMV in rhesus macaques where 100% placental transmission and 83% fetal loss were seen in CD4 + T lymphocyte-depleted rhesus CMV (RhCMV)-seronegative dams after primary RhCMV infection. To investigate the protective effect of preconception maternal immunity, we performed reinfection studies in CD4+ T lymphocyte-depleted RhCMV-seropositive dams inoculated in late first / early second trimester gestation with RhCMV strains 180.92 ( n =2), or RhCMV UCD52 and FL-RhCMVΔRh13.1/SIV gag , a wild-type-like RhCMV clone with SIV gag inserted as an immunological marker ( n =3). An early transient increase in circulating monocytes followed by boosting of the pre-existing RhCMV-specific CD8+ T lymphocyte and antibody response was observed in the reinfected dams but not in control CD4+ T lymphocyte-depleted dams. Emergence of SIV Gag-specific CD8+ T lymphocyte responses in macaques inoculated with the FL-RhCMVΔRh13.1/SIV gag virus confirmed reinfection. Placental transmission was detected in only one of five reinfected dams and there were no adverse fetal sequelae. Viral whole genome, short-read, deep sequencing analysis confirmed transmission of both reinfection RhCMV strains across the placenta with ∼30% corresponding to FL-RhCMVΔRh13.1/SIV gag and ∼70% to RhCMV UCD52, consistent with the mixed human CMV infections reported in infants with cCMV. Our data showing reduced placental transmission and absence of fetal loss after non-primary as opposed to primary infection in CD4+ T lymphocyte-depleted dams indicates that preconception maternal CMV-specific CD8+ T lymphocyte and/or humoral immunity can protect against cCMV infection.

Author Summary

Globally, pregnancies in CMV-seropositive women account for the majority of cases of congenital CMV infection but the immune responses needed for protection against placental transmission in mothers with non-primary infection remains unknown. Recently, we developed a nonhuman primate model of primary rhesus CMV (RhCMV) infection in which placental transmission and fetal loss occurred in RhCMV-seronegative CD4+ T lymphocyte-depleted macaques. By conducting similar studies in RhCMV-seropositive dams, we demonstrated the protective effect of pre-existing natural CMV-specific CD8+ T lymphocytes and humoral immunity against congenital CMV after reinfection. A 5-fold reduction in congenital transmission and complete protection against fetal loss was observed in dams with pre-existing immunity compared to primary CMV in this model. Our study is the first formal demonstration in a relevant model of human congenital CMV that natural pre-existing CMV-specific maternal immunity can limit congenital CMV transmission and its sequelae. The nonhuman primate model of non-primary congenital CMV will be especially relevant to studying immune requirements of a maternal vaccine for women in high CMV seroprevalence areas at risk of repeated CMV reinfections during pregnancy.

Human cytomegalovirus (HCMV) long-term shedding and HCMV-specific immune response in pregnant women with primary HCMV infection

Human cytomegalovirus (HCMV) shedding has been extensively investigated in newborns and in young children, however, much less is known about it in immunocompetent adults. Shedding of HCMV was investigated in saliva, vaginal secretions and urine of pregnant women experiencing primary infection along with the development of the HCMV-specific immune response. Thirty-three pregnant women shed HCMV DNA in peripheral biological fluids at least until one year after onset of infection, while in blood HCMV DNA was cleared earlier. Significantly higher levels of viral load were found in vaginal secretions compared to saliva and urine. All subjects examined two years after the onset of infection showed a high avidity index, with IgM persisting in 36% of women. Viral load in blood was directly correlated with levels of HCMV-specific IgM and inversely correlated with levels of IgG specific for the pentameric complex gH/gL/pUL128L; in addition, viral load in blood was inversely correlated with percentage of HCMV-specific CD4⁺ and CD8⁺ expressing IL-7R (long-term memory, LTM) while viral load in biological fluids was inversely correlated with percentage of HCMV-specific CD4⁺ and CD8⁺ effector memory RA⁺(T_EMRA). In conclusion, viral shedding during primary infection in pregnancy persists in peripheral biological fluids for at least one year and the development of both antibodies (including those directed toward the pentameric complex) and memory T cells are associated with viral clearance.

Fallopian tube stem cell medium of porcine and bovine: In vitro regenerative effect on maturation and parthenogenesis of porcine oocytes

Assisted reproductive technology (ART) has been widely developed over the decades. This advanced technology has shown efficacy in the conception and breeding of an animal. However, several issues such as polyspermy, low maturation rate, and low development rate in vitro remain unresolved. Fallopian tube derived cells are proposed to promote the maturation and development of oocyte. This study aims to characterize porcine (PFTSC) and bovine fallopian tube stem cell (BFTSC) while comparing allogeneic and xenogeneic paracrine effects on porcine oocyte. FTSC of Taiwan yellow cattle (B. indicus) and porcine (Landrace x Yorkshire dam x Duroc) were isolated and identified. Conditioned media (Medium 199 or PZM-3) from porcine and bovine was collected and added to porcine cells during in vitro maturation (IVM) and in vitro culture (IVC). Both PFTSC and BFTSC expressed little CD44, CD105, and CD4. Both cells were induced to transform into chondrocytes, very few cells gave rise to osteocytes and adipocytes. IVM test showed a significant elevation of maturation rate in both groups (Porcine: 66.5 ± 3.5% > 55.9 ± 1.7%, p < .05; Bovine: 68.9 ± 2.3% > 55.9 ± 1.7%, p < .05). IVC test demonstrated markedly reduction of blastocyst in both groups. In a diluted conditioned medium with different concentration, 25% and 50% PFTSC showed a decrease in blastocyst rate which is significantly different, but BFTSC demonstrated no significant difference. PFTSC and BFTSC possessed properties of stem cells. Conditioned media from both PFTSC and BFTSC could improve maturation rate but not blastocyst rate in vitro.

Revisiting Koch's postulate to determine the plausibility of viral transmission by human milk

As breastfeeding is of utmost importance for child development and survival, identifying whether breast milk is a route of transmission for human viruses is critical. Based on the principle of Koch's postulate, we propose an analytical framework to determine the plausibility of viral transmission by breast milk. This framework is based on five criteria: viral infection in children receiving breast milk from infected mothers; the presence of virus, viral antigen, or viral genome in the breast milk of infected mothers; the evidence for the virus in breast milk being infectious; the attempts to rule out other transmission modalities; and the reproduction of viral transmission by oral inoculation in an animal model. We searched for evidence in published reports to determine whether the 5 criteria are fulfilled for 16 human viruses that are suspected to be transmissible by breast milk. We considered breast milk transmission is proven if all 5 criteria are fulfilled, as probable if 4 of the 5 criteria are met, as possible if 3 of the 5 criteria are fulfilled, and as unlikely if less than 3 criteria are met. Only five viruses have proven transmission through breast milk: human T-cell lymphotropic virus 1, human immunodeficiency virus, human cytomegalovirus, dengue virus, and Zika virus. The other 11 viruses fulfilled some but not all criteria and were categorized accordingly. Our framework analysis is useful for guiding public health recommendations and for identifying knowledge gaps amenable to original experiments.

In vitro and in vivo characterization of a recombinant rhesus cytomegalovirus containing a complete genome

Cytomegaloviruses (CMVs) are highly adapted to their host species resulting in strict species specificity. Hence, in vivo examination of all aspects of CMV biology employs animal models using host-specific CMVs. Infection of rhesus macaques (RM) with rhesus CMV (RhCMV) has been established as a representative model for infection of humans with HCMV due to the close evolutionary relationships of both host and virus. However, the only available RhCMV clone that permits genetic modifications is based on the 68-1 strain which has been passaged in fibroblasts for decades resulting in multiple genomic changes due to tissue culture adaptations. As a result, 68-1 displays reduced viremia in RhCMV-naïve animals and limited shedding compared to non-clonal, low passage isolates. To overcome this limitation, we used sequence information from primary RhCMV isolates to construct a full-length (FL) RhCMV by repairing all mutations affecting open reading frames (ORFs) in the 68-1 bacterial artificial chromosome (BAC). Inoculation of adult, immunocompetent, RhCMV-naïve RM with the reconstituted virus resulted in significant viremia in the blood similar to primary isolates of RhCMV and furthermore led to high viral genome copy numbers in many tissues at day 14 post infection. In contrast, viral dissemination was greatly reduced upon deletion of genes also lacking in 68-1. Transcriptome analysis of infected tissues further revealed that chemokine-like genes deleted in 68-1 are among the most highly expressed viral transcripts both in vitro and in vivo consistent with an important immunomodulatory function of the respective proteins. We conclude that FL-RhCMV displays in vitro and in vivo characteristics of a wildtype virus while being amenable to genetic modifications through BAC recombineering techniques.

CD4+ T cell exhaustion revealed by high PD-1 and LAG-3 expression and the loss of helper T cell function in chronic hepatitis B

Background

Immune inhibitory receptors play an important role in chronic infections. However, little is known about their role in hepatitis B virus (HBV) infection. Here, we analyzed the relationship between programmed death-1 (PD-1) and lymphocyte activation gene-3 (LAG-3) expression on CD4⁺ T cells and HBV disease progression.

Results

PD-1 and LAG-3 expression was significantly higher on CD4⁺ T cells from HBV patients than on those from the HCs. In addition, a significant positive correlation was found between the PD-1 and LAG-3 expression levels and the ALT(alanine aminotransferase) level. CD4⁺ T cell function was inhibited by high PD-1 and LAG-3 levels, and CD4⁺ T cells with high PD-1 and LAG-3 expression lost the ability to secrete IFN-γ, IL-2 and TNF-α. Furthermore, blockade of the PD-1 and LAG-3 pathways reversed the damage to CD4⁺ T cell proliferation and cytokine secretion.

Conclusions

CD4⁺ T cell exhaustion during chronic HBV had high PD-1 and LAG-3 expression and the absence of helper T cell cytokines, including IFN-γ, IL-2 and TNF-α. After blocking PD-L1 and LAG-3, CD4⁺ T cell function in chronic hepatitis B patients was partially restored.

Characterization of Baboon Cytomegalovirus Infection in Healthy Adult Baboons (Papio anubis)

Cytomegalovirus (CMV) is a common chronic herpesvirus found in humans and numerous other mammalian species. In people, chronic viruses like CMV can alter overall health and immunity and pose a serious risk for those with an inadequate immune system. In addition, CMV plays an important role in animal health, and could affect the health of vulnerable populations, like endangered species. Previous studies found a high rate of CMV seropositivity among adult baboons (Papio anubis), and results from our laboratory revealed that baboon CMV (BaCMV) seropositivity was correlated with altered immune cell populations. In the current study, we further characterized BaCMV infection in normal, adult baboons. Analysis of blood samples from baboons (age, 6 to 26 y) revealed a low overall prevalence of detectable of BaCMV DNA, with a higher detection rate in aged baboons (older than 15 y). Furthermore, data suggest that individual baboons maintain similar rates of recurrence and levels of BaCMV shedding in saliva over time. Finally, we evaluated multiple commercially available assays for antihuman CMV IgG and IgM for use with baboon sera. Results of this study will improve our understanding of BaCMV and may be directly relevant to other closely related species.

Natural history of postnatal rhesus cytomegalovirus shedding by dams and acquisition by infant rhesus monkeys

BACKGROUND

Human infants frequently acquire human cytomegalovirus (HCMV) through breastfeeding, resulting in persistent high-level viral shedding in saliva and urine and infectivity to others, including pregnant women. Thus, vaccination to interrupt postnatal HCMV transmission is an attractive strategy to prevent HCMV spread and congenital infection. Rhesus CMV (RhCMV) in nonhuman primates is a valuable model for the study of immune strategies to prevent CMV transmission. Although rhesus monkeys typically acquire RhCMV before 1 year of age, the timing and mode of natural infant RhCMV transmission remain unknown.

METHODS

We followed 5 RhCMV-seropositive dams and their infants from birth until weaning, approximately 6 months later. RhCMV DNA levels in plasma, breast milk, saliva, and urine were measured every 2 weeks by quantitative PCR. RhCMV-specific T cell responses in peripheral blood and breast milk were measured by interferon gamma ELISpot assays. Serum IgG antibody levels were measured by ELISA.

RESULTS

Four of five postpartum RhCMV-seropositive mothers had intermittent, low-level RhCMV shedding in breast milk, whereas all had high-magnitude RhCMV shedding in saliva and urine. The kinetics of maternal blood RhCMV-specific T cell responses and viral shedding in urine and saliva did not strongly associate, though dams with consistently high systemic RhCMV-specific T cell responses tended to have undetectable RhCMV shedding in breast milk. All RhCMV-exposed infants had intermittent, low-level RhCMV shedding in saliva during the lactation period, with minimal systemic RhCMV-specific T cell responses.

CONCLUSIONS

Despite exposure to RhCMV shedding in breast milk and other maternal fluids, postnatal mother-to-child RhCMV transmission appears to be less efficient than that of HCMV. A greater understanding of the determinants of RhCMV transmission and its usefulness as a model of HCMV mucosal acquisition may provide insight into strategies to prevent HCMV infections in humans.

Rhesus monkeys for a nonhuman primate model of cytomegalovirus infections

Human cytomegalovirus (HCMV) is the leading opportunistic viral infection in solid organ transplant patients and is the most common congenitally transmitted pathogen worldwide. Despite the significant burden of disease HCMV causes in immunosuppressed patients and infected newborns, there are no licensed preventative vaccines or effective immunotherapeutic treatments for HCMV, largely due to our incomplete understanding of the immune correlates of protection against HCMV infection and disease. Though CMV species-specificity imposes an additional challenge in defining a suitable animal model for HCMV, nonhuman primate (NHP) CMVs are the most genetically related to HCMV. In this review, we discuss the advantages and applicability of rhesus monkey models for studying HCMV infections and pathogenesis and ultimately informing vaccine development.

Maternal CD4+ T cells protect against severe congenital cytomegalovirus disease in a novel nonhuman primate model of placental cytomegalovirus transmission

Elucidation of maternal immune correlates of protection against congenital cytomegalovirus (CMV) is necessary to inform future vaccine design. Here, we present a novel rhesus macaque model of placental rhesus CMV (rhCMV) transmission and use it to dissect determinants of protection against congenital transmission following primary maternal rhCMV infection. In this model, asymptomatic intrauterine infection was observed following i.v. rhCMV inoculation during the early second trimester in two of three rhCMV-seronegative pregnant females. In contrast, fetal loss or infant CMV-associated sequelae occurred in four rhCMV-seronegative pregnant macaques that were CD4(+) T-cell depleted at the time of inoculation. Animals that received the CD4(+) T-cell-depleting antibody also exhibited higher plasma and amniotic fluid viral loads, dampened virus-specific CD8(+) T-cell responses, and delayed production of autologous neutralizing antibodies compared with immunocompetent monkeys. Thus, maternal CD4(+) T-cell immunity during primary rhCMV infection is important for controlling maternal viremia and inducing protective immune responses that prevent severe CMV-associated fetal disease.

The Cellular Localization of Human Cytomegalovirus Glycoprotein Expression Greatly Influences the Frequency and Functional Phenotype of Specific CD4+ T Cell Responses

CMV infection is a significant cause of morbidity and mortality in immunocompromised individuals, and the development of a vaccine is of high priority. Glycoprotein B (gB) is a leading vaccine candidate but the glycoprotein H (gH) pentameric complex is now recognized as the major target for neutralizing Abs. However, little is known about the T cell immune response against gH and glycoprotein L (gL) and this is likely to be an important attribute for vaccine immunogenicity. In this study, we examine and contrast the magnitude and phenotype of the T cell immune response against gB, gH, and gL within healthy donors. gB-specific CD4(+) T cells were found in 95% of donors, and 29 epitopes were defined with gB-specific response sizes ranging from 0.02 to 2.88% of the CD4(+) T cell pool. In contrast, only 20% of donors exhibited a T cell response against gH or gL. Additionally, gB-specific CD4(+) T cells exhibited a more cytotoxic phenotype, with high levels of granzyme B expression. Glycoproteins were effectively presented following delivery to APCs but only gB-derived epitopes were presented following endogenous synthesis. gB expression was observed exclusively within vesicular structures colocalizing with HLA-DM whereas gH was distributed evenly throughout the cytoplasm. Grafting of the C-terminal domain from gB onto gH could not transfer this pattern of presentation. These results reveal that gB is a uniquely immunogenic CMV glycoprotein and this is likely to reflect its unique pattern of endogenous Ag presentation. Consideration may be required toward mechanisms that boost cellular immunity to gH and gL within future subunit vaccines.

Repeated measures study of weekly and daily cytomegalovirus shedding patterns in saliva and urine of healthy cytomegalovirus-seropositive children

Background

To better understand potential transmission risks from contact with the body fluids of children, we monitored the presence and amount of CMV shedding over time in healthy CMV-seropositive children.

Methods

Through screening we identified 36 children from the Atlanta, Georgia area who were CMV-seropositive, including 23 who were shedding CMV at the time of screening. Each child received 12 weekly in-home visits at which field workers collected saliva and urine. During the final two weeks, parents also collected saliva and urine daily.

Results

Prevalence of shedding was highly correlated with initial shedding status: children shedding at the screening visit had CMV DNA in 84% of follow-up saliva specimens (455/543) and 28% of follow-up urine specimens (151/539); those not shedding at the screening visit had CMV DNA in 16% of follow-up saliva specimens (47/303) and 5% of follow-up urine specimens (16/305). Among positive specimens we found median viral loads of 82,900 copies/mL in saliva and 34,730 copies/mL in urine (P = 0.01), while the viral load for the 75th percentile was nearly 1.5 million copies/mL for saliva compared to 86,800 copies/mL for urine. Younger age was significantly associated with higher viral loads, especially for saliva (P < 0.001). Shedding prevalence and viral loads were relatively stable over time. All children who were shedding at the screening visit were still shedding at least some days during weeks 11 and 12, and median and mean viral loads did not change substantially over time.

Conclusions

Healthy CMV-seropositive children can shed CMV for months at high, relatively stable levels. These data suggest that behavioral prevention messages need to address transmission via both saliva and urine, but also need to be informed by the potentially higher risks posed by saliva and by exposures to younger children.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0569-1) contains supplementary material, which is available to authorized users.

Immunity to cytomegalovirus in early life

Cytomegalovirus (CMV) is the most common congenital infection and is the leading non-genetic cause of neurological defects. CMV infection in early life is also associated with intense and prolonged viral excretion, indicating limited control of viral replication. This review summarizes our current understanding of the innate and adaptive immune responses to CMV infection during fetal life and infancy. It illustrates the fact that studies of congenital CMV infection have provided a proof of principle that the human fetus can develop anti-viral innate and adaptive immune responses, indicating that such responses should be inducible by vaccination in early life. The review also emphasizes the fact that our understanding of the mechanisms involved in symptomatic congenital CMV infection remains limited.