HHV-6 infection during pregnancy and spontaneous abortion

Metagenomic profiling of placental tissue suggests DNA virus infection of the placenta is rare

It is widely recognized that pathogens can be transmitted across the placenta from mother to foetus. Recent re-evaluation of metagenomic studies indicates that the placenta has no unique microbiome of commensal bacteria. However, viral transmission across the placenta, including transmission of DNA viruses such as the human herpesviruses, is possible. A fuller understanding of which DNA virus sequence can be found in the placenta is required. We employed a metagenomic analysis to identify viral DNA sequences in placental metagenomes from full-term births (20 births), pre-term births (13 births), births from pregnancies associated with antenatal infections (12 births) or pre-term births with antenatal infections (three births). Our analysis found only a small number of DNA sequences corresponding to the genomes of human herpesviruses in four of the 48 metagenomes analysed. Therefore, our data suggest that DNA virus infection of the placenta is rare and support the concept that the placenta is largely free of pathogen infection.

Maternal natural killer cells at the intersection between reproduction and mucosal immunity

Many maternal immune cells populate the decidua, which is the mucosal lining of the uterus transformed during pregnancy. Here, abundant natural killer (NK) cells and macrophages help the uterine vasculature adapt to fetal demands for gas and nutrients, thereby supporting fetal growth. Fetal trophoblast cells budding off the forming placenta and invading deep into maternal tissues come into contact with these and other immune cells. Besides their homeostatic functions, decidual NK cells can respond to pathogens during infection, but in doing so, they may become conflicted between destroying the invader and sustaining fetoplacental growth. We review how maternal NK cells balance their double duty both in the local microenvironment of the uterus and systemically, during toxoplasmosis, influenza, cytomegalovirus, malaria and other infections that threat pregnancy. We also discuss recent developments in the understanding of NK-cell responses to SARS-Cov-2 infection and the possible dangers of COVID-19 during pregnancy.

Inherited Chromosomally Integrated Human Herpesvirus 6 Is a Risk Factor for Spontaneous Abortion

BACKGROUND

Human herpesvirus 6 (HHV-6) can be genetically transmitted from parent to child as inherited chromosomally integrated HHV-6 (iciHHV-6). HHV-6 reactivation occurs in pregnant women with iciHHV-6. We found no sex differences in the frequency of index cases with iciHHV-6 but inheritance from the father was more common. We evaluated the association between iciHHV-6 status and spontaneous abortion.

METHODS

iciHHV-6 was confirmed by high viral DNA copy numbers in whole blood and somatic cells. The origin of integrated viral genome, paternal or maternal, was examined using the same method. The pregnancy history of 23 mothers in families with iciHHV-6 and 285 mothers in families without iciHHV-6 was abstracted.

RESULTS

Of 23 iciHHV-6 index cases, 8 mothers and 15 fathers had iciHHV-6. Spontaneous abortion rates in mothers with and mothers without/fathers with iciHHV-6 and mothers in families without iciHHV-6 were 27.6%, 10.3%, and 14.8%, respectively (P = .012). Mothers with iciHHV-6 (odds ratio [OR], 6.41; 95% confidence interval [CI], 1.10-37.4) and maternal age at the most recent pregnancy ≥40 years (OR, 3.91; 95% CI, 1.30-11.8) were associated with 2 or more spontaneous abortions.

CONCLUSIONS

Mothers with iciHHV-6 is a risk factor for spontaneous abortion.

Human Herpesvirus-6 Meningitis in a Premature Infant with Fevers: A Case and Literature Review

Human herpesvirus-6 (HHV-6) is a common virus that can cause nearly universal infection in infancy and early childhood. It typically manifests as an acute febrile illness. We describe a case of a premature infant with congenital hydrocephalus secondary to aqueductal stenosis with a ventriculoperitoneal shunt in place who developed intermittent fevers while she was admitted to the neonatal intensive care unit. She was ultimately diagnosed with acute HHV-6 meningitis. In addition to this report, we present a literature review regarding this virus’s potential modes of transmission and forms of clinical presentation in the neonatal period.

Presence of HHV-6A in Endometrial Epithelial Cells from Women with Primary Unexplained Infertility

To elucidate the roles of human herpesvirus (HHV)-6 primary unexplained infertile women, a prospective randomized study was conducted on a cohort of primary unexplained infertile women and a cohort of control women, with at least one successful pregnancy. HHV-6 DNA was analyzed and the percentage and immune-phenotype of resident endometrial Natural Killer (NK) cells, as the first line of defense towards viral infections, was evaluated in endometrial biopsies. Cytokine levels in uterine flushing samples were analyzed. HHV-6A DNA was found in 43% of endometrial biopsies from primary unexplained infertile women, but not in control women. On the contrary, HHV-6B DNA was absent in endometrial biopsies, but present in PBMCs of both cohorts. Endometrial NK cells presented a different distribution in infertile women with HHV6-A infection compared with infertile women without HHV6-A infection. Notably, we observed a lower percentage of endometrial specific CD56brightCD16- NK cells. We observed an enhanced HHV-6A-specific endometrial NK cell response in HHV-6A positive infertile women, with a marked increase in the number of endometrial NK cells activating towards HHV-6A infected cells. The analysis of uterine flushing samples showed an increase in IL-10 levels and a decrease of IFN-gamma concentrations in infertile women with HHV6-A infection. Our study indicates, for the first time, that HHV-6A infection might be an important factor in female unexplained infertility development, with a possible role in modifying endometrial NK cells immune profile and ability to sustain a successful pregnancy.

Presence of HHV-6 genome in spermatozoa in a context of couples with low fertility: what type of infection?

Human herpesvirus-6 (HHV-6) is a betaherpesvirus whose genome may integrate into human chromosomes. Chromosomally integrated HHV-6 (ciHHV-6) may be transmitted vertically from parents to children. HHV-6 DNA has been detected in semen, but its integrated or extrachromosomal status has not yet been characterised. The aim of this study was to determine the prevalence of HHV-6 DNA and to search for ciHHV-6 forms in spermatozoa purified from semen obtained from subjects explored for low fertility. A total of 184 sperm samples were purified using PureSperm(®) . HHV-6 viral load and species identification were performed by real-time polymerase chain reaction. Of 179 sperm specimens analysed, three were positive for HHV-6 (1.7%). Two samples (1.1%) had viral loads of 680 232 and 2 834 075 copies per million spermatozoa, compatible with loads expected for a ciHHV-6 form. The viral load of the third positive sample (73 684 copies per million spermatozoa) was lower than would be expected for ciHHV-6 infection, implying that the HHV-6 DNA detected in spermatozoa corresponds mainly to ciHHV-6. However, viral DNA may also be detected at a low level that is not in favour of the presence of ciHHV-6. Further studies are necessary to determine the origin of detected viral genomes.

Human herpesvirus-6A/B binds to spermatozoa acrosome and is the most prevalent herpesvirus in semen from sperm donors

An analysis of all known human herpesviruses has not previously been reported on sperm from normal donors. Using an array-based detection method, we determined the cross-sectional frequency of human herpesviruses in semen from 198 Danish sperm donors. Fifty-five of the donors had at least one ejaculate that was positive for one or more human herpesvirus. Of these 27.3% (n = 15) had a double herpesvirus infection. If corrected for the presence of multiple ejaculates from some donors, the adjusted frequency of herpesviruses in semen was 27.2% with HSV-1 in 0.4%; HSV-2 in 0.1%; EBV in 6.3%; HCMV in 2.7%; HHV-6A/B in 13.5%; HHV-7 in 4.2%, whereas none of the samples had detectable VZV or HHV-8. Subsequently, we examined longitudinally data on ejaculates from 11 herpesvirus-positive donors. Serial analyses revealed that a donor who tested positive for herpesvirus at one time point did not necessarily remain positive over time. For the most frequently found herpesvirus, HHV-6A/B, we examined its association with sperm. For HHV-6A/B PCR-positive semen samples, HHV-6A/B could be detected on the sperm by flow cytometry. Conversely, PCR-negative semen samples were negative by flow cytometry. HHV-6B was shown to associate with sperm within minutes in a concentration dependent manner. Confocal microscopy demonstrated that HHV-6B associated with the sperm head, but only to sperm with an intact acrosome. Taken together, our data suggest that HHV-6A/B could be transported to the uterus via binding to the sperm acrosome. Moreover, we find a 10 times higher frequency of HHV-7 in semen from healthy individuals than previously detected. Further research is required to determine the potential risk of using herpesvirus-positive donor semen. Longitudinally analyses of ejaculate series indicate that implementation of quarantine for a donor shown to shed a herpesvirus is not a tenable solution.

Pityriasis rosea: an update with a critical appraisal of its possible herpesviral etiology

Pityriasis rosea is an acute, self-healing exanthem characterized by oval erythematous-squamous lesions of the trunk and limbs, that usually spares face, scalp, palms, and soles. Constitutional symptoms, which have the character of true prodromes; clinical features, which resemble those of the known exanthems; and many epidemiologic data all suggest an infectious origin. A host of infectious agents have been incriminated, but, recently, human herpesvirus 6 and 7 have been extensively studied. The goal of this review is to outline the epidemiologic, clinical, histologic, and ultrastructural features of pityriasis rosea, but mainly to stress its possible human herpesvirus nature. In addition, clues have been added to help the reader to go through the complex subtleties of the virologic investigation.

CCR5 signalling, but not DARC or D6 regulatory, chemokine receptors are targeted by herpesvirus U83A chemokine which delays receptor internalisation via diversion to a caveolin-linked pathway

Background

Herpesviruses have evolved chemokines and chemokine receptors, which modulate the recruitment of human leukocytes during the inflammatory response to infection. Early post-infection, human herpesvirus 6A (HHV-6A) infected cells express the chemokine receptor U51A and chemokine U83A which have complementary effects in subverting the CC-chemokine family thereby controlling anti-viral leukocyte recruitment. Here we show that, to potentiate this activity, the viral chemokine can also avoid clearance by scavenger chemokine receptors, DARC and D6, which normally regulate an inflammatory response. Conversely, U83A delays internalisation of its signalling target receptor CCR5 with diversion to caveolin rich membrane domains. This mechanism can redirect displaced human chemokines to DARC and D6 for clearance of the anti-viral inflammatory response, leaving the viral chemokine unchecked.

Methods

Cell models for competitive binding assays were established using radiolabeled human chemokines and cold U83A on CCR5, DARC or D6 expressing cells. Flow cytometry was used to assess specific chemotaxis of CCR5 bearing cells to U83A, and internalisation of CCR5 specific chemokine CCL4 after stimulation with U83A. Internalisation analyses were supported by confocal microscopy of internalisation and co-localisation of CCR5 with caveosome marker caveolin-1, after virus or human chemokine stimulation.

Results

U83A displaced efficiently human chemokines from CCR5, with a high affinity of 0.01nM, but not from DARC or D6. Signalling via CCR5 resulted in specific chemoattraction of primary human leukocytes bearing CCR5. However, U83A effective binding and signalling to CCR5 resulted in delayed internalisation and recycling up to 2 hours in the absence of continual re-stimulation. This resulted in diversion to a delayed caveolin-linked pathway rather than the rapid clathrin mediated endocytosis previously shown with human chemokines CCL3 or CCL4.

Conclusion

U83A diverts human chemokines from signalling, but not regulatory or scavenger, receptors facilitating their clearance, while occupying signalling receptors at the cell surface. This can enhance virus specific inflammation, facilitating dissemination to replication sensitive leukocytes while evading clearance; this has implications for linked neuro-inflammatory pathologies.

Infection with Parvovirus B19 and Herpes viruses in early pregnancy and risk of second trimester miscarriage or very preterm birth

We investigated whether infections with Parvovirus B19 and Herpes viruses in early pregnancy increase risks of second trimester miscarriage or delivery before 32 gestational weeks. Blood samples taken in early pregnancy were analyzed for Parvovirus B19 or Herpes viruses. Viremia was found in blood samples of 11 (4.7%) women with second trimester miscarriage and 10 (3.7%) women with very preterm birth, compared to 5 (1.7%) women who delivered at term, corresponding to adjusted odds ratios [95% CI] of 3.32 [0.93, 11.8] and 2.21 [0.71, 6.84], respectively. In stratified analyses, Parvovirus B19 viremia was associated with adjusted odds ratios of 3.76 [0.77, 18.3] for second trimester miscarriage and 2.66 [0.64, 11.1] for very preterm birth. Corresponding odds ratios for Human Herpes virus 6 viremia was 2.52 [0.33, 19.5] and 1.08 [0.14, 8.08], respectively. In conclusion, this study lends some support to the hypothesis that women with viremia in early pregnancy may face an increased risk of second trimester miscarriage or very preterm birth. Studies with larger sample sizes are needed.

Prevalence and avidity of human herpesvirus-6 specific IgG antibodies in pregnant women in Hungary

The prevalence, the level and the avidity of human herpesvirus-6 (HHV-6) specific IgG were examined in pregnant women and age-matched female blood donors. The study group consisted of 180 women (age 14-45); 60 women with normal pregnancy, 60 pregnant women with fetuses suspected of having any viral infection and 60 healthy blood donors with no history of pregnancy. Plasma or serum samples were tested for HHV-6 IgG antibodies by an immunofluorescence assay. Ninety-eight percent of blood donors and 97% of 120 pregnant women had IgG antibodies to HHV-6. The rate of seropositivity in women with normal pregnancies and women with fetuses suspected to have viral infection was the same. Pregnant women (n = 120) had significantly lower antibody titer than blood donors. No significant differences were found in the same respect between the two groups of pregnant women. Low avidity of IgG antibodies to HHV-6 was detected in 5% of pregnant women.

Congenital infections with human herpesvirus 6 (HHV6) and human herpesvirus 7 (HHV7)

OBJECTIVE

To examine whether: (1) congenital human herpesvirus 6 (HHV6) and human herpesvirus 7 (HHV7) infections occur; whether (2) their manifestations differ from postnatal infections; and whether (3) HHV6 and HHV7 infections differ despite their close relatedness.

STUDY DESIGN

HHV6 and HHV7 infections acquired congenitally and postnatally in normal children were compared using viral isolation, serology, reverse-transcription polymerase chain reaction (RT-PCR) and nested DNA-PCR for HHV6 variant A (HHV6A), HHV6 variant B (HHV6B), and HHV7.

RESULTS

HHV6 DNA was detected in 57 (1%) of 5638 cord bloods. HHV7 DNA, however, was not detected in 2129 cord bloods. Congenital HHV6 infections differed from postnatal infections, which were acute febrile illnesses. Congenital infections were asymptomatic, 10% demonstrated reactivation at birth, and HHV6 DNA persistence in follow-up blood samples was significantly more frequent. One-third of congenital infections were HHV6A, whereas all postnatal infections were HHV6B.

CONCLUSIONS

Congenital HHV6 infections occurred in 1% of births, similar to the rate for cytomegalovirus infection. Congenital infections were clinically and virologically distinct from postnatal infections. Congenital HHV7 infections, however, were not detected, suggesting considerable differences in transmission and pathogenesis in these closely related beta-herpesviruses.

Congenital infection with human herpesvirus 6 variant B associated with neonatal seizures and poor neurological outcome

Human herpesvirus 6 (HHV 6) has neurotropic and neuroinvasive properties. The virus has been found in the cerebrospinal fluid of many children with aseptic meningoencephalitis. Intrauterine transmission has been documented by HHV 6 DNA detection in cord blood specimens of apparently healthy newborns and in fetuses following spontaneous abortions. A patient is described with early neonatal afebrile seizures resulting from a congenital HHV 6 variant B infection disclosed by repeated detection of viral genome by polymerase chain reaction (PCR) in cerebrospinal fluid in the first days of life. At follow-up, magnetic resonance imaging (MRI) studies disclosed hyperintensities in the periventricular white matter and basal ganglia, associated with cerebral atrophy. Further follow-up at 18 months revealed poor neurological outcome with mild neurodevelopmental retardation, strabismus and hypertonia of legs. This report provides evidence of neurological involvement after HHV 6 vertical transmission, and the association with neurological sequelae.

HHV-6, 7 and their related diseases

Human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7) are relatively recently discovered beta-herpesvirus. They are prevalent in the human population. Primary infection of HHV-6 has been associated with exanthem subitum and febrile illness. Little information is known about the clinical characteristics of primary infection with HHV-7, although some cases of exanthem subitum have been linked to it. HHV-6 has been recently recognized as an opportunistic pathogen in patients with HIV infection and in transplant recipients. The techniques now available to detect these two viruses remain limited, though putative roles for HHV-6 and HHV-7 in several diseases linked to viral infection have been reported. This report reviews the current knowledge of HHV-6 and HHV-7 biology and their pathogenesis.

Human herpesviruses 6 and 7 in cervixes of pregnant women

We looked for human herpesvirus 6 (HHV-6) and HHV-7 genomes in the cervixes of pregnant women in the late stages of their pregnancies. Of 72 samples collected with cervical swabs and amplified by nested PCR, we found that 14 (19.4%) and 2 (2.7%) contained detectable HHV-6 and HHV-7 genomes, respectively. The two samples in which HHV-7 DNA was detected also contained HHV-6 genomes. Hybridization of HHV-6 DNA amplified by PCR with variant-specific probes revealed that all of these DNA samples belonged to variant type B. These results indicated that HHV-6 and/or HHV-7 exists in the cervixes of infected women in late pregnancy and may cause perinatal infection.