Detection of human herpesvirus 7 (HHV-7) DNA in breast milk by polymerase chain reaction and prevalence of HHV-7 antibody in breast-fed and bottle-fed children

Update on human herpesvirus 7 pathogenesis and clinical aspects as a roadmap for future research

Human herpesvirus 7 (HHV-7) is a common virus that is associated with various human diseases including febrile syndromes, dermatological lesions, neurological defects, and transplant complications. Still, HHV-7 remains one of the least studied members of all human betaherpesviruses. In addition, HHV-7-related research is mostly confined to case reports, while in vitro or in vivo studies unraveling basic virology, transmission mechanisms, and viral pathogenesis are sparse. Here, we discuss HHV-7-related literature linking clinical syndromes to the viral life cycle, epidemiology, and viral immunopathogenesis. Based on our review, we propose a hypothetical model of HHV-7 pathogenesis inside its host. Furthermore, we identify important knowledge gaps and recommendations for future research to better understand HHV-7 diseases and improve therapeutic interventions.

Characteristics of HHV-7 meningitis: a systematic review

There are limited data on HHV-7 meningitis and this systematic review used electronic search to gather pieces of evidence regarding its characteristics. Nine articles were included which three were case reports and the rest of the articles were retrospective studies. Altogether, 32 cases were described in the literature that 13 were females and 26 were aged less than 16 years old. The HHV-7 meningitis has been reported in any season, especially in winter. It affected both immunocompetent and immunocompromised individuals and mostly presented with fever and headache, however rash and seizure have also been documented. The CSF analysis in general showed an elevated range of cell count with lymphocytic predominance and normal to slightly elevated protein levels. Thirteen patients did not receive treatment for HHV-7 meningitis and full recovery was gained in the majority of cases after about 10 days. This review summarizes characteristics of HHV-7 meningitis in the literature, and yet epidemiological studies are needed to shed more light which eventually could be helpful for the diagnosis and management of this disease.

Viruses and Human Milk: Transmission or Protection?

Human milk (HM) is considered the best source of nutrition for infant growth and health. This nourishment is unique and changes constantly during lactation to adapt to the physiological needs of the developing infant. It is also recognized as a potential route of transmission of some viral pathogens although the presence of a virus in HM rarely leads to a disease in an infant. This intriguing paradox can be explained by considering the intrinsic antiviral properties of HM. In this comprehensive and schematically presented review, we have described what viruses have been detected in HM so far and what their potential transmission risk through breastfeeding is. We have provided a description of all the antiviral compounds of HM, along with an analysis of their demonstrated and hypothesized mechanisms of action. Finally, we have also analyzed the impact of HM pasteurization and storage methods on the detection and transmission of viruses, and on the antiviral compounds of HM. We have highlighted that there is currently a deep knowledge on the potential transmission of viral pathogens through breastfeeding and on the antiviral properties of HM. The current evidence suggests that, in most cases, it is unnecessarily to deprive an infant of this high-quality nourishment and that the continuation of breastfeeding is in the best interest of the infant and the mother.

Associations between Oral Human Herpesvirus-6 and -7 and Periodontal Conditions in Older Adults

BACKGROUND

The associations between oral human herpesvirus-6 (HHV-6) and HHV-7, periodontal conditions, and lifestyle-related diseases, such as hypertension, diabetes, and dyslipidemia, have not been fully investigated in older adults.

METHODS

Seventy-four older patients who visited Hiroshima University Hospital were enrolled. Tongue swab samples were employed, and a real-time polymerase chain reaction was performed to detect HHV-6 and HHV-7 DNA. Dental plaque accumulation, probing pocket depth, and bleeding on probing (BOP) (i.e., a sign of periodontal inflammation) were examined. The periodontal inflamed surface area (PISA) value (i.e., an indicator of the severity of periodontitis) was also examined.

RESULTS

Of the 74 participants, one participant (1.4%) was HHV-6 DNA-positive and 36 participants (48.6%) were HHV-7 DNA-positive. A significant association between HHV-7 DNA and probing depth was found (p = 0.04). The HHV-7 DNA-positive participants had a higher positive rate of a ≥6-mm periodontal pocket with BOP (25.0%) than the HHV-7 DNA-negative participants (7.9%). Additionally, the HHV-7 DNA-positive participants had a higher PISA value than the HHV-7 DNA-negative participants. However, there was no significant association between HHV-7 and the PISA value (p = 0.82). No significant association was found between HHV-7 and lifestyle-related diseases (p > 0.05).

CONCLUSIONS

Oral HHV-7 infection is associated with a deep periodontal pocket.

Prevalence of human herpesviruses infections in nonmalignant tonsils: The SPLIT study

OBJECTIVE

To assess the prevalence of all known human herpesviruses (HHV) in tonsils of an age-stratified large sample of immunocompetent children and adults.

METHODS

Patients undergoing tonsillectomy for benign indications were recruited in 19 French hospitals. After resection, the entire outer surfaces of right and left half tonsils were extensively brushed. A highly sensitive species-specific multiplex assay was used to detect herpes simplex virus 1 (HSV1), HSV2, Epstein-Barr virus (EBV; types 1 and 2), and human cytomegalovirus (CMV) DNA in 688, as well as varicella zoster virus (VZV), HHV6A, HHV6B, HHV7, and Kaposi's sarcoma-associated herpesvirus (KSHV) DNA in a subset of 440 tonsil brushings.

RESULTS

Overall 85% of tonsil brushing samples were infected with at least one HHV species. HHV7 and EBV were the most prevalent (≈70%), followed by HHV6B (≈50%), HSV1, CMV, VZV (≈2%), and KSHV and HSV2 (<1%), while HHV6A was not detected. EBV prevalence was significantly higher in adults than in children, whereas it was opposite for HHV6B and VZV. No difference in HHV prevalence was observed by sex. In multivariate analysis, EBV detection was associated with age greater than or equal to 15 years (prevalence ratio [PR] = 1.8; 95% confidence interval [CI]: 1.5-2.3) and marginally with tobacco smoking (PR = 1.2; 95% CI: 1.1-1.3).

CONCLUSION

Differing patterns of HHV infection in tonsils in a large age-stratified population were described. This study is by far the largest available and shows that EBV, HHV6B, and HHV7 are commonly detected in the tonsils in both men and women, in contrast to other HHVs.

Transient Oral Human Cytomegalovirus Infections Indicate Inefficient Viral Spread from Very Few Initially Infected Cells

Cytomegalovirus (CMV) is acquired by the oral route in children, and primary infection is associated with abundant mucosal replication, as well as the establishment of latency in myeloid cells that results in lifelong infection. The efficiency of primary CMV infection in humans following oral exposure, however, is unknown. We consistently detected self-limited, low-level oral CMV shedding events, which we termed transient CMV infections, in a prospective birth cohort of 30 highly exposed CMV-uninfected infants. We estimated the likelihood of transient oral CMV infections by comparing their observed frequency to that of established primary infections, characterized by persistent high-level shedding, viremia, and seroconversion. We developed mathematical models of viral dynamics upon initial oral CMV infection and validated them using clinical shedding data. Transient infections comprised 76 to 88% of oral CMV shedding events. For this high percentage of transient infections to occur, we identified two mathematical prerequisites: a very small number of initially infected oral cells (1 to 4) and low viral infectivity (<1.5 new cells infected/cell). These observations indicate that oral CMV infection in infants typically begins with a single virus that spreads inefficiently to neighboring cells. Thus, although the incidence of CMV infection is high during infancy, our data provide a mechanistic framework to explain why multiple CMV exposures are typically required before infection is successfully established. These findings imply that a sufficiently primed immune response could prevent CMV from establishing latent infection in humans and support the achievability of a prophylactic CMV vaccine.IMPORTANCE CMV infects the majority of the world's population and is a major cause of birth defects. Developing a vaccine to prevent CMV infection would be extremely valuable but would be facilitated by a better understanding of how natural human CMV infection is acquired. We studied CMV acquisition in infants and found that infections are usually brief and self-limited and are successfully established relatively rarely. Thus, although most people eventually acquire CMV infection, it usually requires numerous exposures. Our analyses indicate that this is because the virus is surprisingly inefficient, barely replicating well enough to spread to neighboring cells in the mouth. Greater knowledge of why CMV infection usually fails may provide insight into how to prevent it from succeeding.

Update on infections with human herpesviruses 6A, 6B, and 7

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.

Epidemiology and transmission of Kaposi's sarcoma-associated herpesvirus

This review summarizes the current knowledge pertaining to Kaposi sarcoma-associated herpesvirus (KSHV) epidemiology and transmission. Since the identification of KSHV twenty years ago, it is now known to be associated with Kaposi's sarcoma (KS), primary effusion lymphoma, and multicentric Castleman's disease. Many studies have been conducted to understand its epidemiology and pathogenesis and their results clearly show that the worldwide distribution of KSHV is uneven. Some geographical areas, such as sub-Saharan Africa, the Mediterranean region and the Xinjiang region of China, are endemic areas, but Western Europe and United States have a low prevalence in the general population. This makes it imperative to understand the risk factors associated with acquisition of infection. KSHV can be transmitted via sexual contact and non-sexual routes, such as transfusion of contaminated blood and tissues transplants, or via saliva contact. There is now a general consensus that salivary transmission is the main route of transmission, especially in children residing in endemic areas. Therefore, there is a need to better understand the sources of transmission to young children. Additionally, lack of animal models to study transmission, gold standard serological assay and the lack of emphasis on endemic KS research has hampered the efforts to further delineate KSHV transmission in order to design effective prevention strategies.

[Human herpesvirus-6 and human herpesvirus-7 (HHV-6, HHV-7)]

human herpesvirus 6 (HHV-6) is the major causative agent of exanthem subitum which is one of popular diseases in infant, and establishes latent infections in adults of more than 90%. Recently, the encephalitis caused by reactivated- HHV-6 has been shown in patients after transplantation. In addition, the relationship HHV-6 and drug-induced hypersensitivity syndrome has also been reported. human herpesvirus 7 (HHV-7) was isolated from the stimulated-peripheral blood lymphocytes of a healthy individual, and also causes exanthema subitum. Both viruses are related viruses which belong to betaherpesvirus subfamily, and replicate and produce progeny viruses in T cells.

Human herpesvirus 7

Az emberi 7-es herpeszvírus 1990 óta ismert, közeli rokonságban áll a 6-os herpeszvírussal, annak B változatával. Csak emberi sejtekben szaporodik, receptora a CD4 molekula. A fertőzött sejtek egy részében élethossziglan lappang, gyakran reaktiválódik és a nyálban tünetmentesen ürül. Gyermekek egy része 3–4 éves korára tünetmentesen fertőződik, de minden életkorban találhatók szeronegatív egyének, akik fogékonyak a fertőzés iránt. Gyermekekben ritkán exanthema subitum, múló lázas-görcsös állapotok, fiatal felnőttekben rózsahámlás, immunszuppresszált egyénekben a reaktiválódott 6-os B herpeszvírussal és cytomegalovirussal egyetemben halálos szövődmények alakulhatnak ki. Egyéb vírusokat is aktiválhat más kórképekben. A vírus patogenezisében a legfontosabb, hogy megváltozik a fertőzött lymphocytákból kiáramló citokinek és növekedési faktorok egyensúlya, amely láncreakcióként hat az immunrendszer és egyéb szervek sejtjeire. A vírusellenes antitestek kimutatása kereskedelmi forgalomban kapható készletekkel (immunfluoreszcencia, ELISA, immunoblot), a nukleinsav kimutatása fészkes polimeráz láncreakcióval lehetséges. A fertőzés következtében kialakult betegségek legtöbbje nem igényel kezelést, de súlyos szövődmények esetén ganciclovir és származékai, valamint foscarnet és cidofovir alkalmazható.

Cytomegalovirus and Epstein-Barr virus in breast milk are associated with HIV-1 shedding but not with mastitis

BACKGROUND

Breast milk HIV-1 load is associated with clinical and subclinical mastitis, and both milk viral load and mastitis are associated with increased mother-to-child-transmission of HIV-1 through breastfeeding. Bacterial infections may cause clinical mastitis, but whether other copathogens common in HIV-1 infection are associated with subclinical mastitis or HIV-1 shedding is unknown.

DESIGN

A cross-sectional study of HIV-1-infected breastfeeding women in Zimbabwe was performed to examine the relationship between a wide range of breast coinfections, mastitis, and HIV-1 shedding.

METHODS

Breast milk was cultured for bacteria and fungi and tested by PCR for mycobacteria, mycoplasmas, human herpesvirus (HHV)-6, HHV-7, HHV-8, cytomegalovirus, Epstein-Barr virus, and HIV-1 RNA and DNA. Symptoms of clinical mastitis were documented and subclinical mastitis was identified by breast milk sodium concentration (Na) and leukocyte counts.

RESULTS

Coinfections of milk were not associated with clinical or subclinical mastitis in the 217 women studied. Detection of HIV-1 RNA, but not DNA, in breast milk was associated with cytomegalovirus concentration (odds ratio = 1.8, P = 0.002) and detection of Epstein-Barr virus (odds ratio = 3.8, P = 0.0003) but not other coinfections in multivariate analysis.

CONCLUSION

Coinfection of breast milk with bacteria, fungi, or herpes viruses was not associated with mastitis. The associations between shedding of cytomegalovirus and Epstein-Barr virus with HIV-1 in milk suggest a local interaction between herpes virus infection and HIV-1 independent of mastitis. Cytomegalovirus and Epstein-Barr virus infections may impact HIV-1 shedding in breast milk and the risk of MTCT.

Human herpesviruses 6 and 7 and central nervous system infection in children

Human herpesviruses 6 and 7 were infrequently found in cerebrospinal fluid of children with central nervous system infection.

The role and frequency of human herpesviruses (HHV)-6 and -7 in central nervous system (CNS) diseases of children are unclear. Cerebrospinal fluid samples from 245 pediatric patients (median age 43 days), submitted for evaluations of possible sepsis or of neurologic symptoms, were tested for HHV-6 and HHV-7 DNA by polymerase chain reaction. HHV-6 DNA was found in 3 of 245 samples, and HHV-7 was found in 0 of 245 samples. The three patients with HHV-6 DNA were <2 months of age. HHV-6 was likely pathogenic in two patients with meningitis who lacked evidence of another microbiologic cause. HHV-6 and HHV-7 are uncommon causes of CNS infection in children. HHV-6 may occasionally cause meningitis in young infants.

Human herpesvirus 6 (HHV-6) is transmitted from parent to child in an integrated form and characterization of cases with chromosomally integrated HHV-6 DNA

We obtained 7,566 peripheral blood mononuclear cell (PBMC) samples from 2,332 individuals and screened them for human herpesvirus infection. We identified five individuals who persistently harbored high copy numbers of human herpesvirus 6 (HHV-6) DNA in their PBMCs. HHV-6 DNA was also detected in other somatic tissues of these individuals. Five additional cases were identified among their family members. For two of these families, chromosomally integrated HHV-6 DNA (CIHHV-6) was detected in the PBMCs by fluorescence in situ hybridization. The prevalence of CIHHV-6 among all the subjects was 0.21%. The HHV-6 DNA was variant B in four families and variant A in one family. Antibodies to immediate early antigen and glycoprotein B were detected in 57 and 14% of individuals with CIHHV-6 and in 0 and 60% of healthy volunteers without CIHHV-6, respectively. HHV-6 could not be isolated from PBMCs with CIHHV-6. These cases shared no clinical features, and included three healthy individuals. Our data suggest that CIHHV-6 is rare but detectable in the general population and that hereditary transmission is one of the routes of HHV-6 transmission.

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.

Human herpesvirus 7 in dermatology: what role does it play?

Human herpesvirus 7 (HHV-7) was discovered in 1989 as a new member of the beta-herpesvirus subfamily. Primary infection occurs early in life and manifests as exanthema subitum, or other febrile illnesses mimicking measles and rubella. Thus, HHV-7 has to be considered as a causative agent in a variety of macular-papular rashes in children. In addition, HHV-7 was found in some cases of other inflammatory skin disorders, such as psoriasis. There are controversial data on the detection of HHV-7 in pityriasis rosea, but so far there is not enough evidence for a pathogenetic association of HHV-7 with this exanthematic skin disease. Although HHV-7 can be found in some cases of Hodgkin's disease, there are no data supporting a direct causative role in this lymphoma type nor in other nodal or primary cutaneous lymphomas. In various epidemiologic forms of Kaposi's sarcoma, infection of monocytic cells with HHV-7 was demonstrated, which may indirectly influence tumor biology. In the context of immunosuppression, HHV-7 has recently been identified as an emerging pathogen in transplant recipients and may exacerbate graft rejection in renal transplant recipients. The ability of HHV-7 to induce cytokine production in infected cells could make HHV-7 an important pathogenetic co-factor in inflammatory and neoplastic disorders. Moreover, the restricted cellular tropism of HHV-7 may render this virus an interesting vector for gene therapy. Thirteen years after the discovery of HHV-7, there has been considerable progress in characterizing its genetic structure, virus-induced effects on infected host cells and in the development of diagnostic tools. Nevertheless, the role of HHV-7 in various skin diseases and the clinical manifestations of reactivation of HHV-7 infection have still to be defined.

Human herpesvirus 7 is latent in gastric mucosa

Chronic gastritis is associated frequently with persistent infection by Helicobacter pylori. However, not all patients with chronic gastritis have evidence of H. pylori infection, suggesting that other factors might contribute to the development of gastritis. The present study was undertaken to evaluate a possible etiologic role of human herpesvirus 7 (HHV-7). HHV-7 DNA was detected in about 80% of gastric biopsies, both in healthy mucosa from individuals without evidence of inflammation and in biopsies from patients with histologically confirmed chronic gastric inflammation. HHV-7 was present also in H. pylori negative samples, was associated specifically with gastric tissue and not with residual blood within the mucosa, and was present with high viral loads. HHV-7 DNA persisted in several patients also after remission of gastric inflammation and the viral presence did not correlate with specific symptoms. Analysis by RT-PCR showed that HHV-7 is transcriptionally inactive in chronic gastritis lesions. These observations show that gastric tissue represents a site of HHV-7 latent infection and a potential reservoir for viral reactivation.

Human herpesvirus 7

Human herpesvirus 7, reported in 1990 is a lymphotropic member of the betaherpesvirus subfamily of herpesviruses. The virus is highly seroprevalent, primary infection usually occurs during childhood, and it has been associated with cases of exanthem subitum, pityriasis rosea, neurological manifestations and transplant complications. The latter two may warrant antiviral intervention, in vitro studies have shown that HHV-7 is susceptible to several nucleoside phosphonate compounds. In vitro, the virus has approximately a 5 day growth cycle in cultured lymphocytes; in vivo, latency is established in peripheral blood T-cells and a persistent infection is established in salivary gland tissue from which infectious virus is constitutively shed in saliva. The HHV-7 genome is approximately 145 kb and encodes at least 84 different proteins. Studies characterising HHV-7 gene products and the required interactions between viral and cellular genes necessary for virus replication, persistence and latency are in their infancy. HHV-7 infection has a variety of effects on host cells including upregulation of interleukin 15 and down-modulation of the cell surface molecule CD4; the latter serves as the cellular membrane receptor for HHV-7. Since HIV also infects T-cells via the CD4 molecule, the interactions of these viruses within T-cells during the course of AIDS are important areas of investigation.

The epidemiology and pathogenesis of infections caused by the high numbered human herpesviruses in children: HHV-6, HHV-7 and HHV-8

Human herpesvirus 6 may be transmitted from saliva to infants, but other routes of transmission, such as organ and bone marrow transplantation, have also been reported. Intrauterine infection has also been suggested. Although the clinical symptoms during the primary infection in children are mild, human herpesvirus 6 may have neurotropic properties and be involved in the pathogenesis of febrile seizures in infants. The clinical symptoms caused by human herpesvirus 7 are not yet clear, but reports have described neurological symptoms. Human herpesvirus 8 has been identified from Kaposi's sarcoma tissue using molecular procedures. Serological study shows that human herpesvirus 8 is not so common in society and the mode of transmission is still unclear. Several routes of infection have, however, been considered, including sexual transmission.