Human Cytomegalovirus Genome Diversity in Longitudinally Collected Breast Milk Samples

Bidirectional transfer of human cytomegalovirus strains in donor and recipient seropositive lung transplant patients

Donor and recipient human cytomegalovirus (HCMV) seropositive (D+R+) lung transplant recipients (LTRs) often harbor multiple strains of HCMV, likely due to transmitted donor (D) strains and reactivated recipient (R) strains. To date, the extent and timely occurrence of each likely source in shaping the post-transplantation (post-Tx) strain population is unknown. Here, we deciphered the D and R origin of the post-Tx HCMV strain composition in blood, bronchoalveolar lavage (BAL), and CD45+ BAL cell subsets. We investigated either D and/or R formalin-fixed paraffin-embedded blocks or fresh D lung tissue from four D+R+ LTRs obtained before transplantation. HCMV strains were characterized by short amplicon deep sequencing. In two LTRs, we show that the transplanted lung is reseeded by R strains within the first 6 months after transplantation, likely by infiltrating CD14+ CD163+/- alveolar macrophages. In three LTRs, we demonstrate both rapid D-strain dissemination and persistence in the transplanted lung for >1 year post-Tx. Broad inter-host diversity contrasts with intra-host genotype sequence stability upon transmission, during follow-up and across compartments. In D+R+ LTRs, HCMV strains of both, D and R origin can emerge first and dominate long-term in subsequent episodes of infection, indicating replication of both sources despite pre-existing immunity.

Cellular Transformation by Human Cytomegalovirus

Epstein-Barr virus (EBV), Kaposi sarcoma human virus (KSHV), human papillomavirus (HPV), hepatitis B and C viruses (HBV, HCV), human T-lymphotropic virus-1 (HTLV-1), and Merkel cell polyomavirus (MCPyV) are the seven human oncoviruses reported so far. While traditionally viewed as a benign virus causing mild symptoms in healthy individuals, human cytomegalovirus (HCMV) has been recently implicated in the pathogenesis of various cancers, spanning a wide range of tissue types and malignancies. This perspective article defines the biological criteria that characterize the oncogenic role of HCMV and based on new findings underlines a critical role for HCMV in cellular transformation and modeling the tumor microenvironment as already reported for the other human oncoviruses.

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.

Human Cytomegalovirus in breast milk is associated with milk composition, the infant gut microbiome, and infant growth

Human cytomegalovirus (CMV) is a highly prevalent herpesvirus that is often transmitted to the neonate via breast milk. Postnatal CMV transmission can have negative health consequences for preterm and immunocompromised infants, but any effects on healthy term infants are thought to be benign. Furthermore, the impact of CMV on the composition of the hundreds of bioactive factors in human milk has not been tested. Here, we utilize a cohort of exclusively breastfeeding full term mother-infant pairs to test for differences in the milk transcriptome and metabolome associated with CMV, and the impact of CMV in breast milk on the infant gut microbiome and infant growth. We find upregulation of the indoleamine 2,3- dioxygenase (IDO) tryptophan-to-kynurenine metabolic pathway in CMV+ milk samples, and that CMV+ milk is associated with decreased Bifidobacterium in the infant gut. Our data indicate a complex relationship between milk CMV, milk kynurenine, and infant growth; with kynurenine positively correlated, and CMV viral load negatively correlated, with infant weight-for-length at 1 month of age. These results suggest CMV transmission, CMV-related changes in milk composition, or both may be modulators of full term infant development.

[Effect of breastfeeding on immune function in infants with human cytomegalovirus infection]

OBJECTIVES

To study the effect of breastfeeding on immune function in infants with human cytomegalovirus (HCMV) infection.

METHODS

A retrospective analysis was performed on the medical data of 135 infants with HCMV infection who were admitted to Children's Hospital Affiliated to Zhengzhou University from January 2021 to May 2022, and all these infants received breastfeeding. According to the results of breast milk HCMV-DNA testing, the infants were divided into two groups: breast milk HCMV positive (n=78) and breast milk HCMV negative (n=57). According to the median breast milk HCMV-DNA load, the infants in the breast milk HCMV positive group were further divided into two subgroups: high viral load and low viral load (n=39 each). Related indicators were compared between the breast milk positive and negative HCMV groups and between the breast milk high viral load and low viral load subgroups, including the percentages of peripheral blood lymphocyte subsets (CD3⁺ T cells, CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, and CD19⁺ B cells), CD4⁺/CD8⁺ ratio, IgG, IgM, IgA, and urine HCMV-DNA load.

RESULTS

There were no significant differences in the percentages of CD3⁺ T cells, CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, and CD19⁺ B cells, CD4⁺/CD8⁺ ratio, IgG, IgM, IgA, and urine HCMV-DNA load between the breast milk HCMV positive and HCMV negative groups, as well as between the breast milk high viral load and low viral load subgroups (P>0.05).

CONCLUSIONS

Breastfeeding with HCMV does not affect the immune function of infants with HCMV infection.

High-Risk Oncogenic Human Cytomegalovirus

Human cytomegalovirus (HCMV) is a herpesvirus that infects between 40% and 95% of the population worldwide, usually without symptoms. The host immune response keeps the virus in a latent stage, although HCMV can reactivate in an inflammatory context, which could result in sequential lytic/latent viral cycles during the lifetime and thereby participate in HCMV genomic diversity in humans. The high level of HCMV intra-host genomic variability could participate in the oncomodulatory role of HCMV where the virus will favor the development and spread of cancerous cells. Recently, an oncogenic role of HCMV has been highlighted in which the virus will directly transform primary cells; such HCMV strains are named high-risk (HR) HCMV strains. In light of these new findings, this review defines the criteria that characterize HR-HCMV strains and their molecular as well as the phenotypic impact on the infected cell and its tumor microenvironment.

Human cytomegalovirus strain diversity and dynamics reveal the donor lung as a major contributor after transplantation

Mixed human cytomegalovirus (HCMV) strain infections are frequent in lung transplant recipients (LTRs). To date, the influence of the donor (D) and recipient (R) HCMV serostatus on intra-host HCMV strain composition and viral population dynamics after transplantation is only poorly understood. Here, we investigated ten pre-transplant lungs from HCMV-seropositive donors and 163 sequential HCMV-DNA-positive plasma and bronchoalveolar lavage samples from fifty LTRs with multiviremic episodes post-transplantation. The study cohort included D+R+ (38 per cent), D+R- (36 per cent), and D-R+ (26 per cent) patients. All samples were subjected to quantitative genotyping by short amplicon deep sequencing, and twenty-four of them were additionally PacBio long-read sequenced for genotype linkages. We find that D+R+ patients show a significantly elevated intra-host strain diversity compared to D+R- and D-R+ patients (P = 0.0089). Both D+ patient groups display significantly higher viral population dynamics than D- patients (P = 0.0061). Five out of ten pre-transplant donor lungs were HCMV DNA positive, whereof three multiple HCMV strains were detected, indicating that multi-strain transmission via lung transplantation is likely. Using long reads, we show that intra-host haplotypes can share distinctly linked genotypes, which limits overall intra-host diversity in mixed infections. Together, our findings demonstrate donor-derived strains as the main source of increased HCMV strain diversity and dynamics post-transplantation. These results foster strategies to mitigate the potential transmission of the donor strain reservoir to the allograft, such as ex vivo delivery of HCMV-selective immunotoxins prior to transplantation to reduce latent HCMV.

Tumors and Cytomegalovirus: An Intimate Interplay

Human cytomegalovirus (HCMV) is a herpesvirus that alternates lytic and latent infection, infecting between 40 and 95% of the population worldwide, usually without symptoms. During its lytic cycle, HCMV can result in fever, asthenia, and, in some cases, can lead to severe symptoms such as hepatitis, pneumonitis, meningitis, retinitis, and severe cytomegalovirus disease, especially in immunocompromised individuals. Usually, the host immune response keeps the virus in a latent stage, although HCMV can reactivate in an inflammatory context, which could result in sequential lytic/latent viral cycles during the lifetime and thereby participate in the HCMV genomic diversity in humans and the high level of HCMV intrahost genomic variability. The oncomodulatory role of HCMV has been reported, where the virus will favor the development and spread of cancerous cells. Recently, an oncogenic role of HCMV has been highlighted in which the virus will directly transform primary cells and might therefore be defined as the eighth human oncovirus. In light of these new findings, it is critical to understand the role of the immune landscape, including the tumor microenvironment present in HCMV-harboring tumors. Finally, the oncomodulatory/oncogenic potential of HCMV could lead to the development of novel adapted therapeutic approaches against HCMV, especially since immunotherapy has revolutionized cancer therapeutic strategies and new therapeutic approaches are actively needed, particularly to fight tumors of poor prognosis.

Clinical, Virologic and Immunologic Correlates of Breast Milk Acquired Cytomegalovirus (CMV) Infections in Very Low Birth Weight (VLBW) Infants in a Newborn Intensive Care Unit (NICU) Setting

Cytomegalovirus (CMV) infections acquired by very-low-birthweight (VLBW) infants are incompletely characterized. To examine CMV transmission in VLBW infants, we evaluated maternal DNAlactia, infant DNAemia, and presence of clinical disease in a blinded study in VLBW infants in our newborn intensive care unit (NICU). To examine these issues, 200 VLBW infants were enrolled in a surveillance study, with weekly breast milk and infant whole blood samples collected, as available. Virologic (breast milk and infant whole blood real time PCR) and immunologic (IgG, IgM, and IgG avidity) correlates were evaluated. A chart review examined whether infants had symptoms compatible with CMV disease. DNAlactia was identified in 65/150 (43%) of lactating mothers. Nine CMV infections were identified in 9/75 CMV-exposed infants (12% of exposed infants). A higher median breast milk viral load (DNAlactia) correlated with an increased likelihood of DNAemia (p = 0.05). Despite potential symptoms compatible with CMV infection, clinicians had not considered the diagnosis of CMV in 6/9 cases (66%). All of these infants had chronic lung disease at discharge. There was no correlation between IgG antibody titer or IgG avidity index and the likelihood of transmission or CMV disease. In conclusion, in VLBW infants receiving milk from seropositive mothers, CMV infections are commonly acquired, and are frequently unrecognized. Future studies are needed to determine whether routine surveillance for CMV of either breast milk or infant plasma is beneficial in preventing or recognizing infection.

Human cytomegalovirus multiple-strain infections and viral population diversity in haematopoietic stem cell transplant recipients analysed by high-throughput sequencing

Human cytomegalovirus (HCMV) is an important opportunistic pathogen in allogeneic haematopoietic stem cell transplant (HSCT) recipients. High-throughput sequencing of target-enriched libraries was performed to characterise the diversity of HCMV strains present in this high-risk group. Forty-four HCMV-DNA-positive plasma specimens (median viral input load 321 IU per library) collected at defined time points from 23 HSCT recipients within 80 days of transplantation were sequenced. The genotype distribution for 12 hypervariable HCMV genes and the number of HCMV strains present (i.e. single- vs. multiple-strain infection) were determined for 29 samples from 16 recipients. Multiple-strain infection was observed in seven of these 16 recipients, and five of these seven recipients had the donor (D)/recipient (R) HCMV-serostatus combination D + R + . A very broad range of genotypes was detected, with an intrahost composition that was generally stable over time. Multiple-strain infection was not associated with particular virological or clinical features, such as altered levels or duration of antigenaemia, development of acute graft-versus-host disease or increased mortality. In conclusion, despite relatively low viral plasma loads, a high frequency of multiple-strain HCMV infection and a high strain complexity were demonstrated in systematically collected clinical samples from this cohort early after HSCT. However, robust evaluation of the pathogenic role of intrahost viral diversity and multiple-strain infection will require studies enrolling larger numbers of recipients.