Replication properties and immunomodulatory effects of human cytomegalovirus infection impact the clinical presentation in congenital patients: A case series.

BACKGROUND: Human cytomegalovirus (HCMV) is the leading cause of congenital infections resulting in severe morbidity and mortality among newborns worldwide. Although both the host's and the virus' genetic backgrounds contribute to the outcome of infections, significant gaps remain in our understanding of the exact mechanisms that determine disease severity. OBJECTIVES: In this study, we sought to identify a correlation between the virological features of different HCMV strains with the clinical and pathological features of congenitally infected newborns, therefore proposing new possible prognostic factors. STUDY DESIGN: This short communication presents five newborns with congenital cytomegalovirus infection, whose clinical phenotype during fetal, neonatal, and follow-up periods is correlated with in-vitro growth properties, immunomodulatory abilities and genome variability of HCMV strains isolated from organic samples (urine) of the patients. RESULTS: The five patients described in this short communication displayed a heterogeneous clinical phenotype and different virus replication properties, immunomodulatory abilities, and genetic polymorphisms. Interestingly, we observed that an attenuate viral replication in-vitro influences the immunomodulatory abilities of HCMV, leading to more severe congenital infections and long-term sequelae. Conversely, infection with viruses characterized by aggressive replicative behavior in-vitro resulted in asymptomatic patients' phenotypes. CONCLUSIONS: Overall, this case series suggests the hypothesis that genetic variability and differences in the replicative behavior of HCMV strains result in clinical phenotypes of different severity, most likely due to different immunomodulatory properties of the virus.

Genetic Variability of Human Cytomegalovirus Clinical Isolates Correlates With Altered Expression of Natural Killer Cell-Activating Ligands and IFN-γ.

Human cytomegalovirus (HCMV) infection often leads to systemic disease in immunodeficient patients and congenitally infected children. Despite its clinical significance, the exact mechanisms contributing to HCMV pathogenesis and clinical outcomes have yet to be determined. One of such mechanisms involves HCMV-mediated NK cell immune response, which favors viral immune evasion by hindering NK cell-mediated cytolysis. This process appears to be dependent on the extent of HCMV genetic variation as high levels of variability in viral genes involved in immune escape have an impact on viral pathogenesis. However, the link between viral genome variations and their functional effects has so far remained elusive. Thus, here we sought to determine whether inter-host genetic variability of HCMV influences its ability to modulate NK cell responses to infection. For this purpose, five HCMV clinical isolates from a previously characterized cohort of pediatric patients with confirmed HCMV congenital infection were evaluated by next-generation sequencing (NGS) for genetic polymorphisms, phylogenetic relationships, and multiple-strain infection. We report variable levels of genetic characteristics among the selected clinical strains, with moderate variations in genome regions associated with modulation of NK cell functions. Remarkably, we show that different HCMV clinical strains differentially modulate the expression of several ligands for the NK cell-activating receptors NKG2D, DNAM-1/CD226, and NKp30. Specifically, the DNAM-1/CD226 ligand PVR/CD155 appears to be predominantly upregulated by fast-replicating ("aggressive") HCMV isolates. On the other hand, the NGK2D ligands ULBP2/5/6 are downregulated regardless of the strain used, while other NK cell ligands (i.e., MICA, MICB, ULBP3, Nectin-2/CD112, and B7-H6) are not significantly modulated. Furthermore, we show that IFN-γ; production by NK cells co-cultured with HCMV-infected fibroblasts is directly proportional to the aggressiveness of the HCMV clinical isolates employed. Interestingly, loss of NK cell-modulating genes directed against NK cell ligands appears to be a common feature among the "aggressive" HCMV strains, which also share several gene variants across their genomes. Overall, even though further studies based on a higher number of patients would offer a more definitive scenario, our findings provide novel mechanistic insights into the impact of HCMV genetic variability on NK cell-mediated immune responses.

Risk of Symptomatic Infection after Non-Primary Congenital Cytomegalovirus Infection.

Cytomegalovirus (CMV) is the leading cause of congenital infection. Its occurrence is phenotypically heterogeneous. The type of maternal infection, primary or non-primary, is an important factor related to the symptomatic disease, the primary infection was long considered the only cause of severe neonatal disease. We aimed to analyze the association of primary and non-primary infection with pathological outcomes in infants and with long-term sequelae at follow-up. This was a monocentric retrospective observational study on a population of 91 infants diagnosed with a CMV infection at the Neonatal Care Unit of Neonatology at the Sant'Anna Hospital of Turin during the period of June 2005 to December 2018. Infants underwent clinical, laboratory, and neuroradiological evaluations at birth. Subsequently, the patients were monitored in an auxological, neurodevelopment, and audiological follow-up. Regarding primary vs. non-primary infection, we found a higher percentage of incidence of symptomatic and neurological localized infection, as well as long-term sequelae in the latter. However, no significant difference between the two populations was found. We underline the possibility of re-infection in previously immunized mothers (non-primary infection) with unfavorable neonatal and long-term outcomes.

Biological relevance of Cytomegalovirus genetic variability in congenitally and postnatally infected children.

BACKGROUND: Human cytomegalovirus (HCMV) is the leading cause of congenital infections resulting in severe morbidity and mortality among infected children. Although the virus is highly polymorphic, particularly in genes contributing to immune evasion, the mechanisms underlying its genetic variability and pathogenicity are only partially understood. OBJECTIVES: We aimed to characterize different HCMV clinical strains isolated from 21 congenitally- or postnatally-infected children for in vitro growth properties and genetic polymorphisms. STUDY DESIGN: The growth of various HCMV isolates was analyzed in different cell culture models. Genetic polymorphism was assessed by genetic and phylogenetic analysis of viral genes involved in virulence (UL144, US28, and UL18), latency (UL133-138), or drug resistance (UL54 and UL97). RESULTS: Here, we report a high degree of genetic and phenotypic diversity in distinct HCMV clinical isolates, as shown by their in vitro growth properties. In particular, HCMV isolates displayed the highest degree of genetic variability in the UL144 gene, where we were able to define four distinct genotypes within the cohort based on UL144 heterogeneity. Lastly, among all isolates we were able to identify 36 mutations in UL54 and 2 in UL97. CONCLUSIONS: Our findings indicate that surprisingly high levels of genetic HCMV variability correlate with a high degree of phenotypic polymorphism, which in turn might differentially influence the growth, fitness, and drug susceptibility of HCMV.

Congenital toxoplasmosis: assessment of risk to newborns in confirmed and uncertain maternal infection.

UNLABELLED: We identified 205 newborns at risk of congenital infection based on their mothers' immunological status during pregnancy, using the criteria established by the European Research Network on Congenital Toxoplasmosis to define the likelihood of infection in pregnant women. Of the 205 newborns, 60 (29.2%) were born to mothers with documented seroconversion, 49 (23.9%) to mothers with probable infection, 60 (29.2%) to mothers with possible infection, and 36 (17.6%) to mothers who were unlikely to be infected. Infection was transmitted to the child in 13 out of 60 cases (21.6%) of seroconversion, in 2 out of 49 (4.1%) cases of probable infections and in none of the possible and unlikely cases. The results were further analysed considering only the 109 newborns of mothers with confirmed and probable infection; in this group, toxoplasmosis was not transmitted to any of the 45 newborns of mothers infected in the first trimester of pregnancy, whereas it was transmitted to 5 out of 29 (17.2%) cases of seroconversion and 2 out of 12 (16.6%) with probable infection in the second trimester, and to 8 out of 23 (34.8%) with confirmed infection in the third trimester (no probable infections were dated in the third trimester). Among the newborns of mothers with seroconversion, the risk of symptomatic infection was 10.4% in the second trimester and 8.7% in the third trimester. CONCLUSION: the authors have quantified the risk of transmission of toxoplasmosis infection, not only in cases of seroconversion, as reported by others, but also in infections defined as probable or possible based on presence of IgM and/or IgA and with medium-high IgG levels. Probable infections in the second trimester of pregnancy carries the same risk of transmission as seroconversions and pregnant women and their newborns in these cases should undergo the same diagnostic and therapeutic approach. It is suggested that newborns of mothers with certain and probable infection must be carefully observed and undergo clinical and serological testing to identify and treat the infection as soon as possible. In the case of possible or unlikely maternal infection, serological testing at longer intervals is nevertheless advisable without the need for treatment.