Heterogeneous pathways of maternal-fetal transmission of human viruses (review)

Maternal human papillomavirus infection and the risk of congenital malformations: A nationwide population-based cohort study

Previous research has explored theories regarding the vertical transmission of human papillomavirus (HPV) infection and its association with adverse pregnancy and perinatal outcomes. However, the impact of maternal HPV infection on congenital anomalies (CAs) in offspring remains relatively understudied. We conducted a population-based cohort study linking the Taiwan Birth Registry, Taiwan Death Registry, and National Health Insurance Research Database, in which newborns born in Taiwan between 2009 and 2015 were included. We established a maternal HPV infection cohort comprising 37 807 newborns and matched them with a comparison group of 151 228 newborns at a 1:4 ratio based on index year, age, and sex. The study examined a composite outcome and subgroups of different types of congenital malformations. Differences in cumulative incidence of CAs were assessed using Kaplan-Meier curves and log-rank tests. Adjusted hazard ratios (aHRs) were estimated using Cox proportional hazard regressions. No significant association was found between HPV infection and the broad spectrum of CAs (aHR: 1.04, 95% confidence interval [CI]: 0.98-1.10; log-rank test p = 0.14). However, we observed a 19% increased risk of musculoskeletal CAs in the maternal HPV infection group (aHR: 1.19; 95% CI: 1.05-1.34) compared to those without maternal HPV exposure. Other factors, including the type of HPV (aHR: 0.65; 95% CI: 0.16-2.63), the timing of exposure (during or before pregnancy), and maternal age (aHR for <30 years: 1.02, 95% CI: 0.94-1.1; aHR for 30-39 years: 1.05, 95% CI: 0.99-1.11; aHR for ≥40 years: 0.88, 95% CI: 0.67-1.17), did not significantly affect the risk for any CA. In conclusion, gestation detection of HPV infection was associated with musculoskeletal CAs but not other major CAs. Prospective studies are warranted to elucidate the necessity of prenatal screening in populations at risk.

Human papillomavirus in cancer: Infection, disease transmission, and progress in vaccines

Human papillomaviruses (HPVs) infect epithelial cells of human beings, and their replication cycle is associated with epithelial differentiation. More than 200 genotypes of HPVs were identified, and each of these HPVs shows distinct specificity for tissues and infection. HPV infection was involved in the development of lesions on the feet, genital warts and hands. The evidence of HPV infection revealed the role of HPVs in neck and head squamous cell carcinoma, esophageal cancer, cervical cancer, head and neck cancer, brain and lung tumours. The independent traditional risk factors, various clinical outcomes, and increased prevalence among certain populations and geographical regions have led increasing interest in HPV infection. The mode of HPVs transmission remains unclear. Moreover, in recent years, vertical transmission of HPVs was reported. This review concludes present knowledge about HPV infection, virulence strains, clinical significance of HPVs, and mode of transmission, and vaccination strategies.

Human papillomavirus (HPV) in pregnancy - An update

Human papilloma viruses (HPV) are small epitheliotropic DNA viruses, of which there are 200 genotypes, 40 of which are known to cause genital infections and are also oncogenic. HPV is the most common sexually transmitted infection. Clinical features vary from asymptomatic (identified at routine cervical cancer screening) to large lesions on the vulva, vagina, cervix and some extragenital sites. Its prevalence in pregnancy varies from 5.5% to 65% depending on age, geography and gestational age (increasing with gestational age). Infection in pregnancy has been associated with adverse outcomes such as spontaneous miscarriage, preterm birth, placental abnormalities and fetal growth restriction. However, the evidence for these adverse outcomes is varied. Besides being oncogenic (and thus associated with cancer of the cervix in pregnancy), vertical transmission to the fetus/neonate can cause neonatal infections, especially juvenile-onset recurrent oral and respiratory papillomatosis (JORRP). Where there are very large lesions on the vulva, delivery may be obstructed. Diagnosis in pregnancy is mainly by viral PCR or from the clinical appearance of the characteristic lesions on the vulva. Treatment is local by either surgical or laser excision or application of trichloroacetic acid. Podophyllin/podophyllotoxin is contraindicated in pregnancy. HPV Infection is not an indication for caesarean delivery as this has not been shown to prevent vertical transmission. For those diagnosed at routine cervical cancer screening, management should follow guidelines for cervical cancer screening in pregnancy. Vaccination is currently not recommended for pregnant women, although studies on those inadvertently vaccinated in pregnancy have not shown any adverse effects on either the fetus or mother.

The presence of human papillomavirus (HPV) in placenta and/or cord blood might result in Th2 polarization

The purpose of this study was to evaluate if an early exposure to human papillomavirus (HPV) during the prenatal period or infancy could result in HPV16-specific T helper (Th) responses resembling those of adults with HPV-induced lesions. We tested HPV16-specific cell-mediated immunity (CMI) in children born with HPV-positive umbilical cord blood and/or placenta or having persistent oral HPV infection and in constantly oral HPV-negative controls. Peripheral blood mononuclear cells from 33 children from the Finnish HPV Family Study cohort (mean age 14.7 years) were stimulated with peptide pools covering the amino acid sequence of the HPV16 E2, E6, and E7 proteins. Lymphocyte proliferation, secretion of cytokines (IFN-γ, TNF-α, IL-2, IL-4, IL-5, IL-10, IL-17A), and the frequency of Foxp3+ regulatory T-cells were determined in relation to the HPV DNA status during a 14-year follow-up. 73.6% of cases and 85.7% of controls responded against HPV16 E2, while reactivity against E6 was found in 10.5 and 35.7%, respectively. The proliferative response against E6 and E7 was more frequent in controls than in cases (p = 0.047). No HPV16-specific CMI response or antibodies were detected in two children with persistent oral HPV16. The profiles of induced cytokines indicated higher levels of IL-5, IL-10, and IL-17A in children with HPV DNA in placenta and/or cord blood than in other children. HPV16-specific CMI is common in HPV DNA-negative children. The cytokine profile in children infected with HPV16 during early life suggests that the viral dose and/or specific environment created by the placenta may have significant impact on the type of HPV-specific immunity.

Human papillomavirus vertical transmission: review of current data

Despite the increasing evidence of human papillomavirus (HPV) vertical transmission, this route is regarded as less clinically important because of the detections of transient HPV DNA. However, recent studies have provided clear evidence of papillomavirus productive infection in lymphocytes, placenta, and bovine fetal tissue. Furthermore, a model of papillomavirus latency has been recently proposed that could explain the failure or transience in HPV detection observed in some infected infants. This new evidence of hematogeneous and vertical spread of HPV suggests that these modes of transmission should be investigated in greater detail to obtain a better understanding of the infection and a fuller awareness of the preventive measures that can be taken against HPV-related diseases.

Barriers of the Human Organism and Their Achilles’ Heels

The human body is covered by barriers separating it from the external and internal surroundings. The “milieu enterieur” has to be stabilised in spite of the variable external and internal conditions of toxic, osmotic, microbial and climatic environmental circumstances. This first line of barriers is composed of skin and mucous membranes of complicated structures.

A second line of barrier system is present in our organisms. Certain organs have to be separated from the immune system and other parts of the body because of evolutionary reasons (eye-bulb and testicles) because of unique proteins “unknown” for the acquired immune system. The blood-brain barrier (BBB) is providing enhanced safety circumstances for the central nervous system. The second line of barriers is represented by the special properties of the capillary endothelial system.

The maternal-fetal barrier is the most complex. At the maternal fetal interface two individuals of two different haplotypes has to be live 9 months separated by a very complicated dynamic barrier.

The placenta is the organ, which is separating the maternal and fetal tissues. Similar to others the bidirectional transport of gasses, metabolites, cells, proteins, regulatory substances, are transported by active or passive transcellular and intercellular mechanisms.

The fetal immune system develops immunotolerance to all maternal cells and antigens transferred transplacentally. The problem is to mitigate the maternal immune system to tolerate the paternal haplotype of the fetus. In the case of normal pregnancy a complex series of physiological modifications can solve the problem without harmful consequences to the mother and fetus.

The outermost contact cells of trophoblasts express instead of HLA-class Ia and class II antigens non-variable HLA-C, HLA-E, HLA-F and HLA-G antigens. The first consequence of this is reduction of the activity of maternal natural killer cells and maternal dendritic cells;

Progesteron, micro-RNA and mediators influence the development of T effector-cells. The production of soluble HLA-G(5 and 6) and IL-10 supports the differentiation of Th-2 CD4⁺ helper cells, reducing the ability of maternal cells to kill fetal cells.

Series of receptors and costimulators are expressed by the different lines of semi-allogenic trophoblast cells to bind HLA-G and mitigate maternal immune response;

The maternal immunotolerance is further facilitated by the activation of CD4⁺CD25^brightFoxp3⁺ regulatory T (T_REG) cells.

Infections have to be prevented during pregnancy. The cells of placenta express 10 Toll-like receptors a group of pattern recognition receptors responsible for innate immunity. The interferon level is also higher in the placental tissues than in the somatic fetal or maternal cells.

The complement system is also adapted to the requirements of the pregnancy and fetal damage is inhibited by the production of “assymmetric IgG antibodies” under hormonal and placental-regulation. These modifications prevent the activation of complement, cytotoxic activity, opsonising ability, antigen clearance and precipitating activity of the molecules.

The Achilles’ heels of the different barriers are regularly found by virus infections. Lamina cribrosa of the blood-brain barrier, optical nerve of the eyes, etc. the risk factors of the maternal-fetal barrier has been summarised in Table 1.1.

Symptomless intrauterine transmission of bovine herpesvirus 4 to bovine fetuses

Blood samples of 31 healthy calves and their dams taken immediately after calving before colostrum uptake, and at days 11, 23 and 8 weeks, spleens of seven stillborn calves were analysed in order to determine the source and time of bovine herpesvirus type 4 infection. All the calves were born as seronegatives, while all cattle were seropositives. Viral DNA were amplified by a nested PCR assay from 54.8% of peripheral blood leukocyte samples of newborn calves taken before colostrum uptake, and from all cattle and from their colostrums. Real time PCR detected higher virus level in peripheral blood leukocytes in adult cattle, then in their newborn calves. Bovine semen cells (spermatozoa and leukocyte fractions), spleens of stillborn calves also carried viral genomes. Our results prove, that bovine fetuses can be infected in utero by BoHV-4, but are born as seronegatives. After human examples this is the first report in veterinary virology on intrauterine transmission of a herpesvirus without acute consequences. This phenomenon could explain the low antigenicity of BoHV-4 proteins and lack of neutralizating antibodies. BoHV-4, a gammaherpesvirus, could serve as an animal model for studying inapparent herpesviral infections of human fetuses.

Viral ssRNA induces first trimester trophoblast apoptosis through an inflammatory mechanism

PROBLEM

Infection during pregnancy represents a significant cause of mobility and mortality. While viruses pose a major threat, little is known about their effect on early pregnancy, or the mechanisms involved. The objective of this study was to characterize the trophoblast response following exposure to viral ssRNA.

METHOD OF STUDY

First trimester trophoblast cells were treated with or without viral ssRNA. Cytokine production was measured using multiplex analysis and ELISA. Apoptosis was determined using Hoechst staining, cell viability, and caspase activity assays.

RESULTS

Treatment of trophoblasts with viral ssRNA increased their secretion of IL-8, IL-6, and IFNbeta. However, the ssRNA also induced trophoblast apoptosis. To test whether the viral ssRNA-induced inflammatory response was responsible for this induction of apoptosis, conditioned media (CM) from trophoblasts were added to a fresh culture of cells. The CM from viral ssRNA-treated induced higher levels of trophoblast apoptosis than the control CM. Moreover, recombinant IFNbeta induced trophoblast apoptosis.

CONCLUSION

We demonstrate that viral ssRNA induces a pro-inflammatory and type I interferon response in the trophoblast and this inflammatory process may indirectly induce trophoblast apoptosis. These results provide a novel mechanism by which certain viral infections might compromise placental integrity and function, and therefore, pregnancy outcome.