Genetic diversity and declining norovirus prevalence in infants and children during Japan's COVID-19 pandemic: a three-year molecular surveillance

Noroviruses (NoVs) are a global concern, causing widespread outbreaks and sporadic acute gastroenteritis (AGE) cases across all age groups. Recent research has shed light on the emergence of novel recombinant strains of NoV in various countries. To delve deeper into this phenomenon, we extensively analyzed 1,175 stool samples collected from Japanese infants and children with AGE from six different prefectures in Japan over three years, from July 2018 to June 2021. Our investigation aimed to determine the prevalence and genetic characteristics of NoV associated with sporadic AGE while exploring the possibility of detecting NoV recombination events. Among the analyzed samples, we identified 355 cases positive for NoV, 11 cases attributed to GI genotypes, and 344 associated with GII genotypes. Notably, we discovered four distinct GI genotypes (GI.2, GI.3, GI.4, and GI.6) and seven diverse GII genotypes (GII.2, GII.3, GII.4, GII.6, GII.7, GII.14, and GII.17). The predominant genotypes were GII.4 (56.4%; 194 out of 344), followed by GII.2 and GII.3. Through dual genotyping based on sequencing of the ORF1/ORF2 junction region, we identified a total of 14 different RdRp/capsid genotypes. Of particular interest were the prevalent recombinant genotypes GII.4[P31] and GII.2[P16]. Notably, our study revealed a decrease in the number of children infected with NoV during and after the COVID-19 pandemic. These findings underscore the importance of continuous NoV surveillance efforts.

Outbreak of human astroviruses 1 and Melbourne 2 in acute gastroenteritis pediatric patients in Japan during the COVID-19 pandemic, 2021

BACKGROUND

Human astrovirus (HAstV) infection is one of the leading causes of acute gastroenteritis in young children. The present study reports the outbreak of HAstV in children with acute gastroenteritis in Kyoto, Japan, during the COVID-19 pandemic, 2021.

METHODS

A total of 61 stool samples were collected from children with acute gastroenteritis who visited a pediatric outpatient clinic in Maizuru city, Kyoto, Japan from July to October, 2021. HAstV was screened by RT-PCR, and the genotypes were identified by nucleotide sequence analysis.

RESULTS

Of 61 cases of acute gastroenteritis, 20 were mono-infected with HAstV alone. In addition, mixed infection of HAstV and NoV, and HAstV and RVA were also detected in 15 and 1 cases, respectively. Of 36 HAstV strains detected in this outbreak, 29 and 7 were HAstV1 and MLB2 genotypes, respectively. All HAstV1 strains were closely related to the HAstV1 reported from Thailand and Japan in 2021 and all of them belonged to subgenotype HAstV1a. Among MLB2, they were most closely related to the MLB2 strains reported from China in 2016 and 2018.

CONCLUSIONS

After the kindergartens and schools were re-opened at the middle of 2021 in Japan, an outbreak of HAstV was reported. Control measures against the COVID-19 pandemics might affect the spread of diarrheal virus infection. Here we report the outbreak of HAstV1 and MLB2 in Kyoto, Japan, during COVID-19 pandemic in 2021.

The Factors Influencing Pregnant Women's Selection of Media Sources to Obtain Information on COVID-19 in Japan in 2021

Pregnant women presumably gather information about the coronavirus disease 2019 (COVID-19) from various sources. However, it is difficult for pregnant women who are not medical professionals to source the appropriate information because of the infodemic related to the COVID-19 pandemic. Therefore, the objective of our study was to investigate how pregnant women gathered information about COVID-19 and COVID-19 vaccination. To address this issue, we conducted an online questionnaire survey between 5 October and 22 November 2021, which was approved by the Ethics Committee of Nihon University School of Medicine. We received 4962 responses after excluding 1179 insufficient answers. Our study found that age, occupation, and infection-risk anxiety influenced the selection of media for obtaining information. Pregnant women who were older, medical professionals, public servants, or educators tended to rely on specialized medical websites, whereas housewives tended to use mass media, social media, and sources with uncertain scientific evidence. Additionally, the number of weeks of gestation and the method of conception (natural or assisted reproductive conception) affected the selection of media. The accessibility of COVID-19 information for pregnant women was determined by their social background and pregnancy status. We need to continue making efforts to ensure that appropriate information is readily available to pregnant women and their families.

Roles of TGF-β1 in Viral Infection during Pregnancy: Research Update and Perspectives

Transforming growth factor-beta 1 (TGF-β1) is a pleiotropic growth factor playing various roles in the human body including cell growth and development. More functions of TGF-β1 have been discovered, especially its roles in viral infection. TGF-β1 is abundant at the maternal-fetal interface during pregnancy and plays an important function in immune tolerance, an essential key factor for pregnancy success. It plays some critical roles in viral infection in pregnancy, such as its effects on the infection and replication of human cytomegalovirus in syncytiotrophoblasts. Interestingly, its role in the enhancement of Zika virus (ZIKV) infection and replication in first-trimester trophoblasts has recently been reported. The above up-to-date findings have opened one of the promising approaches to studying the mechanisms of viral infection during pregnancy with links to corresponding congenital syndromes. In this article, we review our current and recent advances in understanding the roles of TGF-β1 in viral infection. Our discussion focuses on viral infection during pregnancy, especially in the first trimester. We highlight the mutual roles of viral infection and TGF-β1 in specific contexts and possible functions of the Smad pathway in viral infection, with a special note on ZIKV infection. In addition, we discuss promising approaches to performing further studies on this topic.

Pathological roles of antimicrobial peptides and pro-inflammatory factors secreted from the cervical epithelium in Gardnerella vaginalis-abundant vaginal flora in pregnancy

Bacterial vaginosis due to Gardnerella vaginalis (GV) is one of the main causes of preterm birth. Antimicrobial function of the cervical glands prevents ascending pathogen infection. This study investigated the effect of GV on the cervical gland cells. We examined the correlation between GV and neutrophil elastase in the cervical mucous obtained from pregnant women's clinical samples. Culture supernatants (sup) of GV and Lactobacillus crispatus (LC) were added to human immortalized cervical gland cells (EndoCx). Quantitative reverse transcription PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) were used to examine the effects on the production of antimicrobial peptides (AMPs), secretory leukocyte peptidase inhibitor (SLPI), and Elafin. mRNA microarray analysis revealed the expression profile of GV-exposed EndoCx. Moreover, the antimicrobial activity of Elafin against LC and GV was investigated. In the clinical samples, neutrophil elastase was increased in the GV-positive cervical mucous. In an in vitro assay, RT-qPCR and ELISA showed that GV-sup enhanced the secretion of Elafin, but not SLPI, from EndoCx, whereas LC-sup did not. mRNA microarray assay and ELISA results demonstrated that GV-sup enhanced the proinflammatory pathway and interleukin (IL)- 8 secretion from EndoCx as well as cell adhesion and tight junction pathways. Moreover, GV-sup directly enhanced Elafin and IL-8 secretion from the cervical gland cells. In the GV-abundant vaginal flora, IL-8 level increased the neutrophil elastase activity and Elafin inhibited the elastase activity to protect from tissue damage and infection. Thus, the balance of IL-8-induced neutrophil and Elafin-induced antiprotease activities may be crucial in preterm labor.

Female reproductive tract-organ axes

The female reproductive tract (FRT) and remote/versatile organs in the body share bidirectional communication. In this review, we discuss the framework of the "FRT-organ axes." Each axis, namely, the vagina-gut axis, uterus-gut axis, ovary-gut axis, vagina-bladder axis, vagina-oral axis, uterus-oral axis, vagina-brain axis, uterus-brain axis, and vagina-joint axis, is comprehensively discussed separately. Each axis could be involved in the pathogenesis of not only gynecological diseases but also diseases occurring apart from the FRT. Although the microbiota is clearly a key player in the FRT-organ axes, more quantitative insight into the homeostasis of the microbiota could be provided by host function measurements rather than current microbe-centric approaches. Therefore, investigation of the FRT-organ axes would provide us with a multicentric approach, including immune, neural, endocrine, and metabolic aspects, for understanding the homeostatic mechanism of women's bodies. The framework of the FRT-organ axes could also provide insights into finding new therapeutic approaches to maintain women's health.

Massive intravascular hemolysis is an important factor in Clostridium perfringens-induced bacteremia

Clostridium perfringens bacteremia is rare but often fatal. In particular, once bacteremia with massive intravascular hemolysis (MIH) occurs, the mortality rate is extremely high. However, because of its rarity, the detailed pathophysiology of this fulminant form of bacteremia is unclear. To elucidate the detailed pathogenesis of MIH, we retrospectively reviewed the data of all patients with C. perfringens bacteremia from two university hospitals from 2000 to 2014. The medical records and laboratory data of 60 patients with bacteremia, including 6 patients with MIH and 54 patients without MIH, were analyzed. Patients with MIH had higher rates of intense pain at onset, impaired consciousness, shock at presentation, hematuria, metabolic acidosis, and gas formation than patients without MIH. The antibiotic susceptibility of the clinical isolates was not significantly different between the two groups. All patients with MIH, although treated with appropriate antimicrobial agents, died within 26 h of admission due to rapidly progressive acute lung injury or acute respiratory distress syndrome, and the median time from arrival at the hospital to death was only 4 h and 20 min. When clinicians observe intravascular hemolysis in blood samples from patients with characteristic symptoms of MIH, they should prepare for a severe disease outcome. The underlying pathophysiology of fulminant cases must be investigated.

Inhibition of Epithelial-Mesenchymal Transition Maintains Stemness in Human Amniotic Epithelial Cells

Human amniotic epithelial cells (hAECs), which are a type of placental stem cell, express stem cell marker genes and are capable of differentiating into all three germ layers under appropriate culture conditions. hAECs are known to undergo TGF-β-dependent epithelial-mesenchymal transition (EMT); however, the impact of EMT on the stemness or differentiation of hAECs has not yet been determined. Here, we first confirmed that hAECs undergo EMT immediately after starting primary culture. Comprehensive transcriptome analysis using RNA-seq revealed that inhibition of TGF-β-dependent EMT maintained the expression of stemness-related genes, including NANOG and POU5F1, in hAECs. Moreover, the maintenance of stemness did not affect the nontumorigenic characteristics of hAECs. We showed for the first time that TGF-β-dependent EMT negatively affected the stemness of hAECs, providing novel insight into cellular processes of placental stem cells.

Enhancement of Rubella Virus Infection in Immortalized Human First-Trimester Trophoblasts Under Low-Glucose Stress Conditions

Rubella virus (RuV) infections in pregnant women, especially first-trimester infections, can lead to congenital rubella syndrome (CRS). However, the mechanisms of fetal RuV infection are not completely understood, and it is not observed in every pregnant woman infected with RuV. As gestational diabetes mellitus is a risk factor for congenital viral infections, we investigated the possible roles of hypoglycemia-related endoplasmic reticulum (ER) stress as a key factor for vertical RuV infection using immortalized human first-trimester trophoblasts. Low-glucose stress was induced prior to RuV infection by culturing HTR-8/SVneo and Swan.71 cells in low-glucose (LG) medium for 24 h or high-glucose medium for 6 h and then LG medium for an additional 18 h. Clinically isolated RuV was inoculated at a multiplicity of infection of 5 to 10. The intracellular localization of the RuV capsid protein was investigated 24 to 48 h post-infection (pi) with flow cytometry (FCM) analysis and fluorescence microscopy. Viral progeny production was monitored by FCM analysis. Increases in RuV infection in LG-induced ER-stressed trophoblasts were observed. No significant increase in apoptosis of RuV-infected cells was noted at days 2 and 5 pi, and substantial viral progeny production was observed until day 5 pi. An approximate fivefold increase in viral binding was noted for the LG-stressed cells. Although the detailed mechanisms underlying viral entry into LG-stressed cells are not known and require further investigation, these findings suggest that a certain degree of LG stress in early pregnancy may facilitate infection and cause CRS.

Restriction of SARS-CoV-2 replication in the human placenta

Although SARS-CoV-2 can infect human placental tissue, vertical transmission is rare. Therefore, the placenta may function as a barrier to inhibit viral transmission to the foetus, though the mechanisms remain unclear. In this study, we confirmed the presence of the SARS-CoV-2 genome in human placental tissue by in situ hybridization with antisense probes targeting the spike protein; tissue staining was much lower when using sense probes for the spike protein. To the best of our knowledge, this is the first evidence directly indicating inefficient viral replication in the SARS-CoV-2-infected placenta. Additional studies are required to reveal the detailed mechanisms.

Low Susceptibility of Rubella Virus in First-Trimester Trophoblast Cell Lines

We recently published an article about myelin oligodendrocyte glycoprotein-independent rubella infection of keratinocytes in vitro, in which first-trimester trophoblast cells were shown as rubella virus (RuV)-resistant. Given an incident rate as high as 90% of congenital rubella syndrome in the first eight weeks of pregnancy, the RuV infection of first-trimester trophoblasts is considered key to opening the gate to transplacental transmission mechanisms. Therefore, with this study, we aimed to verify the susceptibility/resistance of first-trimester trophoblast cell lines, HTR-8/SVneo and Swan.71, against RuV. Cells cultured on multi-well plates were challenged with a RuV clinical strain at a multiplicity of infection from 5 to 10 for 3 h. The infectivity was investigated by immunofluorescence (IF) assay and flow cytometry (FCM) analysis. Supernatants collected during the post-infection period were used to determine virus-progeny production. The scattered signaling of RuV infection of these cells was noted by IF assay, and the FCM analysis showed an average of 4–5% of gated cells infected with RuV. In addition, a small but significant production of virus progeny was also observed. In conclusion, by employing appropriate approaches, we determined the low infectivity of RuV in first-trimester trophoblast cell lines but not resistance as in our previous report.

Intrauterine fetal death during COVID-19 pregnancy: Typical fetal heart rate changes, coagulopathy, and placentitis

Although various perinatal outcomes in coronavirus disease 2019 (COVID‐19) pregnancies have been reported, the fetal and neonatal consequences of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection remain unclear. Several reports of miscarriages and stillbirths have been recorded, but vertical transmission by SARS‐CoV‐2 is considered very rare, and the cause remains unknown. We report a case of a 22‐year‐old uncomplicated Japanese woman infected with SARS‐CoV‐2 during the second trimester, resulting in intrauterine fetal death due to placental insufficiency associated with COVID‐19 placentitis. This report emphasizes the importance of longitudinal assessment of fetal well‐being by fetal heart rate monitoring and early detection of maternal coagulation dysfunction representing SARS‐CoV‐2 inflammation to manage COVID‐19 in pregnancy.

Adverse events after BNT162b2 mRNA COVID-19 vaccination in health care workers and medical students in Japan

To control the coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the promotion of vaccination is important. However, adverse reactions following vaccination remain a concern. To investigate adverse events in the vaccinated Japanese population, we conducted a survey-based study among health care workers, including medical doctors and nurses; other medical staff; and medical university faculty, staff, and students in a single medical school and affiliated hospital in Japan. In addition, we analyzed the association of different adverse events with individual factors (e.g., age, sex) by performing network analysis. While young age and female sex are often considered risk factors for more severe adverse events, the regression models showed neither age nor sex was associated with local injection-site reactions after the second dose in this study. In contrast to local reactions, systemic adverse events were associated with young age and female sex. However, myalgia was unique in that it was not associated with younger age even though the network analysis showed that myalgia was consistently related to arthralgia and belonged to the group of systemic events after both the first and second vaccine doses. Further study is needed to ensure safe and effective vaccination to aid in controlling the COVID-19 pandemic.

The vaccination status and adverse effects of COVID-19 vaccine among pregnant women in Japan in 2021

To investigate the vaccination status and adverse reactions to the COVID‐19 vaccine among pregnant women in Japan, we conducted an online questionnaire survey from October 5 to November 22, 2021. The number of participants in the online survey was 6576. Of the participants, 4840 (73.6%) were vaccinated twice, and 557 (8.5%) were vaccinated once. A total of 1179 (17.9%) responders had never been vaccinated against COVID‐19. The most frequent adverse reaction was local pain at the injection site. The incidence of local adverse reactions was almost identical after the first and the second vaccinations, while systemic reactions, such as fever and fatigue/malaise, and adverse reactions outside the vaccination site such as headache and arthralgia, were more frequent after the second vaccination than after the first vaccination. Regarding the obstetrical complications, uterine tension and/or contraction was observed in 1.65% of the pregnant women after the first vaccination and in 2.98% after the second vaccination, and uterine pain appeared in 1.06% of the pregnant women after the second vaccination. However, serious symptoms, such as hemorrhage, decreased fetal movement, edema, increased blood pressure, and amniorrhexis, were seen in less than 1% of vaccinated women after both the first and second vaccinations. This study clarified the characteristics of vaccination, adverse reactions, and obstetrical symptoms in pregnant women in Japan who had the COVID‐19 vaccine up to the second dose. As a booster vaccination is currently underway, further study is needed to improve the management of pregnant women during the current pandemic.

Liver X receptors regulate natural killer T cell population and antitumor activity in the liver of mice

The nuclear receptors liver X receptor α (LXRα) and LXRβ are lipid sensors that regulate lipid metabolism and immunity. Natural killer T (NKT) cells, a T cell subset expressing surface markers of both natural killer cells and T lymphocytes and involved in antitumor immunity, are another abundant immune cell type in the liver. The potential function of the metabolic regulators LXRα/β in hepatic NKT cells remains unknown. In this study, we examined the role of LXRα and LXRβ in NKT cells using mice deficient for LXRα and/or LXRβ, and found that hepatic invariant NKT (iNKT) cells are drastically decreased in LXRα/β-KO mice. Cytokine production stimulated by the iNKT cell activator α-galactosylceramide was impaired in LXRα/β-KO hepatic mononuclear cells and in LXRα/β-KO mice. iNKT cell-mediated antitumor effect was also disturbed in LXRα/β-KO mice. LXRα/β-KO mice transplanted with wild-type bone marrow showed decreased iNKT cells in the liver and spleen. The thymus of LXRα/β-KO mice showed a decreased population of iNKT cells. In conclusion, LXRα and LXRβ are essential for NKT cell-mediated immunity, such as cytokine production and hepatic antitumor activity, and are involved in NKT cell development in immune tissues, such as the thymus.

Pathogenic Characterization of Clostridium perfringens Strains Isolated From Patients With Massive Intravascular Hemolysis

Sepsis caused by Clostridium perfringens infection is rare but often fatal. The most serious complication leading to poor prognosis is massive intravascular hemolysis (MIH). However, the molecular mechanism underlying this fulminant form of hemolysis is unclear. In the present study, we employed 11 clinical strains isolated from patients with C. perfringens septicemia and subdivided these isolates into groups H and NH: septicemia with (n = 5) or without (n = 6) MIH, respectively. To elucidate the major pathogenic factors of MIH, biological features were compared between these groups. The isolates of two groups did not differ in growth rate, virulence-related gene expression, or phospholipase C (CPA) production. Erythrocyte hemolysis was predominantly observed in culture supernatants of the strains in group H, and the human erythrocyte hemolysis rate was significantly correlated with perfringolysin O (PFO) production. Correlations were also found among PFO production, human peripheral blood mononuclear cell (PBMC) cytotoxicity, and production of interleukin-6 (IL-6) and interleukin-8 (IL-8) by human PBMCs. Analysis of proinflammatory cytokines showed that PFO induced tumor necrosis factor-α (TNF-α), IL-5, IL-6, and IL-8 production more strongly than did CPA. PFO exerted potent cytotoxic and proinflammatory cytokine induction effects on human blood cells. PFO may be a major virulence factor of sepsis with MIH, and potent proinflammatory cytokine production induced by PFO may influence the rapid progression of this fatal disease caused by C. perfringens.

Lactobacillus crispatus promotes invasion of the HTR-8/SVneo trophoblast cell line

INTRODUCTION

Recent studies have shown that the endometrium possesses unique microbiomes, including Lactobacillus. However, the roles of these microbes are currently unknown, especially in placentation and the early stage of pregnancy.

METHODS

The immortalized human first-trimester trophoblast cell line HTR-8/SVneo was cultured in the presence or absence of Lactobacillus crispatus. Invasive and migrative activities were directly evaluated using an optical microscope and a time-lapse imaging system. Protein levels of the invasion-related protein matrix metalloproteinase (MMP)-1, MMP-2, and MMP-9 were evaluated using ELISA.

RESULTS

Matrigel invasion of HTR-8/SVneo cells was significantly increased by L. crispatus, though migration was not affected. The culture supernatant of L. crispatus also promoted invasion. Additionally, levels of the active forms of MMP-1 and MMP-2 in the cell culture medium were upregulated by L. crispatus treatment, but that of MMP-9 was not changed.

DISCUSSION

L. crispatus promotes trophoblast invasion with an increase in MMP-1 and MMP-2 activation. Our results might explain why Lactobacillus dominance in the endometrium seems beneficial for implantation. Nevertheless, further research is required to determine whether the promotion of trophoblast invasion by L. cripatus is favorable for successful placentation at the early stage of pregnancy.

Anti-SARS-CoV-2 vaccination strategy for pregnant women in Japan

The current COVID‐19 pandemic is a global concern. The recent introduction of vaccines has provided a reason for hope, but new problems, such as vaccine hesitancy, have arisen. One of the most important of these issues is the safety of vaccines for pregnant women. In this article, we collected worldwide indications for vaccination, including women who are pregnant or who wish to become pregnant, and reports of adverse reactions to COVID‐19 vaccination. The Japan Society of Obstetrics and Gynecology and the Japanese Society of Infectious Diseases in Obstetrics and Gynecology have published recommendations for the vaccination of pregnant women with a COVID‐19 vaccine. The guidelines are as follows: (1) pregnant women should not be excluded from vaccination; (2) informed consent should be obtained before vaccination; (3) healthcare workers and pregnant women with complications such as diabetes, hypertension, and obesity should be vaccinated preferentially; (4) vaccination should be avoided until 12 weeks of gestation during organogenesis; (5) spouse and family members should be vaccinated actively; and (6) nursing mothers are not particularly affected. This policy has been adopted in government guidelines. Additional efforts should be made to protect pregnant women from infection and severe illness with COVID‐19 by eliminating vaccine hesitancy.

Genetic diversity of Parechovirus A in infants and children with acute gastroenteritis in Japan during 2016-2018

Parechovirus A (PeV-A), previously known as human parechovirus, is a common pathogen in children that can cause respiratory and gastrointestinal diseases as well as severe neurological disease. Take advantage of our previous findings on the genetic diversity of PeV-A circulating in Japanese children with acute gastroenteritis (AGE), this study was conducted to investigate the genetic diversity of PeV-A isolated from children with AGE in Japan as well as their clinical symptoms. Of 1070 stool samples collected from Japanese infants and children with AGE during the 2-year period from July 2016 to June 2018, 76 were positive for PeV-A by multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) and were subjected to genotyping based on viral protein 1 (VP1) sequences. Five different PeV-A genotypes including PeV-A1B, -A2, -A3, -A4, and -A6 were detected with predominant of PeV-A1 clade B genotype. This study revealed a high genetic diversity of PeV-A circulating in Japanese infants and children with AGE and the PeV-A2, a rare genotype, was detected for the first time in Japan in patients with AGE. The clinical symptoms observed in these patients included diarrhea, vomiting, fever, cough, rhinorrhea, and dehydration.

Placental barrier against COVID-19

Vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and possible induction of pregnancy complications, including miscarriage, fetal malformations, fetal growth restriction and/or stillbirth, are serious concerns for pregnant individuals with COVID-19. According to clinical information, the incidence of vertical transmission of SARS-CoV-2 is limited to date. However, even if a neonate tests negative for SARS-CoV-2, frequent abnormal findings, including fetal and maternal vascular malperfusion, have been reported in cases of COVID-19-positive mothers. Primary receptor of SARS-CoV-2 is estimated as angiotensin-converting enzyme 2 (ACE2). It is highly expressed in maternal-fetal interface cells, such as syncytiotrophoblasts, cytotrophoblasts, endothelial cells, and the vascular smooth muscle cells of primary and secondary villi. However other route of transplacental infection cannot be ruled out. Pathological examinations have demonstrated that syncytiotrophoblasts are often infected with SARS-CoV-2, but fetuses are not always infected. These findings suggest the presence of a placental barrier, even if it is not completely effective. As the frequency and molecular mechanisms of intrauterine vertical transmission of SARS-CoV-2 have not been determined to date, intensive clinical examinations by repeated ultrasound and fetal heart rate monitoring are strongly recommended for pregnant women infected with COVID-19. In addition, careful investigation of placental samples after delivery by both morphological and molecular methods is also strongly recommended.

Interleukin-22 promotes the migration and invasion of oral squamous cell carcinoma cells

The roles of interleukin-22 (IL-22) in carcinogenesis have been proposed in various neoplasms. Increased expression of IL-22 has been observed in oral squamous cell carcinoma (OSCC) lesions as well as in other cancers. OSCC is still associated with poor prognosis and a high mortality rate because of its invasiveness and frequent lymph node metastasis. In the present study, we investigated the effects of IL-22 on OSCC cells. The human OSCC cell lines Ca9-22 and SAS were stimulated with IL-22 (1-10 ng/mL), and their migration abilities were examined using a cell scratch assay. A Matrigel invasion assay was performed to evaluate the invasion abilities of OSCC cells. Signal transducer and activator of transcription 3 (STAT3) phosphorylation, matrix metalloproteinase (MMP) and epithelial-mesenchymal transition (EMT)-related genes and proteins were also examined. IL-22 treatment promoted the migration and invasion abilities of OSCC cells without increasing their viability. IL-22 stimulation also induced STAT3 phosphorylation, MMP-9 activity and EMT-related genes and proteins. Our findings suggest that IL-22 has possible roles in the development of OSCC.

Cow milk exosomes activate NK cells and γδT cells in human PBMCs in vitro

Cow milk is a nourishing food containing numerous essential nutrients. In Japan, the consumption of cow milk is thought to enhance resistance to exhaustion-related diseases. Although several nutrients in cow milk, such as lactoferrin, are thought to modulate immune cells, the mechanisms remain unclear. Recently, the immunoregulatory functions of food-derived microRNAs or exosomes have been reported. Therefore, we studied the effects of exosomes derived from cow milk (CM-Exs) on immune cells in the present study. We obtained blood samples from healthy adult donors with the approval of the ethics committee. Peripheral blood mononuclear cells (PBMCs) were stimulated with CM-Exs in the absence or presence of interleukin-2 (IL-2) and IL-12. Cell surface markers and intracellular cytokine production were analysed by flow cytometry. CM-Ex stimulation enhanced the expression of CD69 on NK cells. Although CM-Ex stimulation alone did not induce interferon-γ (IFN-γ) production by NK cells or γδT cells, simultaneous stimulation with CM-Ex, IL-2 and IL-12 significantly enhanced IFN-γ production. In conclusion, cow milk consumption alone may not activate immune cells; however, CM-Exs could enhance immune cells under inflammatory conditions.

MHC-restricted Ag85B-specific CD8+ T cells are enhanced by recombinant BCG prime and DNA boost immunization in mice

Despite efforts to develop effective treatments and vaccines, Mycobacterium tuberculosis (Mtb), particularly pulmonary Mtb, continues to provide major health challenges worldwide. To improve immunization against the persistent health challenge of Mtb infection, we have studied the CD8+ T cell response to Bacillus Calmette-Guérin (BCG) and recombinant BCG (rBCG) in mice. Here, we generated CD8+ T cells with an rBCG-based vaccine encoding the Ag85B protein of M. kansasii, termed rBCG-Mkan85B, followed by boosting with plasmid DNA expressing the Ag85B gene (DNA-Mkan85B). We identified two MHC-I (H2-Kd )-restricted epitopes that induce cross-reactive responses to Mtb and other related mycobacteria in both BALB/c (H2d ) and CB6F1 (H2b/d ) mice. The H2-Kd -restricted peptide epitopes elicited polyfunctional CD8+ T cell responses that were also highly cross-reactive with those of other proteins of the Ag85 complex. Tetramer staining indicated that the two H2-Kd -restricted epitopes elicit distinct CD8+ T cell populations, a result explained by the X-ray structure of the two peptide/H2-Kd complexes. These results suggest that rBCG-Mkan85B vector-based immunization and DNA-Mkan85B boost may enhance CD8+ T cell response to Mtb, and might help to overcome the limited effectiveness of the current BCG in eliciting tuberculosis immunity.

Lactobacillus crispatus accelerates re-epithelialization in vaginal epithelial cell line MS74

PROBLEM

The functions of vaginal lactobacilli in susceptibility to infectious diseases as regards epithelial barrier integrity and wound healing remain incompletely understood.

METHOD OF STUDY

Lactobacillus crispatus, one of the most common Lactobacillus species in the vagina and among the most protective against sexually transmitted infections, was cocultured with an immortalized human vaginal epithelial cell line (MS74), and a scratch assay was performed to evaluate re-epithelialization. The concentration of vascular endothelial growth factor A (VEGF) was measured using enzyme-linked immunosorbent assay (ELISA). An immunofluorescence assay was performed to locate the expression of VEGF and VEGF receptor (VEGFR) 1 and 2. The effects of the bacterial supernatant of L. crispatus were also evaluated.

RESULTS

Lactobacillus crispatus significantly accelerated re-epithelialization of MS74 cells, accompanied by an increase in VEGF concentration. In contrast, heat-killed L. crispatus did not show this effect. The bacterial supernatant of L. crispatus also induced re-epithelialization. The immunoreactivity of VEGF was higher at the scratched edge, whereas VEGFR1 and 2 stained site-independently. Recombinant VEGF induced cell migration in a dose-dependent manner. The bacterial supernatant of L. crispatus also significantly accelerated re-epithelialization in MS74 cells and increased the concentration of VEGF in the culture 24 hours after the scratch.

CONCLUSION

These results may enhance our knowledge of the importance of L. crispatus in the healing of damaged vaginal epithelium and protection against the consequent risk of pathogenic infections, such as human immunodeficiency virus (HIV), and improve our understanding of vaginal epithelial barrier integrity maintenance by this bacterium.

Periodontal diseases and adverse pregnancy outcomes

From last decade of the 20th century, numerous epidemiological studies and intervention trials have attempted to prove the relationships between maternal periodontal diseases and adverse pregnancy outcomes (APO). Periodontal diseases are considered a risk factor for APO, including preterm birth, fetal growth restriction, low birthweight, pre-eclampsia and gestational diabetes. However, the efficacy of periodontal treatment during pregnancy is controversial. Two pathogenic mechanisms might explain the potential effect of periodontal diseases on pregnancy outcomes. First, periodontal bacteria originating in the gingival biofilm directly affect the feto-placental unit subsequent to bacteremia. Second, inflammatory mediators secreted by the subgingival inflammatory site are carried to the feto-placental unit, where they then cause an inflammatory response. To elucidate these mechanisms, many researchers have been investigating the use of experimental animal models and in vitro models. In the present review, we summarize the current literature on the relationship between periodontal diseases and APO from epidemiological studies, animal models studies and in vitro studies, and speculate on the possible mechanism of periodontal diseases affecting pregnancy outcomes.

A 3-Month-Old Child with Acute Gastroenteritis with Enterovirus D68 Detected from Stool Specimen

Enterovirus D68 (EV-D68) is known to be causative agent of mild to severe upper and lower respiratory illnesses in sporadic cases and outbreaks. We present a case report of a 3-month-old child with acute gastroenteritis who visited a pediatric clinic in Kyushu area in Japan in 2015. A stool sample collected from the patient was screened for diarrheal viruses by multiplex RT-PCR. The result showed that the sample was positive only for enterovirus, and EV-D68 clade B3 was identified by sequence analysis of the viral protein 1 gene. This study supports an association between EV-D68 infection and acute gastroenteritis.

Liver X receptors regulate hepatic F4/80 + CD11b+ Kupffer cells/macrophages and innate immune responses in mice

The liver X receptors (LXRs), LXRα and LXRβ, are nuclear receptors that regulate lipid homeostasis. LXRs also regulate inflammatory responses in cultured macrophages. However, the role of LXRs in hepatic immune cells remains poorly characterized. We investigated the role of LXRs in regulation of inflammatory responses of hepatic mononuclear cells (MNCs) in mice. Both LXRα and LXRβ were expressed in mouse hepatic MNCs and F4/80⁺ Kupffer cells/macrophages. LXRα/β-knockout (KO) mice had an increased number of hepatic MNCs and elevated expression of macrophage surface markers and inflammatory cytokines compared to wild-type (WT) mice. Among MNCs, F4/80⁺CD11b⁺ cells, not F4/80⁺CD11b^- or F4/80⁺CD68⁺ cells, were increased in LXRα/β-KO mice more than WT mice. Isolated hepatic MNCs and F4/80⁺CD11b⁺ cells of LXRα/β-KO mice showed enhanced production of inflammatory cytokines after stimulation by lipopolysaccharide or CpG-DNA compared to WT cells, and LXR ligand treatment suppressed lipopolysaccharide-induced cytokine expression in hepatic MNCs. Lipopolysaccharide administration also stimulated inflammatory cytokine production in LXRα/β-KO mice more effectively than WT mice. Thus, LXR deletion enhances recruitment of F4/80⁺CD11b⁺ Kupffer cells/macrophages and acute immune responses in the liver. LXRs regulate the Kupffer cell/macrophage population and innate immune and inflammatory responses in mouse liver.

Detection and genetic characterization of enterovirus strains circulating among children with acute gastroenteritis in Japan during 2014-2016

Of 972 stool samples collected from infants and children with acute gastroenteritis in six different regions (Hokkaido, Tokyo, Shizuoka, Kyoto, Osaka, and Saga) of Japan during 2-year period from July 2014 to June 2016, 63 samples (6.5%) determined to be positive for enterovirus by multiplex RT-PCR were subjected to genotype determination based on the partial VP1 region using the CODEHOP method. Sixty-two strains were succeeded in genotyping and seventeen EV types were identified. The majority of the studied strains belonged to EV-A (30 of 62; 48.4%) and EV-B (31 of 62, 50%) species, and the remaining strain was of the EV-D species. The most frequently detected type was Coxsackievirus A5 (CV-A5) in 2014-2015 while was CV-B5 in 2015-2016. This study provides an insight into the genetic diversity of EV with the predominance of EV-A and EV-B species in Japanese infants and children with acute gastroenteritis during 2014-2016.

Frequent isolation of extended-spectrum beta-lactamase-producing bacteria from fecal samples of individuals with severe motor and intellectual disabilities

Extended-spectrum beta-lactamase (ESBL) producing bacteria spread worldwide and became major concern for antibiotic treatment. Although surveillance reports in general hospitals and long-term care facilities are increasing, their frequencies in individuals with severe motor and intellectual disabilities (SMID) are so far unknown. In this study, we examined the frequency of ESBL in stool samples collected from 146 asymptomatic SMID subjects hospitalized in a single institution. With their clinical information, we evaluated possible risk factors for ESBL colonization. From 146 fecal samples, ESBL-producing bacteria were isolated in 45 cases (31%). Drug sensitivity testing showed that 82% of the isolates were resistant to levofloxacin but were sensitive to tazobactam/piperacillin and cefmetazole. The most frequent genotype was CTX-M-9 detected in 36/45 (80%). A high degree of disability, antibiotic use within three months before sampling and post-tracheostomy were statistically significant risk factors. Tube feeding was also strongly correlated with ESBL colonization (p < 0.001) and associated with lower micro-organismic diversities. Our findings are the first to reveal a high prevalence of ESBL in the fecal samples of SMID individuals and suggest possible relationships between high degree disability, tube feeding and latest histories of antibiotic use.

Myelin Oligodendrocyte Glycoprotein-Independent Rubella Infection of Keratinocytes and Resistance of First-Trimester Trophoblast Cells to Rubella Virus In Vitro

Rubella virus (RuV), which belongs to the family Togaviridae and genus Rubivirus, causes systemic infection in children and young adults and congenital rubella syndrome in developing fetuses if the infection occurs during pregnancy. The mechanisms of fetal infection by RuV are not completely understood. Myelin oligodendrocyte glycoprotein (MOG) is reported to be a cellular receptor for RuV; however, it is mainly expressed in the central nervous system. Therefore, it is thought that other receptors are also responsible for virus entry into susceptible cells. In this study, we found that first-trimester trophoblast cells were resistant to RuV. In addition, we showed that HaCaT cells (an immortalized keratinocyte cell line) that did not express MOG on their surface were infected with RuV. This finding is one of the first demonstrations of MOG-independent RuV infection of susceptible host cells and suggests that it is important to continue searching for alternative RuV receptors. In addition, this study reports the resistance of first-trimester trophoblast cells to RuV and suggests that utilizing an epithelial-mesenchymal transition approach to study the mechanisms of transplacental vertical RuV infection.

High Mobility Group Box 1 Protein Enhances HIV Replication in Newly Infected Primary T Cells

BACKGROUND

High-mobility group box 1 (HMGB1), a DNA-binding protein, has recently been shown to have effects on HIV replication, but the effects are dependent on the cell type and the timing of infection. Using human primary T cells, this study aimed to investigate the role of HMGB1 in HIV-1 replication in newly infected cells.

METHODS

Human primary T cells were infected with the HIV-1 LAI (X4) strain and then cultured in the presence of recombinant HMGB1 protein or an anti-HMGB1 antibody at various concentrations. At the indicated time points, HIV-1 p24 concentrations in the culture media were measured by ELISA. Cell proliferation, basal HMGB1 concentration, and CD3, CD4, CXCR4, and receptor for advanced glycation end products (RAGE) expression were also examined.

RESULTS

Recombinant HMGB1 could enhance HIV replication in newly infected primary T cells. In the presence of an anti-HMGB1 antibody (5 µg/mL or higher), significantly lower concentrations of HIV-1 p24 were observed in the cultures of primary T cells during the post-infection period.

CONCLUSIONS

The data presented suggest that HMGB1 plays a role in the enhancement of HIV-1 replication in newly infected T cells. This finding provides useful information toward understanding HIV pathogenesis and for the development of new therapeutic strategies.

Multiplex PCR for the Detection of 10 Viruses Causing Encephalitis/Encephalopathy and its Application to Clinical Samples Collected from Japanese Children with Suspected Viral

BACKGROUND

Acute encephalitis is a serious neurological condition having a high mortality rate and affecting both children and adults. This study aimed to develop a multiplex PCR method for the simultaneous screening of clinical samples for the presence of the 10 viruses presently considered as the major viral causes of acute encephalitis/ encephalopathy in Asia.

METHODS

Using previously published primers that have been widely used to screen for herpes virus-6, influenza A virus, human parechovirus, herpes simplex viruses 1 and 2, Japanese encephalitis virus, group A rotavirus, enterovirus, adenovirus, and dengue virus in clinical samples, a single-tube multiplex PCR assay was developed and was tested for its sensitivity and specificity. The method was then applied to screen 57 clinical samples, consisting of 13 fecal samples, 5 throat swabs, 3 post-nasal swabs, 18 serum samples, and 18 cerebrospinal fluid (CSF) samples, collected from 18 hospitalized Japanese children with suspected viral encephalitis/encephalopathy for the target viruses, and the results were compared with those of a monoplex PCR method.

RESULTS

Positive viral controls of the 10 viruses were correctly typed using this multiplex PCR method. The multiplex PCR method showed high specificity with no unspecific amplification to non-target viruses. The results of applying this PCR method for screening clinical samples showed that 6 fecal samples, 2 serum samples, and 1 CSF sample collected from 7 patients were positive for a virus, specifically group A rotavirus (4 patients, 22.2%), enterovirus (2 patients, 11.1%), or adenovirus (1 patient, 5.6%). In comparison with monoplex PCR, for group A rotavirus, enterovirus, and adenovirus, the sensitivity of this multiplex PCR method decreased for serum, cerebrospinal fluid, and throat swab samples.

CONCLUSIONS

This newly developed multiplex PCR method is a simple, rapid diagnostic tool and can be used to screen clinical samples for viruses causing acute encephalitis/encephalopathy in children in Asian countries.

Poly I:C induces collective migration of HaCaT keratinocytes via IL-8

Background

Delayed wound healing reduces the quality of life (QOL) of patients. Thus, understanding the mechanism of wound healing is indispensable for better management. However, the role of innate immunity in wound healing is thus far unknown. Recently the involvement of TLR3 in wound healing has been evaluated. The systemic administration of polyriboinosinic-polyribocytidylic acid (poly I:C ; a substitute for viral dsRNA and a ligand of toll-like receptor 3), enhances wound healing in vivo. The aim of this study is to improve our understanding of the link between innate immunity and human wound healing, particularly in re-epithelialization.

Results

The present study showed that poly I:C significantly accelerated collective HaCaT cell migration in a scratch assay. Poly I:C also increased IL-8 and bFGF production, and anti-IL-8 antibodies significantly inhibited the migration caused by poly I:C. Human recombinant IL-8 also accelerated collective HaCaT cell migration. An immunofluorescence assay and enzyme-linked immunosorbent assay (ELISA) also revealed that poly I:C decreased E-cadherin protein levels and increased vimentin protein levels, and anti-IL-8 antibody reversed this effect. In contrast, nucleic/cytosolic protein ratios of Snail 1 were unchanged in all tested conditions.

Conclusion

Our findings demonstrated that poly I:C accelerated collective HaCaT cell migration via autocrine/paracrine secretions of IL-8 and the subsequent incomplete epithelial-mesenchymal transition (EMT). Our findings provide a new strategy for wound healing by regulating innate immune systems in re-epithelialization.

Prevalence and Antimicrobial Resistance of Campylobacterjejuni and Campylobacter coli from Adult Hospitalized Patients with Diarrhea in Thailand

BACKGROUND

Infection with Campylobacter jejuni and C. coli are recognized as the major cause of bacterial gastroenteritis in humans.

METHODS

A total of 310 fecal samples collected from Thai adult patients with diarrhea in 2008 were screened for the presence of Campylobacter by PCR. Resistance to fluoroquinolone and macrolides of the detected Campylobacter strains were analyzed by studying the mutations in the gyrA and 23S rRNA genes, respectively.

RESULTS

Campylobacter species were detected in 4/310 (1.3%) of diarrheal patients, and C. jejuni was found in 3 of the 4 cases (75%). Fluoroquinolone resistance was noted in 2 cases (50%); however, no resistance to macrolides was observed.

CONCLUSIONS

Campylobacter was detected in a low prevalence in adult Thai patients hospitalized with diarrhea, and the resistance to fluoroquinolones is still a matter of concern in case antibiotic therapy is required.

Loop-Mediated Isothermal Amplification (LAMP) for Detection of Campylobacter jejuni and C. coli in Thai Children with Diarrhea

Campylobacter species are common causes of bacterial diarrhea, and Campylobacter jejuni and C. coli are known as the predominant causative agents in humans. Recent studies suggested that loop-mediated isothermal amplification (LAMP) is an efficient and practical tool for rapid detection of C. jejuni and C. coli in clinical samples. We used LAMP to screen 151 stool samples for Campylobacter; these samples were collected in 2012 from Thai children with diarrhea. The PCR method discriminated C. jejuni and C. coli among the detected Campylobacter strains; these species were subjected to sequencing of the hipO gene (in C. jejuni) or the ask gene (in C. coli). The results suggest that the prevalence of Campylobacter infection among Thai children with diarrhea is 8.6%, and C. jejuni is the most prevalent species.

Suppression of osteoblast Toll-like receptor 2 signaling by endothelin-1

Peripheral endothelin-1 (ET-1) levels are increased in chronic systemic disorders such as congestive cardiac failure, diabetes and chronic renal failure. Bone infections are also associated with poor prognoses in these conditions. In the present study, we examined the alterations in Toll-like receptor 2 (TLR2) signaling induced by ET-1 in an in vitro osteoblast cell model. The TLR2-positive murine osteoblast cell line MC3T3-E1 was treated with heat-killed Listeria monocytogenes (HKLM), a TLR2 ligand, in the presence or absence of ET-1. We examined TLR2 expression, intranuclear NF-κB phosphorylation and interleukin 6 (IL-6) production. ET-1 suppressed cell surface expression of TLR2, NF-κB phosphorylation and IL-6 production. As TLR2 represents an important mechanism by which osteoblasts recognize bacterial pathogens, a continuously elevated ET-1 status may impair pathogenic recognition by osteoblasts and consequently affect bone metabolism during infections.

Short communication: Drug resistance mutations in the HIV type 1 protease and reverse transcriptase genes in antiretroviral-naive Vietnamese children

Anti-HIV drugs have recently become available for the treatment of children infected with HIV in Vietnam; however, the genetic background of HIV-1 drug resistance in antiretroviral-naive children has yet to be studied. Of the 104 HIV-1 CRF01-AE subtype strains that were previously isolated from antiretroviral-naive children from the provinces of southern Vietnam and hospitalized in Children Hospital 1 in Ho Chi Minh City from 2004 to 2005, 79 strains were used for amplification and sequence analyses of the protease and reverse transcriptase (RT) genes. Minor mutations were found in the protease gene, including L10I, I13V, G16E, M36I, D60E, I62V, I64V, L63P, H69K, V82I, and I93L. Of these mutations, M36I and H69K were detected in all of the strains that were studied. However, all of the amino acid changes in the protease gene were considered to be polymorphisms. In the RT gene, three major mutations were detected in six strains: the V75M mutation in one strain, the Y181C mutation in two strains, and the M184I mutation in three strains. The prevalence of primary or transmitted HIV drug resistance to all of the drugs and drug classes that were evaluated in this study was 7.6%. These findings provide a useful background for antiretroviral therapy in Vietnam and contribute reference data for the surveillance of HIV drug resistance around the world. This study suggests that the prevalence of HIVDR in Vietnam may have recently increased. The monitoring of HIV drug resistance in Vietnam is necessary.