Importation and Circulation of Vaccine-Derived Poliovirus Serotype 2, Senegal, 2020–2021

Environmental surveillance for poliovirus is increasingly used in poliovirus eradication efforts as a supplement to acute flaccid paralysis (AFP) surveillance. Environmental surveillance was officially established in 2017 in Senegal, where no poliovirus had been detected since 2010. We tested sewage samples from 2 sites in Dakar monthly for polioviruses. We identified a vaccine-derived poliovirus serotype 2 on January 19, 2021, from a sample collected on December 24, 2020; by December 31, 2021, we had detected 70 vaccine-derived poliovirus serotype 2 isolates circulating in 7 of 14 regions in Senegal. Sources included 18 AFP cases, 20 direct contacts, 17 contacts in the community, and 15 sewage samples. Phylogenetic analysis revealed the circulation of 2 clusters and provided evidence on the virus introduction from Guinea. Because novel oral polio vaccine serotype 2 was used for response activities throughout Senegal, we recommend expanding environmental surveillance into other regions.     

The Role of Food Insecurity and Dietary Diversity on Recovery from Wasting among Hospitalized Children Aged 6–23 Months in Sub-Saharan Africa and South Asia

Background: Current guidelines for the management of childhood wasting primarily focus on the provision of therapeutic foods and the treatment of medical complications. However, many children with wasting live in food-secure households, and multiple studies have demonstrated that the etiology of wasting is complex, including social, nutritional, and biological causes. We evaluated the contribution of household food insecurity, dietary diversity, and the consumption of specific food groups to the time to recovery from wasting after hospital discharge. Methods: We conducted a secondary analysis of the Childhood Acute Illness Network (CHAIN) cohort, a multicenter prospective study conducted in six low- or lower-middle-income countries. We included children aged 6–23 months with wasting (mid-upper arm circumference [MUAC] ≤ 12.5 cm) or kwashiorkor (bipedal edema) at the time of hospital discharge. The primary outcome was time to nutritional recovery, defined as a MUAC > 12.5 cm without edema. Using Cox proportional hazards models adjusted for age, sex, study site, HIV status, duration of hospitalization, enrollment MUAC, referral to a nutritional program, caregiver education, caregiver depression, the season of enrollment, residence, and household wealth status, we evaluated the role of reported food insecurity, dietary diversity, and specific food groups prior to hospitalization on time to recovery from wasting during the 6 months of posthospital discharge. Findings: Of 1286 included children, most participants (806, 63%) came from food-insecure households, including 170 (13%) with severe food insecurity, and 664 (52%) participants had insufficient dietary diversity. The median time to recovery was 96 days (18/100 child-months (95% CI: 17.0, 19.0)). Moderate (aHR 1.17 [0.96, 1.43]) and severe food insecurity (aHR 1.14 [0.88, 1.48]), and insufficient dietary diversity (aHR 1.07 [0.91, 1.25]) were not significantly associated with time to recovery. Children who had consumed legumes and nuts prior to diagnosis had a quicker recovery than those who did not (adjusted hazard ratio (aHR): 1.21 [1.01,1.44]). Consumption of dairy products (aHR 1.13 [0.96, 1.34], p = 0.14) and meat (aHR 1.11 [0.93, 1.33]), p = 0.23) were not statistically significantly associated with time to recovery. Consumption of fruits and vegetables (aHR 0.78 [0.65,0.94]) and breastfeeding (aHR 0.84 [0.71, 0.99]) before diagnosis were associated with longer time to recovery. Conclusion: Among wasted children discharged from hospital and managed in compliance with wasting guidelines, food insecurity and dietary diversity were not major determinants of recovery.     

Microfluidic study of retention and elimination of abnormal red blood cells by human spleen with implications for sickle cell disease

The spleen clears altered red blood cells (RBCs) from circulation, contributing to the balance between RBC formation (erythropoiesis) and removal. The splenic RBC retention and elimination occur predominantly in open circulation where RBCs flow through macrophages and inter-endothelial slits (IESs). The mechanisms underlying and interconnecting these processes significantly impact clinical outcomes. In sickle cell disease (SCD), blockage of intrasplenic sickled RBCs is observed in infants splenectomized due to acute splenic sequestration crisis (ASSC). This life-threatening RBC pooling and organ swelling event is plausibly triggered or enhanced by intra-tissular hypoxia. We present an oxygen-mediated spleen-on-a-chip platform for in vitro investigations of the homeostatic balance in the spleen. To demonstrate and validate the benefits of this general microfluidic platform, we focus on SCD and study the effects of hypoxia on splenic RBC retention and elimination. We observe that RBC retention by IESs and RBC–macrophage adhesion are faster in blood samples from SCD patients than those from healthy subjects. This difference is markedly exacerbated under hypoxia. Moreover, the sickled RBCs under hypoxia show distinctly different phagocytosis processes from those non-sickled RBCs under hypoxia or normoxia. We find that reoxygenation significantly alleviates RBC retention at IESs, and leads to rapid unsickling and fragmentation of the ingested sickled RBCs inside macrophages. These results provide unique mechanistic insights into how the spleen maintains its homeostatic balance between splenic RBC retention and elimination, and shed light on how disruptions in this balance could lead to anemia, splenomegaly, and ASSC in SCD and possible clinical manifestations in other hematologic diseases.

The human spleen is a unique organ that plays an important role in our immune and circulatory systems. The spleen is composed primarily of two distinct functional regions, the red pulp and the white pulp, which are intermingled by the marginal/perifollicular zone (1). It contains complex vascular pathways involving direct and indirect connections. Direct connections exist between the fast perifollicular microcirculation and venous sinuses drained in splenic veins (“closed circulation”), whereas indirect connections exist between red pulp arterioles and veins through the reticular meshwork (“open circulation”) and across the wall of sinuses (1). As much as about 80% of the spleen parenchyma is populated with the red pulp, which mainly comprises the vascular sinuses and cords of Billroth (1, 2). Approximately 3 to 10% of blood from cardiac output flows through the spleen, and about 10% of splenic inflow passes through slow open circulation in the red pulp (1, 3–5).Splenic filtration of abnormal red blood cells (RBCs) is predominately performed in the open circulation, through macrophage-rich zones (M-filter) and across splenic inter-endothelial slits (IESs) in the wall of sinuses (S-filter), as shown in Fig. 1A. The specialized elongated shape of littoral cells in the splenic sinuses and their three-dimensional (3D) barrel-like structure impose sub-micrometer scale physical barriers or constraints on RBCs navigating the open circulation (6). Prior to returning to the systemic circulation through the IESs across the spleen, circulating RBCs are checked for surface integrity by a scattered collection of resident macrophages (7). These two structural and functional spleen filters, S-filter and M-filter (Fig. 1B), sustain the remarkable capacity of the spleen to retain and destroy abnormal RBCs. Consequently, they contribute to the fine balance between RBC production in the bone marrow and the removal of abnormal RBCs from the blood circulation (1).Open in a separate windowFig. 1.Splenic filtration of altered RBCs. (A) Schematic diagram of blood circulation through splenic red pulp, including closed circulation and open circulation. The splenic filtration of altered RBCs is achieved in the open circulation in the red pulp, through macrophages (M-filter) and the splenic IESs (S-filter). (B) Schematic diagram of the oxygen gradient near the sinus. The two structural and functional spleen filters, the S-filter and M-filter, respectively, are modeled in vitro using the S-Chip and M-Chip, respectively. Created with BioRender.com.Healthy human RBCs (AA RBCs) have an average life span of 100 to 120 d (8), indicating that about 1% of the RBCs are recycled each day by the human body (9). Senescent RBCs typically have reduced deformability (10) and send signals to macrophages by expressing higher phosphatidylserine (PS), higher band-3, and reduced CD47 levels (11, 12), on their external cell surface. Senescent RBCs could exhibit a higher propensity to be sequestered at the IESs due to their reduced deformability and then cleared by macrophages, or trapped by adhesion and phagocytosed in the meshwork (13). Here, a balance between RBC retention rate and RBC elimination rate (by post-retention processing) should be dynamically maintained to ascertain homeostasis. Such homeostatic balance, however, can be severely disrupted due to hemolytic disorders, resulting in serious, and sometimes life-threatening, complications such as splenomegaly and/or hypersplenism (14). As a result, the RBC retention rate can significantly surpass the RBC post-retention elimination rate in the spleen. It is, therefore, important to investigate systematically and quantitatively both the RBC retention rate and the elimination rate in the spleen, and to compare their relative changes, as a function of disease state, with the baseline condition of healthy hemostasis.The spleen is generally in a hypoxic (low oxygen level) condition owing to its slow and open blood circulation in the red pulp (see the brief review of splenic oxygen level and transit time/velocity of RBCs in SI Appendix, Table S2). An oxygen gradient exists in the spleen from locations nearest to the arteriolar end of capillaries to the distal locations in the proximity of the IESs, as shown schematically in Fig. 1B (15). Under normal circumstances, hypoxia is mild due to continuous oxygen delivery by the RBCs through splenic circulation. However, it deepens with the reduction in oxygen delivery arising from the obstruction of RBC flow or anemia in many hemolytic blood disorders. For instance, in sickle cell disease (SCD), such obstruction/anemia-induced local hypoxia may in turn trigger sickling of homozygous sickle cell disease (HbSS) RBCs (SS RBCs) and subsequently lead to further reduction in deformability and increase in the expression of adhesion molecules (16, 17). Therefore, sickled RBCs have a higher propensity to be retained by the venous sinuses as well as cords of Billroth, thereby contributing further to a reduction in the oxygen level in the spleen (18). The splenic retention of SS RBCs depends on a trade-off between the local oxygen level (which determines the sickling kinetics) and the transit time of RBCs through the spleen (19). Excessive retention of stiff and sickled SS RBCs in the patient’s spleen has been considered a dominant cause of acute splenic sequestration crisis (ASSC), a life-threatening complication, in SCD (17, 20, 21). This process might involve a vicious cycle: the more RBCs the spleen traps, the larger the spleen grows, and the larger the spleen grows, the deeper the hypoxia is, resulting in more and more sickled SS RBCs that are consequently being trapped and destroyed. Indeed, following splenectomy in young SCD children with still functional spleen, sickled RBCs have been found retained and congested upstream of IESs during ASSC (17, 22, 23). On the other hand, surface modulations such as PS externalization (24), decreased levels of CD47 (25), and elevated binding of autologous immunoglobulin (26), as well as increased membrane rigidity of sickled RBCs may also promote the retention and elimination of SS RBCs by the splenic macrophages (27–29). From these considerations, we postulate that both increased mechanical retention and hyperactive phagocytosis elimination of abnormal RBCs can exacerbate significantly under some extreme conditions such as hypoxia in SCD. These factors could, in turn, play a key role in disrupting the homeostatic balance thereby causing spleen dysfunction in hemolytic disorders.Recent in vitro studies based on microfluidic spleen-on-a-chip platforms, which simulate the micro-constrictions of IESs and hydrodynamic conditions, have advanced the functional study of RBC filtration in the spleen (30–33). However, to our knowledge, no prior in vitro assays have effectively integrated a controlled gaseous microenvironment within a microfluidic system to enable the quantitative investigation of the hypoxic effect on splenic retention and post-retention elimination of RBCs, especially for SS RBCs. Moreover, there is a compelling need for an in vitro assay that elucidates the mechanisms underlying the interaction of RBCs with splenic phagocytes during the low-velocity microcirculation through the red pulp. Most existing erythrophagocytosis (RBC elimination) assays measure phagocytic activity in a static condition, which does not faithfully replicate in vivo conditions (27, 28). To this end, the development and validation of an oxygen-mediated in vitro assay for investigating the kinetics of both splenic retention of RBCs and erythrophagocytosis under hypoxia are critically needed for a better understanding of the mechanisms responsible for splenic functions in physiology and disease.Here we present a general microfluidic platform to systematically probe the retention and elimination functions undertaken by IESs and macrophages in the human spleen, by developing and validating two functional modules of an oxygen-mediated spleen-on-a-chip. This platform entails the S-Chip and the M-Chip, which model the S-filter for RBC retention through splenic IESs and the M-filter for RBC adhesion and elimination by splenic resident macrophages, respectively. While the microfluidic platform and assays presented in this work can, by design, potentially provide mechanistic insights into a wide spectrum of hereditary and acquired human diseases, we focus particular attention here on the study of homeostatic processes in SCD. We make comparisons with healthy subjects as a negative control group. We additionally use heated AA RBCs as a positive control, while considering it as a generic model for exploring different controlled concentrations of altered RBCs in hemolytic disorders. We demonstrate that our microfluidic platform can also be used to mimic in vitro the two major components of the spleen filtering unit, namely surface sensing by macrophages and mechanical sensing by splenic IESs under controlled oxygen pressure. We further show that this approach enables systematic investigations of the cellular mechanisms underlying anemia and ASSC in SCD, while also providing potential pathways to explore, with appropriate modifications, splenomegaly and hypersplenism in other diseases such as Plasmodium falciparum malaria.     

Mandibular fractures in children. Apropos of 20 cases]

Authors report their experiences about the caring for child mandible fractures at Yalgado Ouedraogo University Hospital Centre, CHUYO. These fractures constitute day-to-day relative immediate emergencies. The techniques of retention used after bone setting are various. Ligatures with steel thread are frequently used. The retention is shortened because of the quick strengthening noticed in child. The satisfying results reveal the necessity of classical retention and ligatures with steel thread in jawbone fractures.     

Adiponectin suppression of high-glucose-induced reactive oxygen species in vascular endothelial cells: evidence for involvement of a cAMP signaling pathway

Adiponectin is an abundant adipocyte-derived plasma protein with antiatherosclerotic effects. Vascular signal transduction by adiponectin is poorly understood and may involve 5'-AMP-activated protein kinase (AMPK), cAMP signaling, and other pathways. Hyperglycemia sharply increases the production of reactive oxygen species (ROS), which play a key role in endothelial dysfunction in diabetes. Because the recombinant globular domain of human adiponectin (gAd) reduces the generation of endothelial ROS induced by oxidized LDL, we sought to determine whether adiponectin could also suppress ROS production induced by high glucose in cultured human umbilical vein endothelial cells. Incubation in 25 mmol/l glucose for 16 h increased ROS production 3.8-fold (P<0.05), using a luminol assay. Treatment with gAd for 16 h suppressed glucose-induced ROS in a dose-dependent manner up to 81% at 300 nmol/l (P<0.05). The AMPK activator 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR; 1 mmol/l, 16 h) only partially decreased glucose-induced ROS by 22% (P<0.05). Cell pretreatment with AMPK inhibitors, however, failed to block the effect of gAd to suppress glucose-induced ROS, suggesting that the action of gAd was independent of AMPK. Interestingly, activation of cAMP signaling by treatment with forskolin (2 micromol/l) or dibutyryl-cAMP (0.5 mmol/l) reduced glucose-induced ROS generation by 43 and 67%, respectively (both P<0.05). Incubation with the cAMP-dependent protein kinase (PKA) inhibitor H-89 (1 micromol/l) fully abrogated the effect of gAd, but not that of AICAR, on ROS induced by glucose. gAd also increased cellular cAMP content by 70% in an AMPK-independent manner. Full-length adiponectin purified from a eukaryotic expression system also suppressed ROS induced by high glucose or by treatment of endothelial cells with oxidized LDL. Thus, adiponectin suppresses excess ROS production under high-glucose conditions via a cAMP/PKA-dependent pathway, an effect that has implications for vascular protection in diabetes.     

Longitudinal assessment of HIV-1 and HSV-2 shedding in the genital tract of West African women

Forty-two HSV-2-seropositive women, of whom 22 were HIV-1 seropositive, were followed up weekly for 3 weeks for assessment of HIV-1 and HSV-2 genital shedding in Bobo Dioulasso, Burkina Faso. HSV-2 DNA and HIV-1 RNA were quantitated in cervicovaginal lavages enriched with a cervical swabbing (eCVL) using real-time polymerase chain reaction. HIV-1 RNA shedding was detected in eCVL from 19 of 22 (86.4%) of the HIV-1-seropositive women and HSV-2 DNA was detected in eCVL from 12 of 42 (28.6%) of the women. Compared with the HIV-1-seronegative women, the HIV-1-seropositive women showed more persistent HSV-2 genital shedding and higher HSV-2 DNA loads in eCVL. This study showed that eCVL is a reliable sampling method for detecting both viruses. Three measurement points (at weekly intervals in this study) seem to adequately allow detection of most HIV-1 or HSV-2 genital shedders.