Rhizosphere bacterial exopolysaccharides: composition, biosynthesis, and their potential applications.

Bacterial exopolysaccharides (EPS) are biopolymers of carbohydrates, often released from cells into the extracellular environment. Due to their distinctive physicochemical properties, biocompatibility, biodegradability, and non-toxicity, EPS finds applications in various industrial sectors. However, the need for alternative EPS has grown over the past few decades as lactic acid bacteria's (LAB) low-yield EPS is unable to meet the demand. In this case, rhizosphere bacteria with the diverse communities in soil leading to variations in composition and structure, are recognized as a potential source of EPS applicable in various industries. In addition, media components and cultivation conditions have an impact on EPS production, which ultimately affects the quantity, structure, and biological functions of the EPS. Therefore, scientists are currently working on manipulating bacterial EPS by developing cultures and applying abiotic and biotic stresses, so that better production of exopolysaccharides can be attained. This review highlights the composition, biosynthesis, and effects of environmental factors on EPS production along with the potential applications in different fields of industry. Ultimately, an overview of potential future paths and tactics for improving EPS implementation and commercialization is pointed out.

Pregnant women with chronic hepatitis B virus infection at the assessment of tenofovir disoproxil fumarate prescription: Baseline characteristics of a prospective cohort study in Vietnam.

Objectives: We aimed to determine epidemiological characteristics and serologic markers among chronically hepatitis B virus (HBV)-infected pregnant women during the assessment of tenofovir disoproxil fumarate (TDF) prescription in Vietnam. Methods: We consecutively recruited 375 pregnant women with chronic HBV (cHBV) infection at week 25±2 of pregnancy, at which time they were assessed for TDF use as pre-prophylaxis and/or pre-treatment at the Hospital for Tropical Diseases in southern Vietnam during December 2019-April 2021. Demographic characteristics, serological biomarkers, and prenatal liver ultrasounds were obtained through interviews and reviews of medical records. Results: The median age of pregnant women was 29 years (interquartile range: 26-32). More than half of pregnant women (208/375; 55.5%) started TDF for prevention of mother-to-child transmission of HBV and/or treatment of chronic hepatitis B (CHB). Among the pregnant women initiating TDF, 96.1% (198/206) tested positive for hepatitis B e antigen, and 21.6% (45/208) had quantitative hepatitis B surface antigen (qHBsAg) ≤104 IU/mL. A relatively strong correlation between qHBsAg and HBV deoxyribonucleic acid (DNA) (r = 0.81; 95% CI: 0.76-0.85) was observed in pregnant women starting TDF. Conclusions: Our results demonstrate the high need for TDF prescription for prevention and/or treatment purposes in pregnant women with cHBV infection. Pregnant women with qHBsAg levels ≤104 IU/mL may prioritize HBV DNA testing over qHBsAg to decide on TDF prescription.

Kinetics of neutralising antibodies against Omicron variant in Vietnamese healthcare workers after primary immunisation with ChAdOx1-S and booster with BNT162b2

We studied the development and persistence of neutralising antibodies against SARS-CoV-2 ancestral strain, and Delta and Omicron (BA.1 and BA.2) variants in Vietnamese healthcare workers (HCWs) up to 15 weeks after booster vaccination. We included 47 HCWs with different pre-existing immune statuses (group 1 (G1): n=21, and group 2 (G2): n=26 without and with prior breakthrough Delta variant infection, respectively). The study participants had completed primary immunisation with ChAdOx1-S and booster vaccination with BNT162b2. Neutralising antibodies were measured using a surrogate virus neutralisation assay. Of the 21 study participants in G1, neutralising antibodies against ancestral strain, Delta variant, BA.1 and BA.2 were (almost) abolished at month 8 after the second dose, but all had detectable neutralising antibodies to the study viruses at week two post booster dose. Of the 26 study participants in G2, neutralising antibody levels to BA.1 and BA.2 were significantly higher than those to the corresponding viruses measured at week 2 post breakthrough infection and before the booster dose. At week 15 post booster vaccination, neutralising antibodies to BA.1 and BA.2 dropped significantly, with more profound changes observed in those without breakthrough Delta variant infection. Booster vaccination enhanced neutralising activities against ancestral strain and Delta variant, as compared to those induced by primary vaccination. These responses were maintained at high levels for at least 15 weeks. Our findings emphasise the importance of the first booster dose in producing cross-neutralising antibodies against Omicron variant. A second booster dose might be needed to maintain long-term protection against Omicron variant.

Immunogenicity of Oxford-AstraZeneca COVID-19 vaccine in Vietnamese healthcare workers

We studied the immunogenicity of Oxford-AstraZeneca vaccine in Vietnamese healthcare workers. We collected blood samples before each dose, at 14 days after each dose, and month 1 and 3 after dose 1 from each participant alongside demographics data. We measured neutralizing antibodies using a surrogate virus neutralization assay. The 554 study participants (136 males and 418 females) were aged between 22-71 years (median: 36 years). 104 and 94 out of 144 selected participants were successfully followed up at 14 days after dose 2 and 3 months after dose 1, respectively. Neutralizing antibodies increased after each dose, with the sero-conversion rate reaching 98.1% (102/104) at 14 days after dose 2. At month 3 after dose 1, neutralizing antibody levels decreased, while 94.7% (89/94) of the study participants remained seropositive. Oxford-AstraZeneca COVID-19 vaccine is immunogenic in Vietnamese healthcare workers. The requirement for a third dose warrants further research.

Biparatopic single-domain antibodies against Axl achieve ultra-high affinity through intramolecular engagement.

Overexpression of Axl, a TAM-family receptor tyrosine kinase, plays key roles in the formation, growth, and spread of tumors as well as resistance to targeted therapies and chemotherapies. We identified novel llama VHHs against human Axl using multiple complementary phage display selection strategies and characterized a subset of high-affinity VHHs. The VHHs targeted multiple sites in Ig-like domains 1 and 2 of the Axl extracellular domain, including an immunodominant epitope overlapping the site of Gas6 interaction and two additional non-Gas6 competitive epitopes recognized by murine monoclonal antibodies. Only a subset of VHHs cross-reacted with cynomolgus monkey Axl and none recognized mouse Axl. As fusions to human IgG1 Fc, VHH-Fcs bound Axl+ tumor cell lines and mertansine-loaded VHH-Fcs were cytotoxic in vitro against Axl+ cells in proportion to their binding affinities. Engineered biparatopic VHH-VHH heterodimers bound Axl avidly, and a subset of molecules showed dramatically enhanced association rates indicative of intramolecular binding. These VHHs may have applications as modular elements of biologic drugs such as antibody-drug conjugates.

Adopting open access in the social sciences and humanities: evidence from a developing nation.

Open Access (OA) publishing, with ambitious movements such as Plan S, is engendering radical changes among academic publishers. Emerging countries need to keep publishing as well as adopt open access to catch up with the changes. Using exclusive data from the Social Sciences & Humanities Peer Awards (SSHPA) database, the study employed both descriptive statistics and a Bayesian linear regression model to examine the journals and publishers in which Vietnamese social scientists published during the period 2008-2019, and the potential of pursuing the OA movement in Vietnam. We found an increasing diversification in the publishing sources of Vietnamese social science researchers with growth rates of 9.8% and 14.1% per annum in the number of publishers and journals, respectively. Given that the proportion of Gold OA articles had a fourfold increase over the examined period, it seems that the Vietnamese academic community is adopting OA. Furthermore, Bayesian analysis results hint at positive associations of internal and external collaborative power (number of domestic and foreign authors, respectively) with the decision to publish in OA (ß b_TotalVN_OpenAccess = 0.22; ß b_TotalForeign_OpenAccess = 0.15). The results and its implications suggest that Vietnamese policymakers and university director boards should facilitate as well as control the quality of the scientific publishing and the OA movement.

SARS-CoV-2 detection in nasopharyngeal throat swabs by metagenomics

Metagenomics could detect SARS-CoV-2 in all eight nasopharyngeal/throat swabs with high/low viral loads, and rhinovirus in a co-infected patient. The sequenced viruses belonged to lineage B1. Because metagenomics could detect novel pathogen and co-infection, and generate sequence data for epidemiological investigation, it is an attractive approach for infectious-disease diagnosis.

The natural history and transmission potential of asymptomatic SARS-CoV-2 infection

BackgroundLittle is known about the natural history of asymptomatic SARS-CoV-2 infection or its contribution to infection transmission. MethodsWe conducted a prospective study at a quarantine centre for COVID-19 in Ho Chi Minh City, Vietnam. We enrolled quarantined people with RT-PCR-confirmed SARS-CoV-2 infection, collecting clinical data, travel and contact history, and saliva at enrolment and daily nasopharyngeal throat swabs (NTS) for RT-PCR testing. We compared the natural history and transmission potential of asymptomatic and symptomatic individuals. ResultsBetween March 10th and April 4th, 2020, 14,000 quarantined people were tested for SARS-CoV-2; 49 were positive. Of these, 30 participated in the study: 13(43%) never had symptoms and 17(57%) were symptomatic. 17(57%) participants acquired their infection outside Vietnam. Compared with symptomatic individuals, asymptomatic people were less likely to have detectable SARS-CoV-2 in NTS samples collected at enrolment (8/13 (62%) vs. 17/17 (100%) P=0.02). SARS-CoV-2 RNA was detected in 20/27 (74%) available saliva; 7/11 (64%) in the asymptomatic and 13/16 (81%) in the symptomatic group (P=0.56). Analysis of the probability of RT-PCR positivity showed asymptomatic participants had faster viral clearance than symptomatic participants (P<0.001 for difference over first 19 days). This difference was most pronounced during the first week of follow-up. Two of the asymptomatic individuals appeared to transmit the infection to up to four contacts. ConclusionsAsymptomatic SARS-CoV-2 infection is common and can be detected by analysis of saliva or NTS. NTS viral loads fall faster in asymptomatic individuals, but they appear able to transmit the virus to others.

Infants Understand Others' Needs.

Infants begin to help other individuals in the second year of life. However, it is still unclear whether early helping behavior is based on an understanding of other individuals' needs and is thus motivated prosocially. In the present eye-tracking study, 9- to 18-month-old infants (N= 71) saw a character in need of help, unable to reach its goal because of an obstacle, and a second character that was able to achieve a goal on its own. When a third individual (a helper) initiated an action, the infants expected the helper to help the character in need (as indicated during the anticipatory-looking and violation-of-expectation phases). Their prosocial understanding did not differ between age groups and was not related to their helping behavior (measured in two behavioral tasks). Thus, infants understand other individuals' needs even before they start to help others themselves. This indicates that early helping may indeed be motivated prosocially and raises the question of which other competences underlie the ontogeny of helping behavior.

Molecular targeting of CEACAM6 using antibody probes of different sizes.

Carcinocinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is overexpressed in a number of human malignancies, especially in pancreatic cancer. It has been demonstrated that CEACAM6 is a potential target for monoclonal antibody (mAb) therapy with a safe therapeutic index. Here, we labeled three anti-CEACAM6 antibodies of different sizes, including a single-domain antibody 2A3 (16 kDa), a heavy chain antibody 2A3-mFc (80 kDa) and a full length antibody 9A6 (150 kDa), with 64Cu to image CEACAM6 expression in a xenografted pancreatic tumor model. For positron emission tomography (PET) imaging, the tumor mice were intravenously injected with 64Cu-DOTA-antibodies and static scans were obtained at 5 min, 0.5, 1, 2, 4, 8 and 24h post-injection (p.i.). All three antibodies showed strong CEACAM6 binding. Ex vivo immunostaining on tumor sections at 24 h after Ab injection demonstrated specific tumor targeting of both 2A3-mFc and 9A6. 64Cu-DOTA-2A3 showed fast BxPC3 tumor uptake and rapid whole-body clearance. At 24 h p.i., the tumor uptakes were 98.2±6.12%ID/g for 64Cu-DOTA-2A3-mFc and 57.8±3.73%ID/g for 64Cu-DOTA-9A6, respectively. Compared with the full length antibody 9A6, the heavy chain antibody 2A3-mFc showed higher tumor uptake, lower liver uptake and shorter circulation half-life. All the data supported that the heavy chain antibody 2A3-mFc is superior to the single domain antibody and the full-length antibody with regard to tumor detection and pharmacokinetics, which has great potential to be developed for CEACAM6-targeted pancreatic cancer imaging and therapy.

Isolation of functional single domain antibody by whole cell immunization: implications for cancer treatment.

Carcinoembryonic antigen related cell adhesion molecule (CEACAM) 6 is over-expressed in different types of cancer cells. In addition, it has also been implicated in some infectious diseases. Targeting this molecule by an antibody might have applications in diverse tumor models. Single domain antibody (sdAb) is becoming very useful format in antibody engineering as potential tools for treating acute and chronic disease conditions such as cancer for both diagnostic as well as therapeutic application. Generally, sdAbs with good affinity are isolated from an immune library. Discovery of a new target antigen would require a new immunization with purified antigen which is not always easy. In this study, we have isolated, by phage display, an sdAb against CEACAM6 with an affinity of 5 nM from a llama immunized with cancer cells. The antibody has good biophysical properties, and it binds to the cells expressing the target antigen. Furthermore, it reduces cancer cells proliferation in vitro and shows an excellent tumor targeting in vivo. This sdAb could be useful in diagnosis as well as therapy of CEACAM6 expressing tumors. Finally, we envisage it would be feasible to isolate good sdAbs against other interesting tumor associated antigens from this library. Therefore, this immunization method could be a general strategy for isolating sdAbs against any surface antigen without immunizing the animal with the antigen of interest each time.

Improving solubility and refolding efficiency of human V(H)s by a novel mutational approach.

The antibody V(H) domains of camelids tend to be soluble and to resist aggregation, in contrast to human V(H) domains. For immunotherapy, attempts have therefore been made to improve the properties of human V(H)s by camelization of a small set of framework residues. Here, we have identified through sequence comparison of well-folded llama V(H) domains an alternative set of residues (not typically camelid) for mutation. Thus, the solubility and thermal refolding efficiency of a typical human V(H), derived from the human antibody BT32/A6, were improved by introduction of two mutations in framework region (FR) 1 and 4 to generate BT32/A6.L1. Three more mutations in FR3 of BT32/A6.L1 further improved the thermal refolding efficiency while retaining solubility and cooperative melting profiles. To demonstrate practical utility, BT32/A6.L1 was used to construct a phage display library from which were isolated human V(H)s with good antigen binding activity and solubility. The engineered human V(H) domains described here may be useful for immunotherapy, due to their expected low immunogenicity, and in applications involving transient high temperatures, due to their efficient refolding after thermal denaturation.

A pentavalent single-domain antibody approach to tumor antigen discovery and the development of novel proteomics reagents.

Proteomics research has delivered many novel tumor targets. However, due to key limitations, it does not specifically identify targets that are most accessible for drug delivery, such as cell-surface antigens. A novel tumor antigen discovery platform based on screening a single domain antibody (sdAb) library against tumor cells and subsequently identifying the corresponding antigens of the isolated antibodies is described. An sdAb, AFAI, specific for non-small cell lung carcinoma (A549 cell line) was isolated from a phage library derived from the heavy chain antibody repertoire of a llama. The homopentamerization property of a non-toxic verotoxin B-subunit was exploited to make the ES1 pentabody, a pentameric form of AFAI. Pentamerization improved the binding of the AFAI to A549 cells dramatically and greatly facilitated antigen identification by a Western blotting/mass spectrometry approach. The antigen of ES1, which is present only in the hydrophobic, not in the hydrophilic, fraction of A549 cellular proteins, was identified as carcinoembryonic antigen-related cell adhesion molecule 6 (CEA6). CEA6 was observed to be acidic and highly glycosylated, and to exist in multiple glycoforms. The results show that the platform described here should find wide application in antigen discovery, and demonstrated that the pentabodies are very useful immunological reagents for proteomics.

Endothelin B receptor-mediated regulation of endothelin-1 content and release in cultured porcine aorta endothelial cell.

Several cardiovascular diseases are associated with an increase in circulating levels of endothelin-1 (ET-1). Little is known about the consequences of this increase on endothelial cell responses with respect to ET-1 production and regulation. Confluent, passage 1, cultured porcine aorta endothelial cells were exposed to exogenous ET-1 (0.1 microM) for 24 h. BQ788 (1 microM, ETB receptor antagonist) but not BQ123 (1 microM, ETA receptor antagonist) significantly (p < 0.05) reduced 125I-ET-1 uptake. The effects of BQ788 were mimicked by dansylcadaverine (0.5 mM) but not nystatin (50 microg/ml). Immunoreactive ET-1 endothelial cell content doubled (p < 0.05) after 24 h of exogenous ET-1 treatment. Bosentan (10 microM, dual ETA/B receptor antagonist) reduced (p < 0.05) immunoreactive ET-1 content in control cells. Bosentan prevented exogenous ET-1-induced endothelial cell ET-1 loading, suggesting that exogenous ET-1 is partly recycled. PreproET-1 mRNA levels were reduced (p < 0.05) by exogenous ET-1 after 24 h, an effect blocked by BQ788 and bosentan. When used alone, both receptor antagonists increased mRNA levels. The results of this study suggest that part of ET-1 is recycled through ETB receptors and subsequently released to contribute to constitutive ET-1 overflow. ET-1 exerts a negative feedback on ET-1 gene transcription, which is dependent on ETB receptor activation and internalization of the complex ET-1/ETB receptor. The maintenance of this negative regulatory loop of ET-1 production may be essential for the normal endothelial physiology.