Non–antigen-contacting region of an asymmetric bispecific antibody to factors IXa/X significantly affects factor VIII-mimetic activity

While antibody engineering improves the properties of therapeutic antibodies, optimization of regions that do not contact antigens has been mainly focused on modifying the effector functions and pharmacokinetics of antibodies. We recently reported an asymmetric anti-FIXa/FX bispecific IgG₄ antibody, ACE910, which mimics the cofactor function of FVIII by placing the two factors into spatial proximity for the treatment of hemophilia A. During the optimization process, we found that the activity was significantly affected by IgG subclass and by modifications to the inter-chain disulfide bonds, upper hinge region, elbow hinge region, and Fc glycan, even though these regions were unlikely to come into direct contact with the antigens. Of these non–antigen-contacting regions, the tertiary structure determined by the inter-chain disulfide bonds was found to strongly affect the FVIII-mimetic activity. Interestingly, IgG₄-like disulfide bonds between Cys131 in the heavy chain and Cys114 in the light chain, and disulfide bonds between the two heavy chains at the hinge region were indispensable for the high FVIII-mimetic activity. Moreover, proline mutations in the upper hinge region and removal of the Fc glycan enhanced the FVIII-mimetic activity, suggesting that flexibility of the upper hinge region and the Fc portion structure are important for the FVIII-mimetic activity. This study suggests that these non–antigen-contacting regions can be engineered to improve the biological activity of IgG antibodies with functions similar to ACE910, such as placing two antigens into spatial proximity, retargeting effector cells to target cells, or co-ligating two identical or different antigens on the same cell.     

Serum antibodies against Toxoplasma gondii and Neospora caninum in southeast Queensland dugongs

The dugong (Dugong dugon) is an herbivorous marine mammal that inhabits tropical inshore waters and thus may be vulnerable to pollutants and terrestrial pathogens as a result of coastal runoff. In this study, serum samples collected from live, wild dugongs (n = 114) in an embayment located on the urbanized southeast Queensland coast of Australia during 2008–2014, were measured for IgG antibody levels specific to Toxoplasma gondii and Neospora caninum. An ELISA used to measure T. gondii tachyzoite antibodies indicated a non-Gaussian distribution of antibody level, with five dugongs identified as high outliers. Mean levels of antibodies specific for T. gondii in dugongs sampled in 2014 were significantly higher than in 2010 (p = .006) and 2011 (p = .009) with an elevation in mean antibody levels after a major 2011 flood event relative to antibody levels prior to the flood (p < .0001). A competitive ELISA to detect N. caninum antibody indicated a normal distribution of antibody with no high outliers. Mean antibody level for N. caninum was highest in 2012 and declined significantly in 2014 (p = .004). This is the first survey of antibodies directed against T. gondii and N. caninum in dugongs and suggests future health monitoring of this species.     

Autoimmunity and immune system dysregulation in schizophrenia: IgGs from sera of patients hydrolyze myelin basic protein

Several different theories of schizophrenia (SCZ) were discussed; the causes of this disease are not yet clear. Using ELISA, it was shown that titers of autoantibodies against myelin basic protein (MBP) in SCZ patients are ~1.8‐fold higher than in healthy individuals but 5.0‐fold lower than in patients with multiple sclerosis. Several rigid criteria were checked to show that the MBP‐hydrolyzing activity is an intrinsic property of SCZ IgGs. Approximately 82% electrophoretically homogeneous SCZ IgGs purified using several affinity sorbents including Sepharose with immobilized MBP hydrolyze specifically only MBP but not many other tested proteins. The average relative activity of IgGs from patients with negative symptoms was 2.5‐fold higher than that of patients with positive symptoms of SCZ, and it increases with the duration of this pathology. It was shown that abzymes are the earliest statistically significant markers of many autoimmune pathologies. Our findings surmise that the immune systems of individual SCZ patients can generate a variety of anti‐MBP abzymes with different catalytic properties, which can attack MBP of the myelin‐proteolipid shell of axons. Therefore, autoimmune processes together with other mechanisms can play an important role in SCZ pathogenesis. MBP‐hydrolyzing antibodies were previously detected in the blood of 80% to 90% of patients with systemic lupus erythematosus (SLE) and multiple sclerosis (MS). In addition, some similar neuropsychiatric indicators of disease common to SLE, MS, and SCZ were described in the literature. Thus, the destruction of the myelin sheath and the production of MBP‐hydrolyzing antibodies can be a common phenomenon for some different diseases.     

Violacein improves recombinant IgG production by controlling the cell cycle of Chinese hamster ovary cells

Cytotechnology - Chinese hamster ovary (CHO) cells are used as host cells for industrial monoclonal antibody (mAb) production. Cell cycle control is an effective approach to increase mAb production...     

Plant CSR types in the north: comparing the morphological and morpho-physiological approaches

Grime’s competition–stress–ruderal (CSR) theory is widely used to study plant species’ responses to multiple environmental factors. We compared two models to allocate CSR types the global “StrateFy” model (Pierce et al. Funct Ecol, 31:444–457, 2017) and a locally developed morpho-physiological model (Novakovskiy et al. Int J Ecol, p e1323614, 2016). The “StrateFy” model is based on three morphological leaf traits: leaf area (LA), leaf dry matter content (LDMC) and specific leaf area (SLA). The morpho-physiological model additionally uses plant height (PH), leaf dry weight (LDW), photosynthetic capacity (PN) and respiration rate (RD), leaf nitrogen, and carbon concentration (LNC, LCC). We applied both models to 74 plant species, the traits of which were measured at mountain (Northern Urals) and plane (Komi Republic, Russia) landscapes of European Northeast. The comparison of the calculated C, S, and R scores showed two groups of species with large and unidirectional differences. The first group consists of species with a shift from S (morpho-physiological model) to CR (StrateFy model) strategy. Species of this group are typical for deep shaded habitats and characterized by low LDMC (10–25%) and high SLA (30–60 mm² mg⁻¹). The second group consists of C species (morpho-physiological model) which were classified as S (StrateFy model) strategy. This group includes mainly tall shrubs, graminoids, and forbs with relatively small leaves (300–2000 mm²). In our opinion, the CSR strategies obtained by the morpho-physiological model showed better agreement with the basic principles underlying Grime''s theory. The use of a limited number of morphological traits (LA, LDMC, SLA) in the StrateFy model does not always allow to determine the life strategy correctly. For example, these traits are insufficient for a clear separation of deeply shaded stress-tolerant species and ruderals. On the other hand, the use of the morpho-physiological model requires a large number of field measurements, which makes it difficult to use this model to allocate CSR strategies for a large number of species.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-00973-9.     

Externally held water – a key factor for hair lichens in boreal forest canopies

Lichens hold water inside (internal pool) and outside their body (external pool). Yet, external pool size is not known in hair lichens dominating boreal forest canopies. Here we quantify morphological traits and internal/external water in two widespread Bryoria species along Picea abies canopy-height gradients: Bryoria fuscescens at 5–20 m and Bryoria capillaris at 15–20 m. Dry mass and specific thallus mass (STM) of intact B. fuscescens increased with height, while STM of individual branches did not. Maximum water holding capacity (mg H₂O cm⁻²) increased with height, but did not differ between the species. Bryoria had much larger external (79–84% of total) than internal water pools, trapping water by dense clusters of thin, overlapping branches. They thus increase water storage in boreal forest canopies and influence hydrology. High external water storage extends hydration periods and improves lichen performance in upper canopies, and thereby contributes to the success of these hair lichens.     

Affinity of human IgG subclasses to mouse Fc gamma receptors

Human IgG is the main antibody class used in antibody therapies because of its efficacy and longer half-life, which are completely or partly due to FcγR-mediated functions of the molecules. Preclinical testing in mouse models are frequently performed using human IgG, but no detailed information on binding of human IgG to mouse FcγRs is available. The orthologous mouse and human FcγRs share roughly 60–70% identity, suggesting some incompatibility. Here, we report binding affinities of all mouse and human IgG subclasses to mouse FcγR. Human IgGs bound to mouse FcγR with remarkably similar binding strengths as we know from binding to human ortholog receptors, with relative affinities IgG3>IgG1>IgG4>IgG2 and FcγRI>>FcγRIV>FcγRIII>FcγRIIb. This suggests human IgG subclasses to have similar relative FcγR-mediated biological activities in mice.     

用甲酰胺提高多聚酶链式反应的特异性、灵敏度和效率的研究

在多聚酶链式反应体系中加入甲酰胺可以有效地抑制非特异性扩增,提高特异性扩增,并使反应的灵敏度提高一个数量级。     

花粉发育的研究进展

近年来,随着现代生物学技术及分子生物学技术在花粉生物学研究领域中广泛的应用,从而使花粉发育过程中一些关键问题及其有关分子机理的研究均获得了重要进展。目前已克隆了许多与花粉发育有关的,并鉴定了一些花粉发育的突变体。本文针对花偻发育过程中的细胞质改组;胼胝质壁、淀粉粒和细胞器的动态变化;绒毡层的发育;花粉发育特异基因;以及不对称分裂和细胞命运等几个生物学问题的研究进展作了简要综述,最后还提出了一些研究展望。