Protective Capacity of the Human Anamnestic Antibody Response during Acute Dengue Virus Infection.

Half of the world's population is exposed to the risk of dengue virus infection. Although a vaccine for dengue virus is now available in a few countries, its reported overall efficacy of about 60% is not ideal. Protective immune correlates following natural dengue virus infection remain undefined, which makes it difficult to predict the efficacy of new vaccines. In this study, we address the protective capacity of dengue virus-specific antibodies that are produced by plasmablasts a few days after natural secondary infection. Among a panel of 18 dengue virus-reactive human monoclonal antibodies, four groups of antibodies were identified based on their binding properties. While antibodies targeting the fusion loop of the glycoprotein of dengue virus dominated the antibody response, two smaller groups of antibodies bound to previously undescribed epitopes in domain II of the E protein. The latter, largely serotype-cross-reactive antibodies, demonstrated increased stability of binding at pH 5. These antibodies possessed weak to moderate neutralization capacity in vitro but were the most efficacious in promoting the survival of infected mice. Our data suggest that the cross-reactive anamnestic antibody response has a protective capacity despite moderate neutralization in vitro and a moderate decrease of viremia in vivo IMPORTANCE: Antibodies can protect from symptomatic dengue virus infection. However, it is not easy to assess which classes of antibodies provide protection because in vitro assays are not always predictive of in vivo protection. During a repeat infection, dengue virus-specific immune memory cells are reactivated and large amounts of antibodies are produced. By studying antibodies cloned from patients with heterologous secondary infection, we tested the protective value of the serotype-cross-reactive "recall" or "anamnestic" response. We found that results from in vitro neutralization assays did not always correlate with the ability of the antibodies to reduce viremia in a mouse model. In addition, a decrease of viremia in mice did not necessarily improve survival. The most protective antibodies were stable at pH 5, suggesting that antibody binding in the endosomes, after the antibody-virus complex is internalized, might be important to block virus spread in the organism.

Plasmablasts generated during repeated dengue infection are virus glycoprotein-specific and bind to multiple virus serotypes.

Dengue virus immune protection is specific to the serotype encountered and is thought to persist throughout one's lifetime. Many serotype cross-reactive memory B cells isolated from humans with previous dengue infection are specific for the nonstructural and the prM structural viral proteins, and they can enhance infection in vitro. However, plasmablasts circulating in enormous numbers during acute secondary infection have not been studied. In this study, we analyzed single plasmablasts from two patients by sorting the cells for Ig sequence analysis and for recombinant expression of Abs. In contrast to memory B cells, most plasmablast-derived Abs bound to the structural E protein of dengue, and protection experiments in mice revealed that virus serotypes encountered during past infections were neutralized more efficiently than were the serotypes of the current infection. Together with genetic analyses, we show evidence that plasmablasts in dengue patients are a polyclonal pool of activated E protein-specific memory B cells and that their specificity is not representative of the serum Abs secreted by long-lived plasma cells in the memory phase. These results contribute to the understanding of the phenomenon of original antigenic sin in dengue.

Two case reports and a systematic review of the literature on adult cerebral cortical encephalitis with anti-myelin oligodendrocyte glycoprotein antibody.

Background and purpose: Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) has gained recognition in recent years as an immune-mediated inflammatory demyelinating disease of the central nervous system. The clinical features and prognosis of MOGAD adult cerebral cortical encephalitis (adult CCE) have not been fully elucidated. This study aims to further characterize the clinical symptoms, magnetic resonance imaging (MRI) findings, and prognosis of CCE with anti-MOG antibody. Methods: We present two adult cases of CCE with anti-MOG antibody and summarize the clinical symptoms, magnetic resonance imaging (MRI) findings, and prognosis of this phenotype as per a completed systematic review of the literature. Results: We found a total of 39 cases of MOGAD adult CCE (36% females; average age of onset of 29 years). Among them, 85% had seizure, 82% had headache, 64% had cortical symptoms, 64% had fever, 54% had changes of consciousness, and 38% had ocular symptoms. All cases demonstrated cerebral cortical T2 fluid-attenuated inversion recovery (FLAIR) lesions on MRI. Of the 25 patients (with seizure or not) who had EEG reports, 76% of patients showed abnormal EEG. Cerebrospinal fluid (CSF) white blood cell count of 90% of patients and CSF total protein of 67% of patients were elevated. In 16 patients with available CSF cytology data, 11 (69%) had abnormal cytology findings with monocytic predominance. In the 15 cases for which MOG antibody IgG was tested in both serum and CSF, 14 (93%) demonstrated a higher positive MOG IgG titer in serum than CSF. The majority of patients were treated with immunosuppressive therapy (97% corticosteroids, 15% mycophenolate mofetil, 13% IVIg, 5% azathioprine, and 5% other). The majority of patients had a favorable prognosis after treatment, as exemplified by improved clinical symptoms and imaging. Two patients relapsed. Conclusions: The clinical presentation and prognosis of adult CCE remain less understood in comparison to more common MOGAD phenotypes. It is important to consider MOGAD as an underlying etiology for adult CCE, as early detection and immunotherapy may improve outcomes.

Association of egg consumption with colorectal polyp prevalence: findings from the Lanxi Pre-Colorectal Cancer Cohort (LP3C) in China.

Eggs contain high-quality protein, lavish vitamins and other bioactive nutrients but are rich in cholesterol. Our study is designed to assess the association of egg intake with polyp prevalence. A total of 7068 participants at a high risk of CRC from the Lanxi Pre-Colorectal Cancer Cohort Study (LP3C) were recruited. A food frequency questionnaire (FFQ) was utilized to obtain dietary data through a face-to-face interview. Cases of colorectal polyps were identified by electronic colonoscopy. The logistic regression model was exploited to achieve odds ratios (ORs) and 95% confidence intervals (CIs). Overall 2064 cases of colorectal polyps were identified in the 2018-2019 survey of LP3C. A positive association of egg consumption with colorectal polyp prevalence was found after the multivariable adjustment [ORQ4 vs. Q1 (95% CI): 1.23 (1.05-1.44); Ptrend = 0.01]. However, a positive relationship disappeared after further adjustment for dietary cholesterol (Ptrend = 0.37), which explained that the harmful role of eggs could be ascribed to the high content of dietary cholesterol. Besides, a positive trend was found between dietary cholesterol and polyp prevalence [OR (95% CI): 1.21 (0.99-1.47); Ptrend = 0.04]. Furthermore, replacing 1 egg (50 g d-1) with an equal amount of total dairy products was related to 11% lower colorectal polyp prevalence [OR (95% CI): 0.89 (0.80-0.99); P = 0.03]. In summary, higher egg consumption was correlated with a higher polyp prevalence among the Chinese population at a high risk of CRC, which was ascribed to the high content of dietary cholesterol in eggs. Besides, individuals with the highest dietary cholesterol tended to have a higher polyp prevalence. Reducing the consumption of eggs and replacing eggs with total dairy products as alternative protein sources may prevent the occurrence of polyps in China.

Targeted metabolomics analysis of nucleosides and the identification of biomarkers for colorectal adenomas and colorectal cancer.

The morbidity and mortality of colorectal cancer (CRC) have been increasing in recent years, and early detection of CRC can improve the survival rate of patients. RNA methylation plays crucial roles in many biological processes and has been implicated in the initiation of various diseases, including cancer. Serum contains a variety of biomolecules and is an important clinical sample for biomarker discovery. In this study, we developed a targeted metabolomics method for the quantitative analysis of nucleosides in human serum samples by using liquid chromatography with tandem mass spectrometry (LC-MS/MS). We successfully quantified the concentrations of nucleosides in serum samples from 51 healthy controls, 37 patients with colorectal adenomas, and 55 patients with CRC. The results showed that the concentrations of N 6-methyladenosine (m6A), N 1-methyladenosine (m1A), and 3-methyluridine (m3U) were increased in patients with CRC, whereas the concentrations of N 2-methylguanosine (m2G), 2'-O-methyluridine (Um), and 2'-O-methylguanosine (Gm) were decreased in patients with CRC, compared with the healthy controls and patients with colorectal adenomas. Moreover, the levels of 2'-O-methyluridine and 2'-O-methylguanosine were lower in patients with colorectal adenomas than those in healthy controls. Interestingly, the levels of Um and Gm gradually decreased in the following order: healthy controls to colorectal adenoma patients to CRC patients. These results revealed that the aberrations of these nucleosides were tightly correlated to colorectal adenomas and CRC. In addition, the present work will stimulate future investigations about the regulatory roles of these nucleosides in the initiation and development of CRC.

Matching is the Key Factor to Improve the Production of Patchoulol in the Plant Chassis of Marchantia paleacea.

The valuable terpenoids, such as artemisinin acid, have achieved bioproduction in the chassis of microbes recently. In this study, Marchantia paleacea L, a promising plant synthetic biology chassis, was used to explore the possibility of patchoulol production by constructing a synthetic biology pathway composed of FPS and PTS. The experiment results show that the maximum yields based on the cytoplasm and plastid pathway were 621.56 and 1006.45 µg/g, respectively. However, there is no statistically significant difference in the yield of patchoulol between transformant plants with different subcellular compartment-targeting pathways. However, it was found that the highest yield of patchoulol was achieved in transformant plants with similar transcription levels of FPS and PTS. Also, the optimized transcription ratio between PTS and FPS is determined at 1.12 based on statistical analysis and model simulation. Therefore, two kinds of new optimized pathway vectors were constructed. One is based on the fusion protein method, and the other is based on protein expression individually, in which the same promoter and terminator were used to derive the expression of both FPS and PTS. The effect of pathway optimization was tested by transient and stable transformation. The production of patchoulol in transient transformation was the same for the two abovementioned kinds of matching pathway and higher than that for the original pathway. Also, in stable transformation, the yield of patchoulol reached up to 3250.30 µg/g, being three times the maximum content before optimization. It is suggested that M. paleacea is a powerful plant chassis for terpenoid synthetic biology and the matching between enzymes may be the key factor in determining the metabolic flux of the pathway in the study of synthetic biology.

A Human Antibody Neutralizes Different Flaviviruses by Using Different Mechanisms.

Human antibody SIgN-3C neutralizes dengue virus (DENV) and Zika virus (ZIKV) differently. DENV:SIgN-3C Fab and ZIKV:SIgN-3C Fab cryoelectron microscopy (cryo-EM) complex structures show Fabs crosslink E protein dimers at extracellular pH 8.0 condition and also when further incubated at acidic endosomal conditions (pH 8.0-6.5). We observe Fab binding to DENV (pH 8.0-5.0) prevents virus fusion, and the number of bound Fabs increase (from 120 to 180). For ZIKV, although there are already 180 copies of Fab at pH 8.0, virus structural changes at pH 5.0 are not inhibited. The immunoglobulin G (IgG):DENV structure at pH 8.0 shows both Fab arms bind to epitopes around the 2-fold vertex. On ZIKV, an additional Fab around the 5-fold vertex at pH 8.0 suggests one IgG arm would engage with an epitope, although the other may bind to other viruses, causing aggregation. For DENV2 at pH 5.0, a similar scenario would occur, suggesting DENV2:IgG complex would aggregate in the endosome. Hence, a single antibody employs different neutralization mechanisms against different flaviviruses.

Erratum: Publisher Correction: A potent neutralizing antibody with therapeutic potential against all four serotypes of dengue virus.

[This corrects the article DOI: 10.1038/s41541-016-0003-3.].

A potent neutralizing antibody with therapeutic potential against all four serotypes of dengue virus.

A therapy for dengue is still elusive. We describe the neutralizing and protective capacity of a dengue serotype-cross-reactive antibody isolated from the plasmablasts of a patient. Antibody SIgN-3C neutralized all four dengue virus serotypes at nano to picomolar concentrations and significantly decreased viremia of all serotypes in adult mice when given 2 days after infection. Moreover, mice were protected from pathology and death from a lethal dengue virus-2 infection. To avoid potential Fc-mediated uptake of immune complexes and ensuing enhanced infection, we introduced a LALA mutation in the Fc part. SIgN-3C-LALA was as efficient as the non-modified antibody in neutralizing dengue virus and in protecting mice while antibody-dependent enhancement was completely abrogated. The epitope of the antibody includes conserved amino acids in all three domains of the glycoprotein, which can explain its cross-reactivity. SIgN-3C-LALA neutralizes dengue virus both pre and post-attachment to host cells. These attributes likely contribute to the remarkable protective capacity of SIgN-3C.

Cross-reactive dengue human monoclonal antibody prevents severe pathologies and death from Zika virus infections.

Zika virus (ZIKV) infections have been linked with neurological complications and congenital Zika syndrome. Given the high level of homology between ZIKV and the related flavivirus dengue virus (DENV), we investigated the level of cross-reactivity with ZIKV using a panel of DENV human mAbs. A majority of the mAbs showed binding to ZIKV virions, with several exhibiting neutralizing capacities against ZIKV in vitro. Three of the best ZIKV-neutralizing mAbs were found to recognize diverse epitopes on the envelope (E) glycoprotein: the highly conserved fusion-loop peptide, a conformation-specific epitope on the E monomer, and a quaternary epitope on the virion surface. The most potent ZIKV-neutralizing mAb (SIgN-3C) was assessed in 2 type I interferon receptor-deficient (IFNAR-/-) mouse models of ZIKV infection. Treatment of adult nonpregnant mice with SIgN-3C rescued mice from virus-induced weight loss and mortality. The SIgN-3C variant with Leu-to-Ala mutations in the Fc region (SIgN-3C-LALA) did not induce antibody-dependent enhancement (ADE) in vitro but provided similar levels of protection in vivo. In pregnant ZIKV-infected IFNAR-/- mice, treatment with SIgN-3C or SIgN-3C-LALA significantly reduced viral load in the fetal organs and placenta and abrogated virus-induced fetal growth retardation. Therefore, SIgN-3C-LALA holds promise as a ZIKV prophylactic and therapeutic agent.