Cytidine deamination-induced perpetual immunity to SAR-CoV-2 infection is a potential new therapeutic target.

As the world is racing to develop perpetual immunity to the SARS-CoV-2 virus. The emergence of new viral strains, together with vaccination and reinfections, are all contributing to a long-term immunity against the deadly virus that has taken over the world since its introduction to humans in late December 2019. The discovery that more than 95 percent of people who recovered from COVID-19 had long-lasting immunity and that asymptomatic people have a different immune response to SARS-CoV-2 than symptomatic people has shifted attention to how our immune system initiates such diverse responses. These findings have provided reason to believe that SARS-CoV-2 days are numbered. Hundreds of research papers have been published on the causes of long-lasting immune responses and variations in the numbers of different immune cell types in COVID 19 survivors, but the main reason of these differences has still not been adequately identified. In this article, we focus on the activation-induced cytidine deaminase (AID), which initiates molecular processes that allow our immune system to generate antibodies against SARS-CoV-2. To establish lasting immunity to SARS-CoV-2, we suggest that AID could be the key to unlocking it.

Immunoglobulin Class Switch Recombination Is Initiated by Rare Cytosine Deamination Events at Switch Regions.

Activation-induced cytidine deaminase (AID) initiates immunoglobulin (Ig) class switch recombination (CSR), somatic hypermutation (SHM), and gene conversion by converting DNA cytosines to uracils at specific genomic regions. In this study, we examined AID footprints across the entire length of an engineered switch region in cells ablated for uracil repair. We found that AID deamination occurs predominantly at WRC hot spots (where W is A or T and R is A or G) and that the deamination frequency remains constant across the entire switch region. Importantly, we analyzed monoallelic AID deamination footprints on both DNA strands occurring within a single cell cycle. We found that AID generates few and mostly isolated uracils in the switch region, although processive AID deaminations are evident in some molecules. The frequency of molecules containing deamination on both DNA strands at the acceptor switch region correlates with the class switch efficiency, raising the possibility that the minimal requirement for DNA double-strand break (DSB) formation is as low as even one AID deamination event on both DNA strands.

Rheumatoid Arthritis and Periodontal Disease. An Update.

A review of the epidemiological, pathological and immunological relationships between two chronic inflammatory diseases: rheumatoid arthritis (RA) and periodontal disease (PD). RA is a chronic inflammatory disease of the joints, characterized by loss of connective tissue and mineralized structures, the so-called "synovial membrane." Periodontitis is the inflammatory destruction of the periodontal attachment and alveolar bone. While the etiology of these two diseases may differ, the underlying pathogenic mechanisms are similar. And it is possible that individuals manifesting both PD and RA may suffer from a unifying underlying systemic deregulation of the inflammatory response. There is an overproduction of a variety of cytokines and MMPs that appears to be common in both diseases. Oral health parameters should be more closely monitored in patients with RA, an autoimmune disease. Data suggest that periodontal therapies combined with routine RA treatments further improve RA status. Interventions to prevent, minimize or treat periodontitis in arthritis patients will definitely promise a better quality of life for these patients.

A monoamine oxidase from scallop Chlamys farreri serving as an immunomodulator in response against bacterial challenge.

Monoamine oxidase (MAO) is an essential enzyme in the catabolism of monoamines, and implicated in the immune response of vertebrates. In the present study, the full-length cDNA encoding monoamine oxidase (designated CfMAO) was cloned from Chlamys farreri by using rapid amplification of cDNA ends (RACE) approaches and expression sequence tag (EST) analysis. The open reading frame of CfMAO cDNA encoded 519 amino acids, which shared 73.9% similarity with that from oyster Crassostrea gigas, and 64.5-66.3% similarity with those from vertebrates. A conserved Amino_oxidase domain and a transmembrane domain were identified in the deduced CfMAO protein. The mRNA transcripts of CfMAO could be detected in all the tested tissues, including haemocytes, hepatopancreas, kidney, adductor muscle, mantle, gill and gonad. The mRNA expression of CfMAO was up-regulated significantly in haemocytes of scallops during 6-48 h after bacteria Vibrio anguillarum challenge, and it reached the peak (25.9-fold, P < 0.05) at 12h. The cDNA fragment encoding the mature peptide of CfMAO was expressed in the prokaryotic expression system, and 1mg of the recombinant protein (rCfMAO) could catalyze the deamination of 3665.59 nmol serotonin, 2061.89 nmol norepinephrine, 2104.85 nmol epinephrine or 3040.34 nmol dopamine within 1 min (nmol min⁻¹ mg⁻¹) in vitro. When the reaction mixture was coincubated with 0.1 mmol L⁻¹ MAO inhibitor clorgyline, its catalyzing activity to deaminize serotonin and dopamine was decreased significantly to 1603.69 and 955.39 nmol min⁻¹ mg⁻¹ (P < 0.05) respectively. These results indicated that CfMAO, as the homologue of monoamine oxidase in scallop C. farreri, could modulate the immune response of scallops through the deamination of monoamines.

Childhood coeliac disease: towards an improved serological mass screening strategy.

BACKGROUND: In 1997-1998, 6127 asymptomatic children aged 2-4 years were screened for coeliac disease (CD) by anti-endomysium (EmA) testing in the Netherlands. After 6 (+/-2) months, biopsies were performed in 57 seropositive children; 31(54%) had villous atrophy, but 26 (46%), all HLA-DQ2/DQ8 positive, had normal histology. AIMS: To reduce the number of unnecessary biopsies after serological mass screening for CD in asymptomatic young children by optimizing screening procedures. METHODS: Comparing different tests and optimizing their cut-off point: screening samples were tested for EmA, tissue-transglutaminase (tTGA), antigliadin and deamidated-gliadin-peptides (anti-DGP) antibodies. Determining serological persistence over time: persistence of EmA and tTGA was determined by testing serological samples obtained at biopsy. RESULTS: Tissue-transglutaminase and anti-DGP correlated with EmA. Optimization of standard cut-off points not only reduced unnecessary biopsies by 50-96% but also reduced sensitivity. EmA persisted in all CD children, but in only 50% of the non-CD children. tTGA persisted in 83% of CD, but in only 15% of non-CD children. CONCLUSIONS: Coeliac disease antibodies may be present transiently in genetically predisposed children. To avoid unnecessary biopsies, serological mass screening procedures may be improved by repeating EmA and/or tTGA in initially seropositive young children after 6 months, before proceeding to biopsy. This may reduce the number of unnecessary biopsies that are performed.