MICROBIOME: Targeting Microbiota to Treat Lethal, Inflammatory Cardiomyopathy
Inflammatory cardiomyopathy is a disease arising from targeting of autoreactive T-cells to a patient’s cardiac muscle. Specifically autoreactive T-cells are generated against Myosin Heavy Chain 6 (MYH6), a crucial component of cardiac muscle. Treatments for this condition remain elusive, as the underlying mechanism of autoreactive T-cell generation has not been well understood. Using a mouse model of progressive inflammatory cardiomyopathy, the authors of this paper were able to show that MYH6-like protein epitopes, generated by bacteria of the gut could lead to generation of autoreactive T-cells and increased mortality. Using in silico modeling, the authors were also able to identify a species specific β-galactosidase gene from the bacterium Bacteroides thetaiotaomicron (B. theta), that was predicted to condition autoreactive T-cells against MYH6. Using germ-free mice inoculated with B. thetalacking this gene, the authors were able to confirm that B. thetaexpressing β-galactosidase contributes to the progression of inflammatory cardiomyopathy. The results of these findings in mice were recapitulated in serum samples of human patients with inflammatory cardiomyopathy, which revealed elevated levels of antibodies targeting B. thetaβ-galactosidase. Finally the authors showed significant improvements in mouse survival rates when antibiotics were administered to reduce the level of gut bacteria and prevent generation of autoreactive T-cells. This work demonstrates a clearer mechanism of the development of inflammatory cardiomyopathy as well as demonstrating possible treatments to reduce the progression of the disease.
By: Nate Dempsey
DOI: 10.1126/science.aav3487
AWARENESS: What is Antibiotic Resistance?
Antibiotic resistance is an emerging threat to human health—it renders therapeutics against pathogenic bacteria completely ineffective. Resistance emerges as an adaptive strategy for bacteria to survive in the presence of an antibiotic threat. Resistance often arises from the accumulation of random mutations that allow the microbe to survive in the presence of antibiotics. There are several mechanisms of action of mutations that cause resistance. For instance, mutations can modify the antibiotic target, modify the antibiotic itself, decrease the drug uptake by bacteria, or activate efflux mechanisms to expel the antibiotic (Munita & Arias 2016).
One of the most common mechanisms of resistance is the alteration of the drug binding site of antibiotics. Researchers have discovered that various bacteria causing urinary tract and respiratory infections, suchasEscherichia coliandStreptococcus pneumoniae, havebecome resistant to fluoroquinolone (FQ) by acquiring mutations in genes that encode the target site of FQs(LaPlante et al. 2007), which are DNA gyrase and topoisomerase IV enzymes (which are essential is bacterial DNA replication). Therefore, this resistance can be combatted by developing new antibiotics that either bind to the mutated DNA gyrase and topoisomerase IV enzymes, or that have a different lethal target.
By: Lourdes Kaufman
Munita, Jose M., and Arias, Cesar A. “Mechanisms of Antibiotic Resistance.” Microbiology Spectrum, vol. 4, no. 2, 2016, pp. Microbiology spectrum, April 2016, Vol.4(2).
AWARENESS: How Does the Microbiome Affect HIV Acquisition?
Research has shown that certain distinct microbial profiles of the female reproductive tract, referred to as “cervicotypes,” (CT) are associated with an elevated risk of HIV acquisition. Data was taken from the FRESH cohort, which is a group of women in the Umlazi Township near the city of Durban, South Africa. This cohort is at an extremely elevated risk of acquiring HIV; 66% of females acquire HIV by the age of 23. Women in this cohort with CT4, defined as a high-diversity, low Lactobacillus community, acquired HIV four times as often as those with CT1, defined as a Lactobacillus crispatus dominant community (Gosmann et. al 2017). Gosmann et. al (2017) hypothesize that this four-fold increase in HIV acquisition in women with CT4 has to do with elevated numbers of activated genital CD4+ T cells (HIV-target cells). This makes sense, since a greater number of HIV-target cells at the site of infection in women would mean that the HIV virus is more likely to “find” a host cell to infect. Therefore, future HIV prevention techniques in women can target the vaginal microbiome—shifting CT4 communities to CT1 communities could perhaps lower a woman’s’ likelihood of acquiring HIV upon exposure.
By: Lourdes Kaufman
Gosmann, Christina, et al. “Lactobacillus-Deficient Cervicovaginal Bacterial Communities Are Associated with Increased HIV Acquisition in Young South African Women.” Immunity, vol. 46, no. 1, 2017, pp. 29–37.
PLAGUE THEME: Monoclonal Antibody prevents against Plague bacteria
Despite causing many of the most devastating epidemics in history, Yersinia pestishas never been eradicated. This gives Y. pestisdangerous potential as a biological weapon, necessitating research into effective treatments and vaccines. Monoclonal antibodies (mAbs) have been proposed as effective protective agents against the plague, but before this 2017 paper by Liu et al. only one mAb had been confirmed to prevent spread of Y. pestis.
In this paper, the authors present F2H5, a mAb that protects against Y. pestisinfection in a mouse model. Previous studies of mAbs in Y. Pestis prevention focused on antibodies that bind to the bacterial F1 protein, so the authors immunized mice with recombinant F1 (rF1) and used ELISA to obtain three monoclonal antibody lines with therapeutic potential. They then tested the effectiveness of each mAb by first pre-treating mice with an antibody, and subsequently infecting them with Y. pestis; they found that F2H5 provided complete protection against Y. pestisinfection. Once they observed the antibacterial effects of F2H5, they used ELISA and Western Blot to confirm that the mAb bound selectively to rF1.
Once they had identified and verified F2H5, the authors used computational methods to investigate the epitope to which the mAb binds. Using a novel method called Residue Contact Frequency (RCF), the researchers were able to predict the F1 epitopes most likely to be recognized by F2H5. They then verified the top RCF result using Western Blot, mutating amino acids in the region until they identified a three-residue sequence essential for F2H5 to bind to F1. They then used computational technology to characterize the F1/F2H5 complex and the effect of F1 mutations on its structure.
This paper provides a novel antibody which could be used to protect against a dangerous bioweapon. The authors were able to confirm its efficacy in a mouse model and humanize it for future therapeutic use. In addition, by identifying the epitope and predicting the dynamics of the antibody-antigen complex, the authors verified their assessment of therapeutic potential.
By: Zach Altshuler
Liu, W. et al.Identification and characterization of a neutralizing monoclonal antibody that provides complete protection against Yersinia pestis. PLOS ONE, e0177012 (2017).
PLAGUE THEME: Infection promoted when Yersinia pestis Interacts With SIGNR1
The bacterium Yersinia pestis is the pathogen responsible for the historical plagues that affected much of central and western Europe in the 1400s and was responsible for approximately 75-200 million deaths. In modern times outbreaks of Y. pestis are rare and often easily treatable with antibiotics. Progression of Y. pestis infections is brought on by dissemination of an acute infection to disparate areas of the body through hijacking host macrophages to traffic Y. pestis to the lymph nodes and next to the body at large. Interaction between bacteria and macrophages is mediated by cell surface receptors and glycans, in Y. pestis and related pathogenic gram-negative bacteria Lipopolysaccharide (LPS) is the primary epitope recognized by the innate immune system. Sequencing of various Y. pestis strains revealed a lack of gene synthesizing the terminal O-antigen region of LPS. Lack of O-Antigen exposes the LPS core region and the authors hypothesized that this structural change may explain some of the increased efficacy of Y. pestis macrophage-mediated invasion. This hypothesis was confirmed by showing that a knockout of LPS core interacting protein Signr1 (CD209b) in mouse macrophages reduced Y. pestis invasion. This finding was also supported by showing that expression of O-antigen in Y. pestis reduced binding to Signr1 and virulence in mice. While Y. pestis infections are far less common and deadly today that several hundred years ago, understanding how this dangerous pathogen spread will help the response to possible outbreaks in the future.
By: Nate Dempsey
Yang, Kun, He, Yingxia, Park, Chae Gyu, Kang, Young Sun, Zhang, Pei, Han, Yanping, . . . Chen, Tie. (2019). Interacts With SIGNR1 (CD209b) for Promoting Host Dissemination and Infection. Frontiers in Immunology,10, 96.
AWARENESS: What is Alzheimer's Disease?
Alzherimer’s disease (AD) is an irreversible neurodegenerative disorder that interferes with memory and cognition. AD is thought to be caused by the build-up of amyloid plaques and tau protein tangles in the brain that cause neurons to die. How does AD relate to immunology? The brain’s immune system is thought to be a key factor in the development of AD; specifically, the microglia are involved in AD. Microglia are immune cells in the brain that normally clear toxins and debris. In AD patients, microglia appear to not perform their function well or even contribute to the development of the disease. Some scientists hypothesize that amyloid proteins, the proteins that form plaque in the brain in AD patients, activate microglia, which perform properly at first. As more amyloid is produced, the system becomes unregulated. Understanding the microglia activation system is essential in understanding AD and developing treatments.
By: Lourdes Kaufman
“Understanding How the Immune System Contributes to Alzheimer's Disease Development.” Alzheimer's Society, www.alzheimers.org.uk/research/our-research/research-projects/understanding-how-immune-system-contributes-alzheimers-disease-development.
AWARENESS: What is Multiple Sclerosis?
Multiple sclerosis (MS) is a disease of the central nervous system, in which the immune system attacks the myelin sheath nerve covering. The myelin sheath covering protects and insulates neurons, allowing an electrical signal to efficiently propagate down the axon and signal to the next neuron. In MS, the degraded myelin causes communication problems between the brain and the body, as signals can no longer be effectively sent, since electrical signals in neurons are able to dissipate. The disease can cause permanent damage to nerves in the body. The symptoms vary, and depend on the amount of damage to the nerves. Some MS patients cannot walk, while others may have remission periods without new symptoms at all. How does MS relate to immunology? MS is relevant to immunology because it is caused by a maladaptive immune response in the central nervous system. By understanding the immunology behind this disorder, effective treatments can be developed.
By: Lourdes Kaufman
“Multiple Sclerosis.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 19 Apr. 2019, www.mayoclinic.org/diseases-conditions/multiple-sclerosis/symptoms-causes/syc-20350269.
THE BLACK PLAGUE: Next Generation Vaccines
The plague, is one of the most notorious infectious diseases of all time, having a history or decimating populations with a 100% mortality rate. It is now understood that the plague is caused by Yersinia pestis, a Gram-negative bacterium, which is often transmitted through fleas to rodents and then to humans. The originally contracted bubonic plague could then develop into either septicemic plague or a pneumonic plague. There are currently no FDA approved vaccines against plague, and thus this paper, focuses on a novel approach, using a mutated bacteriophage T4 nanoparticle as a possible carrier of a vaccine, specifically targeting pneumonic plague.
This strategy utilizes two antigens, the F1 and V antigen, both of which assist in the immunosuppressive capabilities of the plague by helping Y.pestis to escape phagocytosis. Hence, by introducing these antigens through a vaccine, the immune system could ideally develop targeted antibodies which could fight off the bacteria in the future. The main problems with current F1 vaccine attempts are the effectiveness of cell-mediated immune responses and the fact that F1 naturally polymerizes into aggregates, which become unrecognizable from the normal form. The researchers of this paper attempted to solve these problems through their development of a novel delivery system, using the bacteriophage T4 nanoparticle. In order to form this nanoparticle, first the F1 antigen was mutated so that it no longer polymerized, and it was then fused to the V antigen, creating a F1mut-V immunogen which was further fused to the Soc protein on the phage T4 nanoparticle capsid. The infused T4 nanoparticle was then tested against isolated V, the F1mut-V, and then a control group in mouse studies with 12 mice per group. There were also other antigens tested, such as YscF and F1mut-V10, however these results were not as significant compared to the previously noted antigens.
Overall, the data showed that the utilization of the T4 nanoparticle caused the production of similar amounts of IgG1 antibodies, a part of the humoral response, than the soluble V and F1-V. However, the T4 mice were found to have higher levels of IgG2a, which is a part of the cellular response. This could be seen in the results as where as there were two deaths in both the V and F1-V groups, there was 100% protection with no deaths in the T4 group, which suggests that even though the antibody levels were similar, the antibodies in the T4 group seem to be more effective, meaning that the T4 antigens were more potent. All 12 mice in the control group died by day 4.
Overall the advantages of the T4 vaccine could be summarized as it enhances vaccine potency compared to the introduction of both isolated and combined antigens, as shown by the increased protection in the study results. Additionally, it the T4 vaccine would not require an additional adjuvant, and it could be easily be modified to include additional antigens as well. These findings are essential for the world because of the capability of aerosolized Yersinia pestis to be used as a bioterror agent. Y.pestis is both easily manufactured and aerosolized, and as a result of its 100% mortality rate within 3-6 days, it has the potential to be used as a lethal biological weapon. Thus, although relatively low amount of people die from the plague worldwide, this vaccine has the potential to eliminate the potential global threat.
By: Harris Allen
Tao, P., Mahalingam, M., Kirtley, M., Van Lier, C., Sha, J., Yeager, L., . . . Kubori, T. (2013). Mutated and Bacteriophage T4 Nanoparticle Arrayed F1-V Immunogens from Yersinia pestis as Next Generation Plague Vaccines (Next Generation Plague Vaccines). 9(7), E1003495.
https://doi.org/10.1371/journal.ppat.1003495
ALZHEIMERS DISEASE: CD33 - TREM2 Interaction may have Immune signaling implications
In CD33 modulates TREM2: convergence of Alzheimer loci, Chan et al. investigated the connections between various genetic variants associated with risk of late-onset Alzheimer’s Disease (AD). They worked in monocytes, a type of white blood cell that can differentiate further into more targeted immune cells, and based their investigation on large-scale studies associating genetic mutations with disease susceptibility. They started by validating their model system: they confirmed that the genes they focused on were predominantly expressed in monocytes and that AD-associated alleles were correlated with the expected protein-level changes. In the TREM1/2 receptor locus, in which the former is pro-inflammatory and the latter anti-inflammatory, they found that the association of TREM1 mutations with AD results from changes in signaling balance rather than a simple reduction of TREM1, suggesting a potential effect of TREM2. In the CD33 locus, they found that two mutations that increase expression have opposite effects on AD susceptibility, leaving the connection between CD33 expression and AD murky. Interestingly, they found an effect of CD33 on TREM2 expression, suggesting a potential connection between their associations with AD; their model suggested a link between CD33 suppression and decreased expression of TREM2. They hypothesized that the association between TREM2 and AD may have to do with accumulated amyloid damage over time. They concluded that the signaling connection between CD33 and TREM2 (and the similar connection between NME8 and PTK2B) could prove important for future studies improving understanding of the genetic and immune basis of AD.
By: Zach Altshuler