Inactivation of SAM-methyltransferase is the mechanism of attenuation of a historic louse borne typhus vaccine strain

Louse borne typhus (also called epidemic typhus) was one of man's major scourges, and epidemics of the disease can be reignited when social, economic, or political systems are disrupted. The fear of a bioterrorist attack using the etiologic agent of typhus, Rickettsia prowazekii, was a reality. An attenuated typhus vaccine, R. prowazekii Madrid E strain, was observed to revert to virulence as demonstrated by isolation of the virulent revertant Evir strain from animals which were inoculated with Madrid E strain. The mechanism of the mutation in R. prowazekii that affects the virulence of the vaccine was not known. We sequenced the genome of the virulent revertant Evir strain and compared its genome sequence with the genome sequences of its parental strain, Madrid E. We found that only a single nucleotide in the entire genome was different between the vaccine strain Madrid E and its virulent revertant strain Evir. The mutation is a single nucleotide insertion in the methyltransferase gene (also known as PR028) in the vaccine strain that inactivated the gene. We also confirmed that the vaccine strain E did not cause fever in guinea pigs and the virulent revertant strain Evir caused fever in guinea pigs. We concluded that a single nucleotide insertion in the methyltransferase gene of R. prowazekii attenuated the R. prowazekii vaccine strain E. This suggested that an irreversible insertion or deletion mutation in the methyl transferase gene of R. prowazekii is required for Madrid E to be considered a safe vaccine

The Weil-Felix test for the rickettsioses

The so-called Weil-Felix reaction as a method of diagnosis in typhus fever has been widely accepted by German workers, especially on the Eastern fronts, where in the Balkans especially, cases of typhus fever have been numerous. World War I was responsible for some of the worst epidemics of typhus that the world has known. In this day and age everyone accepts unquestioningly the fact that the causative agent of epidemic typhus is Rickettsia prowazeki but in those days the candidate etiological agents were as numerous as candidate viruses have been in our days for the virus of infective hepatitis. When the Great War of 1914-1919 was over Weil devoted himself whole-heartedly to all aspects of typhus research; etiology, diagnosis and prophylaxis, whereas after World War II, Felix stressed the necessity of standardising the W-F test and his recommendations were published in the Bulletin of the World Health Organisation (1950).peer-reviewe

Wholly Rickettsia! Reconstructed Metabolic Profile of the Quintessential Bacterial Parasite of Eukaryotic Cells

Reductive genome evolution has purged many metabolic pathways from obligate intracellular Rickettsia (Alphaproteobacteria; Rickettsiaceae). While some aspects of host-dependent rickettsial metabolism have been characterized, the array of host-acquired metabolites and their cognate transporters remains unknown. This dearth of information has thwarted efforts to obtain an axenic Rickettsia culture, a major impediment to conventional genetic approaches. Using phylogenomics and computational pathway analysis, we reconstructed the Rickettsia metabolic and transport network, identifying 51 host-acquired metabolites (only 21 previously characterized) needed to compensate for degraded biosynthesis pathways. In the absence of glycolysis and the pentose phosphate pathway, cell envelope glycocon- jugates are synthesized from three imported host sugars, with a range of additional host-acquired metabolites fueling the tricarboxylic acid cycle. Fatty acid and glycero- phospholipid pathways also initiate from host precursors, and import of both iso- prenes and terpenoids is required for the synthesis of ubiquinone and the lipid car- rier of lipid I and O-antigen. Unlike metabolite-provisioning bacterial symbionts of arthropods, rickettsiae cannot synthesize B vitamins or most other cofactors, accen- tuating their parasitic nature. Six biosynthesis pathways contain holes (missing en- zymes); similar patterns in taxonomically diverse bacteria suggest alternative en- zymes that await discovery. A paucity of characterized and predicted transporters emphasizes the knowledge gap concerning how rickettsiae import host metabolites, some of which are large and not known to be transported by bacteria. Collectively, our reconstructed metabolic network offers clues to how rickettsiae hijack host met- abolic pathways. This blueprint for growth determinants is an important step toward the design of axenic media to rescue rickettsiae from the eukaryotic cell

Compelled to Volunteer: American Conscientious Objectors to World War II as Subjects of Medical Research

This dissertation is a history of the use of World War II-era American conscientious objectors as the subjects of medical research. Under the Selective Training and Service Act of 1940, conscientious objectors had two choices: provide noncombatant service within the military or provide work of national importance under civilian direction under the auspices of a program called Civilian Public Service (CPS). Conscientious objectors who chose assignment to CPS were placed in camps in which the men labored on a work project authorized by the U.S. Selective Service System, the government entity that administered the draft. At the outset of the CPS program, the camps were modeled after the work camps of the Civilian Conservation Corps, a New Deal jobs program. Over time, and largely due to protests that such Civilian Conservation Corps-type forestry and soil conservation work assignments were not the promised work of national importance, other types of CPS camps were developed, with work projects dealing with public health, custodial care for the mentally disabled, or scientific research. In the later, which became commonly known as the guinea pig units, over five hundred conscientious objectors voluntarily participated as research subjects for a diverse assortment of scientific studies, including projects that dealt with infectious diseases, diet, frostbite, psycho-acoustics, and the impacts of temperature extremes and of altitude. In addition to describing the creation and operation of the guinea pig units, this dissertation examines the use of American World War II conscientious objectors as research subjects in light of two specific questions: first, why did these men volunteer to be guinea pigs? And second, was the use of World War II-era conscientious objectors as research subjects in keeping with the ethical standards of the time? This dissertation draws upon a diverse array of sources to answer the question of motivation from the volunteers' perspectives. Likewise, this dissertation relies upon a wide array of sources to piece together what researchers of the day, both military and civilian, would have considered acceptable and unacceptable uses of people in the name of research

Microorganisms as Shapers of Human Civilization, from Pandemics to Even Our Genomes: Villains or Friends? A Historical Approach

SARS-CoV-2; Influenza; MicrobiotaSARS-CoV-2; Influenza; MicrobiotaSARS-CoV-2; Influenza; MicrobiotaUniversal history is characterized by continuous evolution, in which civilizations are born and die. This evolution is associated with multiple factors, among which the role of microorganisms is often overlooked. Viruses and bacteria have written or decisively contributed to terrible episodes of history, such as the Black Death in 14th century Europe, the annihilation of pre-Columbian American civilizations, and pandemics such as the 1918 Spanish flu or the current COVID-19 pandemic caused by the coronavirus SARS-CoV-2. Nevertheless, it is clear that we could not live in a world without these tiny beings. Endogenous retroviruses have been key to our evolution and for the regulation of gene expression, and the gut microbiota helps us digest compounds that we could not otherwise process. In addition, we have used microorganisms to preserve or prepare food for millennia and more recently to obtain drugs such as antibiotics or to develop recombinant DNA technologies. Due to the enormous importance of microorganisms for our survival, they have significantly influenced the population genetics of different human groups. This paper will review the role of microorganisms as “villains” who have been responsible for tremendous mortality throughout history but also as “friends” who help us survive and evolve