Up close and 3-dimensional: HIV caught in the act inside the gut

HIV infection has many unhealthy consequences on the body, but in particular it messes up the gut. The human intestine has the highest concentration of HIV target cells, the majority of which are destroyed within days of infection, and before CD4 T cell counts drop measurably in the blood. A study published on January 30th in PLOS Pathogens reports the first three-dimensional ultra-structural study of HIV infection in vivo. Not only does it reveal details on how the virus quickly infects immune cells in the gut, using them as virus-producing factories, but it also highlights where the virus “hides out” deep within the intestinal tissue.Pamela Bjorkman, from the Howard Hughes Medical Institute and the California Institute of Technology, USA, and colleagues used electron tomography for a high-resolution study of HIV virus in the guts of “humanized” mice, whose immune system is made up to a large degree of human cells. They infected these “BLT mice” (so-called because they have human bone marrow, thymus, and liver cells) with HIV virus and developed methods that allowed them to safely examine and visualize the three-dimensional architecture of infected parts of the gut.They saw HIV-infected human immune cells, caught virus particles in the act of budding from such cells, and also found groups of free immature and mature viruses. For one infected host cell (turned HIV factory) the researchers counted 63 virus particles it had likely released. The actual number is almost certainly much higher, because the method can only visualize virus particles surrounding the host cell within a relatively small part of the tissue. Nevertheless, they discovered that groups of viruses that were farther from the host cell were more mature than those closer to it, which suggested that the host cell releases new virus in a series of “semi-synchronized” waves.Among the samples, the researchers found some where viruses released from one infected cell seemed directly to attach to a neighboring host cell, presumably infecting it. In addition to such “virological synapses,” they also observed free virus particles that appear to have covered some distance between their “mother” cell and the cell that would become their target to infect.These images provide the first 3D ultrastructural details on HIV infection and virus production in a setting that closely resembles the gut of human patients. Some results confirm earlier findings from in vitro experiments — cells grown and infected in a petri dish — but others are seen for the first time and advance the understanding of how HIV infection spreads in real life.”To me, an important finding is that the majority of the viral transmission events within tissue involved free virus rather than virological synapses,” says Bjorkman. …

Read more

Adding blood pressure drug to standard antibiotics speeds up TB treatment

Aug. 29, 2013 — Infectious disease experts at Johns Hopkins have found, in studies in mice, that a drug better known as a treatment for high blood pressure and headaches effectively speeds up treatment of TB when added to the standard, daily antibiotic regimen. Test animals were cured in four months instead of the usual six.Researchers say that if clinical trials starting later this year in India, a country heavily burdened by the highly contagious lung disease, prove successful, then the shortened treatment time with verapamil, a so-called calcium channel blocker, used in combination with antibiotics isoniazid and rifampin, could make it easier for infected people to complete their drug therapy as prescribed. The experts note that antibiotics for TB do not work if treatment is interrupted or if people stop taking their medication. Improved drug adherence, they say, could also prevent the buildup of drug-resistant strains of TB, caused by Mycobacterium tuberculosis, which is now estimated to kill a million people each year, mostly in the developing world.”Our results show that verapamil is a good drug candidate as an add-on therapy with antibiotics for TB, a global disease in urgent need of new treatment options,” says study senior investigator and infectious disease specialist William Bishai, M.D., Ph.D. Bishai’s team’s latest findings are set to be published in the Sept. 1 edition of the American Journal of Respiratory and Critical Care Medicine.Bishai, a professor at the Johns Hopkins University School of Medicine and its Center for Tuberculosis Research, says that drug treatment options for TB are “too few,” and limited to about a dozen older antibiotics, some with serious side effects. Bishai, who also is a Howard Hughes Medical Institute Lab Head at Johns Hopkins, says verapamil has been around for some 40 years, so its side effects — such as too-low blood pressure — are well-known. He says the clinical trial in India, primarily a safety study to determine a minimum effective dose, will be pivotal in clarifying the drug’s “true potential” as an add-on therapy in TB.Lead study investigator and immunologist Shashank Gupta, Ph.D., says the study results also suggest that verapamil, commonly sold under the brand names Isoptin, Verelan, Calan, Bosoptin and Covera, could be a good drug candidate for combination therapy studies with multidrug-resistant forms of TB.Gupta, a postdoctoral fellow at Johns Hopkins, says verapamil is known to work as an efflux pump inhibitor, making bacteria more susceptible to antibiotics and killing by immune cell macrophages, but whose precise workings remain unknown. He says the research team investigated verapamil’s potential as a TB therapy after another study showed that increased efflux pump action promoted drug tolerance to TB, minimizing antibiotics’ effectiveness.Among the latest study’s other key findings were that verapamil accelerated killing of TB bacteria 10-fold after two months of treatment. …

Read more

Memory-boosting chemical identified in mice: Cell biologists find molecule targets a key biological pathway

June 14, 2013 — Memory improved in mice injected with a small, drug-like molecule discovered by UCSF San Francisco researchers studying how cells respond to biological stress.The same biochemical pathway the molecule acts on might one day be targeted in humans to improve memory, according to the senior author of the study, Peter Walter, PhD, UCSF professor of biochemistry and biophysics and a Howard Hughes Investigator.The discovery of the molecule and the results of the subsequent memory tests in mice were published in eLife, an online scientific open-access journal, on May 28, 2013.In one memory test included in the study, normal mice were able to relocate a submerged platform about three times faster after receiving injections of the potent chemical than mice that received sham injections.The mice that received the chemical also better remembered cues associated with unpleasant stimuli — the sort of fear conditioning that could help a mouse avoid being preyed upon.Notably, the findings suggest that despite what would seem to be the importance of having the best biochemical mechanisms to maximize the power of memory, evolution does not seem to have provided them, Walter said.”It appears that the process of evolution has not optimized memory consolidation; otherwise I don’t think we could have improved upon it the way we did in our study with normal, healthy mice,” Walter said.The memory-boosting chemical was singled out from among 100,000 chemicals screened at the Small Molecule Discovery Center at UCSF for their potential to perturb a protective biochemical pathway within cells that is activated when cells are unable to keep up with the need to fold proteins into their working forms.However, UCSF postdoctoral fellow Carmela Sidrauski, PhD, discovered that the chemical acts within the cell beyond the biochemical pathway that activates this unfolded protein response, to more broadly impact what’s known as the integrated stress response. In this response, several biochemical pathways converge on a single molecular lynchpin, a protein called eIF2 alpha.Scientists have known that in organisms ranging in complexity from yeast to humans different kinds of cellular stress — a backlog of unfolded proteins, DNA-damaging UV light, a shortage of the amino acid building blocks needed to make protein, viral infection, iron deficiency — trigger different enzymes to act downstream to switch off eIF2 alpha.”Among other things, the inactivation of eIF2 alpha is a brake on memory consolidation,” Walter said, perhaps an evolutionary consequence of a cell or organism becoming better able to adapt in other ways.Turning off eIF2 alpha dials down production of most proteins, some of which may be needed for memory formation, Walter said. But eIF2 alpha inactivation also ramps up production of a few key proteins that help cells cope with stress.Study co-author Nahum Sonenberg, PhD, of McGill University previously linked memory and eIF2 alpha in genetic studies of mice, and his lab group also conducted the memory tests for the current study.The chemical identified by the UCSF researchers is called ISRIB, which stands for integrated stress response inhibitor. ISRIB counters the effects of eIF2 alpha inactivation inside cells, the researchers found.”ISRIB shows good pharmacokinetic properties [how a drug is absorbed, distributed and eliminated], readily crosses the blood-brain barrier, and exhibits no overt toxicity in mice, which makes it very useful for studies in mice,” Walter said. These properties also indicate that ISRIB might serve as a good starting point for human drug development, according to Walter.Walter said he is looking for scientists to collaborate with in new studies of cognition and memory in mouse models of neurodegenerative diseases and aging, using ISRIB or related molecules.In addition, chemicals such as ISRIB could play a role in fighting cancers, which take advantage of stress responses to fuel their own growth, Walter said. Walter already is exploring ways to manipulate the unfolded protein response to inhibit tumor growth, based on his earlier discoveries.At a more basic level, Walter said, he and other scientists can now use ISRIB to learn more about the role of the unfolded protein response and the integrated stress response in disease and normal physiology.Additional UCSF study authors are Diego Acosta-Alvear, PhD, Punitha Vedantham, PhD, Brian Hearn, PhD, Ciara Gallagher, PhD, Kenny Ang, PhD, Chris Wilson, PhD, Voytek Okreglak, PhD, Byron Hann, MD, PhD, Michelle Arkin, PhD, and Adam Renslo, PhD. Other authors are Han Li, PhD, and Avi Ashkenazi, PhD, from Genentech; and, Karim Nader, PhD, Karine Gamache, and Arkady Khoutorsky, PhD, from McGill University. The study was funded by the Howard Hughes Medical Institute.

Read more

Utilizzando il sito, accetti l'utilizzo dei cookie da parte nostra. maggiori informazioni

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close