Welcome to the Future!

In general, there are two main forms of “being sick”—a bacterial infection which most know can be treated through use of antibiotics and a viral infects in which case…just go back to bed because there’s nothing you can do. Well, welcome to 2010 America! A recent publication in PNAS, the Proceedings of the National Academy of Sciences in the United States of America explains current research being performed using bacterial vectors as a mechanism to deliver RNase P-based ribozymes into specific human cells and inhibit viral infections (1).

In a nutshell a virus is an infectious agent that hijacks the cellular mechanisms of another type of cell. Most every organism can be infected by viruses including plants, bacteria, animals and humans. The basic structure of a virus is simple: protein coat and genetic material (hence the big controversy of whether or not they’re “living”) however some may contain an envelope of membranous material and surface proteins that often act in antigen-recognition of immunological responses. The genetic material of viruses is perhaps one of the reasons they’re so difficult to treat. Many viruses contain DNA, however some crazies out there have RNA and either of these can be single stranded, double stranded, linear or circular on top of the many recombinations, horizontal gene transfers, reassortments and mutations.
Viruses do not perform their own metabolism but, as mentioned earlier, hijack the host’s cellular machinery through the same basic process: Attachment to the outer membrane of the cell, penetration of the membrane into the cell’s interior, uncoating in which the viral protein coat, called a capsid, is removed to avoid immune defenses and inject the viral genome; Replication in which the genes injected are transcribed and translated via the host cell and the subsequent proteins assist in viral replication and finally release in which the host cell cannot continue producing viral proteins and burst, thus spreading the virus to surrounding cells (2).

Because the virus eliminated its protein coat, targeting the problem becomes especially hard. Also because it is host cells producing the viral proteins and subsequent virus for spread, eliminating host cells is the ideal, however not really an option (you can’t go off killing all your cells….Bad news Bears!) So for a while there, people just slept until their immune systems could “kick in” and get the job done. For some, however, that was not a possibility and the flu virus meant certain death. Sure there were some basic antiviral drugs that could target and prevent DNA replication, but often were not site-specific and ended in very gruesome side effects. Vaccines also help in which attenuate (dead or weakened) virus was pre-introduced before a nature infection could take place so the immune system could build antibodies before a real problem him. That’s really convenient…until the strain isn’t actually weakened or dead and you just infected an innocent human being with polio, THANKS CUTTER LABORATORIES! (3) Regardless most viral infections cannot truly be “cured” or even treated for that matter…until February 2010.

Yong Bai, Hongjian Li, Gia-Phong Vu, Hao Gong, Sean Umamoto, Tianhong Zhou, Sangwei Lu and Fenyong Liu recently published their research on Salmonella-mediated delivery of RNase P-based ribozymes for inhibition of viral gene expression and replication in human cells (1).

According to Bai et al, the main challenge of gene therapy is finding approached to deliver nucleic-acid based gene interfering agents like interfering RNAs and ribozymes. Interfering RNAs are small single stranded RNAs that are complementary to a sequence of mRNA. Upon being delivered, these single stranded RNAs find and bind with mRNA preventing translation and tagging it for destruction via the RNA-induced silencing complex (RISC) (4). Ribozymes (or RNA enzymes) are RNA molecules capable of catalyzing a reaction. These reactions are more than often hydrolysis of phosphodiester bonds including those in the backbones of complementary sequences, thus preventing translation of mRNA (I don’t know like maybe that of VIRAL INFECTIONS?! Hmmm) (5).


Anywho, back to the research. In the article mentioned above, human cytomegalovirus (HCMV) was used as the target virus for study. A functional RNase P ribozyme called M1GS was constructed which targets the mRNA essential in synthesizing capsid proteins: the scaffolding protein and assembling which are required for the protein coat of the HCMV. This ribozyme was expressed using Salmonella strains and up to 90% of viral protein expression as well as about 5,000-fold reduction in viral growth was seen in the treated cells and NOT in untreated.

HCMV is an opportunistic pathogen which can lead to death in immunocompromised, neonates, AIDS patients and transplant recipients. In these patients the HCMV infests macrophages and monocytes resulting in lysis and spreading of the infection. To combat infections like this, Nucleic-acid based gene interference (the ribozymes and RNAi mentioned earlier) are used for specific targeting of infected cells. The problem with these mechanisms is getting them to the cells. Many of the vectors used now-a-days are attenuated or modified viruses which have many problems previously described. The research done here used the invasive bacteria Salmonella which has the ability to enter human cells and transfer genetic material. These bacteria have been used for anti-tumor small hairpin RNAs in cancer therapy due to their ability to specifically target dendritic cells, macrophages and epithelial cells. Using these bacteria to deliver ribozyme plasmids to macrophages infected with HCMV, it was seen that not only are capsid-scaffolding proteins and assmeblin necessary for viral replication but also that delivery of ribozyme via Salmonella to HCMV-infected cells resulted in effective inhibition of gene expression and replication and may demonstrate a novel method for ribozyme delivery and treatment of viral diseases.







1. Bai, Yong, et al. "Salmonella-mediated delivery of RNase P-based ribozymes for inhibition of viral gene expression and replication in human cells ." Proceedings of the National Academy of Sciences in the United States of America . 107.16 (2010): 7269-7274. Print.
2. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/V/Viruses.html
3. http://en.wikipedia.org/wiki/Polio_vaccine
4. http://en.wikipedia.org/wiki/RNA_interference
5. http://en.wikipedia.org/wiki/Ribozyme#Activity

Michael Specter: The danger of science denial | Video on TED.com

Michael Specter: The danger of science denial | Video on TED.com

I just though I would post this video on science denial since we touched on it earlier in the semester. It is very interesting. The man speaking in the video is Michael Specter. He is a staff writer for the New Yorker and has recently written a new book called "Denialism" touching on some major issues of why we have begun to fear science instead of accept all the advances that we have.

Oh those poor bats...

As summer approaches, I can't help but think of going caving again. Crawling through tight spaces and climbing down cliffs is such an adrenaline rush; plus it's a great way to learn some pretty cool science. Please allow me to encourage you to go!

I hear people saying all the time that being short has its perks, but I know of one situation in which it's a curse. While at Mammoth Cave, our guide took us to a drop which they call the Lion's Head. As you can see, I'm (yes, that's me!) hanging on for dear life (actually I'm having the time of my life)! Even though the floor is about 5 feet under me I still don't want to fall. Plus there's a huge stalagmite below not pictured prepared to attack, giving the formation the title of the Lion's Head. However, the tour guides there are helpful and make sure that you get down safely. Anyway, aside from the crazy expeditions, you can learn many things from going on a tour like this. You can learn about the glittering water in the cave that contains many organisms and certain minerals. You can also learn about certain epidemics that are affecting certain native species. For example, bats living in the caves are starting to contract a particular fungus. This fungus grows on their noses, killing them and affecting their natural behavior. This is known as the white nose syndrome and has effected many bats. It can be transferred to bats via humans. The syndrome also spreads amongst bats. I find this interesting and important because the bat population is steadily decreasing due to this malicious killer. Since the introduction of the white nose syndrome, the bat population in 2 New York caves was found to be reduced by 75% [1]. This disease has spread to other caves in North America and researchers are studying this more to gain more of an insight into what it is and how to treat it.

I did a little more research on the subject because I want to know more about it. I found one paper by Courtin et al titled "Pathologic Findings and Liver Elements in Hibernating Bats With White-Nose Syndrome" that discussed this disease. The paper gave a great overview of the disease and did a nice job This malicious disease first appeared in 2006 in a New York cave and then spread throughout the Northeast during the winters of 2007 and 2008. By 2009 it had found its way to Pennsylvania and Virginia [1]. The bats most commonly affected are the little brown, northern-long eared, and big brown species. When they examined some of the bats, they found lesions on the muzzle and wings. Geomyces destructans, a white fungus, was found around these lesions. Behavioral differences were also seen. Some of the bats flew out of the caves in the middle of winter during hibernation and some even flew during the day. What is interesting about this study is that they analyzed the lesions and looked to see if there were any metals or minerals at abnormal levels. This could correlate to the disease [1].

For this experiment, they collected dead or almost-dead bats with the disease. They collected two groups: one for microbiological examination and the other for metal and mineral analysis. In the examination group they found that the dead bats had fungus that started to penetrate the basement membrane of the root sheaths and into surrounding tissues, but this was not the case in the almost-dead bats. They also found that the body weights of the bats were on the low side. They found that the fungal hyphae grew along the hair follicles and also went along the surface of the skin in hairless places such as on the wings. One interesting thing Courtin et al discussed was that this type of fungus is that it can extend into the epidermis, near the noncorneal layers as well as the sebaceous glands [1]. While examining the bats, they also found that there was fungus growing, as well as gram-negative bacteria, in the dermal-epidermal interface. They also found no organ failure in these bats.

In the second group, they analyzed the livers for different metals. They found that most metal levels varied and were not consistent. Courtin et al collected several different species of bats (they are listed above). They found, along with other labs, that the little brown bat is more commonly afflicted with the fungus, whereas the the big brown bats are not. They believe this could be due to the areas in which the big brown bats hibernate. They hibernate in drier, ventilated areas whereas the little brown bats do not. So, in conclusion, their home choice could have an effect on their susceptibility to this fungus [1].

I don't know about you, but I can't help but think of these poor bats. So, if you do go caving, please, don't touch the bats. Even though the Mammoth Cave bats have not seen this fungus as of now, there is still the potential that it could be introduced.

[1] Courtin, F., Stone, W. B., Risatti, G., Gilbert, K., & Van Kruiningen, H. (2010). Pathologic findings and liver elements in hibernating bats with white-nose syndrome. Veterinary pathology, 47(2), 214-219.

Photo of bat from Courtin et al, (2010).