Monthly Archives: December 2010

Guest Blogger

Still no cure, but possibly a better method of diagnosis for “mono”  

Contributed by Guest Blogger: L. Kantor ’14

Infectious mononucleosis was first brought about in 1889 with the expressed symptoms of pharyngitis, fever, and lymphadenopathy.  In 1920, it was discovered that many patients with “mono” had similar blood films, demonstrating an absolute lymphocytosis with abnormally abundant cytoplasm in mononuclear cells.  In 1932, the monospot test, a form of the heterophile antibody test, began being used to test for the disease.  Epstein-Barr virus, the currently identified cause of infectious mononucleosis, was identified in 1968.  The virus causes a high white blood cell count with a relative lymphocytosis, which is usually confirmed by a positive monospot test.  However, it has recently been suggested that a lymphocyte to white cell count (L/WCC) ratio could be a quickly available alternative test for the detection of infectious mononucleosis.  In a recent study, the L/WCC of a series of infected patients was compared with that of a similar number of patients with bacterial tonsillitis.  The researchers were trying to prove that a lymphocite/white cell count shows better specificity and sensitivity than the mononucleosis spot test.
One thousand monospot tests in patients with tonsillitis both in an outpatient and inpatient study were analyzed to compare L/WCC ratios in 500 positive and 500 negative results.  The lymphocyte counts and white blood cell ratio was significantly different in the positive and negative monospot groups.  The mean lymphocyte counts and white blood cell ratio in the positive group was 0.49 and the mean lymphocyte to white cell count ratio in the monospot negative group was 0.29.  A ratio of 0.35 had a specificity of 72% and a sensitivity of 84% for detection of the Epstein-Barr virus.  However, these results show that a higher ratio will give a greater specificity, but a lower sensitivity, and vice versa.  Therefore, the mean lymphocyte to white cell count ratio is not sufficient to diagnose or exclude infectious mononucleosis.
However, some questions still arise.  Could the tests be equally accurate but simply at different stages of the infection?  Would the same results occur before the patient showed symptoms of infection?  Or after the symptoms disappeared?

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Guest Blogger

A cure for cold sores?

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ContribUted by Guest Blogger: A. Parayannilam ’13

The cold sores many of us see on our mouths or faces at one point in our lifetimes are caused by the prevalent Herpes simplex virus Type 1(HSV1). More serious symptoms can develop if the virus infects the Central Nervous System, causing herpes encephalitis and damage to the brain. A recent study has shown how interferon delta (IFN-λ), a member of a group of proteins known as interferons (IFNs), can reduce infectivity of the virus in the Central Nervous System. The results of the study are promising: perhaps by recruiting the body’s own defenses, we can avoid the use of potentially unsafe antiviral drugs in treatment for the disease.
 
Researchers observed IFN-λ to significantly reduce the quantity of the virus found in infected cells of the central nervous system, specifically astrocytes and neurons. Researchers investigated the mechanism behind IFN-λ’s anti-HSV-1 effect and found that IFN-λ activated several Type 1 IFNs. Type 1 IFNs play critical roles in our innate immunity and defense against viruses. To test the significance of Type 1 IFNs, researchers treated astrocytes and neurons with Type 1 IFN antibodies, essentially preventing IFN- λ from activating Type 1 IFNs in these cells. The antibody-treated cells became highly susceptible to infection, highlighting the importance of Type 1 IFNs in the virulence of the disease.
Another method by which IFN- λ reduces infectivity of the virus is by promoting cytokine signaling. Cytokine signaling is a method of intercellular communication cells use to warn each other of infection. Because HSV-1 suppresses cytokine signaling, uninfected cells aren’t able to prepare themselves for possible infection, making these cells more susceptible to infection.
The study raises a number of questions. The researchers discuss the interplay between HSV-1 and interferon delta, but how about the interplay between HSV-2 and interferon delta? The study examines how interferon delta can reduce infectivity in astrocytes and neurons– can interferon delta similarly reduce infectivity in cells outside the Central Nervous System? Is this a fix to the annoying, chronic cold sores that affect the majority of us?
 

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A new host for Ebola

Contributed by Guest Blogger: S. Brucker ’14

Ebolavirus is a relatively new threat to the living world and therefore still enigmatic to the medical community in many ways. The question of where Ebolavirus strains come from remains unsettled, but they are thought to mainly infect humans and non-human primates. However, the feasible targets for Ebola expanded when researchers ran tests on pigs in the Philippines. A recent porcine epidemic in the Philippines lead the worried government to contact the USDA along with other mammalian medical laboratories for help diagnosing the problem. The disease was originally thought to solely be Porcine Respiratory and Reproductive Syndrome Virus (PRRSV) also known as “Blue Ear Disease,” but as it turns out, the swine were carrying something else. A technique called microarray analysis was used to identify any other pathogens infecting the pigs. This process consists of comparing an unknown genetic sample to an array of signature sequences belonging to known pathogens. The results of this test showed 28 out of 28 positive matches of the pigs’ genetic samples to signature Reston Ebolavirus (REBOV) sequences. This finding came as a surprise to a scientific community who believed Ebola to only infect primates. This seemingly small discovery has large implications for the way we think abut Ebola. Although Reston Ebolavirus has not yet been shown to infect humans, it is of concern that Ebola strains are appearing in the human food chain. This discovery leads to many questions that must be answered. How long has Ebola been able to infect pigs? If it recently evolved to include pigs in its host tropism, then what is different about this strain? What else can it affect? Are more virulent strains also going to evolve to expand host range? The biggest danger about Ebola is the fact that there is so much that we do not know about it, and until we answer these questions, the virus will be a constant threat.
 

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Exit Pathway for Cancer-inducing Virus

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Contributed by Guest Blogger: M. Aradi ’14

It has been recently discovered that exosomes are used by virally infected cells and cancer cells to manipulate their environment.  The Epstein-Barr Virus, or EBV, significantly affects cell growth and leads to types of malignant cancer. The major oncogenic protein of EBV has been found to be LMP1, as it is often expressed with EBV cancers. Viruses use the exosomal pathway to leave cells and evade immune responses. It has been observed that LMP1 contributes to cell growth through the exosomal pathway. Exosomes generally transfer mRNA, micro RNA (miRNA) and proteins to other cells to affect cell proliferation, cell to cell communication and tumor cell invasion.  LMP1’s most important target is the cellular EFGR protein, which is a cell growth-signaling receptor.  EFGR is secreted from cells in exosomes, and then is taken up by epithelial cells where it functions for cell-growth pathways. It has also been discovered that cells infected with EBV release exosomes that contain LMP1, which inhibits T-cell functions.  

The question was: What are the effects of LMP1 on exosomal composition and biochemical properties that support EBV cell infection?  The test included two groups of EBV cells;  first group contained low levels of LMP1, and the second group had higher expression levels of LMP1.  The two group exosomes were tested for uptake potential by other cells, and it was found that the second group exosomes had a higher level of uptake.  This shows that LMP1 plays a role in controlling exosomal proteins involved in cell adhesion and interaction.  The two groups were exposed to epithelial cells and were observed for how the host cell signaling pathways were affected.  It was found that the LMP1 exosomes induced higher levels of cell growth signaling pathways in recipient cells, showing that LMP1 contains protein factors that induce cell growth necessary for tumor growth and metastasis.

Although the study revealed certain key mechanisms of LMP1 function with EBV, further questions involve which specific exosomal proteins are manipulated by LMP1? How do LMP1 and EFGR interact to successfully induce cell growth?  Which structure or pathway could possibly be targeted to prevent the spread of EBV and its tumor-inducing factors in efforts to cure cancer?

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MicroRNA and mosquitos: Possible method for arbovirus restriction?

Contributed by Guest Blogger: C. Romero ’14

Recent research has shown that microRNA miR-275 in the Aedes aegypti mosquito is necessary for blood digestion and egg development. A. aegypti is the most common vector of arboviruses, or ARthropod-BOrne viruses, which include the dengue fever and yellow fever viruses that infect millions and kill thousands each year. Mosquitoes require vertebrate blood to produce eggs, making them good vectors for human diseases. Blood feeding and egg maturation occur in cycles, where blood feeding is required to trigger a step in the process of egg production. In A. aegypti, researchers from University of California, Riverside led by Alexander Raikhel found that miR-275 plays a critical role in this regulatory system.
MicroRNA is a relatively recent discovery, having been first identified in 1993. It appears as if their primary function is post-transcriptional regulation, in which microRNA sequences bind to complementary mRNA. The outcome has come to be known as translational repression or gene silencing, where mRNA is kept from reaching ribosomes and producing proteins, thus interrupting gene expression.
The researchers developed a RNA inhibitor specific to the microRNA molecule, known as an antagomir, to bind to miR-275 before it could silence its corresponding mRNA. By injecting female A. aegypti with this antagomir, blood digestion, fluid excretory function and egg production were all severely inhibited.
This discovery opens new doors to control of the spread of arboviruses, where removal of a single tiny molecule can limit the mosquito’s function at a fundamental level.
Many new questions arise from this research, some of which are already pending investigation by Raikhel’s UC Riverside team. The researchers plan on looking into the particular mRNA that miR-275 targets, and thus find the genes that regulate the blood-meal-mediated egg maturation cycle and see what role they play. Raikhel also plans on looking into the mechanism that underlies the activation of miR-275.
Further off, however, are considerations of how to bring this finding into the real world with a new mosquito control method. New innovations in microRNA research will surely bring us closer to harnessing its power, much as the scientific community has done in DNA genetics.

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Septic Tanks: urban breeding grounds for virus-carrying mosquitoes

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Contributed by Guest Blogger: L. Herrera-Torres ’14

Like in several other landforms in tropical regions, Puerto Rico is victim to seasonal increases in the Dengue fever and West Nile Virus, which are transmitted via the mosquitoes Aedes aegypti and Culex quiquefasciatus respectively. In order to test whether or not active septic tanks with raw sewage provide an adequate environment for the development of mosquitoes (particularly Aedes aegypti) and therefore aid in the spread of these diseases, a test was conducted in a southern municipality of Puerto Rico, called Salinas. In the community of Playa-Playita 89 septic tanks with varying structural integrity and water quality were sampled for the presence and abundance of mosquito larvae using floating funnel traps and 93 septic tanks were tested for the presence and abundance of adult mosquitoes using screened, plastic emergence traps.
Predictably, Culex quinquefasciatus, the vector of West Nile virus, which has been proven to thrive in polluted waters, was found in 74% of the septic tanks in larval form and in 97% in adult form. However, the results of vector for Dengue fever (the main focus of the experiment) were more surprising.
Previously Ae. Aegypti was known to be well adapted to urban areas and were often found in artificial containers, but it was still generally accepted that these larvae developed in clean water. However in 18% of the septic tanks sampled revealed that Ae. Aegypti was present in this water despite its contamination and had a positive association with the cracking of septic tank walls, uncapped tanks, and larger tank surface area. Similar results were found for Ae. Aegypti adults. 49% of the tanks showed both their presence and abundance as well as their positive correlation with cracking, uncapping, and septic water pH. The correlation between the amount of larvae collected from the septic tanks and the amount of adult mosquitoes recorded strongly insinuates that this environment is conducive to mosquito reproduction and development and is not just a resting place as others have suggested.
These findings led the researchers to believe that Ae. Aegypti can develop in sewage water and that septic tanks provide ideal conditions for mosquito productivity and can serve as potential to maintain dengue transmission during the dry season.

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Shotgun Approach to Keeping Viruses Off

Contributed by Guest Blogger: J. Moon ’14

The amount of human resources to develop therapeutics on a single-pathogen basis is limited. A single-pathogen approach is made more impractical with the ever increasing number of viral pathogens. But there are alternatives to this approach: broad-spectrum antivirals that target various groups of viral pathogens. Recent studies have found that LJ001, a broad-spectrum small molecule antiviral , is effective against numerous lipid enveloped viruses including Influnza A, filoviruses, poxviruses, areanviruses, bunyaviruses, paramyxoviruses,flaviviruses, and HIV-1. Against nonenveloped viruses, however, LJ001 has no effect.
The LJ001 antiviral acts by attaching to the membranes of both the cell and virus and inhibits virus-cell fusion. The antiviral begins by injecting itself into the lipid bilayer of the cell. But it is only activated upon contact with the other antiviral on the virus. Once activated, the molecule damages the lipid membrane of the virus. This damage to the lipid membrane results in loss of fluidity/rigidity that is necessary to undergo fusion into the cell. Since viral membranes do not have the ability to repair themselves, the viral membrane is deactivated by the LJ001 antiviral. Therefore, LJ001 is effective against various enveloped virus groups including the previously mentioned.
One of the first experiments was to see the comparative effects of the antiviral on viruses. The experiment consisted of testing enveloped and nonenveloped cells. The conclusion reached after data collection was that the LJ001 antiviral has no effect on nonenveloped viruses. Experiments were also conducted to determine whether or not the LJ001 antiviral was acting on the virus or on the cell. This included the introduction of the antiviral to the cell culture before and after attachment of the virions to cells. Results showed high infection rates near 100% for the cell cultures introduced to the antiviral after the virus attachment whereas infection rates for the cell cultures pre-treated with the antiviral were near zero. Experiments were also conducted with the antiviral being applied to a wide variety of large-scale lipid enveloped viruses. These results showed that there are varying degrees of effectiveness across different viruses. The conclusions reached on these observations are that LJ001 affects only non-enveloped viruses on varying degrees of effectiveness and that the LJ001 deactivates virions and prohibits virus-cell fusion.
What impact does this have on these enveloped virus groups? Although the lipid membrane of a virus remains fairly static from generation to generation, is it likely or possible that these viruses will somehow develop mechanisms to counter the effect of the antiviral? What are some possibilities?

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Locking Viruses into Endosomes – An Advancement in Influenza Therapeutics

Contributed by Guest Blogger: E. Cesanek ’13

Enveloped viruses have developed a clever technique to enter host cells and release viral genome into the cell for replication. In order to enter the cell, a virus particle takes advantage of the endosomal transport system, in which large particles bud into the cell after being enclosed by a section of the cell’s lipid membrane. Then, the acidic environment of the endosome provides the cellular energy needed to fuse the viral membrane. This process requires energy because it involves changing the conformation of the viral membrane to bend it towards the lipid membrane enclosing it. Clearly, membrane fusion is an essential part of the viral life cycle as it is the only way viral genome can be released into the host cell.
As a result, lots of recent research has been directed at identifying molecules that effectively inhibit membrane fusion. A crystallography study has helped to elucidate the mechanism by which tert-butyl hydroquinone (TBHQ), a small molecular compound that binds to influenza HA envelope protein, inhibits membrane fusion and reduces viral infectivity. Unfortunately, TBHQ only works on influenza group 2 subtypes (e.g., H3 or H14), which have a special hydrophobic binding pocket for the molecule. Once there, TBHQ works as a kind of “molecular glue,” stabilizing the structural conformation of the HA envelope protein. As a result, the amount of energy required for membrane fusion is increased to the point that HA is unresponsive to the acidic environment of the endosome.
The findings of this study may provide a framework for structural design of effective membrane fusion inhibitors for use as therapeutics against enveloped viruses. Molecular compounds that are structurally similar to TBHQ are both easier to synthesize and have more drug-like chemical properties than other types of membrane fusion inhibitors (e.g., enfurvirtide, an HIV-1 membrane fusion inhibitor).
However, it is important to remember that the TBHQ binding site is only one possibility for such conformation-locking molecules. Further research should explore alternative sites, and also explore the problem of viral resistance developing against TBHQ inhibition of membrane fusion.

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Crop Virus Bamboozles Vectors

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Contributed by Guest Blogger: H. Tran ‘14

A virus’s ability to replicate is largely dependent on the health of its host; a virus cannot proliferate in an immobile or dead organism. For this reason, viruses have a vested interest in doing as little damage as possible to ensure easy transmission. Vector-borne pathogen transmission between plants is seemingly ideal for viruses as particles can move freely from one diseased host to another potential host. However, infected plants do not typically attract vectors in the first place, as they don’t promise healthy feeding. One common crop virus is able to sidestep this obstacle by causing its diseased host to release a greater number of vector-attractants without sacrificing virulence.
It was recently discovered that the widespread plant pathogen cucumber mosaic virus elevates the release of host volatiles, or odorous chemicals, that attract vectors. Researchers measured the rates of aphid population growth on and emigration from healthy and infected plants. It was discovered that aphids were initially more attracted to the infected plants than to the healthy plants. However, the aphids dispersed rapidly from the diseased hosts after feeding. This form of transmission is known as non-persistent transmission because rather than long-term feeding and colonizing on the plants (persistent), the vectors are repelled by the inferior quality and move on to other plants (non-persistent). This type of transmission is advantageous for CMV as it facilitates easy transmission from one host to another.
It is known that the non-persistent nature of CMV transmission encourages quicker spreading between host and uninfected plants. It remains unclear, however, whether the elevated level of volatile emission is a result of an adaptation to hosts for the purpose of manipulating vectors or simply an accidental by-product of infection. In either case, the phenotypic change resulting in higher levels of volatile release has the capacity to significantly alter ecology, agriculture and human health. Damaged crops are less nutritious and unmarketable, making CMV a vastly undesirable pathogen.
Which is a more probable explanation for the deceptive mechanism by which the virus enhances host-vector interaction: manipulative adaptation or coincidentally advantageous evolution? What does your conclusion tell us about the evolution of this virus, or viruses in general? Knowing what was recently discovered about CMV, can anything be done to prevent the cultivation of diseased crops?

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Social Spread of HIV

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Contributed by Guest Blogger: T. McKinnon ’14

In the mid-1980’s, businesspeople were crossing the Tanzania/Uganda border, and caught a disease. This disease spread through all of Tanzania after 2 years, and this is the birth of the HIV/AIDS epidemic. The question that was being asked in this research is how rampant HIV is in two differing economic classes, the “rich” and the “poor,” and in which is it more prevalent. The model created by studying the transmission of this disease through differing socio-economic classes is to see the impact HIV/AIDS has on one economic class versus another, and whether transmission is easier, harder, faster, etc. in different social classes.
The experiment conducted worked like this: a total population of individual is accounted for, divided into susceptibles, infectives (infectious), pre-AIDS and AIDS patients. These people are then divided into pre-AIDS hospitalized patients and AIDS patients seeking no hospitalization, because this is common in lower economic classes. From then, the spread and rate of infection of HIV and the spread of AIDS is measured among these separate groups, whether it is initial infection or development into full blown AIDS.
Through extensive experimentation, HIV/AIDS was found to be more prevalent among wealthier populations, but it spreads faster among the lower classes. I find it very interesting that this disease is not more prevalent and spreads faster in the lower classes. In the upper class, people can more readily afford the treatments and medications than people living in lower classes with less money.
The researchers acknowledged that this experiment was by no means exhaustive. I would like this experiment to expand to how race and sexuality interact with social class in the spread and prevalence of HIV/AIDS or if race has anything to do with it, both separately and together. I also would like to know how level of sexual activity among social class propagates HIV spread, and if the members of the upper class were more or less sexually active, or participated in more unsafe sexual practices than those of the lower class, or if it was the other way around.

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