Better Treatments for Rheumatoid Arthritis Not Too Far Off

Rheumatoid Arthritis (RA) is an inflammatory autoimmune disease that most often targets peripheral joints, frequently resulting in pain, swelling, and possible deterioration and destruction of cartilage and bone located at the joint. RA afflicts more than 1.3 million people in the United States alone, and the disease is most prevalent among women and the elderly. For over 60 years, RA has been widely treated non-selectively with glucocorticoids (GCs), such as methotrexate, a type of steroid hormone, because of their unrivaled, potent anti-inflammatory effects. Despite the successful anti-inflammatory effects that GCs have on the joints of afflicted patients (in fact, GCs are successful in just about every type of inflammatory ailment), it is a costly treatment, and there are numerous, severe side effects due to their non-selective nature, including immunodeficiency, high blood sugar, and increased skin fragility and bruising, among others. Consequently, there is currently a necessity for research into possible steroid therapies better targeted to healing RA with greater efficiency and fewer adverse side effects.

When RA is treated with GC steroid hormones, the hormone binds to a glucocorticoid receptor (GR) located in host cells (and expressed nearly universally in all vertebrate cells). Once being bound by a GC, the GR then translocates into the host cell nucleus where it can act as a transcription factor, subsequently altering gene expression and helping to dampen the host immune response and reduce inflammation at the site of RA. The GR may carry out this function via two different modes of action: it may dimerize, or split into two separate subunits, and then bind to the gene promoter of GC-regulated genes, or it may remain as a single unit and interact with other DNA-bound transcription factors, thereby altering gene expression to induce anti-inflammatory function.

While it is well understood that GCs induce potent anti-inflammatory effects, the specific cells targeted by GCs and their underlying mechanisms are poorly characterized. Just yesterday, a study was published in the Proceedings of the National Academy of Science by Baschant and colleagues that identifies a potential mechanism by which GCs actually carry out their anti-inflammatory function. The paper suggests that the GR in T cells, which are cells that contribute to the inflammatory state in joints, is critical for the suppression of inflammation by GCs, and that the dimerization of GRs is necessary for the GC’s anti-inflammatory effects. To achieve this, the authors utilized a mouse model in which they used an antigen-induced arthritis (AIA) to mimic the severe inflammation in joints that is characteristic of RA, and serves as a model to examine the mechanism by which GCs carry out their function.

Herd Immunity Renders Male Vaccination Against Human Papillomavirus Impractical

Human Papillomavirus, more commonly known as HPV, has been the topic of discussion most recently in reference to the ability to vaccinate against it and prevent its association with cervical cancer. There are certain strains of HPV that that are classified as high-oncogenic-risk (likely to cause cancer). Risk of cervical cancer is the main force behind the push for vaccination against HPV. HPV infection types such as HPV-16 and -18 are a necessary cause of cervical and other types of cancers (1). Because it is so dangerously associated with cervical cancer, HPV infection presents a serious burden for females. Others like HPV-6 and -11 are low-oncogenic-risk but cause other symptoms like genital warts, and some cancers found in men (penile cancer).

Young girls around age 12 have begun receiving the vaccine against HPV in order to combat the associated diseases like cervical cancer. Results suggest that so far it is effective. There are two prophylactic vaccines currently used in females: the bivalent and quadrivalent vaccines. The bivalent protects against HPV -16/18 and the quadrivalent protects against HPV – 16/18/6/11. Previous research has determined that these vaccines are efficacious and cost-effective in preadolescent girls. Currently, there is debate over whether or not young boys should also be vaccinated against HPV. Recent studies have also found the HPV quadrivalent vaccine to be 86% effective in young males, which presents another option for vaccination against HPV infection (2). Therefore, Brisson, et al. (2011) wanted to investigate the potential incremental impact of vaccinating boys against HPV.

Combination Therapy--Giving Cancer the 1-2 Punch

It has been well documented that many cancer cells over express Intreleukin-13 receptors—in particular 4T1 breast carcinoma cell lines and MCA304 sarcoma cell lines (Joshi, 2000). Interleukin-13 (IL-13) is a small, cell-signaling protein that is derived from a Th2 immune response that binds to Interleukin-13 receptors (IL-13R). IL-13Ralpha2 is one of two receptor subunits of the IL-13R complex. This subunit binds IL-13 with high affinity to mediate a signal transduction, ultimately resulting in the production of TGF-beta (Fichtner-Feigl et al., 2006).

Recent studies have focused on targeting IL-13R of tumor cells in order to control the progression of cancer. For this reason, an immunotoxin, IL13-PE, was formulated by recombining IL-13 and Pseudomonas exotoxin in order to target IL-13R expressing tumor cells (Kawakami et al., 2001). IL13-PE is able to specifically recognize IL-13Rs, limiting toxicity to cancerous tissues (Puri et al., 1996). IL13-PE acts to inhibit protein synthesis and cause cell death of IL-13 expressing cells by irreversibly ADP-ribosylating the diphthamide residue of elongation factor 2 (Fichtner-Feigl et al., 2006).

Vaccines have also been utilized as an alternative method to induce a strong immune response against tumor cells. T cells and B cells are leukocytes that are responsible for regulating the immune response by recognizing harmful entities in the body and carrying out their destruction. Antitumor vaccines are intended to incur an antigen-specific immune response against a tumor peptide by priming the immune system to activate T cells and B cells (Nakashima et al., 2010). By stimulating the production of T cells and B cells to recognize tumor cells, the proliferation of tumors can be controlled. One particular vaccine, IL-13Ralpha2 DNA vaccine, has shown to be effective in limiting tumor growth in both 4T1 breast carcinoma cell lines and MCA304 sarcoma cell lines (Nakashima et al., 2010).

A novel way to fight an old foe: expression of TCRs on macrophages in granulomatous responses

Tuberculosis is caused by the bacteria Mycobacterium tuberculosis, and is characterized by an infection of the bronchi (a part of the lungs) in which macrophages (a type of white blood cell) are unable to digest the bacteria. As a result, macrophages release cytokines, small proteins, that attract T lymphocytes, which kill cells by releasing "killer proteins" and create a granuloma (a collection of immune cells surrounding infected tissue) (Knechel 2009). Tuberculosis poses a threat to the health of the world: in 2007, there were approximately 1.77 million deaths from tuberculosis—the second highest death rate of any infectious disease (Glaziou et al. 2009). It is also a highly mutative pathogen: cases of extreme-multidrug resistant tuberculosis are common, and the treatment responses are usually poor, while the mortality rates are high (Telzak et al 1995).

A recent study by Beham et al. published in PLoS pathogens examined how T-cell receptors (TCRs), which recognize a protein-complex on other cells, on macrophages affect the formation of tuberculous granulomas. To begin the study, the researchers had to establish that monocytes, precursors to macrophages, and macrophages do in fact express T-cell receptors. To do this the researchers used antibodies, proteins that target specific molecules, targeted to TCRα/TCRβ and MHC-II (this is the protein complex recognized by TCRs). From this experiment, they were able to establish that approximately 5% of monocytes expressed TCRαβ (a type of TCR). Although the presence of TCRs in monocytes appeared to be promising, the researchers continued by testing monocyte-derived macrophages from three donors. These monocytes were activated using IFNγ and IL-4, both cytokines that are responsible for initiating inflammation. The researchers found that 5% of the naïve macrophages expressed TCRs, while 9% IL-4 of and 11% of IFNγ activated macrophages expressed TCRs.

Protect Your Unborn or Newborn Baby: Secondhand Smoking’s Association to Asthma

Do you know someone with asthma? Chances are that you do. In 2009, over 8% of the US population reported that they currently had asthma. Interestingly, asthma rates are the highest among children and teenagers (Akinbami et al., 2011). Allergic asthma in particular is the type of asthma that is most commonly found in children. Allergic asthma, also known as atopic asthma, affects the lower respiratory tracts. Inhalation of an allergen leads to the release of granules from sensitized cells called mast cells that are located in the mucus of a person’s nose or bronchi (which serve as passageways into his or her lungs). The release of these granules and other molecules favour inflammation. This causes abundant amounts of mucus to be secreted and the tightening of a person’s airways. Asthmatics routinely report feelings of constriction in their chest as well as wheezing. Given this information, you might ask the following question: what factors contribute to the development of allergic asthma? Exposure to cigarette smoke during fetal development and during a child’s infancy has been shown to be a risk factor for allergic asthma (DiFranza et al., 2004). Mice exposed to secondhand smoke (SS) early-on after birth also seem to develop respiratory infections (Phaybouth et al., 1006), and can be used as a model for this disease. The specific contributions of exposure to smoke that is either prenatal (before birth) or early postnatal (after birth) in the development of allergic asthma, however, is not well understood. Also, the specific way in which exposure to cigarette smoke leads to asthma is not understood in great detail. To shed some light on these topics, researchers decided to use a mouse model to study the development of allergic asthma (Singh et al. 2011).

STAT3β: Not Such A Downer

STAT3 is a transcription factor that has been of particular interest to oncologists lately for its promotion of oncogenesis through constitutive activation. STAT3 has two key residues that must both by phosphorylated by a kinase in order for the protein to dimerize into a homodimer or heterodimer and thus be active. The two residues, tyrosine 705 and serine 727, are both found on exon 23. STAT3 is activated by several interferons, cytokines, and growth factors.

An article published in the October 25, 2011 edition of PNAS explored the study of Dr. Francesa Zammarchi et al on the alternative splicing that leads to two isoforms of STAT3: STAT3α and STAT3β. Exon 23, which includes the two amino acid residues necessary for activation of the STAT3 TF, can be fully or partially included in the final product. If the entire exon is included, STAT3α is formed and the protein is fully functional. If the 55 amino acids at the end of exon 23 are excluded from the final product, then STAT3β is made. The premature termination of the protein causes serine 727, a necessary residue for phosphorylation and activation of the STAT3 protein, to be truncated. This renders STAT3β able to maintain its DNA binding function, but not able to be fully active as a transcription factor.

Previously, it has been thought that STAT3β was a dominant-negative regulator based on its ability to bind DNA and thus competitively inhibit the activity of STAT3α. However, the findings of Zammarchi et al are questioning that designation, and have made a strong case for STAT3β as an antitumorigenic factor with its own specific set of regulated genes and proteins.

In a series of experiments that tested STAT3β regulation of both RNA and protein products, Zammarchi et al found that IL-8, LEGDF, and PCAF were all regulated specifically by STAT3β rather than total STAT3 knockdown. The transcription factor was demonstrated to downregulate both LEDGF and PCAF transcription and translation. IL-8 is involved in inflammation and in the chemotaxis of neutrophils, which are innate immune cells that phagocytose pathogens. LEDGF is a chromatin-binding protein and a transcriptional coactivator, as well as a pro-survival growth factor. PCAF is a histone acetyl transferase and transcriptional coactivator that promotes growth, invasion, and drug resistance. Clearly these genes are all of great interest to oncologists as potential cancer treatment targets, and thus STAT3β is coming into focus as a gene and protein of interest for all those involved in fighting cancer.

It has been previously demonstrated by Yue and Turkson1 that overexpression of STAT3β can induce apoptosis and inhibit tumor growth, and now the next step investigating the reasons for these effects has begun. Zammarchi et al showed that the STAT3β regulation occurs in several different types of cancer cell lines, including breast cancer, prostate cancer, and lung cancer, demonstrating the potential widespread nature of this factor as a cancer treatment target. There is still a long list of topics to be further investigated before STAT3β can be implicated as a prospective treatment target in humans including determining side effects, testing in animal models, and the development of drug delivery systems that are compatible with this substance, but nonetheless STAT3β appears to be a promising target for future oncological studies.

Reference:

Zammarchi, F. et al. (2011) Antitumorigenic potential of STAT3 alternative splicing modulation. PNAS 108(43):17779-84.

Additional Citation:

1) Yue, P., Turkson, J. (2009) Targeting STAT3 in cancer: How successful are we? Expert Opin Investig Drugs 18:45-56.

Treating γδT cells as Individuals May Help Develop New Cancer Treatments

γδ T cells are a subset of T cells that bridge innate and adaptive immunity. γδ T cells bind and recognize a broad range of foreign materials with their “γδ” receptors. These foreign entities can include proteins and lipids from pathogens as well as host stress molecules. This is the innate part of their function; it is fairly non-specific. They then generate either CTL-like (toxic) or Th-like (helper) responses against these pesky materials. This is the adaptive part of their function; it is more specific (1). Often, it is thought that all γδ T cells behave similarly, in the way that was just described.

A growing body of evidence, however, including a recent paper by Yin et. al. (2), suggests that different subsets of γδ T cells perform unique functions (3). In their work, Yin and coworkers found that one type of γδ T cell, Vg1 γδ T cells, inhibits the antitumor response of another type of γδ T cell, Vγ4 γδ T cells. (Vγ1 and Vγ4 refer to a particular gene segment that codes for part of the receptor chain; think of it as a receptor flavor).

In a previous study (4), Yin and coworkers found that Vγ4 γδ T cells killed tumors using INFγ (a signaling molecule that can: tell other cells to kill the tumor, prevent blood and nutrient flow to the tumor, and prevent spreading of the tumor by constructing a barrier around it (1)) and perforin (a molecule that kills a tumor by poking holes in it (1)). In this study, Yin et al. found that Vγ1 γδ T cells inhibit the anti-tumor response of Vγ4 γδ T by using signaling molecule IL-4.

Yin and co-workers placed Vγ1 γδ T cells , Vγ4 γδ T cells, and tumor cells in mice in different combinations and monitored tumor growth. Vγ4 γδ T cells alone suppressed the tumor. Addition of Vγ1 γδ T cells reduced this suppression. They obtained similar results when they performed the experiments in vitro (outside of mice, in culture).

When they separated the two types of cells by a membrane in vitro, they observed the same loss of tumor suppressor function. This suggests that the Vγ1 γδ T cells do not depend on direct cell-to-cell contact to inhibit Vγ4 γδ T cells and instead depend on a soluble mediator. This conclusion was further confirmed by a dye staining experiment that showed that the two types of cells localized to different parts of the tumor and were therefore unlikely to directly contact each other at all.

The soluble mediator molecule was determined to be IL-4. Suppressing IL-4 restored Vγ4 γδ T tumor suppression abilities. Furthermore, adding IL-4 alone, but not Vγ1 γδ T cells, to Vγ4 γδ T cells suppressed antitumor properties. The relationship between the two cell types came full circle when Yin and coworkers found that IL-4 down regulates NKG2D (Natural Killer Group 2 receptor, common to NK cells and γδ T cells), a receptor that tells Vγ4 γδ T cells to make IFNγ and perforin. IL-4 interferes with IFNγ and perforin. Thus, molecules made by Vγ1 γδ T cells interfere with molecules made by Vγ4 γδ T cells.

The study leaves some questions unanswered. For example, why do the different γδ T cell subsets localize to different parts of the tumor? How does IL-4 down regulate NKG2D receptors? More broadly, how do Vγ4 γδ T and Vγ1 γδ T cells interact with other cell types? But it also provides novel and potentially useful results. It suggests that Vγ1 γδ T is a regulatory T cell of sorts in that it dampens the response of another type of T cell, Vγ4 γδ T. The study also opens the door for a possible tumor therapy where Vγ1 γδ T cells are selectively killed or inactivated so that Vγ4 γδ T cells can be allowed to carryout out their tumor-killing mission.

Reference:

Yin, Z. et. al. 2011. Regulatory Role of Vγ1 γδ T cells in Tumor Immunity through IL-4 Production. J. Immunol. 187: 4979-4986.

Additional Citations:

(1) Mak, Tak and Mary Saunders. Primer to the Immune Response. California: Elsevier, 2011. Print.

(2) Yin, Z. et. al. 2011. Regulatory Role of Vγ1 γδ T cells in Tumor Immunity through IL-4 Production. J. Immunol. 187: 4979-4986.

(3) Born,W. K., Z. Yin, Y. S. Hahn, D. Sun, and R. L. O’Brien. 2010. Analysis of γδ T cell Functions in the Mouse. J. Immunol. 184: 4055–4061.

(4) He, W. , J. Hao, S. Dong, Y. Gao, J. Tao, H. Chi, R. Flavell, R. L. O’Brien, W. K. Born, J. Craft, et al. 2010. Naturally Activated Vγ4 γδ T cells Play a Protective Role in Tumor Immunity through Expression of Eomesodermin. J. Immunol. 185: 126–133.

Allergies Slowly Becoming More Understood

In this day in age, a majority of the population possesses some sort of allergy. Whether it be to penicillin, pollen, peanuts, eggs, or shellfish, the list goes on and on. Yet, what can be immediately noticed from this list of but a few allergens is that most are directed towards food. After all, food contains some of the most common "foreign entities" which enter our body, in the same ranks (kinda) as bacteria, viruses, and fungi. What's more is we let food in it willingly (why would we ever do such a crazy thing!). However, importantly, food does not often release immune danger signals into our body (unless it was those Mexican leftovers sitting in your fridge for one day too long).

A common form of allergy is immediate hypersenstivity, or type I hypersensitivity. This response to an allergen usually occurs relatively quickly (~ 30 mins) and can be very severe. Such a hypersensitivity (aka allergy) is mediated in two distinct steps. First is the sensitization stage where the allergen penetrates, most likely at a skin or mucosal interface, and is taken up by dendritic cells (DC), which are known for there extensive processes and ability to showcase a pathogen on their surface. Next, the DC activates a helper T cell and helps produce a polarized response, meaning the T cell develops into a Th2 subtype. A danger signal must be present in order for this type of activation to occur, but the whereabouts of such a signal is still under debate. Nevertheless, the Th2 cell, known for aiding in the humoral (antibody response) does its duty and activated B cells. These B cells ultimately undergo a process dubbed isotype switching where the type of antibody they produce is modified. This process leads to B cells producing large quantities of a type of antibody known as IgE, known for its role in allergies.
The next stage is the effector stage where if the allergen returns to the body it leads to an allergic response. The IgE antibodies can bind to the outer surface of certain leukocytes, such as mast cells, via Fc receptors and "arm" them. When the allergen returns then the mast cell is activated via the antibodies and degranulates, spewing toxic chemicals at the allergen and causing an immune response in the process.

In the recent work of Morin et al. (2011), the group examines the allergenicity of two proteins found in different fractions of cow milk, beta-lactoglobulin (BLG) and casein (CAS). Cow's milk allergy (CMA) is very common during early childhood and evokes a rapid response. However, CMA usually disappears , it remains in some (Sicherer et al. 2010). What is more dangerous about CMA is that it increases the child's susceptibility to other allergies (Saarinen et al. 2005). In this study, they examined the allergenic and immunogenic effects of these two proteins in two different strains of mice, one was germ-free (GF) and the other conventionally raised (CV). They attempted to complete this study in the absence of an adjuvant for the proteins. Adjuvants are commonly used to give the immune system a push, so to speak, helping to evoke an immune response to the injected compound. The downside of adjuvants in allergy studies is that they can evoke non-specific allergies to some of their own components, making it difficult to examine the specificity of a response. The GF mice have an immature immune system due to their lack of experience with many pathogens, so the authors hypothesized these mice would be more susceptible to an allergic response. Two sets of experiments were completed in each mouse, one measuring antibody type from blood samples and the other examining cytokine secretion from the isolated and reactivated spleens of the mice. Afterwards, they tried something novel and intraperitoneally administered a heated mix of the proteins, hoping to denature the proteins and open new epitopes for binding.

Solving the Puzzle of the Super Bug

Solving the Puzzle of the Super Bug

"We have applied the latest genome sequencing technology to show that Staph can readily become vancomycin (antibiotic) resistant by acquiring a single mutation in its DNA. When the bacteria mutate, they are reprogramming themselves, changing their cell walls to resist the action of our antibiotics"-Dr. Stinear.

 

                The treatment of mild to serious infections from Staphylococcus aureus (Golden Staph) is severely hindered by the development of antibiotic resistance. This antimicrobial resistance is a major public health threat which is further worsened by the development of strains of Staph bacteria with resistance to strong antibiotics such as vancomycin and daptomycin, which are considered last line antimicrobials. Patients in hospitals are more susceptible to staph infections because their immune systems are already compromised.  In hospitals around the world, infections with methicillin-resistant Staph aureus (MRSA) continue to cause a significant number of unnecessary deaths.  Therefore developing treatments to fight staph resistant strains as well as reduce the number of cases in hospitals is a major topic of study.  Recently research has added a new piece to the puzzle of elucidating the mechanism by which Staph evades the immune response to develop resistance to these last-line antibiotics.  

Frighteningly so, a small number of clones of staph account for the large number of hospital acquired infections.  In Australia, multi-locus sequence type (MLST) 239 termed ST239 comprises the major clone MRSA and has been infecting patients for over 30 years.  Unfortunately this clone is resistant to almost all antibiotic types therefore the current treatment for such an infection is the strong antibiotic vancomycin. Generally speaking, vancomycin is only prescribed after treatment with other antibiotics has failed; therefore it is administered as a last resort. However, recently strains have evolved to develop a low resistance to this antibiotic as well.  These strains partially resistant to vancomycin are named vancomycin-intermediate S. aureus (VISA).  The genetics of these strains that enable them to resist vancomycin antibiotics are the topic of a recently published study in the journal PLoS Pathogens titled Evolution of Multidrug Resistance during Staphylococcus aureus Infection Involves Mutation of the Essential Two Component Regulator WalkR.

LAG3 Gene and Early Onset of Type 1 Diabetes

The lymphocyte activation gene-3, LAG3, is a significant regulator of the immune system and recently has been concretely attributed to development in Type 1 Diabetes in diabetes prone mice. Type 1 Diabetes is an autoimmune disease in which cells of the body are mistaken as pathogens and destroyed by the immune system. In Type 1 Diabetes, the cells that are destroyed are the insulin-producing beta cells. This disease is generally characterized by insulitis and beta-cell autoantibodies (Van den Driessche et. al, 2009).

LAG3 may be responsible for the malfunctioning of the immune system and the onset of Type 1 Diabetes. LAG3 plays a large part in regulating T cells, which are critical to fighting infections and diseases. LAG3 both regulates the numbers of T cells in the body and is required for the proper functioning of T cells and Natural Killer cells (Workman et. al, 2009). Moreover, many critical cell types in the immune system express LAG3, including CD4⁺ and CD8⁺ T cells, natural killer cells, and plasmacytoid dendritic cells (Workman et. al, 2009). These cells each play important functions in detecting pathogens throughout the body and carrying out the removal of harmful entities.

Lag3 deletion in normal mice has been documented to have minor noticeable changes, with little to no effect on the prevalence of diabetes development (Miyazaki et. al, 1996). However, it has been recently demonstrated that in autoimmune-prone conditions, LAG3 plays a critical role in an early onset of Type 1 Diabetes (Bettini et. al, 2011).

Bettini et. al used non-obese diabetic mice, or NOD mice, to test the control of LAG3 on three important types of cells in the immune system: T cells, natural killer cells and plasmacytoid dendritic cells (2011). NOD mice were the subjects of choice, for they are often used as a mouse model of Type 1 Diabetes (Crawford et al., 2011). Bettini et. al bred NOD mice with a Lag3 mutation, rendering the gene non-functional. The mice were then tested for diabetes onset at various points of development by analysis of urine samples and blood glucose levels.

IRF-1 is Essential for Immunity Against West Nile Virus Infection in Mice

The West Nile Virus (WNV) is spread via mosquitoes and has been affecting humans in the United States since 1999 (1). Current research by immunologist further dissects antiviral immunity, in hopes of understanding WNV infectivity and how it can be combated or prevented. Previous research in mice has identified several immune mechanisms of control against WNV including cytokines, chemokines, complement, B CD4+ and CD8+ T cells (reviewed in [1]). These are all various aspects of the innate and adaptive immune system that aid in fighting against pathogens. More specifically, type 1 IFN (IFN-αβ) has been given special attention, as mice deficient in it, rapidly succumb to WNV infection (2). Further, it was determined that IFN induction is dependent on certain transcriptional signals. Past research pointed Brien et al. (2011) in the direction of IRF-1, as it has been reported to contribute to IFN-β induction. For example, it was found that IRF-1 transcription factor activated IFN-β gene transcription and regulated genes that directly impeded replication of several viruses. Further roles of IRF-1 have been found in controlling herpes virus, even though mice lacking IRF-1 did not have defects in their type I IFN response. This would suggest that IRF-1 regulates IFN genes “in a pathogen and cell type-dependent manner” (1). Further research has also identified IRF-1 as a tumor suppressing gene and a regulator of the adaptive immune response (3).
To understand the role of IRF-1, Brien et al. (2011) assessed WNF infectivity in IRF-1 normal and IRF-1 deficient mice (1). As previously mentioned, they chose to manipulate IRF-1 because mice lacking it (IRF-1-/- ) were vulnerable to WNV infection. First, it was confirmed that IRF-1 is required for control of lethal WNV infection. After infection with WNV, Wild-type (WT) mice had a 65% survival rate and a mean time to death of 11 days, whereas IRF-1-/- mice had a 0% survival rate and a mean time to death of 9.5 days.
To better understand how IRF-1 deficiency is a disadvantage for mice with WNV infection, the ‘viral burden’ was measured at various points post infection in serum, several peripheral organs, and the central nervous system (CNS). Indeed, increased levels of viral RNA were found in the serum and lymph nodes in IRF-1-/- mice compared to the WT. Therefore, IRF-1 controls the early stages of WNV infection. Additionally, WNV infected the spleen more rapidly and clearance was delayed in IRF-1-/- mice. WNV was also detected sooner in the kidneys of IRF-1-/- mice, further suggesting that IRF-1 normally functions to control infection in peripheral tissues.