Among many global health challenges, infectious diseases remain among the most problematic, accounting for about one quarter of all deaths globally, and nearly two-thirds of deaths in sub-Saharan Africa. Dr. Fauci will discuss progress–and remaining challenges–in the fight against major infectious causes of death and disability such as HIV/AIDS, malaria, tuberculosis and drug-resistant microbes. He also will discuss how conceptual and technological progress in fields such as genomics and nanotechnology has invigorated infectious disease research. These advances also are contributing to exciting studies on the ecology of human disease, including the Human Microbiome Project, which is exploring how the billions of bacteria that inhabit our bodies contribute to health and illness.

Other NIAID scientists are scheduled to present findings during the four-day meeting as well. The range of topics covered reflects the broad scope of NIAID’s research efforts aimed at better understanding, treating and preventing infectious and immune-mediated diseases.

• Noroviruses, the highly contagious viruses that cause the episodes of acute gastroenteritis also known as winter vomiting disease (Kim Green, Ph.D.)
• The role of gut-dwelling commensal bacteria in producing the symptoms of Crohn’s disease, a chronic inflammatory disease of the intestines (Warren Strober, M.D.)
• Antibiotic-resistant bacterial infections caused by Staphylococcus epidermidis (Michael Otto, Ph.D.) and Staphylococcus aureus (Frank DeLeo, Ph.D.)
• Finding ways to treat primary immunodeficiencies, inherited conditions in which immune function is impaired (Steve Holland, M.D.)
• Containing Ebola virus, for which there is currently no vaccine or specific treatment (Gary Nabel, M.D., Ph.D.)

Flaviviruses such as tick-borne encephalitis virus (TBEV), yellow fever, and dengue are dangerous human pathogens.  These membrane-encircled viruses enter cells by being gobbled up into endosomes and fusing their membrane with that of the endosome.

Fusion is triggered by the endosome’s acidic environment.  Low pH prompts the aptly named fusion protein, on the virus’s outer membrane, to change shape and grab hold of the endosome membrane, bringing the two membranes together.  In their search for possible pH sensors, researchers have focused on five highly conserved histidine residues in the flavivirus fusion protein.  The chemical properties of histidines make them prime candidates—they switch from uncharged to having a double positive charge upon acidification of their environment, such as that in endosomes.

Fritz et al.  Replaced each of the five histidines of the TBEV fusion protein with alternative residues and observed the virus’s fusion ability.  Given the conservation of the five histidines, the team was surprised, that mutation of one of the histidines, His323, was sufficient to completely abolish fusion.  Individual mutation of three of the others had no effect on fusion whatsoever, and mutation of the fourth led to an untestable ill-formed fusion protein.

The team went on to show that mutation of the crucial His323 interfered with the pH-induced shape change of the fusion protein.

Researchers at the University of Toronto have shown that the EBNA1 protein of Epstein-Barr virus (EBV) disrupts structures in the nucleus of nasopharyngeal carcinoma (NPC) cells, thereby interfering with cellular processes that normally prevent cancer development.  The study, published October 3rd in the open-access journal PloS Pathogens, describes a novel mechanism by which viral proteins contribute to carcinogenesis.

EBV is a common herpesvirus whose latent infection is strongly associated with several types of cancer including NPC, a tumor that is endemic in several parts of the world.  With NPC only a few EBV proteins are expressed, including EBNA1.  EBNA1 is required for the persistence of the EBV genomes, however, whether or not EBNA1 directly contributes to the development of tumors has not been clear, until now.

In this study Frappier and her team examined PML nuclear bodies and proteins in EBV-positive and EBV-negative NPC cells.  Manipulation of EBNA1 levels in each cell type clearly showed that EBNA1 expression induces the loss of PML proteins and PML nuclear bodies through an association of EBNA1 with the PML bodies.  PML nuclear bodies are known to have tumor-suppressive effects due to their roles in regulating DNA repair and programmed cell death, and accordingly, EBNA1 was shown to interfere with these processes.

The researchers conclude that there is “an important role for EBNA1 in the development of NPC, in which EBNA1-mediated disruption of PML nuclear bodies promotes the survival of cells with DNA damage.”  Since EBNA1 is expressed in all EBV-associated tumors, including B-cell lymphomas and gastric carcinoma, these findings raise the possibility that EBNA1 could play a similar role in the development of these cancers.  The cellular effects of EBNA1 in other EBV-induced cancers will require further investigation.

A study published July 11th in the open-access journal PloS Pathogens suggests that herpesviruses use multiple strategies to manipulate important components of the host cell nuclear environment during infection.  The study, conducted by researchers at the University of Toronto in collaboration with Affinium Pharmaceuticals Inc., provides novel insights into the potential functions of over 120 previously uncharacterized viral proteins.

Most people are infected with the three human herpesviruses that were the subject of this study; namely herpes simplex virus (type 1), Epstein-Barr virus, and cytomegalovirus.  Herpesviruses have complex life cycles due to their adept manipulation of the host cell environment.  Although often asymptomatic, herpesviruses can cause life-threatening diseases.  In order to provide a more complete understanding of how these viruses alter host cells, the researchers developed a system to examine each viral protein individually in human cells.

The researchers investigated over 230 individual proteins from the three herpesviruses.  They focused on 93 identified viral proteins that localized to the cell nucleus and altered key cellular components that regulate gene expression, cell growth and death, and antiviral responses.

Cells depend on nuclear structures called PML bodies to control cell proliferation and survival, to ensure damaged DNA is repaired, and to inhibit virus replication.  24 of the nuclear viral proteins, several of which had no previously assigned function, were found to disrupt or reorganize PML bodies, suggesting that herpesviruses employ multiple strategies for manipulating this key regulator of essential cellular processes.

Further studies will be needed to determine how the identified viral proteins function in the context of viral infection, but this research provides a starting point for investigating how these proteins affect important processes of the cell nucleus.

Individuals inhale measles virus particles in aerosols and it is currently thought that these particles infect the cells that line the airways (respiratory epithelial cells) before being passed to immune cells that carry the virus particles to other parts of the body and then back to the airways, which again become infected and shed virus into exhaled aerosols.  In the study, a measles virus unable to bind to and infect epithelial cells was found to cause symptoms of measles virus infection in monkeys even though it did not infect respiratory epithelial cells and was not being shed into exhaled aerosols.  These data suggest that, in fact, inhaled measles virus particles first infect lymphocytes and are only passed to respiratory epithelial cells from the lymphocytes in the tissues.  Further, they indicate that the protein that measles virus particles bind to on respiratory epithelial cells, which has yet to be identified, is likely to be found on the surface of the cells that faces the tissues rather than the surface that faces the airways, as previously assumed.  As discussed in an accompanying commentary by Makoto Takeda, at Kyushu University, Japan, the results of this study should help researchers identify this protein.

Coronaviruses, a group including the well-known SARS virus, are the causative agents of many respiratory and enteric infections in humans and animals. As with all viruses, virtually every step of their infection cycle depends on host cellular factors. As the first, most crucial step after their penetration into cells, coronaviruses assemble huge RNA replication “factory” complexes in association with characteristic, newly induced double membrane vesicles. The cellular pathways hijacked by these plus-strand RNA viruses to create these “factories” have thus far not been elucidated.

The researchers, led by Cornelis A. M. de Haan, showed that RNA replication of mouse hepatitis coronavirus (MHV) was inhibited by a drug — brefeldin A — that disrupts the central station in the cell’s secretory pathway, the Golgi complex. Consistently, depletion of both the cellular target of brefeldin A, a factor called GBF1, and its downstream target, ARF1, was also shown to negatively affect coronavirus infection.

The researchers conclude that “an intimate association exists between the early secretory pathway and MHV replication.” They speculate that, while GBF1 and ARF1 are not involved in the formation of the viral replication structures, they probably play a key role in their maturation or functioning. As this work was limited to the mouse hepatitis coronavirus, an interesting next step would be to study the importance of GBF1 and ARF1 in the replication of other coronaviruses.

Soon after an individual becomes infected with HIV the virus infects cells in the brain and spinal cord (the central nervous system [CNS]).  Although this causes no immediate problems, during the late-stages of disease it can cause dementia and encephalitis (acute inflammation of the brain that can cause death).  Monkeys infected with a relative of HIV (SIV) also sometimes develop CNS damage and provide a good model of CNS disease in individuals infected with HIV.  Insight into the mechanisms of CNS damage in SIV-infected monkeys has now been provided by a team of researchers at The Scripps Research Institute, La Jolla, who developed an approach to identify molecular changes in the fluid bathing the CNS (the CSF).  The researchers, who were led by Howard Fox and Gary Siuzdak, hope that similar approaches could be used to provide new information about other neurodegenerative and neuropsychiatric disorders.

In the study, an approach known as global metabolomics was used to assess the levels of molecules known as metabolites in the CSF before and after SIV-induced encephalitis was manifest.  The level of a number of metabolites, including some known as fatty acids and phospholipids, was observed to increase during infection.  Consistent with this, a protein known to be important in the generation of fatty acids was found to be increased in the brain of monkeys with SIV-induced encephalitis.  Further studies will be required to determine the precise role of the increased level of each metabolite, but it should be noted that many of them are known to induce receptor signaling and thereby might be able to further modulate CNS function.

A study from researchers at Children’s Hospital Boston published in Pediatrics found that a simple infection control intervention in elementary schools – disinfecting frequently-touched surfaces and using alcohol-based hand sanitizers – helped reduce illness-related student absenteeism.Illnesses caused by bacteria and viruses account for millions of lost school days each year.(1) According to Thomas Sandora, MD, MPH, a pediatric infectious diseases specialist at Children’s Hospital Boston, “The best ways to avoid common infections are cleaning your hands and preventing exposure to the germs that cause these illnesses. Our research indicates that elementary schools should consider a few simple infection control practices to help keep students healthier.”

The study, led by Dr. Sandora, was a randomized, controlled trial involving 285 third-, fourth-, and fifth-grade students in an elementary school system in Avon, Ohio. Teachers in intervention classrooms used disinfecting wipes on student desks, and students used hand sanitizer in the classroom at key points throughout the school day. Control classrooms followed usual hand washing and cleaning procedures.

Over eight weeks, researchers tracked the frequency of absences and the reasons for missing school. Study investigators also tested several classroom surfaces for total bacterial counts and for the presence of several common viruses.

Researchers found absenteeism rates for gastrointestinal illnesses were nine percent lower in classrooms that followed the infection control regimen of disinfecting surfaces and using alcohol-based hand sanitizers. The absenteeism rate for respiratory illness was not affected by this intervention.

Gastrointestinal illnesses are extremely common for school-age children, and children can be at risk for these infections because of frequent exposure to ill peers and poor hand hygiene.(1) In fact, the bacteria and viruses that cause these gastrointestinal infections can be easily passed from one person to another on the hands.(2) The germs can also survive on surfaces in the environment, where some of them can persist for hours to days.(1)

The study suggests that schools should consider adopting simple infection control practices, including disinfecting desktops once a day and using hand sanitizer before and after lunch, to help reduce days lost to common illnesses.

Viruses are true experts at importing genetic material into the cells of an infected organism. This trait is now being exploited for gene therapy, in which genes are brought into the cells of a patient to treat genetic diseases or genetic defects. Korean researchers have now made an artificial virus. As described in the journal Angewandte Chemie, they have been able to use it to transport both genes and drugs into the interior of cancer cells.

Natural viruses are extremely effective at transporting genes into cells for gene therapy; their disadvantage is that they can initiate an immune response or cause cancer. Artificial viruses do not have these side effects, but are not especially effective because their size and shape are very difficult to control—but crucial to their effectiveness. A research team headed by Myongsoo Lee has now developed a new strategy that allows the artificial viruses to maintain a defined form and size.

The researchers started with a ribbonlike protein structure (β-sheet) as their template. The protein ribbons organized themselves into a defined threadlike double layer that sets the shape and size. Coupled to the outside are “protein arms” that bind short RNA helices and embed them. If this RNA is made complementary to a specific gene sequence, it can very specifically block the reading of this gene. Known as small interfering RNAs (siRNA), these sequences represent a promising approach to gene therapy.

Glucose building blocks on the surfaces of the artificial viruses should improve binding of the artificial virus to the glucose transporters on the surfaces of the target cells. These transporters are present in nearly all mammalian cells. Tumor cells have an especially large number of these transporters.

Trials with a line of human cancer cells demonstrated that the artificial viruses very effectively transport an siRNA and block the target gene.

In addition, the researchers were able to attach hydrophobic (water repellant) molecules—for demonstration purposes a dye—to the artificial viruses. The dye was transported into the nuclei of tumor cells. This result is particularly interesting because the nucleus is the target for many important antitumor agents.