sabato 28 giugno 2014

Polio will go, acute flaccid paralysis will stay

The Global Polio Eradication Initiative has made tremendous progress since its launch by WHO in 1988, reducing polio cases from an estimated 350 000 in 1988 to about 407 in 2013. The number of countries that have never interrupted wild poliovirus transmission decreased from more than 125 to only three countries (Nigeria, Afghanistan, and Pakistan). In 1999, the eradication of wild poliovirus type 2 was achieved. The last case of poliovirus type 3 occurred on Nov 10, 2012, in Nigeria. The remaining goal of the Global Polio Eradication Initiative is to stop the transmission of all wild poliovirus and vaccine-derived poliovirus through supplementary immunisation activities, and environmental and acute flaccid paralysis surveillance (read more)

West Nile virus nucleic acid persistence in whole blood months after clearance in plasma: implication for transfusion and transplantation safety

Background : Previous reports of West Nile virus (WNV) RNA persistence in blood compartments have raised concerns around the remaining risk of WNV transfusion transmission. This study characterized the dynamics of WNV viremia in blood compartments in a longitudinal cohort of 54 WNV-infected blood donors.
Study Design and Methods : Blood samples were collected throughout the year after WNV RNA–positive blood donation (index) and characterized for WNV immunoglobulin (Ig)M and IgG antibodies and for WNV RNA by real-time reverse transcription–polymerase chain reaction. WNV viral loads were compared in plasma and whole blood samples and correlated with blood groups and clinical outcomes.
Results : WNV RNA persisted in the red blood cell (RBC) compartment up to 3 months postindex in 42% of the donors. Donors with the highest WNV RNA levels in plasma at index maintained the highest WNV RNA levels in whole blood over the 3 months postindex. Blood group A donors maintained higher postindex WNV viral load in whole blood than blood group O individuals (p = 0.027). Despite a trend for WNV RNA to persist longer in whole blood from symptomatic subjects, no significant association was found between WNV RNA levels in whole blood and disease outcome.
Conclusion : This study confirmed that WNV RNA persists in the RBC fraction in whole blood and further suggested that the level of persistence in whole blood may be a reflection of initial viral burden in plasma. The association with blood groups suggests that WNV adherence to RBCs may be mediated by molecules overrepresented at the surface of blood group A RBCs (read more).

lunedì 23 giugno 2014

Team science and the creation of a novel rotavirus vaccine in India: a new framework for vaccine development

In The Lancet, findings from Nita Bhandari and colleagues' phase 3 clinical trial show the safety and efficacy of the 116E rotavirus vaccine against severe rotavirus gastroenteritis in Indian infants. The vaccine has an efficacy similar to that of two licensed oral rotavirus vaccines—RotaTeq (Merck) and Rotarix (GlaxoSmithKline)—when tested in low-income settings. However, the timeline of development has been unique and unconventional. The vaccine was not the product of a major multinational manufacturer, but rather, the result of work by team science, based in India (read more)

sabato 21 giugno 2014

Preclinical Detection of Variant CJD and BSE Prions in Blood

The emergence of variant Creutzfeldt Jakob Disease (vCJD) is considered a likely consequence of human dietary exposure to Bovine Spongiform Encephalopathy (BSE) agent. More recently, secondary vCJD cases were identified in patients transfused with blood products prepared from apparently healthy donors who later went on to develop the disease. As there is no validated assay for detection of vCJD/BSE infected individuals the prevalence of the disease in the population remains uncertain. In that context, the risk of vCJD blood borne transmission is considered as a serious concern by health authorities. In this study, appropriate conditions and substrates for highly efficient and specific in vitro amplification of vCJD/BSE agent using Protein Misfolding Cyclic Amplification (PMCA) were first identified. This showed that whatever the origin (species) of the vCJD/BSE agent, the ovine Q171 PrP substrates provided the best amplification performances. These results indicate that the homology of PrP amino-acid sequence between the seed and the substrate is not the crucial determinant of the vCJD agent propagation in vitro. The ability of this method to detect endogenous vCJD/BSE agent in the blood was then defined. In both sheep and primate models of the disease, the assay enabled the identification of infected individuals in the early preclinical stage of the incubation period. Finally, sample panels that included buffy coat from vCJD affected patients and healthy controls were tested blind. The assay identified three out of the four tested vCJD affected patients and no false positive was observed in 141 healthy controls. The negative results observed in one of the tested vCJD cases concurs with results reported by others using a different vCJD agent blood detection assay and raises the question of the potential absence of prionemia in certain patients (read more)

Replication of Many Human Viruses Is Refractory to Inhibition by Endogenous Cellular MicroRNAs

The issue of whether viruses are subject to restriction by endogenous microRNAs (miRNAs) and/or by virus-induced small interfering RNAs (siRNAs) in infected human somatic cells has been controversial. Here, we address this question in two ways. First, using deep sequencing, we demonstrate that infection of human cells by the RNA virus dengue virus (DENV) or West Nile virus (WNV) does not result in the production of any virus-derived siRNAs or viral miRNAs. Second, to more globally assess the potential of small regulatory RNAs to inhibit virus replication, we used gene editing to derive human cell lines that lack a functional Dicer enzyme and that therefore are unable to produce miRNAs or siRNAs. Infection of these cells with a wide range of viruses, including DENV, WNV, yellow fever virus, Sindbis virus, Venezuelan equine encephalitis virus, measles virus, influenza A virus, reovirus, vesicular stomatitis virus, human immunodeficiency virus type 1, or herpes simplex virus 1 (HSV-1), failed to reveal any enhancement in the replication of any of these viruses, although HSV-1, which encodes at least eight Dicer-dependent viral miRNAs, did replicate somewhat more slowly in the absence of Dicer. We conclude that most, and perhaps all, human viruses have evolved to be resistant to inhibition by endogenous human miRNAs during productive replication and that dependence on a cellular miRNA, as seen with hepatitis C virus, is rare. How viruses have evolved to avoid inhibition by endogenous cellular miRNAs, which are generally highly conserved during metazoan evolution, remains to be determined.
IMPORTANCE Eukaryotic cells express a wide range of small regulatory RNAs, including miRNAs, that have the potential to inhibit the expression of mRNAs that show sequence complementarity. Indeed, previous work has suggested that endogenous miRNAs have the potential to inhibit viral gene expression and replication. Here, we demonstrate that the replication of a wide range of pathogenic viruses is not enhanced in human cells engineered to be unable to produce miRNAs, indicating that viruses have evolved to be resistant to inhibition by miRNAs. This result is important, as it implies that manipulation of miRNA levels is not likely to prove useful in inhibiting virus replication. It also focuses attention on the question of how viruses have evolved to resist inhibition by miRNAs and whether virus mutants that have lost this resistance might prove useful, for example, in the development of attenuated virus vaccines (read more)

martedì 3 giugno 2014

The Human Fetal Glial Cell Line SVG p12 Contains Infectious BK Polyomavirus

The human fetal glial cell line SVG was generated in 1985 by transfecting primary fetal brain cells with a plasmid containing an origin-defective mutant of simian virus 40 (SV40). The cells, which express SV40 large T-antigen, support the replication of human JC polyomavirus (JCPyV) and have been used for JCPyV studies but also for other studies in which cells of neural origin were desirable. We intended to use the SVG p12 cells from ATCC for antiviral drug studies with JCPyV. However, during initial experiments, immunofluorescence microscopy controls unexpectedly revealed cells expressing the late viral proteins VP1, VP2/VP3, and agno. This was confirmed by Western blotting. Since our agnoprotein antiserum is specific for BKPyV agnoprotein, infection with BKPyV was suspected. Indeed, specific BKPyV PCR of SVG p12 supernatants revealed a viral load of >1 × 1010 genomic equivalents/ml. Negative-staining electron microscopy showed characteristic polyomavirus virions, and infectious BKPyV was transmitted from SVG p12 supernatant to other cells. Long-range PCR covering the viral genome, followed by DNA sequencing, identified BKPyV strain UT as well as deletion derivatives. This was confirmed by next-generation sequencing. JCPyV (MAD-4) was found to infect apparently uninfected and BKPyV-infected SVG p12 cells. In total, 4 vials from 2 different ATCC lots of SVG p12 cells dating back to 2006 contained BKPyV, whereas the subclone SVG-A was negative. In conclusion, SVG p12 cells from ATCC contain infectious BKPyV. This may have affected results and interpretations of previous studies, and caution should be taken in future experiments (read more)

Polio eradication: the CIA and their unintended victims

On May 2, 2011, President Barack Obama announced that the US Central Intelligence Agency (CIA) had located and killed Osama Bin Laden. The agency organised a fake hepatitis vaccination campaign in Abottabad, Pakistan, in a bid to obtain DNA from the children of Bin Laden, to confirm the presence of the family in a compound and sanction the rollout of a risky and extensive operation. Release of this information has had a disastrous effect on worldwide eradication of infectious diseases, especially polio.
On May 16, 2014, the White House announced that the CIA will no longer use vaccination programmes as a cover for espionage. The news comes in the wake of a series of militant attacks on polio vaccination workers in Pakistan, with legitimate health-care workers targeted as being US spies. The attacks have forced organisations such as the UN to suspend polio vaccination efforts in Pakistan, and have severely hampered anti-polio efforts, with parents refusing to have their children vaccinated. News of the vaccination programme led to a banning of vaccination in areas controlled by the Pakistan Taliban, and added to existing scepticism surrounding the sincerity of public health efforts by the international health community.
Consequently, WHO declared that polio has re-emerged as a public health emergency in Pakistan—one of only three countries, including Afghanistan and Nigeria, where the disease remains endemic. According to the Global Polio Eradication Initiative, 61 of 77 cases of polio reported this year have been in Pakistan, and cases of paralytic polio have spiked, with 66 cases reported up to now, compared with only 14 last year.
The lesson learned from the experience in Pakistan is that public health programmes should be politically neutral. Although the announcement from the White House might go some way to building bridges towards that neutrality, health officials and local leaders now have the challenge of convincing communities that vaccination is not merely beneficial, but vital for children (read more)

[Review] Infectious causes of stroke

Most infectious pathogens have anecdotal evidence to support a link with stroke, but certain pathogens have more robust associations, in which causation is probable. Few dedicated prospective studies of stroke in the setting of infection have been done. The use of head imaging, a clinical standard of diagnostic care, to confirm stroke and stroke type is not universal. Data for stroke are scarce in locations where infections are probably most common, making it difficult to reach conclusions on how populations differ in terms of risk of infectious stroke (read more)