Pathogenicity and transmissibility of North American triple reassortant swine influenza A viruses in ferrets

North American triple reassortant swine (TRS) influenza A viruses have caused sporadic human infections since 2005, but human-to-human transmission has not been documented. These viruses have six gene segments (PB2, PB1, PA, HA, NP, and NS) closely related to those of the 2009 H1N1 pandemic viruses. Therefore, understanding of these viruses' pathogenicity and transmissibility may help to identify determinants of virulence of the 2009 H1N1 pandemic viruses and to elucidate potential human health threats posed by the TRS viruses. Here we evaluated in a ferret model the pathogenicity and transmissibility of three groups of North American TRS viruses containing swine-like and/or human-like HA and NA gene segments. The study was designed only to detect informative and significant patterns in the transmissibility and pathogenicity of these three groups of viruses. We observed that irrespective of their HA and NA lineages, the TRS viruses were moderately pathogenic in ferrets and grew efficiently in both the upper and lower respiratory tracts. All North American TRS viruses studied were transmitted between ferrets via direct contact. However, their transmissibility by respiratory droplets was related to their HA and NA lineages: TRS viruses with human-like HA and NA were transmitted most efficiently, those with swine-like HA and NA were transmitted minimally or not transmitted, and those with swine-like HA and human-like NA (N2) showed intermediate transmissibility. We conclude that the lineages of HA and NA may play a crucial role in the respiratory droplet transmissibility of these viruses. These findings have important implications for pandemic planning and warrant confirmation.

Live bird markets of Bangladesh: H9N2 viruses and the near absence of highly pathogenic H5N1 influenza

Avian influenza surveillance in Bangladesh has been passive, relying on poultry farmers to report suspected outbreaks of highly pathogenic H5N1 influenza. Here, the results of an active surveillance effort focusing on the live-bird markets are presented. Prevalence of influenza infection in the birds of the live bird markets is 23.0%, which is similar to that in poultry markets in other countries. Nearly all of the isolates (94%) were of the non-pathogenic H9N2 subtype, but viruses of the H1N2, H1N3, H3N6, H4N2, H5N1, and H10N7 subtypes were also observed. The highly pathogenic H5N1-subtype virus was observed at extremely low prevalence in the surveillance samples (0.08%), and we suggest that the current risk of infection for humans in the retail poultry markets in Bangladesh is negligible. However, the high prevalence of the H9 subtype and its potential for interaction with the highly pathogenic H5N1-subtype, i.e., reassortment and attenuation of host morbidity, highlight the importance of active surveillance of the poultry markets.

Oseltamivir-resistant pandemic H1N1/2009 influenza virus possesses lower transmissibility and fitness in ferrets

The neuraminidase (NA) inhibitor oseltamivir offers an important immediate option for the control of influenza, and its clinical use has increased substantially during the recent H1N1 pandemic. In view of the high prevalence of oseltamivir-resistant seasonal H1N1 influenza viruses in 2007–2008, there is an urgent need to characterize the transmissibility and fitness of oseltamivir-resistant H1N1/2009 viruses, although resistant variants have been isolated at a low rate. Here we studied the transmissibility of a closely matched pair of pandemic H1N1/2009 clinical isolates, one oseltamivir-sensitive and one resistant, in the ferret model. The resistant H275Y mutant was derived from a patient on oseltamivir prophylaxis and was the first oseltamivir-resistant isolate of the pandemic virus. Full genome sequencing revealed that the pair of viruses differed only at NA amino acid position 275. We found that the oseltamivir-resistant H1N1/2009 virus was not transmitted efficiently in ferrets via respiratory droplets (0/2), while it retained efficient transmission via direct contact (2/2). The sensitive H1N1/2009 virus was efficiently transmitted via both routes (2/2 and 1/2, respectively). The wild-type H1N1/2009 and the resistant mutant appeared to cause a similar disease course in ferrets without apparent attenuation of clinical signs. We compared viral fitness within the host by co-infecting a ferret with oseltamivir-sensitive and -resistant H1N1/2009 viruses and found that the resistant virus showed less growth capability (fitness). The NA of the resistant virus showed reduced substrate-binding affinity and catalytic activity in vitro and delayed initial growth in MDCK and MDCK-SIAT1 cells. These findings may in part explain its less efficient transmission. The fact that the oseltamivir-resistant H1N1/2009 virus retained efficient transmission through direct contact underlines the necessity of continuous monitoring of drug resistance and characterization of possible evolving viral proteins during the pandemic.

Most of the currently circulating pandemic H1N1/2009 (“swine”) influenza viruses are susceptible to the anti-influenza drug oseltamivir. Many countries have stockpiled oseltamivir for pandemic preparedness, and to date only a small proportion of the H1N1/2009 viruses isolated have been oseltamivir-resistant. However, if these viruses can be readily transmitted, oseltamivir resistance may spread. We evaluated the transmissibility of a pair of pandemic H1N1/2009 influenza viruses in ferrets. One virus was oseltamivir-sensitive and the other carried the oseltamivir resistance-associated H275Y NA mutation. We also investigated the viruses' susceptibility to NA inhibitors (the drug class to which oseltamivir belongs), their NA enzyme kinetics, and their replication efficiency in cultured cells. Under identical conditions, the resistant H1N1/2009 virus was not transmitted by respiratory droplets but was efficiently transmitted by direct contact, while the sensitive H1N1/2009 virus was efficiently transmitted by both routes.

Emergence of H5N1 avian influenza viruses with reduced sensitivity to neuraminidase inhibitors and novel reassortants in Lao People's Democratic Republic

Pandemic influenza viruses can emerge through continuous evolution and the acquisition of specific mutations or through reassortment. This study assessed the pandemic potential of H5N1 viruses isolated from poultry outbreaks occurring from July 2006 to September 2008 in the Lao People's Democratic Republic (PDR). We analyzed 29 viruses isolated from chickens and ducks and two from fatal human cases in 2007. Prior to 2008, all H5N1 isolates in Lao PDR were from clade 2.3.4; however, clade 2.3.2 was introduced in September 2008. Of greatest concern was the circulation of three isolates that showed reduced sensitivity to the neuraminidase (NA) inhibitor oseltamivir in an enzyme inhibition assay, each with different NA mutations - V116A, I222L and K150N, and a previously unreported S246N mutation. In addition, six isolates had an S31N mutation in the M2 protein, which conferred resistance to amantadine not previously reported in clade 2.3.4 viruses. Two H5N1 reassortants were isolated whose polymerase genes, PB1 and PB2, were homologous to those of Eurasian viruses giving rise to a novel H5N1 genotype, genotype P. All H5N1 viruses retained avian-like receptor specificity, but four had altered affinities for alpha2,3-linked sialic acid. This study shows that, in a genetically similar population of H5N1 viruses in Lao PDR, mutants emerged with natural resistance to antivirals and altered affinities for alpha2,3-linked sialic acids, together with reassortants with polymerase genes homologous to Eurasian viruses. These changes may contribute to the emergence of a pandemic influenza strain and are critical in devising surveillance strategies.

Zoonotic potential of highly pathogenic avian H7N3 influenza viruses from Pakistan

H5 and H7 avian influenza viruses can become highly pathogenic in chickens after interspecies transmission. These viruses have transmitted directly to humans from birds in Eurasia and Africa (H5N1), the Netherlands (H7N7), and Canada (H7N3). Here we report antigenic, sequence, and phylogenetic analyses of H7N3 viruses isolated from chickens in Pakistan from 1995 to 2002. We compared the pathogenic and zoonotic potential of the Pakistani viruses in avian and mammalian hosts. In chickens, all of the isolates showed high pathogenicity with poor transmissibility to contact birds. Viral shedding from the trachea and cloaca was equivalent, but cloacal shedding occurred longer; dissemination of virus into the tissues was widespread. In contrast, the viruses replicated poorly in 6-week-old mallard ducks. In mammalian hosts, of the two Pakistani H7N3/02 viruses that caused weight loss, one also caused 40% mortality in mice without prior adaptation, and preliminary experiments in ferrets showed significant virus multiplication in the lungs, intestine, and conjunctiva. We conclude that the H7N3/02 isolates from Pakistan show limited antigenic drift and have evolved slowly during their 8-year circulation in chickens; however, these viruses have the potential to infect mammals.

Role of terrestrial wild birds in ecology of influenza A virus (H5N1)

Recent viruses are pathogenic for some small terrestrial bird species.

House sparrows, European starlings, and Carneux pigeons were inoculated with 4 influenza A (H5N1) viruses isolated from different avian species. We monitored viral replication, death after infection, and transmission to uninfected contact birds of the same species. Sparrows were susceptible to severe infection; 66%–100% of birds died within 4–7 days. High levels of virus were detected from oropharyngeal and cloacal swabs and in organs of deceased sparrows. Inoculation of starlings caused no deaths, despite high levels of virus shedding evident in oropharyngeal swabs. Least susceptible were pigeons, which had no deaths and very low levels of virus in oropharyngeal and cloacal swabs. Transmission to contact birds did not occur frequently: only A/common magpie/Hong Kong/645/2006 virus was shown to transmit to 1 starling. In summary, recent influenza (H5N1) viruses are pathogenic for small terrestrial bird species but the rate of intraspecies transmission in these hosts is very low.

The immunogenicity and efficacy against H5N1 challenge of reverse genetics-derived H5N3 influenza vaccine in ducks and chickens

H5N1 avian influenza viruses are continuing to spread in waterfowl in Eurasia and to threaten the health of avian and mammalian species. The possibility that highly pathogenic (HP) H5N1 avian influenza is now endemic in both domestic and migratory birds in Eurasia makes it unlikely that culling alone will control H5N1 influenza. Because ducks are not uniformly killed by HP H5N1 viruses, they are considered a major contributor to virus spread. Here, we describe a reverse genetics-derived high-growth H5N3 strain containing the modified H5 of A/chicken/Vietnam/C58/04, the N3 of A/duck/Germany/1215/73, and the internal genes of A/PR/8/34. One or two doses of inactivated oil emulsion vaccine containing 0.015 to 1.2 microg of HA protein provide highly efficacious protection against lethal H5N1 challenge in ducks; only the two dose regimen has so far been tested in chickens with high protective efficacy.

Are ducks contributing to the endemicity of highly pathogenic H5N1 influenza virus in Asia?

Wild waterfowl are the natural reservoir of all influenza A viruses, and these viruses are usually nonpathogenic in these birds. However, since late 2002, H5N1 outbreaks in Asia have resulted in mortality among waterfowl in recreational parks, domestic flocks, and wild migratory birds. The evolutionary stasis between influenza virus and its natural host may have been disrupted, prompting us to ask whether waterfowl are resistant to H5N1 influenza virus disease and whether they can still act as a reservoir for these viruses. To better understand the biology of H5N1 viruses in ducks and attempt to answer this question, we inoculated juvenile mallards with 23 different H5N1 influenza viruses isolated in Asia between 2003 and 2004. All virus isolates replicated efficiently in inoculated ducks, and 22 were transmitted to susceptible contacts. Viruses replicated to higher levels in the trachea than in the cloaca of both inoculated and contact birds, suggesting that the digestive tract is not the main site of H5N1 influenza virus replication in ducks and that the fecal-oral route may no longer be the main transmission path. The virus isolates' pathogenicities varied from completely nonpathogenic to highly lethal and were positively correlated with tracheal virus titers. Nevertheless, the eight virus isolates that were nonpathogenic in ducks replicated and transmitted efficiently to naïve contacts, suggesting that highly pathogenic H5N1 viruses causing minimal signs of disease in ducks can propagate silently and efficiently among domestic and wild ducks in Asia and that they represent a serious threat to human and veterinary public health.

Role of domestic ducks in the propagation and biological evolution of highly pathogenic H5N1 influenza viruses in Asia

Wild waterfowl, including ducks, are natural hosts of influenza A viruses. These viruses rarely caused disease in ducks until 2002, when some H5N1 strains became highly pathogenic. Here we show that these H5N1 viruses are reverting to nonpathogenicity in ducks. Ducks experimentally infected with viruses isolated between 2003 and 2004 shed virus for an extended time (up to 17 days), during which variant viruses with low pathogenicity were selected. These results suggest that the duck has become the "Trojan horse" of Asian H5N1 influenza viruses. The ducks that are unaffected by infection with these viruses continue to circulate these viruses, presenting a pandemic threat.

Decontamination with vaporized hydrogen peroxide is effective against Mycobacterium tuberculosis

AIMS

To determine the efficacy of room fumigation with vaporized hydrogen peroxide (VHP) in decontamination of viable Mycobacterium tuberculosis.

METHODS AND RESULTS

About 8 x 10(4)-2.3 x 10(6) CFU of M. tuberculosis H37Rv and M. tuberculosis Beijing were dried in 10-microl drops in tissue culture plates, placed in steam-permeable Tyvek pouches and distributed on laboratory surfaces. The room was exposed to VHP delivered by air conditioning. Different exposure conditions were tested. Exposure to VHP resulted in sterilization of the bacterial samples in three different test runs.

CONCLUSIONS

VHP treatment is an effective means of reducing and eliminating room contaminations of M. tuberculosis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Fumigation with VHP represents an alternative to formaldehyde fumigation, particularly for decontamination of animal rooms in tuberculosis research laboratories.

Preparation of a standardized, efficacious agricultural H5N3 vaccine by reverse genetics

Options for the control of emerging and reemerging H5N1 influenza viruses include improvements in biosecurity and the use of inactivated vaccines. Commercially available H5N2 influenza vaccine prevents disease signs and reduces virus load but does not completely prevent virus shedding after challenge with H5N1 virus. By using reverse genetics, we prepared an H5N3 vaccine whose hemagglutinin is 99.6% homologous to that of A/CK/HK/86.3/02 (H5N1). We used the internal genes of A/PR/8/34 and the H5 of A/Goose/HK/437.4/99 (H5N1) after deletion of basic amino acids from its connecting peptide region. The resulting virus was not lethal to chicken embryos and grew to high HA titers in eggs, allowing preparation of HA protein-standardized vaccine in unconcentrated allantoic fluid. The N3 neuraminidase, derived from A/Duck/Germany/1215/73 (H2N3), permitted discrimination between vaccinated and naturally infected birds. The virus construct failed to replicate in quail and chickens. Similar to parental A/PR/8/34 (H1N1), it replicated in mice and ferrets and spread to the brains of mice; therefore, it should not be used as a live-attenuated vaccine. The H5N3 vaccine, at doses of 1.2 microg HA, induced HI antibodies in chickens and prevented death, signs of disease, and markedly reduced virus shedding after challenge with A/CK/HK/86.3/02 (H5N1) but did not provide sterilizing immunity. Thus, reverse genetics allows the inexpensive preparation of standardized, efficacious H5N3 poultry vaccines that may also reduce the reemergence of H5N1 genotypes.

A systems interpretation for observations of bird V-formations

Birds in V formations are frequently observed and two main hypotheses have emerged to explain this particular geometry: (i) it offers aerodynamic advantages and (ii) it is used to improve visual communication. Both explanations require a bird to track its predecessor. However, most V-formations observed in nature are small and the distribution of wing-tip spacings has a large variation. This suggests that tracking the lateral position of the preceding bird is a difficult task. Control theorists, when trying to control platoons of vehicles, also noted that predecessor following is difficult. In this paper, we apply a result from systems theory to explain the observations of bird V-formations. The strength of this result is that it does not rely on the details of the bird flight model. Thus we claim that formation flight is inherently difficult for birds.

Limited mycobacterial infection of the liver as a consequence of its microanatomical structure causing restriction of mycobacterial growth to professional phagocytes

Among sites of extrapulmonary growth of Mycobacterium tuberculosis, the liver is the least infected. Our data suggest that this is due to the complete restriction of mycobacterial growth to liver macrophages. Unlike in organs more persistently seeded by M. tuberculosis, in the liver the bacteria do not infect cell types other than professional phagocytes.

Tetrathiafulvalene-acetylene scaffolding: new pi-electron systems for advanced materials

Novel extended tetrathiafulvalenes (TTFs) with hexa-2,4-diyne-1,6-diylidene spacers between the two 1,3-dithiole rings and laterally appended alkynyl moieties for one- and two-dimensional scaffolding were synthesised and investigated for their electronic properties.

Highly functionalized dimeric tetraethynylethenes and expanded radialenes: strong evidence for macrocyclic cross-conjugation

A selection of dimeric tetraethynylethenes (TEEs) and perethynylated expanded radialenes, containing different donor/acceptor substitution patterns, have been prepared and fully characterized. The first X-ray crystal structure of an expanded [6]radialene, with twelve peripheral 3,5-di(tert-butyl)phenyl substituents, is presented. This macrocycle, the all-carbon core of which is isomeric with fullerene C60, adopts a non-planar, "chair-like" conformation. Also a TEE dimer, carrying N,N-dimethylaniline donor substituents, has been subjected to an X-ray crystallographic analysis. The electronic properties were studied by UV/Vis spectroscopy and electrochemistry, providing fundamental insight into mechanisms of pi-electron delocalization in the acyclic and macrocyclic chromophores. Donor or donor-acceptor-substituted dimeric TEE derivatives show very strong absorptions extending over the entire UV/Vis region; their longest wavelength absorption bands have high charge-transfer character. Macrocyclic cross-conjugation in the expanded radialenes becomes increasingly efficient with increasing donor-acceptor polarization. A dual, strongly solvent-polarity-dependent fluorescence was observed for a tetrakis(N,N-dimethylaniline)-substituted dimeric TEE; this interesting emission behavior is explained by the twisted intramolecular charge-transfer (TICT) state model. Donor-substituted expanded radialenes display huge resonance-enhanced third-order nonlinear optical coefficients.

Additive effect of neutralizing antibody and antiviral drug treatment in preventing virus escape and persistence

Poorly cytopathic or noncytopathic viruses can escape immune surveillance and establish a chronic infection. Here we exploited the strategy of combining antiviral drug treatment with the induction of a neutralizing antibody response to avoid the appearance of neutralization-resistant virus variants. Despite the fact that H25 immunoglobulin transgenic mice infected with lymphocytic choriomeningitis virus mounted an early neutralizing antibody response, the virus escaped from neutralization and persisted. After ribavirin treatment of H25 transgenic mice, the appearance of neutralization-resistant virus was prevented and virus was cleared. Thus, the combination of virus-neutralizing antibodies and chemotherapy efficiently controlled the infection, whereas each defense line alone did not. Similar additive effects may be unexpectedly efficient and beneficial in humans after infections with persistent viruses such as hepatitis C virus and hepatitis B virus and possibly human immunodeficiency virus.

Sperm number and condition affect the number of basal cells and their expression of macrophage antigen in the murine epididymis

Unilateral ligation of the mid-corpus epididymis, the proximal vas deferens and imposition of an abdominal temperature for 6 days as well as bilateral castration for 3, 6 or 14 days, resulted in a change in epithelial composition of the adult murine epididymis with regard to the number and antigen expression of basal cells. There were fewer basal cells per tubule cross-section with fewer expressing F4/80 antigen when spermatozoa were absent from the proximal lumen following short-term castration. Conversely, more basal cells with more of them demonstrating macrophage antigen expression were evident when more or damaged spermatozoa were in the proximal lumen after corpus ligation and exposure to abdominal temperature or in the cauda after long-term withdrawal of androgen support. By contrast, ligation of the vas deferens did not lead to tubule distension, and hence sperm accumulation, and did not alter the basal cell population in the cauda epididymis. The data suggest that epididymal basal cells respond in number and macrophage antigen expression to the presence of sperm autoantigens in the lumen with little dependence on circulating androgens. These changes may represent responses to minimise the interaction of sperm autoantigens with the immune system and the risk of immunological infertility.

Rapid neutrophil response controls fast-replicating intracellular bacteria but not slow-replicating Mycobacterium tuberculosis

Being one of the first cells to invade the site of infection, neutrophils play an important role in the control of various bacterial and viral infections. In the present work, the contribution of neutrophils to the control of infection with different intracellular bacteria was investigated. Mice were treated with the neutrophil-depleting monoclonal antibody RB6-8C5, and the time course of infection in treated and untreated mice was compared by using intracellular bacterial species and strains varying in virulence and replication rate. The results indicate that neutrophils are crucial for the control of fast-replicating intracellular bacteria, whereas early neutrophil effector mechanisms are dispensable for the control of the slow-replicating Mycobacterium tuberculosis.