Definition of an HBsAg to DNA international unit conversion factor by enrichment of circulating hepatitis B virus forms.

Hepatitis B (HBV) virus infection is characterized by the overproduction of subviral particles (SVP) over infectious Dane particles (VP). Precise regulation of the ratio between these forms is unknown, but its fluctuation may have a clinical impact. An enrichment method was applied to assess the SVP/VP ratio in chronically infected patients (CHB) and to compare the sensitivity of HBs antigen (HBsAg) and DNA detection methods. Plasmas from 9 genotype A-D CHB patients were fractionated on Nycodenz(®) gradients, and both HBV DNA and HBsAg were quantified in each collected fraction using standardized techniques expressed in IU/mL. Infection of primary human hepatocytes (PHHs) was performed with crude or fractionated plasma. Independently of the genotype, all plasmas showed a similar rate-zonal separation profile characterized by a bottom DNA-enriched peak surmounted by HBsAg-enriched fractions. Inoculation of PHH with plasma-derived VP-enriched fractions led to long-lasting production of virus in cell supernatants with a SVP/VP ratio similar to that observed in patient plasmas. In the VP fraction, one IU of HBsAg corresponded to approximately 5 million IU of HBV DNA. Rate-zonal gradient separation directly applied on patient plasma allows a better insight into the distribution of VP in HBeAg-positive CHB carriers. This study highlights the sensitivity difference of the techniques classically used to monitor HBV infection and indicates that VP-associated HBsAg contributes modestly to the overall amount of total circulating HBsAg in CHB. Such a fractionation approach should help to understand the fine regulation of HBsAg production over replication at different stages of CHB.

The Plasmodium PI(4)K inhibitor KDU691 selectively inhibits dihydroartemisinin-pretreated Plasmodium falciparum ring-stage parasites.

Malaria control and elimination are threatened by the emergence and spread of resistance to artemisinin-based combination therapies (ACTs). Experimental evidence suggests that when an artemisinin (ART)-sensitive (K13 wild-type) Plasmodium falciparum strain is exposed to ART derivatives such as dihydroartemisinin (DHA), a small population of the early ring-stage parasites can survive drug treatment by entering cell cycle arrest or dormancy. After drug removal, these parasites can resume growth. Dormancy has been hypothesized to be an adaptive physiological mechanism that has been linked to recrudescence of parasites after monotherapy with ART and, possibly contributes to ART resistance. Here, we evaluate the in vitro drug sensitivity profile of normally-developing P. falciparum ring stages and DHA-pretreated dormant rings (DP-rings) using a panel of antimalarial drugs, including the Plasmodium phosphatidylinositol-4-OH kinase (PI4K)-specific inhibitor KDU691. We report that while KDU691 shows no activity against rings, it is highly inhibitory against DP-rings; a drug effect opposite to that of ART. Moreover, we provide evidence that KDU691 also kills DP-rings of P. falciparum ART-resistant strains expressing mutant K13.

[Preliminary study of transcutaneous oxygen partial pressure in adults after discontinuing normobaric hyperoxia during intubation]. / Etude préliminaire de la PO2 transcutanée de l'adulte à l'arrêt de l'hyperoxie normobarique pour intubation.

When tracheal intubation is conducted with traditional laryngoscope PtcO2 fall during the first minute after intubation; when continuous O2 supplied laryngoscope (Laryng O2) is used PtcO2 rise; the difference is statistically significant (p less than 0.001) either the subjects are in curarisation apnea or in spontaneous ventilation. With traditional laryngoscope, the fall is faster with spontaneous ventilation conditions than during curarisation apnea. Likewise in normal conscient subject the same fall is faster (p less than 0.001) during first minute of posthyperoxic spontaneous quiet ventilation than the first minute of voluntary hypocapnic apnea induced by hyperventilation during the same hyperoxia. Such results have to be taken into account for the indications of tracheal intubation technical means if hypoxic conditions are to be suspected, particularly for infants and subjects with cardio-respiratory failure.