A Cell-Adapted Live-Attenuated Vaccine Candidate Protects Pigs against the Homologous Strain VNUA-ASFV-05L1, a Representative Strain of the Contemporary Pandemic African Swine Fever Virus.

African swine fever (ASF) is a lethal and highly contagious transboundary animal disease with the potential for rapid international spread. Currently, there is no ASF vaccine commercially available. All infected animals must be isolated and culled immediately upon the confirmation of the presence of the virus. Studies leading to the rational development of protective ASF vaccines are urgently needed. Here, we generated a safe and efficacious live-attenuated vaccine (LAV) VNUA-ASFV-LAVL2 by serially passaging a field isolate (VNUA-ASFV-05L1, genotype II) in porcine alveolar macrophages (PAMs, 65 passages) and an immortalized porcine alveolar macrophage cell line (3D4/21, 55 passages). VNUA-ASFV-LAVL2 can efficiently replicate in both PAMs and 3D4/21 cells. It provides 100% protection, even with the low dose of 102 HAD50, to the vaccinated pigs against the challenge of contemporary pandemic ASFV field isolate. Pigs vaccinated with this LAV in a dose range of 102 to 105 HAD50 remained clinically healthy during both the 28-day observation period of immunization and the 28-day observation period of challenge. VNUA-ASFV-LAVL2 was eliminated from blood by 28 days post-inoculation (DPI), and from feces or oral fluids by 17 DPI. Although the vaccine strain in serum remained a safe and attenuated phenotype after five passages in swine, a reversion-to-virulence study using blood or tissue homogenates at peak viremia will be conducted in the future. ASFV-specific IgG antibodies and significant cellular immunity were detected in vaccinated pigs before the ASFV challenge. These results indicate that the VNUA-ASFV-LAVL2 strain is a safe and efficacious LAV against the genotype II ASFV strain responsible for current ASF outbreaks in Asia.

A Multiplex PCR Method for Simultaneous Detection of Infectious Laryngotracheitis Virus and Ornithobacterium rhinotracheale.

To date, many fluorescence- and gel-based multiplex polymerase chain reaction (PCR) assays have been developed for the simultaneous detection of multiple infectious agents of respiratory disease in poultry. However, PCR assays are not available for other important emerging respiratory bacteria, such as Ornithobacterium rhinotracheale (ORT). We aimed to fill this gap by establishing a new duplex PCR method for the simultaneous detection of infectious laryngotracheitis virus (ILTV) and ORT. Multiplex primer design software was used to select the compatible multiplex primer pairs. It was determined that an annealing temperature of 65 °C and an initial concentration of 2.5 pmol/µL for each primer set were the most suitable conditions for multiplex PCR. The assay was confirmed to be specific, as it only detected the target pathogens, even in the presence of six non-target agents. The limit of detection was up to 103 copies/µL of template DNA for both ILTV and ORT. In the screening of 304 field samples, 23, 88, and 44 were positive for both ILTV and ORT, solely for ILTV, and solely ORT, respectively.

Serological and Molecular Characterization of Avian Metapneumovirus in Chickens in Northern Vietnam.

Avian Metapneumovirus (aMPV) is a causative agent of respiratory disease complex in turkeys and chickens that has recently been detected in Vietnam. Due to its novelty, this study was conducted to elucidate the distribution of aMPV in several provinces in northern Vietnam. By the application of Enzyme-Linked Immunosorbent Assay (ELISA) and nested Reverse Transcription-Polymerase Chain Reaction (RT-PCR), this study demonstrated the circulation of aMPV in 12 out of 14 cities/provinces with positive rates of 37.6% and 17.2%, respectively. All nested RT-PCR positive samples were aMPV subgroup B. By pairing the detection results with age groups, it was observed that aMPV infections occurred in chickens of all ages. Additionally, by genetic characterization, aMPV strains were demonstrated to not be attenuated vaccine viruses and to belong to at least two genetic clades. Overall, the obtained results provided insights into the prevalence of aMPV and indicated a greater complexity of respiratory diseases in chickens in Vietnam.

Application of HPLC in quantity of plasma rifampicin in patient taking simultaneously rifampicin - isoniazid - pyrazinamide

A HPLC method has been used to quantify plasma rifampicin and isoniazid and pyrazinamide simultaneously. Extraction of rifampicin in plasma samples was done as follows: mix 1ml of plasma containing rifampicin and 1.5 ml acetonitril on a vortex mixer for 1 minute prior to centrifugation at 3500 rpm for 30 minutes. The organic layer was filtered through 0.45m filter membrane and then 30l of this solution was injected into the HPLC system. The chromatographic conditions were as follows: in stationary phase: column: Apollo Alltech RP18 (250 x 4.6 mm; 5 m); in mobile phase: methanol - phosphate buffet solution containing 0.02M potassium dihydrogen phosphate adjusted to pH 4.5 by adding phosphoric acid (65: 35); Flow rate: 1.0 ml/min and UV detector: 254 nm

Comparison of bioavailability of rifampicin in fixed dose combination (3-FDC) with standard separate tablet

Study on 12 healthy volunteers using 2 types of medication: rifampicin, isoniazid, and pyrazinamid standard separate tablets and in fixed dose combination of rifampicin + isoniazid + pyrazinamid (3- FDC). Results: rifampicin is one of essential anti-tuberculosis drugs that have most advantages of pharmacodynamics on both intra- and extra-cellular bacteria. Cmax (maximum concentration in plasma) and AUC 0-∞ (Area Under the Concentration-Time Curve) of rifampicin in 3- FDC is lower than that in standard separate tablet, Tmax (Time to Maximum Plasma Concentration) of rifampicin in 3- FDC is more slowly than in standard separate tablet. These findings showed that the bioavailability of rifampicin in FDC tablet that was using in treating tuberculosis is much lower than in standard separate tablet.

Study on evaluation of bioavailability of rifampicin in mixed antituberculous drug with 2 and 3 components available in Vietnam

Comparative bioavailability study of rifampicin from 2-FDC and 3- FDC with standard separate tablets at the same dose level was conducted in 12 healthy volunteers. The study was designed as a cross-over experiment with a washout period of 1 week. Bioavailability of rifampicin was estimated by plasma concentration of rifampicin from Oh to 24h after dosed. Plasma rifampicin concentration was determined by HPLC method. The results revealed that: Cmax and AVC for rifampicin in 2-FDC and 3FDC formulation were lower (but Tmax were higher) than the standard separate formulations. It was concluded that FDC tablets are of poor relative bioavailabity of rifampicin. The implication for National Tuberculosis Programme is extremely serious and warrants urgent attention