Development and Validation of an Assay To Detect Porcine Reproductive and Respiratory Syndrome Virus-Specific Neutralizing Antibody Titers in Pig Oral Fluid Samples

Porcine reproductive and respiratory syndrome virus (PRRSV)-specific neutralizing antibodies (NA) are important for clearing the virus. Pen-based pig oral fluid samples for disease surveillance are gaining in importance due to the ease of collection and low cost. The aim of this study was to develop a PRRSV-specific NA assay to determine NA titers in pig oral fluid samples. At first, we standardized the PRRSV NA assay using pen-based pig oral fluid samples collected over a period of 3 months from a herd of swine that received a PRRSV modified live vaccine (PRRS-MLV), and we also used oral fluid and serum samples collected from individual boars that were vaccinated with PRRS-MLV or infected with a virulent PRRSV strain. Our results suggest that a PRRSV NA titer of >8 in oral fluid samples is virus specific and can be detected beginning at 28 days after vaccination or infection. To validate the assay, we used 104 pen-based pig oral fluid and five representative serum samples from each pen of unknown history, as well as 100 serum samples from repeatedly vaccinated sows and oral fluid samples of their respective litters belonging to four different swine-breeding farms. Our results demonstrated that PRRSV NA titers in oral fluid samples are correlated with serum sample titers, and maternally derived PRRSV-specific NA titers could be detected in litters at the time of weaning. In conclusion, we have standardized and validated the pig oral fluid-based PRRSV NA assay, which has 94.3% specificity and 90.5% repeatability. The assay can be used to monitor herd immunity against PRRSV in vaccinated and infected herds of swine.     

Development of a Fluorescent Microsphere Immunoassay for Detection of Antibodies against Porcine Reproductive and Respiratory Syndrome Virus Using Oral Fluid Samples as an Alternative to Serum-Based Assays

For effective disease surveillance, rapid and sensitive assays are needed to detect antibodies developed in response to porcine reproductive and respiratory syndrome virus (PRRSV) infection. In this study, we developed a multiplexed fluorescent microsphere immunoassay (FMIA) for detection of PRRSV-specific antibodies in oral fluid and serum samples. Recombinant nucleocapsid protein (N) and nonstructural protein 7 (nsp7) from both PRRSV genotypes (type I and type II) were used as antigens and covalently coupled to Luminex fluorescent microspheres. Based on an evaluation of 488 oral fluid samples with known serostatus, the oral fluid-based FMIAs achieved >92% sensitivity and 91% specificity. For serum samples (n = 1,639), the FMIAs reached >98% sensitivity and 95% specificity. The assay was further employed to investigate the kinetics of the antibody response in infected pigs. In oral fluid, the N protein was more sensitive for the detection of early infection (7 and 14 days postinfection), but nsp7 detected a higher level and longer duration of antibody response (28 days postinfection). In serum, the antibodies specific to nsp7 and N proteins were detected as early as 7 days postinfection, and the responses lasted more than 202 days. This study provides a framework from which a more robust assay could be developed to profile the immune response to multiple PRRSV antigens in a single test. The development of oral fluid-based diagnostic tests will change the way we survey diseases in swine herds and improve our ability to cheaply and efficiently track PRRSV infections in both populations and individual animals.     

Frequency of thiopurine S-methyltransferase genetic variation in Thai children with acute leukemia

BACKGROUND: Thiopurine S-methyltransferase (TPMT) catalyzes the S-methylation (inactivation) of mercaptopurine, azathioprine, and thioguanine, and exhibits genetic variation. About 11% of Caucasians have intermediate TPMT activity because of heterozygosity, and about 1 in 300 inherits TPMT deficiency as an autosomal codominant trait. If patients who have intermediate or deficient TPMT activity receive the standard dose of thiopurine medications, they can accumulate excessive thiopurine nucleotides in hematopoietic tissue, which could lead to severe and possibly fatal myelosuppression. There is very little information about TPMT genetic variation among Asian populations. We investigated the frequency of TPMT genetic variation among Thai children with acute leukemia. PROCEDURE: Fresh whole blood was obtained from 75 Thai children with acute leukemia at the time of remission. Genomic DNA was isolated from total peripheral white blood cells. We performed polymerase chain reaction (PCR) to detect 3 types of variant of the human TPMT gene. RESULTS: Among 75 patients, the frequency of heterozygotes for the TPMT gene among Thai children with acute leukemia was approximately 11%. However, the TPMT*3C was the only variant TPMT allele found among Thai children. This is different from the North American Caucasian populations, in which TPMT*3A is the predominant variant allele, and TPMT*3C is rare (approximately 5% of variant alleles). CONCLUSIONS: There is no difference in the frequency of this genetic variation between Asian and North American Caucasian populations. Determination of the TPMT genotype by PCR method before antileukemic therapy is practical and may have clinical relevance. This knowledge could be applied towards organ transplant recipients who require these medications for immunosuppression.     

Application of smart phone in Better Border Healthcare Program: A module for mother and child care

Background  

To assess the application of cell phone integrating into the healthcare system to improve antenatal care (ANC) and expanded programme on immunization (EPI) services for the under-served population in border area.