Serologic Evidence of Severe Fever with Thrombocytopenia Syndrome Virus and Related Viruses in Pakistan.

We describe the seroprevalence of severe fever with thrombocytopenia syndrome virus (SFTSV) and the association of antibody occurrence with location, sex, and age among the human population in Pakistan. Our results indicate substantial activity of SFTSV and SFTSV-related viruses in this country.

Detection of Anti-Hepatitis B Virus Drug Resistance Mutations Based on Multicolor Melting Curve Analysis.

Detection of anti-hepatitis B virus (HBV) drug resistance mutations is critical for therapeutic decisions for chronic hepatitis B virus infection. We describe a real-time PCR-based assay using multicolor melting curve analysis (MMCA) that could accurately detect 24 HBV nucleotide mutations at 10 amino acid positions in the reverse transcriptase region of the HBV polymerase gene. The two-reaction assay had a limit of detection of 5 copies per reaction and could detect a minor mutant population (5% of the total population) with the reverse transcriptase M204V amino acid mutation in the presence of the major wild-type population when the overall concentration was 104 copies/µl. The assay could be finished within 3 h, and the cost of materials for each sample was less than $10. Clinical validation studies using three groups of samples from both nucleos(t)ide analog-treated and -untreated patients showed that the results for 99.3% (840/846) of the samples and 99.9% (8,454/8,460) of the amino acids were concordant with those of Sanger sequencing of the PCR amplicon from the HBV reverse transcriptase region (PCR Sanger sequencing). HBV DNA in six samples with mixed infections consisting of minor mutant subpopulations was undetected by the PCR Sanger sequencing method but was detected by MMCA, and the results were confirmed by coamplification at a lower denaturation temperature-PCR Sanger sequencing. Among the treated patients, 48.6% (103/212) harbored viruses that displayed lamivudine monoresistance, adefovir monoresistance, entecavir resistance, or lamivudine and adefovir resistance. Among the untreated patients, the Chinese group had more mutation-containing samples than did the Pakistani group (3.3% versus 0.56%). Because of its accuracy, rapidness, wide-range coverage, and cost-effectiveness, the real-time PCR assay could be a robust tool for the detection if anti-HBV drug resistance mutations in resource-limited countries.

Rapid detection of HCV genotyping 1a, 1b, 2a, 3a, 3b and 6a in a single reaction using two-melting temperature codes by a real-time PCR-based assay.

The genotype of the hepatitis C virus (HCV) is an important indicator for antiviral therapeutic response. We hereby described development of a rapid HCV genotyping approach that enabled the identification of the six most common HCV subtypes of Asia, i.e., 1a, 1b, 2a, 3a, 3b, and 6a, in a single reaction. Using two dual-labeled, self-quenched probes that target the core region of the HCV genome, the exact subtype could be accurately identified by two-melting temperature codes determined from the two respective probes in a real-time PCR assay. Analytical sensitivity studies using armored RNA samples representing each of the six HCV subtypes showed that 5 copies/reaction of HCV RNA could be detected. The assay was evaluated using 244 HCV-positive serum samples and the results were compared with sequencing analysis. Of the 224 samples, subtype 3a (127, 52.3%) was the dominant, followed by 1b (51, 20.9%), 3b (47, 19.3%), 2a (8, 3.3%), 6a (4, 1.6%) and the least was subtype 1a (1, 0.4%). Moreover, 6 (2.5%) mixed infection samples were also detected. These results were fully concordant with sequencing analysis. We concluded that this real-time PCR-based assay could provide a rapid and reliable tool for routine HCV genotyping in most Asian countries.