Estimate of the incidence of PANDAS and PANS in 3 primary care populations.

Objective: Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal infection (PANDAS) and Pediatric Acute-Onset Neuropsychiatric syndrome (PANS) are presumed autoimmune complications of infection or other instigating events. To determine the incidence of these disorders, we performed a retrospective review for the years 2017-2019 at three academic medical centers. Methods: We identified the population of children receiving well-child care at each institution. Potential cases of PANS and PANDAS were identified by including children age 3-12 years at the time they received one of five new diagnoses: avoidant/restrictive food intake disorder, other specified eating disorder, separation anxiety disorder of childhood, obsessive-compulsive disorder, or other specified disorders involving an immune mechanism, not elsewhere classified. Tic disorders was not used as a diagnostic code to identify cases. Data were abstracted; cases were classified as PANDAS or PANS if standard definitions were met. Results: The combined study population consisted of 95,498 individuals. The majority were non-Hispanic Caucasian (85%), 48% were female and the mean age was 7.1 (SD 3.1) years. Of 357 potential cases, there were 13 actual cases [mean age was 6.0 (SD 1.8) years, 46% female and 100% non-Hispanic Caucasian]. The estimated annual incidence of PANDAS/PANS was 1/11,765 for children between 3 and 12 years with some variation between different geographic areas. Conclusion: Our results indicate that PANDAS/PANS is a rare disorder with substantial heterogeneity across geography and time. A prospective investigation of the same question is warranted.

Binding by the hepatitis C virus NS3 helicase partially melts duplex DNA.

Binding of NS3 helicase to DNA was investigated by footprinting with KMnO(4), which reacts preferentially with thymidine residues in single-stranded DNA (ssDNA) compared to those in double-stranded DNA (dsDNA). A distinct pattern of reactivity was observed on ssDNA, which repeated every 8 nucleotides (nt) and is consistent with the known binding site size of NS3. Binding to a DNA substrate containing a partial duplex was also investigated. The DNA contained a 15 nt overhang made entirely of thymidine residues adjacent to a 22 bp duplex that contained thymidine at every other position. Surprisingly, the KMnO(4) reactivity pattern extended from the ssDNA into the dsDNA region of the substrate. Lengthening the partial duplex to 30 bp revealed a similar pattern extending from the ssDNA into the dsDNA, indicating that NS3 binds within the duplex region. Increasing the length of the ssDNA portion of the partial duplex by 4 nt resulted in a shift in the footprinting pattern for the ssDNA by 4 nt, which is consistent with binding to the 3'-end of the ssDNA. However, the footprinting pattern in the dsDNA region was shifted by only 1-2 bp, indicating that binding to the ssDNA-dsDNA region was preferred. Footprinting performed as a function of time indicated that NS3 binds to the ssDNA rapidly, followed by slower binding to the duplex. Hence, multiple molecules of NS3 can bind along a ssDNA-dsDNA partial duplex by interacting with the ssDNA as well as the duplex DNA.

Probing RNA translocases with DNA.

For some helicases, it is possible to investigate RNA translocase activity on DNA substrates because the enzyme acts on both substrates. Potassium permanganate (KMnO4) footprinting is a method used to chemically probe the conformation of DNA as well as the binding of proteins. Combining footprinting methods with rapid mixing methods that utilize a chemical quench-flow instrument can enable tracking of the translocase with nucleotide resolution.