Hepatitis C Virus Micro-elimination Among People With HIV in San Diego: Are We on Track?

Background: Rising incidence of hepatitis C virus (HCV) among people with HIV (PWH) in San Diego County (SDC) was reported. In 2018, the University of California San Diego (UCSD) launched a micro-elimination initiative among PWH, and in 2020 SDC launched an initiative to reduce HCV incidence by 80% across 2015-2030. We model the impact of observed treatment scale-up on HCV micro-elimination among PWH in SDC. Methods: A model of HCV transmission among people who inject drugs (PWID) and men who have sex with men (MSM) was calibrated to SDC. The model was additionally stratified by age, gender, and HIV status. The model was calibrated to HCV viremia prevalence among PWH in 2010, 2018, and 2021 (42.1%, 18.5%, and 8.5%, respectively), and HCV seroprevalence among PWID aged 18-39 years, MSM, and MSM with HIV in 2015. We simulate treatment among PWH, weighted by UCSD Owen Clinic (reaching 26% of HCV-infected PWH) and non-UCSD treatment, calibrated to achieve the observed HCV viremia prevalence. We simulated HCV incidence with observed and further treatment scale-up (+/- risk reductions) among PWH. Results: Observed treatment scale-up from 2018 to 2021 will reduce HCV incidence among PWH in SDC from a mean of 429 infections/year in 2015 to 159 infections/year in 2030. County-wide scale-up to the maximum treatment rate achieved at UCSD Owen Clinic (in 2021) will reduce incidence by 69%, missing the 80% incidence reduction target by 2030 unless accompanied by behavioral risk reductions. Conclusions: As SDC progresses toward HCV micro-elimination among PWH, a comprehensive treatment and risk reduction approach is necessary to reach 2030 targets.

Ablation of a Ca2+-activated K+ channel (SK2 channel) results in action potential prolongation in atrial myocytes and atrial fibrillation.

Small conductance Ca(2+)-activated K(+) channels (SK channels) have been reported in excitable cells, where they aid in integrating changes in intracellular Ca(2+) (Ca(2+)(i)) with membrane potential. We have recently reported the functional existence of SK2 channels in human and mouse cardiac myocytes. Moreover, we have found that the channel is predominantly expressed in atria compared to the ventricular myocytes. We hypothesize that knockout of SK2 channels may be sufficient to disrupt the intricate balance of the inward and outward currents during repolarization in atrial myocytes. We further predict that knockout of SK2 channels may predispose the atria to tachy-arrhythmias due to the fact that the late phase of the cardiac action potential is highly susceptible to aberrant excitation. We take advantage of a mouse model with genetic knockout of the SK2 channel gene. In vivo and in vitro electrophysiological studies were performed to probe the functional roles of SK2 channels in the heart. Whole-cell patch-clamp techniques show a significant prolongation of the action potential duration prominently in late cardiac repolarization in atrial myocytes from the heterozygous and homozygous null mutant animals. Moreover, in vivo electrophysiological recordings show inducible atrial fibrillation in the null mutant mice but not wild-type animals. No ventricular arrhythmias are detected in the null mutant mice or wild-type animals. In summary, our data support the important functional roles of SK2 channels in cardiac repolarization in atrial myocytes. Genetic knockout of the SK2 channels results in the delay in cardiac repolarization and atrial arrhythmias.