Jason Wong

The Effect of Lipid Environment and Retinoids on the ATPase Activity of ABCR, the Photoreceptor ABC Transporter Responsible for Stargardt Macular Dystrophy

ABCR is a photoreceptor-specific ATP-binding cassette transporter that has been linked to various retinal diseases, including Stargardt macular dystrophy, and implicated in retinal transport across rod outer segment (ROS) membranes. We have examined the ATPase and GTPase activity of detergent-solubilized and reconstituted ABCR. 3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonic acid-solubilized ABCR had ATPase and GTPase activity (K m ∼75 μm;V max ∼ 200 nmol/min/mg) that was stimulated 1.5–2-fold by all-trans-retinal and dependent on phospholipid and dithiothreitol. The K m for ATP decreased to ∼25 μm after reconstitution, whereas theV max was strongly dependent on the lipid used for reconstitution. ABCR reconstituted in ROS phospholipid had aV max for basal and retinal activated ATPase activity that was 4–6 times higher than for ABCR in soybean or brain phospholipid. This enhanced activity was mainly due to the high phosphatidylethanolamine (PE) content of ROS membranes. PE was also required for retinoid-stimulated ATPase activity. ATPase activity of ABCR was stimulated by the addition ofN-retinylidene-PE but not the reduced derivative, retinyl-PE. ABCR expressed in COS-1 cells also exhibited retinal-stimulated ATPase activity similar to that of the native protein. These results support the view that ABCR is an active retinoid transporter, the nucleotidase activity of which is strongly influenced by its lipid environment.

Near real-time monitoring of HIV transmission hotspots from routine HIV genotyping: an implementation case study

Background Due to the rapid evolution of HIV, infections with similar genetic sequences are likely to be related by recent transmission events. Clusters of related infections can represent subpopulations with high rates of HIV transmission. Here we describe the implementation of an automated “near real-time” system using clustering analysis of routinely collected HIV resistance genotypes to monitor and characterize HIV transmission hotspots in British Columbia (BC). Methods A monitoring system was implemented on the BC Drug Treatment Database, which currently holds over 32000 anonymized HIV genotypes for nearly 9000 residents of BC living with HIV. On average, five to six new HIV genotypes are deposited in the database every day, which triggers an automated re-analysis of the entire database. Clusters of five or more individuals were extracted on the basis of short phylogenetic distances between their respective HIV sequences. Monthly reports on the growth and characteristics of clusters were generated by the system and distributed to public health officers. Findings In June 2014, the monitoring system detected the expansion of a cluster by 11 new cases over three months, including eight cases with transmitted drug resistance. This cluster generally comprised young men who have sex with men. The subsequent report precipitated an enhanced public health follow-up to ensure linkage to care and treatment initiation in the affected subpopulation. Of the nine cases associated with this follow-up, all had already been linked to care and five cases had started treatment. Subsequent to the follow-up, three additional cases started treatment and the majority of cases achieved suppressed viral loads. Over the following 12 months, 12 new cases were detected in this cluster with a marked reduction in the onward transmission of drug resistance. Interpretation Our findings demonstrate the first application of an automated phylogenetic system monitoring a clinical database to detect a recent HIV outbreak and support the ensuing public health response. By making secondary use of routinely collected HIV genotypes, this approach is cost-effective, attains near realtime monitoring of new cases, and can be implemented in all settings where HIV genotyping is the standard of care. Funding This work was supported by the BC Centre for Excellence in HIV/AIDS and by grants from the Canadian Institutes for Health Research (CIHR HOP-111406, HOP-107544), the Genome BC, Genome Canada and CIHR Partnership in Genomics and Personalized Health (Large-Scale Applied Research Project HIV142 contract to PRH, JSGM, and AFYP), and by the US National Institute on Drug Abuse (1-R01-DA036307-01, 5-R01-031055-02, R01-DA021525-06, and R01-DA011591).

Long-term effect of sustained virological response on hepatocellular carcinoma in patients with hepatitis C in Canada

BACKGROUND & AIMS Evidence is limited on hepatocellular carcinoma (HCC) risk after sustained virological response (SVR) to interferon-based treatment of hepatitis C virus (HCV) infection. We evaluated the effect of SVR on the risk of HCC and estimated its incidence in post-SVR HCV patients from a large population-based Canadian cohort. METHODS The British Columbia Hepatitis Testers Cohort includes individuals tested for HCV between 1990-2013 linked with data on their medical visits, hospitalizations, cancers, prescription drugs and mortality. Patients receiving interferon-based HCV treatments were followed from the end of treatment to HCC diagnosis, death or December 31, 2012. We examined HCC risk among those who did and did not achieve SVR using multivariable proportional hazard models with the Fine and Gray modification for competing risks. RESULTS Of 8147 individuals who received HCV treatment and were eligible for analysis, 4663 (57%) achieved SVR and 3484 (43%) did not. Each group was followed for a median of 5.6years (range: 0.5-12.9) for an HCC incidence rate of 1.1/1000 person-years (PY) among the SVR and 7.2/1000 PY among the no SVR group. The HCC incidence rate was higher among those with cirrhosis (SVR: 6.4, no SVR: 21.0/1000 PY). In the multivariable model, SVR was associated with a lower HCC risk (subdistribution hazard ratio [SHR]=0.20, 95% CI: 0.13-0.3), while cirrhosis (SHR=2.61, 95% CI: 1.68-4.04), age ⩾50years, being male and genotype 3 infection were associated with a higher HCC risk. Among those who achieved SVR, cirrhosis, age ⩾50years and being male were associated with a higher HCC risk. CONCLUSION SVR after interferon-based treatment substantially reduces but does not eliminate HCC risk, which is markedly higher among those with cirrhosis and age ⩾50years at treatment initiation. Treatment of patients at an advanced fibrosis stage with new highly effective drugs will warrant continued surveillance for HCC post-SVR. LAY SUMMARY We assessed the effect of successful hepatitis C treatment with older interferon-based treatment on the occurrence of liver cancer (hepatocellular carcinoma) and found that successful treatment prevents liver cancer. However, more people with cirrhosis and older age continued to develop liver cancer after successful treatment. Thus, treatment with new drugs among those with cirrhosis will require continued monitoring for liver cancer.

Incidence, risk factors, and prevention of hepatitis C reinfection: a population-based cohort study

BACKGROUND People remain at risk of reinfection with hepatitis C virus (HCV), even after clearance of the primary infection. We identified factors associated with HCV reinfection risk in a large population-based cohort study in British Columbia, Canada, and examined the association of opioid substitution therapy and mental health counselling with reinfection. METHODS We obtained data from the British Columbia Hepatitis Testers Cohort, which includes all individuals tested for HCV or HIV at the British Columbia Centre for Disease Control Public Health Laboratory during 1990-2013 (when data were available). We defined cases of HCV reinfection as individuals with a positive HCV PCR test after either spontaneous clearance (two consecutive negative HCV PCR tests spaced ≥28 days apart without treatment) or a sustained virological response (SVR; two consecutive negative HCV PCR tests spaced ≥28 days apart 12 weeks after completing interferon-based treatment). We calculated incidence rates of HCV reinfection (per 100 person-years of follow-up) and corresponding 95% CIs assuming a Poisson distribution, and used a multivariable Cox proportional hazards model to examine reinfection risk factors (age, birth cohort, sex, year of HCV diagnosis, HCV clearance type, HIV co-infection, number of mental health counselling visits, levels of material and social deprivation, and alcohol and injection drug use), and the association of opioid substitution therapy and mental health counselling with HCV reinfection among people who inject drugs (PWID). FINDINGS 5915 individuals with HCV were included in this study after clearance (3690 after spontaneous clearance and 2225 after SVR). 452 (8%) patients developed reinfection; 402 (11%) after spontaneous clearance and 50 (2%) who had achieved SVR. Individuals were followed up for a median of 5·4 years (IQR 2·9-8·7), and the median time to reinfection was 3·0 years (1·5-5·4). The overall incidence rate of reinfection was 1·27 (95% CI 1·15-1·39) per 100 person-years of follow-up over a total of 35 672 person-years, with significantly higher rates in the spontaneous clearance group (1·59, 1·44-1·76) than in the SVR group (0·48, 0·36-0·63). With the adjusted Cox proportional hazards model, we noted higher reinfection risks in the spontaneous clearance group (adjusted hazard ratio [HR] 2·71, 95% CI 2·00-3·68), individuals co-infected with HIV (2·25, 1·78-2·85), and PWID (1·53, 1·21-1·92) than with other reinfection risk factors. Among the 1604 PWID with a current history of injection drug use, opioid substitution therapy was significantly associated with a lower risk of reinfection (adjusted HR 0·73, 95% CI 0·54-0·98), as was engagement with mental health counselling services (0·71, 0·54-0·92). INTERPRETATION The incidence of HCV reinfection was higher among HIV co-infected individuals, those who spontaneously cleared HCV infection, and PWID. HCV treatment complemented with opioid substitution therapy and mental health counselling could reduce HCV reinfection risk among PWID. These findings support policies of post-clearance follow-up of PWID, and provision of harm-reduction services to minimise HCV reinfection and transmission. FUNDING The British Columbia Centre for Disease Control and the Canadian Institutes of Health Research.

The Population Level Cascade of Care for Hepatitis C in British Columbia, Canada: The BC Hepatitis Testers Cohort (BC-HTC)

Background Population-level monitoring of hepatitis C virus (HCV) infected people across the cascade of care identifies gaps in access and engagement in care and treatment. We characterized a population-level cascade of care for HCV in British Columbia (BC), Canada and identified factors associated with leakage at each stage. Methods The BC Hepatitis Testers Cohort (BC-HTC) includes 1.5 million individuals tested for HCV, HIV, reported cases of hepatitis B, and active tuberculosis in BC from 1990 to 2013 linked to medical visits, hospitalizations, cancers, prescription drugs and mortality data. We defined six HCV cascade of care stages: 1) estimated population prevalence; 2) HCV diagnosed; 3) HCV RNA tested; 4) genotyped; 5) initiated treatment; and 6) achieved sustained virologic response (SVR). Results We estimated that 73,203 people were HCV antibody positive in BC in 2012 (undiagnosed: 18,301, 25%; diagnosed: 54,902, 75%). Of these, 56%(40,656) had HCV RNA testing; 34%(26,300) were genotyped; 12%( 8532 ) had received interferon-based therapy and 7%(5197) had SVR. Males, older birth cohorts, and HBV coinfected were less likely to undergo HCV RNA testing. Among those with chronic HCV infection, 32% had received liver-related care. Retention in liver care was more likely in those with HIV, cirrhosis, and drug/alcohol use and less likely in males and HBV coinfected. Conclusions Although there are gaps in HCV RNA testing and genotyping after HCV diagnosis, the major gap in the cascade of care was low treatment initiation. People with comorbidities progressed through the cascade of testing and care but few received treatment.

Assessing Hepatitis C Burden and Treatment Effectiveness through the British Columbia Hepatitis Testers Cohort (BC-HTC): Design and Characteristics of Linked and Unlinked Participants

Background The British Columbia (BC) Hepatitis Testers Cohort (BC-HTC) was established to assess and monitor hepatitis C (HCV) epidemiology, cost of illness and treatment effectiveness in BC, Canada. In this paper, we describe the cohort construction, data linkage process, linkage yields, and comparison of the characteristics of linked and unlinked individuals. Methods The BC-HTC includes all individuals tested for HCV and/or HIV or reported as a case of HCV, hepatitis B (HBV), HIV or active tuberculosis (TB) in BC linked with the provincial health insurance client roster, medical visits, hospitalizations, drug prescriptions, the cancer registry and mortality data using unique personal health numbers. The cohort includes data since inception (1990/1992) of each database until 2012/2013 with plans for annual updates. We computed linkage rates by year and compared the characteristics of linked and unlinked individuals. Results Of 2,656,323 unique individuals available in the laboratory and surveillance data, 1,427,917(54%) were included in the final linked cohort, including about 1.15 million tested for HCV and about 1.02 million tested for HIV. The linkage rate was 86% for HCV tests, 89% for HCV cases, 95% for active TB cases, 48% for HIV tests and 36% for HIV cases. Linkage rates increased from 40% for HCV negatives and 70% for HCV positives in 1992 to ~90% after 2005. Linkage rates were lower for males, younger age at testing, and those with unknown residence location. Linkage rates for HCV testers co-infected with HIV, HBV or TB were very high (90–100%). Conclusion Linkage rates increased over time related to improvements in completeness of identifiers in laboratory, surveillance, and registry databases. Linkage rates were higher for HCV than HIV testers, those testing positive, older individuals, and females. Data from the cohort provide essential information to support the development of prevention, care and treatment initiatives for those infected with HCV.

Shift in disparities in hepatitis C treatment from interferon to DAA era: A population‐based cohort study

We evaluated the shift in the characteristics of people who received interferon‐based hepatitis C virus (HCV) treatments and those who received recently introduced direct‐acting antivirals (DAAs) in British Columbia (BC), Canada. The BC Hepatitis Testers Cohort includes 1.5 million individuals tested for HCV or HIV, or reported cases of hepatitis B and active tuberculosis in BC from 1990 to 2013 linked to medical visits, hospitalization, cancer, prescription drugs and mortality data. This analysis included all patients who filled at least one prescription for HCV treatment until 31 July 2015. HCV treatments were classified as older interferon‐based treatments including pegylated interferon/ribavirin (PegIFN/RBV) with/without boceprevir or telaprevir, DAAs with RBV or PegIFN/RBV, and newer interferon‐free DAAs. Of 11 886 people treated for HCV between 2000 and 2015, 1164 (9.8%) received interferon‐free DAAs (ledipasvir/sofosbuvir: n=1075; 92.4%), while 452 (3.8%) received a combination of DAAs and RBV or PegIFN/RBV. Compared to those receiving interferon‐based treatment, people with HIV co‐infection (adjusted odds ratio [aOR]: 2.96, 95% CI: 2.31‐3.81), cirrhosis (aOR: 1.77, 95% CI: 1.45‐2.15), decompensated cirrhosis (aOR: 1.72, 95% CI: 1.31‐2.28), diabetes (aOR: 1.30, 95% CI: 1.10‐1.54), a history of injection drug use (aOR: 1.34, 95% CI: 1.09‐1.65) and opioid substitution therapy (aOR: 1.30, 95% CI: 1.01‐1.67) were more likely to receive interferon‐free DAAs. Socio‐economically marginalized individuals were significantly less likely (most deprived vs most privileged: aOR: 0.71, 95% CI: 0.58‐0.87) to receive DAAs. In conclusion, there is a shift in prescription of new HCV treatments to previously excluded groups (eg HIV‐co‐infected), although gaps remain for the socio‐economically marginalized populations.

Seroprevalence of hepatitis C and correlates of seropositivity among men who have sex with men in Vancouver, Canada: a cross-sectional survey.

Objectives We sought to determine the prevalence of hepatitis C virus (HCV) infection among men who have sex with men (MSM) in Vancouver, Canada, and associations of risk behaviours with HCV serostatus. Methods We used data from the ManCount Study, a cross-sectional survey of MSM selected through a venue-based, time-location sampling method. Bivariate analyses and multivariate logistic regression modelling were used to determine correlates of HCV seropositivity. Bivariate analyses of participants who reported no history of injection drug use (IDU) were used to explore sexual behaviours associated with HCV seropositivity. Results HCV seroprevalence was 4.9% (56/1132). Among HCV-seropositive participants who responded to the question, 22.4% (11/49) were unaware of their HCV-seropositive status, 84.9% (45/53) reported a history of IDU and 60.7% (34/56) were HIV positive by dried blood spot. Multivariate modelling found previous IDU (adjusted OR (AOR): 26.30, 95% CI 11.15 to 62.03), receiving goods, drugs or money for sex (AOR 4.98, 95% CI 2.43 to 10.20) and current smoking (AOR 3.46, 95% CI 1.47 to 8.16) were associated with HCV seropositivity. Among MSM who reported no history of IDU, HCV seropositivity was associated with bleeding after receptive anal sex (p=0.001) and a previous diagnosis of gonorrhoea (p=0.007). Conclusions HCV seroprevalence among a sample of MSM is higher than the general population and associated with a history of IDU. Among those who did not report IDU, we found evidence that suggests sexual exposure could be the route of transmission.

Use of GetCheckedOnline, a Comprehensive Web-based Testing Service for Sexually Transmitted and Blood-Borne Infections

Background The British Columbia Centre for Disease Control implemented a comprehensive Web-based testing service GetCheckedOnline (GCO) in September 2014 in Vancouver, Canada. GCO’s objectives are to increase testing for sexually transmitted and blood-borne infections (STBBIs), reach high-prevalence populations facing testing barriers, and increase clinical STI service capacity. GCO was promoted through email invitations to provincial STI clinic clients, access codes to clients unable to access immediate clinic-based testing (deferred testers), and a campaign to gay, bisexual, and other men who have sex with men (MSM). Objective The objective of the study was to report on characteristics of GCO users, use and test outcomes (overall and by promotional strategy) during this pilot phase. Methods We used GCO program data, website metrics, and provincial STI clinic records to describe temporal trends, progression through the service pathway, and demographic, risk, and testing outcomes for individuals creating GCO accounts during the first 15 months of implementation. Results Of 868 clients creating accounts, 318 (36.6%) submitted specimens, of whom 96 (30.2%) tested more than once and 10 (3.1%) had a positive STI diagnosis. The proportion of clients submitting specimens increased steadily over the course of the pilot phase following introduction of deferred tester codes. Clients were diverse with respect to age, gender, and ethnicity, although youth and individuals of nonwhite ethnicity were underrepresented. Of the 506 clients completing risk assessments, 215 (42.5%) were MSM, 89 (17.6%) were symptomatic, 47 (9.3%) were STI contacts, 232 (45.8%) reported condomless sex, 146 (28.9%) reported ≥4 partners in the past 3 months, and 76 (15.0%) reported a recent STI. A total of 63 (12.5%) GCO clients were testing for the first time. For 868 accounts created, 337 (38.8%) were by clinic invitations (0 diagnoses), 298 (34.3%) were by deferred testers (6 diagnoses), 194 (22.4%) were by promotional campaign (3 diagnoses), and 39 (4.5%) were by other means (1 diagnosis). Conclusions Our evaluation suggests that GCO is an acceptable and feasible approach to engage individuals in testing. Use by first-time testers, repeated use, and STI diagnosis of individuals unable to access immediate clinic-based testing suggest GCO may facilitate uptake of STBBI testing and earlier diagnosis. Use by MSM and individuals reporting sexual risk suggests GCO may reach populations with a higher risk of STI. Motivation to test (eg, unable to access clinical services immediately) appears a key factor underlying GCO use. These findings identify areas for refinement of the testing model, further promotion, and future research (including understanding reasons for drop-off through the service pathway and more comprehensive evaluation of effectiveness). Increased uptake and diagnosis corresponding with expansion of the service within British Columbia will permit future evaluation of this service across varying populations and settings.

Role of primary T‐cell immunodeficiency and hepatitis B coinfection on spontaneous clearance of hepatitis C: The BC Hepatitis Testers Cohort

T‐cell host immune response against hepatitis C virus (HCV) has been suggested to play an important role in determining HCV infection outcome. However, data from human studies are not available. This study examined the effect of primary T‐cell deficiency along with other factors on the spontaneous clearance of HCV in a large population‐based cohort in British Columbia, Canada. The BC Hepatitis Testers Cohort includes all individuals tested for HCV in BC in 1990‐2013 linked with data on their medical visits, hospitalizations and prescription drugs. HCV‐positive individuals with at least one valid HCV PCR test on/after HCV diagnosis (n=46 783) were included in this study. To examine factors associated with the spontaneous clearance of HCV, multivariable logistic regression was fitted on the full sample, and Cox proportional hazards model on the HCV seroconverters. Spontaneous clearance was observed in 25.1% (n=11 737) of those tested for HCV. After adjusting for potential confounders, the odds of spontaneous clearance of HCV was lower in people with primary T‐cell immunodeficiency (adjusted odds ratio [aOR]: 0.55, 95% CI: 0.32‐0.94), and higher in females (aOR: 1.61, 95% CI: 1.54‐1.68) and in those coinfected with HBV (aOR: 2.31, 95% CI: 1.93‐2.77). Similar results were observed in HCV seroconverters except HBV coinfection was not significant. In conclusion, primary T‐cell immunodeficiency is associated with a lower spontaneous clearance of HCV while female sex and coinfection with HBV are associated with a higher spontaneous clearance.