Performance of the Cue COVID-19 point-of-care molecular test: insights from a multi-site clinic service model

The COVID-19 pandemic highlighted the critical need for rapid and accurate molecular diagnostic testing. The Cue COVID-19 Point-of-Care Test (Cue POCT) is a nucleic acid amplification test (NAAT), authorized by Health Canada and FDA as a POCT for SARS-CoV-2 detection. Cue POCT was deployed at a network of clinics in Ontario, Canada with n = 13,848 patrons tested between 17 July 2021 and 31 January 2022. The clinical performance and operational experience with Cue POCT were examined for this testing population composed mostly of asymptomatic individuals (93.7%). A head-to-head prospective clinical verification was performed between 17 July and 4 October for all POCT service clients (n = 3,037) with paired COVID-19 testing by Cue and RT-PCR. Prospective verification demonstrated a clinical sensitivity of 100% and clinical specificity of 99.4% for Cue COVID-19 POCT. The lack of false negatives and low false positive rate (0.64%), underscores the high accuracy (99.4%) of Cue POCT to provide rapid PCR quality results. Low error rates (cancellation rate of 0% and invalid rate of 0.63%) with the current software version were additionally noted. Taken together, these findings highlight the value of accurate molecular COVID-19 POCT in a distributed service delivery model to rapidly detect cases in the community with the potential to curb transmission in high-exposure settings (i.e., in-flight, congregate workplace, and social events). The insights gleaned from this operational implementation are readily transferable to future POCT diagnostic services. IMPORTANCE This manuscript reports on the findings of a large asymptomatic population who underwent surveillance COVID testing on the Cue COVID-19 Point-of-Care Test (POCT). Review of test performance of this rapid molecular POCT, as compared to gold standard RT-PCR, is valuable to many audiences, including public health, emergency testing services, employers, and the general population of consumers who are seeking a user-friendly, accurate, cost-effective, and sustainable testing model for COVID screening. The findings from this operational experience also inform future models of POCT services beyond COVID.

Household Transmission of Carbapenemase-producing Enterobacterales in Ontario, Canada

BACKGROUND

Data on household transmission of carbapenemase-producing Enterobacterales (CPE) remain limited. We studied risk of CPE household co-colonization and transmission in Ontario, Canada.

METHODS

We enrolled CPE index cases (identified via population-based surveillance from January 2015 to October 2018) and their household contacts. At months 0, 3, 6, 9, and 12, participants provided rectal and groin swabs. Swabs were cultured for CPE until September 2017, when direct polymerase chain reaction (PCR; with culture of specimens if a carbapenemase gene was detected) replaced culture. CPE risk factor data were collected by interview and combined with isolate whole-genome sequencing to determine likelihood of household transmission. Risk factors for household contact colonization were explored using a multivariable logistic regression model with generalized estimating equations.

RESULTS

Ninety-five households with 177 household contacts participated. Sixteen (9%) household contacts in 16 (17%) households were CPE-colonized. Household transmission was confirmed in 3/177 (2%) cases, probable in 2/177 (1%), possible in 9/177 (5%), and unlikely in 2/177 (1%). Household contacts were more likely to be colonized if they were the index case's spouse (odds ratio [OR], 6.17; 95% confidence interval [CI], 1.05-36.35), if their index case remained CPE-colonized at household enrollment (OR, 7.00; 95% CI, 1.92-25.49), or if they had at least 1 set of specimens processed after direct PCR was introduced (OR, 6.46; 95% CI, 1.52-27.40).

CONCLUSIONS

Nine percent of household contacts were CPE-colonized; 3% were a result of household transmission. Hospitals may consider admission screening for patients known to have CPE-colonized household contacts.

512. Healthcare-Acquired (HA) Carbapenemase-Producing Enterobacteriales (CPE) in Southern Ontario, Canada: To Whom Are We Transmitting CPE?

Background

Though CPE in Canada are mainly acquired abroad, outbreaks/transmission in Canadian hospitals have been reported. We determined the incidence of HA CPE in southern Ontario, Canada, to inform prevention and control programs.

Methods

Toronto Invasive Bacterial Diseases Network (TIBDN) has performed population-based surveillance for CPE in the Toronto area/Peel region of southern Ontario, Canada, since CPE were first identified in October 2007. Clinical microbiology laboratories report all CPE isolates to TIBDN; annual lab audits are performed. Incidence calculations used first isolates as numerator; denominator (patient-days/fiscal year for Toronto/Peel hospitals) was from the Ontario Ministry of Health and Long-Term Care.

Results

The incidence of HA CPE has risen from 0 in 2007/2008 to 0.45 and 0.28 per 100,000 patient-days for all and clinical cases, respectively, in 2017/2018 (Figure, P < 0.0001). 190/790 (24%) incident cases of CPE colonization/infection in southern Ontario from October 2007 to December 2018 were likely HA (hospitalized in Ontario with no history of hospitalization abroad/high-risk travel). Eighty (25%) were female and the median age was 73 years (IQR 57–83 years). 157 (83%) had no prior travel abroad and 33 (17%) had prior low-risk travel. 122 (64%) had their CPE identified >72 hours post-admission (of which 83 also had ≥1 other prior Ontario hospitalization); 68 (36%) had their CPE identified at admission but had recent prior Ontario hospitalization. HA cases vs. foreign acquisitions were significantly more likely K. pneumoniae (48% vs. 38%, P = 0.02) and Enterobacter spp. (20% vs. 7%, P < 0.0001) and less likely E. coli (20% vs. 48%, P < 0.0001). Genes of HA vs. foreign acquisitions were significantly more likely bla_KPC (34% vs. 12%, P < 0.0001) and bla_VIM (12% vs. 2%, P < 0.0001) and less likely bla_NDM±OXA (38% vs. 56%, P < 0.0001) and bla_OXA (13% vs. 27%, P = 0.0001). 36 (19%) HA cases had a negative CPE screen before their first positive CPE test (10/36 (28%) were on admission). The median incidence of HA CPE per 100,000 patient-days at each hospital was 0.44 (IQR 0.15–0.68) (P < 0.0001).

Conclusion

A quarter of CPE cases in southern Ontario were HA and the incidence of HA cases is increasing. Most cases were admitted to >1 Ontario hospital. Strategies to control transmission are critical.

Disclosures

All authors: No reported disclosures.

501. Risk of Infection in Persons Colonized with Carbapenemase-Producing Enterobacteriales (CPE) in Ontario, Canada

Background

We aimed to assess the risk of subsequent infection among patients colonized by CPE.

Methods

The Toronto Invasive Bacterial Diseases Network (TIBDN) has conducted population-based surveillance for CPE colonization/infection in Toronto and Peel region, Ontario, Canada, since CPE were first identified (2007). All laboratories report all CPE isolates to TIBDN. Clinical data are collected via patient interview and hospital chart review. Initially colonized patients are followed for 5y; subsequent CPE infection is defined as an episode with onset >3 days after initial detection of CPE colonization that meets National Healthcare Safety Network criteria for infection with a clinical isolate of CPE.

Results

From 2007 to 2018, 790 persons with CPE colonization/infection were identified. Among 364 cases colonized at identification, 42 (12%) subsequently had at least one clinical isolate, and 23 (6%) had an infection: 8 with bacteremia (primary or secondary), 7 UTI, 5 pneumonia, and 3 other. The median time from identification of colonization to infection was 21 days (IQR 7–38), with a probability of developing an infection of 7% at 3 months, and 18% by 3 years (figure). In 305 cases with data available to date, older persons, those admitted to the ICU, and those with current/recent invasive medical devices were more likely to develop infection (table). Gender, underlying conditions and other procedures were not associated with risk of infection. There was a trend to infections being more likely in patients colonized with K. pneumoniae (52% vs. 35%, P = 0.13).

Conclusion

The risk of subsequent infection in our cohort was 18%, with highest risk in the first 3 months; most infections occurred in patients requiring intensive care unit admission and invasive medical devices.

Disclosures

All authors: No reported disclosures.

Emergence of Carbapenemase-Producing Enterobacteriaceae, South-Central Ontario, Canada1

We analyzed population-based surveillance data from the Toronto Invasive Bacterial Diseases Network to describe carbapenemase-producing Enterobacteriaceae (CPE) infections during 2007–2015 in south-central Ontario, Canada. We reviewed patients’ medical records and travel histories, analyzed microbiologic and clinical characteristics of CPE infections, and calculated incidence. Among 291 cases identified, New Delhi metallo-β-lactamase was the predominant carbapenemase (51%). The proportion of CPE-positive patients with prior admission to a hospital in Canada who had not received healthcare abroad or traveled to high-risk areas was 13% for patients with oxacillinase-48, 24% for patients with New Delhi metallo-β-lactamase, 55% for patients with Klebsiella pneumoniae carbapenemase, and 67% for patients with Verona integron-encoded metallo-β-lactamase. Incidence of CPE infection increased, reaching 0.33 cases/100,000 population in 2015. For a substantial proportion of patients, no healthcare abroad or high-risk travel could be established, suggesting CPE acquisition in Canada. Policy and practice changes are needed to mitigate nosocomial CPE transmission in hospitals in Canada.

2165. Risk Factors for CPE Colonization in Household Contacts of CPE Colonized/Infected Patients

Background

Carbapenemase-producing Enterobacteriaceae (CPE) are a global threat. Risk of transmission of CPE in households remains poorly understood

Methods

Population-based surveillance for CPE colonization/infection is conducted in Toronto/Peel Region, Canada. In households with ≥1 consenting household contact (HC), groin, rectal swabs and urine samples are submitted every 3 months for both IC and HC until the IC has three consecutive negative swab sets. Swabs/urines are incubated overnight in BHI, direct PCR for carbapenemase genes is performed; specimens positive for PCR are then cultured.

Results

Eighty-five households and 150 HC have been enrolled. Most common species/gene combinations in IC are: E. coli/NDM (33), E. coli/OXA48 (15), Klebsiella spp./NDM (11). HCs have a median of eight swabs (range 2–14). 12 (8%) HCs were colonized with CPE (median 1.5 pos samples, range 1–8). IC and HC had same gene in 11(92%) cases, and same species/gene in seven (58%) cases. NDM+OXA48 ICs were more likely to have CPE colonized HC, see table. CPE colonized HC were older, more likely to be the IC’s spouse (OR 32, 95% CI 4–260), and more likely to have travelled outside Canada (OR 9.7, 95% CI 1.2–78).

Conclusion

HC colonization with CPE is uncommon, but not rare, and may be associated with either household transmission, or co-exposure of HC and IC via travel. Spouses are most often colonized.

Disclosures

S. Poutanen, MERCK: Scientific Advisor, Speaker honorarium; COPAN: Speaker(but not part of a bureau), Travel reimbursement; Accelerate Diagnostics: Investigator, Research support; Bio-Rad: Investigator, Research support; bioMérieux: Investigator, Research support.

1205. Emergence of Carbapenemase Producing Enterobacteriaceae in South Central Ontario, Canada

Background

The spread of CPE is an increasing global threat to patient safety. We describe the introduction and evolution of CPE in south-central Ontario, Canada.

Methods

The Toronto Invasive Bacterial Diseases Network has performed population based surveillance for CPE in metropolitan Toronto and Peel region from first identified isolates in 2007. All laboratories test/refer all carbapenem non-susceptible Enterobacterial isolates for PCR testing for carbapenemases. Demographic and medical data and travel history are collected from chart review and patient/physician interview.

Results

Since 2007, 659 patients have been identified as colonized/infected with CPE; 362, 57%) have at least one clinical isolate. Annual incidence has increased from 0 in 2006 to 1.3 per 100,000 in 2016/17 (Figure 1). First bacteremia occurred in 2010, the incidence in 2017 was 0.14 per 100,000 population. 388 (59%) patients were male, median age was 70 years (range 3 months–100 years). Most common genes among first isolates were NDM (306, 46%), OX48 (149, 23%), KPC (122, 19%). Most common species were K. pneumoniae (268, 41%) and E. coli (259, 39%). Over time, second species/same gene were identified in 113 (16%) patients. In addition, 34/xxx patients with isolates with NDM and/or OXA-48 subsequently had a second isolate with a different gene/gene combination. Of 518 patients whose travel and hospitalization history are available, patients with VIM were less likely than other patients to have a foreign hospitalization or travel history (9/28 vs. 341/490, P < 0.0001). Patients with KPC were more likely to have a hospitalization history outside Canada and the Indian subcontinent (25/70, 36%), in Canada (47/164,29%) than to have no hospitalization in the last year (13/93, 14%), or a history of hospitalization in the Indian subcontinent (2/191, 1%) (P < 0.001). The number of incident patients with different hospitalization and travel history over time is shown in Figure 2.

Conclusion

CPE is increasingly recognized in southern Ontario, both in patients with a history of exposure in healthcare in other countries, and to healthcare in Canada. Intensification of control programs is urgently needed.

Disclosures

S. Poutanen, MERCK: Scientific Advisor, Speaker honorarium. COPAN: Speaker(but not part of a bureau), Travel reimbursement. Accelerate Diagnostics: Investigator, Research support. Bio-Rad: Investigator, Research support. bioMérieux: Investigator, Research support.

Case-control study of household contacts to examine immunological protection from Bordetella pertussis transmission - study protocol

BACKGROUND

There is mounting evidence that the recent resurgence of pertussis in many countries is in part related to the acellular vaccine, which has been administered in Canada since 1997. This vaccine elicits a different cell-mediated immune response than the previously used whole-cell vaccine, and its effectiveness wanes over time. The aim of this study is to understand the immunological, demographic and clinical factors that mediate protection from pertussis on exposure.

METHODS

This is a household case-control study protocol. Following notification of an index case in a household, a study team will conduct a home visit to collect data and biological specimens. The study team will return to the household 8 weeks from the onset of illness in the index case. The Th1, Th2 and Th17 responses, cytokine expression, IgG subclass, blood cell counts and presence of Bordetella pertussis will be determined. We will use laboratory and statistical analyses to determine immunological differences between contacts who are infected with B. pertussis and contacts who remain healthy, and to determine which clinical and demographic covariates are associated with a reduced risk of infection.

INTERPRETATION

The results of this study will be essential for understanding the immune response required for protection from infection with B. pertussis and will contribute to our understanding of the shortcomings of the current vaccine.

Association of HPV infection and clearance with cervicovaginal immunology and the vaginal microbiota

Cervical human papillomavirus (HPV) infection may increase HIV risk. Since other genital infections enhance HIV susceptibility by inducing inflammation, we assessed the impact of HPV infection and clearance on genital immunology and the cervico-vaginal microbiome. Genital samples were collected from 65 women for HPV testing, immune studies and microbiota assessment; repeat HPV testing was performed after 6 months. All participants were HIV-uninfected and free of bacterial STIs. Cytobrush-derived T cell and dendritic cell subsets were assessed by multiparameter flow cytometry. Undiluted cervico-vaginal secretions were used to determine cytokine levels by multiplex ELISA, and to assess bacterial community composition and structure by 16S rRNA gene sequence analysis. Neither HPV infection nor clearance were associated with broad differences in cervical T cell subsets or cytokines, although HPV clearance was associated with increased Langerhans cells and HPV infection with elevated IP-10 and MIG. Individuals with HPV more frequently had a high diversity cervico-vaginal microbiome (community state type IV) and were less likely to have an L. gasseri predominant microbiome. In summary, HPV infection and/or subsequent clearance was not associated with inflammation or altered cervical T cell subsets, but associations with increased Langerhans cells and the composition of the vaginal microbiome warrant further exploration.

Randomized Intervention of Self-Collected Sampling for Human Papillomavirus Testing in Under-Screened Rural Women: Uptake of Screening and Acceptability

BACKGROUND

Our aim was to determine if cervical cancer screening uptake would increase among under-screened women living in rural Ontario, Canada, if at-home self-collected sampling for human papillomavirus (HPV) testing was offered as a primary cervical cancer screening modality, compared to invited papanicolaou (Pap) testing or routine opportunistic screening.

METHODS

Women 30-70 years of age who were overdue for cervical cancer screening were randomized to receive (1) an at-home self-collected HPV kit, (2) a reminder invitation for Pap testing, or (3) standard of care opportunistic screening. The first two arms were also asked demographic and screening history questions. Women randomized to arm 1 were asked about acceptability.

RESULTS

In total, 818 eligible women were identified in a small rural community in Southwestern Ontario: 335 received a self-collected HPV testing kit, 331 received a reminder letter, and 152 received standard of care. In the HPV self-collection arm, 21% (70/335) returned the sample and questionnaire and 11% (37/335) opted to undergo Pap testing. In total, 32% from the HPV self-collection arm, 15% (51/331) from the Pap invitation arm, and 8.5% (13/152) with standard of care were screened. Women receiving the self-collected HPV kit were 3.7 (95% confidence interval 2.2-6.4) times more likely to undergo screening compared to the standard of care arm. In the HPV self-sampling arm, 80% (56/70) said they would be very likely to choose self-collected sampling in the future.

CONCLUSIONS

Providing self-collected sampling for HPV testing was more effective than sending reminder letters to increase screening coverage in under-screened women.

Integrated quantum dot barcode smartphone optical device for wireless multiplexed diagnosis of infected patients

Inorganic nanoparticles are ideal precursors for engineering barcodes for rapidly detecting diseases. Despite advances in the chemical design of these barcodes, they have not advanced to clinical use because they lack sensitivity and are not cost-effective due to requirement of a large read-out system. Here we combined recent advances in quantum dot barcode technology with smartphones and isothermal amplification to engineer a simple and low-cost chip-based wireless multiplex diagnostic device. We characterized the analytical performance of this device and demonstrated that the device is capable of detecting down to 1000 viral genetic copies per milliliter, and this enabled the diagnosis of patients infected with HIV or hepatitis B. More importantly, the barcoding enabled us to detect multiple infectious pathogens simultaneously, in a single test, in less than 1 h. This multiplexing capability of the device enables the diagnosis of infections that are difficult to differentiate clinically due to common symptoms such as a fever or rash. The integration of quantum dot barcoding technology with a smartphone reader provides a capacity for global surveillance of infectious diseases and the potential to accelerate knowledge exchange transfer of emerging or exigent disease threats with healthcare and military organizations in real time.

Impact of asymptomatic herpes simplex virus type 2 infection on mucosal homing and immune cell subsets in the blood and female genital tract

HSV-2 infection is common and generally asymptomatic, but it is associated with increased HIV susceptibility and disease progression. This may relate to herpes-mediated changes in genital and systemic immunology. Cervical cytobrushes and blood were collected from HIV-uninfected African/Caribbean women in Toronto, and immune cell subsets were enumerated blindly by flow cytometry. Immune differences between groups were assessed by univariate analysis and confirmed using a multivariate model. Study participants consisted of 46 women, of whom 54% were infected with HSV-2. T cell activation and expression of the mucosal homing integrin α4β7 (19.60 versus 8.76%; p < 0.001) were increased in the blood of HSV-2-infected women. Furthermore, expression of α4β7 on blood T cells correlated with increased numbers of activated (coexpressing CD38/HLA-DR; p = 0.004) and CCR5(+) (p = 0.005) cervical CD4(+) T cells. HSV-2-infected women exhibited an increase in the number of cervical CD4(+) T cells (715 versus 262 cells/cytobrush; p = 0.016), as well as an increase in the number and proportion of cervical CD4(+) T cells that expressed CCR5(+) (406 versus 131 cells, p = 0.001; and 50.70 versus 34.90%, p = 0.004) and were activated (112 versus 13 cells, p < 0.001; and 9.84 versus 4.86%, p = 0.009). Mannose receptor expression also was increased on cervical dendritic cell subsets. In conclusion, asymptomatic HSV-2 infection was associated with significant systemic and genital immune changes, including increased immune activation and systemic α4β7 expression; correlation of the latter with highly HIV-susceptible CD4(+) T cell subsets in the cervix may provide a mechanism for the increased HIV susceptibility observed in asymptomatic HSV-2-infected women.

Ano-genital human papillomavirus type 97 infection is detected in Canadian men but not women at risk or infected with the human immunodeficiency virus

Background

Human papillomavirus type 97 (HPV97) DNA was detected in nearly 5% of anal samples collected from HIV-seropositive men living in Montreal, Canada. The rate of detection of HPV97 in the genital tract of Canadian women is unknown. Whether HPV97 is a local epidemic in HIV-seropositive men living in Montreal is also unknown. The prevalence of human papillomavirus type 97 (HPV97) was assessed in cervicovaginal cells from women living in Canada and in anal samples from HIV-seropositive men living in Toronto.

Findings

Cervicovaginal lavages collected from 904 women (678 HIV-seropositive, 226 HIV-seronegative) women living in Canada and anal cells collected from 123 HIV-seropositive men living in Toronto were tested for the presence of HPV97 with PCR. HPV97-positive samples were further tested by PCR-sequencing for molecular variant analysis to assess if all HPV97-positive men were infected with the same strain. All cervicovaginal samples were negative for HPV97. HPV97 was detected in anal samples from 6 HIV-seropositive men (4.9%, 95% confidence interval 2.0-10.5%), of whom five had high-grade and one had low-grade anal intraepithelial neoplasia, in addition to 2 to 8 HPV genital genotypes per sample. Four HPV97 variants were defined by four variation sites in the viral control region.

Conclusion

These findings indicate that HPV97 infects in the anal canal of HIV-seropositive men but is not detected in the genital tract of women.

Community-acquired respiratory viruses and co-infection among patients of Ontario sentinel practices, April 2009 to February 2010

Please cite this paper as: Peci et al. (2012) Community‐acquired respiratory viruses and co‐infection among patients of Ontario Sentinel practices, April 2009 to February 2010. Influenza and Other Respiratory Viruses 7(4), 559–566.

Background  Respiratory viruses are known to cocirculate but this has not been described in detail during an influenza pandemic.

Objectives  To describe respiratory viruses, including co‐infection and associated attributes such as age, sex or comorbidity, in patients presenting with influenza‐like illness to a community sentinel network, during the pandemic A(H1N1)pdm09 in Ontario, Canada.

Methods  Respiratory samples and epidemiologic details were collected from 1018 patients with influenza‐like illness as part of respiratory virus surveillance and a multiprovincial case–control study of influenza vaccine effectiveness.

Results  At least one virus was detected in 668 (65·6%) of 1018 samples; 512 (50·3%) had single infections and 156 (15·3%) co‐infections. Of single infections, the most common viruses were influenza A in 304 (59·4%) samples of which 275 (90·5%) were influenza A(H1N1)pdm09, and enterovirus/rhinovirus in 149 (29·1%) samples. The most common co‐infections were influenza A and respiratory syncytial virus B, and influenza A and enterovirus/rhinovirus. In multinomial logistic regression analyses adjusted for age, sex, comorbidity, and timeliness of sample collection, single infection was less often detected in the elderly and co‐infection more often in patients <30 years of age. Co‐infection, but not single infection, was more likely detected in patients who had a sample collected within 2 days of symptom onset as compared to 3–7 days.

Conclusions  Respiratory viral co‐infections are commonly detected when using molecular techniques. Early sample collection increases likelihood of detection of co‐infection. Further studies are needed to better understand the clinical significance of viral co‐infection.

Humoral and cell-mediated immunity to pandemic H1N1 influenza in a Canadian cohort one year post-pandemic: implications for vaccination

We evaluated a cohort of Canadian donors for T cell and antibody responses against influenza A/California/7/2009 (pH1N1) at 8-10 months after the 2nd pandemic wave by flow cytometry and microneutralization assays. Memory CD8 T cell responses to pH1N1 were detectable in 58% (61/105) of donors. These responses were largely due to cross-reactive CD8 T cell epitopes as, for those donors tested, similar recall responses were obtained to A/California 2009 and A/PR8 1934 H1N1 Hviruses. Longitudinal analysis of a single infected individual showed only a small and transient increase in neutralizing antibody levels, but a robust CD8 T cell response that rose rapidly post symptom onset, peaking at 3 weeks, followed by a gradual decline to the baseline levels seen in a seroprevalence cohort post-pandemic. The magnitude of the influenza-specific CD8 T cell memory response at one year post-pandemic was similar in cases and controls as well as in vaccinated and unvaccinated donors, suggesting that any T cell boosting from infection was transient. Pandemic H1-specific antibodies were only detectable in approximately half of vaccinated donors. However, those who were vaccinated within a few months following infection had the highest persisting antibody titers, suggesting that vaccination shortly after influenza infection can boost or sustain antibody levels. For the most part the circulating influenza-specific T cell and serum antibody levels in the population at one year post-pandemic were not different between cases and controls, suggesting that natural infection does not lead to higher long term T cell and antibody responses in donors with pre-existing immunity to influenza. However, based on the responses of one longitudinal donor, it is possible for a small population of pre-existing cross-reactive memory CD8 T cells to expand rapidly following infection and this response may aid in viral clearance and contribute to a lessening of disease severity.

Seroprevalence of pandemic influenza H1N1 in Ontario from January 2009-May 2010

BACKGROUND

We designed a seroprevalence study using multiple testing assays and population sources to estimate the community seroprevalence of pH1N1/09 and risk factors for infection before the outbreak was recognized and throughout the pandemic to the end of 2009/10 influenza season.

METHODS

Residual serum specimens from five time points (between 01/2009 and 05/2010) and samples from two time points from a prospectively recruited cohort were included. The distribution of risk factors was explored in multivariate adjusted analyses using logistic regression among the cohort. Antibody levels were measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays.

RESULTS

Residual sera from 3375 patients and 1024 prospectively recruited cohort participants were analyzed. Pre-pandemic seroprevalence ranged from 2%-12% across age groups. Overall seropositivity ranged from 10%-19% post-first wave and 32%-41% by the end of the 2009/10 influenza season. Seroprevalence and risk factors differed between MN and HAI assays, particularly in older age groups and between waves. Following the H1N1 vaccination program, higher GMT were noted among vaccinated individuals. Overall, 20-30% of the population was estimated to be infected.

CONCLUSIONS

Combining population sources of sera across five time points with prospectively collected epidemiological information yielded a complete description of the evolution of pH1N1 infection.

Analytical and clinical validation of novel real-time reverse transcriptase-polymerase chain reaction assays for the clinical detection of swine-origin H1N1 influenza viruses

During the early stages of the 2009/2010 swine-origin H1N1 influenza A (S-OIV H1N1 FluA) outbreak, the development and validation of sensitive and specific detection methods were a priority for rapid and accurate diagnosis. Between May and June 2009, 2 real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) assays targeting the hemagglutinin and neuraminidase genes of the S-OIV H1N1 FluA virus were developed. These assays are highly specific, showing no cross-reactivity against a panel of respiratory viruses and can differentiate S-OIV H1N1 from seasonal FluA viruses. Analytical sensitivities of the 2 assays were found to be 10(-1) tissue culture infectious dose, 50%/ml. Clinical testing showed 99.2% sensitivity and 94.6-98.1% specificity. A large prospective analysis showed that 94.8-95.5% of S-OIV positive specimens were negative by seasonal H1/H3 subtyping. The large-scale validation data presented in this report indicate that these novel assays provide an accurate and efficient method for the rapid detection of S-OIV H1N1 FluA viruses.

Cervical HIV-specific IgA in a population of commercial sex workers correlates with repeated exposure but not resistance to HIV

We conducted a comprehensive cross-sectional analysis of total and HIV-specific cervical antibody levels in HIV-1-resistant, uninfected, and infected women in order to examine the role of HIV-specific antibody responses in the female genital tract and examine the effect on antibody levels of various epidemiologic factors in this population. Cervical lavages were collected from 272 subjects of the Pumwani commercial sex worker cohort. Total and HIV-specific genital tract IgA and IgG levels were measured using an ELISA and correlated with behavioral and demographic factors. No significant difference was seen between cervical HIV-specific IgA levels in infected, uninfected, and resistant individuals, nor were any correlations between cervical HIV-specific IgA and neutralization capacity or viral shedding seen. We did, however, note increased HIV-specific IgA in HIV-negative women with four or more clients per day, and decreased HIV-specific IgA in both long-term nonprogressors and long-term survivors. These results show that there is not a strong cohort-wide correlation between HIV-specific cervical IgA levels and resistance to infection by HIV-1 as previously believed, but there is a correlation between exposure to HIV and HIV-specific cervical IgA. Our findings do not preclude the possibility that functional differences in the cervical IgA of HEPS women may play a role in resistance, but argue that HIV-specific responses may not be a universal protective factor. They also indicate that resistance to HIV is a complex condition related to more factors than exposure. Further studies of correlates of immune protection in these individuals would be beneficial to the field.

The genital tract immune milieu: an important determinant of HIV susceptibility and secondary transmission

HIV is generally sexually acquired across the genital or rectal mucosa after exposure to the genital secretions of an HIV-infected partner. Most exposures to HIV do not result in infection, likely due to protection afforded by an intact mucosal epithelium, as well as by innate and adaptive mucosal immune factors present in the genital tract. Another important mucosal determinant of transmission may be the number and activation status of potential HIV target cells, including CCR5/CD4+ T cells and DC-SIGN+ dendritic cells. The simultaneous presence of other genital infections, including classical sexually transmitted infections (STIs), can enhance HIV susceptibility either by breaching the epithelial barrier, recruiting HIV target cells to the genital tract, or by generating a pro-inflammatory local immune milieu. In HIV-infected individuals, genital co-infections increase HIV levels in the genital secretions, thereby increasing secondary sexual transmission. Co-infections that act as important HIV cofactors include human cytomegalovirus (CMV), Herpes simplex virus type 2 (HSV2), Neisseria gonorrhoeae and many others. Strategies focused on genital co-infections, such as vaccines, microbicides and suppressive therapy, are feasible in the short term and have the potential to curb the pandemic.

Myostatin signals through a transforming growth factor beta-like signaling pathway to block adipogenesis

Myostatin, a transforming growth factor beta (TGF-beta) family member, is a potent negative regulator of skeletal muscle growth. In this study we characterized the myostatin signal transduction pathway and examined its effect on bone morphogenetic protein (BMP)-induced adipogenesis. While both BMP7 and BMP2 activated transcription from the BMP-responsive I-BRE-Lux reporter and induced adipogenic differentiation, myostatin inhibited BMP7- but not BMP2-mediated responses. To dissect the molecular mechanism of this antagonism, we characterized the myostatin signal transduction pathway. We showed that myostatin binds the type II Ser/Thr kinase receptor. ActRIIB, and then partners with a type I receptor, either activin receptor-like kinase 4 (ALK4 or ActRIB) or ALK5 (TbetaRI), to induce phosphorylation of Smad2/Smad3 and activate a TGF-beta-like signaling pathway. We demonstrated that myostatin prevents BMP7 but not BMP2 binding to its receptors and that BMP7-induced heteromeric receptor complex formation is blocked by competition for the common type II receptor, ActRIIB. Thus, our results reveal a strikingly specific antagonism of BMP7-mediated processes by myostatin and suggest that myostatin is an important regulator of adipogenesis.

The FAD-PAS domain as a sensor for behavioral responses in Escherichia coli

Aer, the aerotaxis receptor in Escherichia coli, is a member of a novel class of flavoproteins that act as redox sensors. The internal energy of the cell is coupled to the redox state of the electron transport system, and this status is sensed by Aer(FAD). This is a more versatile sensory response system than if E. coli sensed oxygen per se. Energy-depleting conditions that decrease electron transport also alter the redox state of the electron transport system. Aer responds by sending a signal to the flagellar motor to change direction. The output of other sensory systems that utilize redox sensors is more commonly transcriptional regulation than a behavioral response. Analysis in silico showed Aer to be part of a superfamily of PAS domain proteins that sense the intracellular environment. In Aer, FAD binds to the PAS domain. By using site-specific mutagenesis, residues critical for FAD binding and sensory transduction were identified in the PAS domain. The PAS domain appears to interact with a linker region in the C-terminus. The linker region is a member of a HAMP domain family, which has signal transduction roles in other systems.

The Aer protein and the serine chemoreceptor Tsr independently sense intracellular energy levels and transduce oxygen, redox, and energy signals for Escherichia coli behavior

We identified a protein, Aer, as a signal transducer that senses intracellular energy levels rather than the external environment and that transduces signals for aerotaxis (taxis to oxygen) and other energy-dependent behavioral responses in Escherichia coli. Domains in Aer are similar to the signaling domain in chemotaxis receptors and the putative oxygen-sensing domain of some transcriptional activators. A putative FAD-binding site in the N-terminal domain of Aer shares a consensus sequence with the NifL, Bat, and Wc-1 signal-transducing proteins that regulate gene expression in response to redox changes, oxygen, and blue light, respectively. A double mutant deficient in aer and tsr, which codes for the serine chemoreceptor, was negative for aerotaxis, redox taxis, and glycerol taxis, each of which requires the proton motive force and/or electron transport system for signaling. We propose that Aer and Tsr sense the proton motive force or cellular redox state and thereby integrate diverse signals that guide E. coli to environments where maximal energy is available for growth.