M McClure

Transmitted drug-resistant HIV-1 in primary HIV-1 infection; incidence, evolution and impact on response to antiretroviral therapy

The aim of the study was to determine the incidence and persistence of transmitted drug‐resistant HIV‐1 in an incident cohort between 2000 and 2004, and to investigate the impact of transmitted drug‐resistant HIV‐1 on the response to antiretroviral therapy (ART).

O05.2 Measuring Syphilis: Quantitative PCR Can Be Used to Monitor Treatment Response

Background The humoral response to Treponema pallidum ( T. pallidum), which causes syphilis, is divided into ‘non-specific’ anti-lipid and specific anti-treponemal protein antibodies. A four-fold reduction in anti-lipid antibodies is used to diagnose cure, which can take six or more months. Quantitative PCR (qPCR) can measure T. pallidum DNA copies in blood and ulcer samples. Bacteraemia is more common and of higher load in early disease. We present a pilot study monitoring the early treatment response in patients with infectious syphilis by qPCR. Methods Patients with symptomatic primary or secondary disease were admitted to hospital and following baseline sampling were treated with 2.4 M units of benzathine penicillin. Whole blood was collected into EDTA and Tempus RNA preservation tubes and the ulcer sampled using a philtre paper strip every four hours for T. pallidum DNA ( tpp047 gene) and RNA ( 16S rRNA) quantification. Sampling ended when two consecutive PCRs were negative. Standard serological follow-up was performed. Results Three men were recruited (two secondary, one primary). All were homosexual and two were HIV-1 infected. Blood DNA quantification and clearance: A mean peak-level of 1611(range 1212) tpp047 copies/ml was detected and mean half-life for clearance (t½ clearance) was 7.89 hours (range 5.34). Blood RNA: Mean peak-level 8829(range 20366) 16SrRNA copies/ml blood; (t½ clearance) 5.24 hours (range 0.78). Ulcer DNA 1.14 × 105 copies/strip and RNA 4.35 × 107 copies/strip with a t½ (clearance) of 1.67 and 3.76 hours, respectively. T. pallidum nucleic acids were undetectable in all samples after 56 hours. All patients had serology consistent with disease stage at baseline and cure at one month. Conclusions T. pallidumqPCR presents a novel and quick way of monitoring early syphilis treatment efficacy. Both DNA and RNA may be suitable targets to measure bacterial clearance from blood and ulcer exudates. Ulcers may be non-infectious as soon as 56 hours post-treatment.

P3.021 Seroepidemiology to Evaluate Chlamydia Screening Programmes: Results from Two Surveys of Pgp3 Antibody in Residual Stored Serum Samples in England

Background There have been substantial increases in chlamydia screening among young adults in England since the introduction of the National Chlamydia Screening Programme in 2003. The impact of the programme on the incidence of chlamydia in practise is unknown. We used stored sera to investigate trends in seroprevalence for chlamydia. Methods Unlinked, anonymous, residual serum specimens were obtained from: (1) an approximate population-based collection, the Health Protection Agency Seroepidemiology Unit (SEU), consisting of sera submitted to laboratories in England for routine investigations (n = 4,732); (2) a higher STI-risk collection, the Unlinked Anonymous Survey of Genitourinary Medicine Clinic Attendees (GUMAnon), consisting of sera from women tested for syphilis in two GUM clinics (n = 5,431). Specimens from women aged 17–24, between 1993 and 2010 (SEU) and women aged < 20–34, between 1998 and 2009 (GUMAnon) were tested using an indirect IgG ELISA for chlamydia Pgp3 antibody. Results In the SEU samples, seroprevalence amongst 17–24 year-olds increased between 1993 and 2002 (from 17% to 21%), and decreased between 2007 and 2010 (20% to 15%). The biggest decrease was among 20–21 year-olds (21% to 9%). In the GUMAnon samples, seroprevalence was consistently higher and declined in < 20 year olds between 2002 and 2009 (48% to 38%); no notable changes were seen in older ages. Seroprevalence was generally higher among older age groups within each collection. Conclusions Pgp3 seroprevalence reflected known epidemiology of chlamydia infection with regard to increases between 1993–2002, by age and by risk. Given this, the decline in seroprevalence in recent years, particularly in younger age groups, suggests that the increased chlamydia screening during these years is changing the epidemiology of Pgp3 antibody-inducing chlamydia infection. Further exploration of Pgp3 seroprevalence as a tool for evaluation of chlamydia screening programmes is warranted.

O21.6 A Tale of Two Cities: Treponema Pallidum Macrolide Resistance in Colombo (Sri Lanka) and London (United Kingdom)

Background The bacterium Treponema pallidum ( T. pallidum) causes syphilis. Penicillin is effective treatment, but azithromycin (a macrolide) is a single-dose oral alternative for those with allergy. Unfortunately, macrolide resistance secondary to one of two 23S ribosomal RNA (rRNA) point mutations (A2058G and A2059G) is now wide-spread. Molecular strain-typing suggests that epidemics and macrolide resistance are unlikely the spread of single clones. We present typing and macrolide resistance data from two geographically distinct populations: Colombo, Sri Lanka and London, UK. Methods Cross-sectional studies were conducted at the Colombo District STD clinics and St Mary’s Hospital, London. Ulcer exudate and/or blood were collected from patients with microbiologically confirmed syphilis. Presence of T. pallidum DNA ( tpp047 gene) was confirmed with PCR. Next, using published techniques, the 23SrRNAgene was PCR-amplified for a point-mutation assay and tpp0548, arp and tprE,G& Jamplicons were used for strain-typing. Results Sri Lanka: 24 T. pallidum PCR-positive samples were collected. Patients were men (45.9% MSM) and 91.6% Sinhalese with a mean age of 28 (range 29). None were HIV-1 infected. Two strain types were discovered (14b/f and 13b/f), neither harbouring macrolide resistance. London: 43 men were recruited, 18 in 2006–8 and 25 in 2011–12. Mean age was 37.5 (range 43); 95.2% were MSM and 62.8% were HIV-1 infected. Half (22/43) were white British. A total of 5 full and 14 partial strain types were identified, of which 6 were unique. Macrolide resistance increased from 66.7%(12/18) in 2006–8 to 80%(20/25) in 2011–12. Conclusion Colombo T. pallidumstrains have limited diversity with no macrolide resistance. London strains are more varied and increasingly macrolide-resistant. Ethnic diversity in London exceeds Colombo’s and may explain increased strain diversity. In contrast to Sri Lanka, azithromycin is widely used to treat Chlamydia and non-specific urethritis in the UK thus selection pressure may be driving macrolide resistance.

P3.018 Development of a C. Trachomatis-Specific Competitive Pgp3 ELISA

Background Chlamydia trachomatis (CT) DNA testing of genital samples principally from symptomatic persons provides information about active infection only, and is unlikely to represent true prevalence of current and past infection in the population. Serological tests applied to serum collections that are more representative of the general population can help understanding the pattern of the infection. We previously described an indirect immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) based on the CT-specific antigen Pgp3. Sensitivity and specificity were determined using ROC curve analysis of data from 356 sera from CT-infected patients and 722 paediatric sera. The assay works particularly well in women, with a greater sensitivity (74%) than commercial assays (60%), and is suitable for use in seroprevalence studies. However, there is a need to confirm the specificity of samples reactive in the indirect Pgp3 ELISA and, to this end, we have developed a competitive Pgp3 ELISA. Methods Purified IgG from human sera containing high titre antibody to CT was labelled with HRP and, by optimising conditions and using chequerboard titrations, an assay developed where test sera compete with labelled IgG for epitopes on the Pgp3 protein. Results The competitive assay was optimised, then 89 sera from our CT-infected patient cohort (patients having had at least one positive CT NAAT result at least one month previously) and 91 paediatric sera were assayed by both the indirect and competitive Pgp3 ELISAs. Results by these two assays were concordant. Conclusion A competitive ELISA based on the CT-specific Pgp3 protein has been developed, which confirms the specificity of the indirect Pgp3 ELISA.

O1-S11.03 How many infections are averted by behaviour change after early HIV diagnosis & counselling of MSM? Estimates from a stochastic individual-based model

Background A recent paper (Fox et al HIV Medicine 2009) reported that MSM in the UK significantly reduced their transmission-risk behaviour following HIV diagnosis and suggested that this could be effective in averting transmission during the highly-infectious primary infection stage. However, cost-effectiveness analysis is required to inform policy-making. To assess the effectiveness of early HIV diagnosis in MSM as a prevention strategy we quantified its potential impact in terms of transmission HIV events averted. Methods We developed an individual-based stochastic transmission model to calculate the number of HIV-transmission events expected to occur from a cohort of recently-diagnosed MSM with and without the changes in behaviour that occurred post-diagnosis and counselling. The model incorporates different types of sex-act, patterns of condom use, and distinguishes between regular and casual partners. Results In the 12 weeks post-diagnosis, for a large majority of respondents there was a reduction in the expected number of casual partners who would be infected: 76% of participants eliminated risk of onward transmission entirely. However, a small proportion still presented a transmission risk. Overall, reductions in HIV transmission risk behaviour post-diagnosis would have reduced estimated secondary transmission during primary HIV infection (PHI) from been 33 (23–37) to 12 (6–14)—a reduction of 62% (32%–83%). Diagnosis after PHI produces a more modest reduction in transmission by missing the high-infectivity period. Conclusions Diagnosis of PHI can produce a large proportionate reduction in HIV-transmission events by reducing transmission-risk behaviour. Due to the high infectivity but short duration of primary infection, even short-term behaviour change can significantly reduce transmission. Later diagnosis is less effective, whilst early diagnosis requires frequent or highly-targeted testing. Whilst further work is required to determine the costs of different testing strategies, our quantification of the number of infections averted is an essential component of an assessment of the cost-effectiveness of strategies to increase early diagnoses of HIV infection.