Comparative multi-assay evaluation of Determine™ HIV-1/2 Ag/Ab Combo rapid diagnostic tests in acute and chronic HIV infection.

In resource-limited or point-of-care settings, rapid diagnostic tests (RDTs), that aim to simultaneously detect HIV antibodies and p24 capsid (p24CA) antigen with high sensitivity, can pose important alternatives to screen for early infections. We evaluated the performance of the antibody and antigen components of the old and novel version of the Determine™ HIV-1/2 Ag/Ab Combo RDTs in parallel to quantifications in a fourth-generation antigen/antibody immunoassay (4G-EIA), p24CA antigen immunoassay (p24CA-EIA), immunoblots, and nucleic acid quantification. We included plasma samples of acute, treatment-naïve HIV-1 infections (Fiebig stages I-VI, subtypes A1, B, C, F, CRF02_AG, CRF02_AE, URF) or chronic HIV-1 and HIV-2 infections. The tests' antigen component was evaluated also for a panel of subtype B HIV-1 transmitted/founder (T/F) viruses, HIV-2 strains and HIV-2 primary isolates. Furthermore, we assessed the analytical sensitivity of the RDTs to detect p24CA using a highly purified HIV-1NL4-3 p24CA standard. We found that 77% of plasma samples from acutely infected, immunoblot-negative HIV-1 patients in Fiebig stages II-III were identified by the new RDT, while only 25% scored positive in the old RDT. Both RDTs reacted to all samples from chronically HIV-1-infected and acutely HIV-1-infected patients with positive immunoblots. All specimens from chronically infected HIV-2 patients scored positive in the new RDT. Of note, the sensitivity of the RDTs to detect recombinant p24CA from a subtype B virus ranged between 50 and 200 pg/mL, mirrored also by the detection of HIV-1 T/F viruses only at antigen concentrations tenfold higher than suggested by the manufacturer. The RTD failed to recognize any of the HIV-2 viruses tested. Our results indicate that the new version of the Determine™ HIV-1/2 Ag/Ab Combo displays an increased sensitivity to detect HIV-1 p24CA-positive, immunoblot-negative plasma samples compared to the precursor version. The sensitivity of 4G-EIA and p24CA-EIA to detect the major structural HIV antigen, and thus to diagnose acute infections prior to seroconversion, is still superior.

Prevalence of Chlamydia trachomatis infection in women, heterosexual men and MSM visiting HIV counselling institutions in North Rhine-Westphalia, Germany - should Chlamydia testing be scaled up?

BACKGROUND: Patients asking for a free anonymous HIV test may have contracted other sexually transmitted infections (STIs) such as Chlamydia trachomatis, yet Chlamydia prevalence in that population is unknown. This study aimed to assess the prevalence and factors associated with Chlamydia infection in patients seeking HIV testing at local public health authorities (LPHA) in order to evaluate whether Chlamydia testing should be routinely offered to them. METHODS: We conducted a cross-sectional study among patients (≥18 years) attending 18 LPHA in North Rhine-Westphalia from November 2012 to September 2013. LPHA collected information on participants' socio-demographic characteristics, sexual and HIV testing behaviours, previous STI history and clinical symptoms. Self-collected vaginal swabs and urine (men) were analysed by Transcription-Mediated Amplification. We assessed overall and age-stratified Chlamydia prevalence and 95 % confidence intervals (95 % CI). Using univariate and multivariable binomial regression, we estimated adjusted prevalence ratios (aPR) to identify factors associated with Chlamydia infection. RESULTS: The study population comprised 1144 (40.5 %) women, 1134 (40.1 %) heterosexual men and 549 (19.4 %) men who have sex with men (MSM); median age was 30 years. Chlamydia prevalence was 5.3 % (95 % CI: 4.1-6.8 %) among women, 3.2 % (95 % CI: 2.2-4.4) in heterosexual men and 3.5 % (95 % CI: 2.1-5.4) in MSM. Prevalence was highest among 18-24 year-old women (9 %; 95 % CI: 5.8-13) and heterosexual men (5.7 %; 95 % CI: 3.0-9.8 %), respectively. Among MSM, the prevalence was highest among 30-39 year-olds (4.4 %; 95 % CI: 1.9-8.5 %). Among those who tested positive, 76.7 % of women, 75.0 % of heterosexual men and 84.2 % of MSM were asymptomatic. Among women, factors associated with Chlamydia infection were young age (18-24 years versus ≥ 40 years, aPR: 3.0, 95 % CI: 1.2-7.8), having had more than 2 partners over the past 6 months (ref.: one partner, aPR: 2.1, 95 % CI: 1.1-4.0) and being born abroad (aPR: 1.9, 95 % CI: 1.0-3.5). Among heterosexual men, young age was associated with Chlamydia infection (18-24 years versus ≥ 40 years, aPR: 4.1, 95 % CI: 1.3-13). Among MSM, none of the variables were associated with Chlamydia infection. CONCLUSIONS: LPHA offering HIV tests should consider offering routine Chlamydia testing to women under 30 years. Women with multiple partners and those born abroad may also be considered for routine testing. Our results also suggest offering routine Chlamydia testing to heterosexual men under 25 years old. For MSM, we cannot draw specific recommendations based on our study as we estimated the prevalence of urethral Chlamydia infection, leaving out rectal and pharyngeal infections.

Development of an immunofiltration-based antigen-detection assay for rapid diagnosis of Ebola virus infection.

Ebola virus (EBOV) has caused outbreaks of severe viral hemorrhagic fever in regions of Central Africa where medical facilities are ill equipped and diagnostic capabilities are limited. To obtain a reliable test that can be implemented easily under these conditions, monoclonal antibodies to the EBOV matrix protein (VP40), which previously had been found to work in a conventional enzyme-linked immunosorbent assay, were used to develop an immunofiltration assay for the detection of EBOV antigen in chemically inactivated clinical specimens. The assay was evaluated by use of defined virus stocks and specimens from experimentally infected animals. Its field application was tested during an outbreak of Ebola hemorrhagic fever in 2003. Although the original goal was to develop an assay that would detect all EBOV species, only the Zaire and Sudan species were detected in practice. The assay represents a first-generation rapid field test for the detection of EBOV antigen that can be performed in 30 min without electrical power or expensive or sensitive equipment.

Production of monoclonal antibodies and development of an antigen capture ELISA directed against the envelope glycoprotein GP of Ebola virus.

Ebola virus (EBOV) causes severe outbreaks of Ebola hemorrhagic fever in endemic regions of Africa and is considered to be of impact for other parts of the world as an imported viral disease. To develop a new diagnostic test, monoclonal antibodies to EBOV were produced from mice immunized with inactivated EBOV species Zaire. Antibodies directed against the viral glycoprotein GP were characterized by ELISA, Western blot and immunofluorescence analyses. An antigen capture ELISA was established, which is specific for EBOV-Zaire and shows a sensitivity of approximately 10(3) plaque-forming units/ml. Since the ELISA is able to detect even SDS-inactivated EBOV in spiked human sera, it could complement the existing diagnostic tools in the field and in routine laboratories where high containment facilities are not available.

Development, characterization and use of monoclonal VP40-antibodies for the detection of Ebola virus.

Ebola virus (EBOV) causes uncommon but dramatic outbreaks in remote regions of Africa, where diagnostic facilities are limited. In order to develop diagnostic tests, which can be handled and distributed easily, monoclonal antibodies (mAbs) to EBOV, species Zaire, were produced from mice immunized with inactivated viral particles. Nine stable hybridoma cell lines were obtained producing specific mAbs directed against the viral structural protein VP40. These mAbs were characterized by enzyme-linked immunosorbent, immunoblot and immunofluorescence assays. Subsequently, an antigen capture enzyme-linked immunosorbent assay was established, which detects VP40 of all known species of EBOV. This assay could detect viral material in spiked human serum that has been sodium dodecylsulfate-inactivated. The established enzyme-linked immunosorbent assay therefore has the ability to become a very useful tool for obtaining an accurate diagnosis in the field, limiting the risk of laboratory infections.