Relative sensitivities of licensed nucleic acid amplification tests for detection of viremia in early human immunodeficiency virus and hepatitis C virus infection

Comparison of two nucleic acid amplification technology systems for detection of human immunodeficiency virus, hepatitis B virus, and hepatitis C virus

Human immunodeficiency virus (HIV) and hepatitis B virus (HBV) are endemic in South Africa while hepatitis C virus (HCV) infection is rare. Two nucleic acid amplification technology platforms, the Procleix Ultrio Elite assay on the Panther instrument (Elite) and the cobas MPX assay on the cobas 6800 or 8800 system (MPX), are used worldwide. In 2015 these were evaluated in South African context.

STUDY DESIGN AND METHODS

The sensitivity of HIV, HBV, and HCV was evaluated using reference panels and 2-fold dilutions of 51 positive plasma samples tested in 12 to 24 replicates. The 95% and 50% lower limits of detection (LOD) were estimated by probit analysis and window period (WP) risk days by the Weusten model. Specificity was established by testing 3646 blood donations individually and instrument performance by evaluating all runs.

RESULTS

Specificity was 99.94% for MPX and 99.97% for Elite. The following 95% LODs (95% confidence intervals [CIs]) were estimated for MPX and Elite, respectively: HBV, 17.8 (10.9-33.9) and 47.9 (29.1-92.4) cp/mL; HCV, 21.9 (15.3-34.6) and 13.8 (8.9-24.0) cp/mL; and HIV, 8.3 (5.5-14.7) and 10.4 (6.9-18.2) cp/mL. On SA HBV and HIV dilution panels, relative sensitivity (range) of MPX was 3.20 (1.26-6.50) and 1.42 (0.26-2.72) fold higher than Elite. Downtime on cobas 6800 was 26 hours vs 6.6 hours on Panther (P < .001). We estimated infectious WPs for HBV, HCV, and HIV-1 at 13.8, 1.8, and 2.6 days for Elite and 10.3, 2.1, and 2.4 days for MPX.

CONCLUSION

Although MPX was significantly more sensitive for HBV, Elite was implemented due to instrument reliability during evaluation.

Transfusion-transmitted hepatitis C: A cluster of cases in transfusion-dependent thalassaemia patients in Sri Lanka

OBJECTIVES

To report the clinical and virologic epidemiology of a recent epidemic of hepatitis C in thalassaemia patients in Sri Lanka.

BACKGROUND

Transfusion-dependent thalassaemia patients remain at risk for hepatitis C virus (HCV). Here, we report a cluster of recent HCV infections in Sri Lankan thalassaemia patients and examine the phylogenetic relationship of viral sequences.

METHODS

We conducted two prospective cross-sectional surveys of 513 patients in four Sri Lankan thalassaemia centres in 2014/2015 and re-surveyed one centre in 2016. We screened for anti-HCV antibodies using the CTK Biotech enzyme-linked immunosorbent assay (ELISA) kits and confirmed active infection by reverse transcription-polymerase chain reaction (RT-PCR) for HCV-RNA. HCV genomes were sequenced by unbiased target enrichment.

RESULTS

Anti-HCV antibodies were found in 116/513 (22.6%) of patients initially tested. Active hepatitis C infection was found in 26 patients with no cases of active hepatitis B infection. Of 26 patients with HCV, two were infected with genotype 1(a), and the rest had 3(a). In a single centre (Ragama), 122 patients (120 new cases and two previously tested, but negative) were retested for anti-HCV antibodies. 32/122 (26.2%) patients were seropositive. Twenty-three (23/122; 18.8%) of these new cases were confirmed by HCV PCR (all genotype 3[a]).

CONCLUSION

There is a significant cluster of recent HCV cases in multiply transfused thalassaemia patients in several centres in Sri Lanka. Most of the viruses shared a close phylogenetic relationship. The results are consistent with recent continuing transfusion-transmitted HCV infection. Routine surveillance for HCV of chronically transfused patients is required irrespective of screening of blood products.

The Alphabet Soup of HIV Reservoir Markers

PURPOSE OF REVIEW

Despite the success of antiretroviral therapy in suppressing HIV, life-long therapy is required to avoid HIV reactivation from long-lived viral reservoirs. Currently, there is intense interest in searching for therapeutic interventions that can purge the viral reservoir to achieve complete remission in HIV patients off antiretroviral therapy. The evaluation of such interventions relies on our ability to accurately and precisely measure the true size of the viral reservoir. In this review, we assess the most commonly used HIV reservoir assays, as a clear understanding of the strengths and weaknesses of each is vital for the accurate interpretation of results and for the development of improved assays.

RECENT FINDINGS

The quantification of intracellular or plasma HIV RNA or DNA levels remains the most commonly used tests for the characterization of the viral reservoir. While cost-effective and high-throughput, these assays are not able to differentiate between replication-competent or defective fractions or quantify the number of infected cells. Viral outgrowth assays provide a lower bound for the fraction of cells that can produce infectious virus, but these assays are laborious, expensive and substantially underestimate the potential reservoir of replication-competent provirus. Newer assays are now available that seek to overcome some of these problems, including full-length proviral sequencing, inducible HIV RNA assays, ultrasensitive p24 assays and murine adoptive transfer techniques. The development and evaluation of strategies for HIV remission rely upon our ability to accurately and precisely quantify the size of the remaining viral reservoir. At this time, all current HIV reservoir assays have drawbacks such that combinations of assays are generally needed to gain a more comprehensive view of the viral reservoir. The development of novel, rapid, high-throughput assays that can sensitively quantify the levels of the replication-competent HIV reservoir is still needed.

Modeling complete removal of risk assessment questions in the USA predicts the risk of HIV exposure in blood recipients could increase despite the use of nucleic acid testing

BACKGROUND AND OBJECTIVES

The safety of the blood supply in a number of countries is achieved by interventions that include behaviour-based time-limited or indefinite deferrals and screening of donated units for transfusion-transmitted infections. The relatively high sensitivity of nucleic acid testing (NAT) used in blood donor screening has raised the question of whether such time-based deferrals can be eliminated in favour of individual risk assessment.

MATERIALS AND METHODS

Data on the annual number of incident human immunodeficiency virus (HIV) infections associated with various behaviours and on the performance characteristics of NAT applied to donor screening were used to model the number of potentially infected units that might escape detection in the worst-case scenario in which individual risk assessment was implemented, but was not effective as a screening tool, and donors did not otherwise self-select for lower risk.

RESULTS

In the absence of effective individual risk-based screening or donor self-selection, the model predicts that in the United States, an additional 39 (95% CI 35-43) HIV-infected units would escape detection by nucleic acid testing, potentially capable of exposing approximately 68 (95% CI 61-75) individuals to the risk of HIV infection through the administration of prepared blood components.

CONCLUSION

Despite some inherent uncertainty, the worst-case scenario of completely ineffective individual risk assessment, absence of donor self-selection and increased reliance on NAT for blood screening is estimated to be associated with an approximately fourfold increase in the risk of HIV exposure through transfusion in the United States.

Transmission of Hepatitis C Virus From Organ Donors Despite Nucleic Acid Test Screening

Nucleic acid testing (NAT) for hepatitis C virus (HCV) is recommended for screening of organ donors, yet not all donor infections may be detected. We describe three US clusters of HCV transmission from donors at increased risk for HCV infection. Donor's and recipients' medical records were reviewed. Newly infected recipients were interviewed. Donor-derived HCV infection was considered when infection was newly detected after transplantation in recipients of organs from increased risk donors. Stored donor sera and tissue samples were tested for HCV RNA with high-sensitivity quantitative PCR. Posttransplant and pretransplant recipient sera were tested for HCV RNA. Quasispecies analysis of hypervariable region-1 was used to establish genetic relatedness of recipient HCV variants. Each donor had evidence of injection drug use preceding death. Of 12 recipients, 8 were HCV-infected-6 were newly diagnosed posttransplant. HCV RNA was retrospectively detected in stored samples from donor immunologic tissue collected at organ procurement. Phylogenetic analysis showed two clusters of closely related HCV variants from recipients. These investigations identified the first known HCV transmissions from increased risk organ donors with negative NAT screening, indicating very recent donor infection. Recipient informed consent and posttransplant screening for blood-borne pathogens are essential when considering increased risk donors.

Expanded criteria donors

The greatest challenge facing liver transplantation today is the shortage of donor livers. Demand far exceeds supply, and this deficit has driven expansion of what is considered an acceptable organ. The evolving standard has not come without costs, however, as each new frontier of expanded donor quality (i.e., advancing donor age, donation after cardiac death, and split liver) may have traded wait-list for post-transplant morbidity and mortality. This article delineates the nature and severity of risk associated with specific deceased donor liver characteristics and recommends strategies to maximally mitigate these risks.

Screening tests for hepatitis B virus, hepatitis C virus, and human immunodeficiency virus in blood donors: evaluation of two chemiluminescent immunoassay systems

Automated chemiluminescent immunoassays (CLIAs) are useful for the detection of hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus 1/2 antigen/antibodies (HIV 1/2 Ag/Ab) in blood donor screening. Eight hundred and forty serum samples were tested for hepatitis B surface antigen (HBsAg), HCV antibodies (anti-HCV), and HIV1/2 Ag/Ab in parallel using 2 different CLIAs (Abbott Architect i2000SR and Roche Cobas e411). The concordance between the 2 systems was high (Cohen's kappa 0.97 for HBsAg, 0.77 for anti-HCV, 0.92 for HIV1/2 Ag/Ab) and the specificity and the positive predictive value were comparable. Among the 12 discrepant results, 11 were false-positive and 1 (reactive by Architect) was true-positive for anti-HCV. Positivity for HBV DNA, HCV RNA, and HIV RNA was recorded in 90.9%, 38.9%, and 100% of true-positive samples, respectively. This study represents the first stringent comparison between Architect i2000SR and Cobas e411 in blood donors. We observed a good correlation and high agreement among HBV, HCV, and HIV with the 2 automated systems.

Development of a microchip Europium nanoparticle immunoassay for sensitive point-of-care HIV detection

Rapid, sensitive and specific diagnostic assays play an indispensable role in determination of HIV infection stages and evaluation of efficacy of antiretroviral therapy. Recently, our laboratory developed a sensitive Europium nanoparticle-based microtiter-plate immunoassay capable of detecting target analytes at subpicogram per milliliter levels without the use of catalytic enzymes and signal amplification processes. Encouraged by its sensitivity and simplicity, we continued to miniaturize this assay to a microchip platform for the purpose of converting the benchtop assay technique to a point-of-care test. It was found that detection capability of the microchip platform could be readily improved using Europium nanoparticle probes. We were able to routinely detect 5 pg/mL (4.6 attomoles) of HIV-1 p24 antigen at a signal-to-blank ratio of 1.5, a sensitivity level reasonably close to that of microtiter-plate Europium nanoparticle assay. Meanwhile, use of the microchip platform effectively reduced sample/reagent consumption 4.5 fold and shortened total assay time 2 fold in comparison with microtiter plate assays. Complex matrix substance in plasma negatively affected the microchip assays and the effects could be minimized by diluting the samples before loading. With further improvements in sensitivity, reproducibility, usability, assay process simplification, and incorporation of portable time-resolved fluorescence reader, Europium nanoparticle immunoassay technology could be adapted to meet the challenges of point-of-care diagnosis of HIV or other health-threatening pathogens at bedside or in resource-limited settings.

Reduction of HIV persistence following transplantation in HIV-infected kidney transplant recipients

Chronic inflammation may contribute to human immunodeficiency virus (HIV) persistence through a number of potential pathways. We explored the impact of immunosuppressant therapy on peripheral blood measures of HIV persistence following kidney transplantation. Stored plasma and peripheral blood mononuclear cells prior to transplantation and at weeks 12, 26, 52 and 104 posttransplant were obtained from 91 transplant recipients. In a multivariate model, higher pretransplant plasma HIV RNA level (p < 0.0001) and a longer duration of follow-up posttransplant (p = 0.09) were associated with higher posttransplant plasma HIV RNA levels. A higher baseline HIV DNA (p < 0.0001) was significantly associated with higher HIV DNA levels posttransplant, while higher CD4+ T cell count (p = 0.001), sirolimus use (p = 0.04) and a longer duration of follow-up (p = 0.06) were associated with lower posttransplant HIV DNA levels. The association between sirolimus exposure and lower frequency of cells containing HIV DNA levels posttransplant suggest that the immune-modifying drugs may affect the level of HIV persistence during effect therapy. Future studies of sirolimus as a reservoir-modifying agent are warranted.

Reducing infection transmission in solid organ transplantation through donor nucleic acid testing: a cost-effectiveness analysis

For solid organ transplant (SOT) donors, nucleic acid-amplification testing (NAT) may reduce human immunodeficiency virus (HIV) and hepatitis C virus (HCV) transmission over antibody (Ab) testing given its shorter detection window period. We compared SOT donor NAT + Ab versus Ab alone using decision models to estimate incremental cost-effectiveness ratios (ICERs; cost per quality-adjusted life year [QALY] gained) from the societal perspective across a range of HIV/HCV prevalence values and NAT costs. The cost per QALY gained was calculated for two scenarios: (1) favorable: low cost ($150/donor)/high prevalence (HIV: 1.5%; HCV: 18.2%) and (2) unfavorable: high cost ($500/donor)/low prevalence (HIV: 0.1%; HCV: 1.5%). In the favorable scenario, adding NAT screening cost $161 013 per QALY gained for HIV was less costly) for HCV, and cost $86 653 per QALY gained for HIV/HCV combined. For the unfavorable scenario, the costs were $15 568 484, $221 006 and $10 077 599 per QALY gained, respectively. Universal HCV NAT + Ab for donors appears cost-effective to reduce infection transmission from SOT donors, while HIV NAT + Ab is not, except where HIV NAT is ≤$150/donor and prevalence is ≥1.5%. Our analyses provide important data to facilitate the decision to implement HIV and HCV NAT for deceased SOT donors and shape national policy regarding how to reduce infection transmission in SOT.

Challenges in detecting HIV persistence during potentially curative interventions: a study of the Berlin patient

There is intense interest in developing curative interventions for HIV. How such a cure will be quantified and defined is not known. We applied a series of measurements of HIV persistence to the study of an HIV-infected adult who has exhibited evidence of cure after allogeneic hematopoietic stem cell transplant from a homozygous CCR5Δ32 donor. Samples from blood, spinal fluid, lymph node, and gut were analyzed in multiple laboratories using different approaches. No HIV DNA or RNA was detected in peripheral blood mononuclear cells (PBMC), spinal fluid, lymph node, or terminal ileum, and no replication-competent virus could be cultured from PBMCs. However, HIV RNA was detected in plasma (2 laboratories) and HIV DNA was detected in the rectum (1 laboratory) at levels considerably lower than those expected in ART-suppressed patients. It was not possible to obtain sequence data from plasma or gut, while an X4 sequence from PBMC did not match the pre-transplant sequence. HIV antibody levels were readily detectable but declined over time; T cell responses were largely absent. The occasional, low-level PCR signals raise the possibility that some HIV nucleic acid might persist, although they could also be false positives. Since HIV levels in well-treated individuals are near the limits of detection of current assays, more sensitive assays need to be developed and validated. The absence of recrudescent HIV replication and waning HIV-specific immune responses five years after withdrawal of treatment provide proof of a clinical cure.

There is intense interest in developing a cure for HIV. How such a cure will be quantified and defined is not known. We applied a series of measurements of HIV persistence to the study of an HIV+ adult who has exhibited evidence of cure after a stem cell transplant. Samples from blood, spinal fluid, lymph node, and gut were analyzed in multiple laboratories using different approaches. No HIV was detected in blood cells, spinal fluid, lymph node, or small intestine, and no infectious virus was recovered from blood. However, HIV was detected in plasma (2 laboratories) and HIV DNA was detected in the rectum (1 laboratory) at levels considerably lower than those expected in antiretroviral treated patients. The occasional, low-level HIV signals might be due to persistent HIV or might reflect false positives. The sensitivity of the current generation of assays to detect HIV RNA, HIV DNA, and infectious virus are close to the limits of detection. Improvements in these tests will be needed for future curative studies. The lack of rebounding virus after five years without therapy, the failure to isolate infectious virus, and the waning HIV-specific immune responses all indicate that the Berlin Patient has been effectively cured.

Comparative analysis of triplex nucleic acid test assays in United States blood donors

BACKGROUND

This study assessed the clinical sensitivity of three fully automated, human immunodeficiency virus (HIV), hepatitis C virus (HCV), and hepatitis B virus (HBV) triplex nucleic acid test (NAT) assays by individual donation (ID-NAT) and at operational minipool (MP-NAT) sizes used worldwide.

STUDY DESIGN AND METHODS

MPX, Ultrio, and Ultrio Plus were used to test 2222 pedigreed, marker-positive samples with varying viral loads, each from a unique US blood donor. NAT-positive, seronegative yield samples (16 HBV, 156 HCV, and 23 HIV) were tested in replicates of three; undiluted; and in 1:6, 1:8, and 1:16 dilutions (MP6, MP8, and MP16), simulating various MP sizes. Seropositive samples (1276 HBV, 488 HCV, and 263 HIV) were tested by ID-NAT in singlet.

RESULTS

MPX-MP6 and Ultrio Plus-MP16 had equivalent HCV sensitivity. Although Ultrio Plus-MP16 for HIV trended toward lesser sensitivity, this was not corroborated in a large substudy of low-viral-load samples in which Ultrio Plus-MP8/MP16 showed 100% reactivity. MPX-ID and Ultrio Plus-ID HBV clinical sensitivity were identical, but MPX-MP6 was significantly more sensitive than Ultrio Plus-MP16; the differential yield projected to one HBV NAT yield per 4.72 million US donations. Ultrio Plus HBV sensitivity did not increase at MP8 versus MP16. Ultrio Plus versus Ultrio sensitivity was significantly increased in HBV-infected donors with early acute, late acute or chronic, and occult infections. No difference in sensitivity was noted for any virus for MPX-MP6 versus Ultrio Plus-ID.

CONCLUSIONS

Our data support US donation screening with MPX-MP6 or Ultrio Plus-MP16 since the HBV DNA detection of Ultrio Plus was significantly enhanced (vs. Ultrio) without compromising HIV or HCV RNA detection.

The National Heart, Lung, and Blood Institute retrovirus epidemiology donor studies (Retrovirus Epidemiology Donor Study and Retrovirus Epidemiology Donor Study-II): twenty years of research to advance blood product safety and availability

The Retrovirus Epidemiology Donor Study (REDS), conducted from 1989 to 2001, and the REDS-II, conducted from 2004 to 2012, were National Heart, Lung, and Blood Institute-funded, multicenter programs focused on improving blood safety and availability in the United States. The REDS-II also included international study sites in Brazil and China. The 3 major research domains of REDS/REDS-II have been infectious disease risk evaluation, blood donation availability, and blood donor characterization. Both programs have made significant contributions to transfusion medicine research methodology by the use of mathematical modeling, large-scale donor surveys, innovative methods of repository sample storage, and establishing an infrastructure that responded to potential emerging blood safety threats such as xenotropic murine leukemia virus-related virus. Blood safety studies have included protocols evaluating epidemiologic and/or laboratory aspects of human immunodeficiency virus, human T-lymphotropic virus 1/2, hepatitis C virus, hepatitis B virus, West Nile virus, cytomegalovirus, human herpesvirus 8, parvovirus B19, malaria, Creutzfeldt-Jakob disease, influenza, and Trypanosoma cruzi infections. Other analyses have characterized blood donor demographics, motivations to donate, factors influencing donor return, behavioral risk factors, donors' perception of the blood donation screening process, and aspects of donor deferral. In REDS-II, 2 large-scale blood donor protocols examined iron deficiency in donors and the prevalence of leukocyte antibodies. This review describes the major study results from over 150 peer-reviewed articles published by these 2 REDS programs. In 2011, a new 7-year program, the Recipient Epidemiology and Donor Evaluation Study-III, was launched. The Recipient Epidemiology and Donor Evaluation Study-III expands beyond donor-based research to include studies of blood transfusion recipients in the hospital setting and adds a third country, South Africa, to the international program.

Evolving epidemiology of hepatitis C virus in the United States

The impact of hepatitis C virus (HCV) infection on health and medical care in the United States is a major problem for infectious disease physicians. Although the incidence of HCV infection has declined markedly in the past 2 decades, chronic infection in 3 million or more residents now accounts for more disease and death in the United States than does human immunodeficiency virus (HIV)/AIDS. Current trends in the epidemiology of HCV infection include an apparent increase in young, often suburban heroin injection drug users who initiate use with oral prescription opioid drugs; infections in nonhospital healthcare (clinic) settings; and sexual transmission among HIV-infected persons. Infectious disease physicians will increasingly have the responsibility of diagnosing and treating HCV patients. An understanding of how these patients were infected is important for determining whom to screen and treat.

Infectivity in chimpanzees (Pan troglodytes) of plasma collected before HCV RNA detectability by FDA-licensed assays: implications for transfusion safety and HCV infection outcomes

Serial plasma aliquots (50 mL) obtained from 10 commercial donors who converted from hepatitis C virus (HCV) RNA negative to positive were transfused into 2 chimpanzees to assess infectivity during early HCV infection. Plasma, obtained 4 days before HCV RNA detectability by licensed assays, transmitted HCV infection to chimpanzee X355. The infectious PCR-negative plasma was subsequently shown to be positive in 2 of 23 replicates using a sensitive transcription-mediated amplification (TMA) assay, and estimated to contain 1.2 HCV RNA copies/mL (60 copies/50 mL transfused). Plasma units obtained up to 8 weeks earlier were not infectious in a second susceptible chimp, even when from donors with low-level, intermittent HCV RNA detection. Chimp x355 developed acute viremia with subsequent seroconversion, but cleared both virus and Ab in 17 weeks. When rechallenged 38 months later with 6000 RNA copies/mL from the same donor, X355 was transiently reinfected and again rapidly lost all HCV markers. We conclude that: (1) transfusions can transmit HCV infection before RNA detection, but the interval of test-negative infectivity is very brief; (2) early "blips" of HCV RNA appear noninfectious and can be ignored when calculating residual transfusion risk; and (3) markers of HCV infection can be lost rapidly after exposure to low-dose inocula.

Sequential bottlenecks drive viral evolution in early acute hepatitis C virus infection

Hepatitis C is a pandemic human RNA virus, which commonly causes chronic infection and liver disease. The characterization of viral populations that successfully initiate infection, and also those that drive progression to chronicity is instrumental for understanding pathogenesis and vaccine design. A comprehensive and longitudinal analysis of the viral population was conducted in four subjects followed from very early acute infection to resolution of disease outcome. By means of next generation sequencing (NGS) and standard cloning/Sanger sequencing, genetic diversity and viral variants were quantified over the course of the infection at frequencies as low as 0.1%. Phylogenetic analysis of reassembled viral variants revealed acute infection was dominated by two sequential bottleneck events, irrespective of subsequent chronicity or clearance. The first bottleneck was associated with transmission, with one to two viral variants successfully establishing infection. The second occurred approximately 100 days post-infection, and was characterized by a decline in viral diversity. In the two subjects who developed chronic infection, this second bottleneck was followed by the emergence of a new viral population, which evolved from the founder variants via a selective sweep with fixation in a small number of mutated sites. The diversity at sites with non-synonymous mutation was higher in predicted cytotoxic T cell epitopes, suggesting immune-driven evolution. These results provide the first detailed analysis of early within-host evolution of HCV, indicating strong selective forces limit viral evolution in the acute phase of infection.

Primary hepatitis C (HCV) infection is typically asymptomatic and commonly results in persistent infection. The characteristics of early infection remain undefined. Four subjects were studied longitudinally from within a few weeks of transmission until resolution of outcome, via a full genome analysis of viral evolution. In the acute phase (<100 days post-infection) there were two periods with a major reduction in genetic diversity (i.e. a bottleneck) irrespective of subsequent clearance (n = 2) or chronic infection (n = 2). The first bottleneck was associated with transmission, with generally only one ‘founder’ virus successfully establishing infection. The second occurred following the primary peak in viraemia, concomitant with seroconversion, approximately 100 days post-infection. In the subjects who became chronically infected, the second bottleneck was followed by emergence of a new cluster of variants, which evolved from the founder(s), and carried only a small number of mutated residues that reached fixation. Some fixations occurred in known targets of CD8 cytotoxic T cell and neutralizing antibody responses. These results indicate a common evolutionary pattern, independent of disease outcome in the acute phase of HCV infection, with strong signatures of selective pressures driving the transition into chronic infection. These novel data will inform preventative vaccine strategies.

Modification of the Abbott RealTime assay for detection of HIV-1 plasma RNA viral loads less than one copy per milliliter

Although commercial tests are approved for detection of HIV-1 plasma viral loads ≥ 20 copies per milliliter (ml), only one specialized research assay has been reported to detect plasma viral loads as low as 1 copy/ml. This manuscript describes a method of concentrating HIV-1 virions from up to 30 ml of plasma, which can be combined with a commercial viral load test to create a widely available, reproducible assay for quantifying plasma HIV RNA levels less than 1 copy/ml. Using this pre-analytically modified assay, samples with a known level of 0.5 copy/ml were detected in 8 of 12 replicates (mean 0.47 copy/ml; 95% confidence interval (CI) 0.14-0.81 copy/ml) and samples with a known level of 1.0 copy/ml were detected in 13 of 13 replicates (mean 1.96 copy/ml; 95% CI 1.42-2.50 copy/ml). By concentrating virus from 30 ml of plasma, HIV RNA could be measured in 16 of 19 samples (84%) from 12 of 12 subjects (mean 2.77 copy/ml; 95% CI 0.86-4.68 copy/ml). The measured viral load correlated inversely (r = -0.78; p = 0.028) with the total duration of viral suppression (viral load<40 copies/ml).

Absence of reproducibly detectable low-level HIV viremia in highly exposed seronegative men and women

OBJECTIVE

Transient HIV infections have been invoked to account for the cellular immune responses detected in highly virus-exposed individuals who have remained HIV-seronegative. We tested for very low levels of HIV RNA in 524 seronegative plasma samples from 311 highly exposed women and men from three longitudinal HIV cohorts.

DESIGN

Two thousand and seventy-three transcription-mediated amplification (TMA) HIV RNA tests were performed for an average of 3.95 TMA assays per plasma sample. Quadruplicate TMA assays, analyzing a total of 2 ml of plasma, provided an estimated sensitivity of 3.5 HIV RNA copies/ml.

RESULTS

Four samples from individuals who did not seroconvert within the following 6 months were positive for HIV RNA. For one sample, human polymorphism DNA analysis indicated a sample mix-up. Borderline HIV RNA detection signals were detected for the other three positive samples but further replicate TMA testing yielded no positive results. Nested PCR assays (n = 254) for HIV proviral DNA in peripheral blood mononuclear cells (PBMCs) from these three individuals were negative.

CONCLUSION

Transient viremia was not reproducibly detected in highly HIV-exposed seronegative men and women. If transient infections do occur, plasma HIV RNA levels may remain below the detection limits of the sensitive assay used here, be of very short duration, or viral replication may be restricted to mucosal surfaces or their draining lymphoid tissues.

HIV-specific CD4+ T cells may contribute to viral persistence in HIV controllers

BACKGROUND

Human immunodeficiency virus (HIV)--infected individuals maintaining plasma HIV RNA levels <75 copies/mL in the absence of therapy ("HIV controllers") often maintain high HIV-specific T cell responses, which likely contribute to the control of viral replication. Despite robust immune responses, these individuals never eradicate HIV infection. We hypothesized that HIV-specific CD4(+) T cells might serve as target cells for HIV, contributing to viral persistence in this setting.

METHODS

We measured frequencies of activated (CD38(+) HLA-DR(+)) and HIV Gag-specific CD4(+) and CD8(+) T cells and plasma- and cell-associated levels of HIV RNA and DNA in a cohort of 38 HIV controllers.

RESULTS

Although there was no evidence of a relationship between the extent of low-level viremia and the frequency of either activated or HIV-specific CD4(+) T cells, controllers with higher HIV-specific CD4(+) T cell frequencies had higher cell-associated HIV DNA levels (ρ = 0.53; P = .019). Higher activated CD4+ T cell frequencies were also associated with higher levels of cell-associated DNA (P = .027) and RNA (P = .0096). However, there was no evidence of a relationship between cell-associated HIV RNA or DNA levels and HIV-specific CD8(+) T cell frequencies.

CONCLUSIONS

These data support a model in which strong HIV-specific CD4(+) T cell responses in HIV controllers, while contributing to a potent adaptive immune response, may also contribute to viral persistence, preventing the natural eradication of HIV infection.

Decreased prevalence and incidence of HCV markers in haemodialysis units: a multicentric French survey

BACKGROUND

A variety of epidemiological data provide evidence for the nosocomial transmission of hepatitis C virus (HCV) infections to haemodialysis patients. We conducted a multicentric study to determine the prevalence and incidence of HCV infection in French haemodialysis units.

METHODS

Patients undergoing chronic haemodialysis in 56 French units (4718 patients) were systematically screened for anti-HCV antibodies using third-generation tests. The incidence was estimated by detecting HCV RNA in seronegative patients using a standardized real-time PCR assay on pooled samples.

RESULTS

Testing for HCV antibodies identified 361 patients with anti-HCV antibodies, giving a prevalence of 7.7%. Multivariate analysis demonstrated that anti-HCV status was linked to the time on haemodialysis, previous kidney transplantation and the presence of anti-HBc antibodies, whereas erythropoietin therapy and carrying out dialysis in dedicated spaces seem to protect against HCV infection. Only two of the 4357 patients without anti-HCV antibodies tested positive for HCV RNA, giving an estimated incidence of 0.05% new HCV infections/year. Molecular analyses indicated that the two patients probably acquired HCV outside the haemodialysis unit.

CONCLUSION

This decreased prevalence and incidence emphasizes the importance of adhering to the recommended universal infection-control precautions. Virological follow-up based on detecting anti-HCV antibodies with sensitive, specific new-generation serological tests could be adequate for dialysis units with few HCV infections. However, new infections in haemodialysis units should be identified by determining the HCV RNA status of seronegative patients. Standardized real-time PCR assays, plus pooling serum samples, make this a promising method for large-scale epidemiological studies.

Hepatitis C virus prevalence and clearance among US blood donors, 2006-2007: associations with birth cohort, multiple pregnancies, and body mass index

BACKGROUND

During the period 1992-1993, the prevalence of hepatitis C virus (HCV) antibodies (anti-HCV) among US blood donors was 0.36%, but contemporary data on the prevalence of antibody to HCV and the prevalence of HCV RNA are lacking.

METHODS

We performed a large, cross-sectional study of blood donors at 6 US blood centers during 2006-2007. Anti-HCV was measured with enzyme-linked immunosorbent assay followed by immunoblot, and HCV RNA was measured with nucleic acid testing. Adjusted odds ratios (aORs) were derived using multivariable logistic regression.

RESULTS

Of 959,281 donors, 695 had anti-HCV detected (prevalence, 0.072%). Of those with anti-HCV, 516 (74%) had test results positive for HCV RNA, and 179 (26%) had test results that were negative for HCV RNA. Compared with the prevalence during the period 1992-1993, prevalence during 2006-2007 was lower and peaked in older age groups. Anti-HCV was associated with a body mass index (BMI) >30 (aOR, 0.6; 95% confidence interval [CI], 0.5-0.8), and among women, it was associated with higher gravidity (aOR for 5 vs 0 pregnancies, 3.2; 95% CI, 1.9-5.4). HCV RNA negative status was associated with black race (aOR, 0.4; 95% CI, 0.2-0.7), having more than a high school education (aOR, 1.6; 95% CI, 1.1-2.4), and BMI >30 (aOR, 2.4; 95% CI, 1.4-3.9).

CONCLUSIONS

Decreasing HCV prevalence is most likely attributable to culling of seropositive donors and a birth cohort effect. We found new associations between anti-HCV prevalence and gravidity and obesity. Recently discovered genetic factors may underlie differences in HCV RNA clearance in black donors.

Sensitivity of two hepatitis B virus, hepatitis C virus (HCV), and human immunodeficiency virus (HIV) nucleic acid test systems relative to hepatitis B surface antigen, anti-HCV, anti-HIV, and p24/anti-HIV combination assays in seroconversion panels

BACKGROUND

Accurate determination of the infectious window period (IWP) that remains with individual-donation (ID) or minipool (MP) NAT compared to those with serology assays is essential for residual risk estimations.

STUDY DESIGN AND METHODS

The relative sensitivity of the Procleix Tigris system (Gen-Probe/Chiron) used in ID-NAT format and cobas s 201 (Roche Molecular Systems) applied in 1:6 diluted samples to mimic six-minipool (MP6) nucleic acid test (NAT) was assessed by quadruplicate testing of five seroconversion panels per marker. A mathematical analysis based on the log-linear increase of viremia in the ramp-up phase, as established with bDNA 3.0 assays enabled estimation of the IWP for human immunodeficiency virus (HIV) and hepatitis B virus (HBV) assays.

RESULTS

The mean IWPs were Tigris HIV RNA 5.5 days, s 201 (1:6) HIV RNA 7.4 days, GenScreen Plus p24/anti-HIV 17.8 days, PRISM anti-HIV 19.0 days, Tigris HBV DNA 20.6 days, s 201 (1:6) HBV DNA 22.6 days, Bio-Rad hepatitis B surface antigen (HBsAg) 37.8 days, and PRISM HBsAg 35.5 days. At estimated 50 percent NAT seroconversion rates, s 201 (1:6) and Tigris showed mean window-period reduction times (WPRTs) of 30.5 to 35.5 days to hepatitis C virus antibody (anti-HCV) assays, 10.4 to 13.5 days to anti-HIV, or combination p24/anti-HIV assays and 12.8 to 17.2 days to HBsAg assays.

CONCLUSIONS

Tigris ID-NAT detected HIV RNA 2 days earlier than s 201 MP6-NAT, but the difference in sensitivity between the two NAT systems was not significant in HBV seroconversion panels. Insufficient seroconversion samples were available for reliable modeling of WPRT in early HCV infection, but 1.4 to 2.0 days could be predicted by translating analytical sensitivity data. Both multiplex NAT systems demonstrate significant WPRTs compared to (combined) antigen and antibody assays.

Evidence for persistent low-level viremia in individuals who control human immunodeficiency virus in the absence of antiretroviral therapy

A subset of antiretroviral-untreated, human immunodeficiency virus (HIV)-infected individuals are able to maintain undetectable plasma HIV RNA levels in the absence of antiretroviral therapy. These "elite" controllers are of high interest as they may provide novel insights regarding host mechanisms of virus control. The degree to which these individuals have residual plasma viremia has not been well defined. We performed a longitudinal study of 46 elite controllers, defined as HIV-seropositive, antiretroviral-untreated individuals with plasma HIV RNA levels of <50 to 75 copies/ml. The median duration of HIV diagnosis was 13 years, the median baseline CD4(+) T-cell count was 753 cells/mm(3), and the median duration of follow-up was 16 months. Plasma and cellular HIV RNA levels were measured using the transcription-mediated amplification (TMA) assay (estimated limit of detection of <3.5 copies RNA/ml). A total of 1,117 TMA assays were performed (median of five time points/subject and four replicates/time point). All but one subject had detectable plasma HIV RNA on at least one time point, and 15 (33%) subjects had detectable RNA at all time points. The majority of controllers also had detectable cell-associated RNA and proviral DNA. A mixed-effect linear model showed no strong evidence of change in plasma RNA levels over time. In conclusion, the vast majority (98%) of elite controllers had measurable plasma HIV RNA, often at levels higher than that observed in antiretroviral-treated patients. This confirms the failure to eradicate the virus, even in these unique individuals who are able to reduce plasma viremia to very low levels without antiretroviral therapy.

Comparison of two automated nucleic acid testing systems for simultaneous detection of human immunodeficiency virus and hepatitis C virus RNA and hepatitis B virus DNA

BACKGROUND

Recently developed nucleic acid testing (NAT) assays incorporating simultaneous detection of human immunodeficiency virus (HIV), hepatitis C virus (HCV), and hepatitis B virus (HBV) have made HBV NAT screening more feasible for blood services. This study compared the performance of two "multiplex" NAT assays and their automated testing platforms.

STUDY DESIGN AND METHODS

The HBV NAT yield rate was estimated by testing 10,397 Hong Kong (HK) donor samples concurrently on the PROCLEIX ULTRIO (Ultrio) assay as individual donor samples with the TIGRIS and on the cobas TaqScreen multiplex (cobas MPX) test in pools of 6 with the cobas s 201. Analytical sensitivity was assessed by probit analysis of diluted international standards and operational performance was compared.

RESULTS

Each system detected two different HBV NAT yield samples for a combined rate of 0.04 percent. One additional sample was reactive on the cobas MPX test but remained unresolved. The 95 percent detection limits for HIV-1, HBV, and HCV were 42.2, 12.2, and 2.0 IU per mL, respectively, for Ultrio and 50.5, 8.4, and 6.0 IU per mL for the cobas MPX. The invalid test and failed run rates were 0.05 and 2.92 percent, respectively, for the TIGRIS and 2.39 and 5.53 percent for the cobas s 201.

CONCLUSION

Clinical sensitivity for HBV in HK blood donors was equivalent, as was the analytical sensitivity for HIV-1 and HBV; however, the Ultrio assay had a higher analytical sensitivity for HCV. Despite a shorter downtime and mean time of repair for the cobas s 201, the TIGRIS demonstrated better overall operational performance.

Performance of a transcription-mediated-amplification HIV-1 RNA assay in pooled specimens

BACKGROUND

Very limited data exist on the comparative performance of nucleic acid amplification tests (NATs) for the screening of pooled specimens for acute human immunodeficiency virus (HIV) infection.

STUDY DESIGN

In this study, we compared a transcription-mediated-amplification assay (Procleix HIV-1 Discriminatory Assay, [TMA]) with a branched DNA assay (Bayer Versant HIV-1 RNA 3.0 assay, [bDNA]).

RESULTS

After re-testing 1552 samples that were negative for HIV RNA by bDNA, we found one additional positive sample with the TMA assay.

CONCLUSION

Our results suggest that TMA could potentially detect acute HIV infections missed by other technologies.

Current risks of transfusion-transmitted agents: a review

CONTEXT

Infectious disease testing has dramatically improved the safety of blood for transfusion in the United States, especially since the introduction in 1999 of nucleic acid amplification testing. In 2004, methods (primarily culturing) for detecting bacteria in platelets were also added.

OBJECTIVE

To provide current risk estimates for the likelihood of viral transmission by test-negative blood components and to illustrate the safety improvements since the introduction of bacterial testing of platelets.

DATA SOURCES

Published literature from 1999 through 2006 and unpublished American Red Cross data sources.

CONCLUSIONS

The risk of human immunodeficiency virus and hepatitis C virus transmission through blood transfusion since the introduction of nucleic acid amplification testing is approximately 1 in 2 million. Hepatitis B virus risk, for which nucleic acid amplification testing is not performed routinely, remains at 1 in 200,000 to 500,000 using a combination of anti-hepatitis B core and hepatitis B surface antigen testing. Seven cases of transfusion-transmitted West Nile virus have been reported since the introduction of nucleic acid amplification testing in 2003, but none has been reported since system-wide implementation of processes to increase the test sensitivity for use in epidemic areas. The residual risk of receiving a bacterially contaminated platelet component with clinical consequences is estimated at approximately 1 in 75,000, if culture negative and 1 in 33,000 if not tested by culture methods.

Evaluating the impact of public health notification of suspected transfusion-transmissible hepatitis C virus infection and effectiveness of lookback and traceback investigations by Canadian Blood Services in British Columbia, Canada, August 2002 through F

BACKGROUND

Suspected transfusion-transmissible infections (TTIs) have been reported to public health (PH) in British Columbia (BC) since August 2002. The impact of PH notification of suspected transfusion-transmissible hepatitis C virus (TT-HCV) infection over the first 2.5 years and the effectiveness of HCV lookback (LB) and traceback (TB) investigations conducted by Canadian Blood Services (CBS) in BC were evaluated.

STUDY DESIGN AND METHODS

Suspected TT-HCV cases reported to CBS in BC between August 28, 2002, and February 28, 2005, were analyzed. The incremental yield of plausible TTIs from PH-reported suspected TTIs was calculated. The effectiveness of LB and TB investigations was assessed with respect to the impact of improved anti-HCV donor screening, the number of newly recognized HCV infections, and the timeliness of initiating investigations.

RESULTS

Nine of 553 (1.6%) investigations were initiated after PH reporting, yielding an additional 2 of 237 (i.e., 0.8%) plausible TTIs. Ninety-two percent of investigations with transfused units involved transfusions before implementing second-generation anti-HCV enzyme immunoassay (EIA) donor screening. Almost one-third of HCV-infected persons in linked investigations (i.e., LB triggered by a TB and vice versa) were newly identified. Recently tested, PH-reported cases incurred a mean delay exceeding 6 months until initiating a LB or TB investigation.

CONCLUSION

PH reporting of TTIs and investigating transfusions after second-generation anti-HCV EIA donor screening identified few plausible TT-HCV infections. Many HCV-infected recipients or lapsed donors first became aware of their infection status as a result of CBS investigations. The current process of reporting suspected TTIs incurs significant time delay.

Current incidence and estimated residual risk of transfusion-transmitted infections in donations made to Canadian Blood Services

BACKGROUND

New testing methods such as nucleic acid amplification testing (NAT) and chemiluminescent serologic assays have been introduced, more precise estimates for infectious window periods are available, and a new method for estimating the residual risk (RR) of transfusion-transmitted infections (TTIs) has been developed. Thus, available RR estimates for Canada need to be updated.

STUDY DESIGN AND METHODS

Incidence rates for known TTI markers were determined for all allogeneic whole-blood donations made to Canadian Blood Services between 2001 and 2005; they were derived from NAT conversions or seroconversions of repeat donors with at least two donations in a 3-year period. RR estimates for human immunodeficiency virus (HIV)-1 and hepatitis C virus (HCV) derived from the classical incidence/window-period model were compared to those obtained by the new method that estimates incidence from NAT-positive, antibody-negative donations (NAT-yield cases) from all donors divided by person-years.

RESULTS

With the classical method, the RR of HIV (1 per 7.8 million donations) and HCV (1 per 2.3 million) were low; HBV RR was higher (1 per 153,000). HCV RR was significantly lower when estimated with the new method (1 per 13 million). Eleven HCV NAT-yield cases were predicted by applying the classical method to our seroconversion data but only 2 were observed (p = 0.011). Observed HIV-1 NAT-yield cases (n = 1) matched those predicted (n = 0.7).

CONCLUSION

New tests have reduced an already low risk of TTI in Canada. HCV RR estimates by two different methods differed but both were low.

Screening for Acute HIV Infection: Lessons Learned

Human immunodeficiency virus (HIV) nucleic acid testing is increasingly being used by researchers and public health screening programs to identify highly infectious, HIV antibody-negative individuals with acute HIV infection. We present cases to illustrate unusual instances of acute HIV screening, which include "window period" testing and the discovery of low-level HIV RNA.