Failure of routine HIV-1 tests in a case involving transmission with preseroconversion blood components during the infectious window period

Modeling the Risk of HIV Transfusion Transmission

BACKGROUND

Blood donations are routinely screened for HIV to prevent an infectious unit from being released to the blood supply. Despite improvements to blood screening assays, donations from infected donors remain undetectable during the window period (WP), when the virus has not yet replicated above the lower limit of detection (LOD) of a screening assay. To aid in the quantitative risk assessments of WP donations, a dose-response model describing the probability of transfusion-transmission of HIV over a range of viral RNA copies was developed.

METHODS

An exponential model was chosen based on data fit and parsimony. A data set from a HIV challenge study using a nonhuman primate model and another data set from reported human blood transfusions associated with HIV infected donors were separately fit to the model to generate parameter estimates. A Bayesian framework using No-U-Turn Sampling (NUTS) and Monte Carlo simulations was performed to generate posterior distributions quantifying uncertainty in parameter estimation and model predictions.

RESULTS

The parameters of the exponential model for both nonhuman primate and human data were estimated with a mean (95% credible intervals) of 2.70 × 10 -2 (7.74 × 10 -3 , 6.06 × 10 -2 ) and 7.56 × 10 -4 (3.68 × 10 -4 , 1.31 × 10 -3 ), respectively. The predicted ID 50 for the animal and human models was 26 (12, 90) and 918 (529, 1886) RNA copies transfused, respectively.

CONCLUSION

This dose-response model can be used in a quantitative framework to estimate the probability of transfusion-transmission of HIV through WP donations. These models can be especially informative when assessing risk from blood components with low viral load.

Personal Freedom and Public Responsibility: Remaining Questions after First Case of HIV Transmission via Blood Transfusion in North Serbia

The reduction in the risk of transfusion-transmissible infections (including HIV infection) is an essential part of transfusion patient care. Here, we report the first incident of HIV transmission via transfusion in north Serbia due to blood donor dishonesty, and the failure of the laboratory screen tests to detect the presence of HIV particles in his blood. Infected blood products were distributed to two recipients, and HIV infection was confirmed in one. This incident finally led to the implementation of Nucleic Acid Amplification Technology as mandatory testing of blood donors for HIV infection in Serbia and raised many questions related to the responsibility and ethics of all the participants in the blood transfusion supply chain. There is a need for the implementation of modern and non-discriminative laws in Serbia in order to reduce transfusion-transmissible infections. In addition, transfusion institutes in Serbia need to be obliged to pursue the constant upgrade of their diagnostic capacities in order to prevent similar incidents and to provide the best possible care for blood donation recipients.

Inactivation of a broad spectrum of viruses and parasites by photochemical treatment of plasma and platelets using amotosalen and ultraviolet A light

BACKGROUND

The INTERCEPT Blood System pathogen reduction technology (PRT), which uses amotosalen and ultraviolet A light treatment (amotosalen/UV-PRT), inactivates pathogens in plasma and platelet components (PCs). This review summarizes data describing the inactivation efficacy of amotosalen/UVA-PRT for a broad spectrum of viruses and parasites.

METHODS

Twenty-five enveloped viruses, six nonenveloped viruses (NEVs), and four parasites species were evaluated for sensitivity to amotosalen/UVA-PRT. Pathogens were spiked into plasma and PC at high titers. Samples were collected before and after PRT and assessed for infectivity with cell cultures or animal models. Log reduction factors (LRFs) were defined as the difference in infectious titers before and after amotosalen/UV-PRT.

RESULTS

LRFs of ≥4.0 log were reported for 19 pathogens in plasma (range, ≥4.0 to ≥7.6), 28 pathogens in PC in platelet additive solution (PC-PAS; ≥4.1-≥7.8), and 14 pathogens in PC in 100% plasma (PC-100%; (≥4.3->8.4). Twenty-five enveloped viruses and two NEVs were sensitive to amotosalen/UV-PRT; LRF ranged from >2.9 to ≥7.6 in plasma, 2.4 or greater to greater than 6.9 in PC-PAS and >3.5 to >6.5 in PC-100%. Infectious titers for four parasites were reduced by >4.0 log in all PC and plasma (≥4.9 to >8.4).

CONCLUSION

Amotosalen/UVA-PRT demonstrated effective infectious titer reduction for a broad spectrum of viruses and parasites. This confirms the capacity of this system to reduce the risk of viral and parasitic transfusion-transmitted infections by plasma and PCs in various geographies.

Evaluation of the diagnostic performance and optimal cutoff value of a fourth-generation ELISA, VIDAS HIV-1/2 Duo Ultra assay, in a low-prevalence country

In this study, we described the largest analysis to date conducted with VIDAS® HIV Duo Ultra assay. Additionally, we analyzed the diagnostic performance and cutoff values (TV) of HIV Duo Ultra assay and total cost analysis for HIV testing. Of 11,642 enzyme-linked immunosorbent assay (ELISA)-positive samples referred to our center for confirmation, 2000 were positive with HIV Duo Ultra, and of these, 87% were HIV-1 positive and 0.6% were HIV-1 indeterminate with the confirmatory test. Overall, the false-positivity rate was 1.75% for HIV Duo Ultra assay. The sensitivity and specificity were 100% and 99.1%, respectively, when the TV was set at the recommended cutoff value. Even increasing the cutoff value four times, sensitivity and specificity remained high, pointing out that a TV of 0.99 is highly indicative of HIV positivity. Retesting samples with HIV Duo Ultra assay decreased 80% of the confirmatory tests, revealing a significant decrease of 78% in the total costs and reporting time.

Applying strand displacement amplification to quantum dots-based fluorescent lateral flow assay strips for HIV-DNA detection

Up to now, the colloidal gold labeling immunochromatographic test strip is a mature and applicable technology. However, different from the conventional gold nanoparticle, quantum dot (QD) possesses larger specific surface area and better biocompatibility. So, as a novel nanomaterial, QD is capable of assembling more biomolecule which could enhance the sensitivity and accuracy of strips by rationality. Besides, strand displacement amplification was drawn into our test strips in this paper, this assumption made HIV-DNA recycling many times and converting it to plentiful QD-dsDNA (double-stranded deoxyribonucleic acid), where after these nano-structures would be captured by test zone. Meanwhile, the suggested scheme eliminated the hook effect owing to the target drop out of the incorporation on test zone, and any nucleotide sequence or substance which has aptamers can work as the target, such as carcinoembryonic antigen or mycotoxin. This assay realized the detection limit of as low as 0.76 pM (S/N = 3) and the detection range of 1 pM to 10 nM. In the end, we made use of this fluorescent lateral flow assay strips with great reproducibility for detecting HIV-DNA in human serum, that attested this method could be applied to practical application prospectively.

Nucleic acid testing: Is it the only answer for safe Blood in India?

Background:

With the implementation of NAT in countries around the world, there is a growing pressure on the transfusion services in India to adopt NAT testing. India has about 2545 licensed Blood Centres. The Transfusion Services in India are fragmented, poorly regulated and the quality standards are poorly implemented. Blood Centres are still dependent on replacement/family donors and in most places laboratory testing for Transfusion transmitted infections is not quality assured, laboratory equipment are not calibrated and maintained, and validation of results is not carried out. Against the current scenario introducing NAT for screening of blood donors in India would pose a challenge.

Aim:

To study the prudence of universal NAT testing in India.

Materials and Methods:

A retrospective study of 5 years from 2008-2012 was undertaken to study the true reactivity of donors using WHO strategy II and III and therefore the true seroprevalence of TTI infections in the donor populations.

Results:

The true reactivity of the donors was much less as compared to the initially reactive donors due to the use of a well designed testing algorithm. In addition having a total voluntary blood collection along with good pre-donation counseling program also reduces the transmission of infections.

Conclusions:

What India essentially needs to do is religiously implement the strategies outlined in the WHO Aide-memoire. The blood should be collected only from voluntary non remunerative and repeat donors, there should be stringent donor selection with pre-donation counseling instituted. Strict implementation of quality management system, development of well defined testing startegies and strong haemovigilance system could take us a step in the right direction.

Community-Based HIV-1 Early Diagnosis and Risk Behavior Analysis of Men Having Sex with Men in Hong Kong

The increasing prevalence of HIV-1 among men having sex with men (MSM) calls for an investigation of HIV-1 prevalence and incidence in MSM by early diagnosis to assist with early preventive interventions in Hong Kong. The participants were recruited randomly from MSM communities within a one-year period. Rapid HIV Test (RHT) and real-time dried blood spot (DBS)-based quantitative polymerase chain reaction (DBS-qPCR) were used for the early diagnosis of 474 participants. Risk behavior analysis was performed by studying information obtained from the participants during the study period. The HIV-1 prevalence and incident rates in the studied MSM population were 4.01% (19/474) and 1.47% (7/474), respectively. Three infected participants were found at the acute phase of infection by DBS-qPCR. Only 46.4% (220/474) MSM were using condoms regularly for anal sex. HIV infection significantly correlated with unprotected receptive anal sex and syphilis infection. An increased number of infections was found among foreign MSM in Hong Kong. This study is the first to use DBS-qPCR to identify acutely infected individuals in a community setting and to provide both the prevalence and incident rates of HIV-1 infection among MSM in Hong Kong. The risk analysis provided evidence that behavior intervention strengthening is necessary to fight against the increasing HIV-1 epidemic among MSM in Hong Kong and surrounding regions in Asia.

Screening of HIV infection: role of molecular and immunological assays

Due to technical improvements and new developments of immunological assays, the reliability of serological laboratory diagnosis of HIV infection has improved considerably and the residual risk, due to the diagnostic window for transfusion-transmitted HIV, has been reduced significantly. Through the addition of nucleic acid amplification tests (NAT) to blood donor screening, the residual risk can de further decreased by up to 50%, depending on the sensitivity of the NAT protocol and whether individual or pooled blood donations are screened. In-house and commercially available NAT have been implemented in blood banks as HIV only or multiplexed HIV and hepatitis B or C virus assays. As an alternative to separate antigen and antibody screening, combined fourth-generation assays have been developed in 1997, and have achieved a high degree of sensitivity and specificity. Thus, they can replace stand-alone antigen and third-generation antibody assays. While they are used in the routine diagnostics of HIV infection in many countries throughout the world, they probably represent no alternative for NAT in blood-donor screening in industrialized countries. In the next few years, technical improvements will further simplify NAT screening. While there is still some potential to improve the detection threshold of NAT, the sensitivity of the antigen module of fourth-generation assays (a lowest concentration of 3-5 pg of p24 antigen) is probably very close to its technical limit.

Light based anti-infectives: ultraviolet C irradiation, photodynamic therapy, blue light, and beyond

Owing to the worldwide increase in antibiotic resistance, researchers are investigating alternative anti-infective strategies to which it is supposed microorganisms will be unable to develop resistance. Prominent among these strategies, is a group of approaches which rely on light to deliver the killing blow. As is well known, ultraviolet light, particularly UVC (200-280 nm), is germicidal, but it has not been much developed as an anti-infective approach until recently, when it was realized that the possible adverse effects to host tissue were relatively minor compared to its high activity in killing pathogens. Photodynamic therapy is the combination of non-toxic photosensitizing dyes with harmless visible light that together produce abundant destructive reactive oxygen species (ROS). Certain cationic dyes or photosensitizers have good specificity for binding to microbial cells while sparing host mammalian cells and can be used for treating many localized infections, both superficial and even deep-seated by using fiber optic delivered light. Many microbial cells are highly sensitive to killing by blue light (400-470 nm) due to accumulation of naturally occurring photosensitizers such as porphyrins and flavins. Near infrared light has also been shown to have antimicrobial effects against certain species. Clinical applications of these technologies include skin, dental, wound, stomach, nasal, toenail and other infections which are amenable to effective light delivery.

Evaluation of serological transfusion-transmitted viral diseases and mutliplex nucleic acid testing in malaysian blood donors

BACKGROUND

Transmission of infectious diseases is a recognized complication of blood transfusion and blood products. Nucleic acid testing (NAT) may contribute to improved efficiency of blood screening and thereby increase the safety margin for transfused blood.

METHODS

Unscreened blood samples from 1388 randomized donors were selected for this study at the Transfusion Medicine Unit of Hospital Universiti Sains Malaysia (HUSM). Informed consent was obtained from all donors and blood samples were tested for HIV, HBV and HCV serologically and by NAT assay.

RESULTS

Of the 1,388 tested samples, 1,360 were non-reactive for both assays. Four samples (0.29%) were both serologically and NAT reactive. The remaining twenty-four samples were divided into two groups. Of these, five samples (0.366%) were NAT reactive and nineteen samples (1.37%) were serologically reactive. However, serology confirmation tests run on the latter nineteen samples were non-reactive.

CONCLUSIONS

Hence, NAT adds benefit of detecting "false positive" reactions via standard serology, the cost of administering NAT also need further consideration and study.

Translation of biomedical prevention strategies for HIV: prospects and pitfalls

Early achievements in biomedical approaches for HIV prevention included physical barriers (condoms), clean injection equipment (both for medical use and for injection drug users), blood and blood product safety, and prevention of mother-to-child transmission. In recent years, antiretroviral drugs to reduce the risk of transmission (when the infected person takes the medicines; treatment as prevention) or reduce the risk of acquisition (when the seronegative person takes them; preexposure prophylaxis) have proven to be efficacious. Circumcision of men has also been a major tool relevant for higher prevalence regions such as sub-Saharan Africa. Well-established prevention strategies in the control of sexually transmitted diseases and tuberculosis are highly relevant for HIV (ie, screening, linkage to care, early treatment, and contact tracing). Unfortunately, only slow progress is being made in some available HIV-prevention strategies such as family planning for HIV-infected women who do not want more children and prevention of mother-to-child HIV transmission. Current studies seek to integrate strategies into approaches that combine biomedical, behavioral, and structural methods to achieve prevention synergies. This review identifies the major biomedical approaches demonstrated to be efficacious that are now available. We also highlight the need for behavioral risk reduction and adherence as essential components of any biomedical approach.

Development and evaluation of reverse-transcription loop-mediated isothermal amplification for rapid detection of human immunodeficiency virus type 1

PURPOSE

The objective of this study was to establish a reverse-transcription loop-mediated isothermal amplification (RT-LAMP) method for rapid detection of human immunodeficiency virus type 1 (HIV-1).

MATERIALS AND METHODS

The HIV-1 integrase gene region was selected because it was a conserved part of the HIV-1 genome. Six primers specific to eight regions of the HIV-1 integrase gene were designed. A total of 171 samples (18 HIV-1 confirmed positive samples and 153 serum specimens were collected in this study) were tested by RT-LAMP and reverse-transcription polymerase chain reaction (RT-PCR). After amplification in an isothermal water bath for 45 min, samples containing HIV-1 generated the expected ladder-like products while other viruses generated no product.

RESULTS

The sensitivity and specificity of the RT-LAMP assay were evaluated by comparison with RT-PCR. The assay was significantly more sensitive than normal gel-based RT-PCR.

CONCLUSION

Because it is specific and simple, the RT-LAMP assay can be widely applied in clinical laboratories for rapid detection of HIV-1.

New tools in HCV diagnosis, in light of the enhanced awareness and the new drugs for treatment: SMARTube and stimmunology

With improved HCV therapy, challenges regarding HCV diagnosis, such as seronegative window period, false positive readings, and differentiation between recent, chronic, and resolved infections, are of increasing importance. To address these challenges an innovative device—SMARTube HIV & HCV—was used. Blood samples were tested for anti-HCV antibodies before and after incubation in the SMARTube, which promotes the in vitro stimulation of in vivo HCV primed lymphocytes, thus enhancing levels of anti-HCV antibodies. Comparing antibody levels, in concordant samples before and after SMARTube, yielded the Stimulation Index (SI). Among 5888 fresh blood samples, from various populations and regions worldwide, 641 were seropositive using plasma, while SMARTube processing (yielding enriched plasma, termed SMARTplasma) enabled diagnosis of 10 additional carriers in high-risk cohorts, that is, earlier detection. Using SMARTplasma eliminated all false positive results, using the current assays. In addition we show that SI calculation may serve as an important tool for differentiating between those who recently seroconverted, carriers of long-term infection, and those who have cleared the virus. SMARTube and the SI could lead to better, more informative diagnosis of HCV infections and play an important role in changing the way we treat both the infected individuals and the epidemic as a whole.

Babesia microti real-time polymerase chain reaction testing of Connecticut blood donors: potential implications for screening algorithms

BACKGROUND

Babesia microti, an intraerythrocytic parasite, has been implicated in transfusion transmission. B. microti seroprevalence in Connecticut (CT) blood donors is approximately 1%; however, it is not known what percentage of donors is parasitemic and poses a risk for transmitting infection. Therefore, we determined the prevalence of demonstrable B. microti DNA in donors from a highly endemic area of CT and compared observed rates with concurrent immunofluorescence assay (IFA) testing results.

STUDY DESIGN AND METHODS

Blood samples from consenting donors in southeastern CT were collected from mid-August through early October 2009 and tested by IFA for immunoglobulin G antibodies and real-time polymerase chain reaction (PCR) for B. microti DNA. IFA specificity was determined using blood donor samples collected in northwestern Vermont (VT), an area nonendemic for Babesia.

RESULTS

Of 1002 CT donors, 25 (2.5%) were IFA positive and three (0.3%) were real-time PCR positive. Among the three real-time PCR-positive donors, two were also IFA positive, while one was IFA negative and may represent a window period infection. The two IFA- and real-time PCR-positive donors appeared to subsequently clear infection. The other real-time PCR-positive donor did not provide follow-up samples. Of 1015 VT donors tested by IFA, only one (0.1%) was positive, but may have acquired infection during travel to an endemic area.

CONCLUSION

We prospectively identified several real-time PCR-positive blood donors, including an IFA-negative real-time PCR-positive donor, in an area highly endemic for B. microti. These results suggest the need to include nucleic acid testing in planned mitigation strategies for B. microti.

HIV Seroconversion in blood donors from the coordinating blood bank in the State of Pará

BACKGROUND

Transfusion of Human immunodeficiency virus (HIV) infected blood is probably the most effective means of transmission of this disease. Despite intense efforts and investment to ensure safety, transmission of HIV still remains a real possibility in the transfusion service due to the fact that routine laboratory tests in most Brazilian government blood banks rely on the detection of antibodies. This leaves an immunological window period of from 16 to 22 days, which could be minimized to approximately 9 to 11 days if nucleic acid amplification tests were employed in screening.

OBJECTIVE

To analyze the profile of blood donors who seroconverted to HIV positive from 2008 to 2010 in the coordinating blood bank of the State of Pará in respect to gender, age, marital status and educational level.

METHODS

HIV seroconversion cases of blood donors who donated on more than one occasion at the coordinating blood bank of the State of Pará were investigated. Records from 2008 and 2010 were analyzed in respect to gender, marital status, schooling and age.

RESULTS

Among the 157,432 donations in this period, 45 HIV seroconversions were confirmed. Of these, 95.56% were men, of which 86.67% were single, 53.33% had completed high school and 40% were between 23 and 29 years old.

CONCLUSIONS

In order to improve the quality of blood and reduce the residual risk of HIV transmission in blood banks, it is necessary to know the profiles of donors who most frequently seroconvert and use nucleic acid amplification tests as routine screening.

An integrated chip capable of performing sample pretreatment and nucleic acid amplification for HIV-1 detection

This study reports on a microfluidic system equipped with a sample pretreatment device and a nucleic acid amplification device for the rapid diagnosis of the human immunodeficiency virus-1 (HIV-1). The system analyzed proviral deoxyribonucleic acid (DNA) from an HIV-infected Jurkat T cell line. In order to ensure accurate diagnosis among other prevalent B-type strains, simultaneous detections of four conserved HIV-1 B-type DNA fragments were performed in this integrated microfluidic system. The entire protocol including cell lysis, extraction of DNA, polymerase chain reaction (PCR), and optical detection were successfully integrated in order to perform a rapid, automated diagnosis. Experimental results showed that four primer sets with conserved HIV-1 B-type sequences specific for the 167-bp RU5 promoter region, the 424-bp int, the 117-bp tat, and the 162-bp vpr coding regions were successfully amplified from the respective regions of the proviral DNA, even from a single infected cell. This accurate real-time detection was achieved within 95 min using the integrated optical system.

Residual risk of transfusion-transmitted infection with human immunodeficiency virus, hepatitis C virus, and hepatitis B virus in Korea from 2000 through 2010

BACKGROUND

Despite screening blood donations with advanced technologies and improved donor screening, the risk of transfusion-transmitted infections persists. This risk is mainly due to blood donations collected during the window period. A precise estimate of the transfusion risk of viral infection will help to determine the effect of new and current safety measures and to prioritize and allocate limited resources. Therefore, we estimated the risk of transfusion-transmitted viral infection in blood donations collected in Korea from 2000 to 2010.

METHODS

Blood donations collected at 16 blood centers were tested for HIV, HCV, and HBV to estimate the residual risk of transfusion-transmitted viral infection. The residual risk was calculated in two-year periods using the incidence/window model. The incidence rates for HIV/HCV and the confirmed positive rate for HIV/HCV in first-time and repeat donors were compared.

RESULTS

The residual risks for HIV in 2004/2005 and 2009/2010 were 1 in 1,080,244 and 1 in 1,356,547, respectively. The risks for HCV in 2000/2001 and 2009/2010 were 1 in 81,431 and 1 in 2,984,415, and the risks for HBV in 2000/2001 and 2009/2010 were 1 in 45,891 and 1 in 43,666. These estimates indicate that the residual risks for HCV in Korea have declined 36.6-fold, and those for HIV and HBV have not improved significantly, compared to previous estimates. The odds ratios for HCV and HBV positivity in first-time donors compared to repeat donors were 11.8 and 19.6, respectively.

CONCLUSIONS

The residual risk of HCV declined over the last decade due to improved screening reagents, implementation of the nucleic acid amplification test, and tight application of strict donor selection procedures. Current residual risk estimates for HIV and HCV in Korea are extremely low, but the risk for HBV is still high; therefore, urgent measures should focus on decreasing the residual risk of HBV. Despite the introduction of more sensitive assays in blood screening, several other factors may influence the actual residual risk of transfusion-transmitted infection. A continuous monitoring of residual risk of transfusion-transmitted infection is crucial in managing blood safety.

Trends in prevalence, incidence, and residual risk of major transfusion-transmissible viral infections in United Arab Emirates blood donors: impact of individual-donation nucleic acid testing, 2004 through 2009

BACKGROUND

United Arab Emirates (UAE) has a heterogeneous population consisting of more than 160 nationalities and 85% of the population being non-UAE. In 2007, Dubai Blood Donation Centre (DBDC), the major local supplier of blood in the UAE, introduced six-minipool nucleic acid test (NAT) for hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV), which in 2008 upgraded to individual-donation (ID)-NAT. The aim of this study was to analyze the efficacy of the donor screening program in the UAE and evaluate the impact of NAT on the yield and residual risk of transfusion-transmissible viral infections (TTVIs).

STUDY DESIGN AND METHODS

A total of 169,781 blood donations collected at DBDC between 2004 and 2009 were screened for TTVIs. During the period 2008 through 2009, a total of 59,283 donations were tested with both ID-NAT and serologic assays. The incidence, prevalence, and residual risk for each viral agent were estimated and analyzed.

RESULTS

The individual prevalences of HBV, HCV, and HIV per 100,000 donation were 234.4, 110, and 4, respectively. Calculated residual risk per million donations for HBV was decreased from 1.41 in pre-NAT period to 0.92 in post-NAT period. These figures were decreased for HCV and HIV from 1.73 and 0.39 to 0 and 0.32, respectively.

CONCLUSION

Incidence rates and estimated residual risk indicate that the current risk of TTVIs attributable to blood donation is relatively low in the UAE. The study recommends the parallel use of both serology and ID-NAT TTVIs screening in blood donations and suggests the exclusion of antibody to hepatitis B core antigen-positive donations as this can eliminate the potential infectivity of these units with marginal effects on the blood stock in UAE.

Case report of a haemovigilance investigation using phylogenetic analysis of HIV-1 in Brazil

OBJECTIVES

The aim of this work is to provide the first report of a transfusion-acquired HIV-1 infection and to verify transmission from the donor to the recipients using phylogenetic analysis of HIV-1 DNA sequences in a Brazilian blood bank.

BACKGROUND

Although haemovigilance procedures based on phylogenetic analysis of HIV have been reported in several countries, this type of study has yet to be conducted in Latin America.

MATERIALS AND METHODS

Upon identifying a HIV-1-positive repeat blood donor by enzyme immunoassay (EIA) blood screening, all recipients of the donor's previous donation were identified and tested for HIV-1 by EIA, nucleic acid amplification test and HIV-1 DNA sequencing and phylogenetic analysis.

RESULTS

One of the recipients tested positive for HIV-1. The phylogenetic analysis showed a high genetic similarity among the viruses, thus supporting the hypothesis of transmission from the donor to the recipient.

CONCLUSIONS

Phylogenetic analysis of HIV-1 DNA sequences has been a decisive tool in verifying suspected transmission of the virus from blood donor to recipient in Brazil.

Genomic detection of human immunodeficiency virus (HIV) by nucleic acid amplification test in a frequent platelet donor during the pre-seroconversion period

Since serological donor-screening tests for HIV were introduced in 1985, the safety of donated blood components has improved dramatically. However, these tests do not completely prevent the risk of transfusion-associated HIV infection related to the use of blood donated during the pre-seroconversion window period. Testing based on nucleic acid amplification is being implemented to screen for HIV-infected blood donated during this period, which has reduced the probability of transmitting HIV through transfusion by shortening the window period. This article describes a case of acute HIV-1 infection, detected using a nucleic acid amplification test (NAT) in a repeat blood donor who donated during the pre-seroconversion window period and whose antigen and anti-HIV antibody expression was observed after molecular marker detection. In addition, the possible route of infection is discussed based on the patient's history, and finally, the need for NAT technology for blood donor screening is emphasized.

Why implement universal leukoreduction?

The improvement of transfusion medicine technology is an ongoing process primarily directed at increasing the safety of allogeneic blood component transfusions for recipients. Over the years, relatively little attention had been paid to the leukocytes present in the various blood components. The availability of leukocyte removal (leukoreduction) techniques for blood components is associated with a considerable improvement in various clinical outcomes. These include a reduction in the frequency and severity of febrile transfusion reactions, reduced cytomegalovirus transfusion-transmission risk, the reduced incidence of alloimmune platelet refractoriness, a possible reduction in the risk of transfusion-associated variant Creutzfeldt-Jakob disease transmission, as well as reducing the overall risk of both recipient mortality and organ dysfunction, particularly in cardiac surgery patients and possibly in other categories of patients. Internationally, 19 countries have implemented universal leukocyte reduction (ULR) as part of their blood safety policy. The main reason for not implementing ULR in those countries that have not appears to be primarily concerns over costs. Nonetheless, the available international experience supports the concept that ULR is a process that results in improved safety of allogeneic blood components.

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.

Early detection of human immunodeficiency virus type 1-specific B-lymphocyte-derived antibodies in a high-risk population

Diagnosis of acute human immunodeficiency virus (HIV) infection, a key driver of the HIV epidemic, remains a public health challenge. The PlasmAcute technology offers an opportunity to detect early anti-HIV antibody responses. B lymphocytes (B cells) were isolated from the blood of seronegative miners in South Africa by using the PlasmAcute method. B-cell lysates and paired sera were tested for anti-HIV-1 antibodies by two different enzyme-linked immunosorbent assays; immunoreactivity was confirmed by Western blotting. All volunteers were tested for HIV type 1 (HIV-1) viral load, p24 antigen, and CD4 count. Sera from HIV-seronegative men who had positive viral loads and were positive for p24 antigen were retested for anti-HIV antibodies after immune complex dissociation. Anti-HIV antibodies were detected in lysates from 16/259 subjects without immunoreactivity in paired sera. Four subjects, one of whom had a positive viral load initially, subsequently seroconverted. Six subjects showed transient anti-HIV-1 antibodies in the lysates and tested negative for all markers at the follow-up. Five subjects without follow-up data initially had lysate-positive/serum-negative samples, and these cases were classified as inconclusive. One subject had lysate antibodies and a detectable viral load but was seronegative at follow-up. In conclusion, lysate-derived anti-HIV-1 B-cell antibodies can be detected prior to seroconversion and earlier than or contemporary with HIV-1 RNA detection.

High specific infectivity of plasma virus from the pre-ramp-up and ramp-up stages of acute simian immunodeficiency virus infection

To define the ratio of simian immunodeficiency virus (SIV) RNA molecules to infectious virions in plasma, a ramp-up-stage plasma pool was made from the earliest viral RNA (vRNA)-positive plasma samples (collected approximately 7 days after inoculation) from seven macaques, and a set-point-stage plasma pool was made from plasma samples collected 10 to 16 weeks after peak viremia from seven macaques; vRNA levels in these plasma pools were determined, and serial 10-fold dilutions containing 1 to 1,500 vRNA copies/ml were made. Intravenous (i.v.) inoculation of a 1-ml aliquot of diluted ramp-up-stage plasma containing 20 vRNA copies infected 2 of 2 rhesus macaques, while for the set-point-stage plasma, i.v. inoculation with 1,500 vRNA copies was needed to transmit infection. Further, when the heat-inactivated set-point-stage plasma pool was mixed with ramp-up-stage virions, infection of inoculated macaques was blocked. Notably, 2 of 2 animals inoculated with 85 ml of a pre-ramp-up plasma pool containing <3 SIV RNA copies/ml developed SIV infections characterized by high levels of viral replication, demonstrating that "vRNA-negative" plasma collected from macaques in the pre-ramp-up stage is infectious. Furthermore, there is a high ratio of infectious virions to total virions in ramp-up-stage plasma (between 1:1 and 1:10) and a lower ratio in set-point-stage plasma (between 1:75 and 1:750). Heat-inactivated chronic-stage plasma can "neutralize" the highly infectious ramp-up-stage virions. These findings have implications for the understanding of the natural history of SIV and human immunodeficiency virus infection and transmission.

Experience of German Red Cross blood donor services with nucleic acid testing: results of screening more than 30 million blood donations for human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus

BACKGROUND

The risk of transfusion-transmitted human immunodeficiency virus-1 (HIV-1), hepatitis C virus (HCV), and hepatitis B virus (HBV) infections is predominantly attributable to donations given during the early stage of infection when diagnostic tests may fail. In 1997, nucleic acid amplification technique (NAT)-testing was introduced at the German Red Cross (GRC) blood donor services to reduce this diagnostic window period (WP).

STUDY DESIGN AND METHODS

A total of 31,524,571 blood donations collected from 1997 through 2005 were screened by minipool NAT, predominantly with pool sizes of 96 donations. These donations cover approximately 80 percent of all the blood collected in Germany during that period. Based on these data, the WP risk in the GRC blood donor population was estimated by using a state-of-the-art mathematic model.

RESULTS

During the observation period, 23 HCV, 7 HIV-1, and 43 HBV NAT-only-positive donations were detected. On the basis of these data and estimated pre-NAT infectious WPs, the residual risk per unit transfused was estimated at 1 in 10.88 million for HCV (95% confidence interval [CI], 7.51-19.72 million), 1 in 4.30 million for HIV-1 (95% CI, 2.39-21.37 million), and 1 in 360,000 for HBV (95% CI, 0.19-3.36 million). Based on observed cases of breakthrough infections, the risk of transfusion-related infections may be even lower.

CONCLUSION

The risk of a blood recipient becoming infected with HCV, HIV-1, or HBV has reached an extremely low level. Introduction of individual donation testing for HCV and HIV-1 would have a marginal effect on interception of WP donations.

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.

Primary screening of blood donors by nat testing for HCV-RNA: development of an "in-house" method and results

An "in-house" RT-PCR method was developed that allows the simultaneous detection of the RNA of the Hepatitis C Virus (HCV) and an artificial RNA employed as an external control. Samples were analyzed in pools of 6-12 donations, each donation included in two pools, one horizontal and one vertical, permitting the immediate identification of a reactive donation, obviating the need for pool dismembering. The whole process took 6-8 hours per day and results were issued in parallel to serology. The method was shown to detect all six HCV genotypes and a sensitivity of 500 IU/mL was achieved (95% hit rate). Until July 2005, 139,678 donations were tested and 315 (0.23%) were found reactive for HCV-RNA. Except for five false-positives, all 310 presented the corresponding antibody as well, so the yield of NAT-only donations was zero, presenting a specificity of 99.83%. Detection of a window period donation, in the population studied, will probably demand testing of a larger number of donations. International experience is showing a rate of 1:200,000 - 1:500,000 of isolated HCV-RNA reactive donations.

Fast and sensitive quantitative detection of HIV DNA in whole blood leucocytes by SYBR green I real-time PCR assay

The aim of this study was the development of a real-time PCR for HIV DNA quantification in whole blood leucocytes providing an alternative assay to those already described, almost based on the gag gene detection. The technique (pbs-rtPCR assay) is more rapid (the whole assay required less than 5h), easy to perform, omitting both PBMC purification step and data normalization to a housekeeping gene, when compared to previously published assays. Our method is able to detect all group M HIV-1 subtypes in the highly conserved primer-binding site (PBS) region and to avoid the interference by retroviral endogenous sequences in HIV DNA quantification. The sensitivity was 100% for 2 copies even in the presence of high amounts of genomic DNA (1 microg). To monitor the HIV DNA level in all possible clinical conditions, the assay has been validated and compared with a previously developed gag-PCR assay on 73 HIV-1 HAART-treated patients with a plasma HIV-1 RNA range from <50 to >500,000 copies/ml. The 50% of the samples with a viremia below the limit of detection (50 copies/ml) was found to contain HIV DNA between 2 and 10 copies/microg DNA. The pbs-rtPCR offers a significant improvement in the percentage of quantitatively detectable sample (99%) compared with the gag-PCR (42%) suggesting caution in the choice of HIV DNA assay.

Analytical and clinical sensitivity of the Procleix Ultrio HIV-1/HCV/HBV assay in samples with a low viral load

BACKGROUND AND OBJECTIVES

The Procleix Ultrio human immunodeficiency virus type 1 (HIV-1)/hepatitis C virus (HCV)/hepatitis B virus (HBV) (Ultrio) assay simultaneously detects HIV-1 RNA, HCV RNA and HBV DNA in individual blood donations. The main objective of the study was to assess the analytical and clinical sensitivity of the multiplex and discriminatory probe assays in samples with a low viral load.

MATERIAL AND METHODS

The VQC HIV RNA genotype B, HCV RNA genotype 1 and HBV DNA genotype A standard dilutions were tested in 26 repeats. The probability of detection by Ultrio was compared with previously obtained data of the Procleix Duplex HIV-1/HCV assay on the same reference panels. A selection of 121 anti-HIV-1, 138 anti-HCV and 190 HBsAg positive samples from patients receiving antiviral therapy were tested. The majority of patient samples had a viral load below the detection limit of the diagnostic nucleic acid test assays, which made them suitable to evaluate the performance of the multiplex and discriminatory assays on yield cases with a similar low viral load.

RESULTS

The 95% and 50% detection end-points of the Ultrio assay along with the corresponding 95% confidence intervals are 53.7 (32.9-117.2) and 8.6 (6.2-12.1) geq/ml for HIV-1 RNA, 30.3 (19.0-62.4) and 5.2 (3.7-7.2) geq/ml for HCV RNA and 393.7 (147.9-6978) and 54.5 (22.4-143.8) geq/ml for HBV DNA. The analytical sensitivity of Ultrio expressed as a potency factor relative to previously obtained Duplex results on the same HIV-1 RNA and HCV-RNA standard dilutions was 1.09 (0.20-6.10) and 1.11 (0.21-5.89), respectively. The assay detected all 22 HIV-1 infected patients with viral load > 50 copies/ml, and 41 of 99 patients (41%) with viral load < 50 copies/ml, of which 23 (56%) were detected by the discriminatory assay. All 47 patients with HCV RNA load > 521 IU/ml and 10/91 polymerase chain reaction-negative patients with viral load < 50 IU/ml tested positive in Ultrio assay of which five were missed in the discriminatory test. The assay detected 53/55 HBV infected patients (96%) with viral load > 250 copies/ml and 108/135 patients (80%) with viral load < 250 copies/ml of which 17 (16%) were missed by the discriminatory test.

CONCLUSIONS

The new Procleix Ultrio assay is as sensitive as the Procleix Duplex assay for HIV-1 and HCV detection meeting the requirements of universal guidelines. The ability of the assay to detect HBV DNA in low viral load samples could be useful for screening blood. Inevitable negative results of discriminatory probe assays caused by stochastic sample variation will reduce the chance of recognizing low viraemic blood donors detected by individual donation nucleic acid test.

Reverse transcriptase viral load correlates with RNA in SIV/SHIV-infected macaques

Monitoring of viral load in macaques has usually been carried out using in-house PCR-based methods. A novel viral load (VL) kit (ExaVir Load) based on the measurement of lentivirus reverse transcriptase (RT) activity provides a potential alternative to methods that measure plasma viral RNA. RT is a fundamental and conserved activity of all retroviruses and the method should theoretically detect RT from all lentiviruses. To test this we compared VL measured by a commercially available RT kit with an in-house QC RT-PCR in macaques infected with SIV and SHIV. Both RT and RNA levels were measured over time in both sets of macaques. Results indicated that the relationship between both tests was strong for SIV and SHIV (r = 0.95 and r = 0.92, p < 0.0001, respectively). The VL trends also followed each other, indicating that both techniques measured the same process of viral replication. Furthermore, the RT load obtained using standardized control plasma samples supplied by NIBSC gave values close to the designated VL. However, when comparing RT load with QC RT-PCR a consistently three to five time higher level was obtained with the RT assay, highlighting potential differences in assay calibration. Even so, the data suggest that the RT assay is both sensitive and robust for use in the SIV/SHIV macaque model, particularly where molecular-based assays for SIV VL determinations are not easily available. The assay is also a commercially available kit and hence has the potential to reduce the variability seen between laboratories using in-house PCR.

Molecular analysis of HIV strains from a cluster of worker infections in the adult film industry, Los Angeles 2004

OBJECTIVES

In April 2004, 13 susceptible women were exposed to a single acutely HIV-1-infected man while employed to perform various sex acts for the production of adult films; three women were subsequently found to have acquired HIV infection (23% attack rate). As part of the investigation of this infection cluster, we evaluated whether viral strains collected from infected individuals were significantly related.

METHODS

We determined nucleotide sequences from the C2V3C3 and gp41 region of env and the p17 region of gag in viruses from the three infected individuals from whom specimens were available. We then compared these sequences phylogenetically to comparable sequences from available reference strains. Genotypic and phenotypic antiretroviral drug resistance was determined for plasma virus from the male index case and one female contact at a separate commercial laboratory.

RESULTS

The env and gag sequences of the HIV strains from the male index case and two of the infected women were 100% similar. Genotyping of the male index case's virus identified 12 mutations, which represented known naturally occurring polymorphisms in the subtype B consensus sequence that are not associated with antiretroviral drug resistance. Genotyping of the virus from the female contact identified 10 mutations, all of which were shared by the virus from the male index case. Phenotyping demonstrated that both viruses were susceptible to all antiretroviral drugs tested.

CONCLUSION

Molecular and virological data strongly support the epidemiological conclusion that these women were infected with an identical strain of HIV through occupational exposure to an individual with an acute HIV infection.

Transfusion Safety: Where Are We Today?

Over the past decades, the incidence of clinically significant transfusion-transmitted diseases has been dramatically reduced. These reductions have occurred because of a multifocal approach to the collection, processing, and release of blood and blood components. Research has focused on characterizing specific pathogens and their infectious patterns, especially the early viremic phase. Donor motivation and characteristics have been investigated, and restrictive eligibility criteria have been established. Regulatory oversight has been strengthened in the United States and hemovigilance systems established in many countries of the European Union, Canada, and Japan to identify new and emerging infectious and noninfectious transfusion risks. Such systems are required because many emerging pathogens will elude the stringent and sensitive donor testing already in place which, unfortunately, requires advanced technologies. Despite the remarkable progress, the processes of delivering a transfusion to a patient provide additional opportunity for risk, but have been less- well studied and the solutions have been less-well defined. Specific areas of concern include the collection and correct identification of patient samples, selection of modified or unique products, blood administration process, and establishment of specific indications for transfusion. In this chapter, we review the status of transfusion safety in the United States and discuss some emerging infectious and noninfectious risks of transfusion that will become future areas for basic and translational research. The disparities that exist in blood safety in developing countries' red cell alloimmunization and autoimmunity will not be covered.

Evaluation of an automated high-volume extraction method for viral nucleic acids in comparison to a manual procedure with preceding enrichment

BACKGROUND AND OBJECTIVES

Nucleic acid extraction still harbours the potential for improvements in automation and sensitivity of nucleic acid amplification technology (NAT) testing. This study evaluates the feasibility of a novel automated high-volume extraction protocol for NAT minipool testing in a blood bank setting.

MATERIALS AND METHODS

The chemagic Viral DNA/RNA Kit special for automated purification of viral nucleic acids from 9.6 ml of plasma by using the chemagic Magnetic Separation Module I was investigated. Analytical sensitivity for hepatitis C virus (HCV), human immunodeficiency virus-1 (HIV-1), hepatitis B virus (HBV), hepatitis A virus (HAV) and parvovirus B19 (B19) was compared to our present manual procedure that involves virus enrichment by centrifugation.

RESULTS

Chemagic technology allows automation of the viral DNA/RNA extraction process. Viral nucleic acids were bound directly to magnetic beads from 9.6-ml minipools. By combining the automated magnetic beads-based extraction technology with our in-house TaqMan polymerase chain reaction (PCR) assays, 95% detection limits were 280 IU/ml for HCV, 4955 IU/ml for HIV-1, 249 IU/ml for HBV, 462 IU/ml for HAV and 460 IU/ml for B19, calculated for an individual donation in a pool of 96 donors. The detection limits of our present method were 460 IU/ml for HCV, 879 IU/ml for HIV-1, 90 IU/ml for HBV, 203 IU/ml for HAV and 314 IU/ml for B19.

CONCLUSIONS

The 95% detection limits obtained by using the chemagic method were within the regulatory requirements for blood donor screening. The sensitivities detected for HCV, HBV, HAV and B19 were found to be in a range similar to that of the manual purification method. Sensitivity for HIV-1, however, was found to be inferior for the chemagic method in this study.

Protecting the blood supply from emerging pathogens: the role of pathogen inactivation

Although the risk of infection by blood transfusion is relatively low, breakthrough infections still occur, Transfusion-related fatalities caused by infections continue to be reported, and blood is not tested for many potentially dangerous pathogens. The current paradigm for increasing the safety of the blood supply is the development and implementation of laboratory screening methods and restrictive donor criteria. When considering the large number of known pathogens and the fact that pathogens continue to emerge, it is clear that the utility of new tests and donor restrictions will continue to be a challenge when considering the cost of developing and implementing new screening assays, the loss of potential donors, and the risk of testing errors. Despite improving the safety of blood components, testing remains a reactive approach to blood safety. The contaminating organisms must be identified before sensitive tests can be developed. In contrast, pathogen inactivation is a proactive strategy designed to inactivate a pathogen before it enters the blood supply. Almost all pathogen inactivation technologies target nucleic acids, allowing for the inactivation of a variety of nucleic acid-containing pathogens within plasma, platelets, or red blood cells thus providing the potential to reduce transfusion-transmitted diseases. However, widespread use of a pathogen inactivation technology can only be realized when proven safe and efficacious and not cost-prohibitive.

A new strategy for estimating risks of transfusion-transmitted viral infections based on rates of detection of recently infected donors

BACKGROUND

Estimates for human immunodeficiency virus (HIV)-1 and hepatitis C virus (HCV) transfusion-transmitted risks have relied on incidence derived from repeat donor histories and imprecise estimates for infectious, preseroconversion window periods (WPs).

STUDY DESIGN AND METHODS

By use of novel approaches, WPs were estimated by back-extrapolation of acute viral replication dynamics. Incidence was derived from the yield of viremic, antibody-negative donations detected by routine minipool nucleic acid testing (MP-NAT) of 37 million US donations (1999-2002) or from sensitive/less-sensitive HIV-1 enzyme immunoassay (S/LS-EIA) results for seropositive samples from 6.5 million donations (1999). Incidences and WPs were combined to calculate risks and project yield of individual donation (ID)-NAT.

RESULTS

The HIV-1 WP from presumed infectivity (1 copy/20 mL) to ID-NAT detection was estimated at 5.6 days, and the periods from ID to MP-NAT detection and from MP-NAT to p24 detection at 3.4 and 6.0 days, respectively; corresponding estimates for HCV were 4.9, 2.5, and 50.9 days (the latter represents period from MP-NAT to HCV antibody detection). The HIV-1 incidence projected from MP-NAT yield or from S/LS-EIA data was 1.8 per 100,000 person-years, resulting in a corresponding HIV-1 transfusion-transmitted risk of 1 in 2.3 million. The HCV incidence from MP-NAT yield was 2.70 per 100,000 person-years with a corresponding risk of 1 in 1.8 million donations. Conversion from MP-NAT to ID-NAT was projected to detect two to three additional HIV-1 and HCV infectious units annually.

CONCLUSIONS

MP-NAT yield and S/LS-EIA rates can accurately project transfusion risks. HCV and HIV-1 risks, currently estimated at 1 per 2 million units, could be reduced to 1 in 3 to 4 million units by ID-NAT screening.

Towards the prevention of transfusion-transmitted infectious diseases

Transfusion-transmission of viral infections, such as HIV and hepatitis C virus, were once the scourge of blood transfusion. However, due to remarkable progress over the last 30 years, tests for viral proteins, antibody responses and more recently, viral nucleic acids, have virtually eliminated these risks. This review summarizes these advances in an historical context, describes new methodologies on the horizon, and discusses residual infectious risks associated with blood transfusion.

Optimizing platelet transfusion therapy

Platelet transfusions are widely used. Prophylactic transfusions are employed in severely thrombocytopenic patients without evidence of bleeding, but no randomized trial data prove the safety or efficacy of this approach. Randomized trials have demonstrated the equivalence of transfusion triggers of 10,000 and 20,000/microl for prophylactic transfusions. The former threshold is potentially safer for the patient, conservative of donor resources and leads to lower costs, with perhaps a slightly greater risk of minor hemorrhage. Randomized trials have demonstrated the equivalence of pheresis or whole blood-derived platelet transfusions. The former present a lower risk for infectious agents, and the latter are less expensive and a more efficient use of limited donor resources. Randomized trials prove that leukoreduced and ABO identical platelet transfusions reduce the risks of HLA alloimmunization and platelet transfusion refractoriness (both leukoreduction and ABO matching), transfusion reactions (leukoreduction) and CMV transmission (leukoreduction). Leukoreduction and ABO matching of platelet transfusions also have been associated in preliminary observational studies with reduced morbidity and mortality in surgical patients and reduced infections in patients with leukemia. These results require further investigation. Future challenges include (1) determining the best approach to bacterial contamination of platelets, whether by detection methods or pathogen inactivation and (2) determining the threshold for prophylactic platelet transfusions in thrombocytopenic patients undergoing surgery or invasive procedures.

HIV in Singapore--past, present, and future

The first case of HIV infection in Singapore was reported in 1985. Between 1991 and 1998, the number of reported cases of HIV and AIDS increased rapidly before stabilizing from 1999. The epidemiology of the AIDS epidemic in Singapore is characterized by a predominance of male cases (seven to one) and heterosexual transmission. A multipronged control program comprising public education and education of high-risk groups, legislation, protection of the national blood supply, management of cases, and epidemiological surveillance has been put in place. The promotion of condom use among local sex workers has been fairly successful, with very low rates of HIV and other sexually transmitted infections (STIs). However, freelance and potential indirect sex workers such as masseuses and lounge hostesses are a concern in view of their higher prevalence of HIV and STIs. Another concern is the high proportion of cases who are diagnosed only when they develop AIDS. A better understanding of sexual networks among men who have sex with men will enable more effective intervention programs for this group. Fresh innovative approaches are needed to encourage safe sex practices and early screening.

Window-period human immunodeficiency virus transmission to two recipients by an adolescent blood donor

BACKGROUND

Pooled NAT and donor screening have reduced the diagnostic window period for HIV in the blood donor population to approximately 10 to 15 days. This report describes two cases of transfusion-acquired HIV infection and verification of transmission from the donor to the recipients, and attempts to identify how the 18-year-old donor acquired her infection.

STUDY DESIGN AND METHODS

After a repeat donor had a positive HIV test result, two recipients of the donor's previous donation were identified and tested. The donor and recipients were interviewed and blood samples were obtained for HIV DNA sequencing and phylogenetic analysis.

RESULTS

The two recipients had positive HIV test results. Phylogenetic analysis showed a high genetic similarity among the viruses (bootstrap 100%), consistent with transmission from the donor to the recipients. Four of five men with whom the donor had sexual contact during the critical time period when infection most likely occurred were located and tested; results were negative for HIV.

CONCLUSIONS

Pooled NAT of blood donations has not eliminated the window period for HIV identification during seroconversion.

Failure and success of HIV tests for the prevention of HIV-1 transmission by blood and tissue donations

French blood banks recently implemented nucleic acid testing (NAT) of all blood donations to reduce the risk of HIV transmission during the pre-seroconversion period. For tissue donation, HIV infection screening relies on HIV p24 antigen and anti-HIV-1 and 2 antibody detection. In this report, two related cases of infectious donations are described from a cornea donor during the preseroconversion window who was infected by an HIV antibody and NAT negative blood donor. After investigation, the blood donor was found to be herself in the preseroconversion window. Two months after donation, she was found to be HIV positive. The residual risk of HIV infectious blood donations since NAT has been introduced is estimated to be lower than one out of 2.5 millions. Individual NAT instead of minipool testing would not increase significantly the blood transfusion safety. In contrast, introduction of NAT should be considered to increase tissue donation safety as soon as such screening will be possible technically.

First report of human immunodeficiency virus transmission via an RNA-screened blood donation

BACKGROUND AND OBJECTIVES

Blood banks in the USA have recently introduced minipool nucleic acid amplification testing (MP-NAT) of blood products to reduce the transmission of human immunodeficiency virus (HIV) and hepatitis C virus (HCV) by transfusions. However, MP-NAT is limited in its ability to detect preseroconversion samples with very low viral RNA loads.

MATERIALS AND METHODS

To determine whether a red blood cell unit, from an MP-NAT-negative donation, transmitted HIV when transfused to a patient, we compared the viral sequences from the blood donor and recipient. The implicated donation was also tested by commercially available NAT assays at a range of dilution factors to determine whether the infectious unit could have been detected using individual-donation NAT (ID-NAT).

RESULTS

Phylogenetic linkage of HIV sequences in the blood donor and recipient confirmed the transmission of HIV by blood transfusion, the first such case identified since introduction of MP-NAT screening in 1999. Viral RNA was reliably detected by ID-NAT, but only inconsistently detected by MP-NAT.

CONCLUSIONS

Even following the introduction of MP-NAT, a preseroconversion donation with a viral load of <or= 150 copies of RNA/ml went undetected and resulted in an HIV transmission. Implementation of ID-NAT will further reduce such rare transmissions, but at a considerable cost per infectious unit interdicted.