Dengue Virus Immunity Increases Zika Virus-Induced Damage during Pregnancy.

Zika virus (ZIKV) has recently been associated with birth defects and pregnancy loss after maternal infection. Because dengue virus (DENV) and ZIKV co-circulate, understanding the role of antibody-dependent enhancement in the context of pregnancy is critical. Here, we showed that the presence of DENV-specific antibodies in ZIKV-infected pregnant mice significantly increased placental damage, fetal growth restriction, and fetal resorption. This was associated with enhanced viral replication in the placenta that coincided with an increased frequency of infected trophoblasts. ZIKV-infected human placental tissues also showed increased replication in the presence of DENV antibodies, which was reversed by FcγR blocking antibodies. Furthermore, ZIKV-mediated fetal pathogenesis was enhanced in mice in the presence of a DENV-reactive monoclonal antibody, but not in the presence of the LALA variant, indicating a dependence on FcγR engagement. Our data suggest a possible mechanism for the recent increase in severe pregnancy outcomes after ZIKV infection in DENV-endemic areas.

Patterns of Antibody Response to Severe Acute Respiratory Syndrome Coronavirus 2 Among 1.6 Million Blood Donors: Impact of Vaccination, United States, December 2020-June 2021.

From December 2020 to June 2021, 1654487 blood donors were tested for antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) S1 protein, and 1028547 (62.17%) were reactive. A rapid increase in prevalence was due to vaccination. Among a subset of 1567446 donors, 729771 (46.56%) reported SARS-CoV-2 vaccination, of whom 633769 (86.84%) were S1-antibody reactive only in response to vaccination and 68269 (9.35%) were reactive to both S1 and nucleocapsid in response to prior infection; the remainder were not reactive to either antibody. Among the 837675 (53.44%) donors who did not report vaccination, 210022 (25.07%) had reactivity to both antibodies and 29446 (3.52%) to S1 only.

Genotype Distribution and Demographic Characteristics of Hepatitis C Virus Nucleic Acid Testing Yield Cases Among US Blood Donors.

BACKGROUND: Hepatitis C virus (HCV) infection rates among US blood donors have been well characterized; however, few studies evaluated HCV genotypes among blood donors. Monitoring trends in disease and demographic patterns contributes to understanding the safety of the blood supply. We examined the demographic characteristics and distribution of HCV genotypes/subgenotypes for nearly a 16-year period among blood donors confirmed positive for HCV RNA but antibody negative (defined as nucleic acid testing [NAT] yield). METHODS: A retrospective assessment of demographic characteristics and testing data was used to determine temporal trends and geographical distribution of HCV genotypes/subgenotypes among American Red Cross blood donors confirmed positive as HCV-NAT yield. RESULTS: From 2003-2018, 343 donors (0.38/100 000 donations; 95% CI, .35-.43) were confirmed positive as HCV-NAT-yield cases. Temporal analysis revealed a significant increase in HCV-NAT-yield cases of 54.1% between 2009 and 2014 (P = .014), followed by a significant decline of 31.4% between 2015 and 2018 (P = .002). Significantly more HCV-NAT-yield cases were detected among first-time donors, non-Hispanic Whites, donors aged 20-29 years, equally likely to be males as females, with the highest frequency in the South (0.52/100 000 donations). Subgenotype 1a (49.6%) was most frequent, followed by 3a (18.7%), 2b (12.5%), 1b (8.5%), and 2a (1.7%). CONCLUSIONS: Voluntary nonremunerated blood donors are at low risk for HCV infection. Since 2015, the frequency of HCV-NAT-yield cases decreased despite an increase in acute HCV infection in the general population. HCV subgenotypes 1a and 3a continue to remain predominant among US blood donors with recent HCV infection.

Mitigating the risk of transfusion-transmitted infections with vector-borne agents solely by means of pathogen reduction.

BACKGROUND: This study evaluated whether pathogen reduction technology (PRT) in plasma and platelets using amotosalen/ultraviolet A light (A/UVA) or in red blood cells using amustaline/glutathione (S-303/GSH) may be used as the sole mitigation strategy preventing transfusion-transmitted West Nile (WNV), dengue (DENV), Zika (ZIKV), and chikungunya (CHIKV) viral, and Babesia microti, Trypanosoma cruzi, and Plasmodium parasitic infections. METHODS: Antibody (Ab) status and pathogen loads (copies/mL) were obtained for donations from US blood donors testing nucleic acid (NAT)-positive for WNV, DENV, ZIKV, CHIKV, and B. microti. Infectivity titers derived from pathogen loads were compared to published PRT log10 reduction factors (LRF); LRFs were also reviewed for Plasmodium and T. cruzi. The potential positive impact on donor retention following removal of deferrals from required questioning and testing for WNV, Babesia, Plasmodium, and T. cruzi was estimated for American Red Cross (ARC) donors. RESULTS: A/UVA and S-303/GSH reduced infectivity to levels in accordance with those recognized by FDA as suitable to replace testing for all agents evaluated. If PRT replaced deferrals resulting from health history questions and/or NAT for WNV, Babesia, Plasmodium, and T. cruzi, 27,758 ARC donors could be retained allowing approximately 50,000 additional donations/year based on 1.79 donations/donor for calendar year 2019 (extrapolated to an estimated 125,000 additional donations nationally). CONCLUSION: Pathogen loads in donations from US blood donors demonstrated that robust PRT may provide an opportunity to replace deferrals associated with donor questioning and NAT for vector-borne agents allowing for significant donor retention and likely increased blood availability.

West Nile virus activity in United States blood donors and optimizing detection strategies: 2014-2018.

BACKGROUND: Rare transfusion-transmitted West Nile virus (WNV) cases usually occur due to gaps in testing involving converting to more sensitive nucleic acid testing (NAT) formats (referred to as triggering). Using data from 2014 to 2018, we investigated a strategy used to increase detection early in the triggering period and reviewed its yield as the individual donation (ID)-NAT geographic area was decreased. METHODS: Mini-pool-NAT transitioned to ID-NAT following triggering based on one WNV NAT-reactive donation (having an elevated signal, repeat reactive, or in an area with WNV ongoing activity). ID-NAT-triggered geographic areas included an entire state (2014-2017) or collections within a 50-mile radius of the triggering donor's residential zip code (2018). During the MP- to ID-NAT transition, donation samples were retrieved and tested by ID-NAT for those with results not yet released (referred to as in-process testing). Reactive sample confirmation was performed by repeat NAT of an independent sample or antibody testing. RESULTS: ID-NAT included 3.2 million donations of more than 25 million tested year-round, resulting in 684 confirmed positives; all confirmed-positive donations occurred from June to December (0.64/10,000). Overall, 52% (358/684) required ID-NAT for detection, including 68 (19%) antibody negatives. Ten of 19 (53%) identified in-process were ID-NAT-only detectable, including four antibody negatives, or approximately 1 per year (2.8% of ID-NAT-only detectable). With reduced triggering geography, 12 of 19 (63%) were not identified (including 6/10 ID-NAT-only detectable, and 2/4 ID-NAT-only detectable/antibody negative). CONCLUSION: WNV NAT's utility is between June-December; however, abandoning testing outside of this time may increase risk. While in-process testing identified approximately one ID-NAT-only detectable (antibody-negative) donation per year, reducing the geographic triggered area decreased its effectiveness.

Expanded feasibility of ferritin testing: stability of ferritin stored as whole blood and validation of plastic tubes.

BACKGROUND: Ferritin testing is a recommended strategy to mitigate iron depletion in blood donors. A barrier for some testing platforms is a requirement to complete sample management and testing within a temporal window incompatible with the logistics of many blood collectors. The ability to delay separation of plasma/serum from red cells and subsequent testing would enhance the feasibility of ferritin testing on a broader scale. STUDY DESIGN AND METHODS: Thirty blood donors provided a research donation of 12, 4-mL sample tubes of whole blood. Six pairs of serum and K2 -EDTA-plasma tubes were centrifuged and samples tested in triplicate on day of collection and on each of the next 5 days following storage at 4°C. Comparison of ferritin values for serum versus K2 -EDTA-plasma at baseline was performed to validate plastic EDTA-containing tubes. Variation of ferritin values during storage was assessed for direction and strength of any detectable changes. RESULTS: Ferritin values were comparable between EDTA-plasma and serum, with baseline values from EDTA-plasma samples 7% lower on average than serum (p < 0.0001 by paired t-test). Variability over five storage days was within approved parameters in the manufacturer's instructions. Within-run precision averaged 2% to 3% for each test day and within-subject precision across all samples averaged less than 5% for both serum and EDTA-plasma. Repeated measures showed no difference in changes during storage by tube type or day of testing. CONCLUSION: These results support flexible testing procedures, expanding the opportunity for blood centers to adopt this measure for assessing donor iron status.

Impact of one-time testing for Trypanosoma cruzi antibodies among blood donors in the United States.

BACKGROUND: US blood donors are tested for Trypanosoma cruzi antibodies only at their first presentation, based on studies, reviewed here, demonstrating the absence of incident infections. Reports of autochthonous human transmissions of the parasite in Texas have raised concern about the safety of one-time testing. METHODS: Positive donation frequencies were evaluated among first-time blood donations from 2007 to 2015. Rates and their temporal changes were evaluated in an area of high T. cruzi infection and compared with rates elsewhere. Donors with positive results were surveyed for risk factors and relevant demographic characteristics. RESULTS: Data from 9.1 million first-time donations were analyzed; 585 (1:15,544) were confirmed positive by radioimmunoprecipitation assay (RIPA) or concordantly positive with a second screening test/licensed assay. Seroprevalence in first-time donors in Southern California (an area of high endemicity) was 1:2,747, or 5.7-fold higher than the overall rate. Rates did not change over time nationally but showed a nonsignificant consistent downward trend in Southern California. The majority (92%) of donors who responded to a questionnaire had one or more T. cruzi endemic-area risk factors. Five donors with likely autochthonous infection were identified (2007-2013); nine additional donors had RIPA false positivity. CONCLUSION: T. cruzi seroprevalence among donors nationally and in an area of high enzootic infection were stable or declining. Almost all interviewed seropositive donors had known risk factors indicating likely infection years earlier while residing in T. cruzi-endemic areas. In the United States, there was no evidence of increased T. cruzi prevalence among first-time donors.

Discordant human T-lymphotropic virus screening with Western blot confirmation: evaluation of the dual-test algorithm for US blood donations.

BACKGROUND: Human T-lymphotropic virus (HTLV) blood donation screening has used a dual-testing algorithm beginning with either a chemiluminescent immunoassay or enzyme-linked immunosorbent screening assay (ELISA). Before the availability of a licensed HTLV supplemental assay, repeat-reactive (RR) samples on a first assay (Assay 1) were retested with a second screening assay (Assay 2). Donors with RR results by Assay 2 were deferred from blood donation and further tested using an unlicensed supplemental test to confirm reactivity while nonreactive (NR) donors remained eligible for donation until RR on a subsequent donation. This "dual-test" algorithm was replaced in May 2016 with the requirement that all RRs by Assay 1 be further tested by a licensed HTLV supplemental test (Western blot [WB]). In this study, we have requalified the dual-test algorithm using the available licensed HTLV WB. STUDY DESIGN AND METHODS: We tested 100 randomly selected HTLV RRs on screening Assay 1 (Abbott PRISM chemiluminescent immunoassay) but NR on screening Assay 2 (Avioq ELISA) by a Food and Drug Administration-licensed WB (MP Biomedicals) to ensure that no confirmed positives were among those that were RR by Assay 1 but NR by Assay 2. RESULTS: Of the 100 samples evaluated, 79 of 100 were WB seronegative, 21 of 100 indeterminate, and 0 of 100 seropositive. Of the 79 of 100 seronegative specimens, 73 of 79 did not express any bands on WB. CONCLUSIONS: We demonstrated that none of the 100 samples RR on Assay 1 but NR on Assay 2 were confirmed positive. This algorithm prevents such donors from requiring further testing and from being deferred.

Prevalence, incidence, and risk factors of human immunodeficiency virus infection in blood donors in the Southeastern United States.

BACKGROUND: Human immunodeficiency virus (HIV)-positive blood donors pose a risk to blood safety. The Southeastern United States has the highest reported HIV infection rates. Here we calculate HIV prevalence, incidence, and residual risk in Southeastern US blood donors and report risk factors disclosed by incident donors in counseling sessions. STUDY DESIGN AND METHODS: American Red Cross donation and testing data from 2009 to 2014 for three Southeastern collection regions were used to calculate HIV prevalence, incidence, and residual risk. Incident donors had a previous HIV-negative donation within 730 days of their positive donation. Residual risk was defined as the window period multiplied by incidence. RESULTS: From 2009 to 2014, a total of 236 HIV-positive donors occurred in these regions for an overall prevalence of 8.3 per 100,000 donations. There were 56 incident donors over the 6-year period with incidence decreasing from 7.1 per 100,000 person-years (PYs) in the first two years (2009-2010) to 3.5 in the last two years (2013-2014). Residual risk decreased from 1 in 562,000 to 1 in 1,100,000. The most commonly reported risk factor behavior in male incident donors was men who have sex with men; females expressed no predominant risk factor. CONCLUSION: HIV prevalence and incidence among blood donors in the southeast are higher than other US regions, consistent with general public health surveillance. However, the overall residual risk estimates are low at less than 1 per million. Ongoing monitoring of the blood supply along with educational efforts to provide infected individuals with alternatives to donation remain important initiatives.

Differences in Early Cytokine Production Are Associated With Development of a Greater Number of Symptoms Following West Nile Virus Infection.

BACKGROUND: West Nile virus (WNV) is an emerging cause of meningitis and encephalitis in the United States. Although severe neuroinvasive disease and death can occur in rare instances, the majority of infected individuals remain asymptomatic or present with a range of clinical manifestations associated with West Nile fever. METHODS: To better understand the interindividual variability associated with the majority of WNV infections, we evaluated the association of cytokine/chemokine production and outcome of infection among 115 WNV-positive US blood donors identified in 2008-2011. All subjects self-reported symptoms as having occurred during the 2 weeks following blood donation, using a standardized questionnaire. RESULTS: We discovered that, prior to seroconversion, an early potent, largely type I interferon-mediated response correlated with development of a greater number of symptoms in WNV-infected individuals. Interestingly, individuals who developed fewer symptoms had not only a more modest type I interferon response initially, but also a protracted cytokine response after seroconversion, marked by the production of monocyte and T-cell-associated chemokines. CONCLUSIONS: Collectively, our data suggest that, although an early type I interferon response appears to be crucial to control WNV infection, successful immunity may require a modest early response that is maintained during the course of infection.

Hepatitis E virus: seroprevalence and frequency of viral RNA detection among US blood donors.

BACKGROUND: Hepatitis E virus (HEV) is a nonenveloped emerging virus of increasing worldwide interest. Antibody prevalence, RNA frequencies, and transfusion transmissions have been reported. We investigated the HEV RNA and antibody frequencies in US blood donors. STUDY DESIGN AND METHODS: Individual-donation HEV RNA testing was performed on 18,829 donations from six US geographic regions using a CE-marked nucleic acid test (95% limit of detection, 7.9 IU/mL). Repeat-reactive donations were confirmed by in-house, real-time polymerase chain reaction (PCR; 10.3 IU/mL). Total HEV seroprevalence in a randomly selected subset of donations (n = 4499) was assessed by a direct, double-antigen sandwich assay; reactives were further tested for immunoglobulin (Ig)G and IgM. As part of the total antibody confirmatory algorithm, the cutoff was adjusted. RESULTS: Two donations tested confirmed-positive for RNA (PCR not quantifiable, IgM/IgG positive; and 14 IU/mL, antibody negative) for a frequency of 1 in 9500 (95% confidence interval [CI], 1:2850-1:56,180) and 99.96% specificity (95% CI, 99.92%-99.98%); both donors were from the Midwest United States. Antibody prevalence was 9.5% (95% CI, 8.7-10.5) before the cutoff adjustment and 7.7% (95% CI, 7.0%-8.5%) after adjustment; 0.58% (95% CI, 0.39%-0.85%) were IgM positive. CONCLUSIONS: We confirmed comparatively low rates and low viral loads of HEV RNA in US blood donors indicating the need for individual-donation testing if screening is implemented. Antibody prevalence rates were comparable to those reported by one US study using a different assay, but lower than those reported in another study using yet a third assay. We did not answer the question of whether US blood donation screening is warranted. Selective strategies involving providing HEV-negative blood to severely immunosuppressed patients at risk of developing hepatitis may be considered.

Two human immunodeficiency virus Type 2 cases in US blood donors including serologic, molecular, and genomic characterization of an epidemiologically unusual case.

BACKGROUND: Blood donation screening for human immunodeficiency virus Type 2 (HIV-2) has been in place in the United States since 1992. However, only three HIV-2 antibody-positive donors have been reported to date, all detected via HIV-1 cross-reactivity. STUDY DESIGN AND METHODS: Here we identify two additional HIV-2-positive donors by routine anti-HIV-1 and anti-HIV-2 screening, including a first-time male donor living in Georgia having recently immigrated to the United States from West Africa (from a 1998 donation) and a Taiwanese female repeat donor (nurse) living in California with no travel outside of Taiwan or apparent connections to West Africa (from a 2015 donation). Neither donor acknowledged any risk factors, and both remained asymptomatic through follow-up. The second donor was further investigated by serologic, molecular, and genomic assays because of her unusual demographics. She was documented to harbor HIV-2 RNA, albeit sporadically by HIV-2-specific nucleic acid tests (35%-100% of replicates) and at very low levels (<9.6 IU/mL). Metagenomic next-generation sequencing (mNGS) confirmed the identification of a Group B HIV-2 strain, with recovered reads covering 46.9% of the predicted genome. CONCLUSIONS: The estimated frequency of an HIV-2-positive blood donor in the United States is one in 57 million donations. Due to the low frequency and low pathogenicity of HIV-2, public health and blood donation screening efforts must focus on HIV-1 detection and prevention. However, detection of HIV-2 infection in a donor with no apparent link to West Africa suggests that the United States must remain vigilant for HIV-2 virus infections. Ultradeep mNGS may be useful in the future for comprehensive identification of rare transfusion-transmissible agents.

Development of a multisystem surveillance database for transfusion-transmitted infections among blood donors in the United States.

BACKGROUND: The frequency of positive test results for transfusion-transmitted infections (TTIs) among blood donors is an important index of safety; thus, appropriate monitoring is critical, particularly when there are changes in policies affecting donor suitability. STUDY DESIGN AND METHODS: Testing algorithms from three large blood systems were reviewed and consensus definitions for a surveillance-positive result for hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), and human T-cell lymphotropic virus (HTLV) established. In addition, information on each donation, including donor demographics and location, was collected. Combined data were analyzed to characterize the epidemiology of TTIs by person, place, and time. RESULTS: Data from 14.8 million donations were collected for 2011 to 2012, representing more than 50% of the US blood supply. Surveillance-positive rates per 10,000 donations were as follows: HBV, 0.76; HCV, 2.0; HIV, 0.28; and HTLV 0.34. Rates did not vary between the 2 years, although there was variation within a year. With the exception of HTLV, rates were higher among males, and all rates were higher among first-time donations. Window-period donations (those positive only in nucleic acid tests) were infrequent (HBV, 13; HCV, 60; HIV, 14) during the 2-year period. Frequencies of surveillance-positive results varied by donor age and residence location. CONCLUSIONS: We demonstrated that standardized data from multiple major US blood systems can be combined and analyzed for change. However, TTI frequencies are low, impacting their sensitivity to change. Furthermore, observed fluctuations in TTI frequencies may be secondary to changes in blood donor demographics rather than necessarily reflecting the immediate impact of policy modification.

Nucleic acid testing to detect HBV infection in blood donors.

BACKGROUND: The detection of hepatitis B virus (HBV) in blood donors is achieved by screening for hepatitis B surface antigen (HBsAg) and for antibodies against hepatitis B core antigen (anti-HBc). However, donors who are positive for HBV DNA are currently not identified during the window period before seroconversion. The current use of nucleic acid testing for detection of the human immunodeficiency virus (HIV) and hepatitis C virus (HCV) RNA and HBV DNA in a single triplex assay may provide additional safety. METHODS: We performed nucleic acid testing on 3.7 million blood donations and further evaluated those that were HBV DNA-positive but negative for HBsAg and anti-HBc. We determined the serologic, biochemical, and molecular features of samples that were found to contain only HBV DNA and performed similar analyses of follow-up samples and samples from sexual partners of infected donors. Seronegative HIV and HCV-positive donors were also studied. RESULTS: We identified 9 donors who were positive for HBV DNA (1 in 410,540 donations), including 6 samples from donors who had received the HBV vaccine, in whom subclinical infection had developed and resolved. Of the HBV DNA-positive donors, 4 probably acquired HBV infection from a chronically infected sexual partner. Clinically significant liver injury developed in 2 unvaccinated donors. In 5 of the 6 vaccinated donors, a non-A genotype was identified as the dominant strain, whereas subgenotype A2 (represented in the HBV vaccine) was the dominant strain in unvaccinated donors. Of 75 reactive nucleic acid test results identified in seronegative blood donations, 26 (9 HBV, 15 HCV, and 2 HIV) were confirmed as positive. CONCLUSIONS: Triplex nucleic acid testing detected potentially infectious HBV, along with HIV and HCV, during the window period before seroconversion. HBV vaccination appeared to be protective, with a breakthrough subclinical infection occurring with non-A2 HBV subgenotypes and causing clinically inconsequential outcomes. (Funded by the American Red Cross and others.).

Investigational screening for Babesia microti in a large repository of blood donor samples from nonendemic and endemic areas of the United States.

BACKGROUND: Babesia microti, a transfusion-transmissible intraerythrocytic parasite, is increasing in frequency in the United States with no available FDA-licensed donor screening assay. We utilized investigational arrayed fluorescence immunoassay (AFIA) and polymerase chain reaction (PCR) to detect B. microti antibodies and DNA in blood donors. STUDY DESIGN AND METHODS: AFIA and real-time PCR were performed on frozen paired EDTA plasma (AFIA) and EDTA whole blood (PCR) samples collected from May to September 2010 to 2011 in nonendemic (Arizona [AZ] and Oklahoma [OK]), moderately endemic (Minnesota [MN] and Wisconsin [WI]), and highly endemic (Connecticut [CT] and Massachusetts [MA]) areas of the United States. AFIA utilized B. microti piroplasm as an antigen substrate; PCR primers and probes targeted the B. microti 18S ribosomal RNA gene. Data from AZ and OK were used to calculate specificity. All AFIA- or PCR-positive or -inconclusive donors were deferred, notified, and invited to participate in a follow-up study involving repeat testing and a demographic and risk-factor questionnaire. Recipient tracing was performed for any cellular component transfused at index, at subsequent donation, or within the prior 12 months. RESULTS: Testing of 13,269 paired samples included 4022 from AZ and OK, 4167 from MN and WI, and 5080 from CT and MA. B. microti antibody and/or DNA prevalences were 0.025% (95% confidence interval [CI], 0.00%-0.14%), 0.12% (95% CI, 0.04%-0.28%), and 0.75% (95% CI, 0.53%-1.03%) in the nonendemic, mid-endemic, and high-endemic regions, respectively. Specificities were 99.95% (95% CI, 99.82%-99.99%) at a 1-in-64 AFIA cutoff and 99.98% (95% CI, 99.86%-100.00%) at a 1-in-128 cutoff. CONCLUSIONS: B. microti prevalence followed expected geographical patterns. Screening was feasible with a performance comparable or superior to other infectious disease blood donor screening assays.

Blood donation screening for hepatitis B virus markers in the era of nucleic acid testing: are all tests of value?

BACKGROUND: The American Red Cross implemented hepatitis B virus (HBV) minipool (MP)-nucleic acid testing (NAT) in June 2009, in addition to existing tests for hepatitis B surface antigen (HBsAg) and antibodies to hepatitis B core antigen (anti-HBc). The value of all three tests was evaluated. STUDY DESIGN AND METHODS: HBsAg, anti-HBc, and HBV DNA (Ultrio MP-NAT, Gen-Probe/Novartis) donation results were analyzed during a 12-month period (July 1, 2009-June 30, 2010). Additional testing by individual-donation (ID) polymerase chain reaction (PCR) to confirm donor infection was performed when any HBV screening test was reactive or positive, except in the case of HBsAg neutralization-positive, anti-HBc-reactive samples. Numbers of blood donations identified as reactive or positive versus nonreactive or negative were compared. RESULTS: Of about 6.5 million donations, 699 were defined as from HBV-infected donors, of which 64% (444) were reactive for all three markers. More than 99% (697) had reactivity to one or both serologic tests with 68% (477) showing reactivity by MP-NAT. Only two donations were DNA-positive, seronegative NAT-yield donations (1 per 3.23 million), fewer than expected (p = 0.0075). Among MP-NAT-reactive donors, only small numbers represented early infection (2 or 0.4% with negative serology and 10 or 2.1% who were HBsAg confirmed positive, anti-HBc nonreactive). Of the 142 occult HBV-infected donors, 85% were MP-NAT nonreactive requiring ID-PCR for detection (121 or 54.5% of all MP-NAT nonreactives vs. 21 or 4.4% of all MP-NAT reactives). CONCLUSIONS: The HBV DNA-positive yield rate from MP-NAT was lower than expected, likely representing the rarity of such findings even in very large studies. With the implementation of HBV MP-NAT, the value of maintaining anti-HBc for the detection of low-level HBV DNA-positive donors was confirmed; however, HBsAg screening showed no blood safety value.

Dengue viremia in blood donors identified by RNA and detection of dengue transfusion transmission during the 2007 dengue outbreak in Puerto Rico.

BACKGROUND: In 2007, a total of 10,508 suspected dengue cases were reported in Puerto Rico. Blood donations were tested for dengue virus (DENV) RNA and recipients of RNA-positive donations traced to assess transfusion transmission. STUDY DESIGN AND METHODS: Blood donation samples from 2007 were maintained in a repository and tested individually for DENV RNA by transcription-mediated amplification (TMA); a subset was further tested by an enhanced TMA (eTMA) assay. TMA-reactive samples were considered confirmed if TMA (including eTMA) was repeat reactive (RR). All TMA-RR samples were tested by quantitative, DENV type-specific reverse transcriptase-polymerase chain reaction (RT-PCR) and for anti-DENV immunoglobulin (Ig)M by enzyme-linked immunosorbent assay. Samples positive by RT-PCR were further tested for infectivity in mosquito cell culture. Patients receiving components from TMA-RR donations were followed. RESULTS: Of 15,350 donation samples tested, 29 were TMA-RR for a prevalence of 1 per 529 (0.19%). DENV Types 1, 2, and 3 with viral titers of 10(5) to 10(9) copies/mL were detected by RT-PCR in 12 samples of which all were infectious in mosquito culture. Six TMA-RR samples were IgM positive. Three of the 29 recipients receiving TMA-RR donations were tested. One recipient in Puerto Rico transfused with red blood cells containing 10(8) copies/mL DENV-2 became febrile 3 days posttransfusion and developed dengue hemorrhagic fever. The recipient was DENV-2 RNA positive by RT-PCR; both the donor and the recipient viruses had identical envelope sequences. CONCLUSIONS: High rates of viremia were detected in blood donors in Puerto Rico coupled with the first documented transfusion transmission of severe dengue disease, suggesting that further research on interventions is needed.

Genetic variation in OAS1 is a risk factor for initial infection with West Nile virus in man.

West Nile virus (WNV) is a re-emerging pathogen that can cause fatal encephalitis. In mice, susceptibility to WNV has been reported to result from a single point mutation in oas1b, which encodes 2'-5' oligoadenylate synthetase 1b, a member of the type I interferon-regulated OAS gene family involved in viral RNA degradation. In man, the human ortholog of oas1b appears to be OAS1. The 'A' allele at SNP rs10774671 of OAS1 has previously been shown to alter splicing of OAS1 and to be associated with reduced OAS activity in PBMCs. Here we show that the frequency of this hypofunctional allele is increased in both symptomatic and asymptomatic WNV seroconverters (Caucasians from five US centers; total n = 501; OR = 1.6 [95% CI 1.2-2.0], P = 0.0002 in a recessive genetic model). We then directly tested the effect of this SNP on viral replication in a novel ex vivo model of WNV infection in primary human lymphoid tissue. Virus accumulation varied markedly among donors, and was highest for individuals homozygous for the 'A' allele (P<0.0001). Together, these data identify OAS1 SNP rs10774671 as a host genetic risk factor for initial infection with WNV in humans.

West Nile fever characteristics among viremic persons identified through blood donor screening.

Nucleic acid testing (NAT) of blood donors provides opportunities for identifying West Nile virus (WNV)-infected persons before symptoms develop and for characterizing subsequent illness. From June 2003 through 2008, the American Red Cross performed follow­up interviews with and additional laboratory testing for 1436 donors whose donations had initial test results that were reactive for WNV RNA; 821 of the donors were subsequently confirmed to have WNV infection, and the remainder were unconfirmed or determined to have false­positive results. Symptoms attributed to WNV infection were determined by comparing symptom frequency among 576 donors identified with early WNV infection (immunoglobulin M antibody negative) and those with unconfirmed infection. We estimate that 26% of WNV­infected persons become symptomatic, defined by the presence of at least 3 of 8 indicator symptoms. Nearly one­half of symptomatic persons sought medical care; only 5% received a diagnosis of WNV infection. Female subjects and persons with higher viral loads detected in the index donation were more likely than other subjects to develop symptoms.

CCR5 deficiency is a risk factor for early clinical manifestations of West Nile virus infection but not for viral transmission.

BACKGROUND: West Nile virus (WNV) is a neurotropic flavivirus transmitted to humans by mosquito vectors. Homozygosity for CCR5Delta32, a complete loss-of-function mutation in CC chemokine receptor 5 (CCR5), has been previously associated with severe symptomatic WNV infection in patients who present with clinical disease; however, whether it acts at the level of initial infection or in promoting clinical progression is unknown. METHODS: Here, we address this gap in knowledge by comparing CCR5Delta32 distribution among US blood donors identified through a comprehensive blood supply screening program (34,766,863 donations from 2003 through 2008) as either WNV true positive (634 WNV-positive cases) or false positive (422 WNV-negative control participants). All subjects self-reported symptoms occurring during the 2 weeks following blood donation using a standardized questionnaire. RESULTS: No difference was observed in CCR5Delta32 homozygous frequency between the WNV-positive cases and WNV-negative control participants. However, CCR5Delta32 homozygosity was associated in cases but not controls with clinical symptoms consistent with WNV infection (P = .002). CONCLUSIONS: CCR5 deficiency is not a risk factor for WNV infection per se, but it is a risk factor for both early and late clinical manifestations after infection. Thus, CCR5 may function normally to limit disease due to WNV infection in humans.