Lack of difference in cytomegalovirus transmission via the transfusion of filtered-irradiated and nonfiltered-irradiated blood to newborn infants in an endemic area

Sequence analyses of variable cytomegalovirus genes for distinction between breast milk- and transfusion-transmitted infections in very-low-birth-weight infants

BACKGROUND

Cytomegalovirus (CMV) transmission to very-low-birth-weight infants (VLBWIs) sometimes induces serious clinical symptoms. Although breast milk is considered a major source of transmission, transfusion-transmitted CMV (TT-CMV) infection is often suspected when CMV disease develops after transfusion. Thus, it is clinically important to distinguish between transfusion-transmitted and breast milk-transmitted CMV infections.

STUDY DESIGN AND METHODS

Study A: The incidence of acquired CMV transmission was prospectively investigated in 65 VLBWIs. Study B: To determine the transmission routes in 18 TT-CMV-suspected VLBWIs who had been reported in our hemovigilance system, we performed polymerase chain reaction for CMV DNA in fed breast milk and/or repository blood samples related to transfused leukoreduced blood products. Furthermore, we evaluated the identity of CMV strains in patients' urine/blood samples and fed breast milk by sequence analyses of variable CMV genes UL139 and UL146.

RESULTS

Study A: Acquired CMV infection was found in 4 of 65 VLBWIs (6.2%). Study B: CMV DNA was detected in fed breast milk for 12 of 14 TT-CMV-suspected cases, for which breast milk was available. Furthermore, CMV DNA sequence-matching rates between fed breast milk and patients' urine/blood for both UL139 and UL146 genes were 100% or nearly 100% in 11 patients. In contrast, repository blood samples for 11 of 14 patients were CMV DNA negative.

CONCLUSION

CMV is principally transmitted through breast milk in VLBWIs. The risk of TT-CMV seems to be extremely low when using leukoreduced blood products. Sequence analyses of the variable CMV genes are useful for evaluating CMV transmission routes.

Transfusion-transmitted CMV infection - current knowledge and future perspectives

Transmission of human cytomegalovirus (CMV) via transfusion (TT-CMV) may still occur and remains a challenge in the treatment of immunocompromised CMV-seronegative patients, e.g. after stem cell transplantation, and for low birthweight infants. Measures to reduce the risk of TT-CMV have been evaluated in clinical studies, including leucocyte depletion of cellular blood products and/or the selection of CMV-IgG-negative donations. Studies in large blood donor cohorts indicate that donations from newly CMV-IgG-positive donors should bear the highest risk for transmitting CMV infections because they contain the highest levels of CMV-DNA, and early CMV antibodies cannot neutralise CMV. Based on this knowledge, rational strategies to reduce the residual risk of TT-CMV using leucoreduced blood products could be designed. However, there is a lack of evidence that CMV is still transmitted by transfusion of leucoreduced units. In low birthweight infants, most (if not all) CMV infections are caused by breast milk feeding or congenital transmission rather than by transfusion of leucoreduced blood products. For other patients at risk, no definitive data exist about the relative importance of alternative transmission routes of CMV compared to blood transfusion. As a result, only the conduction of well-designed studies addressing strategies to prevent TT-CMV and the thorough examination of presumed cases of TT-CMV will achieve guidance for the best transfusion regimen in patients at risk.

Postnatal cytomegalovirus infection: a pilot comparative effectiveness study of transfusion safety using leukoreduced-only transfusion strategy

BACKGROUND

The optimal mitigation strategy to prevent transfusion transmission of cytomegalovirus (TT-CMV) in preterm very low birthweight infants remains debated. Hospitals caring for this patient population have varied practices.

STUDY DESIGN AND METHODS

A prospective observational comparative effectiveness pilot study was conducted to determine the feasibility for a larger study. The pilot was carried out at hospitals using a leukoreduction (LR)-only transfusion strategy. Specimen and data collection for this study was performed in a similar approach to a study completed at Emory University that employed the CMV-seronegative plus LR approach. All testing was performed at one laboratory. The rates of TT-CMV using the two transfusion strategies were compared.

RESULTS

Zero incidence of TT-CMV was detected in infants (n = 20) transfused with LR-only blood (0/8; 95% confidence interval [CI], 0-25.3%) and is consistent with the previously reported zero incidence of TT-CMV finding in a cohort of infants transfused with CMV-negative plus LR blood (0/310; 95% CI, 0%-0.9%). The seroprevalence rate among enrolled mothers (n = 17) was 60%. Forty percent of those infants (8/20) received 43 transfusions; five were transfused with one or more CMV-seropositive blood components. One infant had tested positive for CMV before receiving blood transfusions; the infant's mother was CMV immunoglobulin (Ig)G positive and IgM negative.

CONCLUSIONS

Using the LR-only transfusion approach, zero cases of TT-CMV were detected in this pilot study. A larger study is needed to reliably determine the most effective strategy for prevention of TT-CMV in this population.

Transfusion-related cytomegalovirus infection among very low birth weight infants in an endemic area

This study investigated the incidence of acquired cytomegalovirus (CMV) infection in very low birth weight infants (VLBWI) given CMV seropositive blood, and sought to determine whether filtering and irradiation of blood products could help prevent CMV infection and the time required to clear passively-derived anti-CMV IgG among 80 VLBWI transfused with filtered-irradiated blood, 20 VLBWI transfused with nonfiltered- nonirradiated blood and 26 nontransfused VLBWI. CMV IgG and IgM values were obtained from all blood products prior to transfusions, and from VLBWI at birth until the infants became seronegative. Urine was obtained for CMV culture at birth and every 3-4 weeks until 12 weeks after the final transfusion. The incidence of CMV IgG seropositivity among the 126 infants at birth and the blood products given were 96% and 95%, respectively. The incidence of acquired CMV infection was 4/100 (4%) in the transfused group: 2/80 (2.5%) and 2/20 (10%) in the filtered-irradiated and nonfiltered-nonirradiated transfusion groups, respectively. Approximately 9-10 months elapsed to clear passively acquired CMV IgG. The irradiation and filtering of the blood products did not seem to decrease the transfusion-related CMV infection rate in Korea among VLBWI, however, further validation is recommended in a larger cohort of infants.

Is White Blood Cell Reduction Equivalent to Antibody Screening in Preventing Transmission of Cytomegalovirus by Transfusion? A Review of the Literature and Meta-Analysis

The question whether the use of cytomegalovirus (CMV)-seronegative versus white blood cell (WBC)-reduced blood components is equally efficacious in preventing transfusion-acquired CMV infection remains unresolved. A total of 829 recipients of CMV-seronegative components were followed in 11 studies, and a total of 878 recipients of WBC-reduced components were followed in 12 studies. Twelve (1.45%) of 829 recipients of CMV-seronegative components and 24 (2.73%) of 878 recipients of WBC-reduced components developed CMV infection in these studies. Among bone marrow transplant (BMT) recipients, the risk of CMV infection was, respectively, 1.63% (11/674) and 3.01% (21/697). Four of 7 controlled studies of CMV-seronegative components and 1 of 3 controlled studies of WBC-reduced components indicated benefit from these special components compared with CMV-unscreened/non-WBC-reduced components. One of 3 controlled studies indicated benefit from CMV-seronegative components, as compared with WBC-reduced components. Across a subset of studies whose results were integrated in a meta-analysis, CMV-seronegative or WBC-reduced components were virtually equivalent to each other when they were compared with CMV-unscreened/non-WBC-reduced components. CMV-seronegative components were associated with a 93.1% reduction in the risk of CMV infection; WBC-reduced components were associated with a 92.3% reduction in risk (summary odds ratio [OR] = 0.069; 95% confidence interval [CI], 0.037-0.128; P < .05; and summary OR = 0.077; 95% CI, 0.031-0.190; P < .05, respectively). However, across 3 studies that compared CMV-seronegative and WBC-reduced components to each other, CMV-seronegative components were associated with a 58% reduction in risk (summary OR = 0.42; 95% CI, 0.22-0.79; P < .05). Thus, a meta-analysis of the available controlled studies indicates that CMV-seronegative blood components are more efficacious than WBC-reduced blood components in preventing transfusion-acquired CMV infection.

Perinatal or early-postnatal cytomegalovirus infection in preterm infants under 34 weeks gestation born to CMV-seropositive mothers within a high-seroprevalence population

In a prospective study, we evaluated the frequency, correlates, and clinical significance of perinatal or early-postnatal cytomegalovirus (CMV) infection in <34-week-gestation infants (n=95) born to CMV-seropositive mothers. None had congenital CMV infection. Overall, 21 (22.1%; 95% CI=14.2-31.8) infants were found to be infected; 10 excreted CMV at <60 days, and 11 had later excretion. Blood transfusion, birth weight, and vaginal delivery were not associated factors. Receiving natural breast milk within the first 30 days (OR=4.5, P=.02) or for >30 days (OR=7.9, P <.01) was associated with infection. Only one (4.8%) of the infected infants was symptomatic. For <34-week-gestation infants, frequency of perinatal and early-postnatal CMV infection is high. Early or prolonged exposure to breast milk is an associated factor. However, most infections are asymptomatic, indicating that CMV infection in preterm infants within such a population is a serious problem infrequently.

Low frequency of observed anti-HLA among transfused preterm infants

BACKGROUND

Although low-birth-weight infants (LBWI) often receive multiple transfusions, there is controversial information on their development of antibodies against WBCs or platelets.

STUDY DESIGN AND METHODS

A total of 52 LBWI with birth weights less than 1500 g were randomly assigned to receive either RBCs that had been WBC- reduced (n = 25) or nonfiltered blood (n = 27). Serum samples collected from 37 infants at 3 months of age and from 30 children when they were 5 to 11 years old were tested. Anti-HLA was assayed with an anti-human globulin-augmented lymphocytotoxicity test against a panel consisting of 13 lymphocytes and against parental cells.

RESULTS

None of 52 transfused LBWI of either group developed anti-HLA (95% CI, 0%-6.8% for overall, 0%-13.7% for the WBC-reduced group, and 0%-12.7% for the nonfiltered group).

CONCLUSION

Multiply transfused LBWI rarely produced antibodies to HLA of blood donors and to noninherited maternal antigens. The benefits of WBC reduction to prevent HLA alloimmunization during infancy were not supported by this study and need further investigation.

Effectiveness of WBC reduction in neonates: what is the evidence of benefit?

BACKGROUND

The presence of WBCs in RBCs is thought to be associated with a number of significant adverse effects in recipients. In adults, WBC reduction has been shown to reduce the frequency of HLA alloimmunization, CMV and HTLV infections, and febrile nonhemolytic transfusion reactions. However, neonates are unique, given that they have an immature immune system and are frequently transfused with RBCs. Thus, the aims of this systematic review were to determine whether WBC reduction of RBCs transfused to neonates decreases the transmission of CMV, reduces the ability to develop HLA antibodies, or reduces the risk of immunomodulation. In addition, nosocomial infection, mortality, and duration of stay were identified and analyzed.

STUDY DESIGN AND METHODS

All studies of WBC reduction were identified by a systematic review of the literature. Studies meeting the inclusion criteria were grouped based on study outcome. Where appropriate, studies were pooled to obtain an overall measure of effect.

RESULTS

Nine eligible studies were identified from the systematic literature search, and six were deemed evaluable. Two studies evaluated WBC reduction and the development of CMV, with different results. The pooled OR was 0.19 (95% Cl, 0.01-3.41), suggesting a clinical but nonsignificant effect. Two studies evaluated WBC reduction and HLA antibody development. As with CMV, the two studies were not congruent in their results. The pooled OR was 0.17 (95% Cl, 0.01-2.43). As for immunomodulation, two small studies presented evidence of a statistically significant change in lymphocyte subsets. No studies were identified with a primary objective of evaluating the impact of WBC reduction on nosocomial infection, mortality, or duration of stay.

CONCLUSION

Current evidence suggests that WBC reduction may be effective in neonates; however, further studies are needed. The lack of convincing data and the significant cost of WBC reduction mandate evaluations to determine the clinical and economic impact.

Congenital and perinatal infections with cytomegalovirus

Congenital cytomegalovirus (CMV) infections remain the leading viral cause of congenital malformations in the developed world. Despite advances in our knowledge, the epidemiology and natural history of congenital CMV infection are still poorly understood, particularly in Australia. Congenital CMV causes illness ranging from no clinical disease (asymptomatic, but infected) through to prematurity, encephalitis, deafness and haematological disorders and death. Perinatal CMV acquisition usually results in less severe illness including asymptomatic infection, acute infection with hepatitis, fever, and pneumonitis. CMV infects only humans, and in vitro and in vivo models for intrauterine infection are required in order to test new treatments, and better describe the pathogenesis of congenital CMV. Using new knowledge of the epidemiology and natural history of CMV, treatment regimens during late pregnancy are currently undergoing clinical trial although no definitive recommendations are available.

[Leukocyte depletion and infection by cytomegalovirus]

Cytomegalovirus (CMV) can be transmitted by fresh blood components containing leukocytes. Consequences of CMV infection are serious in immunocompromised patients and in neonates. Thus, prevention of transfusion-transmitted CMV is of paramount importance. The use of blood products from CMV seronegative donors has been shown effective in preventing transmission. However, it does not completely eliminate the risk of transmission. Moreover, as CMV seroprevalence reaches 50 to 100% depending on the geographical and socioeconomic conditions, the availability of CMV seronegative products is limited. Leukodepletion of cellular blood products can be achieved by various filtration techniques. A method capable of achieving a residual leukocyte count < 5 x 10(6) per unit allows for the reduction of CMV transmission to a level at least equivalent to the transfusion of seronegative blood components. Moreover, leukodepletion may reduce endogenous virus reactivation. Administration of filtered blood products from CMV seronegative donors is usually recommended for those patients at major risk of severe CMV transfusion-associated disease. The ability of the most efficient methods for blood filtration in preventing CMV transmission has to be assessed. Such methods would make it possible to avoid serological screening of blood donors.