Epidemiologic background of blood donors with antibody to human T-cell lymphotropic virus. Transfusion Safety Study Group

High seroprevalence of anti-HTLV-I/II antibodies among solid organ donors necessitates confirmatory testing

BACKGROUND

Human T-cell lymphotrophic virus (HTLV) type I has been linked to adult T-cell leukemia/lymphoma (ATL) and HTLV-I associated myelopathy (HAM). Transmission of HTLV by blood and organ transplantation has been documented, with some infections leading to clinical disease. Organ donors are tested for anti-HTLV antibodies and donor suitability is determined primarily by results from enzyme immunoassays (EIA). Confirmatory testing is not routinely performed, and the number of false positive organ donors is unknown.

METHODS

In order to investigate the contemporary seroprevalence of anti-HTLV I/II antibodies among solid organ donors and determine the number of false positive samples, we tested 1,408 specimens from prospective organ donors in 2002 and 2003. All specimens were tested for anti-HTLV antibodies by a commercial EIA. Repeatedly reactive specimens underwent confirmatory testing using a commercial Western blot.

RESULTS

There were 22 repeatedly EIA reactive donor specimens (1.56%). Five specimens did not undergo further testing because of case shutdown or insufficient sample quantity. HTLV I/II western blot confirmed six positives, whereas five were negative and six were indeterminate. The majority of confirmed specimens were positive for antibodies to HTLV-II.

CONCLUSIONS

Our data shows that 29% of initially reactive specimens were false positives. With the increasing demand for organs, the unnecessary rejection of organs that are falsely positive for HTLV antibodies becomes of tremendous importance and stresses the need for timely confirmatory testing for HTLV.

Significance of human T-lymphotropic virus type I indeterminant serological findings among healthy individuals

Follow-up studies on 67 blood donors with indeterminant serological findings for human T-lymphotropic virus (HTLV) type I by standard immunoassays showed no evidence of infection by polymerase chain reaction analysis for HTLV-I or HTLV-II nucleic acids or by antibody reactivity to a unique HTLV-I recombinant envelope protein, MTA-4. Among HTLV-I- or -II-infected individuals, a history of blood transfusion, past residence in established HTLV-I endemic areas or some association with intravenous drug use were common. In contrast, 85% of indeterminant cases had none of these risk factors. These observations suggest that healthy individuals with indeterminant serology for HTLV-I should not require additional studies.

[Investigation of a transfusion contaminated by HTLV-I virus]

In front of the successive development of an HTLV-I seroconversion and a neuromyelopathy in a French Caucasian following a cardiac transplantation, an ascendant epidemiologic investigation must be manage to search a risk factor or a possible blood donor contaminated with HTLV-I virus. We selected an HTLV-I seropositive donor whose RBC participated to the patient's transfusion. This woman from Martinique island was a regular donor in our blood center and a second investigation was initiated to examine the patients transfused with the blood products issued from her previous donation. Nine were identified and controlled among them a patient who has received a RBC was found HTLV-I seropositive. An evaluation of the infectivity of the different blood products according to their type and specificity has been done. These data confirm that transmission of the HTLV-I is possible through donation of healthy seropositive donor and can induce the development of associated pathology, and prove the importance of screening blood donors for HTLV-I antibodies.

Prevalence of antibodies to HTLV-1 in South American Indians (Mapuches) from Chile

The seroprevalence of HTLV-1 antibodies was investigated in 405 serum samples from healthy South American Indians (Mapuches) from Chile, using enzyme linked immunoassay (ELISA), Western immunoblot (WB) and radioimmuno precipitation assay (RIPA). Six samples were positive by ELISA; 3 of them were confirmed by WB/RIPA. Thus, we observed a seroprevalence of 0.7% for HTLV-1 antibodies in healthy Mapuches.

[Epidemiologic study of anti-HTLV-I/II antibodies in blood donors in metropolitan France. The Retrovirus Working Group of the National Blood Transfusion Society]

Between march and april 1989, the prevalence of HTLV-I/II antibodies was studied in a non selected population of 45,033 blood donors of Continental France. Serum samples were collected and screened by 12 Blood Banks located in different parts of the country. Screening was performed by 4 ELISAs (Abbott-Du Pont de Nemours-Organon-Pharmacia) and by gelatin particle agglutination (Fujirebio); the sensitivity of these tests was previously evaluated with an HTLV-I/II panel of the French National Society of Transfusion. The reproducibly reactive sera were confirmed by Western-Blot (Du Pont) and radioimmunoprecipitation assay. Five donors were confirmed positive: the global prevalence is 0.011%. This prevalence is one of the highest in Europe. Three of the five positive donors (0.007%) are white subjects. The other two are natives from the French West Indies (0.81%). Since may 1989 the Ministry of Health recommends for Continental France to test donors originating from endemic zones or to use their plasma for fractionation. The results obtained in this study show that the efficacy of these measures are incomplete since 0.007% donors (1 out of 15,000 blood donations) are not tracked down.

Screening of selected male blood donors for p24 antigen of human immunodeficiency virus type 1. The Transfusion Safety Study Group

BACKGROUND

The p24 antigen of human immunodeficiency virus type 1 (HIV-1) is sometimes detected before antibody (anti-HIV-1) is detectable in the serum of recently infected persons. This has led to the consideration of p24-antigen testing for routine screening of blood donors.

METHODS

To estimate how many HIV-infected seronegative donors would be identified if p24-antigen screening was introduced, we tested selected donations from a repository of 200,000 serum samples from voluntary donors that was established in late 1984 and early 1985. The 8597 serum samples selected for p24-antigen screening were chosen because their donors had demographic characteristics known to be associated with a high prevalence of seropositivity.

RESULTS

The prevalence of anti-HIV-1 antibodies in the 1984-1985 serum samples selected for p24-antigen screening was 1.54 percent--more than 100 times the 0.012 percent prevalence in present-day donations in the United States. The antigen was detected in 15 of 132 serum samples (11.4 percent) from donors who had already been confirmed as seropositive. No instance of confirmed positivity for p24 antigen was found among the 8465 seronegative serum samples.

CONCLUSIONS

These data indicate that the yield of screening for p24 antigen in volunteer donors to identify HIV-1 carriers would be negligible. We therefore recommend against routine screening with currently available p24-antigen assays.