Prevalence of human T‐cell lymphotropic virus‐I/II‐indeterminate reactivities in a Greek blood bank population

Dear Sir, Human T-cell lymphotropic virus-I/II (HTLV-I/II) full-scale screening of blood donations has been introduced since mid-1980s in public health authorities of Canada, Japan, USA and several European countries. In some cases, obligatory screening is restricted to new donors only. In Greece, blood donors are routinely screened since 1995. In a recent survey that we have conducted between 1997 and 2002, in four blood centres of southwestern Greece (Peloponese peninsula), the presence of HTLV-I infection has been confirmed in six of 107 302 (0 0056%) donors (Tseliou et al., 2003). In the present report, the HTLV-I/II indeterminate reactivities of this blood donor population are analysed. The initial screening of the serum samples was performed using a combined HTLV-I/II enzymelinked immunoassay (EIA) method (Murex HTLV-I/II, Murex Diagnostics, Dartord, UK), which is a new generation assay that uses recombinant proteins and selected synthetic peptides of HTLV antigens. Western Blot (WB) (HTLV WB2 4, Genelabs Diagnostics, Singapore) and a line immunoassay (INNO-LIA HTLV-I/HTLV-II, Inogenetics, Ghent, Belgium) confirmed the sera that gave repeatedly positive results with the EIA method and were also used in order to distinguish HTLV types I and II. A WB was scored as HTLV-I-positive only when bands for the gag proteins p19 and p24 and the env proteins rgp21 and rgp46-I were present, while samples with reactivity to p24, rgp21, rgp46-II were considered positive for antiHTLV-II. Samples without reactivity in WB were interpreted as negative and all other banding patterns were defined as indeterminate. Criteria for interpreting the results of the INNO-LIA HTLV method were those recommended by the manufacturer. Ninety-eight of the 107 302 (0 09%) serum samples of blood donors were repeatedly positive in EIA. Confirmations by WB2 4 revealed that a large percentage (43 of 98, 43 9%) had an HTLV-I/II-seroindeterminate pattern and only six (6 1%) were scored as HTLV-I positive. INNO-LIA showed that 22 (22 4%) of the EIA-positive samples were indeterminate (all being also indeterminate with WB2 4), while the same six samples reacted against HTLV-I antigens. PCR revealed that in contrast with the HTLV-I positive specimens, none of the HTLV-indeterminate specimens reacted with any of the primer sets (from the proviral pol and tax regions amplifying both HTLV-I and HTLV-II). Table 1 shows that the 43 HTLVindeterminate WB2 4 profiles allowed the identification of as many as 11 different profile categories. The most frequently identified WB2 4 profiles including those with isolated bands such as rgp21 (n1⁄4 19) or p24 (n1⁄4 6). All 22 indeterminate INNO-LIA reactivities overlap with WB indeterminate profiles. A HTLV gag indeterminate profiles (HGIP), exhibiting reactivity to p24 and p28, but lacking the p19 and env bands, was detected in two samples (Table 1). Counselling and notification of donors with HTLVindeterminate confirmatory results is difficult, particularly in endemic regions, and the virologic or biologic basis for these results has yet to be elucidated (Busch et al., 2000; Rouet et al., 2001). Although WB2 4 has substantially decreased the high rate of false-positive results, usually obtained by WB2 3 without compromising the sensitivity, indeterminate reactivities, such as HGIP, have been also detected among blood donors in Europe, US and elsewhere with rates being considerably higher in endemic areas (Vrielink et al., 1995; Busch et al., 2000; Rouet et al., 2001; Morozov et al., 2002; Remesar et al., 2002). Therefore, the use of a dual EIA algorithm for HTLV-I/II among blood donors has been proposed as an attempt to reduce the number of expensive and non-conclusive WB and INNO-LIA tests (Rouet et al., 2001). In our region, although is a non endemic, a large number of indeterminate results were observed, mainly due to WB patterns reactive to only a part of the viral proteins or less frequently to reactivities with bands other than gp21 (i.e. p28). It seems that in our population WB2 4, Correspondence: Dr Athanassios Tsakris, Department of Microbiology, Medical School, University of Athens, 75 Mikras Asias Street, 115 27 Athens, Greece. Tel. : þ30 210 7462140; fax: þ30 210 7461489; e-mail: atsakris@med.uoa. gr Transfusion Medicine, 2004, 14, 253–254