Biomolecular study of seroindeterminate individuals for the retrovirus HTLV-I/II

BIOMOLECULAR STUDY OF SEROINDETERMINATE INDIVIDUALS FOR THE RETROVIRUS HTLV-I/II (ABSTRACT)^*. THESIS. FORTALEZA, 2001.

TEREZINHA DE JESUS TEIXEIRA SANTOS^**

The HTLV-I/II belongs to the Retroviridae family and Oncovirinae subfamily. Its genetic structure is similar to that of other mammalian retroviruses, with gag, pol, env and tax/rex regions. The gag region codes for p19, p24 and p15 proteins; the pol region codes for the reverse transcriptase, RNAse and integrase; the env region codes for the glycoproteins gp21 and gp46; and the pX region codes for the regulatory proteins tax (p40) and rex (p27).

The HTLV-I/II is endemic in Central and West Africa, Caribbean, South America, Japan and Melanesia. In Brazil, its prevalence is of 0.46%. The molecular epidemiology shows that the HTLV-I is divided into the Ia (cosmopolitan), Ib (Central Africa) and Ic (Melanesia) subtypes, and HTLV-II into the IIa, IIb, IIc and IId subtypes. This retrovirus is transmitted vertically (mother-to-child) and horizontally (sexual contact, blood transfusion and parenteral drugs use). The Tropical Spastic Paraparesis / HTLV-I-associated Myelopathy (TSP/HAM) and Adult T-cell Leukemia/Lymphoma (ATL) are their main associated pathologies.

The laboratorial diagnosis of HTLV is done with screening (ELISA and particle agglutination), confirmatory (Western blot, IFA, RIPA, and more recently INNO-LIA) and molecular (PCR, NASBA and bDNA) tests.

Serological tests for HTLV infection are mandatory in some countries since 1986, and in Brazil since 1993. The results from blood banks have shown negative, positive and indeterminate results.

Since the definition of the seroindeterminate condition is important for blood banks and for the patient's families, we intended to delineate a diagnostic, demographic and co-infection and risk factors association pictures of this condition as well as to analyze Western blot protein patterns and isolated proteins with possible predictive meaning.

For this, a preliminary analysis of prevalence of the seroindeterminate and ELISA reactive individuals in the general population of blood donors from the Hematology and Hemotherapy Center (HEMOCE) of Fortaleza City between 1997 and 2000 was done. Subsequently, a sample of 191 ELISA reactive individuals (118 WB seroindeterminates and 73 WB seropositives) from HEMOCE's HTLV Unit was analyzed, with their previous ethical consent. This sample was diagnostically analyzed with ELISA, particle agglutination, Western blot, INNO-LIA and PCR. For PCR, the tax/rex region was amplified.

The results showed that the prevalence of seroindeterminate individuals in the general population of blood donors was of 1.64‰ (0.16%), and the prevalence of the seropositives for HTLV-I/II was of 1.36‰ (0.13%). On the other hand, the prevalence of seroindeterminate individuals was of 21.91% in relation to the ELISA reactive population.

The results of our sample showed that, diagnostically, the PCR evidenced infection in 41 seroindeterminate individuals studied, where 22.2% were positive and 77.8% were negative for HTLV-I/II. Moreover, the comparative analysis of PCR and INNO-LIA showed high concordance of results in both tests. The demographic analysis showed a trend of predominance of males among the WB seroindeterminate and PCR negative individuals as well as a trend of predominance of females among the HTLV-I/II seropositive individuals. In addition, mulattos predominate in both groups. As to age, seroindeterminate individuals are younger than the seropositive ones.

The analysis of distribution of the seroindeterminate and HTLV-I/II seropositives individuals as to the association with Co-Infections showed a higher prevalence of hepatitis B and C for seropositive individuals, and a non-association with HIV, syphilis and Chagas disease. The analysis of association with Risk Factors showed a high percentage of breast feeding similar for both groups, and a high percentage of blood transfusion and sexually-transmitted diseases (syphilis) for HTLV-I/II seropositive individuals.

The analysis of the WB protein patterns and isolated proteins showed that among the WB seroindeterminates the most frequent patterns were p24, GD21 (7.6%) and p19 + gp21 (or gp46) + one or more of the p26, p28, p32, p36, p53 proteins (25.5%), and the isolated p24 protein (55.0%). As to the seroindeterminate PCR negative individuals, the most frequent patterns were p28, p53, GD21 (9.4%) and p19 + gp21 (or gp46) + one or more of the p26, p28, p32, p36, p53 proteins (31.2%), and the isolated gp21 protein (50.0%), p19 (46.9%) and p28 (43.8%) proteins. As to the seroindeterminate PCR positive individuals, the most frequent patterns were p24, GD21 (50.0%) and p19 + p24 + gp21 (or gp46) + one or more of the p26, p28, p32, p36, p53 proteins (77.8%), and the isolated p24 protein (100%).

In conclusion, the study of our sample allowed us to show (1) a high prevalence of seroindeterminates in the population of ELISA HTLV-I/II reactive individuals from HEMOCE, (2) the efficacy of PCR as a diagnostic method for seroindeterminate definition, and INNO-LIA as an optional test, (3) a demographic profile of the seroindeterminate individuals, and (4) the identification of the WB protein patterns and isolated proteins which could be eventual candidates for predictive markers for HTLV-I/II infection positivity or negativity.

KEY WORDS: polymerase chain reaction, Western blotting, Retroviridae, HTLV-I/II, seroindeterminate.

**Address: Rua Coronel Nunes de Melo 1127, 60.430-270 Fortaleza CE, Brasil.

*

Estudo biomolecular de indivíduos soroindeterminados para o retrovírus HTLV-I/II (Resumo). Tese de Doutorado, Universidade Federal do Ceará (Área: Neurovirologia). Orientador: Carlos Maurício de Castro Costa.

Publication Dates

• Publication in this collection
  11 Apr 2002
• Date of issue
  Mar 2002