Molecular detection and isolation of human T-cell lymphotropic virus type I (HTLV-I) from patients with HAM/TSP in São Paulo, Brazil.

BACKGROUND: Infection with HTLV-I is etiologically linked with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). However some patients with chronic progressive paraparesis resembling HAM/TSP have been shown to be infected with HTLV-II. OBJECTIVE: To clarify the role of each of these human retroviruses in the etiology of HAM/TSP in São Paulo, Brazil. STUDY DESIGN: A detailed serological and molecular analysis of HTLV-I/II infection was performed in a cohort of 19 patients with HAM/TSP attending a neurological clinic. RESULTS: Plasma samples analyzed for anti-HTLV-I/II antibodies using a Western blot assay, comprising HTLV-I (rgp46I)- and HTLV-II (rgp46II)-specific recombinant env epitopes, demonstrated reactivity to rgp46I and hence were typed as seropositive for HTLV-I. Presence of HTLV genomic sequences in peripheral blood mononuclear cells (PBMC) was sought after by PCR using consensus primers SK 110 and SK 111 for the pol region of HTLV proviral DNA followed by hybridization with type-specific probes--SK 112 (HTLV-I) and SK 188 (HTLV-II). Southern blots from all individuals hybridized with SK 112 but not with SK 188, further confirming HTLV-I infection. Cocultivation of PBMC from eight of these patients with activated lymphocytes from normal individuals resulted in active viral production, detected as presence of soluble p24gag antigen in culture supernatants. Investigation of risk factors for HTLV-I infection in these individuals revealed that five out of 19 patients studied (26.3%) had received blood transfusions previous to disease onset.

Laboratory characterization of human T cell lymphotropic virus types 1 (HTLV-1) and 2 (HTLV-2) infections in blood donors from Sao Paulo, Brazil.

Serologic screening for human T cell lymphotropic virus types 1/2 (HTLV-1/2) infection in blood donors has been recently introduced in Brazil. Analysis of 351,639 blood donations in Sao Paulo from January 1992 to October 1993 identified 1,063 positive (0.30%) and 2,238 indeterminate (0.63%) samples based on serologic confirmation using a 21e Western blot. A detailed analysis (serologic, molecular, and virologic), based on a laboratory diagnostic algorithm for characterization of HTLV-1 and HTLV-2 infections was undertaken in 50 seropositive or seroindeterminate blood donors. Modified serologic assays (2.3 Western blot that incorporate type-specific recombinant peptides) performed in 29 HTLV-1/2 positive and 21 HTLV-1/2 indeterminate donors with the 21e Western blot identified 25 as infected with HTLV-1, four with HTLV-2, five with untypable HTLV-1/2, 15 as HTLV-1/2 indeterminate, and one as seronegative. Polymerase chain reaction (PCR) analysis using DNA amplification of proviral pol and tax sequences from peripheral blood mononuclear cells confirmed HTLV-1 and HTLV-2 infections in all 2.3 Western blot seropositive donors; of the five serologically untypable donors, three were confirmed to be HTLV-1 positive, one HTLV-2 positive, and one negative by PCR. All of the seroindeterminate donors were also negative by PCR. Furthermore, HTLV-1 could be isolated in cocultures from 10 of 18 infected donors. Cell lines developed from two HTLV-1-infected donors were of T cell phenotype (CD2+, CD3+), exhibiting surface markers of activated CD4 cells (CD4+ CD25+ HLA-DR+). Thus, we provide evidence for the high seroprevalence of HTLV infection in blood donor population in Sao Paulo, Brazil compared with North American donors and propose a comprehensive serologic and genotypic diagnostic algorithm for HTLV-infected donors that has strong implications for counseling of these individuals.

PIP: Blood donors in Brazil have recently begun to be screened for infection with HTLV types 1 and 2. Of 351,639 blood donations screened in Sao Paulo from January 1992 to October 1993, 1063 positive and 2238 indeterminate samples were identified based upon serologic confirmation using the 21e Western blot. Detailed serologic, molecular, and virologic analysis, based upon a laboratory diagnostic algorithm for the characterization of HTLV-1 and HTLV-2 infections, was conducted upon 50 seropositive or seroindeterminate blood donors. 2.3 Western blot serologic assays, which incorporate type-specific recombinant peptides, performed in 29 HTLV 1/2 positive and 21 HTLV 1/2 indeterminate donors with the 21e Western blot identified 25 as infected with HTLV-1, 4 with HTLV-2, 5 with untypeable HTLV 1/2, 15 as HTLV 1/2 indeterminate, and 1 as seronegative. Polymerase chain reaction (PCR) analysis using DNA amplification of proviral pol and tax sequences from peripheral blood mononuclear cells confirmed HTLV-1 and HTLV-2 infections in all 2.3 Western blot seropositive donors. Of the 5 serologically untypeable donors, 3 were found to be HTLV-1-positive, 1 HTLV-2-positive, and 1 negative by PCR. All seroindeterminate donors were also negative by PCR. HTLV-1 could be isolated in cocultures from 10 of 18 infected donors.

Low prevalence of HTLV-II in Mayan Indians in the Yucatan Peninsula, Mexico.

Infection with HTLV-II is endemic in Amerindians, with prevalence ranging from 0.89% - 33%. To determine the prevalence of HTLV-II among indigenous Mayans in the Yucatan Peninsula of Mexico, 440 indigenous Mayans were recruited, all native to and residents of one of six Mayan communities in the Yucatan Peninsula, (Xohuayan n=144, Yaxachen n=101, Kanxoc n=84, Xocen n=40, Nabalan n=46 and X'calot n=25) between May, 1992 and June, 1993. All of the above are pre-Hispanic settlements located in tropical forest with no immigrations for over 50 years. Of the 440 indigenous Mayans, only one woman from the X'calot tribe (0.23%) was shown to be infected with HTLV-II. A high percentage of indeterminate results was found (22/439, 5%), three of which were accounted for by the husband and two children of the positive female case. PCR analysis followed by specific restriction digestion demonstrated the virus to be of the HTLV-IIb subtype, similar to that described in the Guaymi Indians from Panama. The presence of HTLV-II in the Mayan ethnos, and in other Amerindian populations supports the idea that HTLV-II is an ancestral virus in America and that it has been sustained in "closed" communities.

PIP: Although not consistently associated with any specific disease, infection with HTLV-II is nonetheless endemic among Amerindians, with a prevalence of 0.89-33%. Findings are presented from a study conducted to determine the prevalence of HTLV-II among indigenous Mayans in the Yucatan Peninsula of Mexico. 440 indigenous Mayans were recruited, all native to and residents of 1 of 6 Mayan communities in the Yucatan Peninsula between May 1992 and June 1993. All participants were drawn from pre-Hispanic settlements located in tropical forest without immigration for more than 50 years. Of the 440 subjects, only 1 woman from the X'calot tribe (0.23%) was found to be infected with HTLV-II. However, 22 of the remaining 439 (5%) results were indeterminate, of which 3 were accounted for by the husband and 2 children of the positive female case. Polymerase chain reaction analysis determined the virus to be of HTLV-IIb subtype, similar to that described among the Guaymi Indians of Panama. These findings support the argument that HTLV-II is an ancestral virus in America and that it has been sustained in closed communities.

Twenty-five years of HTLV type II follow-up with a possible case of tropical spastic paraparesis in the Kayapo, a Brazilian Indian tribe.

A longitudinal study, spanning 25 years and great demographic and cultural change, found a persistently high prevalence of human T-lymphotropic virus type II (HTLV-II) in the Xikrin Kayapo Indians of Brazil. More than 10% of the children continue to develop immune reactions to the virus in infancy, a sharp increase in seroprevalence occurs between ages 15 and 30 years, and prevalence in older woman still approaches 100%. This suggests that the major modes of transmission (breast milk and sexual activity) have not changed. The demonstration of stable maintenance of HTLV-II in one ethnic group makes migration theories of its dispersal more plausible. However, the infection may not be a negligible burden on population survival: at least 1 of 62 persons followed until age 40 years died of possible tropical spastic paraparesis (TSP).

Endemicity and phylogeny of the human T cell lymphotropic virus type II subtype A from the Kayapo Indians of Brazil: evidence for limited regional dissemination.

Long terminal repeat (LTR)-based restriction fragment length polymorphism (RFLP) analysis of human T cell lymphotropic virus type II (HTLV-II) from 17 seropositive Kayapo Indians from Brazil showed that all 17 samples contained a unique HTLV-IIa subtype (A-II). Additional RFLP screening demonstrated the presence of this subtype in two of three Brazilian blood donors and a Mexican prostitute and her child. In contrast, 129 samples from blood donors and intravenous drug users (IDUs) from the United States, two Pueblo Indian samples, five samples from Norwegian IDUs, and two samples from blood donors from Denmark were all found to be a different HTLV-IIa subtype (A-III). Phylogenetic analysis of two Kayapo and one Mexican LTR sequences showed that they cluster with a subtype A-II sequence from a Brazilian blood donor and with sequences from two prostitutes from Ghana and Cameroon. These results demonstrate that infection with the A-II subtype is endemic among the Kayapo Amerindians, has disseminated to non-Indian populations in Brazil, and is also present in Mexico. Furthermore, the A-II subtype does not appear to represent an origin for the HTLV-IIa infection in urban areas of the United States and Europe. This study provides evidence that HTLV-IIa may be a Paleo-Indian subtype as previously suggested for HTLV-IIb.

Molecular analysis of human T-cell lymphotropic virus type II from Wayuu Indians of Colombia demonstrates two subtypes of HTLV-IIb.

Studies of the genetic heterogeneity of human T-cell lymphotropic virus type II (HTLV-II) have revealed the presence of two genetic subtypes, termed HTLV-IIa and HTLV-IIb. The HTLV-IIb subtype encodes an immunodominant epitope present at the C-terminus of the extended Tax protein and, by using an LTR-based, restriction fragment-length polymorphism (RFLP) assay, can be further classified into IIb60-IIb5, with HTLV-IIb1 (Central Amerindian-like) and HTLV-IIb5 (North Amerindian-like) being characteristic subtypes for Native American Indians. To determine the antigenic and genetic heterogeneity among HTLV-II-infected South Amerindians, we used a Tax synthetic peptide immunoassay on serum, and RFLP and phylogenetic analysis on LTR sequences amplified from genomic DNA from four Wayuu Indians of Colombia. The Wayuu specimens displayed seroreactivity to the immunodominant epitope located in the extended Tax region, as predicted, and demonstrated genetic heterogeneity by the presence of both the IIB1 (Wyu1, Zuc31) and IIb5 (Wyu2, Zuc42) subtypes sequences within separate phylogroups represented by the Guaymi Indian (IIb1) and North Amerindian (IIb5) sequences, respectively. Sequence analysis showed that major LTR regulatory motifs and the cis-acting repressive elements in the LTR RNA secondary structure were relatively conserved in both Wayuu subtypes, but the predicted secondary structure of the rex response stem loop in the Wyu2 (IIb5) LTR sequence was 45 nucleotides (nt) and 95 nt longer than that observed in the Wyu1 (IIb1) and G12.1 (IIb1) LTR sequences, respectively. These results extend our knowledge of the genetic heterogeneity of HTLV-II in South Amerindians.

Viral-specific humoral immune responses following transfusion-related transmission of human T cell lymphotropic virus type-I infection.

The immunoglobulin (Ig) isotypes of antibodies to specific proteins of the human T cell lymphotropic virus type I (HTLV-I) were determined by Western blot analysis of serial specimens from six individuals who experienced HTLV-I seroconversion following blood transfusion; five remained asymptomatic carriers, while one developed HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) 32 weeks posttransfusion. Analysis of Ig isotypes demonstrated that while IgM was the most frequent early response to gag (p19, p24) and env (r21e) proteins within the first 3 months following transfusion, IgG and IgA responses could also be detected within this period. HTLV-I-specific antibody responses plateaued in all Ig isotypes, including IgM, within the next 4- to 6-month period following transfusion and persisted through the entire study period (> 4 years). Comparison of antibody profiles in Ig isotypes and IgG1 and IgG3 subclass among asymptomatic carriers and one individual who developed HAM/TSP demonstrated no evidence of isotypic prominence or IgG subclass restriction in either group. These results indicate the appearance of HTLV-I-specific IgM that persists even after the primary infection and suggest that such response does not appear to provide an early marker of seroconversion. Further, we found no evidence of isotypic prominence or restriction of the antibody response in recipients who remained asymptomatic compared to one who developed HAM/TSP.

Simultaneous confirmation and differentiation of human T-lymphotropic virus types I and II infection by modified western blot containing recombinant envelope glycoproteins.

A modified Western blot (WB) that includes both shared (r21e) and unique recombinant envelope proteins from human T-lymphotropic virus (HTLV) type I (rgp46I) and type II (rgp46II) was compared to conventional HTLV serologic tests in 379 United States blood donors and individuals residing in diverse geographic regions, and the specimens were categorized as positive (n = 158), indeterminate (n = 158), or negative (n = 63) for HTLV infection. Of the 158 HTLV-I/II-positive specimens (66 requiring radioimmunoprecipitation assay [RIPA] for confirmation), 156 reacted concordantly with r21e, gag, and either rgp46I or rgp46II, thus eliminating the need for RIPA in all but two specimens and yielding a test sensitivity of 98.7 percent. Of the 158 indeterminate and 63 negative specimens, none reacted with r21e and rgp46I or rgp46II, yielding a test specificity of 100 percent. Furthermore, analysis of an additional 184 consecutive specimens from a retrovirology reference laboratory demonstrated that the modified WB correctly identified 27 of 28 HTLV-I specimens and all 13 HTLV-II specimens, with a test sensitivity of 97.6 percent. None of specimens that were indeterminate or nonreactive in conventional WB and/or RIPA and none of the screening enzyme immunoassay-negative specimens reacted with r21e and either rgp46I or rgp46II, for a test specificity of 100 percent. Thus, the modified WB appears to be highly sensitive and specific for simultaneous detection and discrimination of HTLV-I from HTLV-II and has the advantage of being a one-step assay that is easily performed in all types of laboratory settings and allows rapid, reliable, and standardized testing for HTLV-I/II infection.

Human T lymphotropic virus type II (HTLV-II) infection among female prostitutes in Yucatan, Mexico.

The antibodies to human T-lymphotropic virus type I/II (HTLV-I/II) were determined in non-intravenous drug-using female prostitutes from Merida Yucatan, Mexico. Serum specimens from 282 female prostitutes collected during 1990 were tested initially by enzyme immunoassay and further confirmed by western blot assays. Of these, 5 (1.8%, 95% confidence interval 0.2 to 3.3) were shown to be HTLV-I/II positive (reactivity to p24gag and gp68/r21eenv). All five specimens were shown to be infected with HTLV-II by immunoassays using type-specific synthetic peptides and recombinant proteins. Long-term cell lines developed from two individuals demonstrated active viral replication and were of CD8 phenotype. Polymerase chain reaction analysis from four of these five prostitutes demonstrated HTLV-II-specific amplification of all four specimens, of which one was subtype a (HTLV-IIa) and three were subtype b (HTLV-IIb). These data show that HTLV-II is the predominant HTLV type among female prostitutes from the Yucatan.

Evidence for mother-to-child transmission of human T lymphotropic virus type II.

Serologic analysis of the children of 2 married human T lymphotropic virus type II (HTLV-II)-infected prostitutes demonstrated antibodies to HTLV-II in an 8-year-old boy whose only recognizable risk for HTLV-II infection was breast-feeding during his first 4 years of life. Limited sequence analysis of isolates infecting the mother and child demonstrated 100% identical sequences in the long terminal repeat (LTR65-297; 236 bp), pol4762-4919 (157 bp), and env5523-6003 (480 bp) regions (both isolates were subtype a), suggesting mother-to-child transmission. In contrast, isolates obtained from 2 other prostitutes from the same geographic region had sequences different from those of the first woman and her child, and the second and third women were infected with HTLV-II subtype b. Although vertical transmission of HTLV-II in this 8-year-old child cannot be conclusively ascertained, the probability is overwhelming that infection occurred through breast-feeding for an extended period of time.

Complete nucleotide sequence of an Amerindian human T-cell lymphotropic virus type II (HTLV-II) isolate: identification of a variant HTLV-II subtype b from a Guaymi Indian.

The complete nucleotide sequence of a human T-cell lymphotropic virus type II (HTLV-II) isolate from a Panamanian Guaymi Indian was determined and analyzed. When this new viral isolate (HTLV-IIG12) was compared with prototypic HTLV-IIMoT, the overall nucleotide sequence similarity was 95.4%, while the predicted amino acid sequence similarity was 97.5%. Although the overall percentage of nucleotide and amino acid identity with prototypic HTLV-IIMoT (subtype a) was high, HTLV-IIG12 displayed several distinctive features that defined it as an HTLV-II subtype b. However, there were several characteristics unique to this isolate, which included a cluster of nucleotide substitutions in the pre-gag region and changes in restriction enzyme sites within the pre-gag region and the gag, pol, env, and pX genes. In addition, two nucleotide changes in the C terminus of the Tax protein coding sequence inserted an Arg residue for a stop codon and appeared to result in a larger tax gene product in HTLV-IIG12. Although the HTLV-IIG12 isolate appears to be a variant of the prototypic HTLV-IIb, this information represents the first complete nucleotide sequence of any HTLV-II subtype b. These data will allow further studies on the evolutionary relationships between the HTLV-II subtypes and between HTLV-I and HTLV-II.

Immune responsiveness to the immunodominant recombinant envelope epitopes of human T lymphotropic virus types I and II in diverse geographic populations.

The heterogeneity of immune responsiveness to the immunodominant epitopes of human T lymphotropic virus (HTLV) types I (MTA-1(162-209)) and II (K-55(162-205)) were determined in natural infections with HTLV-I and -II from diverse geographic areas (n = 285). Of the HTLV-I specimens confirmed by polymerase chain reaction (PCR), all North American (n = 37) and Peruvian (n = 19) specimens reacted with MTA-1. Of HTLV-II specimens confirmed by PCR, 44 (96%) of 46 from North American blood donors, 28 (97%) of 29 from native Americans, and all from intravenous drug users (n = 29) reacted with K-55. Specimens from other geographic areas (Peru, 30; Brazil, 4; Mexico, 10; Italy, 5; Somalia, 13; Ethiopia, 17; Japan, 32; and Jamaica, 15) all reacted either with MTA-1 or K-55. By synthetic peptide-based serologic typing, all of these specimens could be typed as HTLV-I or -II. In addition to the direct implications of these findings for diagnostic purposes, these data provide indirect evidence for the conservation of immunodominant HTLVenv epitopes in diverse geographic populations.