Seroepidemiologic survey for antibodies to human retroviruses in human and non-human primates in Brazil

The challenge of describing the epidemiology of HTLV in the Amazon region of Brazil

HTLV-1 was the first described human retrovirus and was soon found to be associated with severe clinical diseases, including a devastating lymphoma/leukemia and other inflammatory diseases. Although HTLV-2 is not usually pathogenic, it is widely distributed among native Indian populations in Brazil, particularly in the Amazon region of the country. Presently, HTLV spreads mainly by the sexual route and from mother to child, and virus persistence is an active biological factor aiding its transmission. Recently, the use of illicit drugs has been shown to be an additional risk factor, showing the influence of new habits on the epidemiology of HTLV in the region. Despite the detection of the virus in several different populations in the Amazon region of Brazil for almost 30 years, the exact prevalence of HTLV-1/2 is not well defined. The original biases in sampling and the selection of epidemiologically unsuitable populations were commonly repeated in most prevalence studies, generating unreliable and conflicting figures that do not represent the actual prevalence of HTLV. The improvements in clinical and laboratory facilities have resulted in the description of several clinical manifestations that were previously unknown in the region. The extent of the spread of the virus must be defined in this region, which is the largest geographical area of the country. As prophylaxis advances toward the use of vaccines against HTLV-1, it is important to determine who is at risk of being infected and developing a disease to successfully implement preventive measures, particularly as proposals are made to eradicate the virus among humans.

Epidemiological aspects of retrovirus (HTLV) infection among Indian populations in the Amazon Region of Brazil

HTLV was initially described in association with a form of leukemia in Japan and a neurological disease in the Caribbean. It was soon shown that HTLV-II was endemic among Amerindians and particularly among Brazilian Indians. The Amazon Region of Brazil is presently the largest endemic area for this virus and has allowed several studies concerning virus biology, the search for overt disease, epidemiological data including detailed demographic data on infected individuals, clear-cut geographic distribution, definition of modes of transmission and maintenance within small, epidemiologically-closed groups, and advances in laboratory diagnosis of the infection. A new molecular subtype named HTLV-IIc was further described on the basis of genome sequencing and phylogenetic analysis. This subtype is present in other areas of Brazil, indicating that the virus is additionally both a valuable marker for tracing past human migration routes in the Americas and a probable marker for social habits of the present human population. HIV, the other human retrovirus, is still not prevalent among indigenous communities in the Brazilian Amazon, but these groups are also easy targets for the virus.

Inhibitory effect of extracts of Brazilian marine algae on human T-cell lymphotropic virus type 1 (HTLV-1)-induced syncytium formation in vitro

Extracts from four species of Brazilian marine algae collected from the Rio de Janeiro State coast were screened to determine the inhibitory effect on HTLV-1-induced syncytium formation. Before performing the syncytium inhibition assay the 50% cytotoxic dose (CyD50) of the algal extracts was evaluated. The antiviral test was carried out in HeLa cells co-cultured with HTLV-I infected T-cell line (C91/PL cells) in the presence of marine algal extracts in the concentration inferior to that corresponding to the CyD50. It was observed that co-cultured cells exposed to Ulva fasciata extract showed 60.2% syncytium inhibition at a concentration of 2.5%. At 5% concentration, Sargassum vulgare and Vidalia obtusiloba extracts presented 78.8 and 76% syncytium inhibition, respectively. The best inhibitory activity was observed with Laminaria abyssalis that presented 100% syncytium inhibition at a concentration of 2.5%. This work shows that extracts of marine algae, mainly L. abyssalis extract, are able to inhibit the cell-to-cell contact essential for the spreading of the virus and could be useful to prevent the infection.

Os vírus linfotrópicos de células T humanos (HTLV) na última década (1990-2000): aspectos epidemiológicos

Vinte anos após o isolamento do vírus linfotrópico humano tipo I, muitos aspectos epidemiológicos, patogênicos e filogenéticos já estão esclarecidos. Sabe-se que em regiões endêmicas a prevalência aumenta com a idade e é maior no sexo feminino. Três patologias estão claramente relacionadas a ele: paraparesia espástica tropical / mielopatia associada ao HTLV, leucemia de células T do adulto e uveíte. Os modos de infecção, semelhantes aos dos outros retrovírus, são: transfusão de sangue, relações sexuais não protegidas, transplacentária e durante o aleitamento materno. A história natural das doenças relacionadas ao HTLV-I ainda não está bem estabelecida. O risco de portadores da infecção desenvolverem patologias depende de mais estudos de incidência para serem corretamente estimados. Menos se conhece sobre o HTLV-II. A despeito do alto grau de homologia entre os dois tipos, os vírus interagem de forma bem diversa com os infectados, não havendo uma associação clara de doença com o HTLV-II. Relatos recentes têm apontado sua participação em casos de mielopatia crônica semelhante à TSP/HAM. As implicações incertas do prognóstico para pessoas infectadas pelo vírus linfotrópico humano (HTLV-I/II) e suas formas de transmissão constituem um problema de saúde pública, principalmente em áreas consideradas endêmicas para esse vírus.

A disseminação da epidemia da AIDS no Brasil, no período de 1987-1996: uma análise espacial

As taxas médias de incidência da AIDS em adultos no Brasil foram estimadas para os períodos 1987-89, 1990-92 e 1993-96, segundo o município de residência dos casos. Nas análises foram utilizadas as variáveis "tamanho da população do município de residência"; "proporção de população que vive em área urbana" e "concentração de pobreza", estratificando-se por sexo e categoria de exposição. A Região Sudeste apresenta menor ritmo de crescimento em contraste com os aclives acentuados das regiões Norte e Sul, do 2º ao 3º intervalo. Cotejando-se as variações das taxas de incidência de 1990-92 a 1993-96 por região ou tamanho de população, obtém-se maiores aumentos relativos entre as mulheres. Nas cidades grandes, a categoria "homo/bissexuais" prevalece, decrescendo proporcionalmente à medida que cresce o número de casos por transmissão heterossexual. Nos municípios médios predominam os usuários de drogas injetáveis e nos menores há aumento dos casos por transmissão heterossexual. A epidemia - ainda fenômeno urbano - dá sinais de expansão nos municípios rurais, intensificando-se naqueles situados abaixo do limite crítico regional do índice de pobreza. Há disseminação crescente da epidemia nos municípios mais pobres.

HTLV-I-associated myelopathy/tropical spastic paraparesis in Brazil: a nationwide survey. HAM/TSP Brazilian Study Group

To study the epidemiology of HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in Brazil, we conducted a nationwide survey between March 1994 and April 1995. Five centers from three regions of the country participated, enrolling 163 patients. Most patients came from the northeastern and southeastern regions (93.2%). Most enrollees were white women, 42.9% and 64.4%, respectively. The most common risk factors for infection included a history of venereal diseases (30.6%) and blood transfusion (21.6%). The median age at the beginning of the disease was 42 years. The main neurologic findings were spastic paraparesis, widespread brisk tendon jerks, bilateral Babinski's sign, and bladder dysfunction. Some interregional differences reached statistical significance. The ratio of females over males increased from south to north. In addition, in both southern and southeastern regions, whites prevailed, whereas in the northeast, mulattos predominated. This follows the normal distribution of the population in these regions. A significantly higher rate of venereal diseases was found in the southeast compared with the other regions studied. A history of intravenous drug use was more frequent among patients as the sample moves south. Finally, a fluctuating course of the disease was proportionally more frequent in the southern region.

HTLV-I infection among relatives of patients with adult T-cell leukemia/lymphoma in Brazil: analysis of infection transmission

We examined the presence of HTLV-I infection among 66 family members of 13 patients with well documented ATL to investigate the routes of HLTV-I transmission in a Southeast region of Brazil. HTLV-I infection was screened by an enzyme immunossay (ELISA) test and all repeatedly positive or indeterminate ELISA samples were further tested by a Western-Blot (WB) technique. Indeterminate and inconclusive WB samples were confirmed by a polymerase chain reaction (PCR). ELISA results showed that 40 (60.6%) individuals were not infected; 16 (24.2%) were positive; and 10 (15.2%) were undetermined. Among 16 ELISA positive subjects, 14 (87.5%) were confirmed to be positive by WB while 2 (12.5%) showed inconclusive results. Based on the laboratory data, questionnaire analysis, and family/epidemiological studies, we concluded that HTLV-I vertical transmission occurred in 6 of the 13 families. In 3 of these 6 families, the horizontal transmission also could be demonstrated. An isolated horizontal transmission was detected in one family, and in 6 families we did not find any infected family member. All HTLV-I-infected persons were clinically asymptomatic. The occurrence of an effective HTLV-I vertical transmission detected by the present study suggest that HTLV-I infection is endemic in the Southeast region of Brazil. Consistent with the modes of transmission, the HTLV-I antibody seroprevalence was greater in relatives of ATL patients than in the general blood donor Brazilian population (0.4%). In addition, the present data suggest that HTLV-I carries a high infectivity rate but a low virulence.

[HTLV-I/II infection in the state of Bahia]

The city of Salvador, capital of Bahia, presents a population with the highest prevalence of HTLV-I infection in Brazil. Until now, only one study has investigated this infection in other cities of this state, even though by using a small sample. With objective to evaluate the prevalence of HTLV-I/II antibodies in four cities of the state of Bahia. Serum samples from 1,539 individuals who lived in Catolândia, Ipupiara, Jacobina and Prado were screened by ELISA, and repeatedly reactive samples confirmed by Western Blot. Forty-seven (3.1%) samples were positive by ELISA, and 44 of them were tested by Western blot: 5 (0.3%) were positive, 8 (0.5%) were indeterminate (all of them from Jacobina) and 31 were negative. The overall prevalence of HTLV-I antibodies was 0.3%. This prevalence varied from 0.0% (Prado) to 0.7% (Jacobina), but differences were not statistically significant (p > 0.21). None of these individuals presented HTLV-II antibodies. Jacobina showed the highest prevalence of HTLV-I infection among the cities studied, although the overall prevalence was low. In conclusion, further epidemiological, clinical and virological studies will be of paramount importance to obtain a better understanding of the natural history of this infection in Jacobina.

Occurrence and frequency of transmission of naturally occurring simian retroviral infections (SIV, STLV, and SRV) at the CIRMF Primate Center, Gabon

Among the primates held at the CIRMF Primate Center, Gabon, no serological sign of SIV infection could be demonstrated in 68 cynomolgus monkeys, 60 chimpanzees, nine gorillas, and 12 sun-tailed monkeys, while seven of 102 mandrills and six of 24 vervets were infected with SIV. Six mandrills, seven vervets and ten cynomolgus monkeys exhibited a full HTLV type 1 Western blot profile. The sera of two gorillas and one chimpanzee presented with a positive but not typical HTLV Western blot profile. The sera of the gorillas lacked p24 antibodies, and the chimpanzee had a Western blot profile evocative of HTLV-II. All attempts to amplify viruses from these animals by PCR were unsuccessful. Two other chimpanzees and seven gorillas presented with indeterminate HTLV Western blot profiles. In the mandrill colony, only male animals were STLV seropositive and no sexual transmission to females was observed. SIV infection was also more frequent in male than female mandrills and sexual transmission appeared to be a rare event. No SRV infection was observed in macaques.

Studies on prevalence of Strongyloides infection in Holambra and Maceió, Brazil, by the agar plate faecal culture method

Prevalence of Strongyloides stercoralis infection in three areas of Brazil was surveyed by a recently developed faecal culture method (an agar plate culture). The Strongyloides infection was confirmed in 11.3% of 432 subjects examined. The diagnostic efficacy of the agar plate culture was as high as 93.9% compared to only 28.5% and 26.5% by the Harada-Mori filter paper culture and faecal concentration methods, when faecal samples were examined simultaneously by these three methods. Among the 49 positive samples, about 60% were confirmed to be positive only by the agar plate culture. These results indicate that the agar plate culture is a sensitive new tool for the correct diagnosis of chronic Strongyloides infection.

Tropical spastic paraparesis/HTLV-I-associated myelopathy in Brazil

Brazil, the largest Latin American country, is highly heterogeneous, both demographically and socioeconomically. The overall human T-cell lymphotropic virus type I (HTLV-I) seroprevalence among blood donors is approximately 0.45%. These rates are highly variable, from 0 to 1.8%. Since 1989, many series of tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM) cases have appeared in the literature, with high variation in the prevalence of HTLV-I among TSP patients (14.7-57%). The main clinical features of Brazilian TSP/HAM are similar to those in other endemic countries, but sensory signs are more frequent. Recently, the presence of peripheral nerve and muscular involvement has been characterized. The first nationwide study on the disease has been recently completed: it enrolled 163 patients and concluded that TSP/HAM is common in Brazil, mainly in the northeast and southeast regions; it predominates among women and whites; the most important risk factors for infection are sexual promiscuity and blood transfusion; and, although a remarkably uniform disease throughout the country, some statistically significant differences were detected, such as a higher proportion of females over males in the northeast region, a higher proportion of whites the southeast and the south and mulattos in the northeast, and, finally, a high rate of venereal diseases in the southeast region and of intravenous drug use in the south. Brazil seems to be a perfect setting for future epidemiologic, clinical, basic, and therapeutic studies on TSP/HAM.

No relationship between HTLV-1 infection and filariasis--Serological study on patients with filariasis in Recife, Brazil

The seroprevalence of antibodies against human T-cell leukemia virus was determined by ELISA in 68 patients with filarial infestation living in an endemic area. The total seropositivity was 2.9% and the HTLV-1-positive cases were detected in 2 microfilaremic patients 12 and 40 years old. This value is very close to that obtained for healthy individuals in the same region and age groups. This result suggests that there is no relationship between filariasis and HTLV-1 infection as previously proposed.

Human T cell leukemia virus type 1 (HTLV-1) antibodies in healthy populations and renal transplanted patients in the north-east of Brazil

The seroprevalence of human T cell leukemia virus type 1 (HTLV-1) infection was investigated in Brazilians (570): native inhabitants (298) and descendants from Japanese (272) living in Recife and its neighborhoods--North-east of Brazil. Furthermore, polytransfused renal transplanted patients (54) were also examined for the serological status to this virus. The seropositivity to HTLV-1, screened by enzyme-linked immunosorbent assay (ELISA), was low: 1.34% for the local population and 0.73% for the descendants from Japanese. However, the seropositivity for the renal transplanted patients was found to be 11.1%. This higher value suggests that this retrovirus infection seems to be of importance in this clinical condition.

HTLV-I and HTLV-II infections among HIV-1 seropositive patients in Sao Paulo, Brazil

To estimate the presence of, and the risk factors for HTLV-I and HTLV-II infections among HIV-1 infected subjects in Sao Paulo, Brazil, a serosurvey was performed in 471 HIV-1 infected patients, including 216 intravenous drug addicts (IVDA), 229 homosexual/bisexual men, and 26 with other risk factors. Serum samples were screened for HTLV seroreactivity by ELISA; reactive samples were analyzed by Western Blot (WB), using whole HTLV-I lysate as antigen. To confirm and discriminate HTLV-I and HTLV-II infections, sera presenting any bands on WB were further analyzed by a WB containing recombinant HTLV-I and HTLV-II proteins (WB 2.3), and by enzyme immunoassays using synthetic peptides specific for envelope proteins (Synth-EIA). In 22 cases, cell samples were available for polymerase chain reaction (PCR) studies. On WB, 114 sera were reactive and, of these, 37 and 25 were concordantly positive on both WB 2.3 and Synth-EIA procedures for HTLV-I and HTLV-II specific antibodies, respectively; 37 specimens were negative on both assays, and 15 gave discordant or indeterminate results. PCR findings confirmed concordant results obtained in the discriminatory serological assays. The prevalence rates of HTLV-I and HTLV-II infections were 15.3% and 11.1% in IVDA, and 0.9% and 0.4% in homosexual/bisexual men, respectively. No case of HTLV-I/HTLV-II co-infection was found.

Clinical and demographic features of HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) in Rio de Janeiro, Brazil

In Rio de Janeiro (RJ) most cases of paraparesis of obscure origin are associated with the human T-cell lymphotropic virus type I (HTLV-I). Thirty-four consecutive patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) from RJ were evaluated. Most patients came from low socio-economic levels. There was no difference in terms of gender. The main affected racial group was white. A history of sexually transmitted diseases was a major risk factor for HAM/TSP and a positive serology for syphilis was found in 26.5% of the patients. The major clinical findings were of a spastic paraparesis with generalized brisk tendon jerks and bilateral Babinki's sign. Sensation was abnormal in 25 patients (73.5%) and five (14.7%) had a sensory level. Three patients (8.8%) had optic atrophy. The cerebrospinal fluid showed a lymphocytic pleocytosis with a mean total protein content of 0.4 g/litre, and an increased intrathecal IgG synthesis in 59.4% of patients. HAM/TSP and multiple sclerosis (MS) occur indigenously in RJ and some HAM/TSP cases can be sometimes confused with MS. Therefore we propose that, in places where MS coexist with HAM/TSP, HTLV-I antibodies should be sought routinely in those MS suspected cases with prominent spastic paraparesis.

Spastic paraparesis of obscure origin. A case-control study of HTLV-I positive and negative patients from Rio de Janeiro, Brazil

In order to find clinical findings that could significantly discriminate between HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and HTLV-I negative spastic paraparesis of obscure origin (SPOneg) prior to serological testing, and to find risk factors significantly associated with HAM/TSP we devised a case-control study. Sixty consecutive SPO patients were studied without previous knowledge of their HTLV-I serological status. Thirty-four (56.7%) turned out to be HTLV-I positive and 26 (43.3%) HTLV-I negative. HTLV-I infected patients tended to have more commonly motor and bladder disturbances at the beginning of their illness and a disease that was still in progression at the time of the examination. Bladder dysfunction, constipation and penile impotence, and more widespread pyramidal signs, were also more frequent during the whole course of their illness. Likewise, an increased intrathecal synthesis of IgG was found more often in the HTLV-I positive group. The only risk factor for HTLV-I infection significantly associated to HAM/TSP was a prior history of sexually transmitted diseases. These results suggest that, at least in RJ, HAM/TSP might be mainly sexually acquired.

[The epidemiological aspects of HIV/AIDS in Brazil]

A trend analysis of the AIDS epidemics in Brazil is presented, emphasizing temporal changes among the population groups most affected. Regional comparisons as well as projections of the extension of HIV infection and AIDS cases are also reported. Amongst the most relevant conclusions the alarming increase of cases in heterosexual populations and intravenous drug users is emphasised, specially in the southeast region.

Serologic confirmation of simian T-lymphotropic virus type I infection by using immunoassays developed for human T-lymphotropic virus antibody detection

Serum specimens from diverse species of Old World monkeys, categorized as seropositive (n = 97) or seronegative (n = 23) for human T-lymphotropic virus (HTLV) infection, were tested by using recombinant env-spiked Western immunoblot assays and synthetic peptide assays for simultaneous detection and discrimination of simian T-lymphotropic virus (STLV) infection. Of the 97 seropositive specimens, 93 reacted with the recombinant transmembrane (r21env) protein and 90 reacted with a recombinant, MTA-1, derived from the central region of the external glycoprotein of HTLV-I (rgp46env), thus yielding test sensitivities of 96 and 93%, respectively. While 1 of the 23 negative monkey specimens reacted with r21env, none reacted with rgp46env, for overall specificities of 96 and 100%, respectively. Analysis of synthetic peptide-based immunoassays demonstrated that while 85 of 97 (88%) seropositive specimens reacted with HTLV-I-specific epitope (p19gag), none of the specimens reacted with HTLV-II-specific epitope (gp52env). These results show that recombinant envelope-spiked Western blots provide a simple means for serologic confirmation of STLV-I infection and that type-specific synthetic peptides can be used to confirm the virus type in seropositive monkey specimens.

HTLV-I infection and neurological disease in Rio de Janeiro

Fifty patients with chronic neurological diseases attending a clinic in Rio de Janeiro, Brazil, were examined for evidence of HTLV-I infection. Fifteen of 27 with progressive paraparesis of obscure origin had antibodies to HTLV-I in high titre in their serum samples, and 10 of 13 studied had antibodies in their cerebrospinal fluid. The clinical features of the antibody positive patients were similar to those of patients with HTLV-I associated myelopathy from other countries except that half of the Brazilian patients were white. Seven patients had multiple sclerosis and one of these had antibodies to HTLV-I in the serum. None of the eight patients with motor neuron disease and four with polymyositis had HTLV-I antibodies in their serum samples.

The epidemiology of HTLV-I infection

It has been 10 years since the discovery of the human T-cell lymphotropic virus type I (HTLV-I), the first human retrovirus. During the past decade, significant progress has been made in understanding the transmission of the virus and defining its geographic distribution. It has been shown conclusively that HTLV-I is a causal factor in the induction of both adult T-cell leukemia/lymphoma and HTLV-I-associated myelopathy. However, the pathogenesis of each of these conditions is not clear, and in the light of the evidence of immune dysfunction seen among carriers of the infection, it is likely that other associated diseases will be identified. The challenge in the next decade will be to develop and implement therapeutic interventions among carriers to prevent such diseases as well as to curtail transmission within endemic populations.

Adult T-cell leukaemia/lymphoma in Brazil and its relation to HTLV-I

In a series of fourteen patients with adult T-cell lymphoma-leukaemia (ATLL) in Brazil the main features were lymphadenopathy, hepatosplenomegaly, hypercalcaemia, and high leucocyte counts, with abnormal lymphoid cells which had irregular nuclei. The series included the youngest patient with ATLL so far (18 months). Analysis with monoclonal antibodies showed a mature T-cell phenotype (CD4+, CD8-). Antibodies to HTLV-I and/or integration of HTLV-I proviral DNA were found in eleven patients. In the other three HTLV-I DNA could not be demonstrated even by means of the polymerase chain reaction; they therefore had HTLV-I-negative ATLL. This report of ATLL in Brazil corroborates serological reports that HTLV-I may be endemic in some parts of that country. Follow-up studies are required to identify precisely the main route of transmission of HTLV-I in South America and the risk factors for the development of ATLL in carriers.