Human T cell lymphotropic virus type I does not increase human immunodeficiency virus viral load in vivo

Neurological Aspects of HIV-1/HTLV-1 and HIV-1/HTLV-2 Coinfection

Simultaneous infection by human immunodeficiency viruses (HIV) and human T-lymphotropic viruses (HTLV) are not uncommon since they have similar means of transmission and are simultaneously endemic in many populations. Besides causing severe immune dysfunction, these viruses are neuropathogenic and can cause neurological diseases through direct and indirect mechanisms. Many pieces of evidence at present show that coinfection may alter the natural history of general and, more specifically, neurological disorders through different mechanisms. In this review, we summarize the current evidence on the influence of coinfection on the progression and outcome of neurological complications of HTLV-1/2 and HIV-1.

STLV-1 as a model for studying HTLV-1 infection

Few years after HTLV-1 identification and isolation in humans, STLV-1, its simian counterpart, was discovered. It then became clear that STLV-1 is present almost in all simian species. Subsequent molecular epidemiology studies demonstrated that, apart from HTLV-1 subtype A, all human subtypes have a simian homolog. As HTLV-1, STLV-1 is the etiological agent of ATL, while no case of TSP/HAM has been described. Given its similarities with HTLV-1, STLV-1 represents a unique tool used for performing clinical studies, vaccine studies as well as basic science.

Adult T-cell leukemia/lymphoma and acquired immunodeficiency syndrome - CD4+ T-cell malignancy in CD4+ T-cell deficient status: A paradox

CD4 counts along with viral loads are important parameters in the monitoring of human immunodeficiency virus (HIV) infection. Human T-cell lymphotropic virus type I (HTLV-I) is known to be an etiological agent for adult T-cell leukemia/lymphoma (ATLL). Coinfection of HTLV-I and HIV is well known in regions with high seroprevalence, and there is no published data in the Indian scenario. We present an interesting case of occurrence of CD4+ T-cell proliferation in a known beta thalassemia major with acquired HIV seropositivity accompanied by simultaneously increasing CD4+ counts and viral loads. Further workup revealed ATLL with an underlying HTLV infection.

HTLV-1/-2 and HIV-1 co-infections: retroviral interference on host immune status

The human retroviruses HIV-1 and HTLV-1/HTLV-2 share similar routes of transmission but cause significantly different diseases. In this review we have outlined the immune mediated mechanisms by which HTLVs affect HIV-1 disease in co-infected hosts. During co-infection with HIV-1, HTLV-2 modulates the cellular microenvironment favoring its own viability and inhibiting HIV-1 progression. This is achieved when the HTLV-2 proviral load is higher than that of HIV-1, and thanks to the ability of HTLV-2 to: (i) up-regulate viral suppressive CCL3L1 chemokine expression; (ii) overcome HIV-1 capacity to activate the JAK/STAT pathway; (iii) reduce the activation of T and NK cells; (iv) modulate the host miRNA profiles. These alterations of immune functions have been mainly attributed to the effects of the HTLV-2 regulatory protein Tax and suggest that HTLV-2 exerts a protective role against HIV-1 infection. Contrary to HIV-1/HTLV-2, the effect of HIV-1/HTLV-1 co-infection on immunological and pathological conditions is still controversial. There is evidence that indicates a worsening of HIV-1 infection, while other evidence does not show clinically relevant effects in HIV-positive people. Possible differences on innate immune mechanisms and a particularly impact on NK cells are becoming evident. The differences between the two HIV-1/HTLV-1 and HIV-1/HTLV-2 co-infections are highlighted and further discussed.

Predictive factors of HTLV1-HIV coinfections in French Guiana

French Guiana, the French territory most affected by human immunodeficiency virus (HIV) (1.3% of pregnant women), is also endemic for human T lymphotropic virus 1 (HTLV1). The objective of this study was to determine if the HTLV1/HIV coinfected patients had particular characteristics. All HIV-infected patients having a computerized medical file containing an HTLV1 serology were included: there were 1,333 HIV monoinfections and 76 HTLV1/VIH coinfections. The prevalence of HTLV1/HIV coinfections was 5.39%. Women (odds ratio [OR] = 1.91[1.13-3.24]), subjects > 40 years of age, and patients of Surinamese origin (OR = 2.65 [1.25-5.61]) were overrepresented among the coinfected. CD4 count at the time of diagnosis and viral loads were higher among coinfected patients. The clinical stage was not significantly different between the two groups. The number of CD4 cells was not higher among the coinfected, unlike most reports from the literature. Prevalence of HTLV1 among HIV-infected patients is high in French Guiana, and physicians seem to omit the prescription of serology for this potentially serious coinfection.

Simian T-cell lymphotropic virus type I alters the proviral load and biodistribution of simian retrovirus type 2 in co-infected macaques, supporting advancement of immunosuppressive pathology

The infection dynamics and pathology of a retrovirus may be altered by one or more additional viruses. To investigate this further, this study characterized proviral load, biodistribution and the immune response in Macaca fascicularis naturally infected with combinations of simian retrovirus type 2 (SRV-2) and simian T-cell lymphotropic virus type I (STLV-I). As the mesenteric lymph node (MLN) and the spleen have been implicated previously in response to retroviral infection, the morphology and immunopathology of these tissues were assessed. The data revealed a significant change in SRV-2 biodistribution in macaques infected with STLV-I. Pathological changes were greater in the MLN and spleen of STLV-I-infected and co-infected macaques compared with the other groups. Immune-cell populations in co-infected macaque spleens were increased and there was an atypical distribution of B-cells. These findings suggest that the infection dynamics of each virus in a co-infected individual may be affected to a different extent and that STLV-I appears to be responsible for enhancing the biodistribution and associated pathological changes in SRV-2 in macaques.

Higher mortality in HIV-2/HTLV-1 co-infected patients with pulmonary tuberculosis in Guinea-Bissau, West Africa, compared to HIV-2-positive HTLV-1-negative patients

OBJECTIVES

To investigate the effect of human T-lymphotropic virus type 1 (HTLV-1) on CD4 counts and mortality in tuberculosis (TB) patients with or without human immunodeficiency virus (HIV).

METHODS

A prospective study on 280 hospitalized patients with pulmonary TB was performed in Guinea-Bissau, 1994-1997, including HIV, CD4 counts and clinical outcome. We compared the CD4 count levels at the time of inclusion between HIV-negative and HIV-positive patients, with or without HTLV-1. Mortality was determined while patients were on treatment for TB.

RESULTS

Median CD4% was significantly higher in HIV-positive subjects co-infected with HTLV-1 compared to HTLV-1-negative patients. Two hundred thirty-three individuals were included in the analysis of mortality, and among HIV-negative subjects the mortality was 18.6/100 person-years . In HIV-2-positive HTLV-1-negative subjects the mortality was 39.5/100 person-years and in HIV-2/HTLV-1 co-infected patients it was 113.6/100 person-years (adjusted mortality rate ratio 4.7, 95% CI 1.5-14.4; p < 0.01). When all HIV-positive patients were analyzed together, corresponding mortality rates were 53.5/100 person-years and 104.8/100 person-years , respectively (not significant).

CONCLUSIONS

HIV/HTLV-1 co-infected patients hospitalized for pulmonary TB had a high mortality and had significantly higher CD4% compared to only HIV-positive subjects. This may imply that HTLV-1 has an adverse effect on the immune system in HIV-infected subjects, independently of the CD4 count, that makes co-infected subjects more vulnerable to TB.

Co-infection by human immunodeficiency virus type 1 (HIV-1) and human T cell leukemia virus type 1 (HTLV-1): does immune activation lead to a faster progression to AIDS?

BACKGROUND

Recent data have shown that HTLV-1 is prevalent among HIV positive patients in Mozambique, although the impact of HTLV-1 infection on HIV disease progression remains controversial. Our aim was to determine the phenotypic profile of T lymphocytes subsets among Mozambican patients co-infected by HIV and HTLV-1.

METHODS

We enrolled 29 patients co-infected by HTLV-1 and HIV (co-infected), 59 patients mono-infected by HIV (HIV) and 16 healthy controls (HC), respectively.For phenotypic analysis, cells were stained with the following fluorochrome-labeled anti-human monoclonal antibodies CD4-APC, CD8-PerCP, CD25-PE, CD62L-FITC, CD45RA-FITC. CD45RO-PE, CD38-PE; being analysed by four-colour flow cytometry.

RESULTS

We initially found that CD4+ T cell counts were significantly higher in co-infected, as compared to HIV groups. Moreover, CD4+ T Lymphocytes from co-infected patients presented significantly higher levels of CD45RO and CD25, but lower levels of CD45RA and CD62L, strongly indicating that CD4+ T cells are more activated under HTLV-1 plus HIV co-infection.

CONCLUSION

Our data indicate that HTLV-1/HIV co-infected patients progress with higher CD4+ T cell counts and higher levels of activation markers. In this context, it is conceivable that in co-infected individuals, these higher levels of activation may account for a faster progression to AIDS.

Co-Infection by the Human T-Cell Lymphotropic Virus Type II in Patients Infected by the Human Immunodeficiency Virus in Yucatan, Mexico

BACKGROUND

The HTLV-II infection has been reported in patients with HIV infection as often in asymptomatic as those with acquired immunodeficiency syndrome (AIDS). The aim of this study was to determine the prevalence of HTLV-II infection in a group of patients infected by HIV in our region, as well as determining the risk factors associated with HTLV-II transmission in this group of patients and its impact on the clinical course of HIV infection.

METHODS

A cross-sectional study was carried out to determine the prevalence of co-infection of HIV-1 and HTLV-II among 192 patients from Yucatán, México. Serum specimens were tested for HTLV antibodies by an enzyme-linked immunosorbent assay (ELISA) test. Positive results were confirmed and typed by Western blot. Twenty four (12.5%) patients were confirmed with antibodies for HTLV-II, but none had antibodies for HTLV-I. Specific risk factors for HTLV-II transmission were not identified.

RESULTS

Candidiasis (42 vs. 12%, p = 0.0004) and more than two defining entities of AIDS (37 vs. 18%, p = 0.02) was observed with greater prevalence in the group co-infected.

CONCLUSIONS

In our study, a higher frequency of candidiasis and a larger number of AIDS-defining pathologies were observed in the co-infected patients, suggesting that co-infection is associated with greater immunodeficiency.

Clinical Outcomes and Disease Progression among Patients Coinfected with HIV and Human T Lymphotropic Virus Types 1 and 2

The goal of this study was to investigate clinical outcomes and survival probabilities among persons coinfected with human immunodeficiency virus (HIV) and human T lymphotropic viruses types 1 and 2 (HTLV-I/II). A nonconcurrent cohort study of 1033 HIV-infected individuals was also conducted. Sixty-two patients were coinfected with HTLV-I, and 141 patients were coinfected with HTLV-II. HTLV-I/II coinfection was highly associated with African-American race/ethnicity, age of >36 years, higher CD4(+) T cell count at baseline and over time, and history of injection drug use. Coinfected patients were more likely to have neurologic complications, thrombocytopenia, respiratory and urinary tract infections, and hepatitis C. Despite having higher CD4(+) T cell counts over time, there was no difference in the incidence of opportunistic infections. Progression to both acquired immunodeficiency syndrome (AIDS; adjusted hazard ratio [aHR], 0.50; 95% confidence interval [CI], 0.25-0.98) and death (aHR, 0.57, 95% CI, 0.37-0.89) were slower among HTLV-II-coinfected patients, compared with time-entry- and CD4(+) T cell count-matched control subjects. In conclusion, HIV-HTLV-I/II coinfection may result in improved survival and delayed progression to AIDS, but this happens at the expense of an increased frequency of other of clinical complications.

A systematic review of the epidemiologic interactions between classic sexually transmitted diseases and HIV: how much really is known?

BACKGROUND

Many studies have explored the role of "classic" sexually transmitted diseases (STDs) in determining the pattern of HIV epidemics. However, the many different STDs may contribute in different ways, at different magnitudes.

GOAL

To review available studies on the bidirectional interactions of HIV and STDs to explore the extent of current knowledge on the different influences of the varied STDs in heterosexual HIV epidemics.

METHODS

Longitudinal studies on susceptibility and controlled studies on infectiousness and duration of disease identified on electronic databases through reference lists and citation indices up to the end of 1999 were systematically reviewed, including meta-analyses assessing the influence of STDs on susceptibility to HIV.

RESULTS

Studies have a clear publication bias with a significant result that hinders robust interpretation. However, genital ulcerative disease appears to have a greater impact than nonulcerative disease, and men are more affected than women by the effects of STDs on susceptibility to HIV. There is evidence that STDs increase the infectiousness of HIV from men to women, whereas the evidence is more equivocal for the infectiousness of women. Few studies identify the impact of different STDs, and there is a marked lack of studies investigating the impact of HIV infection on the transmission of other STDs.

CONCLUSIONS

A large body of work has measured the association between STDs and HIV. However, publication bias and gaps in the focus of studies mean that a detailed, quantitative understanding of the interaction requires much more attention.

Contribution of immune activation to the pathogenesis and transmission of human immunodeficiency virus type 1 infection

The life cycle of human immunodeficiency virus type 1 (HIV-1) is intricately related to the activation state of the host cells supporting viral replication. Although cellular activation is essential to mount an effective host immune response to invading pathogens, paradoxically the marked systemic immune activation that accompanies HIV-1 infection in vivo may play an important role in sustaining phenomenal rates of HIV-1 replication in infected persons. Moreover, by inducing CD4+ cell loss by apoptosis, immune activation may further be central to the increased rate of CD4+ cell turnover and eventual development of CD4+ lymphocytopenia. In addition to HIV-1-induced immune activation, exogenous immune stimuli such as opportunistic infections may further impact the rate of HIV-1 replication systemically or at localized anatomical sites. Such stimuli may also lead to genotypic and phenotypic changes in the virus pool. Together, these various immunological effects on the biology of HIV-1 may potentially enhance disease progression in HIV-infected persons and may ultimately outweigh the beneficial aspects of antiviral immune responses. This may be particularly important for those living in developing countries, where there is little or no access to antiretroviral drugs and where frequent exposure to pathogenic organisms sustains a chronically heightened state of immune activation. Moreover, immune activation associated with sexually transmitted diseases, chorioamnionitis, and mastitis may have important local effects on HIV-1 replication that may increase the risk of sexual or mother-to-child transmission of HIV-1. The aim of this paper is to provide a broad review of the interrelationship between immune activation and the immunopathogenesis, transmission, progression, and treatment of HIV-1 infection in vivo.

Late diagnosis of HIV infection in women seeking counseling and testing services in São Paulo, Brazil

We investigated whether women positive for human immunodeficiency virus (HIV) infection were late in seeking an anonymous HIV counseling and testing service, and the factors associated with a low CD4 count, in São Paulo, Brazil. Seventy-one consecutive HIV-1-seropositive women were interviewed by means of a structured questionnaire. Blood samples were collected for CD4+ T-lymphocytes count and determination of HIV-1 subtypes. Hepatitis C, syphilis, human T-cell lymphotrophic virus type I (HTLV-I), and HTLV-II infections were assessed by serologic tests. More than 70% of the women had less than 500 CD4+ cells/mm3 (20% below 200). Low CD4 count was significantly associated with sex work history, condom use in the last 6 months, and seropositivity to HTLV-I and syphilis. There was no relation between low CD4 count and HIV-1 subtypes. These results indicate that in Sao Paulo many women are seeking an anonymous testing service late in the course of HIV infection. The main purposes of anonymous HIV testing services - early diagnosis of infection, and counseling to prevent infection - are not being achieved. Another strategy for reducing the interval between infection and diagnosis in women must be addressed.

Quantification of HTLV type I and HIV type I DNA load in coinfected patients: HIV type 1 infection does not alter HTLV type I proviral amount in the peripheral blood compartment

Several reports suggest that HTLV-I/HIV coinfection may be associated with an increased risk of HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). In HTLV-I-monoinfected patients, the occurrence of HAM/TSP is associated with high peripheral blood HTLV-I proviral load. Using a real-time quantitative PCR assay, we assessed the proviral DNA load in peripheral blood mononuclear cells (PBMCs) from 15 asymptomatic HTLV-I-monoinfected patients, 15 HTLV-I-monoinfected patients with HAM/TSP, and 25 HTLV-I/HIV-1 coinfected patients, including 4 with HAM/TSP. We also measured HIV-1 proviral DNA load in PBMCs from the coinfected patients. The median HTLV-I proviral loads were 6,800 and 4,100 copies per 10(6) PBMCs in the asymptomatic monoinfected and coinfected groups, and 58,800 and 43,300 copies per 10(6) PBMCs in the monoinfected and coinfected patients with HAM/TSP, respectively. The difference between HTLV-I proviral loads in HAM/TSP and asymptomatic monoinfected patients was statistically significant (p < 0.0001), but there was no difference between the HTLV-I-monoinfected and HTLV-I/HIV-1-coinfected groups. There was no correlation between HTLV-I and HIV-1 proviral load. HTLV-I proviral load did not correlate with the CD4+ T lymphocyte count. Among patients with no HTLV-I disease, the median copy number of HTLV-I per 10(6) circulating CD4+ T cells was 114,000 in the coinfected group and 16,700 in the monoinfected group, but the difference was not significant (p = 0.089). These data do not confirm the hypothesis in which HIV-1 coinfection would increase HTLV-I proviral burden in the PBMCs. However, depletion of the CD4+ T cell subset, the main target of HTLV-I, could be counterbalanced by an up-regulation of HTLV-I replication or by greater resistance of HTLV-I-infected cells to HIV-1-induced destruction.

Human immunodeficiency virus/acquired immunodeficiency syndrome and tropical diseases: a Brazilian perspective

The paper summarizes recent findings on the epidemiology and pathogenesis of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/Aids), highlighting the role of co-infections with major tropical diseases. Such co-infections have been studied in the Brazilian context since the beginning of the Aids epidemic and are expected to be more frequent and relevant as the Aids epidemic in Brazil proceeds towards smaller municipalities and the countryside, where tropical diseases are endemic. Unlike opportunistic diseases that affect basically the immunocompromised host, most tropical diseases, as well as tuberculosis, are pathogenic on their own, and can affect subjects with mild or no immunosuppression. In the era of highly active anti-retroviral therapies (HAART), opportunistic diseases seem to be on decrease in Brazil, where such medicines are fully available. Benefiting from HAART in terms of restoration of the immune function, putative milder clinical courses are expected in the future for most co-infections, including tropical diseases. On the other hand, from an ecological perspective, the progressive geographic diffusion of Aids makes tropical diseases and tuberculosis a renewed challenge for Brazilian researchers and practitioners dealing with HIV/Aids in the coming years.

Localization of retrovirus in the central nervous system of a patient co-infected with HTLV-1 and HIV with HAM/TSP and HIV-associated dementia

Persons co-infected with HTLV-1 and HIV are at increased risk for neurologic disease. These patients may develop HAM/TSP and/or HIV-associated dementia. In this study, we localized cells infected with retrovirus in the central nervous system (CNS) of a patient with both HAM/TSP and HIV-associated dementia. HTLV-1 was localized to astrocytes and HIV to macrophage/microglia. There was no co-infection of a single cell phenotype in this patient. These data suggest that mechanisms other than co-infection of the same CNS cell may play a role in the development of neurologic disease in patients dual infected with HTLV-1 and HIV.

In vitro induction of HIV-1 replication in resting CD4(+) T cells derived from individuals with undetectable plasma viremia upon stimulation with human T-cell leukemia virus type I

Microbial coinfections have been associated with transient bursts of human immunodeficiency virus (HIV) viremia in patients. In this study we investigated whether human T-cell leukemia virus type I (HTLV-I), another human retrovirus that is prevalent among certain HIV-infected populations, can induce HIV-1 replication in patients who had been successfully treated with highly active antiretroviral therapy. We demonstrate that supernatants from HTLV-I-producing MT-2 cells can induce in vitro replication of HIV-1 from highly purified, resting CD4(+) T cells obtained from individuals with undetectable plasma viremia. Depletion of proinflammatory cytokines from the supernatants reduced, but did not abrogate, the ability to induce HIV-1 replication, indicating that other factors such as HTLV-I Tax or Env also have a role. The HTLV-I-mediated effect does not require productive infection: exposure to heat-inactivated HTLV-I virions, purified Tax protein, or HTLV-I Env glycoprotein also induced expression of HIV-1. Furthermore, we demonstrate that coculture of resting CD4(+) T cells with autologous CD8(+) T cells markedly inhibits the HTLV-I-induced virus replication. Our results suggest that coinfection with HTLV-I may induce viral replication in the latent viral reservoirs; however, CD8(+) T cells may play an important role in controlling the spread of virus upon microbial stimulation.

Spontaneous production of C-C chemokines by individuals infected with human T lymphotropic virus type II (HTLV-II) alone and HTLV-II/HIV-1 coinfected individuals

To investigate the immunological features of human T lymphotropic virus type II (HTLV-II) infection and specific mechanisms whereby HTLV-II might influence the progression of HIV-1 disease in coinfected individuals, we have analyzed the production of the C-C chemokines RANTES and macrophage inflammatory proteins 1alpha and 1alpha (MIP-1alpha and MIP-1beta) by PBMCs from HTLV-II-infected and HTLV-II/HIV-1-coinfected individuals. We observed spontaneous production of significant levels of MIP-1alpha and -1beta and, to a lesser extent, RANTES, from individuals infected with HTLV-II alone or with concomitant HIV-1 infection. Spontaneous C-C chemokine production was not observed in PBMCs from uninfected or HIV-1-infected individuals. Although HTLV-II is known to preferentially infect CD8+ lymphocytes in vivo, we observed that whereas RANTES was produced exclusively by the CD8+-enriched fraction, MIP-1alpha and -1beta were produced by both the CD8+-enriched and CD8+-depleted fractions of HTLV-II-infected PBMCs. RT-PCR demonstrated active expression of the HTLV-II regulatory protein Tax in the infected CD8+ T lymphocyte population, and it was further shown that Tax transactivates the promoters of MIP-1beta and RANTES. Therefore, it appears that HTLV-II stimulates the production of C-C chemokines both directly at a transcriptional level via the viral transactivator Tax and also indirectly. Although the HTLV-II-infected individuals in this study are all virtually asymptomatic, they certainly display an abnormal immune phenotype. Moreover, our findings suggest that HTLV-II, via chemokine production, would be expected to alter the progression of HIV-1 infection in coinfected individuals.

Intrinsic susceptibility of rhesus macaque peripheral CD4(+) T cells to simian immunodeficiency virus in vitro is predictive of in vivo viral replication

Previous studies with simian immunodeficiency virus (SIV) infection of rhesus macaques suggested that the intrinsic susceptibility of peripheral blood mononuclear cells (PBMC) to infection with SIV in vitro was predictive of relative viremia after SIV challenge. The present study was conducted to evaluate this parameter in a well-characterized cohort of six rhesus macaques selected for marked differences in susceptibility to SIV infection in vitro. Rank order relative susceptibility of PBMC to SIVsmE543-3-infection in vitro was maintained over a 1-year period of evaluation. Differential susceptibility of different donors was maintained in CD8(+) T-cell-depleted PBMC, macrophages, and CD4(+) T-cell lines derived by transformation of PBMC with herpesvirus saimiri, suggesting that this phenomenon is an intrinsic property of CD4(+) target cells. Following intravenous infection of these macaques with SIVsmE543-3, we observed a wide range in plasma viremia which followed the same rank order as the relative susceptibility established by in vitro studies. A significant correlation was observed between plasma viremia at 2 and 8 weeks postinoculation and in vitro susceptibility (P < 0.05). The observation that the two most susceptible macaques were seropositive for simian T-lymphotropic virus type 1 may suggests a role for this viral infection in enhancing susceptibility to SIV infection in vitro and in vivo. In summary, intrinsic susceptibility of CD4(+) target cells appears to be an important factor influencing early virus replication patterns in vivo that should be considered in the design and interpretation of vaccine studies using the SIV/macaque model.

Prevalences of HTLV-1 infection and associated risk determinants in an urban population in Guinea-Bissau, West Africa

OBJECTIVE

To assess the prevalence and modes of transmission of HTLV-1 infection in an adult population in Bissau, and to evaluate possible interactions between the pattern of spread of HTLV-1 and HIV-1/HIV-2.

DESIGN AND METHODS

Univariate and multivariate analyses were used to evaluate gender-and age-specific HTLV-1 prevalences as well as associated risk determinants in an adult population based on a serosurvey comprising 2127 individuals from 304 randomly selected houses in Bissau.

RESULTS

Using stringent Western blot criteria, the overall seroprevalence of HTLV-1 was 3.6%, 2.2% among men and 4.7% among women, respectively. One individual was seropositive to HTLV-2. The prevalence of HTLV-1, which increased with age in both genders, however more markedly among women, was >4 times higher (9.4%) among older individuals (>44 years of age) than among younger individuals (2.4%). Blood transfusion and HIV-2 seropositivity were independently associated with HTLV-1 seropositivity in men. Among women, both HIV-2 seropositivity and HIV-1 seropositivity were significant risk determinants. Having had sexual partners was associated with a fivefold increased risk among women but did not reach significance.

CONCLUSION

The adult population of Guinea-Bissau has a higher prevalence of HTLV-1 than reported from most other countries in West Africa. The gender-and age-specific pattern of spread of HTLV-1 closely resembles that observed for HIV-2, another retrovirus prevalent to the region. The close correlation between HTLV-1 and HIV-2 most likely reflects the shared risk factors related to sexual behavior. The implication of the high percentage of double infections in this population needs to be determined.

Viral Load Monitoring in HIV Infection

Measurement of HIV-1 viral load is now an accepted part of clinical practice for the determination of clinical prognosis and antiretroviral effectiveness in HIV infection. Consensus guidelines have been published on the appropriate use of this testing. Furthermore, recent advances in molecular technology have improved the sensitivity and reproducibility of viral load assays, and these improved assays have provided new insight into the pathogenesis of HIV disease. This article reviews new issues affecting viral load quantification, including viral subtypes, sex, compartmental differences, and other covariables.

Coinfection with HTLV-I and HIV: increase in HTLV-I-related outcomes but not accelerated HIV disease progression?

Human T-lymphotropic virus type I (HTLV-I) and HTLV-II have been postulated to accelerate disease progression in patients coinfected with HIV. However, recent evidence suggests that HTLV-II has no effect on HIV disease progression. In addition, it has recently been reported that HIV viral load was not increased in subjects coinfected with HTLV-I, suggesting that the biologic basis for the hypothesis does not exist. Several recent studies in Brazil, however, suggest that coinfection with HTLV-I and HIV has substantial medical consequences. For example, coinfection was associated with a higher CD4 lymphocytes count following adjustment for HIV viral load or HIV clinical stage. In addition, coinfected subjects have a high prevalence of clinical significant myelopathy. The effect of other putative viruses as cofactors in HIV disease progression is also discussed.

Factors secreted by human T lymphotropic virus type I (HTLV-I)-infected cells can enhance or inhibit replication of HIV-1 in HTLV-I-uninfected cells: implications for in vivo coinfection with HTLV-I and HIV-1

It remains controversial whether human T lymphotropic virus type I (HTLV-I) coinfection leads to more rapid progression of human immunodeficiency virus (HIV) disease in dually infected individuals. To investigate whether HTLV-I infection of certain cells can modulate HIV-1 infection of surrounding cells, primary CD4(+) T cells were treated with cell-free supernatants from HTLV-I-infected MT-2 cell cultures. The primary CD4+ T cells became resistant to macrophage (M)-tropic HIV-1 but highly susceptible to T cell (T)-tropic HIV-1. The CC chemokines RANTES (regulated on activation, normal T cell expressed and secreted), macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta in the MT-2 cell supernatants were identified as the major suppressive factors for M-tropic HIV-1 as well as the enhancers of T-tropic HIV-1 infection, whereas soluble Tax protein increased susceptibility to both M- and T-tropic HIV-1. The effect of Tax or CC chemokines on T-tropic HIV-1 was mediated, at least in part, by increasing HIV Env-mediated fusogenicity. Our data suggest that the net effect of HTLV-I coinfection in HIV-infected individuals favors the transition from M- to T-tropic HIV phenotype, which is generally indicative of progressive HIV disease.

HTLV-I and HTLV-II virus expression increase with HIV-1 coinfection

Coinfections with HIV-1 and HTLV-I or HTLV-II have been associated with unique immunophenotypes and an increased risk for development of neurodegenerative conditions. These findings may result from an increased HTLV-I or II viral burden in dually infected individuals. To investigate this possibility, HTLV-I/II tax/rex messenger RNA and viral antigen expression in peripheral blood mononuclear cells (PBMCs) were measured in 37 HTLV-I- or HTLV-II-infected subjects with or without HIV-1 coinfection. Tax/rex messenger RNA was detected in 14 of 24 PBMC samples from dually infected subjects, compared with only 1 of 13 PBMC samples from singly infected subjects (58% versus 7%; p < .003). The reverse transcription-polymerase chain reaction (RT-PCR) assay correlated with HTLV-I/II viral antigen detection in PBMC cultures but not with HIV-1 viral load levels in plasma. These findings may provide clues regarding the pathophysiologic consequences of HIV/HTLV-I and HIV/HTLV-II coinfections.

Isolation of sooty mangabey simian T-cell leukemia virus type I [STLV-I(sm)] and characterization of a mangabey T-cell line coinfected with STLV-I(sm) and simian immunodeficiency virus SIVsmmPBj14

It has been postulated that dual infections of humans with human immunodeficiency virus (HIV) and human T-cell leukemia/lymphotropic virus (HTLV) may potentiate disease progression. Counterparts of both of these pathogenic human retroviruses have been identified in various simian species indigenous to Asia and Africa, including sooty mangabey monkeys (Cercocebus atys). Using peripheral blood mononuclear cells (PBMC) from a mangabey naturally infected with both SIV and STLV-I, T-cell lines were established and maintained continuously for more than 3 years; these cell lines harbored only a newly identified mangabey STLV-I(sm) or both STLV-I(sm) and the acutely lethal variant SIVsmmPBj14. The dually infected cell line (FEd-P14) was established by de novo infection of mangabey PBMC with SIVsmmPBj14. This cell line was characterized by multiple assays which showed that structural proteins encoded by both viruses were produced in large quantities, but that the predominant viral glycoprotein on the cell surface was the STLV-I(sm) Env. Unusual interactions of the two retroviral glycoproteins were suggested by the formation of syncytia between Raji and the FEd-P14 cells, but not between Raji and simian cells infected with only one retrovirus or human cells infected with HTLV-I. The STLV-I(sm) strain obtained from the sooty mangabey was transmitted to normal macaque and mangabey PBMC and was shown to be unique by sequencing of the entire env gene. STLV-I(sm) from this African species was more closely related to "cosmopolitan" HTLV-I strains than to the prototypic STLV-I from an Asian pig-tailed macaque. In vitro and in vivo studies of STLV-I(sm) and SIVsmm, both isolated from a naturally infected mangabey monkey, may provide insight into disease induction and manifestations associated with coinfection by their human counterparts.

HIV viral load and CD4+ lymphocyte counts in subjects coinfected with HTLV-I and HIV-1

Reports indicate that there is a dissociation between markers of HIV disease progression and clinical stage among subjects coinfected with human T-cell lymphotropic virus type I (HTLV-I) and HIV. HTLV-I coinfection does not appear to affect HIV viral load, currently considered to be the best marker of HIV disease progression. We measured HIV RNA levels in stored serum samples from 23 subjects with coinfection and 92 subjects with HIV single infection and examined the correlation with the CD4+ lymphocyte count. Subjects were recruited from an ongoing HIV cohort study in Rio de Janeiro, Brazil. In both groups, CD4+ lymphocyte counts declined with increasing levels of HIV RNA. In a linear regression analysis adjusting for HIV RNA serum level, coinfected individuals had an estimated 78% higher CD4+ lymphocyte count than those with single infection. Simultaneous adjustment for beta2-microglobulin level increased the difference, with coinfected individuals having 146% (p = 0.005, 95% CI: 32% to 359%) higher CD4+ counts. These data suggest that the higher CD4+ lymphocyte counts associated with coinfection do not provide immunologic benefit and may reflect HTLV-I-associated nonspecific lymphocyte proliferation. The results of this and other studies suggest that the CD4+ count cutoff values used in making clinical decisions in HIV infection may not be appropriate in coinfection. As with HIV single infection, HIV virus load may be the optimal surrogate marker for subjects with coinfection.