Modulation of HTLV-I gene expression by HIV-1 Rev through an alternative RxRE-independent pathway mediated by the RU5 portion of the 5'-LTR

Human T-Cell Leukemia Virus Type 1-Related Diseases May Constitute a Threat to the Elimination of Human Immunodeficiency Virus, by 2030, in Gabon, Central Africa

The Joint United Nations Program on HIV/AIDS (UNAIDS) has adopted the Sustainable Development Goals (SDGs) to end the HIV/AIDS epidemic by 2030. Several factors related to the non-suppression of HIV, including interruptions of antiretroviral therapy (ART) and opportunistic infections could affect and delay this projected epidemic goal. Human T-Cell leukemia virus type 1 (HTLV-1) appears to be consistently associated with a high risk of opportunistic infections, an early onset of HTLV-1 and its associated pathologies, as well as a fast progression to the AIDS phase in co-infected individuals, when compared to HIV-1 or HTLV-1 mono-infected individuals. In Gabon, the prevalence of these two retroviruses is very high and little is known about HTLV-1 and the associated pathologies, leaving most of them underdiagnosed. Hence, HTLV-1/HIV-1 co-infections could simultaneously imply a non-diagnosis of HIV-1 positive individuals having developed pathologies associated with HTLV-1, but also a high mortality rate among the co-infected individuals. All of these constitute potential obstacles to pursue targeted objectives. A systematic review was conducted to assess the negative impacts of HTLV-1/HIV-1 co-infections and related factors on the elimination of HIV/AIDS by 2030 in Gabon.

Human T-cell lymphotropic virus 1/2 and human immunodeficiency virus antibodies identification among transactional sex workers and drug users in the Dominican Republic

BACKGROUND

Human immunodeficiency virus (HIV) increases the risk of acquiring human T-cell lymphotropic virus (HTLV) and subsequently HTLV's progression to tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). Existing data have exclusively reported generalized rates of HIV and HTLV-1 chronic viral infections in the Dominican Republic. To our knowledge, no published studies have focused on the rates of HTLV-1/2 in transactional sex workers and drug users, both higher risk groups, in the Dominican Republic.

METHODS

From December 2012 to April 2013 we conducted a study to estimate the seroprevalence of HTLV-1/2 immunoglobulin G (IgG) and HIV antibodies among transactional sex workers and intravenous drug users in Santo Domingo, Dominican Republic. Serological status was analysed with behaviour and demographic data.

RESULTS

We collected and analysed plasma from 200 participants with a mean age of 27.4 y in men and 25.2 y in women. The overall weighted seroprevalence of HTLV-1/2 IgG antibodies was 13.91% (95% CI 7.59 to 20.23) in men and 10.59% (95% CI 4.05 to 17.13) in women. The overall weighted seroprevalence of HIV-1 was 13.91% (95% CI 7.59 to 20.23%) in men and 17.65% (95% CI 9.55 to 25.75) in women. Male intravenous drug users had an exceptionally high rate of HTLV-positive HIV co-infection, at 75% (95% CI 44.99 to 105.01). Although there an association has been found between HTLV/HIV co-infections and sex work, the adjusted odds revealed a confounding role of HIV infection.

CONCLUSIONS

The results highlight the urgent need for enhanced public health preventive strategies among high-risk populations in the Dominican Republic and other resource-constrained Caribbean settings, as well as global adoption of routine screening for HTLV-associated infections, particularly in these high-risk, underserved populations.

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.

Rev and Rex proteins of human complex retroviruses function with the MMTV Rem-responsive element

Background

Mouse mammary tumor virus (MMTV) encodes the Rem protein, an HIV Rev-like protein that enhances nuclear export of unspliced viral RNA in rodent cells. We have shown that Rem is expressed from a doubly spliced RNA, typical of complex retroviruses. Several recent reports indicate that MMTV can infect human cells, suggesting that MMTV might interact with human retroviruses, such as human immunodeficiency virus (HIV), human T-cell leukemia virus (HTLV), and human endogenous retrovirus type K (HERV-K). In this report, we test whether the export/regulatory proteins of human complex retroviruses will increase expression from vectors containing the Rem-responsive element (RmRE).

Results

MMTV Rem, HIV Rev, and HTLV Rex proteins, but not HERV-K Rec, enhanced expression from an MMTV-based reporter plasmid in human T cells, and this activity was dependent on the RmRE. No RmRE-dependent reporter gene expression was detectable using Rev, Rex, or Rec in HC11 mouse mammary cells. Cell fractionation and RNA quantitation experiments suggested that the regulatory proteins did not affect RNA stability or nuclear export in the MMTV reporter system. Rem had no demonstrable activity on export elements from HIV, HTLV, or HERV-K. Similar to the Rem-specific activity in rodent cells, the RmRE-dependent functions of Rem, Rev, or Rex in human cells were inhibited by a dominant-negative truncated nucleoporin that acts in the Crm1 pathway of RNA and protein export.

Conclusion

These data argue that many retroviral regulatory proteins recognize similar complex RNA structures, which may depend on the presence of cell-type specific proteins. Retroviral protein activity on the RmRE appears to affect a post-export function of the reporter RNA. Our results provide additional evidence that MMTV is a complex retrovirus with the potential for viral interactions in human cells.

HIV-1-mediated syncytium formation promotes cell-to-cell transfer of Tax protein and HTLV-I gene expression

An important increase in luciferase activity was detected following co-culture of Jurkat T cells transiently transfected with an HTLV-I-LTR-driven reporter construct with HIV-1- and HTLV-I-infected cells. Production of infectious HTLV-I and expression of the HTLV-I envelope were not required for this HIV-1-dependent induction while it was severely hampered by anti-gp120 and anti-CD4 antibodies. The HTLV-I Tax protein and the TRE1 repeats were found to be necessary for the HIV-1-mediated enhancement of HTLV-I LTR activity in the co-culture assay. As these results suggested triple fusion events involving all three cell types and the intracellular transfer of Tax, we labelled each cell line with a distinct fluorescent probe. Through confocal microscopy, a number of resulting syncytia and cell clusters were indeed observed to be positive for all three probes. We are proposing a model in which HIV-1-mediated syncytium formation between HIV-1- and HTLV-I-infected cells and uninfected T cells forms a "bridge" or "tunnel" through which Tax from the HTLV-I-infected cells can diffuse and activate HTLV-I-LTR transcription.