High levels of T lymphocyte activation in Leishmania-HIV-1 co-infected individuals despite low HIV viral load

Abstract

Background: Concomitant infections may influence HIV progression by causing chronic activation leading to decline in T-cell function. In the Americas, visceral (AVL) and tegumentary leishmaniasis (ATL) have emerged as important opportunistic infections in HIV-AIDS patients and both of those diseases have been implicated as potentially important co-factors in disease progression. We investigated whether leishmaniasis increases lymphocyte activation in HIV-1 co-infected patients. This might contribute to impaired cellular immune function.

Methods: To address this issue we analyzed CD4+ T absolute counts and the proportion of CD8+ T cells expressing CD38 in Leishmania/HIV co-infected patients that recovered after anti-leishmanial therapy.

Results: We found that, despite clinical remission of leishmaniasis, AVL co-infected patients presented a more severe immunossupression as suggested by CD4+ T cell counts under 200 cells/mm3, differing from ATL/HIV-AIDS cases that tends to show higher lymphocytes levels (over 350 cells/mm3). Furthermore, five out of nine, AVL/HIV-AIDS presented low CD4+ T cell counts in spite of low or undetectable viral load. Expression of CD38 on CD8+ T lymphocytes was significantly higher in AVL or ATL/HIV-AIDS cases compared to HIV/AIDS patients without leishmaniasis or healthy subjects.

Conclusions: Leishmania infection can increase the degree of immune system activation in individuals concomitantly infected with HIV. In addition, AVL/HIV-AIDS patients can present low CD4+ T cell counts and higher proportion of activated T lymphocytes even when HIV viral load is suppressed under HAART. This fact can cause a misinterpretation of these laboratorial markers in co-infected patients.

Figure 1

Relationship between lymphocyte immune status and plasmatic HIV-1 viral load in Leishmania/HIV-1 co-infected patients during remission phase of leishmaniasis. A. Absolute counts of CD4⁺ T lymphocytes. B. Absolute counts of CD4⁺ T lymphocytes and viral load levels. C. Levels of CD38 expression on CD8⁺ T lymphocytes. D. CD38 expression on CD8⁺ T lymphocytes and viral load levels. American visceral leishmaniasis (AVL)/HIV-AIDS patients (solid squares), American tegumentary leishmaniasis (ATL)/HIV-AIDS patients (solid triangles), HIV-1 infected adults without leishmaniasis (HIV infected, solid diamonds) and healthy subjects (solid circles). Each point represents one subject. The horizontal bars express median.