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Visceral leishmaniasis (VL) and HIV co-infection (VL/HIV) has emerged as a significant public health problem in Ethiopia, with up to 30% of patients with VL co-infected with HIV. These patients suffer from recurrent VL relapses and increased mortality. Those with a previous history of VL relapses (recurrent VL/HIV) experience increased VL relapses as compared to patients with HIV presenting with their first episode of VL (primary VL/HIV). Our aim was to identify drivers that account for the higher rate of VL relapses in patients with recurrent VL/HIV (n = 28) as compared to primary VL/HIV (n = 21). Our results show that the relapse-free survival in patients with recurrent VL/HIV was shorter, that they had higher parasite load, lower weight gain, and lower recovery of all blood cell lineages. Their poorer prognosis was characterized by lower production of IFN-gamma, lower CD4+ T cell counts, and higher expression of programmed cell death protein 1 (PD1) on T cells.

Visceral leishmaniasis (VL) is a neglected tropical disease that causes substantial morbidity and mortality and is a growing health problem in Ethiopia, where this study took place. Most individuals infected with Leishmania donovani parasites will stay asymptomatic, but some develop VL that, if left untreated, is almost always fatal. This stage of the disease is associated with a profound immunosuppression, characterised by impaired production of Interferonγ (IFNγ), a cytokine that plays a key role in the control of Leishmania parasites, and high expression levels of an inhibitory receptor, programmed cell death 1 (PD1) on CD4+ T cells. Here, we tested the contribution of the interaction between the immune checkpoint PD1 and its ligand PDL-1 on the impaired production of IFNγ in VL patients. Our results show that in the blood of VL patients, not only CD4+, but also CD8+ T cells express high levels of PD1 at the time of VL diagnosis. Next, we identified PDL-1 expression on different monocyte subsets and neutrophils and show that PDL-1 levels were significantly increased in VL patients. PD1/PDL-1 inhibition resulted in significantly increased production of IFNγ, suggesting that therapy using immune checkpoint inhibitors might improve disease control in these patients.

Visceral leishmaniasis (VL) and HIV co-infection (VL/HIV) has emerged as a significant public health problem in Ethiopia, with up to 30% of VL patients co-infected with HIV. These patients suffer from recurrent VL relapses and increased mortality. Our aim was to assess whether VL/HIV co-infected patients with a previous history of VL relapses (recurrent VL/HIV) have a poorer prognosis as compared to HIV patients presenting with their first episode of VL (primary VL/HIV). Our results show that recurrent VL/HIV patients have a higher parasite load, higher mortality and that their relapse-free survival is significantly shorter. The poorer prognosis of recurrent VL/HIV patients is accompanied by lower weight gain and lower recovery of all blood cell lineages, as well as lower production of IFNγ, lower CD4+ T cell counts and higher expression levels of PD1 on T cells. Furthermore, our results show that prior history of VL relapse is an important risk factor for future relapse. Both CD4+ T cell count and parasite load were also associated with a higher risk of VL relapse, but neither of these was independently associated with relapse risk after adjustment for previous VL relapse history.We propose that in addition to the current treatments, novel interventions should be considered at the time of VL diagnosis in VL/HIV patients; and suggest that improved anti-leishmanial and antiretroviral treatments, as well as immune therapy, through PD1/PDL-1 blockade and/or through IFNγ administration, could result in more efficient parasite killing and thereby reduce the relapse rate and improve survival.

Visceral leishmaniasis (VL) is a neglected tropical disease that causes substantial morbidity and mortality and is a growing health problem in Ethiopia, where this study took place. Most individuals infected with Leishmania donovani parasites will stay asymptomatic, but some develop VL that, if left untreated, is almost always fatal. This stage of the disease is associated with a profound immunosuppression, characterised by impaired production of Interferonγ (IFNγ), a cytokine that plays a key role in the control of Leishmania parasites, and high expression levels of an inhibitory receptor, programmed cell death 1 (PD1) on CD4+ T cells. Here, we tested the contribution of the interaction between the immune checkpoint PD1 and its ligand PDL-1 on the impaired production of IFNγ in VL patients. Our results show that in the blood of VL patients, not only CD4+, but also CD8+ T cells express high levels of PD1 at the time of VL diagnosis. Next, we identified PDL-1 expression on different monocyte subsets and neutrophils and show that PDL-1 levels were significantly increased in VL patients. PD1/PDL-1 inhibition resulted in significantly increased production of IFNγ, suggesting that therapy using immune checkpoint inhibitors might improve disease control in these patients.

Summary Visceral leishmaniasis (VL) has emerged as a clinically important opportunistic infection in HIV patients, as VL/HIV co-infected patients suffer from frequent VL relapse. Here, we follow cohorts of VL patients with or without HIV in Ethiopia. By the end of the study, 78.1% of VL/HIV—but none of the VL patients—experience VL relapse. Despite a clinically defined cure, VL/HIV patients maintain higher parasite loads, lower BMI, hepatosplenomegaly, and pancytopenia. We identify three immunological markers associated with VL relapse in VL/HIV patients: (1) failure to restore antigen-specific production of IFN-γ, (2) persistently lower CD4+ T cell counts, and (3) higher expression of PD1 on CD4+ and CD8+ T cells. We show that these three markers, which can be measured in primary hospital settings in Ethiopia, combine well in predicting VL relapse. The use of our prediction model has the potential to improve disease management and patient care., Graphical abstract, Highlights • Visceral leishmaniasis patients co-infected with HIV suffer from frequent VL relapse • VL relapse is associated with low CD4+ T cell counts and low production of IFN-γ • VL relapse is associated with increased PD1 expression on CD4+ and CD8+ T cells • These three markers can predict whether and when these patients relapse, Patients with visceral leishmaniasis (VL) co-infected with HIV suffer from frequent VL relapse after successful anti-leishmanial treatment. Here, Takele et al. identify immune markers that can be used to predict when these patients will relapse. This has the potential to improve the disease management of these patients.