Abortive T follicular helper development is associated with a defective humoral response in Leishmania infantum-infected macaques.

Leishmania infantum causes a chronic infectious disease named visceral leishmaniasis (VL). We employed a non-human primate model to monitor immune parameters over time and gain new insights into the disease. Rhesus macaques were infected with L. infantum and the T helper and B cell immunological profiles characterized during acute and chronic phases of infection. Parasite detection in visceral compartments during the acute phase was associated with differentiation of effector memory CD4 T cells and increased levels of Th1 transcripts. At the chronic phase, parasites colonized novel lymphoid niches concomitant with increased expression of IL10. Despite the occurrence of hypergammaglobulinemia, the production of parasite-specific IgG was poor, being confined to the acute phase and positively correlated with the frequency of an activated memory splenic B cell population. We noticed the expansion of a splenic CD4 T cell population expressing CXCR5 and Bcl-6 during acute infection that was associated with the differentiation of the activated memory B cell population. Moreover, the number of splenic germinal centers peaked at one month after infection, hence paralleling the production of specific IgG. However, at chronic infection these populations contracted impacting the production of parasite-specific IgG. Our study provides new insights into the immune events taking place in a physiologically relevant host and a mechanistic basis for the inefficient humoral response during VL.

Immune Thrombocytopenia Purpura Associated With COVID-19 Infection: A Challenging Diagnosis and Management.

The COVID-19 pandemic has posed unprecedented challenges in the field of medicine. Among its diverse manifestations, immune thrombocytopenia purpura (ITP) has emerged as a complication associated with COVID-19 infection. This case report presents a 90-year-old Caucasian male with a history of COVID-19 infection who developed acute hemoptysis, thrombocytopenia, and purpura. The diagnosis of ITP confirmed through exclusion criteria and clinical evaluation, occurred several weeks after the initial COVID-19 diagnosis. Differential diagnoses, including drug-induced thrombocytopenia, were carefully considered and excluded. The reported case highlights the importance of vigilance in identifying ITP as a potential complication of COVID-19 infection, even in the post-infection period. The timely initiation of appropriate treatment proved effective in managing the patient's condition. Collaboration among medical specialties facilitated comprehensive patient care, thereby reducing hospitalization periods. This case report serves as a crucial alert to physicians, underlining the need for ongoing monitoring of COVID-19 complications, especially as testing dwindles. By fostering interdisciplinary cooperation, healthcare professionals can optimize patient outcomes and effectively manage the multifaceted challenges associated with COVID-19 infection.