MORPHOLOGICAL ALTERATIONS CORRELATE WITH VIRAL PRESENCE IN  LYMPHOID TISSUE OF HIV-INFECTED PERSONS ON HIGHLY-ACTIVE  ANTIRETROVIRAL THERAPY (HAART).

Morente V, Alós L, Garcia F*, Caballero M**, Navarrete P, Pumarola T +, Plana M #, Gallart T#, Fumero E*, Gatell JM *, Miró JM*, Martinez A, Cardesa A. Departments of Pathology, Infectious Diseases(*), Immunology(#), Microbiology(+) and Otolaryngology(**), Hospital Clinic, IDIBAPS; University of Barcelona (Spain).

Background: Although plasma virus load (PVL) is actually used for monitoring HIV infection, key pathogenesis events and most viral replication take place in lymphoid tissues, in which the infection produces a progressive involution and destruction. In many cases, HAART result in a marked reduction of PVL. However, eradication is not a feasible goal so novel approaches are necessary to determine the nature of persistent immunodeficiency in this setting. Material and Methods: Fourteen HIV-infected persons in early stages of the infection (lymphocytes T CD4+ > 500 x10 ⁶/L and plasma viral load > 5000 copies/ml) were treated with HAART. Tonsil biopsies were performed before treatment and after 12 months of treatment. Each  sample of tonsillar tissue  was split in two parts. From one half  lymphoid tissue viral load (LTVL) was determined and the  other half was formalin-fixed and paraffin-embedded for histologic analyses. Hematoxylin-eosin stain and immunohistochemical procedures were performed, using the antibodies (Dako, Carpinteria, CA, USA): HIV-1 p24, CD20, CD21. The tonsil lymphoid tissue morphology was graded: I: follicular hyperplasia; II: follicular regression; III: absence of follicles. Total lymphoid tissue and follicular areas (FA) were measured by morphometry, calculating the FA proportion with regard to the total amount of lymphoid tissue. The expression of HIV-1 p24 protein was graded: 0: negative; 1: scattered and scarce positive cells; 2: small groups of positive cells with mild  intensity; 3: extensive and intense positive cells.The histologic results were compared with LTVL and blood lymphocyte T subsets. Results: Before treatment, 8 cases (57,1 %) were in histological stage III and the immunoexpression of p24 antigen was extense and intense in 12 cases (85,7%). After treatment, 8 cases were in histological stage II ( 57,1%) and 6 in stage I (42,8 %), and the immunoexpression of p24 antigen was negative in 6 cases (42,8%) but it was still positive in 8 cases ( 57,1 %) (6 in grade 2 and 2 cases in grade 1), mainly distributed in follicular dendritic cells. We have detected significantly differences between histological grade and proportion of FA of the lymphoid tissue before and after  HAART. These morphological  parameters have correlated with LTVL, the immunoexpression of p24 protein, the blood CD4+T cells increase and CD8+ T cells. Conclusion: There is a strong correlation between the morphological alterations  and the presence of HIV in the lymphoid tissue. Despite HAART, we have evidenced viral persistence in LT, mainly located in follicular dendritic cells, and lack of complete recovery of lymph node architecture even in patient with sustained undetectable PVL. The histological study of lymphoid tissue in HIV-infected persons could be of great value to establish the effectiveness of  new antiretroviral therapies.