Immunological Evolution of a Cohort of HIV-2 Infected Patients: Peculiarities of an Underestimated Infection

Background: Human Immunodeficiency Virus type 2 (HIV-2) affects a minority of patients in Italy; nevertheless, the increasing migratory flow from higher prevalence areas led to the spread of this virus into our Country. We evaluate clinical, viro-immunological, and therapeutic characteristics of patients with HIV-2 infection and HIV-1/HIV-2 dual-infection and the early treatment impact on overall survival and incidence of AIDS events.Methods: We retrospectively analyzed all HIV-2, and HIV-1/HIV-2 positive patients followed in a large Italian clinic from January 1987 to December 2020. We recorded demographic, viro-immunological, clinical, and therapeutic data. We performed a descriptive analysis followed by a longitudinal analysis to explore the factors associated with the CD4+ lymphocyte trend; lastly, we studied the possible predictors of death and AIDS in our cohort in a multivariable model.Results: 32 subjects were enrolled, 17 (53%) HIV-2 infected and 15 (46.8%) HIV-1/HIV-2 dual-infected; 12 patients were lost to follow up, while 3 died. We found a lack of HIV-2 viremia in 12/32 subjects (37.5%). Most of the patients at baseline had a good viro-immunological profile with HIV-2 RNA <200 copies/ml and CD4+ lymphocyte >200 cell/mcl. We found a CD4+ lymphocyte improvement over time, both in the absolute number (beta 472.61, 95%CI 383.05-562.18, p<0.001) and in percentage (beta 25.28, 95%CI 21.91 - 28.66, p<0.001). Nevertheless, subjects taking cART had CD4+ lymphocyte percentage increase over time, and this trend appeared significantly better than those who did not receive therapy. Lastly, in the multivariable model CD4+, T-cell count increase was negatively associated with AIDS (HR 0.34 95%CI 0.13-0.91, p=0.032).Conclusion: We found a higher prevalence of HIV-1/2 dual infection than in previous observations. Subjects with HIV-2 infection showed a favorable immunological condition at diagnosis, and the benefits of cART in those who received treatment are undiscussed. Moreover, our data suggest a different disease course based on age at diagnosis, as in HIV-1 infections. We encourage starting cART at diagnosis in HIV-2 patients, regardless of CD4+ lymphocyte, because even in the new cART era, CD4+ lymphocyte decrease remains the strongest predictor of death and AIDS also in this population.