Infection [14]. Specific T helper cells are crucial for the anti-HIV immune response, since they provide help to B and CD8+ cells. A recent study in SIV-infected macaques has shown that depleting CD4+ KS-176 chemical information during PHI worsen the infection [15]. HIV preferentially infects HIV-specific CD4+ lymphocytes [16]. The efficacy of a specific immune response is due to CD4+ and CD8+ T cell clones with multiple effectors functions, such as production of different cytokines and chemokines, activity of 1655472 costimulatory molecules, capacity to perform degranulation and to express cytotoxic molecules (e.g., perforin) [17,18]. These cells, defined “polyfunctional”, are present at relatively low frequency in HIV+ patients, but at high frequency in the blood of patients who control the virus, such as long term non progressors (LTNPs) or “elite controllers”, where the ?presence of HIV-specific polyfunctional CD8+ lymphocytes is associated with spontaneous control of viral replication [19,20,21,22]. Very few data exist on the polyfunctionality of T cells immediately after primary infection [23], and we were interesting in investigating this aspect in a longitudinal manner. Regulatory T cells (Tregs) have a crucial importance, being a viral reservoir, as shown by the presence of HIV-DNA in resting CD4+ Tregs from patients assuming HAART [24]. However, their role during the infection remains PHCCC unclear. CD4+ Tregs might be important for the reduction of immune activation after PHI or even in chronic infection [25]. During chronic infection they could cause the deregulation of HIV-specific response [26], so favoring the progression of the infection, and a decrease of such cells has been associated to an increase in CD4+ and CD8+ specific responses to the virus. In chronically infected HIV+ patients, increased proportions, but reduced absolute numbers of circulating Tregs were found, and Treg frequency was largely normalized by HAART [27]. Thus, in order to identify some crucial immunological events that occur during PHI, we analyzed specific response to viral antigens such as gag and nef, regulatory CD4+ T cells, and T cell activation in a group of patients who experienced a well documented PHI, and have been followed for more than 4 years. Our main finding is that T cell activation after PHI, more than T cell polyfunctionality or the presence of Tregs, could be considered as a predictive marker for the viral setpoint and time required to treatment.psoriasis; such pathologies were not considered related to HIV infection. All patients came to the medical observation and HIV testing because they realized to have had a risk because of unprotected sexual intercourses, that occurred few weeks before their first visit. At enrolment, median plasma viral load (VL) was 305,943 copies/mL, median CD4+ T cell count was 816 cells/mL). Viroimmunological parameters (standard CD4+ T cell count and quantification of VL) were performed in untreated patients up to 48 months from PHI (specifically at 12, 24, 36, 48 months) or up to the start of therapy. Chiron branched-DNA was used for plasma HIV RNA, and a value below 50 copies/mL was considered undetectable. Immunological analyses were performed in the first (M1), second (M2), third (M3), fourth (M4) and sixth (M6) month after infection. The different length of the observation period, during which no patients took antiretroviral therapy, was due to different time of enrollment; the longer period of observation in the survival analysis i.Infection [14]. Specific T helper cells are crucial for the anti-HIV immune response, since they provide help to B and CD8+ cells. A recent study in SIV-infected macaques has shown that depleting CD4+ during PHI worsen the infection [15]. HIV preferentially infects HIV-specific CD4+ lymphocytes [16]. The efficacy of a specific immune response is due to CD4+ and CD8+ T cell clones with multiple effectors functions, such as production of different cytokines and chemokines, activity of 1655472 costimulatory molecules, capacity to perform degranulation and to express cytotoxic molecules (e.g., perforin) [17,18]. These cells, defined “polyfunctional”, are present at relatively low frequency in HIV+ patients, but at high frequency in the blood of patients who control the virus, such as long term non progressors (LTNPs) or “elite controllers”, where the ?presence of HIV-specific polyfunctional CD8+ lymphocytes is associated with spontaneous control of viral replication [19,20,21,22]. Very few data exist on the polyfunctionality of T cells immediately after primary infection [23], and we were interesting in investigating this aspect in a longitudinal manner. Regulatory T cells (Tregs) have a crucial importance, being a viral reservoir, as shown by the presence of HIV-DNA in resting CD4+ Tregs from patients assuming HAART [24]. However, their role during the infection remains unclear. CD4+ Tregs might be important for the reduction of immune activation after PHI or even in chronic infection [25]. During chronic infection they could cause the deregulation of HIV-specific response [26], so favoring the progression of the infection, and a decrease of such cells has been associated to an increase in CD4+ and CD8+ specific responses to the virus. In chronically infected HIV+ patients, increased proportions, but reduced absolute numbers of circulating Tregs were found, and Treg frequency was largely normalized by HAART [27]. Thus, in order to identify some crucial immunological events that occur during PHI, we analyzed specific response to viral antigens such as gag and nef, regulatory CD4+ T cells, and T cell activation in a group of patients who experienced a well documented PHI, and have been followed for more than 4 years. Our main finding is that T cell activation after PHI, more than T cell polyfunctionality or the presence of Tregs, could be considered as a predictive marker for the viral setpoint and time required to treatment.psoriasis; such pathologies were not considered related to HIV infection. All patients came to the medical observation and HIV testing because they realized to have had a risk because of unprotected sexual intercourses, that occurred few weeks before their first visit. At enrolment, median plasma viral load (VL) was 305,943 copies/mL, median CD4+ T cell count was 816 cells/mL). Viroimmunological parameters (standard CD4+ T cell count and quantification of VL) were performed in untreated patients up to 48 months from PHI (specifically at 12, 24, 36, 48 months) or up to the start of therapy. Chiron branched-DNA was used for plasma HIV RNA, and a value below 50 copies/mL was considered undetectable. Immunological analyses were performed in the first (M1), second (M2), third (M3), fourth (M4) and sixth (M6) month after infection. The different length of the observation period, during which no patients took antiretroviral therapy, was due to different time of enrollment; the longer period of observation in the survival analysis i.