HIV virology and pathogenetic mechanisms of infection: a brief overview

Studies on HIV virology and pathogenesis address the complex mechanisms that result in the HIV infection of the cell and destruction of the immune system. These studies are focused on both the structure and the replication characteristics of HIV and on the interaction of the virus with the host. Continuous updating of knowledge on structure, variability and replication of HIV, as well as the characteristics of the host immune response, are essential to refine virological and immunological mechanisms associated with the viral infection and allow us to identify key molecules in the virus life cycle that can be important for the design of new diagnostic assays and specific antiviral drugs and vaccines. In this article we review the characteristics of molecular structure, replication and pathogenesis of HIV, with a particular focus on those aspects that are important for the design of diagnostic assays

The epidemic of HIV infection and AIDS, promotion of testing, and innovative strategies

In Europe, the incidence of new diagnoses of HIV infection in 2008 was 86.7 cases per one million population, and most cases were attributable to sexual transmission. In Italy, in 2007, the incidence was 60.0 cases per one million population (in the areas in which surveillance exists), and 73.7% of the cases were attributable to sexual transmission. At present, there are an estimated 170 000-180 000 persons living with HIV/AIDS in Italy, some of whom are unaware of being infected. Based on available epidemiological data and taking into consideration the level of risk of exposure to HIV, we describe several proposals for promoting access to HIV testing in diverse population groups and contexts, including some innovative approaches. The promotion of HIV testing is fundamental for public health and human rights and must be associated with treatment, care and prevention activities, which must be guaranteed for the entire population

Molecular characterization of HIV-1 subtype C gp-120 regions potentially involved in virus adaptive mechanisms

The role of variable regions of HIV-1 gp120 in immune escape of HIV has been investigated. However, there is scant information on how conserved gp120 regions contribute to virus escaping. Here we have studied how molecular sequence characteristics of conserved C3, C4 and V3 regions of clade C HIV-1 gp120 that are involved in HIV entry and are target of the immune response, are modulated during the disease course. We found an increase of "shifting" putative N-glycosylation sites (PNGSs) in the α2 helix (in C3) and in C4 and an increase of sites under positive selection pressure in the α2 helix during the chronic stage of disease. These sites are close to CD4 and to co-receptor binding sites. We also found a negative correlation between electric charges of C3 and V4 during the late stage of disease counteracted by a positive correlation of electric charges of α2 helix and V5 during the same stage. These data allow us to hypothesize possible mechanisms of virus escape involving constant and variable regions of gp120. In particular, new mutations, including new PNGSs occurring near the CD4 and CCR5 binding sites could potentially affect receptor binding affinity and shield the virus from the immune response. © 2014 Cenci et al

HIV-1 tat addresses dendritic cells to induce a predominant th1-type adaptive immune response that appears prevalent in the asymptomatic stage of infection

Tat is an early regulatory protein that plays a major role in human HIV-1 replication and AIDS pathogenesis, and therefore, it represents a key target for the host immune response. In natural infection, however, Abs against Tat are produced only by a small fraction (∼20%) of asymptomatic individuals and are rarely seen in progressors, suggesting that Tat may possess properties diverting the adaptive immunity from generating humoral responses. Here we show that a Th1-type T cell response against Tat is predominant over a Th2-type B cell response in natural HIV-1 infection. This is likely due to the capability of Tat to selectively target and very efficiently enter CD1a-expressing monocyte-derived dendritic cells (MDDC), which represent a primary target for the recognition and response to virus Ag. Upon cellular uptake, Tat induces MDDC maturation and Th1-associated cytokines and β-chemokines production and polarizes the immune response in vitro to the Th1 pattern through the transcriptional activation of TNF-αgene expression. This requires the full conservation of Tat transactivation activity since neither MDDC maturation nor TNF-α production are found with either an oxidized Tat, which does not enter MDDC, or with a Tat protein mutated in the cysteine-rich region (cys22 Tat), which enters MDDC as the wild-type Tat but is transactivation silent. Consistently with these data, inoculation of monkeys with the native wild-type Tat induced a predominant Th1 response, whereas cys22 Tat generated mostly Th2 responses, therefore providing evidence that Tat induces a predominant Th1 polarized adaptive immune response in the host. Copyright © 2009 by The American Association of Immunologists, Inc

Suggested strategies for the laboratory diagnosis of HIV infection in Italy

HIV/AIDS surveillance data indicate that, in 2008, approximately one-fourth of all HIV infections in adults remain undiagnosed in Italy and that close to 60% of Aids diagnosed individuals discovered their seropositivity at the diagnosis of AIDS. Late diagnosis of HIV infection is associated with increased mortality and morbidity and increased cost to healthcare services. From a public health perspective, knowledge of HIV status is associated with a reduction in risk behaviour. Thus, a routine screening for HIV infection is important for both a better prognostic outcome, and control of HIV spreading in the population. In Italy there are not shared guidelines for the laboratory diagnosis. In this paper, we suggest two algorithms that can be adopted for the diagnosis of HIV infection in individuals undergoing HIV testing

Communication and cultural interaction in health promotion strategies to migrant populations in Italy: the cross-cultural phone counselling experience

INTRODUCTION: In the last 10 years migration processes have progressively increased worldwide and in Italy about 5 millions of residing migrants are estimated. To meet health needs of these new residents, effective relational and communication tools, which allow a reciprocal intercultural interaction within health care structures, are therefore necessary. AIM: This article faces the main features of the relational-communication processes associated with health promotion and care in the migrant population in Italy to the aim of identifying the key and critical points within the interaction between different cultures, focusing on the role of specific professional figures, including cultural mediators and health educators. RESULTS: Within the activity of HIV phone counselling operated by Psyco-socio-behavioural, Communication and Training Operating Unit of National Institute of Health in Italy, an intercultural approach was successfully experienced in a project targeted to migrants (2007-2008). Specifically, the presence of cultural mediators answering in the languages of main migrants' groups allowed the increase of calls from migrant people and of the information provided

Sex workers clients in Italy: results of a phone survey on hiv risk behaviour and perception

Sex workers (SW) clients represent a bridge population for HIV transmission from high risk to low risk general population

Information needs of young Italians accessing the AIDS/STI Helpline at the Italian National Institute of Health

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Native HIV-1 Tat Protein Targets Monocyte-Derived Dendritic Cells and Enhances Their Maturation, Function, and Antigen-Specific T Cell Responses

Vaccination of cynomolgus monkeys with the biologically active HIV-1 Tat protein induces specific Th1 responses, including CTLs. Similar responses are also induced by vaccination with tat DNA, but not by vaccination with inactivated Tat or Tat peptides. This suggested that the native Tat protein may act differently on APC as compared with inactivated Tat or peptide Ag. In this study, we show that biologically active Tat is very efficiently taken up by monocyte-derived dendritic cells (MDDC) in a time (within minutes)- and dose-dependent (starting from 0.1 ng/ml) fashion, whereas uptake is very poor or absent with other APC, including T cell blasts and B lymphoblastoid cell lines. Although maturation of MDDC reduces their pino/phagocytic activity, mature MDDC take up Tat much more efficiently than immature cells. In addition, Tat uptake is abolished or greatly hampered by oxidation/inactivation of the protein or by performing the experiments at 4 degrees C, suggesting that MDDC take up native Tat by a receptor-mediated endocytosis. After uptake, active Tat protein induces up-regulation of MHC and costimulatory molecules and production of IL-12, TNF-alpha, and beta chemokines, which drive Th1-type immune response. In contrast, these effects are lost by oxidation and inactivation of the protein. Finally, native Tat enhances Ag presentation by MDDC, increasing Ag-specific T cell responses. These data indicate that native Tat selectively targets MDDC, is taken up by these cells via specialized pathways, and promotes their maturation and Ag-presenting functions, driving Th1-type immune responses. Thus, Tat can act as both Ag and adjuvant, capable of driving T cell-mediated immune responses