The envelope of HIV

Complement analysis 2016: Clinical indications, laboratory diagnostics and quality control

In recent years, complement analysis of body fluids and biopsies, going far beyond C3 and C4, has significantly enhanced our understanding of the disease process. Such expanded complement analysis allows for a more precise differential diagnosis and for critical monitoring of complement-targeted therapy. These changes are a result of the growing understanding of the involvement of complement in a diverse set of disorders. To appreciate the importance of proper complement analysis, it is important to understand the role it plays in disease. Historically, it was the absence of complement as manifested in severe infection that was noted. Since then complement has been connected to a variety of inflammatory disorders, such as autoimmune diseases and hereditary angioedema. While the role of complement in the rejection of renal grafts has been known longer, the significant impact of complement. In certain nephropathies has now led to the reclassification of some rare kidney diseases and an increased role for complement analysis in diagnosis. Even more unexpected is that complement has also been implicated in neural, ophtalmological and dermatological disorders. With this level of involvement in some varied and impactful health issues proper complement testing is clearly important; however, analysis of the complement system varies widely among laboratories. Except for a few proteins, such as C3 and C4, there are neither well-characterized standard preparations nor calibrated assays available. This is especially true for the inter-laboratory variation of tests which assess classical, alternative, or lectin pathway function. In addition, there is a need for the standardization of the measurement of complement activation products that are so critical in determining whether clinically relevant complement activation has occurred in vivo. Finally, autoantibodies to complement proteins (e.g. anti-C1q), C3 and C4 convertases (C3 and C4 nephritic factor) or to regulatory proteins (e.g. anti-C1inhibitor, anti-factor H) are important in defining autoimmune processes and diseases based on complement dysregulation. To improve the quality of complement laboratory analysis a standardization commmittee of the International Complement Society (ICS) and the International Union of Immunological Societies (IUIS) was formed to provide guidelines for modern complement analysis and standards for the development of international testing programs.

Interference with complement regulatory molecules as a possible therapeutic strategy in HIV infection

Drugs which inhibit different stages of the HIV infection process, such as cell entry through CD4 and chemokine receptors, production of double stranded DNA from the HIV genome and maturation of newly produced viruses, are now proposed for AIDS therapy. None of these treatments, however, solve the problem of complete HIV eradication and the frequent appearance of mutants displaying drug resistance. We have recently detailed a strategy describing how HIV protects itself from the human complement and propose that interference of this resistance could be a possible target for therapy.

Cellular Compartments of Human Immunodeficiency Virus Type 1 Replication In Vivo: Determination by Presence of Virion-Associated Host Proteins and Impact of Opportunistic Infection

Antigens derived from host cells are detectable in the envelope of human immunodeficiency virus type 1 (HIV-1) and result in a distinctive viral phenotype reflecting that of the host cell. An immunomagnetic capture assay targeting discriminatory host proteins was developed to differentiate between HIV-1 derived from macrophages and lymphocytes. HIV-1 propagated in macrophages or lymphocytes in vitro was selectively captured by monoclonal antibodies directed against the virally incorporated cell-type-specific host markers CD36 (macrophages) and CD26 (lymphocytes). Furthermore, by targeting these markers, virus of defined cellular origin was selectively captured from a mixed pool of in vitro-propagated viruses. This technique was further refined in order to determine the impact of opportunistic infection on HIV-1 expression from these cellular compartments in vivo. Analysis of cell-free virus purified from plasma of patients with HIV-1 infection suggested that in those with an opportunistic infection, viral replication occurred in activated lymphocytes. Interestingly, there was also significant replication in activated macrophages in those patients with untreated pulmonary tuberculosis. Thus, in addition to lymphocytes, the macrophage cellular pool may serve as an important source of cell-free HIV-1 in patients with opportunistic infections that lead to marked macrophage activation. This novel viral capture technique may allow researchers to address a wide range of important questions regarding virus-host dynamics.

Human immunodeficiency virus type 1 derived from cocultures of immature dendritic cells with autologous T cells carries T-cell-specific molecules on its surface and is highly infectious

During the budding process, human immunodeficiency virus type 1 (HIV-1) acquires cell surface molecules; thus, the viral surface of HIV-1 reflects the antigenic pattern of the host cell. To determine the source of HIV-1 released from cocultures of dendritic cells (DC) with T cells, immature DC (imDC), mature DC (mDC), T cells, and their cocultures were infected with different HIV-1 isolates. The macrophage-tropic HIV-1 isolate Ba-L allowed viral replication in both imDC and mDC, whereas the T-cell-line-tropic primary isolate PI21 replicated in mDC only. By a virus capture assay, HIV-1 was shown to carry a T-cell- or DC-specific cell surface pattern after production by T cells or DC, respectively. Upon cocultivation of HIV-1-pulsed DC with T cells, HIV-1 exclusively displayed a typical T-cell pattern. Additionally, functional analysis revealed that HIV-1 released from imDC-T-cell cocultures was more infectious than HIV-1 derived from mDC-T-cell cocultures and from cultures of DC, T cells, or peripheral blood mononuclear cells alone. Therefore, we conclude that the interaction of HIV-1-pulsed imDC with T cells in vivo might generate highly infectious virus which primarily originates from T cells.