Naranbhai V, Altfeld M, Abdool Karim Q, Ndung’u T, Abdool Karim SS, Carr WH, Sentrum vir die VIGS Program van Raosing in Suid-Afrika (CAPRISA) Tenofovir gel Raosing vir VIGS Prevention Science (TRAPS) Span. Naranbhai V, Abdool Karim SS, Altfeld M, Samsunder N, Durgiah R, Sibeko S, Abdool Karim Q, Carr WH en die CAPRISA004 TRAPS-span. Naranbhai V, Altfeld A, Werner L, Abdool Karim Q, Abdool Karim S, Carr WH namens die TRAPS-span.
Valley-Omar Z, Anderson J, Arney L, Sibeko S, Naranbhai V, Swanstrom R, Abdool Karim Q, Abdool Karim SS, Williamson C. Multiple Variant HIV-1 Transmission: CAPRISA 004 TNV Microbicide Trial.
Thesis Framework
Using a variety of assays, NK cell function was analyzed before HIV acquisition and in women who did not acquire HIV. This chapter presents evidence that primed NK cell anti-HIV-1 responses are protective against HIV-1 acquisition and examines the implications of this finding for vaccine development. Chapter six presented evidence that non-specific innate immune activation precedes and is strongly associated with HIV-1 acquisition.
Chapter six summarizes findings that exclude microbial translocation and TLR responsiveness as major players in innate immune activation that precedes HIV-1 acquisition.
HIV-1
Recently, the increased risk of metabolic (Norbiato, 2012), cardiovascular (Hsue et al., 2012) and malignant diseases in patients with HIV-1 has been recognized and partially linked to aberrant immune activation (Hunt, 2012). HIV acquisition prevention or intervention studies have been designed based on a wide variety of known HIV risk factors (Padian et al., 2011). Survival of patients with HIV-1 on cART now approaches that of the normal population (van Sighem et al., 2010; Walensky et al., 2006).
Therefore, the primary approach to developing prophylactic interventions has been to attempt to enhance protective immune responses (McMichael et al., 2010).
Natural Killer cells and HIV-1 .1 Natural Killer cell function
Activation of KIR and HLA-C1 alleles has been associated with NK cell antiviral peptide-specific HIV-1 responses ( Tiemessen et al., 2011 ). Therefore, the effect of HIV-1 on NK cells has also been of considerable interest to the field (Fauci et al., 2005). Alter and colleagues (Alter et al., 2007b) described the changes in NK cell populations in 29 acutely infected individuals.
Some functions of NK cells are preserved through chronic infection, but whether their specific anti-HIV-1 activity is preserved is less clear (Fogli et al., 2008).
The role of immune activation in HIV-1 pathogenesis
A study of NK cells in patients with inflammatory bowel disease suggested that NK cells are not further activated in vitro by microbial products (Gregson et al., 2009). But because of the genetic and immunological basis of inflammatory bowel disease, these results are not generalizable to NK cells in individuals at risk or infected with HIV-1. As a key part of the innate immune response, the role that NK cells play in immune activation is important for studying activation in the context of HIV-1 acquisition.
Data are conflicting in this respect with some studies claiming that activation is protective and others suggesting so.
Tenofovir gel
Finally, delays in PBMC processing were associated with a reduced ability of NK cells to degranulate (as measured by CD107a expression) or secrete cytokines (IFN-γ and TNF-α). D shows the proportion of NK cells expressing CCR4 or CCR7 in WB 2 or 24 hours after venipuncture. In comparison, much greater changes occur in acute NK cell activation after vaccination (Horowitz et al., 2010).
CD57 defines a functionally distinct population of mature NK cells in the human CD56dimCD16+ NK cell subset. In vitro and animal studies suggest a possible role of NK cells in controlling viral replication during primary HIV-1 infection [6]. The proportion of activated T cells and NK cells was significantly correlated before (C) but not after HIV-1 infection (D).
There was no difference in the proportion of NK cells secreting IFN-c after ex vivo IL-2 stimulation alone (Figure 3B). During primary HIV-1 infection, the frequency of NK cells expressing homing markers to lymphoid tissues increases. In contrast, the proportion of NK cells expressing both integrin α4 and β7 subunits remained unchanged (Figure 4B).
In this study, NK cell and T cell activation were uncoupled from primary HIV-1 infection illustrating the differential effects of HIV on NK cells and T cells. After infection, a higher percentage of NK cells degranulated in the presence of IL alone -2 than before infection. We observed functional impairment of NK cells early after HIV acquisition in the absence of anergic NK cell expansion.
NK cells were defined (shown clockwise for A and B) after transition to singlets, lymphocytes, non-monocytes (CD14neg), non-B cells (CD20neg) or dead cells (Viability dieneg) and were CD3 negative but expressed CD7 ( as described) [18]). The proportion of NK cells expressing CCR7 decreased in the later stages of primary infection (B). Alter G, Altfeld M (2009) NK cells in HIV-1 infection: evidence for their role in the control of HIV-1 infection.
Study conclusions
Validation of multiparametric flow cytometry and cell preparation methods for quantification of NK cell activation, chemokine receptor expression and function. The NK cell studies reported here show that delayed treatment beyond eight hours introduces artifacts of increased activation, decreased expression of chemokine receptors, and decreased measures of NK cell cytolytic and secretory function. Therefore, for studies in which inference about in vivo NK cell function is desired, sample processing should occur at least eight hours after venipuncture.
Although NK IFN-γ cell responses to 721,221 cells were higher in non-acquirers than in acquirers, only the antiviral cytokine response to HIV-1-infected cells was associated with protection against acquisition. Therefore, these data suggest that specific NK cell IFN-γ responses may be protective against HIV-1. Current studies on the role of immune activation in HIV-1 acquisition differ in their conclusions.
In contrast, the results here show that women who later acquired HIV-1 had significantly higher ex vivo levels of innate immune activation, as measured by higher levels of pro-inflammatory cytokines including IL-2, IL-7, IL-12p70 and TNF -α, platelets, NK cell activation and constitutive CD8+ T cell degranulation. During primary HIV-1 infection, translocation of microbial products is thought to be a major cause of immune activation. Alternative contributors to immune activation may be changes in the microbiome and/or chronic intercurrent infections perhaps by herpes viridae, as HSV-2 infection was observed to alter NK cell function in this study and herpesviridae are known modulators of systemic immune responses.
Future studies are required to elucidate the causes of immune activation in women at risk for HIV. Women who acquired HIV-1 while using Tenofovir gel had similar NK cell and dendritic cell (DC) activation profiles but had relative preservation of gag-specific IFN-γ+ CD4+ T cell responses.
Limitations
Due to the small number of participants in this part of the study, no firm conclusions can be drawn, but these results suggest that tenofovir gel may modulate some adaptive immune parameters after infection in humans. The use of cryopreserved cells was unfortunately not addressed in these studies, and although widely practiced in clinical trials, use of cryopreserved samples may not extrapolate to in vivo events. More generally, the ex vivo measurements here are simply correlates of events in vivo, so they may include implicit biases.
Therefore, the risk of Type II errors—failure to reject a false null hypothesis—was substantial. Larger studies may have allowed the identification of NK cell-associated factors that have smaller effects on HIV-1 protection or control. Therefore, events that may have occurred during very early HIV-1 and that may be relevant to the course of the disease may have been missed.
Although the Tenofovir study included women similar to those at moderate to high risk of HIV in these settings, the findings may not be generalizable to settings other than clinical trials, women of different ages, and in different geographic areas. Although Tenofovir gel did not appear to confound the results, further studies are needed to determine whether the findings described here apply to at-risk groups in other settings. For example, it would be useful to assess this in the VOICE study (Marrazzo J., 2013) in which tenofovir gel was made available to the study participants, but adherence to the use of gel every day was low.
The main strength of this analysis is the study of clinically well-defined high-risk women at times before infection. A further strength is the wide variety of measures assessed and in particular the measurement of NK cell responses to autologous in vitro HIV-infected cells.
Implications for Future Research
Efficacy and safety of tenofovir gel, an antiretroviral microbicide, for the prevention of HIV infection in women. NK cells in HIV-1 infection: evidence for their role in the control of HIV-1 infection. Differential natural killer cell-mediated inhibition of HIV-1 replication based on different KIR/HLA subtypes.
Reduced CD4 T cell activation and in vitro susceptibility to HIV-1 infection in exposed, uninfected Central Africans. Heterosexual risk of HIV-1 infection by sex act: systematic review and meta-analysis of observational studies. Increased plasma lipopolysaccharide is not sufficient to stimulate natural killer cell activation in HIV-1 infected individuals.
A homozygous defect in the HIV-1 coreceptor is responsible for the resistance of some multiply exposed individuals to HIV-1 infection. Characterization of the defective interaction between a subset of natural killer cells and dendritic cells in HIV-1 infection. Frequent and strong antibody-mediated activation of natural killer cells in response to HIV-1 Env in individuals with chronic HIV-1 infection.
Human immunodeficiency virus type 1 (HIV-1) peptide-responsive natural killer cells are associated with control of HIV-1 infection. Increased plasmacytoid dendritic cell maturation and natural killer cell activation in HIV-1-exposed, uninfected intravenous drug users.
