Increased spontaneous immunoglobulin secretion associated with cyclophosphamide-induced immune suppression

The Role of Microbial Translocation and Immune Activation in AIDS-Associated Non-Hodgkin Lymphoma Pathogenesis: What Have We Learned?

Human immunodeficiency virus (HIV) infection is associated with greatly increased risk for development of non-Hodgkin lymphoma (NHL). Nearly all acquired immunodeficiency syndrome (AIDS)-associated NHL (AIDS-NHL) is of B-cell origin. Two major mechanisms are believed to contribute to the genesis of AIDS-NHL: (1) loss of immunoregulation of Epstein-Barr virus (EBV)+ B cells, resulting from impaired T-cell function late in the course of HIV disease and (2) chronic B-cell activation, leading to DNA-modifying events that contribute to oncogene mutations/ translocations. HIV infection has long been known to be associated with chronic inflammation and polyclonal B-cell activation, and more recently, microbial translocation. Microbial translocation is bacterial product leakage from gut lumen into the peripheral circulation, resulting in high levels of lipopolysaccharide (LPS) in the peripheral circulation, leading to chronic immune activation and inflammation. We review recent literature linking microbial translocation to lymphom-agenesis. This includes epidemiological studies of biomarkers of microbial translocation with risk of AIDS-NHL and emerging data on the mechanisms by which microbial translocation may lead to AIDS-NHL development.

Serological Assessment of 18 Pathogens and Risk of AIDS-Associated Non-Hodgkin Lymphoma

BACKGROUND

HIV infection is associated with increased susceptibility to common pathogens, which may trigger chronic antigenic stimulation and hyperactivation of B cells, events known to precede the development of AIDS-associated non-Hodgkin lymphoma (AIDS-NHL).

METHODS

To explore whether cumulative exposure to infectious agents contributes to AIDS-NHL risk, we tested sera from 199 AIDS-NHL patients (pre-NHL, average lead time 3.9 years) and 199 matched HIV-infected controls from the Multicenter AIDS Cohort Study, for anti-IgG responses to 18 pathogens using multiplex serology. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using conditional logistic regression models.

RESULTS

We found no association between cumulative exposure to infectious agents and AIDS-NHL risk (OR 1.01, 95% CI: 0.91 to 1.12). However, seropositivity for trichodysplasia spinulosa polyomavirus (TSPyV), defined as presence of antibodies to TSPyV capsid protein VP1, was significantly associated with a 1.6-fold increase in AIDS-NHL risk (OR 1.62, 95% CI: 1.02 to 2.57). High Epstein-Barr virus (EBV) anti-VCA p18 antibody levels closer to the time of AIDS-NHL diagnosis (<4 years) were associated with a 2.6-fold increase in AIDS-NHL risk (OR 2.59, 95% CI: 1.17 to 5.74). In addition, high EBV anti-EBNA-1 and anti-ZEBRA antibody levels were associated with 2.1-fold (OR 0.47, 95% CI: 0.26 to 0.85) and 1.6-fold (OR 0.57, 95% CI: 0.35 to 0.93) decreased risk of AIDS-NHL, respectively.

CONCLUSIONS

Our results do not support the hypothesis that cumulative exposure to infectious agents contributes to AIDS-NHL development. However, the observed associations with respect to TSPyV seropositivity and EBV antigen antibody levels offer additional insights into the pathogenesis of AIDS-NHL.

Intrathecal IgG synthesis: a resistant and valuable target for future multiple sclerosis treatments

Intrathecal IgG synthesis is a key biological feature of multiple sclerosis (MS). When acquired early, it persists over time. A growing body of evidence suggests that intrathecal Ig-secreting cells may be pathogenic either by a direct action of toxic IgG or by locally secreting bystander toxic products. Intrathecal IgG synthesis depends on the presence of CNS lymphoid organs, which are strongly linked at anatomical level to cortical subpial lesions and at clinical level to the impairment slope in progressive MS. As a consequence, targeting CNS lymphoid lesions could be a valuable new target in MS, especially during the progressive phase. As intrathecal IgGs are end-products of these lymphoid lesions, intrathecal IgG synthesis may be considered as a specific marker of the persistence of these inflammatory lesions. Here we review the effect upon intrathecal IgG synthesis of all drugs ever used in MS. Except for steroids, all these therapeutic strategies, including rituximab, failed to decrease intrathecal IgG synthesis, with the exception of a questionable incomplete action of natalizumab. Thus, IgG synthesis is a robust marker of persistent intrathecal inflammation and its complete normalization should be one of the goals in future therapeutic strategies.

Examination of host immune resistance against Listeria monocytogenes infection in cyclophosphamide-treated mice after dietary lipid administration

BACKGROUND & AIMS

Despite the beneficial effects in the resolution of inflammatory disorders due to their immunosuppressive properties, n-3 polyunsaturated fatty acids are associated with a reduction of immune resistance to some microorganisms. Here, we examine the influence of different dietary lipids on host immune resistance against Listeria monocytogenes in mice treated with cyclophosphamide (CPA).

METHODS

Balb/c mice were fed one of four diets, which contained either olive oil (OO), fish oil (FO), hydrogenated coconut oil (HCO) or low fat (LF) for 4 weeks. Subsequently, mice were treated with CPA or PBS, prior to L. monocytogenes infection. Splenocyte proliferation, survival analysis, counts of viable bacteria from spleens and livers, and measurement of pro-inflammatory cytokine levels were determined.

RESULTS

The FO-rich diet reduced survival, particularly in CPA-treated mice. CPA was responsible for a significant increase of viable bacteria recovery from spleens and livers within each group fed high fat diets, which was aggravated in mice fed an FO diet. In addition, a significant increase of both TNF-alpha and IL-12p70 levels was detected in this group. These results may acquire a crucial relevance in clinical nutrition, particularly when FO diets are administered to immunocompromised patients.

CONCLUSIONS

The mechanism(s) that impair(s) the elimination of L. monocytogenes could be associated with a low mitogen-stimulated splenocyte proliferation, and with an alteration of pro-inflammatory cytokine production. The application of the neutropenic agent CPA moderately aggravates the immunosuppressive state mainly in FO-fed animals.

Preferential reductions in lymphocyte sub-populations induced by monthly pulses of chlorambucil: studies in patients with chronic progressive multiple sclerosis

Thirty-three patients with chronic progressive multiple sclerosis (MS) were assigned to intervention groups receiving monthly pulses of chlorambucil (CB) for about one year. The monthly doses ranged from 0.4 to 1.5 mg/kg. Administration of CB resulted in preferential reduction in different lymphocyte subsets which was dose- and time-dependent. The number of B-cells (CD20) decreased more rapidly than NK-cells (CD16, CD56, CD16+CD56+) or T-cell (CD3) and T-cells subsets (CD4 and CD8). At 1.2 mg/kg, CB administration resulted in a preferential drop of T-suppressor/cytotoxic cells (CD8) compared with T-helper cells (CD4), and of the less mature "virgin" CD4 cells (CD4+CD45RA+) compared with "memory" CD4 cells (CD4+CD45RA-). The expression of activation markers (transferrin receptor, CALLa, HLA-Dr and CD38[OKT10]) within CD4, CD8 or CD20 lymphocytes was not altered by CB administration. Our data, which show that CB administration results in a preferential fall in B-cell numbers, contrast with the effects of long-term administration of the related immunosuppressive drugs, azathioprine and cyclophosphamide.