Simian immunodeficiency virus, infection, alcohol, and host defense

Chronic Binge Alcohol Administration Increases Intestinal T-Cell Proliferation and Turnover in Rhesus Macaques

BACKGROUND

Alcohol use results in changes in intestinal epithelial cell turnover and microbial translocation, yet less is known about the consequences on intestinal lymphocytes in the gut. Here, we compared T-cell subsets in the intestine of macaques before and after 3 months of chronic alcohol administration to examine the effects of alcohol on intestinal T-cell subsets.

METHODS

Rhesus macaques received either alcohol or isocaloric sucrose as a control treatment daily over a 3-month period via indwelling gastric catheters. Intestinal lymphocyte subsets were identified in biopsy samples by flow cytometry. Twenty-four hours prior to sampling, animals were inoculated with bromo-deoxyuridine (BrdU) to assess lymphocyte proliferation. Immunohistochemistry was performed on tissue samples to quantitate CD3+ cells.

RESULTS

Animals receiving alcohol had increased rates of intestinal T-cell turnover of both CD4+ and CD8+ T cells as reflected by increased BrdU incorporation. However, absolute numbers of T cells were decreased in intestinal tissues as evidenced by immunohistochemistry for total CD3 expression per mm(2) intestinal lamina propria in tissue sections. Combining immunohistochemistry and flow cytometry data showed that the absolute numbers of CD8+ T cells were significantly decreased, whereas absolute numbers of total CD4+ T cells were minimally decreased.

CONCLUSIONS

Collectively, these data indicate that alcohol exposure to the small intestine results in marked loss of CD3+ T cells, accompanied by marked increases in CD4+ and CD8+ T-cell proliferation and turnover, which we speculate is an attempt to maintain stable numbers of T cells in tissues. This suggests that alcohol results in accelerated T-cell turnover in the gut, which may contribute to premature T-cell senescence. Further, these data indicate that chronic alcohol administration results in increased levels of HIV target cells (proliferating CD4+ T cells) that may support higher levels of HIV replication in intestinal tissues.

Drugs of abuse and HIV infection/replication: implications for mother-fetus transmission

Human immunodeficiency virus (HIV) infection and progression of acquired immunodeficiency syndrome (AIDS) can be modulated by a number of cofactors, including drugs of abuse. Opioids, cocaine, cannabinoids, methamphetamine (METH), alcohol, and other substances of abuse have been implicated as risk factors for HIV infection, as they all have the potential to compromise host immunity and facilitate viral replication. Although epidemiologic evidence regarding the impact of drugs of abuse on HIV disease progression is mixed, in vitro studies as well as studies using in vivo animal models have indicated that drugs of abuse have the ability to enhance HIV infection/replication. Drugs of abuse may also be a risk factor for perinatal transmission of HIV. Because high levels of viral load in maternal blood are associated with increased risk of HIV vertical transmission, it is likely that drugs of abuse play an important role in promoting mother-fetus transmission. Furthermore, because the neonatal immune system differs qualitatively from the adult system, it is possible that maternal exposure to drugs of abuse would exacerbate neonatal immunity defects, facilitating HIV infection of neonate immune cells and promoting HIV vertical transmission. The availability and use of antiretroviral therapy for women infected with HIV increase, there is an increasing interest in determining the impact of drug abuse on efficacy of AIDS Clinical Trials Group (ACTG)-standardized treatment regimens for woman infected with HIV in the context of HIV vertical transmission.

In vitro and in vivo models of acute alcohol exposure

Alcohol abuse is a global problem due to the financial burden on society and the healthcare system. While the harmful health effects of chronic alcohol abuse are well established, more recent data suggest that acute alcohol consumption also affects human wellbeing. Thus, there is a need for research models in order to fully understand the effect of acute alcohol abuse on different body systems and organs. The present manuscript summarizes the interdisciplinary advantages and disadvantages of currently available human and non-human models of acute alcohol abuse, and identifies their suitability for biomedical research.

Neuroimmunity, drugs of abuse, and neuroAIDS

It has long been postulated that drugs of abuse may represent significant cofactors in the progression of human immunodeficiency virus (HIV)-induced disease. Both HIV infection and drugs of abuse have significant effect on the immune system as well as on the nervous system. In HIV infection, abnormalities in these systems intersect to lead to a constellation of symptoms known as neuroAIDS. Drugs of abuse may synergize with such damage, acting on immune and/or neural cells. However, definitive epidemiological evidence for such an interaction is lacking. Here we review such studies as well as the use of the nonhuman primate/simian immunodeficiency virus system to investigate the interaction of neuroAIDS with drugs of abuse. Furthermore, recent findings on mechanisms of actions of selected drugs reveal the possibility of protective as well as detrimental effects on the central nervous system damage induced by HIV.

Advances in nonhuman primate alcohol abuse and alcoholism research

Advances in our understanding of the biological basis of alcohol abuse and alcoholism and the development of prevention and therapeutic intervention require appropriate animal models. Nonhuman primates are important to the study of complex biomedical disease processes. Genetic, anatomical, physiological, and behavioral similarities to humans offer unique opportunities for translational research along with the advantage of a degree of experimental control that is not possible in human studies. The purpose of this review is to outline the approaches taken with nonhuman primates as subjects in alcohol research and to highlight our current understanding of data on organismal variables that can be uniquely studied in these complex organisms. We review literature on alcohol self-administration to provide an integrative framework for discussion of progress in 2 important areas of research. Designs that incorporate self-administration provide a context for studying excessive alcohol consumption, including the organismal and environmental factors that influence risk for heavy drinking. We then review the use of monkeys to identify aspects of adverse biomedical consequences that follow excessive alcohol consumption. One of the primary conclusions to be drawn from this review is that nonhuman primates are a central part of the translational bridge in alcohol research, providing powerful and unique opportunities for experimental work that can address the biomedical complexities of alcohol abuse and alcoholism.

The effect of chronic binge ethanol consumption on the primary stage of SIV infection in rhesus macaques

BACKGROUND

Alcohol abuse and infection with HIV individually compromise immune function, but the consequence of both conditions together is poorly understood owing to the difficulties of performing appropriate studies in human subjects. Simian immunodeficiency virus (SIV) infection of rhesus macaques is considered to closely model HIV disease in that the virus infects CD4+ cells and this infection leads to a similar AIDS state. This study was initiated to study the combined effects of chronic binge alcohol consumption on the primary stage of SIV infection.

METHODS

Rhesus macaques were administered alcohol or isocaloric sucrose via a permanently indwelling intragastric catheter 4 consecutive days per week for the duration of the study. Doses were individualized to achieve plasma alcohol concentrations of 50-60 mM over a 5-hr period. After 3 months, animals were inoculated intravenously with 10,000 times the ID(50) (50% infective dose) of SIV(DeltaB670) at the conclusion of an alcohol session and followed for 2 months postinoculation.

RESULTS

At 1 week, plasma SIV RNA was greater than 60-fold higher in alcohol-consuming animals compared with sucrose controls. Likewise, alcohol consumption enhanced the SIV-induced increase in cell cycling T lymphocytes (i.e., cells expressing Ki67 protein) in blood. These differences between alcohol- and sucrose-treated animals were not sustained during the observation period. Peak viral load occurred 2 weeks post-SIV inoculation at 7.6 +/- 4.2 and 5.2 +/- 3.1 x 106 copies/ml in alcohol- versus sucrose-consuming animals, respectively. Blood CD4+ lymphocyte numbers were decreased 1 and 2 months after SIV inoculation to a similar degree in both sucrose-control and alcohol-treated animals.

CONCLUSIONS

The consequence of the early rise in viral load and increase in lymphocyte turnover seen with excess alcohol consumption is unknown. We hypothesize that alcohol intoxication may increase the susceptibility of the host to HIV/SIV infection. This possibility needs to be explored further.