I approached these studies with an unbiased mind, searching for both solid and faulty logic, and for strength and weakness in experimental design. I urge you to do the same as you follow me through this further analysis of the AIDS-alkyl nitrite hypotheses. First on the list is the hypothesis that alkyl nitrites suppress the immune system, thereby either encouraging the development of AIDS in HIV-positive individuals or increasing the likelihood that an individual will become infected with the AIDS virus in the first place.
How does the data either support or refute this hypothesis? The first thing that struck me in researching the numerous studies on this topic was that while some immune suppression was found, numerous factors have confounded these findings to the point where they cannot be considered scientifically valid. On first glance, a large number of studies seem to support the immune suppression hypothesis, but further study of the experimental design used in these studies, as well as other shortcomings reveal these claims are on very shaky ground. I began my analysis by looking more closely at a problem found in most of the studies I came across, that of proper dosing.
Not surprisingly, most of these studies are experiments where either mice or cells were exposed to varying concentrations of alkyl nitrites, through various means of delivery. The first question that popped into my mind was how relevant are these experiments to real life? While helpful information is sometimes gained from these types of studies, more often, the findings cannot be transferred to human beings. Many new drugs are studied outside of the human context and, while the lab reports show they are a promising means of treatment, the drug fails to act the same way in human patients (Voeller 1986). Contrasting these experiments to the MACS Project and other studies where humans were studied, I found it impossible to compare the two. The next question that came to mind was how did the researchers adjust for the fact that they are using mice or cells, which differ from human subjects in many ways? Perhaps the most obvious difference is one of scale. Mice and cells are much smaller than human beings. How were doses adjusted to account for this size difference? Most frequently, I discovered, they weren’t.
Let’s look at a study completed by a group of researchers at M.D. Hospital in Houston, Texas (Hersh et al. 1983). The researchers investigated the effects of butyl nitrite (a type of alkyl nitrite) on laboratory cultures of white blood cells. So far, so good. We know the limitations of such an experiment, but let’s continue and look at the dosing regime. Hersh and colleagues reported that when exposed to a 1% concentration of butyl nitrite for 24 hours, many of these cells were killed, while at 0.5%, the cell number and viability were unaffected. What do these findings mean for an average human being? To establish a 1% concentration of butyl nitrite in an average human with six liters of blood even from a brief moment (we are not considering the 24 hour time period here yet), 60 mL of butyl nitrite needs to be added to the blood. A bottle of poppers contains 10 to 12 mL of the compound. This means that five or six bottles of the compound would have to be injected into a human to replicate the conditions of the experiment. Since nitrites are inhaled rather than injected (injecting nitrites is toxic) and only a small fraction of the compound is actually absorbed by the lungs, this study tells us nothing in reality except that a 1% concentration of butyl nitrite kills cells in a test tube. (Voeller 1986)
Numerous experiments conducted on mice also fail to adjust the doses for differences in lung size or body weight. Adjusting dose for body weight is a fundamental aspect of studies using experimental animals. When non-physiological doses (higher or lower than the comparable human dose) are used in animal studies, the results cannot be meaningfully compared to humans. Interestingly, many of the studies I reviewed administered doses that were at near lethal levels, so that it’s also unclear if the observed effect was due to toxicity (Lotzova et al. 1984; Gaworski et al. 1992; Soderberg et al. 1996a; Soderberg and Barnett 1996; Soderberg 1998; Tran et al. 2003). Imagine administering a near lethal dose of any compound, such as aspirin. Would the research findings tell us anything about the behavior of the compound at the normally consumed dose? I’m afraid not. Although it is clear that such data in no way test the hypothesis that alkyl nitrites impair the human immune system, I was completely taken aback to see how many advocates cite numerous studies of similar design to support the AIDS-poppers hypothesis.
In addition to dosing problems, many of the experiments that advocates reference in support of the AIDS-poppers hypothesis report changes in immune function only after administering the compound for an extended duration that simply does not reflect human use. For instance, in the 1983 study by Hersh et al. mentioned earlier, the cells in the experiment were exposed to butyl nitrite continuously for 24-72 hours. I was surprised that this and other studies (Gaworski et al. 1992; Tran et al. 2003) did not administer the compound for a briefer duration to better mimic human inhalation of the compound. Interestingly, I did come across one study that exposed mice to 300 ppm of alkyl nitrites for 6.5 hours a day for five days over 18 weeks, a level and duration that better reflects human use (Lewis 1985). No changes in immune function were observed.
In review, what did these experimental findings say about the effect of alkyl nitrites on immune function? In general, most of the findings stated that immune impairment occurred, but the doses were administered in a manner that rendered the findings invalid. This of course is a matter of scientific opinion. Suppose you don’t agree that the experimental designs were flawed? If so, I have a last point that may interest and surprise you. Many of the studies that saw immune impairment at near toxic doses of alkyl nitrites also reported that these effects were entirely reversible within days of stopping the dose (Soderberg and Barnett 1993; Dax et al. 1991; Soderberg et al. 1996b). Another interesting point to consider is that when immune cell function was compromised, the data often revealed that other cell types experienced cytotoxic effects, showing that nitrites did not act selectively against immune cells, but were harmful to other cell lines as well, suggesting that lethal doses of the compound were administered (Hersh et al. 1983). Additionally, published results were often contradictory. For instance, in 1996 Soderberg and Barnett (Soderberg et al. 1996a) repeated experiments that they had previously published in 1995 (Soderberg and Barnett 1995). The results of these experiments were opposite to those obtained when the same steps were followed previously. In science it’s important to repeat experiments to either support or invalidate a hypothesis. In this case, inconsistent findings help us see that the original hypothesis was invalid.
