We investigated the association between certain clinical parameters and AF-ALB levels among HIV-positive and -negative individuals. Almost all (99.4%) of the HIV-positive and all (100%) of the HIV-negative populations were positive for AF-ALB in blood. This is in agreement with a previous report of AF-ALB levels in the Ashanti Region of Ghana (Jolly et al. 2006
). The results suggest that in regions of aflatoxin exposure HIV-positive people are more likely to have higher levels of AF-ALB in their blood compared with HIV-negative individuals. This observation may be connected to the impaired liver function that has been demonstrated in HIV-positive individuals (Feczko 1994
). It is possible that HIV-positive individuals have a decreased ability to detoxify aflatoxin metabolites. Studies in bovine hepatocytes show that AFB1
biotransformation which results in hydroxylated and demethylated metabolites as well as AFB1
epoxides involves the cytochrome P450 enzyme system (Kuilman et al. 2000
). In human hepatic cells it is thought that the cytochrome P450 isoenzymes CYPIA and CYP3A contribute to the formation of these metabolites (Kuilman et al. 2000
). The high AF-ALB results are consistent with the outcome of liver injury, i.e., increased CYPs (phase I metabolism) and decreased GSTs (phase II metabolism). AF-ALB is the product of phase I metabolism mediated by CYPs. We believe that HIV-induced inflammation and liver injury may stimulate CYPs for AFB metabolic activation (phase I metabolism) and decrease GSTs, which further accumulate AFB-epoxide and an increased AF-ALB level in the blood. On the other hand, both HIV-induced malnutrition and liver injury can decrease overall albumin (made in liver) concentration, which serves as denominator for the AF-ALB assay. Even at the similar AFB dietary exposure, it is reasonable that HIV patients had higher level of AF-ALB than non-HIV patients. However, it is also possible that aflatoxin is responsible for the liver disease since aflatoxins induce injury to both hepatic parenchyma and the biliary tract (Becker 2004
). Antiretrovirals (ARVs) could also play a major role in liver toxicity in HIV-positive patients on treatment (Sulkowski et al. 2000
; Aceti et al. 2002
; Bonacini et al. 2002
) with resulting aflatoxin build up in their blood. Thirty per cent of the study participants were on ARVs.
It was not surprising to find that the HIV-positive participants had significantly higher levels of total protein, higher total and indirect bilirubin, higher ALT and AST levels and lower serum albumin levels than the HIV-negative participants (). Several antiretrovirals have been shown to be associated with elevations in liver enzymes (Bonacini et al. 2002
). Indeed serum aminotransferases ALT and AST have been identified as useful markers of liver cell injury (Wu et al. 2004
). Lower plasma albumin levels indicate that the synthesis function of the liver is compromised in these HIV-positive participants. Bilirubin is a specific signal of hepatic injury and elevated serum bilirubin was found in up to 5% of HIV patients treated with HAART (Bonacini 2004
). Previously, Tao et al. (2005)
reported a close association between AF-ALB levels and direct bilirubin levels in non-HIV infected minors, a close association of AF-ALB with albumin and other liver function tests in HIV infected minors (less than 18 years) and a close association between AF-ALB and indirect bilirubin in non-HIV-infected adults. Other authors have reported increase in plasma/serum bilirubin as a result of aflatoxin treatment in rats (Rastogi et al. 2000
) and rabbits (Raval et al. 1993
; Guerre et al. 1997
). In the latter study increase in conjugated (direct) bilirubin was comparatively higher than increase in unconjugated (indirect) bilirubin. Higher total bilirubin levels indicate liver cell damage or bile duct damage within the liver while elevated direct or conjugated bilirubin indicate decreased bilirubin secretion from the liver or bile duct obstruction. It is likely that aflatoxin may contribute to the suboptimal liver function test results we obtained, since aflatoxins have also been shown to be independently associated with impaired liver function and hepatocellular carcinoma (Coulter et al. 1986
; CDC 2004
; Strosnider et al. 2006
). The findings of significantly higher levels of direct bilirubin in association with high AF-ALB by logistic regression and of significantly higher levels of total and direct bilirubin by linear regression indicate that bilirubin levels are elevated with high aflatoxin exposure and that bilirubin may prove to be a useful indicator of high AF-ALB in HIV-positive people in aflatoxin prone areas. Also, the linear regression results showed an association between lower levels of albumin and high AF-ALB levels indicating that aflatoxin also compromises the synthesis function of the liver in HIV-positive people.
The most interesting finding was that of significantly higher viral load levels (almost three-fold) among HIV-positive participants with high AF-ALB levels compared with those with low AF-ALB levels by multivariate analysis. AFB1
has been reported to cause significant (five-fold) increase in the chloramphenicol acetyltransferase (CAT) reporter gene linked to the promoter sequences in the long terminal repeat (LTR) of HIV-1 (Yao et al. 1994
). This increase in the rate of proviral transcription is determined by interaction between cellular transcription factors and their cognate sequences in the LTR. The mechanism by which AFB1
increased HIV-1 transcription has not been reported. TCDD (2,3,7,8-tetrachlorodibenzo-p
-dioxin) has been shown to increase infectious HIV-1 titres in experimental systems (Pokrovsky et al. 1991
; Tsyrlov and Pokrovsky 1993
was more potent in increasing CAT activity than TCDD. Although the study is cross-sectional, this finding that HIV-positive participants with higher AF-ALB levels also have higher viral load is significant given that aflatoxins have previously been shown to be associated with immune suppression in numerous animal studies (Pier 1986
; Pestka and Bondy 1994
; Gabal and Azzam 1998
; Marin et al. 2002
), in Gambian children (Turner et al. 2003
), and HIV-negative and positive Ghanaians (Jiang et al. 2005
). Perhaps aflatoxins and HIV may act synergistically to suppress immunity and consequently lead to higher viral loads.
It is also possible that aflatoxins by their effect on the liver and in suppressing the immune system contribute to other subtle differences in the presentation of HIV/AIDS in sub-Saharan Africa and other regions of the developing world compared with developed countries where aflatoxin contamination of food crops is not as rampant. Given the significance of these findings, research is urgently needed which would employ more rigorous study designs to shed more light on the possible role of aflatoxins on liver disease and viral load in HIV-positive people. This finding of increased viral load in association with high AF-ALB levels is poignant given that with the advent of HAART, HIV is now largely a chronic disease. If aflatoxins truly act in synergy with HIV and HAART to damage liver function, the taking of HAART would only be a part measure towards a holistic management of HIV/AIDS disease. A comprehensive approach would require a multidisciplinary strategy towards managing HIV patients that involves ways to reduce their exposure to aflatoxins in meals. This would imply educating affected communities on adopting better pre-harvest and crop storage methods, providing an enterosorbent such as NovaSil (Wang et al. 2008
) or drugs such as oltipraz (Wang et al. 1999
) which have been demonstrated to reduce serum AF-ALB, and implementing policy changes that would improve agricultural methods and enforcement of known allowable limits for aflatoxins in food meant for human consumption.
The study has several potential limitations. The most apparent is its cross-sectional nature which prevents establishment of ‘cause and effect’ relationships. Therefore, the study is invariably a preliminary report of associations and should only be interpreted as such. The findings should lead the way for the use of more vigorous study designs to test the observed associations. Since HIV-positive individuals have a myriad of clinical conditions which have similar or overlapping pathophysiological pathways, it is difficult to extricate if observed associations are as a result of HIV infection per se, HIV treatment, or a result of other accompanying or opportunistic infections. Thirdly, since we measured only AF-ALB, due cognizance must be taken of the fact that there are other mycotoxins such as fumonisins which occur in food (Kpodo et al. 2000
) that may have similar actions. The practical implications of the findings relate to the possible role aflatoxins may play in the progression of liver disease and HIV/AIDS and how aflatoxins may impact outcome of HIV treatment and management in areas where exposure to the toxin especially in food is ubiquitous.