Downregulation of MIP-1α/CCL3 with praziquantel treatment in Schistosoma haematobiumand HIV-1 co-infected individuals in a rural community in Zimbabwe

Human immunodeficiency virus (HIV)subtype 1, affects over 25 million persons in sub-Saharan Africa, with most living without access to antiretroviral treatment [1, 2]. An estimated 200 million persons are infected with schistosomes [3, 4]. The number of persons co-infected with these diseases is not known but in some areas the prevalence of co-infected persons is estimated to be high [5–9]. In humans, infection with the trematode parasites, S. mansoni and S. haematobium, is followed, after 4-6 weeks, by the deposition of eggs in the liver and other body organs, leading to immune activation [10]. The impact of schistosomiasis on the progression of HIV in co-infected persons has been contradictory, with reports from uncontrolled studies showing little or no effects of schistosomiasis treatment [5–9]. Infection with HIV induces immune activation with high levels of circulating cytokines, such as tumor necrosis factor-alpha (TNF-α) [11, 12], interleukin-6 (IL-6) [13, 14], IL-10 [13, 15, 16], and some chemokines [14, 15]. Activated CD4 cells express increased levels of the co-receptors CCR5 and CXCR4 speculated to enhance HIV entry and infect host cells [17], and MIP-1α/CCL3 enhances expression of these receptors that are also used by the virus. In vitro, the cytokines TNF-α and IL-6, as well as the chemokines IL-8 and MIP-1α/CCL3 can activate and assist the translocation of the transcription factor nuclear factor (NF)-κB in monocytes or macrophages [17]. In uninfected cells, this leads to cell proliferation and differentiation. However, the HIV provirus DNA carries multiple NF-κB binding sites; thus, the activation of NF-κB in HIV-infected cells results in viral nucleus material translocation into the host nucleus thereby undergoing replication [17]. Conversely, the anti-inflammatory cytokines IL-10 and TGF-β downregulate the pro-inflammatory cytokine TNF-α and MIP-1α/CCL3, thereby inhibits HIV replication in vitro in macrophages [17–19].

Schistosomiasis and some helminth infections are known to induce systemic inflammation associated with increased activation of CD4 cells and higher levels of CD8 cells [20], including surface receptor expression [21]. The initial acute schistosomiasis infection is characterized by production of T helper type 1 (Th1) cytokine that include interferon-γ and production of Th2 cytokines including IL-10 that would predominate in the subsequent early phases of the infection, attributed to play an important anti-inflammatory role [22–24]. There are few reports regarding levels of circulating cytokines during HIV and schistosomiasis co-infection, but Brown et al., (2005) reported that circulating IL-10 is reduced after treatment with praziquantel in co-infected persons and production of other cytokines during HIV-infection might also be affected by schistosomiasis co-infection [8, 25–28]. Greater concentrations of MIP-1α/CCL3/have been reported in S. mansoni infected individuals compared to uninfected individuals [8]. Plasma levels of MIP-1α/CCL3 have also been investigated and reported in several studies of S mansoni infected humans, murine models [24] and cell culture infections [27, 28], but none for S. haematobium. The aim of our study was to determine the plasma MIP-1α/CCL3 concentration in S. haematobium infected and uninfected humans at baseline and at three months after treatment with praziquantel and the influence of HIV-1 co-infection. We hypothesized that schistosomiasis would induce systemic inflammation indicated by the levels of circulating soluble MIP-1α/CCL3, a proinflammatory chemokine, and observed the effects of schistosomiasis treatment with praziquantel.

Schistosomiasis and HIV-1 co-infection has been observed from a couple of studies in Zimbabwe and elsewhere to have far reaching consequences, especially in likelihood of immunopathology and AIDS progression [5–9]. However, no clear attributive aspects have been linked or are known to worsen the condition during co-infection. Generally, in addition to cytokines, chemokines also play an important role in the regulation of immune responses and in controlling infectious diseases including HIV infection and progression. Cytokine and chemokines are chemotactic for specific types of cells and are involved in immunoregulation of cell mediated immunity. MIP-1α/CCL3 play an important role in recruiting macrophages, dendritic cells and T cells to site of infection and lymphoid organs, a task perceived to likely contribute to the dangers of schistosomiasis and HIV-1 co-infection. In this study we found that schistosomiasis infection being depicted by high egg output significantly upregulated the plasma levels of MIP-1α/CCL3 irrespective of HIV-1 infection status. Some studies have identified MIP-1α/CCL3 as a marker of disease severity in S. mansoni infected individuals [11, 25] and experimental studies in mice suggest that MIP-1α/CCL3 may be a causative factor in the development of severe schistosomiasis [24]. We investigated levels of MIP-1α/CCL3 in the plasma of HIV-1 and S. haematobium infected and uninfected individuals. These diseases are endemic in Zimbabwe where it is common to find individuals with HIV-1 and a parasitic co-infection.

From the observation on the co-infection data no differences in egg counts were found between HIV-1 positive participants and HIV-1 negative participants infected with S. haematobium. The findings were reported in detail by our group Kallestrup et al., (2005) [7]. However, briefly, the findings on the coinfection data on schistosomiasis egg counts reveal similarity between HIV-1 coinfected even after adjustments were made for differences in age and sex. These findings, led to speculation of an immunomodulatory inhibition of the human host's ability to excrete Schistosoma eggs when immunodeficient because of HIV-1 coinfection [35]. The findings indicated moderately to severely immunocompromised individuals whose interactions between HIV-1 and concurrent infections with S. haematobium indicated by higher egg counts cause inflammation during schistosomiasis. This finding is in agreement with other reports of an association between CD4 lymphocytopenia and helminthic and other infections [22, 36–40]. These differences in CD4 cell counts apparently disappear in S. mansoni infected HIV-1 positive participants, indicating that any possible subtle effect of schistosomiasis on CD4 cell counts seems to be masked by the dramatic HIV-1 related decline in CD4 cell counts [35]. Despite the difference between the intensities of the S. haematobium infections in the population in the study and the S. mansoni infection in other studies, it appears that HIV-1 induced immunodeficiency does not impair the ability of participants with low and high intensity schistosomiasis to excrete S. haematobium eggs. Our results as first reported in Kallestrup et al., (2005) [7], further question the applicability of murine studies that show a dependency of adequate CD4 cell immunity for S. mansoni development and fecundity to human conditions. One may assume that, in our cohort, some antischistosome immune responses were already established when HIV-1 was encountered [7, 22].

Schistosoma haematobium infected individuals had elevated levels of MIP-1α/CCL3 compared with egg negative individuals. This is in agreement with findings by other investigators on S. mansoni infection who demonstrated a positive correlation between elevated plasma concentrations of MIP-1α/CCL3, egg counts and presentation of severe schistosomiasis in humans [22–25]. Our results also showed that HIV-1 status had no influence on the levels of MIP-1α/CCL3 as individuals who were HIV-1 positive and S. haematobium positive had similar elevated levels as those who were HIV-1 negative and S. haematobium positive, suggesting that schistosomiasis infection is causing the elevation of MIP-1α/CCL3 levels. This is further confirmed by a comparison of MIP-1α/CCL3 levels in HIV-1 positive but S. haematobium negative compared to HIV-1 negative and S. haematobium negative, both groups showing low levels of MIP-1α/CCL3. Egg counts also had an influence on MIP-1α/CCL3 levels as shown by a comparison of the four groups which showed elevated levels in individuals with more than 10 eggs per 10 ml of urine compared to individuals with less than 10 eggs per 10 ml of urine. These findings indicated the existence of inflammatory environment during infection and egg laying by the schistosome worms. However, high egg output may be related to heavy worm burden subsequently related to increased inflammation by the high egg numbers released into the system.

We further determined the plasma concentration of MIP-1α/CCL3 at three months post treatment with the anti-schistosome drug, praziquantel. MIP-1α/CCL3 concentration in plasma was significantly reduced at three months post treatment, an indication that MIP-1α/CCL3 may be an inflammatory factor produced during S. haematobium infection and is downregulated when the infection is eliminated. Similar findings were reported in murine models [34]. It is assumed that eggs are the stimulant of this inflammatory response, and we may speculate that during inflammation, individuals co-infected with HIV-1 may be prone to immune activation and an increase in circulating viruses thereby increase chances of transmission. This calls for surveillance and control of schistosomiasis in population living in endemic areas, making praziquantel readily available for the control of schistosomiasis infection.

The findings from this study have shown that the MIP-1α/CCL3 chemokine levels were associated with S. haematobium egg counts at baseline before treatment, but not with HIV-1 infection status. MIP-1α/CCL3 levels were significantly reduced at three months post treatment with praziquantel. We therefore conclude that MIP-1α/CCL3 chemokine is produced during inflammation, caused by eggs during S haematobium infection, in which infection is associated with increased MIP-1α/CCL3 levels in an egg intensity-dependent manner. Praziquantel treatment of S. haematobium is associated with a reduction in levels of MIP-1α/CCL3.