Absence of cross-reactivity between Schistosoma mansoni infection and human immunodeficiency virus (HIV)

Effects of schistosomes on host anti-viral immune response and the acquisition, virulence, and prevention of viral infections: A systematic review

Although a growing number of studies suggest interactions between Schistosoma parasites and viral infections, the effects of schistosome infections on the host response to viruses have not been evaluated comprehensively. In this systematic review, we investigated how schistosomes impact incidence, virulence, and prevention of viral infections in humans and animals. We also evaluated immune effects of schistosomes in those coinfected with viruses. We screened 4,730 studies and included 103. Schistosomes may increase susceptibility to some viruses, including HIV and Kaposi’s sarcoma-associated herpesvirus, and virulence of hepatitis B and C viruses. In contrast, schistosome infection may be protective in chronic HIV, Human T-cell Lymphotropic Virus-Type 1, and respiratory viruses, though further research is needed. Schistosome infections were consistently reported to impair immune responses to hepatitis B and possibly measles vaccines. Understanding the interplay between schistosomes and viruses has ramifications for anti-viral vaccination strategies and global control of viral infections.

Many studies have described the effects of parasitic Schistosoma worm infections on the way that humans and animals respond to a variety of viral infections. Our goal was to evaluate, in a systematic manner, how having a schistosome parasitic infection affects a host’s susceptibility to viral infections, the clinical disease course of viral infections, and prevention of viral infections by vaccines. We also assessed the effects of schistosome infection on the host immune response to viruses. We screened 4,730 studies for potential relevance and included 103 of them in this review. Overall, our analysis showed that schistosome infection impairs the host response to many viruses. This includes increasing host susceptibility to HIV and possibly Kaposi’s sarcoma-associated herpesvirus, worsening the severity of clinical disease in hepatitis B and C infections, and decreasing immune responses to vaccines for hepatitis B and possibly measles. The studies that we analyzed also suggested that schistosome infection may protect the host against poor clinical outcomes from some viral infections including Human T-cell Lymphotropic Virus-Type 1, respiratory viruses, and chronic HIV. We discuss how these findings might be interpreted, and the additional research needed, in order to improve anti-viral vaccination strategies and control of viral infections globally.

Molecular characterization of two Schistosoma mansoni proteins sharing common motifs with the vif protein of HIV-1

We have previously described a rat mAb directed against a peptide derived from the vif protein of HIV-1 that recognized two Schistosoma mansoni (Sm) antigens with a major band at 65 kDa. Epitope mapping of this mAb using overlapping hexapeptides derived from the vif peptide revealed that the motif recognized was PLPSVT. The screening of a Sm cDNA library led to the identification of two clones, Sm70 and Sm65. The two deduced protein sequences did not share any common structural features apart from the epitope recognized by the mAb (see below), and did not show significant identity to sequences present in the data bases. However, the N terminus of the deduced sequence of the Sm70 protein exhibits a consensus sequence known to be an ATP/GTP binding site. Furthermore, the C terminus of the deduced Sm65 protein sequence was found to contain a conserved hexapeptide with a consensus sequence LPETGE reported to be an important motif of the surface proteins of gram-positive cocci. Both proteins exhibit a peptide sequence (PLRSVT for Sm70 and PVGSVT for Sm65) similar to the epitope recognized by the mAb anti-vif. Western blotting experiments showed that the mAb anti-vif reacted with both proteins. However, only Sm65 was recognized by sera from HIV-1-seropositive individuals, whereas both proteins were recognized by S. mansoni-infected patients.

Naphthalene black staining of granules of eosinophilic granulocytes: proposed mechanism of action using chemical blockade and computer graphics

Histochemical staining of the granules of eosinophilic granulocytes and subsequent blockade of the reaction by alkaline benzyl was strongly suggestive that in its purified form, the diazo dye naphthalene black reacts with tissue sites containing high concentrations of arginine residues. Computer graphics modelling indicated that the sulfonate group of the dye reacts electrostatically with the guanidino functional group of arginine. This acid-base type reaction likely has a stoichiometric ratio of 2:1 in favor of the amino acid.

Immunological crossreactivity between the human immunodeficiency virus type 1 virion infectivity factor and a 170-kD surface antigen of Schistosoma mansoni

A monoclonal antibody (mAb) directed against a synthetic peptide derived from the sequence of the human immunodeficiency virus type 1 (HIV-1) regulatory protein virion infectivity factor (vif) labeled the surface of Schistosoma mansoni schistosomula by indirect immunofluorescence. Western blotting showed that two S. mansoni proteins of 170 and 65 kD were recognized by the mAb. Sera from 20% of S. mansoni-infected HIV-seronegative individuals tested recognized the PS4 peptide in an ELISA as did sera from S. mansoni-infected rats. Sera from individuals seropositive for HIV-1, but without schistosomiasis, that reacted with the vif peptide also recognized a 170-kD S. mansoni protein. This crossreactive S. mansoni antigen appears to be a target of immunity in vivo since passive transfer of the mAb VIF-CD3 to naive rats had a protective effect against a challenge infection with S. mansoni cercariae.