Schistosoma mansoni soluble egg antigens enhance Listeria monocytogenes vector HIV-1 vaccine induction of cytotoxic T cells

Schistosomiasis Chemotherapy, Chemoprevention, and Vaccines: History, Progress, and Priorities

BACKGROUND

Schistosomiasis is a major human disease of public health importance. Freshwater snails serving as intermediary hosts and human interaction with surface water tainted by feces or urine are both necessary components of the transmission cycle. Schistosoma haematobium, Schistosoma mansoni, and Schistosoma japonicum are the primary pathogen species. Over 250 million individuals are infected globally, according to the World Health Organization, causing significant morbidity and an estimated loss of 1.9 million disability-adjusted life years, a number that is probably underestimated. Immunological protection is slowly built up through complex immunological systems, although innate factors also play a role. Chronic schistosomiasis affects mainly individuals residing in poor rural area. Vaccination is considered as one of the most sustainable options for the control of any pathogen, but schistosomiasis vaccine for humans or animals is not available till now despite the discovery of numerous potentially promising schistosome vaccine antigens.

OBJECTIVE

To provide an overview of the schistosomiasis chemotherapy, chemoprevention, and vaccines history and progress.

DESIGN

Review article.

DATA SOURCES

PubMed, ISI Web of Science, Science Direct, and the World Health Organization database.

CONCLUSION

Favorably praziquantel (PZQ) is a medication with excellent chemopreventive treatment compliance. Due to the extensive usage of PZQ, there is a great deal of debate surrounding the emergence of drug resistance. PZQ is effective against all species of schistosomes, schistosomiasis prevalence has remained largely unaffected, due to reinfection in high transmission areas and growing juvenile worms that were not affected by the drug, even though the need for a schistosomiasis vaccine is even more pressing.

An investigation into the role of chronic Schistosoma mansoni infection on Human Papillomavirus (HPV) vaccine induced protective responses

Background

Schistosoma mansoni is one of the most common helminth infections affecting a large population of people in sub-Saharan Africa. This helminth infection is known to cause immunomodulation which has affected the efficacy of a number of vaccines. This study examined whether a chronic schistosoma infection has an effect on the immunogenicity of HPV vaccine which is currently administered to girls and women aged 9 to 24. Little is known about the immune responses of the HPV vaccine in individuals with chronic schistosomiasis.

Methods

This study was carried out at the Institute of Primate Research (IPR) and involved an Olive baboon model. The experimental animals were randomly placed into three groups (n = 3–4); Two groups were infected with S. mansoni cercaria, and allowed to reach chronic stage (week 12 onwards), at week 13 and 14 post-infection, one group was treated with 80mg/kg of praziquantel (PZQ). Sixty four weeks post schistosoma infection, all groups received 2 doses of the Cervarix HPV vaccine a month apart. Specific immune responses to the HPV and parasite specific antigens were evaluated.

Results

Animals with chronic S. mansoni infection elicited significantly reduced levels of HPV specific IgG antibodies 8 weeks after vaccination compared the PZQ treated and uninfected groups. There was no significant difference in cellular proliferation nor IL-4 and IFN-γ production in all groups.

Conclusion

Chronic S. mansoni infection results in reduction of protective HPV specific IgG antibodies in a Nonhuman Primate model, suggesting a compromised effect of the vaccine. Treatment of schistosomiasis infection with PZQ prior to HPV vaccination, however, reversed this effect supporting anti-helminthic treatment before vaccination.

In sub-Saharan Africa countries, vaccines are administered to people who may suffer from existing infections, especially helminth infections. These infections are known to modulate immune responses rendering some vaccines ineffective. The impact of helminth infections such as schistosomiasis on a recently introduced Human Papillomavirus (HPV) vaccine on infected or treated populations and the degree or duration has not been clearly elucidated. This study was set up to investigate whether a chronic schistosoma infection compromises the specific immune responses elicited by the HPV vaccine.

Mucin-Type O-Glycosylation in Invertebrates

O-Glycosylation is one of the most important posttranslational modifications of proteins. It takes part in protein conformation, protein sorting, developmental processes and the modulation of enzymatic activities. In vertebrates, the basics of the biosynthetic pathway of O-glycans are already well understood. However, the regulation of the processes and the molecular aspects of defects, especially in correlation with cancer or developmental abnormalities, are still under investigation. The knowledge of the correlating invertebrate systems and evolutionary aspects of these highly conserved biosynthetic events may help improve the understanding of the regulatory factors of this pathway. Invertebrates display a broad spectrum of glycosylation varieties, providing an enormous potential for glycan modifications which may be used for the design of new pharmaceutically active substances. Here, overviews of the present knowledge of invertebrate mucin-type O-glycan structures and the currently identified enzymes responsible for the biosynthesis of these oligosaccharides are presented, and the few data dealing with functional aspects of O-glycans are summarised.

Schistosoma mansoni soluble egg antigens enhance T cell responses to a newly identified HIV-1 Gag H-2b epitope

Schistosome infection induces significant T helper type 2 (Th2) and anti-inflammatory immune responses and has been shown to negatively impact vaccine efficacy. Our goal was to determine if the administration of schistosome soluble egg antigens (SEA) would negatively influence the induction of cytotoxic T lymphocyte (CTL) and Th1-type T cell responses to an HIV candidate vaccine in the Th1-biased C57BL/6 mouse strain. Initial experiments failed, as we were unable to detect any response to the defined class I epitope for HIV-1 IIIB Gag. Therefore, we initiated an epitope mapping study to identify C57BL/6 (H-2(b)) T cell epitopes in HIV-1 IIIB Gag in order to perform the experiments. This analysis defined two previously unreported minimal class I H-2(b) and class II I-A(b) epitopes for HIV-1 IIIB Gag. The newly defined HIV-1 IIIB Gag epitopes were used to evaluate the influence of SEA on the generation of CTL and Th1-type HIV-1 IIIB Gag responses. Surprisingly, in contrast to our hypothesis, we observed that the coadministration of SEA with a Listeria monocytogenes vector expressing HIV-1 IIIB Gag (Lm-Gag) led to a significantly increased frequency of gamma interferon (IFN-γ)-producing CD8(+) and CD4(+) T cells in C57BL/6 mice compared to mice immunized with Lm-Gag only. These observations suggest that SEA contains, in addition to Th2-type and immune-suppressive molecules, substances that can act with the Lm-Gag vaccine to increase CTL and Th1-type vaccine-specific immune responses.