Vaccination of domestic animals with a novel oral vaccine prevents Giardia infections, alleviates signs of giardiasis and reduces transmission to humans

• Published in: npj vaccines Vol. 1; no. 1; p. 16018
• Main Authors: Serradell, Marianela C, Saura, Alicia, Rupil, Lucia L, Gargantini, Pablo R, Faya, Marcela I, Furlan, Paulina J, Lujan, Hugo D
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15-09-2016; Nature Publishing Group
• Subjects: 631/250/590/2294; 692/699/255/1715; Biomedical and Life Sciences; Biomedicine; Disease control; Disease transmission; Drug resistance; Immune system; Infections; Infectious Diseases; Medical Microbiology; Parasites; Parasitic diseases; Pets; Proteins; Public Health; Vaccine; Vaccines; Virology; Argentina
• DOI: 10.1038/npjvaccines.2016.18
• EISSN: 2059-0105

Giardia lamblia
is a human intestinal parasite and one of the most frequent enteric pathogen of companion animals. Clinical manifestations of giardiasis, such as diarrhoea, anorexia, weight loss and lethargy, have been associated with
Giardia
infections in both domestic and farm animals. A few anti-parasitic drugs are routinely used to treat giardiasis, but re-infections are common and drug-resistant strains have already been reported. Unfortunately, efficient vaccines against
Giardia
are not available.
Giardia
undergoes antigenic variation; through this mechanism, parasites can avoid the host’s immune defenses, causing chronic infections and/or re-infections. Antigenic variation is characterised by a continuous switch in the expression of members of a homologous family of genes encoding surface antigens. In a previous report, we indicated that in
Giardia
, the mechanism responsible for the exchange of variant-specific surface proteins (VSPs) involves the RNA interference (RNAi) pathway. From a repertoire of ~200 VSP genes, only one is expressed on the surface of single trophozoites; however, RNAi machinery disruption generates trophozoites that express the complete VSP repertoire. We also demonstrated that gerbils orally immunised with VSPs isolated from these altered parasites showed high levels of protection. Here we tested this vaccine in cats and dogs, and found that it is highly efficient in preventing new infections and reducing chronic giardiasis in domestic animals both in experimental and natural infections. Remarkably, immunisation of dogs in a highly endemic area strongly decreased the percentage of infected children in the community, suggesting that this vaccine would block the zoonotic transmission of the disease.
Giardia: Preventing interspecies transfer and human infection
Scientists in Argentina have proposed a candidate for the first vaccine against Giardia infection. Giardia typically escapes vaccination by changing its surface proteins, masking it from detection by the immune system. Hugo Lujan and colleagues at Universidad Católica de Córdoba and Consejo Nacional de Investigaciones Cientificas y Tecnicas overcame this by inducing the parasite to express all of these proteins at the same time, allowing them to craft an oral vaccine against all variations of the infection. Lujan's team tested their vaccine in domestic animals and found that the vaccine both conferred protection against giardiasis and reduced infection in diseased animals. A community with immunized dogs saw a sharp decrease in infected children, highlighting the potential of the vaccine to stem transfer to humans. The researchers suggest this vaccine could be economically produced and endorse research into a human vaccine. Scientists in Argentina have proposed a candidate for the first vaccine against Giardia infection. Giardia typically escapes vaccination by changing its surface proteins, masking it from detection by the immune system. Hugo Lujan and colleagues at Universidad Católica de Córdoba and Consejo Nacional de Investigaciones Cientificas y Tecnicas overcame this by inducing the parasite to express all of these proteins at the same time, allowing them to craft an oral vaccine against all variations of the infection. Lujan's team tested their vaccine in domestic animals and found that the vaccine both conferred protection against giardiasis and reduced infection in diseased animals. A community with immunized dogs saw a sharp decrease in infected children, highlighting the potential of the vaccine to stem transfer to humans. The researchers suggest this vaccine could be economically produced and endorse research into a human vaccine.