Systemic and mucosal immune responses to sublingual or intramuscular human papilloma virus antigens in healthy female volunteers

The sublingual route has been proposed as a needle-free option to induce systemic and mucosal immune protection against viral infections. In a translational study of systemic and mucosal humoral immune responses to sublingual or systemically administered viral antigens, eighteen healthy female volunteers aged 19-31 years received three immunizations with a quadravalent Human Papilloma Virus vaccine at 0, 4 and 16 weeks as sublingual drops (SL, n = 12) or intramuscular injection (IM, n = 6). IM antigen delivery induced or boosted HPV-specific serum IgG and pseudovirus-neutralizing antibodies, HPV-specific cervical and vaginal IgG, and elicited circulating IgG and IgA antibody secreting cells. SL antigens induced ~38-fold lower serum and ~2-fold lower cervical/vaginal IgG than IM delivery, and induced or boosted serum virus neutralizing antibody in only 3/12 subjects. Neither route reproducibly induced HPV-specific mucosal IgA. Alternative delivery systems and adjuvants will be required to enhance and evaluate immune responses following sublingual immunization in humans.

TRIAL REGISTRATION

ClinicalTrials.govNCT00949572.

Safety and immunogenicity of SC599, an oral live attenuated Shigella dysenteriae type-1 vaccine in healthy volunteers: results of a Phase 2, randomized, double-blind placebo-controlled trial

SC599 vaccine is a live Shigella dysenteriae 1 strain attenuated by deletion of invasion [icsA], iron chelation [ent, fep] and shiga toxin A subunit [stxA] genes. In a preliminary Phase 1 single dose prospective study, we showed that SC599 vaccine was well tolerated, and the maximum tolerable dose was greater than 10(8) CFU [Sadorge C, Ndiaye A, Beveridge N, Frazer S, Giemza R, Jolly N, et al. Phase 1 clinical trial of live attenuated Shigella dysenteriae type-1 DeltaicsA Deltaent Deltafep DeltastxA:HgR oral vaccine SC599 in healthy human adult volunteers. Vaccine 2008; 26(7):978-8]. In this Phase 2 trial, three groups of volunteers ingested a single dose of SC599 [10(5) CFU, n=38; 10(7) CFU, n=36] or placebo [n=37]. Both 10(5) and 10(7) CFU doses were immunogenic, inducing significant IgA and IgG LPS-specific ASCs and antibody responses, comparable in magnitude to those of other strains that prevented illness following experimental challenge. In the intention to treat analysis, 34.2% and 44.4% IgA ASC responders were detected in the 10(5) and 10(7) CFU groups respectively (p<0001 vs placebo for both groups), as well as 31.6% and 33.3% serum IgA responders (p<001 and p<0.001 vs placebo for 10(5) and 10(7) CFU groups, respectively). No difference between the two vaccine groups was observed. No stxB-specific antibody response was detected in the vaccines. SC599 excretion occurred in 23.7 and 30.6% of subjects in the 10(5) and 10(7) CFU groups, respectively. SC599 vaccine was well tolerated, and the reported adverse events were mainly digestive. These results indicate that a single oral immunization of SC599 vaccine elicits a significant circulating IgA ASC and serum antibody response that may confer protection against the most severe symptoms of Shigellosis in responders to the vaccine.

Ability of SPI2 mutant of S. typhi to effectively induce antibody responses to the mucosal antigen enterotoxigenic E. coli heat labile toxin B subunit after oral delivery to humans

We have evaluated an oral vaccine based on an Salmonella enteric serovar typhi (S. typhi) Ty2 derivative TSB7 harboring deletion mutations in ssaV (SPI-2) and aroC together with a chromosomally integrated copy of eltB encoding the B subunit of enterotoxigenic Escherichia coli heat labile toxin (LT-B) in volunteers. Two oral doses of 10(8) or 10(9)CFU were administered to two groups of volunteers and both doses were well tolerated, with no vaccinemia, and only transient stool shedding. Immune responses to LT-B and S. typhi lipopolysaccharide were demonstrated in 67 and 97% of subjects, respectively, without evidence of anti-carrier immunity preventing boosting of LT-B responses in many cases. Further development of this salmonella-based (spi-VEC) system for oral delivery of heterologous antigens appears warranted.