Inclusion of a universal tetanus toxoid CD4+ T cell epitope P2 significantly enhanced the immunogenicity of recombinant rotavirus ΔVP8* subunit parenteral vaccines

Abstract

Currently available live oral rotavirus vaccines, Rotarix® and RotaTeq®, are highly efficacious in developed countries. However, the immunogenicity and efficacy of such vaccines in some developing countries are low. We reported previously that bacterially-expressed rotavirus ΔVP8* subunit vaccine candidates with P[8], P[4] or P[6] specificity elicited high-titer virus neutralizing antibodies in animals immunized intramuscularly. Of note was the finding that antibodies induced with the P[8]ΔVP8* vaccine neutralized both homotypic P[8] and heterotypic P[4] rotavirus strains to high titer. To further improve its vaccine potential, a tetanus toxoid universal CD4+ T cell epitope P2 was introduced into P[8] or P[6]ΔVP8* construct. The resulting recombinant fusion proteins expressed in Escherichia coli were of high solubility and were produced with high yield. Two doses (10 or 20μg/dose) of the P2-P[8]ΔVP8* vaccine or P2-P[6]ΔVP8* vaccine with aluminum phosphate adjuvant elicited significantly higher geometric mean homologous neutralizing antibody titers than the vaccines without P2 in intramuscularly immunized guinea pigs. Interestingly, high levels of neutralizing antibody responses induced in guinea pigs with 3 doses of the P2-P[8]ΔVP8* vaccine persisted for at least 6 months. Furthermore, in the gnotobiotic piglet challenge study, three intramuscular doses (50μg/dose) of the P2-P[8]ΔVP8* vaccine with aluminum phosphate adjuvant significantly delayed the onset of diarrhea and significantly reduced the duration of diarrhea and the cumulative diarrhea score after oral challenge with virulent human rotavirus Wa (G1P[8]) strain. The P2-P[8]ΔVP8* vaccine induced serum virus neutralizing antibody and VP4-specific IgG antibody production prechallenge, and primed the pigs for higher antibody and intestinal and systemic virus-specific IFN-γ producing CD4+ T cell responses postchallenge. These two subunit vaccines could be used at a minimum singly or preferably in bivalent formulation to provide antigenic coverage of most of the G types of global importance.

Contribution of Maternal Immunity to Decreased Rotavirus Vaccine Performance in Low- and Middle-Income Countries

“…Addressing this question through studies that withhold breastfeeding would require longer withholding periods that may not be feasible or ethical. To avoid interference of oral RV by breast milk, one potential option may be a shift to parenteral RV in LMIC (70)(71)(72)(73)(74)(75).…”

Tandem truncated rotavirus VP8* subunit protein with T cell epitope as non-replicating parenteral vaccine is highly immunogenic

“…18 In this study, we generated tandem rotavirus VP8* recombinant protein with the universal tetanus toxoid (TT) T cell epitope P2-P[8] DVP8*-P[8] DVP8* and P2-P[8] DVP8*-P [6] DVP8* in an attempt to further improve the immunogenicity of the recombinant subunit vaccine candidates. Our study demonstrated that both of the recombinant proteins induced high titers 5120 5120 1280 1280 5120 1280 1280 320 160 80 2 5120 1280 5120 2560 5120 1280 1280 320 320 160 3 5120 1280 1280 2560 5120 1280 1280 320 320 160 4 20480 20480 10240 20480 20480 5120 2560 640 320 80 5 20480 5120 5120 5120 10240 1280 5120 320 320 320 6 20480 2560 2560 2560 5120 1280 2560 320 320 160 7 20480 2560 5120 2560 5120 1280 2560 320 160 80 8 40960 5120 5120 5120 10240 2560 5120 320 320 160 GMT 13280 3620 3620 3620 7241 1660 2348 349 269 …”

“…The effect of structure constraint on antigen presentation was considered when we constructed the tandem rotavirus recombinant VP8 protein. A flexible linker "GSGSG" was introduced between T cell epitope P2 and truncated VP8*, as well as in the middle of the 2 truncated VP8*s (2 copies of truncated P [8] 18 Of interest, introduction of P[6] DVP8* to P2-P[8] DVP8* in pET expression system compromised the expression of soluble protein. In this study, we mainly focused on evaluation of the immunogenicity of tandem fusion proteins, rather than the production of target proteins.…”

“…12,13 In addition, formation of reassortant rotaviruses between vaccine strains and circulating wild-type strains or among vaccine strains can potentially increase virulence as reported recently. [14][15][16][17] PATH (Program for Appropriate Technology in Health, an international nonprofit organization) has launched a non-replicating rotavirus vaccine (NRRV) program (including the P2-P [8] DVP8* recombinant protein vaccine we reported previously) 18 aiming to develop next generation, nonoral rotavirus vaccines. Vaccines administered through non-oral routes may overcome factors that can weaken an oral vaccine's efficacy including co-infections in the digestive system or the presence of maternal antibodies, and remove the slight risk of intussusception associated with live-rotavirus vaccines entirely.…”

“…27,28 We reported previously that bacteriallyexpressed P2-P[8] DVP8* induced high levels of both homotypic and heterotypic neutralizing antibodies in guinea pigs and significantly delayed the onset and shortened the duration of diarrhea in gnotobiotic pigs vaccinated with purified P2-P[8] DVP8* after oral challenge with the virulent human rotavirus Wa strain. 18 The above mentioned phase I clinical trial launched by PATH demonstrated moderate immunogenicity of the P2-P[8] DVP8* (aa 65-223) vaccine in humans. 24 Therefore, we aimed to further increase the immunogenicity of such P2-P[8] DVP8* candidate vaccine.…”