Protective immunity induced by an intranasal multivalent vaccine comprising 10 Lactococcus lactis strains expressing highly prevalent M‐protein antigens derived from Group A Streptococcus

Abstract

Streptococcus pyogenes (group A Streptococcus) causes diseases ranging from mild pharyngitis to severe invasive infections. The N-terminal fragment of streptococcal M protein elicits protective antibodies and is an attractive vaccine target. However, this N- terminal fragment is hypervariable: there are more than 200 different M types. In this study, an intranasal live bacterial vaccine comprising 10 strains of Lactococcus lactis, each expressing one N-terminal fragment of M protein, has been developed. Live bacterial-vectored vaccines cost less to manufacture because the processes involved are less complex than those required for production of protein subunit vaccines. Moreover, intranasal administration does not require syringes or specialized personnel. Evaluation of individual vaccine types (M1, M2, M3, M4, M6, M9, M12, M22, M28 and M77) showed that most of them protected mice against challenge with virulent S. pyogenes. All 10 strains combined in a 10-valent vaccine (M×10) induced serum and bronchoalveolar lavage IgG titers that ranged from three- to 10-fold those of unimmunized mice. After intranasal challenge with M28 streptococci, survival of M×10-immunized mice was significantly higher than that of unimmunized mice. In contrast, when mice were challenged with M75 streptococci, survival of M×10-immunized mice did not differ significantly from that of unimmunized mice. Mx-10 immunized mice had significantly less S. pyogenes in oropharyngeal washes and developed less severe disease symptoms after challenge than did unimmunized mice. Our L. lactis-based vaccine may provide an alternative solution to development of broadly protective group A streptococcal vaccines.

Clinical and microbiological response of mice to intranasal inoculation with Lactococcus lactis expressing Group A Streptococcus antigens, to be used as an anti‐streptococcal vaccine

“…One possible explanation is that the surface expression of M protein fragments masks recognition of WT surface antigens that otherwise activate the innate immune cascade. Interestingly, the greater reactogenicity of the L. lactis ‐WT strain could explain our previous findings of partial protection from infection observed in L. lactis ‐WT‐immunized mice , which may be attributable to them having stronger innate immune responses than in L. lactis ‐Mx10‐immunized mice.…”

“…All vaccine strains were constructed using the NICE genetic system (MoBiTech, Gottingen, Germany) according to previously published protocols . Briefly, portions of the N‐terminal domains of M proteins of 41 to 50 amino acids were PCR amplified from S. pyogenes of the 10 M types selected using primers with restriction enzyme sites.…”

“…We are developing an intranasal bacterial‐vectored vaccine based on 10 strains of Lactococcus lactis , each expressing a different M protein fragment from S. pyogenes . We have previously reported the immunogenicity and efficacy of an L. lactis strain expressing M9 antigen and, more recently, nine additional strains of L. lactis expressing nine different M protein fragments individually (M1, M2, M3, M4, M6, M12, M22, M28 and M77) and all of these fragments combined in a 10‐valent vaccine, named L. lactis ‐Mx10 . This vaccine elicits serum and mucosal specific antibodies against most M types included in the vaccine and protects against lethal challenge with virulent S. pyogenes M28 in mice.…”

Recent Scientific Advancements towards a Vaccine against Group A Streptococcus

“…Over the past decade, various peptide-based antigens selected from the pathogenic M protein achieved considerable progress in clinical trials in peptide-based subunit vaccines, with a summary of recent preclinical trials of peptide-based subunit vaccine candidates in Table 3 . A multivalent vaccine, containing 10 valents, from the hypervariable N-terminal regions of M protein by Wozniak et al [ 112 ]. Here, Wozniak and co-workers developed an intranasal live bacterial vaccine composed of 10 strains of Lactococcus lactis expressing one fragment of M protein, with the induction of high levels of serum and bronchoalveolar lavages IgG titres and low colonisation of bacteria strains on oropharyngeal [ 112 ].…”

Correlates of immunity to Group A Streptococcus: a pathway to vaccine development

“…This forms the basis of the classic "Lancefield" assay 18 , which measures the opsonophagocytic capacity of donor plasma antibodies as a marker of resistance to invasive infection. Subcutaneous [19][20][21] , intramuscular 22,23 and intranasal 24,25 vaccination with adjuvanted protein vaccines appear effective at preventing even lethal invasive infections in mouse models of infection. Furthermore, passive transfer of immunity using antisera and pooled human intravenous immunoglobulin (IVIg) have all successfully induced immunity in animal models, particularly when highly concentrated 13 .…”