High diversity of group A Streptococcal emm types in an Indian community: the need to tailor multivalent vaccines.
BACKGROUND
Concern about the emergence of antibiotic-resistant strains and about morbidity and/or mortality related to rheumatic fever and rheumatic heart disease has been a continuous impetus for the development of a safe, effective vaccine against group A Streptococcus (GAS). To date, >120 GAS M types are known, as identified by serological typing. In general, serum immunoglobulin G directed to the hypervariable NH2 terminal portion of M protein leads to complement fixation and opsonophagocytosis of the homologous streptococcal serotype by polymorphonuclear leukocytes, and the protection is type specific. The sequence variation at the N terminus ultimately affects the binding of opsonic antibodies. Because of hypervariability in these opsonic sequences from different M types, it was relevant to use epitopes derived from these multiple sequences in a "multivalent vaccine" design for evaluation of protection against these M types of GAS. Thus, any attempts to design vaccines for a given community will require information on N terminal-sequence typing and variation.


METHODS
In the present study, we performed molecular characterization of isolates recovered from patients in northern India--to our knowledge, for the first time--in an attempt to study the circulating M types and their N terminal sequence variability.


RESULTS
We report tremendous diversity in GAS strains recovered from symptomatic patients, with implications on the design of appropriate vaccines. Fifty-nine isolates represented 33 different sequence types. Very few novel types and no predominant clones were found.


CONCLUSIONS
The high diversity of emm types encountered in a single year suggests that any M protein-based multivalent vaccine would have to be specifically tailored for this region.
Dey
Nilay
N
Department of Experimental Medicine and Biotechnology, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
McMillan
David J
DJ
Yarwood
Penny J
PJ
Joshi
R M
RM
Kumar
Rajesh
R
Good
Michael F
MF
Sriprakash
Kadaba S
KS
Vohra
Harpreet
H
D015373:Bacterial Typing Techniques; D001428:Bacterial Vaccines / Q000008:administration & dosage*; D005798:Genes, Bacterial; D014644:Genetic Variation; D006801:Humans; D007194:India; D044382:Population Groups; D013290:Streptococcal Infections / Q000517:prevention & control*; D013291:Streptococcus / Q000145:classification* / Q000235:genetics; D014614:Vaccines, Synthetic / Q000008:administration & dosage
D001428:Bacterial Vaccines; D014614:Vaccines, Synthetic