To the Editor: Ksiazek et al. (May 15 issue)1 report that thereis antibody cross-reactivity between serum from a patient withsevere acute respiratory distress syndrome (SARS) and antibodiesthat are reactive with group I coronaviruses. This finding raisesthe possibility of using existing vaccines against these heterologouscoronaviruses for protection against SARS. Unfortunately, thestudy did not show any virus-neutralization activity. Nevertheless,the close similarity between the SARS open reading frame 1band other human and animal coronaviruses lends support to theidea of using heterologous coronaviral strains, which are harmlessto humans, as vaccines. There are several historical examplesof successful heterologous vaccination, such as cowpox virusfor smallpox in humans and bacille Calmette–Guérinderived from mycobacterium in cattle for tuberculosis in humans.Furthermore, it has been shown that pathogens cause diseasesprimarily through their ability to evade immune control andthrough mimicry of host proteins.2 "Fuzzy" antigenic recognitionmight enable T-cell clones to recognize a spectrum of antigens,even antigens that are not closely similar to one another. Thus,the use of altered heterologous antigens, which are structurallydifferent from self-antigens, may improve immunity against theorthologous pathogens.3
Qibin Leng, Ph.D. Weizmann Institute of Science Rehovot 76100, Israel qibin_leng{at}yahoo.com
Zvi Bentwich, M.D. Rosetta Genomics Rehovot 76701, Israel
References
Ksiazek TG, Erdman D, Goldsmith CS, et al. A novel coronavirus associated with severe acute respiratory syndrome. N Engl J Med 2003;348:1953-1966. [Free Full Text]
Kotwal GJ. Poxviral mimicry of complement and chemokine system components: what's the end game? Immunol Today 2000;21:242-248. [CrossRef][Medline]
Leng Q, Bentwich Z. Beyond self and nonself: fuzzy recognition of the immune system. Scand J Immunol 2002;56:224-232. [Medline]
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