The present invention relates to a variant of cyclic GMP-AMP synthase (cGAS) carrying an amino acid substitution at one or more of (i) asparagine at amino acid position 513, (ii) asparagine at amino acid position 514, (iii) aspartic acid at amino acid position 465, (iv) glutamic acid at amino acid position 509, (v) tyrosine at amino acid position 510, (vi) arginine at amino acid position 512, (vii) lysine at amino acid position 427, and (viii) lysine at amino acid position 428. The present invention also relates to a variant of SplA/Ryanodine Receptor Domain And SOCS Box Containing 3 (SPSB3) carrying an amino acid substitution at one or more of (i) arginine at amino acid position 213, (ii) tyrosine at amino acid position 197, (iii) threonine at amino acid position 162, (iv) threonine at amino acid position 259, (v) arginine at amino acid position 262, (vi) serine at amino acid position 132, (vii) tyrosine at amino acid position 131, and (viii) tyrosine at amino acid position 160.