Beaty, and L. in their study. As is evident from Table 2 in the original study (2), two cases of dengue shock syndrome were diagnosed as acute dengue virus infections based upon the dengue virus IgG antibody only. In areas where dengue is endemic, it appears to be difficult even among infants to exclude the presence of either passively transferred maternal IgG antibodies or IgG antibodies acquired due to past exposure in the form of clinical or subclinical infection. The first problem would be easily (S)-3,4-Dihydroxybutyric acid eliminated by determining the absence of dengue virus IgG antibodies in the maternal serum. Otherwise, the role of dengue virus IgG antibody in the diagnosis of acute infection lies with either the demonstration of seroconversion or a significant rise in antibody titers in follow-up samples (1). Since Kabilan et al. reported that the epidemic was due to dengue virus serotype 4, we would like to clarify that cross-reactions between flaviviruses as well as between dengue virus serotypes have been observed. (S)-3,4-Dihydroxybutyric acid It is difficult to type dengue viruses serologically by using the cross-reactive antigens that are available in many microELISA kits; i.e., the Pan-Bio dengue IgM kit utilizes dengue virus serotype 2 as the coating antigen, which cross-reacts with other dengue virus serotypes (serotypes 1, 3, and 4), whereas the Pan-Bio -capture IgM microELISA kit (S)-3,4-Dihydroxybutyric acid utilizes a pool of dengue virus serotypes 1 to 4 as the source of common dengue virus antigen. None of the kits mentioned above have the ability to differentiate between the serotypes unless serotype-specific antigenic determinants of dengue viruses are used individually in separate kits. At best, this type of kit can be used (S)-3,4-Dihydroxybutyric acid only for diagnosing acute dengue virus infection, not for serotyping. Conventionally, serotyping is done by neutralization, immunofluorescence tests using type-specific antisera (1), or reverse transcriptase PCR using type-specific primers (3). Hence, it would be worthwhile to know the type of antigens the authors used to determine the infection to be caused by dengue virus serotype 4. This information would be of much use to the researchers working in similar fields. REFERENCES 1. Calisher, C. H., B. J. Beaty, and L. J. Chandler. 1999. Arboviruses, p. 305-332. E. H. Lennette and T. F. Smith (ed.), Laboratory diagnosis of viral infections. Marcel Dekker Inc., New York, N.Y. 2. Kabilan, L., S. Balasubramanian, S. M. Keshava, V. Thenmozhi, G. Sekar, JAKL S. C. Tewari, N. Arunachalam, R. Rajendran, and K. Satyanarayana. 2003. Dengue disease spectrum among infants in the 2001 dengue epidemic in Chennai, Tamil Nadu, India. J. Clin. Microbiol. 41:3919-3921. [PMC free article] [PubMed] [Google Scholar] 3. Morita, K., M. Tanaka, and A. Igarashi. 1991. Rapid identification of dengue virus serotypes by using polymerase chain reaction. J. Clin. Microbiol. 29:2107-2110. [PMC free article] [PubMed] [Google Scholar] 4. Ratho, R. K., and S. R. Prasad. 1998. A serological study of flaviviral infections in Chandigarh. Indian J. Virol. 14:143-146. [Google Scholar] 5. Ratho, R. K., S. Sethi, and S. R. Prasad. 1999. Prevalence of Japanese encephalitis and West Nile viral infections in pig population in and around Chandigarh. J. Commun. Dis. 31:113-116. [PubMed] [Google Scholar] J Clin Microbiol. 2004 May; 42(5): 2357C2358. ? Author’s Reply 2004 May; 42(5): 2357C2358. doi:?10.1128/JCM.42.5.2357-2358.2004 Author’s ReplyLalitha Kabilan* Author information Copyright and License information Disclaimer CRME, 4, Sarojini St. Chinna Chokikulam Madurai-2, India *E-mail: moc.yfis@emrcid Copyright notice It is a great pleasure for me to respond to Dr. Mishra’s letter and to clarify the following points. First, in our study we used the -capture technique for serological confirmation. Second, what we said in the paper was that while dengue virus-specific IgM responses were predominant in most (23 of 24) dengue fever (DF) cases, the five infants with severe forms of dengue disease elicited IgG responses with or without IgM responses (Table 2 of reference 1), suggesting that the DF and dengue hemorrhagic fever-dengue shock syndrome cases were due to primary and secondary dengue virus infections, respectively. The cases were categorized by clinical and serological criteria. We fully agree with Dr. Mishra’s point of view as to the role of dengue virus-specific IgG antibody in the diagnosis of acute infection, which depends.