MOLECULAR CHARACTERIZATION AND SEQUENCE PHYLOGENETIC ANALYSIS OF SURFACE ANTIGEN 3 (SAG3) GENE OF LOCAL INDIAN ISOLATES (CHENNAI AND IZATNAGAR) OF Toxoplasma gondii

Isolation and characterization of Toxoplasma gondii from small ruminants (sheep and goats) in Chennai City, South India

The present study aimed for the isolation and genotyping of Toxoplasma gondii from small ruminants (sheep and goats). 14 out of 193 tissue samples (either brain and heart) tested positive by MDAT for anti-T. gondii antibodies, were selected and bioassayed, which resulted 4 samples positive for T. gondii after 40 days of post inoculation. Four samples consisting of 3 numbers of sheep and 1 number of goat tissues out of 14 samples detected by B1 PCR, were genotyped at SAG3 locus by nested polymerase chain reaction-restriction fragment length polymorphism technique (nPCR-RFLP). The results of the present study revealed that the four isolates designated as TgShIn19, TgShIn76, TgShIn77 and TgGtIn27 were circulating in small ruminants, were belonged to genotypes of type II (TgShIn19) and type III (TgShIn76, TgShIn77 and TgGtIn27) which are in concordance with the previously reported genotypes from other animal species and further this presumptive results indicating that the genotype II and III could be the predominant in different animal species including birds and humans in India.

Genetic characterization of Toxoplasma gondii from autopsy proven cases of AIDS associated cerebral toxoplasmosis in South India

Toxoplasma gondii (T.gondii) infection can be devastating in the immunodeficient causing high morbidity and mortality. Due to limited availability of both diagnostic facilities and Highly Active Antiretroviral Therapy (HAART), toxoplasmosis continues to be a significant problem amongst Acquired Immuno Deficiency Syndrome (AIDS) patients in India. While scanty literature is available on T. gondii isolates in animals in India, little is known about the genetic diversity of the parasite in humans. Therefore, the present study investigated the genetic diversity of T. gondii in 25 confirmed cases of cerebral toxoplasmosis developing on the background of human immunodeficiency virus (HIV) infection/AIDS. PCR DNA sequencing was performed at four important genetic loci of T. gondii: BTUB, GRA6, alternative SAG2 (alt SAG2) and SAG3 on DNA from tissues obtained at postmortem. The amplified products from all the cases were successfully sequenced except at one locus for one case. Results of the present study suggest that majority of the patients (22/25; 88%) in South India are infected with strains that are recombinants of type II/III and/or strains representing T. gondii different from the archetypal lineages I, II, and III. In addition, clonal types III, MAS, and MAS variant genotypes were encountered. No clonal type I or II was seen in the present study. In addition, variants were observed at alt SAG2 and SAG3 but BTUB and GRA6 were highly conserved. Single nucleotide polymorphisms were observed mainly at two loci which are coding for surface antigens at alt SAG2 and SAG3. In conclusion, the present study reveals genetic diversity in India amongst strains of T. gondii from clinical cases of toxoplasmosis which is in accordance with other recent studies showing a high rate of genetic diversity in this parasite across the globe. There is a need to genotype T. gondii from different forms of toxoplasmosis in humans in India.