Sequence diversity of serine repeat antigen gene exon II of Plasmodium falciparum in worldwide collected wild isolates.

Field isolates of Plasmodium falciparum collected from endemic areas of Southeast Asia, Solomon Islands, tropical African countries and Brazil were analyzed for the genetic diversity of the exon II of serine repeat antigen gene (SERA) by sequencing of genomic DNA. Of sixty-nine isolates, as compared to the reported FCR3, K1 and Honduras-1 types of exon II sequences, 5, 9 and 20 new allelic forms were found in 23 isolates of the FCR3 type, 36 of the K1 type and 10 of the Honduras-1 type. A group of novel non-synonymous substitutions, 4 new insertions and 3 new deletions of octamer units were found in the octamer repeat region (OR) of the exon II, and most of them clustered within a 40-residues domain. An octamer "SNPVSSEP" revealed in the OR was confirmed as a new repeat unit. Based on the sequences of the serine repeat region (SR) of the exon II, the allelic forms of the Honduras-1 type were conjectured to be the recombinant forms between the K1 type and FCR3 type. The allelic forms of K1 type with less or more repeat serine residues in the serine stretch of the SR than the reported 21 serine residues had most of the variations in the OR. Moreover, a biased geographical distribution of allelic forms was observed. Isolates from African and Southeast Asian countries accounted for most of the new allelic forms (29/33). All of the three types were detected in Southeast Asia but none of the FCR3 type in Africa. One of two groups of FCR3 new allelic forms was found solely in Brazil while another was mainly in Solomon Islands.

Intratypic differentiation & partial nucleotide sequencing of poliovirus isolates of northern India.

The potential resolving power of molecular epidemiological studies has enhanced the precision and reliability of poliovirus (PV) surveillance. PV has an error prone RNA polymerase responsible for rapid evolution of genome (approximately 10(-2) nt substitution/site/year), during inter and intra-human passages. The present study included a serotyped panel of 60 PV (42 PV type-1, 13 PV type-2 and 5 PV type-3) isolated during 1997. They were differentiated into vaccine (Sabin) and wild strains by two methods viz., genotype specific RNA probe hybridization (Rpro-Hy) based on genotypic variability; and ELISA that uses cross-absorbed antiserum (Pab-E) based on phenotypic variability. For obtaining information on molecular epidemiology, partial nucleotide sequencing (VP1/2A region) of five clinical PV isolates was also done. Three of the 60 isolates (two PV type-1 and one PV type-3) intratyped, could not be differentiated correctly by either method. Genotypic characterization of PV isolates was done for confirmation of intratyping results. All five wild PV1 sequenced belonged to the same genotype (> 85% homology) and sequence divergence among the strains was < or = 4.5 per cent. This indicated circulation of a single genetic lineage in the area.

Enteric viral infections in pre-school children in Karachi, Pakistan.

A prospective study was conducted in Karachi, Pakistan on the virology of enteropathogens excreted by children with acute gastroenteritis and the results were compared with a control group of healthy children. Rotavirus and Adenovirus detection was done using ELISA techniques, while enterovirus isolation was done by virus culture. In 1990, 12.3% children with acute watery diarrhoea excreted rotavirus, as compared to 24.4% children in 1991. None of the healthy children excreted adenovirus 40 and 41. Preliminary results of 1992 revealed that rotavirus was seen in 13% of children with acute watery diarrhoea and adenovirus in 10% of children. Enteroviruses were isolated in the same frequency in all three groups i.e. children with acute watery diarrhoea, children with poliomyelitis and healthy children. Non-polio enteroviruses were excreted in 50-52% in all the 3 groups. The rate of enterovirus excretion is much higher than seen in other developed countries and is the same in children with diarrhoea and healthy children.

Hepatitis A, B and C seroprevalence in Pakistan.

A cross sectional study was conducted to determine the seroprevalence of Hepatitis A, B, and C virus in healthy Pakistani children. HAV IgG antibody was assayed in 258 subjects and it was found that 94% children by 5 years of age had HAV IgG-antibody. The overall seroprevalence of HAV IgG antibody was 55.8% and IgM 5.3%. HBVsAb levels assayed in 236 healthy children showed a seroprevalence of 2.97%. Similarly, HCV antibody seroprevalence was found to be a low 0.44% in healthy children. HAV is a major cause of Hepatitis, as compared to HBV and HCV which are of low endemicity.