1. MOLECULAR CHARACTERIZATION OF HAV ISOLATES IN ARGENTINA M. Munné 1, S. Vladimirsky 1, M. Cañero Velasco 2, L. Otegui 1, L. Brajterman 1 R. Castro 1, S. Soto 1 and J. González 1. 1 National Reference Lab. for Viral Hepatitis. INEI ANLIS. “Dr C. G. Malbrán”. 2 San Justo Children Hospital. Buenos Aires. Argentina. HAV is endemic in Argentina. OBJECTIVE To characterize HAV strains, circulating in Buenos Aires area and in the rest of the country. SUBJECTS & METHODS RNA extraction and RT-nested PCR with primers targeting the VP1-2A region were performed in antiHAV IgM positive serum samples from sporadic cases in Buenos Aires area and from outbreaks in different regions of the country from 1996 to 2002. (Fig 1)The number of isolates studied was 18. The nucleotide sequence analysis was done with phylogenia programs. RESULTS The 18 isolates are genotype IA (Fig 2). The samples from the same outbreak (2 from Gan Gan, Chubut province, January 2002 and 3 from Barreal, San Juan province, may 2002) are identical within them, but different between and to one from Maquinchao outbreak, Río Negro province, August 1997 and to all (12) sporadic cases. These last ones are 1 from the city of Buenos Aires, June 1999 and 11 from Buenos Aires province (1 from Bernal, May 2002 and 10 from San Justo, 8 recovered between December 1997 and September 1998, 1 in October 2001 and the last in May 2002). Among the isolates from San Justo, only one recovered in December 1997 and other in March 1998 are identical. The one isolated in May 2002 has the same sequence in this fragment as the one from the city of Buenos Aires June 1999. CONCLUSIONS All the isolates reported here were sub-genotype IA, so this is still the only one reported in Argentina to date. There were no differences between outbreak and sporadic involved strains and hence between high (BA area, SJ, Be) and low (Ga, Ba, Ma) population density areas, thus confirming the high endemicity of this infection. The high genetic diversity in this small fragment did not allow us to identify a pattern of circulation. This study will be very important as reference data in the characterization of the strain/s producing fulminant cases since this severe clinical presentation was not the case in any of the infections studied in this series. Barreal San Juan Barreal San Juan Fig 1:Geographic distribution of studied cases Fig 2:Phylogenetic tree of the VP1-2A region of HAV isolates 0.1 SFL CF53 AGM CY145 JM55 KPH H132 PA21 GA76 HM175 ARG6 GBM ARG23 ARG1 ARG4 VII II 87 100 IB IA VI IV V IIIB IIIA III I 74 1 dot = 100 hab/km 2 Gan Gan Chubut Maquinchao Río Negro Maquinchao Río Negro Buenos Aires area Buenos Aires area Strains reported in this work Arg 5.7 (San Justo, Jun 98) Arg 1.9 (San Justo, Mar 98) Arg 5.5 (San Justo, Apr 98) Arg 1.7 (San Justo, Dec 97) Arg 2. 22 & 2.19 (San Justo, May 02; Bs. As., Jun 99) Barreal, Arg 4.7 & 4.8 & 4.9 (Barreal, May 02) (3) Gan Gan, Arg 6.12 & 6.2 (Gan Gan, Jun 02) (2) Arg 5.4 (San Justo, Sep 1998) Bernal Arg 3.17 (Bernal, May 02) Arg 1.10 (San Justo, Mar 98) Maquinchao Arg 1.5 (Maquinchao, Aug 97) Arg 4.10 (San Justo, Oct 01) Arg 5.3 & 5.10 (San Justo, Mar 98/Dec 97) Oral presentation in “Epidemiologic and control of HAV”. Monday 7 April 2003 11-12.30 Hs. Harbourside Meeting Room 5