Serological study of the lymphochoriomeningitis virus (LCMV) in an inner city of Argentina.

Lymphocytic choriomeningitis virus (LCMV) is the prototype of the family Arenaviridae and is associated with the natural reservoir, Mus domesticus (Md). It causes meningitis and a flu-like illness characterized by malaise, myalgia, retrorbital headache, and photophobia. This study presents the data obtained in a rodent and human serological study during 6 years (1998-2003) in the city of Rio Cuarto, Argentina. Antibodies anti-LCMV were sought by ELISA in rodents and humans. LCMV was found only in Md species in 9.4% of animals. The results also show some seasonal, no significant variations in the prevalence of the infection. Distribution of positive mice was not modified significantly by trapping sites, sex, or age of the animals. The prevalence of LCMV positive urban residents was found to be consistently low (1-3.6%) along the study period, with overage prevalence of 3.3% and values in males (4.6%) significantly higher than in females (2.6%) (P < 0.05). Seven of 432 pregnant women were found to be LCMV positive, but the absence of LCMV antibodies in the newborns demonstrated that the mothers were infected before pregnancy. This study is the first evidence on endemic LCMV in an Argentine city located outside the endemic area of Argentine hemorrhagic fever (AHF) and described the need to study other areas and increase awareness of this viral infection.

IgG subclasses in human immune response to wild and attenuated (vaccine) Junin virus infection.

Different proportions of IgG subclasses have previously been reported to distinguish the immune response elicited by primary and recurrent viral infections, as well as viral vaccines. The goal of this study was to study the IgG subclasses composition in the immune response of patients with Argentine hemorrhagic fever, and vaccinees with Candid #1 strain of Junin virus. Twenty-four individuals inoculated with Candid #1 vaccine and 67 patients with Argentine hemorrhagic fever were studied. Blood samples were drawn at 30, 60, and/or 180 days post-inoculation with Candid #1 and 30, 60, and 90 days after clinical onset of the disease. Specific anti-Junin virus IgG subclasses were titrated with specific human monoclonal antibody fluorescence isothiocyanate conjugate (FITC) by immunofluorescent assay (IFA). IgG(1) anti-Junin virus was found in every subject studied and IgG(3) was also detected in some patients with a severe form of Argentine hemorrhagic fever. IgG(2) and IgG(4) were not detected in any serum sample studied. The mean titer of specific IgG(1) in vaccinees was significantly lower than in patients with Argentine hemorrhagic fever (P < 0.05), but no difference was found between mild and severe cases of the disease (P > 0.05). The results of this study demonstrated a central role of IgG(1) in human recovery from infection with every strain of Junin virus, an observation stressed by the immune response to Candid #1 vaccine, which resulted in no difference in IgG subclasses composition from that found in mild cases of Argentine hemorrhagic fever.

Aislamiento del virus de la coriomeningitis linfocitaria de seres humanos / Isolation of lymphocytic choriomeningitis virus from human individuals

The activity of lymphocytic choriomeningitis virus (LCMv) in Argentina has been previously reported on the basis of serological evidence in rodents and humans and the isolation of only one strain of LCMv from a Mus domesticus captured in the province of Cordoba. The aim of this paper was to register patients with serological diagnosis of LCM, to isolate and to identify human strains of LCMv in Argentina. During the last 19 years, 15 cases were diagnosed as LCM by immunoflourescent indirect assay (IFI) and enzyme-linked immunosorbent assay (ELISA) but when neutralizing assay (NT) was incorporated, eight cases were classified as confirmed, three as probable and four as negative. The geographic distribution of the cases included three provinces: Cordoba, Buenos Aires and Santa Fe. Viral isolation was attempted in five patients classified as confirmed and only two resulted positive (P5226 and P8573). They were identified as LCMv by IFI and NT. The coexistence of LCMv with other arenaviruses, such as Junin and Oliveros viruses, in the same area, raises the probability of interactions between them, which could modify the virulence and/or pathogenicity for humans associated to genomic changes. Future studies of antigenic, genomic and virulence variability of different Argentine strains of LCMv, as well as the systematic search for human infection, will contribute to define the importance of this viral agent in our country and to implement control measures.

Aislamiento del virus de la coriomeningitis linfocitaria de seres humanos / Isolation of lymphocytic choriomeningitis virus from human individuals

The activity of lymphocytic choriomeningitis virus (LCMv) in Argentina has been previously reported on the basis of serological evidence in rodents and humans and the isolation of only one strain of LCMv from a Mus domesticus captured in the province of Cordoba. The aim of this paper was to register patients with serological diagnosis of LCM, to isolate and to identify human strains of LCMv in Argentina. During the last 19 years, 15 cases were diagnosed as LCM by immunoflourescent indirect assay (IFI) and enzyme-linked immunosorbent assay (ELISA) but when neutralizing assay (NT) was incorporated, eight cases were classified as confirmed, three as probable and four as negative. The geographic distribution of the cases included three provinces: Cordoba, Buenos Aires and Santa Fe. Viral isolation was attempted in five patients classified as confirmed and only two resulted positive (P5226 and P8573). They were identified as LCMv by IFI and NT. The coexistence of LCMv with other arenaviruses, such as Junin and Oliveros viruses, in the same area, raises the probability of interactions between them, which could modify the virulence and/or pathogenicity for humans associated to genomic changes. Future studies of antigenic, genomic and virulence variability of different Argentine strains of LCMv, as well as the systematic search for human infection, will contribute to define the importance of this viral agent in our country and to implement control measures. (Au)