Human Immunodeficiency Virus type 1 in seronegative infants born to HIV-1-infected mothers.

BACKGROUND: Some individuals repeatedly exposed to Human Immunodeficiency Virus do not seroconvert and are resistant to HIV infection. Here, in a pediatric cohort of HIV seronegative infants born of HIV-infected mothers, we have studied eight non-breastfed children in whom viral DNA was detected in their PBMC. Our objective was to assess whether silent infection in these children can be explained by the presence of integrated viral DNA. METHODS: The presence of viral DNA was corroborated by nested PCR with primers for gag and the nef/LTR regions of HIV-1. Integration of HIV DNA into the host genome was assessed by an Alu-LTR PCR. Amplicons were sequenced and phylogenetic analyzes were done. RESULTS: HIV-1 DNA was detected in the earliest available PBMC sample from all eight infants, and two of them tested positive for HIV DNA at 2 years of age. Nested PCR resulted in the amplification of gag, nef/LTR and Alu-LTR fragments, which demostrated that HIV-1 DNA was integrated in the host cell genome. Each individual has a characteristic sequence pattern and is different from the LTR sequence of HXB2 prototype virus and other Mexican isolates. CONCLUSION: HIV-1 DNA was observed in PBMC from HIV exposed seronegative children in this pediatric cohort.

[A perinatal diagnostic problem: patients serologically negative but infected with HIV]. / Un problema de diagnóstico perinatal: pacientes serológicamente negativos pero infectados por el VIH.

Comprehensive HIV diagnosis of 142 patients was done by ELISA, IgG immunoblot, IgA immunoblot (in patients under 24 months), plasma antigen determination, viral isolation by culture and genome detection by polymerase chain reaction (PCR) amplification. Results showed that 14 patients (10%) with negative or indefinite results for anti-HIV-1 IgG antibody were in fact infected by the virus. Eleven of these patients were between 2 and 24 months of age, two between 4 and 6.5 years and one was 30 years old. Diagnosis was obtained by antigen positivity in four of them; by PCR amplification of peripheral mononuclear cells of proviral DNA in five of them; by PCR and immunofluorescence (IF) of cultured cells in four cases, and the last diagnosis was made by IgG immunoblot and IF of the viral culture. These cases pose a problem because of false negative HIV serology, particularly in patients under 24 months of age.

[11 years since the discovery of the human immunodeficiency virus]. / A 11 años del descubrimiento del virus de inmunodeficiencia humana.

The nucleotide sequence of the human immunodeficiency virus (HIV-1) gp120 variable region (V3) was obtained by sequencing the product of the polymerase chain reaction (PCR) amplification of seven HIV-1 Mexican isolates from patients who had been infected either sexually or through blood products. Mexican isolates showed a 61.4% homology between them and three viral subtypes were demonstrated. One of these corresponds to three sexually infected patients, another to two hemophiliac patients infected through blood products or transfusions and the third subtype to either sexually or blood infected patients. The latter shows a great similarity to the HTLV-IIIb/LAV prototype strain. Antigenic profiles of this region show at least three neutralization patterns for these isolates as well as one virus that does not have a high predictive value epitope in the V3 region. Our data show that Mexico has a high heterogeneity of HIV-1 circulating strains, similar to that reported in other regions of the world.

[Humoral immune response to HIV-2 in Mexico]. / Respuesta immune humoral hacia VIH-2 en México.

OBJECTIVE: To study the reactions of Mexican HIV-1 positive sera to HIV-2 antigens, and their relation to the mode of transmission and the clinical status of infected individuals. MATERIAL AND METHODS: Six-hundred and fifty-four sera samples collected in Mexico were tested using HIV-2 immunoblot (IB) techniques; 492 samples were from HIV-1 positive cases and 162 from HIV-1 negative controls. RESULTS: Seventy-nine percent (388/492) of the HIV-1 reactive sera showed reactivity with at least one HIV-2 protein: 71% (352/492) recognized the capsid protein p24, 24% (119/492) the transmembrane glycoprotein and 9% (44/492) the external glycoprotein of HIV-2. Considering the transmission mechanism, HIV-2 reactivity occurred in 81% (324/401) of the sexually infected patients, and only in 39% (16/41) of people infected through blood products. Ten highly reactive gp32 HIV-2 sera samples were titrated and results showed that reactivity with HIV-1 gp41 was always higher than that to HIV-2 gp32. HIV-1-HIV-2 dual infection was discarded by negative results with the commercial assay Liatek HIV 1+2. CONCLUSIONS: We propose that the serological cross-reactivity found can be due to a possible initial introduction in Mexico of two different viral strains through the two main transmission routes and that the strains circulating in sexually infected individuals are more similar to the HIV-2 strains, at least with respect to their glycoproteins, than the HIV-1 strains predominant in other countries.

[Riboprobes: an alternative in the detection of viral sequences]. / Las ribosondas: una alternativa en la detección de secuencias virales.

The use of riboprobes for the detection of RNA viral sequences is analyzed. Subgenomic fragments of cDNA from poliovirus type 2, dengue virus type 4 and human immunodeficiency virus type 1, were inserted downstream SP6 and/or T7 promoters in the transcription vectors pGEM-4z or pSP64. RNAs obtained by in vitro transcription in the presence of UTP infinity (32P) were used as probes for the detection of RNA viral sequences from infected cell lines in slot and Northern blot assays. The poliovirus riboprobe (P2-221) was able to detect specific viral sequences; thus, it could be used for the detection of the virus in serum, as well as in residual waters. The human immunodeficiency virus riboprobe (HIV-378), detected viral sequences poly A+RNA from infected cells; thus it can be used as a confirmatory test or as a tool in basic research. Finally, the dengue virus riboprobes (D4-2819 and D4-1134) detected specifically dengue 4 virus; however the sensitivity of the detection could be significantly improved amplifying viral sequences by the polymerase chain reaction (PCR) prior to probe hybridization.