The Role of the Humoral Immune Response in the Molecular Evolution of the Envelope C2, V3 and C3 Regions in Chronically HIV-2 Infected Patients

BACKGROUND: This study was designed to investigate, for the first time, the short-term molecular evolution of the HIV-2 C2, V3 and C3 envelope regions and its association with the immune response. Clonal sequences of the env C2V3C3 region were obtained from a cohort of eighteen HIV-2 chronically infected patients followed prospectively during 2-4 years. Genetic diversity, divergence, positive selection and glycosylation in the C2V3C3 region were analysed as a function of the number of CD4+ T cells and the anti-C2V3C3 IgG and IgA antibody reactivity RESULTS: The mean intra-host nucleotide diversity was 2.1% (SD, 1.1%), increasing along the course of infection in most patients. Diversity at the amino acid level was significantly lower for the V3 region and higher for the C2 region. The average divergence rate was 0.014 substitutions/site/year, which is similar to that reported in chronic HIV-1 infection. The number and position of positively selected sites was highly variable, except for codons 267 and 270 in C2 that were under strong and persistent positive selection in most patients. N-glycosylation sites located in C2 and V3 were conserved in all patients along the course of infection. Intra-host variation of C2V3C3-specific IgG response over time was inversely associated with the variation in nucleotide and amino acid diversity of the C2V3C3 region. Variation of the C2V3C3-specific IgA response was inversely associated with variation in the number of N-glycosylation sites. CONCLUSION: The evolutionary dynamics of HIV-2 envelope during chronic aviremic infection is similar to HIV-1 implying that the virus should be actively replicating in cellular compartments. Convergent evolution of N-glycosylation in C2 and V3, and the limited diversification of V3, indicates that there are important functional constraints to the potential diversity of the HIV-2 envelope. C2V3C3-specific IgG antibodies are effective at reducing viral population size limiting the number of virus escape mutants. The C3 region seems to be a target for IgA antibodies and increasing N-linked glycosylation may prevent HIV-2 envelope recognition by these antibodies. Our results provide new insights into the biology of HIV-2 and its relation with the human host and may have important implications for vaccine design.

Stress-Related Mucosal Disease: Incidence of Bleeding and the Role of Omeprazole in its Prophylaxis

BACKGROUND: Upper gastrointestinal bleeding is the severe complication of stress-related mucosal disease in hospitalized patients. In intensive care units (ICU), risk factors are well defined and only mechanical ventilation and coagulopathy proved to be relevant for significant bleeding. On the contrary, in non-ICU settings there is no consensus about this issue. Nevertheless, omeprazole is still widely used in prophylaxis of bleeding. The objective of our study was to evaluate the relevance of stress-related mucosal disease bleeding in patients admitted to an internal medicine ward, and the role of omeprazole in its prophylaxis. METHODS: We conducted a retrospective study in which we analysed consecutive patients who were admitted to our ward over a year. We recorded demographic characteristics of the patients, potential risk factors for stress-related mucosal disease (clinical data, laboratory, and medication), administration of prophylactic omeprazole, and total cost of this prophylaxis. Patients with active gastrointestinal bleeding on the admission were excluded. We recorded every upper gastrointestinal bleeding event with clinical relevance. RESULTS: Five hundred and thirty-five patients, mean age 70 years, mean length of stay 9.6+/-7.7 days; 140 (26.2%) patients were treated with 40 mg of omeprazole intravenously, 193 (36.1%) with 20mg of omeprazole orally, and 202 (37.8%) patients had no prophylaxis. There was only one episode (0.2%) of clinically relevant bleeding. CONCLUSION: In patients admitted to an internal medicine ward, incidence of upper gastrointestinal bleeding as a complication of stress-related mucosal disease is low. We found that there is no advantage in prophylaxis with omeprazole.