Knowledge, attitudes and sexual practices of university students for advancing peer HIV education.

OBJECTIVE: To determine the current HIV/AIDS Knowledge, Attitudes and Sexual Practices (KASP) indicators amonguniversity students that would facilitate development and implementation of a peer education programme and the subsequent monitoring and evaluation of other HIV/AIDS activities. DESIGN: An institutional based cross-sectional study. SETTING: Maseno University, Kenya. SUBJECTS: Five hundred students composed of 60% males and 40% females as dictated by the university's male to female ratio. MAIN OUTCOME MEASURES: Levels of HIV and AIDS awareness, knowledge and attitudes and the current related behavioural trends and tendencies, among the students at the University. RESULTS: Of the five hundred respondents included in the study, 68.5% of them reported having ever had sexual intercourse, with males being the majority at 78.2%, while the females were 54.7%. A large majority (77%) of females were in current sexual relationships compared to 66.7% of males. A significant proportion (54.8%) of first year students reported having had their first sexual intercourse at the university. Sexual activity was seen to increase from 56.9 to 71.2% among the first year students when they got to second year of study at the university. Peer pressure emerged as an important factor in students' sexual behaviour (P=0.001). Of the students, 32% reported having undergone HIV tests, 70.8% were willing to go for a test while 74.3% perceived they had a chance of being infected with the virus based on their previous risky sexual experiences. A significant 77.7% of the respondents affirmed having ever used condoms but only 15.8% reported consistent use. CONCLUSION: High proportions of students are sexually active with peaks in first and second years of study. This is coupled with an equal inconsistent use of condoms. Peer influence emerged as an important feature in accelerating risky sexual behaviour hence the need for advancing peer education programmes in universities.

Metabolic diversity and antiviral activities of acyclic nucleoside phosphonates.

The acyclic nucleoside phosphonates (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC), (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA), and 9-(2-phosphonylmethoxyethyl)adenine (PMEA) inhibited herpes simplex virus-1 replication in Vero cells, and the IC50 values ranged from 4 microM (for HPMPC and HPMPA) to 40 microM (for PMEA). Pretreatment of cells with HPMPC for 12-24 hr induced an effective antiviral state, and the cells maintained this antiviral state for > 7 days. In contrast, much larger amounts (approximately 2.5-5 x IC50 doses) of PMEA or HPMPA were required to establish an antiviral state, which lasted for only approximately 24 or 72 hr, respectively. A 12-hr treatment of the cells with the phosphonates was required for the establishment of optimal antiviral activity; surprisingly, longer durations of exposure to PMEA (but not HPMPA or HPMPC) resulted in diminished antiviral effect. We investigated the metabolism of PMEA and HPMPC to determine the cellular basis for these differences. The cellular uptake of HPMPC was approximately 8-fold greater than that of PMEA. The levels of the PMEA metabolites PMEA monophosphate and PMEA diphosphate increased for approximately 12 hr and plateaued thereafter. PMEA and its metabolites were cleared from the cells with a half-life of 4.9 hr. In contrast, the HPMPC metabolites HPMPC monophosphate (HPMPCp) and HPMPC diphosphate (HPMPCpp) accumulated throughout the 24-hr study period and, at equimolar drug concentrations (25 microM), reached intracellular levels approximately 2-3-fold greater than those of the PMEA metabolites. HPMPC also differed from PMEA in its capacity to generate a phosphodiester metabolite (HMPCp-choline), which was a predominant metabolite in HPMPC-treated cells. In addition, the rates of disappearance of intracellular metabolites of the two drugs were significantly different. Thus, the decay of HPMPCpp was quite slow and biphasic (t1/2 = 24 and 65 hr) and that of HMPCp-choline was monophasic (t1/2 = 87 hr). Together, these factors can explain the differing antiviral potencies seen with PMEA and HPMPC. The possible role of the choline adduct in the expression of antiviral activity of the drug remains to be elucidated, but the adduct may serve as an intracellular store for the long term maintenance of active HPMPCpp in cells. The results also highlight the extent of diversity in the cellular pharmacology and antiviral activities of the acyclic nucleoside phosphonates.

Deoxyribonucleoside triphosphate pools of herpes simplex virus infected cells: the influence of selective antiherpes agents and the role of the deaminase pathway.

The effect of 5-methoxymethyl-2'-deoxycytidine (MMdCyd), in combination with tetrahydrodeoxyuridine (H4dUrd) and 5-methoxymethyl-2'-deoxyuridine (MMdUrd) on deoxyribonucleoside triphosphate pools was assessed. The dNTP pool content was almost 5 times as high in herpes simplex virus (HSV) infected VERO cells compared with mock-infected cells. Significant differences in dNTP pool sizes were observed with the different treatments. Treatment of HSV-infected cells with MMdCyd and MMdUrd resulted in a massive expansion of the dTTP pool, whereas pools of dCTP and dGTP were not affected substantially. MMdUrd and MMdCyd produced dATP pools that were 4 and 2.5 times that of the controls, respectively. Treatment with H4dUrd resulted in the dCTP pool increasing 12 times and barely detectable levels of dTTP. MMdCyd in combination with H4dUrd resulted in a marked reduction of the total deoxyribonucleoside triphosphate level. These results indicate that during viral replication the bulk of the thymidine nucleotides are derived from the dCyd/dCMP deaminase de novo pathway.

Regulatory effects of deoxyribonucleosides on the activity of 5-methoxymethyl-2'-deoxycytidine: modulation of antiherpes activity by deoxyguanosine and tetrahydrodeoxyuridine.

The effect of purine and pyrimidine deoxyribonucleosides on the activity of 5-methoxymethyl-2'-deoxycytidine (MMdCyd) against herpes simplex virus type 1 (HSV-1) was investigated. The antiviral activity of MMdCyd was decreased by deoxythymidine, deoxyuridine and deoxycytidine. Deoxyadenosine had no effect at concentrations up to 500 microM. In contrast, deoxyguanosine (dGuo) potentiated MMdCyd activity. The mean ED50 (1.5 microM) for the combination (MMdCyd plus 100 microM dGuo) was approximately 20-fold lower than that of MMdCyd (ED50 26 microM). When tetrahydrodeoxyuridine (H4dUrd, 540 microM) was added along with MMdCyd and dGuo, anti-HSV-1 activity of MMdCyd was further potentiated by 25-fold (ED50 0.06 microM). The inhibition of virus replication, as determined by the plaque reduction assay, was further confirmed by virus yield studies and by parallel observations on virus-induced cytopathogenicity. The order of decreasing effectiveness for reducing the production of infectious virus particles (virus yield) by different treatments was: MMdCyd + dGuo + H4dUrd greater than MMdCyd + DGuo greater than MMdCyd + H4dUrd greater than MMdCyd greater than dGuo + H4dUrd greater than dGuo greater than H4dUrd. The effect of dGuo and dGuo in combination with H4dUrd on deoxyribonucleoside triphosphate (dNTP) pools was determined in Vero cells infected with multiplicity of infection of 5 PFU/cell. In the presence of 100 microM dGuo, there was approximately a 3-fold, 2-fold and 12-fold increase in dCTP, dTTP and dGTP pool sizes respectively, as compared to control (untreated) cells. Treatment with H4dUrd (1.06 mM) in combination with dGuo (100 microM), resulted in an increase of the dCTP pool and a marked fall in the dTTP and dGTP pool. The possible mechanisms for potentiation of MMdCyd activity by dGuo and H4dUrd are discussed.

Antiherpes virus activity and effect on deoxyribonucleoside triphosphate pools of (E)-5-(2-bromovinyl)-2'-deoxycytidine in combination with deaminase inhibitors.

The antiviral activity and cytotoxicity of (E)-5-(2-bromovinyl)-2'-deoxycytidine (BrVdCyd) against herpes simplex virus type 1 (HSV-1), singly and in combination with deaminase inhibitors was determined using rabbit kidney (RK-13), HEP-2, BHK-21 and VERO cells. BrVdCyd was a potent inhibitor of HSV-1 replication with ED50 values of 0.30 to 1.20 microM depending on the cell line used. In the presence of tetrahydrouridine or tetrahydrodeoxyuridine (H4dUrd), potency of BrVdCyd increased approximately two fold (ED50: 0.54 microM) in HSV-infected VERO cells. The combination of BrVdCyd and H4dUrd was also effective in decreasing virus yield. Dihydrodeoxyuridine (H2dUrd) reversed the activity of BrVdCyd (ED50: 6 to 7 microM). The effect of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BrVdUrd), BrVdCyd and BrVdCyd in combination with H4dUrd on deoxyribonucleoside triphosphate (dNTP) pools was assessed in VERO cells infected with a high multiplicity of infection (10 PFU/cell). Significant differences in dNTP poll sizes (pmol/10(6) cell) were observed with different treatments. BrVdUrd and BrVdCyd treatment resulted in marked expansion of the dTTP pool (greater than 1200 pmol) compared to HSV-infected VERO cells (303 pmol). Exposure to H4dUrd resulted in a 12-fold expansion of the dCTP pool (326 pmol) and barely detectable levels of dTTP (less than 1.0 pmol). BrVdCyd plus H4dUrd treatment resulted in a slight expansion of the dTTP pool (515 pmol). These results indicate: (i) H4dUrd inhibits de novo dCyd/dCMP deaminase pathway and (ii) exposure to BrVdCyd plus H4dUrd puts a strain on viral DNA synthesis to such an extent that even though dTTP is being formed from alternative pathways, its eventual utilization as a substrate is reduced and hence it builds up.