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15th HIV Resistance Workshop: burden of infectious drug-resistant HIV may be falling

Deenan Pillay from University College London (UCL) reported on some good news from Brighton. In a collaborative effort between the MRC, UCL and Brighton Healthcare, the study provided an elegant confirmation of what we suspect but as yet had not been confirmed – that over time, the burden of drug-resistant infectious viral burden is falling in the infected population.

The premise for the study was to correlate viral load burden in potential transmitters and to determine how much resistance mutations in fact contribute to virus levels and its subsequent impact on infectivity. Total infectious viral load is the result of patients either un-treated or virologically failing on non-suppressive regimens. What is less well understood however, is how resistance mutations contribute to viral load and whether this precipitates infectivity with drug-resistant mutations.

The study was located in a fairly homogenous, well-defined and closely monitored group of MSM, all served by the same health care centre in Brighton since 1998. 1,482 patients both treated and naïve had a median of 9 viral loads and a total 495 resistance tests. The burden of resistance was calculated by mutations in the reverse transcriptase at positions 41, 103, 184 and 215 and in protease at position 90. The results from 2000 to 2003 demonstrate that 35% of this group had a VL >1,000 copies/ml. Nearly 7% had virus containing one or more key mutations. But this proportion fell by 20% during the period of study.

The predominant mutations in chronically infected or treated patients were in order of frequency: T215 (any) > M41L > K103N > M184V > L90M. Twenty-four individuals were also detected during this time with acute infection, most frequently harbouring: K103N > T215 (any) > M41L > L90M. But M184V was not detected. This correlates with previous reporting of M184V as a mutation that is not easily transmitted and unlikely to be detected in naïve patients. More interestingly, the impact of M184V on viral burden was found to be less than half of that observed with mutation T215.

The study confirms that the viral burden of infectious drug-resistant virus has indeed fallen over the past few years. With potent therapies and more patients on treatment, this trend can be expected to continue. The overall message is that patients are being treated more effectively and are therefore less infectious. This is due both to reduced viral loads and the overall reduction of drug-resistant infectious viral burden that can serve to facilitate resistance transmission.

Drowning and infectious disease symptoms are similar
July 05,2006

How long can you hold your breath under water?

Recent storms have left many plants standing in saturated soil in need of oxygen. Roots require air for survival, function and development of new roots. The abundant water forces air out of the soil, and roots can die from a lack of oxygen.

When soil temperatures are high, many plants are more quickly damaged in saturated soils. The problems result from low oxygen levels in the root zone, which prevent adequate water uptake to supply the foliage. Death of critical root and vascular system cells also occurs since these tissues require the greatest amount of oxygen. The ability of the root system to take up water and transport nutrients is impaired. The damage is not confined to low lying areas because standing water is not necessary, only saturation of the soil.

The most acute symptoms in large plants related to drowning include rapid wilting (flop), yellowing and death. These are the same symptoms expressed by the plant when stressed by drought and under fertilization.

The foliage of the plant shows the fact that it is not receiving the life sustaining products it needs. Foliage often flops when the sun appears and, in younger plants, symptoms may be temporary. However, equally damaging are the symptoms developing more slowly, such as stunting, yellowing and secondary infectious disease development.

Drowning events can form a complex of problems that lasts for a whole season. The above ground plant symptoms vary depending on which roots are damaged, how quickly the water evaporates and when the affected plants are observed. Furthermore, symptoms of drowning can coincide with several infectious diseases and the vascular wilt diseases.

Phytophthora, Fusarium wilt and Rhizoctonia often appear in sites where drowning has occurred. Serious stunting, root rot and canker formation are indications of plant disease problems. It is important to get a proper diagnosis if future plans include growing crops on the site. If plant death continues, plants should be checked for infectious diseases.

One of the most common problems that plagues homeowners is poor drainage in the landscape.

Very few plants tolerate standing water in their roots for extended periods of time. In poorly planned landscapes or in particularly rainy seasons, too much water often can cause plant death.

Check the root zone of your plants. Visible standing water or black roots are sure signs of problems. Poor drainage frequently is a very challenging problem to correct.

If planning a new landscape, consider the drainage at the earliest stages of development before any installation. For problems in an existing garden, you may be able temporarily to lift the plants and build raised beds by adding soil, then replanting.

For major drainage problems in existing yards, there may not be any easy solution, and a professional may be needed. French drains commonly are used in Kinston to help move water out of poorly drained areas.

Checking your drainage can help prevent your plants from having to “hold their breath.”