Syphilis lowers CD4 cell count and increases viral load in HIV-positive men (AIDSmap)

Syphilis lowers CD4 cell count and increases viral load in HIV-positive men

Syphilis lowers CD4 cell count and increases viral load in HIV-positive men

AIDSmap

Michael Carter, Monday, October 11, 2004

Syphilis infection in HIV-positive men is associated with an increase in
viral load and reduction in CD4 cell count, according to a US study published in
the October 21st edition of AIDS. The study investigators believe that their
findings indicate that HIV-positive men with syphilis are potentially more
infectious and call for integrated public health campaigns to prevent the spread of
both HIV and syphilis.

Although it is known that syphilitic ulcers can facilitate HIV transmission,
the effect of syphilis on HIV viral load and CD4 cell count has been little
studied. Other sexually transmitted infections have been linked to changes in
immune status, and investigators in San Francisco wished to see if infection
with syphilis had an impact on the viral load and CD4 cell counts of HIV-positive
men.

In common with many other cities in the US and Europe, there has been a
substantial increase in the number of cases of primary and secondary syphilis
diagnosed in gay men in San Francisco in recent years. Surveillance data for other
sexually transmitted infections and behavioural studies also suggest an
increase in risky sexual behaviour amongst gay men.

Using a retrospective review of public health records, investigators
identified a total of 52 cases of primary or secondary syphilis in HIV-positive men in
San Francisco between early 2001 and Spring 2003. The men had a median age of
36 years.

In total, 35 men (67%) had secondary syphilis, and 30 (58%) were taking HAART
at the time of their syphilis diagnosis. The overwhelming majority of men
received between one and three injections of benzathine penicillin to treat their
syphilis and this therapy was successful in all but two patients.

A total of 36 men had their HIV viral load measured before and during their
infection with syphilis. The investigators noted that during syphilis infection
viral load in these men increased significantly by a mean 0.21 log10 (p =
0.02). In men with secondary syphilis viral load increased by a mean of 0.33
log10, and amongst men not taking HAART the mean increase in viral load was 0.25
log10. Among the ten men who had secondary syphilis and were not taking HAART,
viral load was increased by a mean of 0.34 log10 during syphilis infection (p
= 0.05).

Of the 26 men who had a detectable viral load before infection with syphilis,
13 experienced an increase in their viral load during infection with
syphilis, and twelve of these men had an increase of 0.50 log10. However, of the ten
men taking HAART who had an undetectable viral load before syphilis was
diagnosed, only two men had a detectable viral load during infection with syphilis.

For 35 men, data were available on viral load during and after infection with
syphilis. Amongst these men, viral load did not decrease significantly after
syphilis was treated (mean fall in viral load 0.10 log10).

In further analysis, the investigators looked at viral load in men for whom
data were available on viral load before, during, and after syphilis. The mean
increase in viral load was 0.10 log10 during infection with syphilis, and
viral load fell by 0.3 log10 after syphilis was treated. Viral load increased by a
mean of 0.007 log10 after syphilis compared to the level of viral load before
syphilis infection. None of these changes in viral load was statistically
significant.

The investigators also looked at the effect of syphilis infection on CD4 cell
count. Amongst the 31 men who had before and during CD4 cell measurements
available, the investigators noted a mean drop in CD4 cell count of 62 cells/mm3
(p = 0.04). The decreases in CD4 cell count were most notable in men who had
secondary syphilis and were not taking HAART. Although CD4 cell count increased
by a mean of 33 cells/mm3 after syphilis was treated, this change was not
statistically significant (p = 0.23).

For 15 men data on CD4 cell count before, during and after syphilis infection
were available. No significant changes in CD4 cell count were seen in this
subset of individuals.

“Syphilis infection was associated with a significant increase in the plasma
viral load and a significant decrease in CD4 cell counts in HIV-infected men”,
write the investigators. The investigators note that these changes were most
notable in men with secondary infection, which could be the result of greater
immune activation.

The investigators admit that their study has several limitations, not least
that data on CD4 cell count and viral load before, during and after syphilis
infection were available for only 19 men. The investigators call for larger
confirmatory studies.

“Syphilis infection in HIV-infected men was associated with a significant
increase in viral load and a significant decrease in CD4 cell count…integrated
public health efforts to prevent new syphilis infections…to reduce the spread of
both diseases within affected communities”, conclude the investigators.

Reference

Buchacz K et al. Syphilis increases HIV viral load and decreases CD4 cell
counts in HIV-infected patients with new syphilis infections. AIDS 18: 2075-2079,
2004.